| 1. |
- Asplund, Maria. E., 1970, et al.
(author)
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Dynamics and fate of blue carbon in a mangrove-seagrass seascape : influence of landscape configuration and land-use change
- 2021
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In: Landscape Ecology. - : Springer. - 0921-2973 .- 1572-9761. ; 36, s. 1489-1509
-
Journal article (peer-reviewed)abstract
- Context Seagrass meadows act as efficient natural carbon sinks by sequestering atmospheric CO2 and through trapping of allochthonous organic material, thereby preserving organic carbon (C-org) in their sediments. Less understood is the influence of landscape configuration and transformation (land-use change) on carbon sequestration dynamics in coastal seascapes across the land-sea interface. Objectives We explored the influence of landscape configuration and degradation of adjacent mangroves on the dynamics and fate of C-org in seagrass habitats. Methods Through predictive modelling, we assessed sedimentary C-org content, stocks and source composition in multiple seascapes (km-wide buffer zones) dominated by different seagrass communities in northwest Madagascar. The study area encompassed seagrass meadows adjacent to intact and deforested mangroves. Results The sedimentary C-org content was influenced by a combination of landscape metrics and inherent habitat plant- and sediment-properties. We found a strong land-to-sea gradient, likely driven by hydrodynamic forces, generating distinct patterns in sedimentary C-org levels in seagrass seascapes. There was higher C-org content and a mangrove signal in seagrass surface sediments closer to the deforested mangrove area, possibly due to an escalated export of C-org from deforested mangrove soils. Seascapes comprising large continuous seagrass meadows had higher sedimentary C-org levels in comparison to more diverse and patchy seascapes. Conclusion Our results emphasize the benefit to consider the influence of seascape configuration and connectivity to accurately assess C-org content in coastal habitats. Understanding spatial patterns of variability and what is driving the observed patterns is useful for identifying carbon sink hotspots and develop management prioritizations.
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| 2. |
- Asplund, Maria. E., 1970, et al.
(author)
-
Methane Emissions From Nordic Seagrass Meadow Sediments
- 2022
-
In: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 8
-
Journal article (peer-reviewed)abstract
- Shallow coastal soft bottoms are important carbon sinks. Submerged vegetation has been shown to sequester carbon, increase sedimentary organic carbon (C-org) and thus suppress greenhouse gas (GHG) emissions. The ongoing regression of seagrass cover in many areas of the world can therefore lead to accelerated emission of GHGs. In Nordic waters, seagrass meadows have a high capacity for carbon storage, with some areas being recognized as blue carbon hotspots. To what extent these carbon stocks lead to emission of methane (CH4) is not yet known. We investigated benthic CH4 emission (i.e., net release from the sediment) in relation to seagrass (i.e. Zostera marina) cover and sedimentary C-org content (%) during the warm summer period (when emissions are likely to be highest). Methane exchange was measured in situ with benthic chambers at nine sites distributed in three regions along a salinity gradient from similar to 6 in the Baltic Sea (Finland) to similar to 20 in Kattegat (Denmark) and similar to 26 in Skagerrak (Sweden). The net release of CH4 from seagrass sediments and adjacent unvegetated areas was generally low compared to other coastal habitats in the region (such as mussel banks and wetlands) and to other seagrass areas worldwide. The lowest net release was found in Finland. We found a positive relationship between CH4 net release and sedimentary C-org content in both seagrass meadows and unvegetated areas, whereas no clear relationship between seagrass cover and CH4 net release was observed. Overall, the data suggest that Nordic Zostera marina meadows release average levels of CH4 ranging from 0.3 to 3.0 mu g CH4 m(-2) h(-1), which is at least 12-78 times lower (CO2 equivalents) than their carbon accumulation rates previously estimated from seagrass meadows in the region, thereby not hampering their role as carbon sinks. Thus, the relatively weak CH4 emissions from Nordic Z. marina meadows will not outweigh their importance as carbon sinks under present environmental conditions.
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| 3. |
- Dahl, Martin, 1984-, et al.
(author)
-
A 2,000-Year Record of Eelgrass (Zostera marina L.) : Colonization Shows Substantial Gains in Blue Carbon Storage and Nutrient Retention
- 2024
-
In: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 38:3
-
Journal article (peer-reviewed)abstract
- Assessing historical environmental conditions linked to habitat colonization is important for understanding long-term resilience and improving conservation and restoration efforts. Such information is lacking for the seagrass Zostera marina, an important foundation species across cold-temperate coastal areas of the Northern Hemisphere. Here, we reconstructed environmental conditions during the last 14,000 years from sediment cores in two eelgrass (Z. marina) meadows along the Swedish west coast, with the main aims to identify the time frame of seagrass colonization and describe subsequent biogeochemical changes following establishment. Based on vegetation proxies (lipid biomarkers), eelgrass colonization occurred about 2,000 years ago after geomorphological changes that resulted in a shallow, sheltered environment favoring seagrass growth. Seagrass establishment led to up to 20- and 24-fold increases in sedimentary carbon and nitrogen accumulation rates, respectively. This demonstrates the capacity of seagrasses as efficient ecosystem engineers and their role in global change mitigation and adaptation through CO2 removal, and nutrient and sediment retention. By combining regional climate projections and landscape models, we assessed potential climate change effects on seagrass growth, productivity and distribution until 2100. These predictions showed that seagrass meadows are mostly at risk from increased sedimentation and hydrodynamic changes, while the impact from sea level rise alone might be of less importance in the studied area. This study showcases the positive feedback between seagrass colonization and environmental conditions, which holds promise for successful conservation and restoration efforts aimed at supporting climate change mitigation and adaptation, and the provision of several other crucial ecosystem services. © 2024. The Authors.
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| 4. |
- Dahl, Martin, et al.
(author)
-
A temporal record of microplastic pollution in Mediterranean seagrass soils
- 2021
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In: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 273
-
Journal article (peer-reviewed)abstract
- Plastic pollution is emerging as a potential threat to the marine environment. In the current study, we selected seagrass meadows, known to efficiently trap organic and inorganic particles, to investigate the concentrations and dynamics of microplastics in their soil. We assessed microplastic contamination and accumulation in 210Pb dated soil cores collected in Posidonia oceanica meadows at three locations along the Spanish Mediterranean coast, with two sites located in the Almería region (Agua Amarga and Roquetas) and one at Cabrera Island (Santa Maria). Almería is known for its intense agricultural industry with 30 000 ha of plastic-covered greenhouses, while the Cabrera Island is situated far from urban areas. Microplastics were extracted using enzymatic digestion and density separation. The particles were characterized by visual identification and with Fourier-transformed infrared (FTIR) spectroscopy, and related to soil age-depth chronologies. Our findings showed that the microplastic contamination and accumulation was negligible until the mid-1970s, after which plastic particles increased dramatically, with the highest concentrations of microplastic particles (MPP) found in the recent (since 2012) surface soil of Agua Amarga (3819 MPP kg-1), followed by the top-most layers of the soil of the meadows in Roquetas (2173 kg-1) and Santa Maria (68-362 kg-1). The highest accumulation rate was seen in the Roquetas site (8832 MPP m-2 yr-1). The increase in microplastics in the seagrass soil was associated to land-use change following the intensification of the agricultural industry in the area, with a clear relationship between the development of the greenhouse industry in Almería and the concentration of microplastics in the historical soil record. This study shows a direct linkage between intense anthropogenic activity, an extensive use of plastics and high plastic contamination in coastal marine ecosystems such as seagrass meadows. We highlight the need of proper waste management to protect the coastal environment from continuous pollution.
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| 5. |
- Dahl, Martin, et al.
(author)
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Effects of seagrass overgrazing on sediment erosion and carbon sink capacity : Current understanding and future priorities
- 2021
-
In: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 6:6, s. 309-319
-
Journal article (peer-reviewed)abstract
- We searched the literature for experimental and observational studies assessing the effects of seagrass overgrazing on erosion of sediment and sedimentary organic carbon (SOC) and found that most studies reported a significant impact, likely caused by a cascading effect (i.e., seagrass shoot loss -> belowground biomass degradation -> sediment destabilization or SOC erosion). However, there appears to be a clear lack of knowledge on the extent and mechanisms behind SOC erosion in seagrass meadows and we highlight the need for research to (1) define spatial and temporal scales of occurrence; (2) assess the influence of belowground biomass degradation, sediment characteristics, and hydrodynamic exposure on sediment stabilization; and (3) estimate the greenhouse gas emission after a disturbance. Such information would help coastal resource managers to address the causes and effects of SOC loss and sediment erosion when evaluating impacts of global change on coastal ecosystems.
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| 6. |
- Dahl, Martin, 1984-, et al.
(author)
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First assessment of seagrass carbon accumulation rates in Sweden: A field study from a fjord system at the Skagerrak coast
- 2023
-
In: PLoS Climate. - : Public Library of Science (PLoS). - 2767-3200. ; 2:1
-
Journal article (peer-reviewed)abstract
- Seagrass meadows are globally important blue carbon sinks. In northern cold-temperate regions, eelgrass (Zostera marina) is the dominant seagrass species, and although their sedimentary carbon stocks have been quantified across regions, information regarding the CO2 withdrawal capacity as carbon sinks remains scarce. Here we assessed the carbon (Corg) accumulation rates (CARs) and stocks as well as the organic matter sources in five seagrass meadows in the Gullmar Fjord area on the Swedish Skagerrak coast. We found that the mean (±SD) CAR was 14 ± 3 g Corg m-2 yr-1 over the last ~120–140 years (corresponding to a yearly uptake of 52.4 ± 12.6 g CO2 m-2). The carbon sink capacity is in line with other Z. marina areas but relatively low compared to other seagrass species and regions globally. About half of the sedimentary carbon accumulation (7.1 ± 3.3 g Corg m-2 yr-1) originated from macroalgae biomass, which highlights the importance of non-seagrass derived material for the carbon sink function of seagrass meadows in the area. The Corg stocks were similar among sites when comparing at a standardized depth of 50 cm (4.6–5.9 kg Corg m-2), but showed large variation when assessed for the total extent of the cores (ranging from 0.7 to 20.6 kg Corg m-2 for sediment depths of 11 to at least 149 cm). The low sediment accretion rates (1.18–1.86 mm yr-1) and the relatively thick sediment deposits (with a maximum of >150 cm of sediment depth) suggests that the carbon stocks have likely been accumulated for an extended period of time, and that the documented loss of seagrass meadows in the Swedish Skagerrak region and associated erosion of the sediment could potentially have offset centuries of carbon sequestration.
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| 7. |
- Dahl, Martin, et al.
(author)
-
High Seasonal Variability in Sediment Carbon Stocks of Cold-Temperate Seagrass Meadows
- 2020
-
In: Journal of Geophysical Research: Biogeosciences. - 2169-8953 .- 2169-8961. ; 125:1
-
Journal article (peer-reviewed)abstract
- ©2020. American Geophysical Union. All Rights Reserved. Seagrass meadows have a high ability to capture and store atmospheric CO2 in the plant biomass and underlying sediment and thereby function as efficient carbon sinks. The seagrass Zostera marina is a common species in the temperate Northern Hemisphere, a region with strong seasonal variations in climate. How seasonality affects carbon storage capacity in seagrass meadows is largely unknown, and therefore, in this study, we aimed to assess variations in sedimentary total organic carbon (TOC) content over a 1-year cycle in seagrass meadows on the Swedish west coast. The TOC was measured in two Z. marina sites, one wave exposed and one sheltered, and at two depths (1.5 and 4 m) within each site, every second month from August 2015 to June 2016. We found a strong seasonal variation in carbon density, with a peak in early summer (June), and that the TOC was negatively correlated to the net community production of the meadows, presumably related to organic matter degradation. There was seasonal variation in TOC content at all sediment sections, indicating that the carbon content down to 30 cm is unstable on a seasonal scale and therefore likely not a long-term carbon sink. The yearly mean carbon stocks were substantially higher in the sheltered meadow (3,965 and 3,465 g m−2) compared to the exposed one (2,712 and 1,054 g m−2) with similar seasonal variation. Due to the large intra-annual variability in TOC content, seasonal variation should be considered in carbon stock assessments and management for cold-temperate seagrass meadows.
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| 8. |
- Dahl, Martin, 1984-, et al.
(author)
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Impacts of land-use change and urban development on carbon sequestration in tropical seagrass meadow sediments
- 2022
-
In: Marine Environmental Research. - : Elsevier BV. - 0141-1136 .- 1879-0291. ; 176
-
Journal article (peer-reviewed)abstract
- Seagrass meadows store significant carbon stocks at a global scale, but land-use change and other anthropogenic activities can alter the natural process of organic carbon (Corg) accumulation. Here, we assessed the carbon accumulation history of two seagrass meadows in Zanzibar (Tanzania) that have experienced different degrees of disturbance. The meadow at Stone Town has been highly exposed to urban development during the 20th century, while the Mbweni meadow is located in an area with relatively low impacts but historical clearing of adjacent mangroves. The results showed that the two sites had similar sedimentary Corg accumulation rates (22–25 g m−2 yr−1) since the 1940s, while during the last two decades (∼1998 until 2018) they exhibited 24–30% higher accumulation of Corg, which was linked to shifts in Corg sources. The increase in the δ13C isotopic signature of sedimentary Corg (towards a higher seagrass contribution) at the Stone Town site since 1998 points to improved seagrass meadow conditions and Corg accumulation capacity of the meadow after the relocation of a major sewage outlet in the mid–1990s. In contrast, the decrease in the δ13C signatures of sedimentary Corg in the Mbweni meadow since the early 2010s was likely linked to increased Corg run-off of mangrove/terrestrial material following mangrove deforestation. This study exemplifies two different pathways by which land-based human activities can alter the carbon storage capacity of seagrass meadows (i.e. sewage waste management and mangrove deforestation) and showcases opportunities for management of vegetated coastal Corg sinks.
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| 9. |
- Dahl, Martin, et al.
(author)
-
The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast
- 2020
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
-
Journal article (peer-reviewed)abstract
- Cold-temperate seagrass (Zostera marina) meadows provide several important ecosystem services, including trapping and storage of sedimentary organic carbon and nutrients. However, seagrass meadows are rapidly decreasing worldwide and there is a pressing need for protective management of the meadows and the organic matter sinks they create. Their carbon and nutrient storage potential must be properly evaluated, both at present situation and under future climate change impacts. In this study, we assessed the effect of wave exposure on sedimentary carbon and nitrogen accumulation using existing data from 53 Z. marina meadows at the Swedish west coast. We found that meadows with higher hydrodynamic exposure had larger absolute organic carbon and nitrogen stocks (at 0-25 cm depth). This can be explained by a hydrodynamically induced sediment compaction in more exposed sites, resulting in increased sediment density and higher accumulation (per unit volume) of sedimentary organic carbon and nitrogen. With higher sediment density, the erosion threshold is assumed to increase, and as climate change-induced storms are predicted to be more common, we suggest that wave exposed meadows can be more resilient toward storms and might therefore be even more important as carbon- and nutrient sinks in the future.
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| 10. |
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| 11. |
- Ismail, Rashid O., 1986-, et al.
(author)
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Effects of calcification on air-water CO2 fluxes in tropical seagrass meadows : A mesocosm experiment
- 2023
-
In: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 561
-
Journal article (peer-reviewed)abstract
- Seagrass meadows deliver a range of ecosystem services, where one of the more important is the capacity to store carbon and serve as sinks for atmospheric carbon dioxide. The capacity of seagrass meadows for carbon storage might, however, be modified and complicated by several factors; one important factor is the possible effects of calcification within the meadows. In tropical areas, seagrass meadows can contain high proportions of calcareous organisms, which through their calcification may cause release of CO2. To study this aspect of the CO2 balance within tropical seagrass systems, we investigated the air-water CO2 flux in seagrass mesocosms with different plant community compositions, i.e. mixtures of seagrass and calcifying macroalgae, having similar overall photosynthetic oxygen evolution rates. The measured CO2 fluxes changed both in rate and direction over the day and were significantly related to plant community composition. Downward fluxes of CO2 were found only over vegetation with high proportion of seagrass and in the afternoon, whereas occurrence of calcifying algae appeared to reverse the flow. A partial least squares (PLS) regression model indicated that pH, pCO2 and dissolved inorganic carbon (DIC) were the primary environmental variables predicting the CO2 fluxes. Our findings show that algal calcification might partly counteract the carbon sequestration in seagrass meadows.
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| 12. |
- Krause-Jensen, D, et al.
(author)
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Nordic Blue Carbon Ecosystems: Status and Outlook
- 2022
-
In: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
-
Research review (peer-reviewed)abstract
- Vegetated coastal and marine habitats in the Nordic region include salt marshes, eelgrass meadows and, in particular, brown macroalgae (kelp forests and rockweed beds). Such habitats contribute to storage of organic carbon (Blue Carbon – BC) and support coastal protection, biodiversity and water quality. Protection and restoration of these habitats therefore have the potential to deliver climate change mitigation and co-benefits. Here we present the existing knowledge on Nordic BC habitats in terms of habitat area, C-stocks and sequestration rates, co-benefits, policies and management status to inspire a coherent Nordic BC roadmap. The area extent of BC habitats in the region is incompletely assessed, but available information sums up to 1,440 km2 salt marshes, 1,861 (potentially 2,735) km2 seagrass meadows, and 16,532 km2 (potentially 130,735 km2, including coarse Greenland estimates) brown macroalgae, yielding a total of 19,833 (potentially 134,910) km2. Saltmarshes and seagrass meadows have experienced major declines over the past century, while macroalgal trends are more diverse. Based on limited salt marsh data, sediment C-stocks average 3,311 g Corg m-2 (top 40-100 cm) and sequestration rates average 142 g Corg m-2 yr-1. Eelgrass C-stocks average 2,414 g Corg m-2 (top 25 cm) and initial data for sequestration rates range 5-33 g Corg m-2, quantified for one Greenland site and one short term restoration. For Nordic brown macroalgae, peer-reviewed estimates of sediment C-stock and sequestration are lacking. Overall, the review reveals substantial Nordic BC-stocks, but highlights that evidence is still insufficient to provide a robust estimate of all Nordic BC-stocks and sequestration rates. Needed are better quantification of habitat area, C-stocks and fluxes, particularly for macroalgae, as well as identification of target areas for BC management. The review also points to directives and regulations protecting Nordic marine vegetation, and local restoration initiatives with potential to increase C-sequestration but underlines that increased coordination at national and Nordic scales and across sectors is needed. We propose a Nordic BC roadmap for science and management to maximize the potential of BC habitats to mitigate climate change and support coastal protection, biodiversity and additional ecosystem functions.
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| 13. |
- Moberg, Christina, et al.
(author)
-
De unga gör helt rätt när de stämmer staten : 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
- 2022
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In: Aftonbladet. - : Aftonbladet. ; :2022-12-07
-
Journal article (pop. science, debate, etc.)abstract
- Vi, 1 620 forskare samt lärare vid universitet och högskolor, är eniga med de unga bakom Auroramålet: De drabbas och riskerar att drabbas allvarligt av klimatkrisen under sin livstid. De klimatåtgärder vi vidtar i närtid avgör deras framtid. Sverige måste ta ansvar och göra sin rättvisa andel av det globala klimatarbetet. I strid med Parisavtalet ökar utsläppen av växthusgaser i en takt som gör att 1,5-gradersmålet kan överskridas om några år. De globala effekterna blir allt mer synliga med ständiga temperaturrekord, smältande isar, havshöjning och extremväder som torka, förödande bränder och skyfall med enorma översvämningar, som i Pakistan nyligen. Försörjningen av befolkningen utsätts för allvarliga hot i många länder.Minskningen av den biologiska mångfalden är extrem. Klimatkrisen är enligt WHO det största hotet mot människors hälsa i hela världen och barn utgör en särskilt sårbar grupp. Med Sveriges nordliga läge sker uppvärmningen här dubbelt så fort som det globala genomsnittet. Det förskjuter utbredningsområden för växtlighet och sjukdomsbärande insekter och ökar förekomsten av extremväder såsom värmeböljor, skogsbränder och översvämningar samt av många olika sorters infektioner och allergier. När extremväder ökar, ökar även stressen och risken för mental ohälsa. Värmeböljor ökar risken för sjukdom och död hos sårbara grupper som äldre, små barn och personer med kroniska sjukdomar. De negativa effekterna på hälsan kommer att öka i takt med klimatkrisen och barn riskerar att drabbas av ackumulerade negativa hälsoeffekter under hela sina liv. Redan i dag är mer än hälften av unga mellan 12 och 18 år i Sverige ganska eller mycket oroliga för klimat och miljö. Detta är förståeligt när våra beslutsfattare inte gör vad som krävs.Den juridiska och moraliska grunden för arbetet mot klimatförändringarna är att varje land måste göra sin rättvisa andel av det globala klimatarbetet. Centralt i det internationella klimatramverket är att rika länder med höga historiska utsläpp, däribland Sverige, måste gå före resten av världen. Dessa länder måste också bidra till att finansiera klimatomställningen i länderna i det Globala Syd, som är minst ansvariga för klimatkrisen men drabbas hårdast. Denna rättviseprincip är tydlig i Parisavtalet och var en het diskussionsfråga under COP27 i Sharm el-Sheikh, men lyser med sin frånvaro i det svenska klimatarbetet. Sverige har satt mål för att minska sina utsläpp. Men de är helt otillräckliga: minskningstakten är för låg och målen tillåter samtidigt att åtgärder skjuts på framtiden. Dessutom exkluderas merparten av Sveriges utsläpp från de svenska nationella utsläppsmålen; bland annat utelämnas utsläpp som svensk konsumtion orsakar utanför Sveriges gränser, utsläpp från utrikes transporter och utsläpp från markanvändning och skogsbruk, exempelvis utsläpp från förbränning av biobränslen eller utsläpp från dikade våtmarker (Prop. 2016/17:146 s.25-28).Sverige saknar dessutom ett eget mål för att öka upptaget av växthusgaser genom utökat skydd och restaurering av ekosystem, något som krävs för att begränsa de värsta konsekvenserna av klimatkrisen (IPCC s.32). Trots dessa låga ambitioner misslyckas Sverige med att nå sina utsläppsmål, konstaterar både Klimatpolitiska rådet och Naturvårdsverket. En klimatpolitik i linje med Parisavtalet kräver både att alla typer av växthusgasutsläpp minskar samtidigt som – inte i stället för – upptaget av växthusgaser maximeras: i dag misslyckas Sverige på bägge fronter.Slutsatsen är tydlig. Sverige vidtar inte de åtgärder som krävs för att skydda barns och ungdomars rättigheter enligt Europakonventionen till skydd för de mänskliga rättigheterna. Detta medför allvarliga risker för liv och hälsa för unga generationer, människor i andra länder och särskilt utsatta grupper. Detta kan inte fortsätta. Därför ställer vi oss bakom Auroras krav att Sverige börjar göra sin rättvisa andel och omedelbart sätter igång ett omfattande och långtgående klimatarbete som vilar på vetenskaplig grund och sätter rättvisa i centrum.
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| 14. |
- Silas, Mathew O., et al.
(author)
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Seascape configuration influences big blue octopus (Octopus cyanea) catches: Implications for a sustainable fishery
- 2023
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In: FISHERIES RESEARCH. - : Elsevier. - 0165-7836 .- 1872-6763. ; 264
-
Journal article (peer-reviewed)abstract
- Seascape configuration is known to influence fish distribution and abundance in coastal waters. However, there is little information regarding how the shape of the coastal seascape influences catches of landed fisheries species, particularly so in the understudied western Indian Ocean (WIO). With focus on big blue octopus (Octopus cyanea), which is a widely found cephalopod species in the WIO, we compared landed catches (biomass, catch rate, and density) in submerged and exposed reefs, and explored the influence of proximity to fishing villages and reef habitat size on octopus landings. We used fishery-dependent data collected between 2018 and 2020 from eight landing sites spread across the Tanzanian coast. We found a strong relationship between biomass of octopus catch and distance from fished reefs to fishing villages, with higher fished biomass on reefs farther away. Octopus densities were higher, while catch rates were lower, on reefs very close to (within one km distance from) fishing villages compared to more distant reefs. In general, submerged reefs provided higher catches than exposed reefs. The low octopus catches on the exposed reefs were attributed to high fishing pressure, while submerged reefs that are only accessible through diving provide optimal areas for octopuses to grow. Octopus catches were, however, not significantly affected by reef size. The findings suggest that management policies should propor-tionate fishing efforts to ensure sustainable exploitation of reefs and associated fishery resources.
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| 15. |
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| 16. |
- Björk, Mats, 1960-, et al.
(author)
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The amount of light reaching the leaves in seagrass (Zostera marina) meadows.
- 2021
-
In: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 16:9
-
Journal article (peer-reviewed)abstract
- Seagrass meadows, and other submerged vegetated habitats, support a wide range of essential ecological services, but the true extents of these services are in many ways still not quantified. One important tool needed to assess and model many of these services is accurate estimations of the systems´ primary productivity. Such productivity estimations require an understanding of the underwater light field, especially regarding the amount of light that actually reaches the plants' photosynthetic tissue. In this study, we tested a simple practical approach to estimate leaf light exposure, relative to incoming light at the canopy, by attaching light sensitive film at different positions on leaves of Zostera marina, eelgrass, in four seagrass meadows composed of different shoot density and at two different depths. We found that the light reaching the leaves decreased linearly down through the canopy. While the upper parts of the leaves received approximately the same level of light (photosynthetic photon flux density, PPFD) as recorded with a PAR meter at the canopy top, the average light that the seagrass leaves were exposed to varied between 40 and 60% of the light on top of the canopy, with an overall average of 48%. We recommend that actual light interception is measured when assessing or modelling light depending processes in submerged vegetation, but if this is not achievable a rough estimation for vegetation similar to Z. marina would be to use a correction factor of 0.5 to compensate for the reduced light due to leaf orientation and internal shading.
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| 17. |
- Charisiadou, S., et al.
(author)
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Coastal aquaculture in Zanzibar, Tanzania
- 2022
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In: Aquaculture. - : Elsevier. - 0044-8486 .- 1873-5622. ; 546
-
Journal article (peer-reviewed)abstract
- This study provides an overview of the multi-sectoral coastal aquaculture development in Zanzibar (Tanzania) over the last thirty years based on empirical evidence from interviews, field observations, policy reports and literature reviews. Despite the immense potential of aquaculture for food and livelihoods, only seaweed farming has so far established into commercial-scale production. This activity is dominated by women and became widespread in the early 1990s as a small but regular source of income. However, seaweed farming constraints such as frequent seaweed die-offs, as well as economic and institutional constraints inhibit its development. Other types of aquaculture activities such as fish farming, mud crab fattening, half-pearl farming, sea cucumber farming and sponge and coral cultures are under development with limited production or in experimental stages. Common constraints among these activities are economic limitations, lack of technical infrastructure and skills, small and irregular production, and limited trade and market availabilities. At the same time, there is a lack of sufficient management and monitoring systems, while there are no formal regulations or clear strategies to boost aquaculture at the national level. In addition, new aquaculture initiatives are often dominated by donor-driven projects instead of local entrepreneurships. This situation does not encourage engagement in aquaculture and thus such activities are outcompeted by other already established sectors (e.g. agriculture and fisheries). We conclude that aquaculture has great potential to evolve due to high environmental capacity. Nevertheless, achieving profitable production and a stronger commitment within local communities, as well as developing effective mariculture governance through support mechanisms and clear strategies to boost the sector at the national level, are essential for sustainable mariculture development in Zanzibar.
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| 18. |
- Eggertsen, Linda, 1981-, et al.
(author)
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Where the grass is greenest in seagrass seascapes depends on life history and simple species traits of fish
- 2022
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In: Estuarine, Coastal and Shelf Science. - : Academic Press. - 0272-7714 .- 1096-0015. ; 266
-
Journal article (peer-reviewed)abstract
- Tropical seagrass meadows are critical habitats for many fish species, yet few studies have investigated the influence of multiple scale-dependent factors and marine protected areas on seagrass fish species of differing life histories. We assessed the influence of fine-scale seagrass meadow characteristics and seascape-scale variables on the abundance of fish in a seagrass-dominated seascape in the Bazaruto Archipelago, Mozambique, particularly examining patterns of nursery- vs. resident species as well as mobile- vs. sedentary species. We found that fish distribution patterns in this seagrass-dominated seascape were dependent on species’ life history characteristics; nursery taxa showed lower abundance in seagrass meadows further from adult reef habitats, while resident species within seagrass meadows occurred in higher abundances far from reefs. For taxa utilizing both mangroves and seagrass meadows as nursery habitat, proximity to mangroves was an important factor. Fish abundances were generally influenced by variables at the seascape scale (km), while sedentary species were predominantly influenced by area variables, and smaller seascapes (<500 m in radius) better explained distribution patterns. The influence of marine protected areas was taxon-specific, with the strongest effects of protection on resident species. Our results indicate that protection efforts in seagrass-dominated seascapes can have varying impacts on fish distribution, depending on the life history of the species present, and the geographical placement of the reserve within the seascape. Further, we suggest that simple species attributes can be utilised to describe generalized abundance patterns of fish in seagrass seascapes.
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| 19. |
- Elma, Eylem, et al.
(author)
-
Post-bleaching alterations in coral reef communities
- 2023
-
In: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 186
-
Journal article (peer-reviewed)abstract
- We explored the extent of post-bleaching impacts, caused by the 2014-2016 El Niño Southern Oscillation (ENSO) event, on benthic community structure (BCS) and herbivores (fish and sea urchins) on seven fringing reefs, with differing protection levels, in Zanzibar, Tanzania. Results showed post-bleaching alterations in BCS, with up to 68 % coral mortality and up to 48 % increase in turf algae cover in all reef sites. Herbivorous fish biomass increased after bleaching and was correlated with turf algae increase in some reefs, while the opposite was found for sea urchin densities, with significant declines and complete absence. The severity of the impact varied across individual reefs, with larger impact on the protected reefs, compared to the unprotected reefs. Our study provides a highly relevant reference point to guide future research and contributes to our understanding of post-bleaching impacts, trends, and evaluation of coral reef health and resilience in the region.
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| 20. |
- George, Rushingisha, et al.
(author)
-
Methane emission and sulfide levels increase in tropical seagrass sediments during temperature stress: A mesocosm experiment
- 2020
-
In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 10:4, s. 1917-1928
-
Journal article (peer-reviewed)abstract
- Climate change-induced ocean warming is expected to greatly affect carbon dynamics and sequestration in vegetated shallow waters, especially in the upper subtidal where water temperatures may fluctuate considerably and can reach high levels at low tides. This might alter the greenhouse gas balance and significantly reduce the carbon sink potential of tropical seagrass meadows. In order to assess such consequences, we simulated temperature stress during low tide exposures by subjecting seagrass plants (Thalassia hemprichii) and associated sediments to elevated midday temperature spikes (31, 35, 37, 40, and 45°C) for seven consecutive days in an outdoor mesocosm setup. During the experiment, methane release from the sediment surface was estimated using gas chromatography. Sulfide concentration in the sediment pore water was determined spectrophotometrically, and the plant's photosynthetic capacity as electron transport rate (ETR), and maximum quantum yield (Fv/Fm) was assessed using pulse amplitude modulated (PAM) fluorometry. The highest temperature treatments (40 and 45°C) had a clear positive effect on methane emission and the level of sulfide in the sediment and, at the same time, clear negative effects on the photosynthetic performance of seagrass plants. The effects observed by temperature stress were immediate (within hours) and seen in all response variables, including ETR, Fv/Fm, methane emission, and sulfide levels. In addition, both the methane emission and the size of the sulfide pool were already negatively correlated with changes in the photosynthetic rate (ETR) during the first day, and with time, the correlations became stronger. These findings show that increased temperature will reduce primary productivity and increase methane and sulfide levels. Future increases in the frequency and severity of extreme temperature events could hence reduce the climate mitigation capacity of tropical seagrass meadows by reducing CO2 sequestration, increase damage from sulfide toxicity, and induce the release of larger amounts of methane. © 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
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| 21. |
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| 22. |
- Ismail, Rashid O., 1986-
(author)
-
Drivers of carbon sink function in tropical seagrass beds : influence of carbon import, plant composition, seascape configuration and human activities
- 2021
-
Doctoral thesis (other academic/artistic)abstract
- Seagrass meadows are effective carbon sinks, sequestering atmospheric CO2 and capturing allochthonous organic material, storing organic carbon (Corg) in their sediments, so called Blue Carbon. In tropical areas, seagrass meadows have a high number of calcareous organisms, which can offset carbon sequestration by releasing CO2 through their calcification. Human activities such as urbanization and land-use change with inadequate management of blue carbon ecosystems are causing fast degradation of tropical blue carbon ecosystems, particularly mangroves and seagrasses. In this thesis, I and colleagues looked at the carbon sequestration process and the impact of marine protected areas (MPAs) on Corg conservation in the blue carbon ecosystems of the western Indian Ocean (WIO) region. This was accomplished by examining the air-water CO2 flux in different plant community compositions (i.e. seagrass and calcifying macroalgae), as well as factors driving air-water CO2 flux and the assessment of Corg stocks within and outside MPAs in tropical and subtropical areas of the WIO. The impact of landscape configuration and modification due to urbanization and mangrove degradation on the accumulation and variability of Corg in seagrass habitats was also investigated. We found that, the sum of the fluxes showed a net efflux of CO2 over the meadows. The CO2 fluxes changed both in rate and direction over the day, and were significantly related to plant community composition and environmental conditions such as pH and CO2 partial pressure, where pH had the strongest influence on CO2 fluxes. Influxes were found only over vegetation with high proportion of seagrass and in the afternoon, whereas calcifying algae appeared to reverse the flow. We found that highly productive seagrass meadows can generate a net CO2 from the water to the atmosphere as plants’ demand for CO2 to a large extent is covered by internal cycling of CO2, both from degradation of autochthonous and allochthonous material and calcification. We found that accumulation of Corg in seagrass meadows is larger than the flow to the atmosphere, indicating that these systems can still be carbon sinks.The inflow of allochthonous carbon, Corg content and stocks in the seagrass meadows was influenced by a combination of landscape metrics and inherent habitat plant- and sediment-properties. We discovered a strong land to sea gradient in terms of Corg content in seagrass seascapes, due to hydrodynamic forces that resulted into unique patterns in sedimentary Corg levels. Seagrass surface sediments closer to a deforested mangrove had higher Corg content and mangrove signal, probably due to increased Corg export from deforested mangrove. In comparison to more diversified and patchy seascapes, seascapes with extensive continuous seagrass meadows have higher sedimentary Corg content. Seagrass meadows located near an area with rapid and short-term urbanization and degraded mangroves had a higher sedimentary Corg content, but similar carbon accumulation rate as an area with long-term progressive urbanization. It was found that tropical and subtropical blue carbon ecosystems store a significant amount of carbon in their sediments, but that many carbon storage hotspots are entirely/partially outside MPAs. This masks their influence on blue carbon conservation. MPAs can still be used to conserve blue carbon if carbon hotspots are properly located and managed.This thesis contributes knowledge of important determining factors influencing primary pathways of tropical coastal ecosystem carbon sequestration and are critical for identifying hotspots of carbon storage to generate conservation prioritizations. Future research should focus on conservation prioritizations that will limit the unsustainable use of coastal resources.
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| 23. |
- Kalokora, O. J., et al.
(author)
-
An experimental assessment of algal calcification as a potential source of atmospheric CO2
- 2020
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:4
-
Journal article (peer-reviewed)abstract
- Marine vegetated ecosystems such as seagrass meadows are increasingly acknowledged as important carbon sinks based on their ability to capture and store atmospheric carbon dioxide, thereby contributing to climate change mitigation. Most studies on carbon storage in marine ecosystems have focused on organic carbon, leaving inorganic carbon processes such as calcification unaccounted for, despite of their critical role in the global carbon budget. This is probably because of uncertainties regarding the role of calcification in marine carbon budgets as either atmospheric CO2 source or sink. Here, we conducted a laboratory experiment to investigate the influence of a calcifying alga (Corallina officinalis L.) on seawater carbon content, using a non-calcifying alga (Ulva lactuca L.) as a control. In a first part, algae were incubated separately while measuring changes in seawater pH, total alkalinity (TA) and total dissolved inorganic carbon (DIC). The amount of carbon used in photosynthetic uptake and production of CaCO3 was then calculated. In a second, directly following, part the algae were removed and DIC levels were allowed to equilibrate with air until the pH stabilized and the loss of CO2 to air was calculated as the difference in total DIC from the start of part one, to the end of the second part. The results showed that C. officinalis caused a significant and persistent reduction in total dissolved inorganic carbon (DIC), TA and seawater pH, while no such permanent changes were caused by U. lactuca. These findings indicate that calcification can release a significant amount of CO2 to the atmosphere and thereby possibly counteract the carbon sequestration in marine vegetated ecosystems if this CO2 is not re-fixed in the system. Our research emphasises the importance of considering algal calcification in future assessments on carbon storage in coastal areas. © 2020 Kalokora et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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| 24. |
- Kalokora, Olivia J, et al.
(author)
-
Seagrass meadows mixed with calcareous algae have higher plant productivity and sedimentary blue carbon storage
- 2022
-
In: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 12:2
-
Journal article (peer-reviewed)abstract
- Seagrass meadows capture and store large amounts of carbon in the sediment beneath, thereby serving as efficient sinks of atmospheric CO2. Carbon sequestration levels may however differ greatly among meadows depending on, among other factors, the plant community composition. Tropical seagrass meadows are often intermixed with macroalgae, many of which are calcareous, which may compete with seagrass for nutrients, light, and space. While the photosynthetic CO2 uptake by both seagrasses and calcareous algae may increase the overall calcification in the system (by increasing the calcium carbonate saturation state, Ω), the calcification process of calcareous algae may lead to a release of CO2, thereby affecting both productivity and calcification, and eventually also the meadows' carbon storage. This study estimated how plant productivity, CaCO3 production, and sediment carbon levels were affected by plant community composition (seagrass and calcareous algae) in a tropical seagrass-dominated embayment (Zanzibar, Tanzania). Overall, the patterns of variability in productivity differed between the plant types, with net areal biomass productivity being highest in meadows containing both seagrass and calcareous algae. Low and moderate densities of calcareous algae enhanced seagrass biomass growth, while the presence of seagrass reduced the productivity of calcareous algae but increased their CaCO3 content. Sedimentary carbon levels were highest when seagrasses were mixed with low or moderate cover of calcareous algae. The findings show that plant community composition can be an important driver for ecosystem productivity and blue carbon sequestration.
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| 25. |
- Martin, Michael, et al.
(author)
-
Estimating the Potential of Building Integration and Regional Synergies to Improve the Environmental Performance of Urban Vertical Farming
- 2022
-
In: Frontiers in Sustainable Food Systems. - : Frontiers Media SA. - 2571-581X. ; 6
-
Journal article (peer-reviewed)abstract
- Vertical farms have expanded rapidly in urban areas to support food system resilience. However, many of these systems source a substantial share of their material and energy requirements outside their urban environments. As urban areas produce significant shares of residual material and energy streams, there is considerable potential to explore the utilization of these streams for urban agriculture in addition to the possibility of employing underutilized urban spaces in residential and commercial buildings. This study aims to explore and assess the potential for developing more circular vertical farming systems which integrate with buildings and utilize residual material and energy streams. We focus on the symbiotic development of a hypothetical urban farm located in the basement of a residential building in Stockholm. Life cycle assessment is used to quantify the environmental performance of synergies related to energy integration and circular material use. Energy-related scenarios include the integration of the farm's waste heat with the host building's heating system and the utilization of solar PV. Circular material synergies include growing media and fertilizers based on residual materials from a local brewery and biogas plant. Finally, a local pick-up system is studied to reduce transportation. The results point to large benefits from integrating the urban farm with the building energy system, reducing the vertical farm's GHG emissions up to 40%. Synergies with the brewery also result in GHG emissions reductions of roughly 20%. No significant change in the environmental impacts was found from the use of solar energy, while the local pick-up system reduces environmental impacts from logistics, although this does not substantially lower the overall environmental impacts. However, there are some trade-offs where scenarios with added infrastructure can also increase material and water resource depletion. The results from the synergies reviewed suggest that proximity and host-building synergies can improve the material and energy efficiency of urban vertical farms. The results provide insights to residential building owners on the benefits of employing residual space for urban food provisioning and knowledge to expand the use of vertical farming and circular economy principles in an urban context.
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| 26. |
- Mgeleka, Said S. S., et al.
(author)
-
Population genetics of the hound needlefish Tylosurus crocodilus (Belonidae) indicate high connectivity in Tanzanian coastal waters
- 2023
-
In: Marine Biology Research. - : Taylor & Francis. - 1745-1000 .- 1745-1019. ; 19:4-5, s. 261-270
-
Journal article (peer-reviewed)abstract
- The hound needlefish Tylosurus crocodilus (Belonidae) is a highly demanded fish in the local markets of Tanzania, but the growing coastal population threatens its sustainability. As belonids are highly migratory fishes utilising various parts of the seascape, increased fishing pressure may disrupt connectivity patterns on different spatiotemporal scales and disaggregate populations. Using the COI gene, this study assessed the genetic population structure, connectivity patterns, and historical demography of T. crocodilus collected in seven sites spread along Tanzanian coastal waters. Results showed fourteen haplotypes with low overall nucleotide and haplotype diversity. Pairwise F-ST comparisons revealed no significant differences among the sampled sites, except for the northernmost site (Tanga) and an island in the south (Songosongo). Analysis of molecular variance (AMOVA) revealed a non-significant genetic structure among populations (F-ST = 0.01782), suggesting the fishery across Tanzanian waters exploits the same population. Moreover, there was no correlative relationship between genetic and pairwise geographic distances, rejecting the isolation by distance hypothesis. However, neutrality tests and mismatch distribution analysis revealed that recent demographic expansion might exist. Empirical evidence of panmixia suggests high genetic connectivity. In combination with low genetic diversity, management should be directed to actions that prevent genetic diversity loss and the effect of genetic drift on populations.
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| 27. |
- Ngisiange, Noah, et al.
(author)
-
Seasonal fish larvae abundance and composition in seagrass habitats of coastal East Africa
- 2024
-
In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 14:1, s. 11203-
-
Journal article (peer-reviewed)abstract
- Seagrass habitats play a major role in fisheries productivity through nursery functions and feeding grounds for diverse fish species. However, little is known about the seasonal distribution of fish larvae at large spatial scales in coastal East Africa. We investigated drivers of the seasonal fish larvae abundance and composition in seagrass habitats in Kenya and Tanzania. We found a high diversity of fish larvae (54 families) inhabiting seagrass habitats that differed between sites and seasons. Fish larvae abundance were highest in Kenya, particularly during the northeast monsoon season. Overall, total larval abundances per site were low, reaching less than 190 individuals/100 m3 in Kenya and less than 40 individuals/100 m3 in Tanzania, likely related to the low productivity and strong hydrodynamic processes in this region. Our data suggests that most of the fish spawn year-round in these tropical waters as we did not find strong seasonal patterns. All sites had a high relative abundance of larvae from demersal spawning fishes, indicating that many fish species move to coastal sites for spawning. Primary productivity and dissolved oxygen, driven by hydrodynamics conditions are positively related to fish larvae productivity both in Kenya and Tanzania. These findings indicate that the occurrence of both resident and transient fish larvae in seagrass meadows is driven by strong hydrodynamic and tidal processes that transport fish larvae across adjacent habitats.
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| 28. |
- Nyangoko, Baraka, 1989-, et al.
(author)
-
Community perceptions of climate change and ecosystem-based adaptation in the mangrove ecosystem of the Rufiji Delta, Tanzania
- 2022
-
In: Climate and Development. - : Informa UK Limited. - 1756-5529 .- 1756-5537. ; 14:10, s. 896-908
-
Journal article (peer-reviewed)abstract
- Mangroves are increasingly recognized for their role in supporting adaptation to climate change and variability. However, knowledge about how climate change and variability affect mangrove ecosystem services (MES) and their role in supporting coastal communities to adaption is limited in Tanzania. We used participatory rural appraisal methods and field observations to explore local communities' perceptions of climate change and variability, and ecosystem-based adaptation (EbA) strategies in the mangroves of the Rufiji Delta, Tanzania. Decrease in rainfall, increased temperatures, coastal flooding, and the incidence of sea level rise were identified as key variables associated with a changing climate in the delta. Perceived climatic stresses included damaged fish breeding sites, altered climate regulation and a decrease in coastal protection and flood control. Decline in crop, fish and honey production were perceived as the main impacts on community livelihoods, although there were significant differences across occupational groups. Dependence on MES in times of shocks, such as when agriculture production fails, switching of occupation, crop diversification, fishing in deep waters and migration to other areas provided potential adaptation options. Although the reported perceptions related to climate change or variability are not explicit, they both have negative consequences to mangrove dependent communities' livelihoods.
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| 29. |
- Nyangoko, Baraka, 1989-, et al.
(author)
-
Community perceptions of mangrove ecosystem services and their determinants in the Rufiji Delta, Tanzania
- 2021
-
In: Sustainability. - Basel : MDPI. - 2071-1050. ; 13:1, s. 1-23
-
Journal article (peer-reviewed)abstract
- Understanding how local communities perceive and depend on mangrove ecosystem services (MES) is important for translating and incorporating their benefits, priorities, and preferences into conservation and decision-making processes. We used focus group discussions, key informant interviews, household questionnaires, and direct observations to explore how local communities in the Rufiji Delta perceive a multitude of MES and factors influencing their perceptions. Sixteen MES were identified by the respondents. Provisioning services were the most highly identified services, accounting for 67% of the overall responses, followed by regulating (53%), cultural (45%), and supporting (45%) services. Poles for building, firewood for cooking, coastal protection, and habitats for fisheries were perceived as the most important MES to sustain local livelihoods, although the perceptions differed between sites. Distance from household homes to mangroves and residence time were significant predictors of the local communities’ awareness of all identified MES. Gender of household heads and performance of local management committees also determined the local communities’ awareness of provisioning, regulating, and cultural services. We conclude that perceptions of MES are context-specific and influenced by multiple factors. We believe a deeper understanding of local stakeholders’ preferences for MES can help strengthen the link between local communities and conservation actors and can provide a basis for sustainable management of mangrove forests.
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| 30. |
- Nyangoko, Baraka, 1989-, et al.
(author)
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Local perceptions of changes in mangrove ecosystem services and their implications for livelihoods and management in the Rufiji Delta, Tanzania
- 2022
-
In: Ocean and Coastal Management. - : Elsevier. - 0964-5691 .- 1873-524X. ; 219
-
Journal article (peer-reviewed)abstract
- Understanding the status and trends of ecosystem services (ES) in a changing environment is important for identifying effective management measures of multifunctional mangrove ecosystems. Mangroves and their ES are jeopardized by a complex set of factors, with impacts that are experienced at local levels, especially in developing countries, where people often rely directly on natural capital for their livelihoods and well-being. This study was set to explore how local communities in the Rufiji Delta, situated in central coastal Tanzania, perceived the status and trends in mangrove ecosystem services (MES), associated drivers of change and the impacts of changes in MES on local livelihoods. A mixed methodological framework (including focus group discussions, key informant interviews, household surveys and direct observations) was used. People from villages close to mangroves rated the status of MES higher than those in villages distant from mangroves. Provisioning services (P) were often perceived to be in a worse and more declining state than regulating (R), cultural (C) and supporting services (S). A decrease in availability of poles and firewood (P), decline of fish habitats (S) and an increase in education value (C) were the most commonly perceived changes of MES in the study area. Illegal harvesting of mangrove poles, rice cultivation, climate change and inadequate management were seen as the most critical drivers of mangrove degradation, although the perceptions differed between sites. Rice farming was perceived to be a primary cause of mangrove loss by communities far from mangrove forests, while illegal exploitation was identified as the major driver by communities near mangroves. Fishing, collection of poles and honey were perceived as the most impacted livelihoodsdepending on MES. This together with the comparatively low status and declining trend of these MES indicate that they should be of high management priority as indicated by the first order management index used in this study.
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| 31. |
- Nyangoko, Baraka, 1989-
(author)
-
Managing Mangrove Ecosystem Services for Local Livelihoods and Adaptations in Tanzania
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- Recognizing the importance of ecosystem services (ES) for peoples' livelihoods and well-being is important for decision-making processes on conservation. Mangrove ecosystems in Tanzania are protected by law, but they continue to be exposed to degradation and loss, and there is still limited information about the awareness, preferences, status and trends of the ES they provide. This thesis aims to explore the link between mangrove ecosystem services (MES) and community livelihoods, changes in MES and associated drivers of change, adaptation options and their management in Tanzania, using the Rufiji Delta and Pangani Estuary as case studies. A mixed framework of methods including focus group discussions, key informant interviews, household surveys, direct observations, and literature reviews was used to gather data. Provisioning services were the most commonly identified MES, and they were more often reported to be deteriorating than regulating, cultural, and supporting services. Proximity to mangrove forest and residence time were positively associated with communities' awareness of all identified MES. Poles for building, firewood for cooking, coastal protection, and fisheries habitats were perceived as the most important MES for sustaining local livelihoods, though perceptions varied between sites. Reliance on mangrove resources was significantly predicted by household residence time, household main occupation, household size, and the cost of alternative resources to substitute mangrove wood as a source of domestic fuel. Illegal harvesting of mangrove poles, rice cultivation, climate change and inadequate governance and conservation measures were identified as the most critical drivers of mangrove degradation, but differed significantly from place to place. Fishing was perceived as the most impacted livelihood occupation compared to the other groups of occupations. Potential ways to adapt to environmental changes in the study areas included reliance on MES for ecosystem-based adaptation (EbA), switching of occupation, diversifying crops, offshore fishing, and migrating to other areas. This thesis argues that the linkage between MES and human well-being is site-specific, and drivers impacting on mangroves and their associated services vary spatially and is greatly accelerated by anthropogenic disturbances. Raising more awareness about the multifunctionality of mangroves and committing to participatory forest management that involves local people, as well as reforming the current forest policy by incorporating clear legal mechanisms for engaging communities around mangrove management and diversifying livelihood options are re-emphasized as appropriate ways to improve mangrove conservation. Furthermore, investment by providing adequate funding for conservation in long run rather than relying on short-term international donor-funded projects are recommended to government institutions as a basis for sustainable management of mangrove forests in Tanzania.
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| 32. |
- Nyangoko, Baraka, et al.
(author)
-
Socio-economic Determinants of Mangrove Exploitation and Management in the Pangani River Estuary, Tanzania
- 2022
-
In: Ecology & Society. - : Resilience Alliance. - 1708-3087. ; 27:2
-
Journal article (peer-reviewed)abstract
- Mangrove forests in Tanzania are gazetted as state forest reserves, implying that exploitation is controlled by the state. However, their continued degradation and loss is largely associated to the inadequate enforcement of management measures against uncontrolled extractive exploitation to support local livelihoods. Local management institutions are therefore advocated to enhance mangrove conservation. This study explored socioeconomic determinants of exploitation patterns and management of mangroves in the Pangani River Estuary, using two coastal communities (Bweni and Pangani Magharibi) as case study sites. Data were collected through focus group discussions, key informant interviews, household questionnaires, and field observations. Quantitative data were analyzed for both descriptive and statistical inferences, while qualitative information was subjected to content analysis. Residence time of household, household main occupation, household size, and cost of alternatives to mangroves as a source of domestic fuel were all factors positively associated with mangrove resource use. The two communities differed in their perceptions on the role of local institutions in management of mangroves. Over half of respondents (56%) in Bweni agreed that interventions by Beach Management Units (BMUs) enhanced mangrove conditions, whereas only about 16% of the respondents in Pangani Magharibi had similar perceptions. Overall, 55% of the respondents were not impressed with the performance of government institutions in implementing conservation measures for sustainable use of mangroves. Exploration and promotion of feasible alternative livelihood activities and improved stakeholders’ collaborative arrangements are recommended for sustainable exploitation and management of mangroves in the study area.
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| 33. |
- Perry, Diana, et al.
(author)
-
Physiological responses of Atlantic cod to climate change indicate that coastal ecotypes may be better adapted to tolerate ocean stressors
- 2024
-
In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 14:1
-
Journal article (peer-reviewed)abstract
- Healthy ecosystems and species have some degree of resilience to changing conditions, however as the frequency and severity of environmental changes increase, resilience may be diminished or lost. In Sweden, one example of a species with reduced resilience is the Atlantic cod (Gadus morhua). This species has been subjected to overfishing, and with additional pressures such as habitat degradation and changing environmental conditions there has been little to no recovery, despite more than a decade of management actions. Given the historical ecological, economical, and cultural significance of cod, it is important to understand how Atlantic cod respond to global climate change to recover and sustainably manage this species in the future. A multi-stressor experiment was conducted to evaluate physiological responses of juvenile cod exposed to warming, ocean acidification, and freshening, changes expected to occur in their nursery habitat. The response to single drivers showed variable effects related to fish biometrics and increased levels of oxidative stress dependent parameters. Importantly, two separate responses were seen within a single treatment for the multi-stressor and freshening groups. These within-treatment differences were correlated to genotype, with the offshore ecotype having a heightened stress response compared to the coastal ecotype, which may be better adapted to tolerate future changes. These results demonstrate that, while Atlantic cod have some tolerance for future changes, ecotypes respond differently, and cumulative effects of multiple stressors may lead to deleterious effects for this important species.
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| 34. |
- Perry, Diana, et al.
(author)
-
Spatial risk assessment of global change impacts on Swedish seagrass ecosystems
- 2020
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:1
-
Journal article (peer-reviewed)abstract
- Improved knowledge on the risk in ecologically important habitats on a regional scale from multiple stressors is critical for managing functioning and resilient ecosystems. This risk assessment aimed to identify seagrass ecosystems in southern Sweden that will be exposed to a high degree of change from multiple global change stressors in mid- and endof- century climate change conditions. Risk scores were calculated from the expected overlap of three stressors: sea surface temperature increases, ocean acidification and wind driven turbid conditions. Three high-risk regions were identified as areas likely to be exposed to a particularly high level of pressure from the global stressors by the end of the century. In these areas it can be expected that there will be a large degree of stressor change from the current conditions. Given the ecological importance of seagrass meadows for maintaining high biodiversity and a range of other ecosystem services, these risk zones should be given high priority for incorporation into management strategies, which can attempt to reduce controllable stressors in order to mitigate the consequences of some of the impending pressures and manage for maintained ecosystem resilience.
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| 35. |
- Pittman, S. J., et al.
(author)
-
Seascape ecology : identifying research priorities for an emerging ocean sustainability science
- 2021
-
In: Marine Ecology Progress Series. - : INTER-RESEARCH. - 0171-8630 .- 1616-1599. ; 663, s. 1-29
-
Journal article (peer-reviewed)abstract
- Seascape ecology, the marine-centric counterpart to landscape ecology, is rapidly emerging as an interdisciplinary and spatially explicit ecological science with relevance to marine management, bio-diversity conservation, and restoration. While important progress in this field has been made in the past decade, there has been no coherent prioritisation of key research questions to help set the future research agenda for seascape ecology. We used a 2-stage modified Delphi method to solicit applied research questions from academic experts in seascape ecology and then asked respondents to identify priority questions across 9 interrelated research themes using 2 rounds of selection. We also invited senior management/conservation practitioners to prioritise the same research questions. Analyses highlighted congruence and discrepancies in perceived priorities for applied research. Themes related to both ecological concepts and management practice, and those identified as priorities include seascape change, seascape connectivity, spatial and temporal scale, ecosystem-based management, and emerging technologies and metrics. Highest-priority questions (upper tercile) received 50% agreement between respondent groups, and lowest priorities (lower tercile) received 58% agreement. Across all 3 priority tiers, 36 of the 55 questions were within a +/- 10% band of agreement. We present the most important applied research questions as determined by the proportion of votes received. For each theme, we provide a synthesis of the research challenges and the potential role of seascape ecology. These priority questions and themes serve as a roadmap for advancing applied seascape ecology during, and beyond, the UN Decade of Ocean Science for Sustainable Development (2021-2030).
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| 36. |
- Rasmusson, Lina M., et al.
(author)
-
Effects of temperature and hypoxia on respiration, photorespiration, and photosynthesis of seagrass leaves from contrasting temperature regimes
- 2020
-
In: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 77:6
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Journal article (peer-reviewed)abstract
- In near-future climate change scenarios, elevated ocean temperatures with higher and more frequent peaks are anticipated than at present. Moreover, increased eutrophication and higher primary and secondary productivity will affect the oxygen levels of shallow-water coastal ecosystems, creating hypoxic conditions that can be experienced regularly, especially in dense vegetated systems. These climate-related events may impose detrimental effects on the primary productivity of seagrass. To evaluate such effects, this study combined gas exchange measurements with pulse amplitude-modulated fluorometry to assess the impact of short-time exposure to a range of water temperatures at ambient and low-oxygen levels on mitochondrial respiration, chlorophyll fluorescence (based on the Fv/F0 ratio), photosynthetic oxygen evolution, and photorespiration in leaf segments of the temperate seagrass Zostera marina and the tropical seagrass Thalassia hemprichii. We found that mitochondrial respiration in both Z. marina and T. hemprichii increased with higher temperatures up to 40°C and that low O2 caused significantly reduced respiration rates, particularly in T. hemprichii. Elevated water temperature had a clear negative effect on the Fv/F0 of both seagrass species, indicating damage or inactivation of the photosynthetic apparatus, even when light is not present. Moreover, damage to the photosynthetic apparatus was observed as an effect of elevated temperature combined with low O2 during darkness, resulting in subsequent lower photosynthesis in light. Photorespiration was present, but not promoted by increased temperature alone and will thus not further contribute to productivity losses during warmer events (when not carbon limited). This study demonstrates the negative impact of hypoxic stress and elevated temperatures on seagrass productivity, which may influence the overall health of seagrass plants as well as oxygen and carbon fluxes of shallow-water coastal ecosystems in warmer climate scenarios.
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| 37. |
- Rasmusson, Lina M., et al.
(author)
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Sensitivity of photosynthesis to warming in two similar species of the aquatic angiosperm ruppia from tropical and temperate habitats
- 2021
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In: Sustainability. - : MDPI AG. - 2071-1050. ; 13:16
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Journal article (peer-reviewed)abstract
- Climate change-related events, such as marine heatwaves, are increasing seawater temperatures, thereby putting pressure on marine biota. The cosmopolitan distribution and significant contribution to marine primary production by the genus Ruppia makes them interesting organisms to study thermal tolerance and local adaptation. In this study, we investigated the photosynthetic responses in Ruppia to the predicted future warming in two contrasting bioregions, temperate Sweden and tropical Thailand. Through DNA barcoding, specimens were determined to Ruppia cirrhosa for Sweden and Ruppia maritima for Thailand. Photosynthetic responses were assessed using pulse amplitude-modulated fluorometry, firstly in short time incubations at 18, 23, 28, and 33◦ C in the Swedish set-up and 28, 33, 38, and 43◦ C in the Thai set-up. Subsequent experiments were conducted to compare the short time effects to longer, five-day incubations in 28◦ C for Swedish plants and 40◦ C for Thai plants. Swedish R. cirrhosa displayed minor response, while Thai R. maritima was more sensitive to both direct and prolonged temperature stress with a drastic decrease in the photosynthetic parameters leading to mortality. The results indicate that in predicted warming scenarios, Swedish R. cirrhosa may sustain an efficient photosynthesis and potentially outcompete more heat-sensitive species. However, populations of the similar R. maritima in tropical environments may suffer a decline as their productivity will be highly reduced.
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| 38. |
- Silas, Mathew Ogalo, et al.
(author)
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Adaptive capacity and coping strategies of small-scale coastal fisheries to declining fish catches: Insights from Tanzanian communities
- 2020
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In: Environmental Science and Policy. - : Elsevier BV. - 1462-9011 .- 1873-6416. ; 108, s. 67-76
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Journal article (peer-reviewed)abstract
- Small-scale fishing communities are expected to adapt to fish catch fluctuations linked to global environmental change. Notwithstanding, impacts from severe climate events and overexploitation of fisheries resources can compromise functions and resilience of ecosystems and associated species, and thereby jeopardize long-term population trend stability and fisheries productivity. To date, most assessments and vulnerability studies of fisheries-dependent populaces have focused on global, regional and national levels, while studies at village and community levels, where adaptive planning in the context of climate- and environmental changes is important, are less common. Based on data from official fishery records over a three-decadal period (1984–2016) and recent interviews with artisanal fishermen (319 fishers from eight communities) along the Tanzanian coast, we assessed small-scale fisheries with regard to (i) long-term trends in fishery landings, (ii) long-term alterations in fishing gear use, and (iii) fishers’ perceptions on how they have been coping and adapting to fluctuating fish landings. We further investigated (iv) the adaptive capacity of a wide range of coastal villages by assessing the fishers’ responses to an anticipated future scenario of a major (50 %) decline in landings from the current fisheries catch levels. The long-term trend records of fish landings showed a remarkable ∼50 % reduction in terms of both catch per vessel and catch per fisher from 1984 to 2016. According to the interviews, the majority of fishers (75 %) have changed fishing grounds from nearshore to offshore areas during the last decade, owing to a general perception that nearshore areas have suffered major reduction in fish stocks (due to overfishing and environmental changes related to extreme climate- or weather events), while offshore areas were considered still productive. The change in location of fishing grounds is probably a result of the clear switch in major gear type utilization from beach seine to ring net that occurred over the last decades. With a further progressive decline in fishery catches to a predictive level of 50 % of the current catch level, there is a general perception that artisanal fishers will continue fishing because alternative livelihoods (like crop farming, which employs more than 65 % of the population) have suffered similar negative impact. These findings highlight the need for building adaptive capacity in local coastal communities to develop alternative coping strategies for the impacts of climate- and environmental changes. © 2020 Elsevier Ltd
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| 39. |
- Silas, Mathew Ogalo, 1982-
(author)
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Patterns of small-scale coastal fisheries and local fisheries management in Tanzania : adaptation to a changing climate
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Coastal habitats like mangroves, seagrass meadows, coral reefs, and adjacent offshore waters constitute an important part of the tropical coastal seascape. They provide conducive environmental conditions for fish and other marine animals, which serve as food and income for coastal communities around the world. Despite the beneficial ecosystem services generated, these habitats are under immense pressure from anthropogenic and climate change impacts that destroy habitats and reduce their capacity to support fisheries. This leaves coastal communities in a challenging situation, where people need to adapt to changing fish stocks. This thesis aimed to understand the past, current, and future patterns of small-scale fisheries in Tanzania and how fishing communities can respond to human activities and climate change. The thesis assesses and integrates fish catch data (from 2013 and 2014) and fishers’ perceptions. Archived fish landing data from 1950 to 2016 were used to understand the role of coastal marine ecosystems for small-scale fisheries and to investigate how local fishers adapt to environmental changes and fishing pressure. To address the goals of the thesis, Paper I investigated seasonal (gear-based) patterns of fish catch in coastal marine habitats. Paper II explored the influence of environmental conditions and monsoon seasons on fish catch. Papers III and IV examined the effects of climate change on small-scale fisheries, and Paper IV also addressed the response of fishing villages to a declining catch trend in the country. The findings show that the coastal seascape (from nearshore to offshore waters) is vital in sustaining fish stocks, while the productivity of coastal habitats varies with seasons. The highest catch rates were observed in the offshore environment during the northeast monsoon season (Paper I), which is characterised by weak winds and high sea surface temperature. In contrast, the catches of important target species, such as tuna and prawn, were found high in nearshore habitats during the rougher southeast monsoon season (Paper II), which is characterised by strong winds and low sea surface temperature. The fishers’ perceptions revealed similar patterns of high catches of tuna and prawn during the southeast monsoon season in nearshore waters (Paper II). This emphasises the relevance of incorporating fishers’ perceptions into research to better understand the complex dynamics of small-scale fisheries. A comparative assessment of climate change impacts on long-term fisheries productivity of two target stocks showed clear species-specific effects of climate change. For instance, pelagic mackerel (Rastrelliger kanagurta) was found sensitive to increased precipitation, as a lowered salinity may negatively affect the maturing phase (Paper III). Demersal prawn, on the other hand, was positively related to increased sea surface temperature (Paper III). Importantly, the findings of Paper IV show that most small-scale fishers will continue to fish despite declining catches. This suggests a need of building adaptive capacity among local coastal communities, which could serve as alternative coping mechanisms to the impacts of climate change and other stressors (Paper IV).In conclusion, this thesis shows how shallow-water habitats and adjacent offshore waters in the coastal seascape, environmental conditions and seasonal weather patterns, and stressors such as climate change and fishing, play essential roles in determining fish catch patterns and the behaviour of fishers in the western Indian Ocean region. The findings of the thesis demonstrate the benefits of integrating fish catch records and local knowledge facilitating applied research and coastal resource management.
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| 40. |
- Silas, Mathew Ogalo, 1982-, et al.
(author)
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Using fishers’ local ecological knowledge for management of small-scale fisheries in data-poor regions : Comparing seasonal interview and field observation records in East Africa
- 2023
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In: Fisheries Research. - : Elsevier. - 0165-7836 .- 1872-6763. ; 264
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Journal article (peer-reviewed)abstract
- Fishers, scientists and policy makers need to describe, understand and “agree on” variations in fish catches caused by exploitation and climate change for effective fisheries management. To achieve this, relevant data with sufficient spatiotemporal resolution is a necessity. In regions of the Global South, such as the Western Indian Ocean (WIO), fish catch data useful for management is scarce or non-existing. Still, the potential of local ecological knowledge to provide such information has not been fully utilised in these regions. In this study, we evaluated fishers’ local ecological knowledge (based on interviews) against detailed seasonal fish catch variability data based on catch per unit effort (CPUE) records. Because of the importance of the monsoon seasons for marine resource variability, differences in fish catches during the northeast (NE) and southeast (SE) monsoon seasons were investigated. Fishers’ perceptions generally agreed with catch data records, both showing that the NE monsoon season generally provides higher catch rates than the SE monsoon season. The fishers’ perceptions at two of the landing sites (Nyamisati and Shangani) contradict the recorded observations by showing highest fish catches during the SE monsoon season. It was clear, however, that fishers’ perceptions in these two sites focused on the most valuable target species (prawn and tuna in Nyamisati and Shangani, respectively) rather than total catches. In this particular case, fishers’ perceptions facilitated the significance of taking target species into consideration. The findings of this study highlight the importance of integrating local ecological knowledge into scientific research to help understand the complex dynamics of coastal fisheries and improve the management of data-poor fisheries.
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| 41. |
- Staveley, Thomas A. B., et al.
(author)
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Exploring seagrass fish assemblages in relation to the habitat patch mosaic in the brackish Baltic Sea
- 2020
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In: Marine Biodiversity. - : Springer Science and Business Media LLC. - 1867-1616 .- 1867-1624. ; 50:1
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Journal article (peer-reviewed)abstract
- Assessing the influence of habitat patch dynamics on faunal communities is a growing area of interest within marine ecological studies. This study sets out to determine fish assemblage composition in Zostera marina (L.) meadows and ascertain how habitat structural complexity and seascape structure (i.e. composition and configuration of habitat patches) influenced these assemblages in the northern Baltic Sea. Using ten seascapes (600m in diameter), the fish assemblage was surveyed both in summer and autumn using beach seine. We found that the fish assemblage was clearly dominated by sticklebacks, followed by pipefish and with a general absence of larger piscivorous species. Biomass of fish did not differ between seasons, and low-level carnivores dominated the trophic structure. Overall, at the larger seascape-scale in summer, the proportion of bare soft sediment showed a negative relationship with fish biomass, while diversity of patches was found to exhibit a positive association with fish biomass. At the smaller habitat scale, both seagrass shoot height and density had a negative influence on fish biomass in both seasons. This study outlines new knowledge regarding how the mosaic of habitat patches shape seagrass fish assemblages in the northern Baltic Sea. © 2020, The Author(s).
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| 42. |
- Tarimo, Barnabas Alphonce, 1983-
(author)
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Patterns of fish larvae and zooplankton distribution in mangrove-seagrass seascapes of East Africa
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Mangroves and seagrass meadows create coastal seascapes acting as breeding and nursery grounds for many fish species in tropical areas. Despite increased awareness on the role of these coastal habitats to fish, less knowledge is given to fish larvae distribution and population dynamics, limiting the understanding of major drivers of fish population dynamics and fisheries resources management, particularly in understudied regions such as the Western Indian Ocean. This thesis aimed at understanding seasonal and spatial patterns of fish larvae populations and community composition in relation to key environmental variables and spatiotemporal patterns of zooplankton in mangrove-seagrass seascapes of coastal East Africa. To address the specific goals of the thesis, four studies were performed and presented (Papers I-IV). Paper I focused on seasonal patterns of fish larvae distribution across mangrove-seagrass seascapes at the scale of Zanzibar (Tanzania). In Paper II, we studied seasonal variability of fish larvae distribution and association to environmental characteristics in seagrass meadows (at the scale of East Africa). In Paper III, we investigated seasonal patterns of zooplankton abundance and community composition across mangrove-seagrass seascapes of Zanzibar. Paper IV addressed how zooplankton community composition and water physicochemical properties influence fish larvae abundances across monsoon seasons in mangrove-seagrass seascapes of Zanzibar.The findings of Paper I showed that abundance and richness of fish larvae varied across different months and among habitats (mangrove creeks, nearshore seagrass meadows and inshore seagrass meadows), whereas there were no significant differences between the southeast monsoon (SEM) and northeast monsoon (NEM) seasons. The abundance of fish larvae was particularly high during the SEM season in mangrove creeks at one of the two studied seascapes. Assemblage composition of fish larvae did not change over time in any habitat. The findings suggest that mangroves and seagrass meadows are connected systems with similarity in assemblage compositions. Paper II displayed significant seasonal variations in abundance and community composition of fish larvae in two of the studied areas. It also showed site-specific influences of temperature, salinity, chlorophyll a and current velocities, on fish larvae abundance. Paper III showed that zooplankton abundance and community composition strongly varied across the two monsoon seasons and among habitats, with a significant difference between mangrove creeks and two different seagrass habitats. There was little influence of key environmental parameters during both monsoon seasons, with the exception of salinity (during precipitation peaks in SEM) and chlorophyll a, which influenced zooplankton abundance in mangrove creeks (in the Chwaka Bay seascape). The findings suggest that local hydrodynamics and seasonal variations have strong influences on zooplankton abundance and community composition in mangrove-seagrass seascapes. Paper IV revealed that fish larval abundances and diversity were generally strongly influenced by salinity and water temperature. In the Chwaka Bay seascape, fish larvae abundances were positively associated with abundances of copepods and invertebrate larvae groups of zooplankton in both monsoons and all three habitats. In the Fumba seascape, fish larvae abundances were strongly (positively) associated with temperature, chlorophyll a and zooplankton diversity, and to some degree also (negatively) related to abundances of non-copepod zooplankton (e.g cirripeds larvae).This thesis comprehends essential information on how fish larvae vary in time and space of tropical coastal seascapes, and how these patterns relate to spatiotemporal distributions of zooplankton and contemporary environmental conditions. Area-specific information integrating the monsoonal influence and spatiotemporal dynamics should be considered in conservation efforts of fish larvae and their habitats in coastal East Africa.
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| 43. |
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| 44. |
- Tarimo, Barnabas, et al.
(author)
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Seasonal distribution of fish larvae in mangrove-seagrass seascapes of Zanzibar (Tanzania)
- 2022
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In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
-
Journal article (peer-reviewed)abstract
- Fish larvae supply in nearshore vegetated habitats, such as seagrass meadows and mangroves, contributes significantly to sustainable fish stocks. Yet, little information is available on distribution patterns of fish larvae in mangrove and seagrass habitats of the western Indian Ocean. The present study investigated the abundance, diversity and assemblage composition of fish larvae in mangrove creeks, inshore seagrass meadows (located adjacent to mangroves) and nearshore seagrass meadows (located in-between mangroves and coral reefs) in two coastal seascapes of Zanzibar (Tanzania) across seasons for 1 year. The highest mean abundances of fish larvae were recorded in mangrove creeks, while nearshore- and inshore seagrass meadows showed similar mean abundance levels. Generally, fish larvae representing 42 families were identified, with the fourteen most abundant families comprising 83% of all specimens. Fish larvae communities were dominated by specimens of the postflexion growth stage in all habitats, except in mangrove creeks in one of the two seascapes (i.e. Chwaka Bay) from April through June when abundances of the preflexion and very small-sized individuals were exceptionally high. Slightly higher fish larvae abundances were observed in mangroves during the southeast monsoon compared to the northeast monsoon, and there were also differences across months within monsoon periods for all three habitats studied. Assemblage composition of larvae did, however, not vary significantly in time or space. Our findings suggest that mangroves and seagrass meadows are highly linked shallow-water habitats with high retention of fish larvae contributing to similarity in assemblage compositions across shallow coastal seascapes. Conservation and management efforts should prioritize connected shallow-water seascapes for protection of fish larvae and to uphold sustainable coastal fisheries.
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