| 11. |
- Rivera-Monroy, Victor H., et al.
(författare)
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Salinity and Chlorophyll a as Performance Measures to Rehabilitate a Mangrove-Dominated Deltaic Coastal Region : the Cienaga Grande de Santa Marta-Pajarales Lagoon Complex, Colombia
- 2011
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 34:1, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Salinity, water temperature, and chlorophyll a (chl-a) biomass were used as performance measures in the period 1999-2001 to evaluate the effect of a hydrological rehabilitation project in the Cienaga Grande de Santa Marta (CGSM)-Pajarales lagoon complex, Colombia where freshwater diversions were initiated in 1995 and completed in 1998. The objective of this study was to evaluate how diversions of freshwater into previously hypersaline (>80) environments changed the spatial and temporal distribution of environmental characteristics. Following the diversion, 19 surveys and transects using a flow-through system were surveyed in the CGSM-Pajarales complex to continuously measure selected water quality parameters. Geostatistical analysis indicates that hydrology and salinity regimes and water circulation patterns in the CGSM lagoon are largely controlled by freshwater discharge from the Fundacion, Aracataca, and Sevilla Rivers. Residence times in the CGSM lagoon were similar before (15.5+/-3.8 days) and after (14.2+/-2.0 days) the rehabilitation project and indicated that the system is flushed regularly. In contrast, chl-a biomass was highly variable in the CGSM-Pajarales lagoon complex and not related to discharge patterns. Mean annual chl-a biomass (44-250 mu g L(-1)) following the diversion project was similar to values recorded since the 1980s and still remains among the highest reported in coastal systems around the world owing to its unique hydrology regulated by the Magdalena River and Sierra Nevada de Santa Marta watersheds and the high teleconnection to the El Nino Southern Oscillation (ENSO). Our results confirm that the reduction in salinity in the CGSM lagoon and Pajarales complex during 1999-2000 was largely driven by high precipitation (2500 mm) induced by the ENSO-La Nina rather than by the freshwater diversions.
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| 12. |
- Rodil, Iván F., et al.
(författare)
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The Importance of Environmental and Spatial Factors in the Metacommunity Dynamics of Exposed Sandy Beach Benthic Invertebrates
- 2018
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 41:1, s. 206-217
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Tidskriftsartikel (refereegranskat)abstract
- We studied the contribution of environmental and spatial factors in determining the metacommunity dynamics of benthic macroinvertebrates in ocean-exposed sandy beaches. A combination of different metacommunity models contributed to the structure of the benthic species, suggesting that the interplay of environmental and spatial factors played a key role in determining the beach community structure. Our study highlights the sensitivity of beach invertebrates to environmental factors such as morphodynamic descriptors, and to oceanographic-related variables (e.g., sea-water temperature). The results also suggest significant spatial signals at a large geographical scale. We applied two different species categorizations, high dispersive vs low dispersive and generalist vs specialist, to disentangle the roles of dispersal mode and habitat specialization in the beach metacommunity structure. The strength of the environmental and spatial factors varied depending on the category of species traits considered, emphasizing the value of using different groups of species in explaining variation in metacommunity dynamics. Low dispersive species showed a better ability to track environmental variability than high dispersive species, which were more spatially constrained. Habitat specialists were better able to track environmental variability than generalists, which were mainly predicted by pure spatial factors. A better understanding of the metacommunity dynamics using different species categorizations can help to improve our predictions about exposed beach community structure, and to prioritize management actions to cope with biodiversity loss in such superlative marine environment.
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| 13. |
- Schulz, Kirstin, et al.
(författare)
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The Fate of Mud Nourishment in Response to Short-Term Wind Forcing
- 2020
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 44, s. 88-102
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Tidskriftsartikel (refereegranskat)abstract
- In this study, results from a realistic 3D hydrodynamic and sediment transport model, applied to a channel in the Dutch Wadden Sea, are analyzed in order to assess the effect of short-term wind forcing, the impact of fresh water effects, and the variability induced by the spring-neap cycle on the transport of suspended sediment. In the investigated region, a pilot study for sediment nourishment, the so-called Mud Motor, is executed. This project aims for the beneficial re-use of dredged harbor sediments through the disposal of these sediments at a location where natural currents are expected to transport them toward a nearby salt marsh area. The model results presented in this study advance the understanding of the driving forces that determine sediment transport in shallow, near-coastal zones, and can help to improve the design of the Mud Motor. In the investigated channel, which is oriented parallel to the coastline, tidal asymmetries generally drive a transport of sediment in flood direction. It was found that already moderate winds along the channel axis reverse (wind in ebb direction), or greatly enhance this transport, up to an export of sediment over the adjacent water shed (wind in flood direction). The most beneficial wind conditions (moderate westerly winds) can cause an accumulation of more than 90% of the initial 200 tons sediment pool on the intertidal area; during less favorable conditions (northeasterly winds), less than a third of the dumped sediment is transported onto the mudflat. On-shore winds induce a transport toward the coast. Surprisingly, sediment pathways are only sensitive to the exact disposal location in the channel during wind conditions that counteract the tidally driven transport, and freshwater effects play no significant role for the dispersal of sediment.
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| 14. |
- Signori, Camila N., et al.
(författare)
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Temporal Variability of Dark Carbon Fixation and Bacterial Production and Their Relation with Environmental Factors in a Tropical Estuarine System
- 2018
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Ingår i: Estuaries and Coasts. - : SPRINGER. - 1559-2723 .- 1559-2731. ; 41:4, s. 1089-1101
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Tidskriftsartikel (refereegranskat)abstract
- Dark carbon fixation (DCF) is considered an important energy source in aquatic environments, although it has been neglected for a long time. DCF is known to be relevant in ecosystems associated with redoxclines, shallow-water sulfide-rich habitats, deep-sea vents, cold seeps, and even in coastal waters associated with upwelling events. The aim of this study was to evaluate the relative importance of DCF in relation to heterotrophic bacterial production (BP), as well as how these rates affect each other, and how they are influenced by the environmental factors. This study was conducted monthly during 2 years in a tropical eutrophic bay (Guanabara Bay), where two stations were sampled and compared. DCF and BP were measured by C-14-bicarbonate and H-3-leucine incorporation, respectively, and incubations in the dark. Our results showed that DCF is not a quantitatively relevant process in this estuarine system, when compared to heterotrophic BP, and possibly occurred via anaplerotic reactions. Relatively higher DCF rates were associated with less oxygenated waters at the more polluted station and during the wet summer-spring, when the water column is more stratified. BP rates presented clear spatial patterns, according to pollution and depth gradients, with higher rates in more polluted areas, and also at surface waters. The hydrodynamics combined with other environmental conditions (precipitation, temperature, dissolved organic carbon, and nutrients) may control the distribution of DCF and BP over space and time. The allochthonous inputs of organic matter are more important than DCF-derived organic carbon to bacterioplankton in this polluted and eutrophic bay, where the heterotrophic metabolism prevails.
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| 15. |
- Sundbäck, Kristina, 1949, et al.
(författare)
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Nitrogen dynamics in nontidal littoral sedimens: Role of microphytobenthos and denitrification
- 2006
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Ingår i: Estuaries and Coasts. - 1559-2723 .- 1559-2731. ; 29:6B, s. 1196-1211
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Tidskriftsartikel (refereegranskat)abstract
- Previous measurements from cool microtidal temperate areas suggest that microphytobenthic incorporation of nitrogen (N) exceeds N removal by denitrification in illuminated shallow-water sediments. The present study investigates if this is true also for fully nontidal sediments in the Baltic Sea., Sediment-water fluxes of inorganic (DIN) and, organic nitrogen (DON) and oxygen, as well as denitrification, were measured in early autumn and spring, in light and dark, at four sites representing different sediment types. All sediments were autotrophic during the daytime both in the autumn and spring. On a 24-h time scale, they were autotrophic in the spring and heterotrophic in early autumn. Sediments funcitoned as sources of DIN and DON during the autumn and sinks during the spring, with DON fluxes dominating or being as important as DIN fluxes. Microphytobenthos (MPB) activity controlled fluxes of both DIN and DON. Significant differences between sites were found, although sediment type (sand or silt) had no consistent effect on the magnitude of MPB production or nutrient fluxes. The clearest effect related to sediment type was found for denitrification, although only in the autumn, with higher rates in silty sediments. Estimated N assimilation by MPB, based on both net primary production (0.7–6.5 mmol N m−2 d−1) and on 80% of gross primary production (1.9–9.4 mmol N m−2 d−1) far exceeded measured rates of denitrification (0.01–0.16 mmol N m−2 d−1). A theoretical calculation showed that MPB may incorporate between 40% and 100% of the remineralized N, while denitrification removes, <5%. MPB assimilation of N appears to be a far more important N consuming process than denitrification in these nontidal, shallow-water sediments.
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| 16. |
- Thang, Nguyen Manh, et al.
(författare)
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The Impact of Sediment and Carbon Fluxes on the Biogeochemistry of Methane and Sulfur in Littoral Baltic Sea Sediments (Himmerfjarden, Sweden)
- 2013
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 36:1, s. 98-115
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Tidskriftsartikel (refereegranskat)abstract
- Three sediment stations in Himmerfjarden estuary (Baltic Sea, Sweden) were sampled in May 2009 and June 2010 to test how low salinity (5-7 aEuro degrees), high primary productivity partially induced by nutrient input from an upstream waste water treatment plant, and high overall sedimentation rates impact the sedimentary cycling of methane and sulfur. Rates of sediment accumulation determined using Pb-210(excess) and Cs-137 were very high (0.65-0.95 cm year(-1)), as were the corresponding rates of organic matter accumulation (8.9-9.5 mol C m(-2) year(-1)) at all three sites. Dissolved sulfate penetrated < 20 cm below the sediment surface. Although measured rates of bicarbonate methanogenesis integrated over 1 m depth were low (0.96-1.09 mol m(-2) year(-1)), methane concentrations increased to > 2 mmol L-1 below the sulfate-methane transition. A steep gradient of methane through the entire sulfate zone led to upward (diffusive and bio-irrigative) fluxes of 0.32 to 0.78 mol m(-2) year(-1) methane to the sediment-water interface. Areal rates of sulfate reduction (1.46-1.92 mol m(-2) year(-1)) integrated over the upper 0-14 cm of sediment appeared to be limited by the restricted diffusive supply of sulfate, low bio-irrigation (alpha = 2.8-3.1 year(-1)), and limited residence time of the sedimentary organic carbon in the sulfate zone. A large fraction of reduced sulfur as pyrite and organic-bound sulfur was buried and thus escaped reoxidation in the surface sediment. The presence of ferrous iron in the pore water (with concentrations up to 110 mu M) suggests that iron reduction plays an important role in surface sediments, as well as in sediment layers deep below the sulfate-methane transition. We conclude that high rates of sediment accumulation and shallow sulfate penetration are the master variables for biogeochemistry of methane and sulfur cycling; in particular, they may significantly allow for release of methane into the water column in the Himmerfjarden estuary.
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| 17. |
- Tomczak, Maciej T., et al.
(författare)
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Evaluation of Trends and Changes in the Gulf of Gdansk Ecosystem-an Integrated Approach
- 2016
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 39:3, s. 593-604
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Tidskriftsartikel (refereegranskat)abstract
- An integrated trend assessment was conducted for the Gulf of GdaAsk (GoG), Baltic Sea for the period 1994-2010 to describe changes and potentially important drivers of the ecosystem. We found changes in the biota, including an increase in open sea taxa (flatfish, sprat and cod), a decrease in typical coastal species such as eelpout and lumpfish and an increase in primary production. The analyses further suggest that changes in the food web were driven by a combination of anthropogenic pressures (e.g., nutrient loadings and fisheries) and possible interactions with climatic disturbance. Our analyses show that significant changes occurred in the GoG ecosystem between 1994 and 2010. The primary drivers and mechanisms of these changes are discussed. We describe this alteration of the GoG within the context of similar temporal patterns identified in adjacent areas.
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| 18. |
- Vaquer-Sunyer, Raquel, et al.
(författare)
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Experimental Evaluation of the Response of Coastal Mediterranean Planktonic and Benthic Metabolism to Warming
- 2013
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2731 .- 1559-2723. ; 36:4, s. 697-707
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Tidskriftsartikel (refereegranskat)abstract
- The Mediterranean Sea has been identified as one of the hotspots for climate change. Intense warming in the Mediterranean Sea may have strong implications for biological activity and ecosystem functioning. To elucidate the effects of warming on planktonic and benthic metabolism, we performed experiments under different increasing temperature regimes, ranging from three to six different temperatures. The lowest range of temperatures assessed was of 2.6 A degrees C and the maximum was 7.5 A degrees C. Our results suggest that a 6 A degrees C warming of the Mediterranean waters may yield a mean increment in planktonic respiration rates of coastal communities of 24 %, higher than the mean increase expected for planktonic gross primary production (9 %). These results confirm earlier theories, and agree with previous experiments, of a higher increase in respiration rates than in primary production with warming, with the subsequent consequences for the carbon cycle, resulting in a negative feedback to climate warming, as ocean communities will capture less CO2.
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| 19. |
- Vaquer-Sunyer, Raquel, et al.
(författare)
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Temperature Dependence of Oxygen Dynamics and Community Metabolism in a Shallow Mediterranean Macroalgal Meadow (Caulerpa prolifera)
- 2012
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2731 .- 1559-2723. ; 35:5, s. 1182-1192
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia is emerging as a major threat to marine coastal biota. Predicting its occurrence and elucidating the driving factors are essential to set successful management targets to avoid its occurrence. This study aims to elucidate the effects of warming on the likelihood of hypoxia. High-frequency dissolved oxygen measurements have been used to estimate gross primary production (GPP), net ecosystem production (NEP) and community respiration (CR) in a shallow macroalgae (Caulerpa prolifera) ecosystem in a highly human-influenced closed Mediterranean bay. Daily averaged GPP and CR ranged from 0 to 1,240.9 and 51.4 to 1,297.3 mmol O-2 m(-2) day(-1), respectively. The higher GPP and CR were calculated for the same day, when daily averaged water temperature was 28.3 A degrees C, and resulted in a negative NEP of -56.4 mmol O-2 m(-2) day(-1). The ecosystem was net heterotrophic during the studied period, probably subsidized by allochthonous organic inputs from ground waters and from the surrounding town and boating activity. Oxygen dynamics and metabolic rates strongly depend on water temperature, with lower oxygen content at higher temperatures. The probability of hypoxic conditions increased at a rate of 0.39 % A degrees C-1 (+/- 0.14 % A degrees C-1). Global warming will increase the likelihood of hypoxia in the bay studied, as well as in other semi-enclosed bays.
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| 20. |
- Wadnerkar, P. D., et al.
(författare)
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Contrasting Radium-Derived Groundwater Exchange and Nutrient Lateral Fluxes in a Natural Mangrove Versus an Artificial Canal
- 2021
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 44, s. 123-136
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Tidskriftsartikel (refereegranskat)abstract
- Artificial canals may function differently than the natural coastal wetlands, floodplains, and estuaries they often replace. Here, we assess the impact of canal estate development on saline groundwater exchange (tidal pumping) and associated nutrient fluxes. Time series observations of short-lived radium isotopes and dissolved nutrients were performed in a canal estate and a nearby mangrove creek in subtropical Australia. A mass balance model based on(223)Ra (1.3 +/- 0.4 and 3.4 +/- 0.9 cm day(-1)in the mangrove and canal, respectively) and(224)Ra (2.8 +/- 3.0 and 5.4 +/- 4.6 cm day(-1)) revealed tidally driven groundwater exchange rates were similar to 2-fold greater in the canal. Lateral fluxes of total dissolved nitrogen (TDN) from the nearby estuary into the canal estate were comparable with the mangrove creek (8.4 and 9.1 mmol m(-2) day(-1)in the mangrove and canal, respectively). Groundwater flows into the canal released similar to 5-fold more TDN than the mangrove. As expected, mangroves appear to be more efficient at retaining groundwater-derived nitrogen than vegetation-stripped, sandy canals. Overall, this study demonstrates that land reclamation for canal estate development not only drives losses of ecosystem services, but also modifies groundwater and related nutrient exchange with coastal surface waters.
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