| 1. |
- Hernroth, Bodil, 1951-, et al.
(författare)
-
Impact of ocean acidification on antimicrobial activity in gills of the blue mussel (Mytilus edulis)
- 2016
-
Ingår i: Fish and Shellfish Immunology. - : Elsevier. - 1050-4648 .- 1095-9947. ; 55, s. 452-459
-
Tidskriftsartikel (refereegranskat)abstract
- Here, we aimed to investigate potential effects of ocean acidification on antimicrobial peptide (AMP) activity in the gills of Mytilus edulis, as gills are directly facing seawater and the changing pH (predicted to be reduced from ∼8.1 to ∼7.7 by 2100). The AMP activity of gill and haemocyte extracts was compared at pH 6.0, 7.7 and 8.1, with a radial diffusion assay against Escherichia coli. The activity of the gill extracts was not affected by pH, while it was significantly reduced with increasing pH in the haemocyte extracts. Gill extracts were also tested against different species of Vibrio (V. parahaemolyticus, V. tubiashii, V. splendidus, V. alginolyticus) at pH 7.7 and 8.1. The metabolic activity of the bacteria decreased by ∼65–90%, depending on species of bacteria, but was, as in the radial diffusion assay, not affected by pH. The results indicated that AMPs from gills are efficient in a broad pH-range. However, when mussels were pre-exposed for pH 7.7 for four month the gill extracts presented significantly lower inhibit of bacterial growth. A full in-depth proteome investigation of gill extracts, using LC-Orbitrap MS/MS technique, showed that among previously described AMPs from haemocytes of Mytilus, myticin A was found up-regulated in response to lipopolysaccharide, 3 h post injection. Sporadic occurrence of other immune related peptides/proteins also pointed to a rapid response (0.5–3 h p.i.). Altogether, our results indicate that the gills of blue mussels constitute an important first line defence adapted to act at the pH of seawater. The antimicrobial activity of the gills is however modulated when mussels are under the pressure of ocean acidification, which may give future advantages for invading pathogens.
|
|
| 2. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Accumulation and elimination kinetics of manganese from different tissues of the Norway lobster Nephrops norvegicus (L.)
- 1999
-
Ingår i: Aquatic Toxicology. - 0166-445X. ; 46:2, s. 127-137
-
Tidskriftsartikel (refereegranskat)abstract
- The exposure of marine benthic animals to dissolved manganese (Mn) occurs from metalliferous outlets or the enhanced flux of dissolved manganese from sediments during hypoxia. A prerequisite to valid interpretation of manganese concentrations measured in animals in situ is a thorough understanding of accumulation and elimination rates of this metal by relevant target tissues in organisms exposed to environmentally realistic manganese concentrations. Norway lobster, Nephrops norvegicus, accumulated manganese when exposed to solutions of < 0.06 (background), 5 and 10 mg Mn l(-1) for 20 days and was allowed to eliminate any accumulated manganese in undosed sea water for a further 20 days. During this period individual N. norvegicus were dissected into a number of components (brain, ventral ganglion, haemolymph, midgut gland, gills and exoskeleton) and the manganese concentration of each was analysed. Manganese accumulation reached a plateau after 1.25 days in all tissues except for midgut gland, which continued to accumulate manganese during the entire exposure period. In general, the manganese elimination was significantly slower than accumulation and reached a plateau after 1.25-2.5 days (except the gills) following exposure to clean sea water. The accumulation factor (AF), when compared to maximum concentrations in control and exposed animals, was highest in the haemolymph (x 88) followed by nerve tissue (x 22) at the 10 mg Mn l(-1) exposure. The concentration factor (CF), when comparing manganese accumulation in tissues (wet weight) with exposure concentration, was 1.2-3.5 and for most tissues was similar for both exposure concentrations or slightly higher in the 5 mg Mn l(-1) exposure-indicating net accumulation of manganese in all tissues with a saturation effect with increasing exposure concentrations. Thus, from these experiments it may be concluded that measured manganese concentrations in N. norvegicus give an indication of recent exposure to manganese concentrations in the bottom waters of their habitats. (C) 1999 Elsevier Science B.V. All rights reserved.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Eriksson, Susanne P., 1964, et al.
(författare)
-
Behaviour and tolerance to hypoxia in juvenile Norway lobster (Nephrops norvegicus) of different ages
- 1997
-
Ingår i: Marine Biology. - 0025-3162. ; 128:1, s. 49-54
-
Tidskriftsartikel (refereegranskat)abstract
- The annual occurrence of hypoxia (<25% oxygen saturation) in the bottom waters along the Swedish west coast coincides with the postlarval settlement of Norway lobster, Nephrops norvegicus (L.). This study investigates behaviour and the experimental effects of low oxygen concentrations in juvenile N. norvegicus of different ages. All experimental individuals were reared to the juvenile (postlarval) stage in the laboratory and then given sediment as a substratum. Behavioural responses to low oxygen concentrations were tested in early and late Postlarvae 1 exposed to normoxia (>80% oxygen saturation, pO(2) > 16.7 kPa), moderate hypoxia (30% oxygen saturation, pO(2) = 6.3 kPa) and hypoxia (25% oxygen saturation, pO(2) = 5.2 kPa). The experiments were run for a maximum period of 24 h or until individuals died. Behaviour was studied using sequential video recordings of four behavioural activities: digging, walking, inactivity or flight (escape swimming up into the water column). Behaviour and mortality changed with lowered oxygen concentrations; energetically costly activities (such as walking) were reduced, and activity in general declined. In normoxia, juveniles initially walked and then burrowed, but when exposed to hypoxia they were mainly inactive with occasional outbursts of escape swimming. To increase oxygen availability the juveniles were observed to raise their bodies on stilted legs (similar to adults in hypoxic conditions), but oxygen saturations of 25% were lethal within 24 h. The results suggest that the main gas exchanges of early postlarval stages occur over the general body surface. Burrowing behaviour was tested in Postlarvae 1 and 2 of different ages held in >80% oxygen saturation for 1 wk. The difference in time taken to complete a V-shaped depression or a U-shaped burrow was measured. The results showed a strong negative relationship between postlarval age and burrowing time, but all individuals made a burrow. Juveniles were more sensitive to hypoxia than adults. Thus, the possible consequences of episodic hypoxia for the recruitment of Nephrops norvegicus and for the recolonization of severely affected areas are discussed.
|
|
| 6. |
- Eriksson, Susanne P., 1964, et al.
(författare)
-
Manganese in the haemolymph and tissues of the Norway lobster, Nephrops norvegicus (L.), along the Swedish west coast, 1993-1995
- 1998
-
Ingår i: Hydrobiologia. - 0018-8158. ; 376, s. 255-264
-
Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal differences in manganese levels in Norway lobsters, Nephrops norvegicus, were compared with the concentrations of manganese in their environment. Animals were collected twice yearly (spring and autumn) from seven stations along the Swedish west coast and from one site in the Faroe Islands, during 1993-94, and analysed for manganese tissue concentration and content. Animals were also collected from the Swedish stations in the autumn of 1995 and compared with animals from a stressful environment, frequently exposed to hypoxia. There were large spatial differences and the animals collected in the Faroe Islands contained (in most tissues) one order of magnitude less manganese than the animals collected along the Swedish west coast. The manganese level of the haemolymph correlated most closely with the manganese concentration the animal was exposed to in the field. The manganese concentration of the female gonad tissue did however not differ with space nor time and remained stable around 5.1 mu g Mn g(-1) dw tissue throughout the investigation. Animals taken from an area with known repeated hypoxia in the bottom water, had high levels of manganese in especially the gills. Their mean manganese concentration was over 20 times higher (1560 mu g Mn g(-1) dw tissue) than the manganese concentration in animals from the other Swedish stations. They also had more than threefold the amount of manganese in the brain, giving a mean concentration of 193 mu g Mn g(-1) dw tissue.
|
|
| 7. |
- Eriksson, Susanne P., 1964, et al.
(författare)
-
Stress Biology and Immunology in Nephrops norvegicus
- 2013
-
Ingår i: Advances in Marine Biology. - : Elsevier. - 0065-2881. ; 64, s. 149-200
-
Tidskriftsartikel (refereegranskat)abstract
- The Norway lobster Nephrops norvegicus lives at low-light depths, in muddy substrata of high organic content where water salinities are high and fluctuations in temperature are moderate. In this environment, the lobsters are naturally exposed to a number of potential stressors, many of them as a result of the surficial breakdown of organic material in the sediment. This process (early diagenesis) creates a heterogeneous environment with temporal and spatial fluctuations in a number of compounds such as oxygen, ammonia, metals, and hydrogen sulphide. In addition to this, there are anthropogenically generated stressors, such as human-induced climate change (resulting in elevated temperature and ocean acidification), pollution and fishing. The lobsters are thus exposed to several stressors, which are strongly linked to the habitat in which the animals live. Here, the capacity of Nephrops to deal with these stressors is summarised. Eutrophication-induced hypoxia and subsequent metal remobilisation from the sediment is a well-documented effect found in some wild Nephrops populations. Compared to many other crustacean species, Nephrops is well adapted to tolerate periods of hypoxia, but prolonged or severe hypoxia, beyond their tolerance level, is common in some areas. When the oxygen concentration in the environment decreases, the bioavailability of redox-sensitive metals such as manganese increases. Manganese is an essential metal, which, taken up in excess, has a toxic effect on several internal systems such as chemosensitivity, nerve transmission and immune defence. Since sediment contains high concentrations of metals in comparison to sea water, lobsters may accumulate both essential and non-essential metals. Different metals have different target tissues, though the hepatopancreas, in general, accumulates high concentrations of most metals. The future scenario of increasing anthropogenic influences on Nephrops habitats may have adverse effects on the fitness of the animals.
|
|
| 8. |
|
|
| 9. |
- Hernroth, Bodil, 1951-, et al.
(författare)
-
Immune suppression of the echinoderm Asterias rubens (L.) following long-term ocean acidification
- 2011
-
Ingår i: Aquatic Toxicology. - 0166-445X .- 1879-1514. ; 103:3-4, s. 222-224
-
Tidskriftsartikel (refereegranskat)abstract
- We compared effects of exposure to predict near-future (2100) ocean acidification (OA; pH 7.7) and normal seawater (Control; pH 8.1) on immune and stress responses in the adult sea star Asterias rubens. Analyses were made after one week and after six months of continuous exposure. Following one week exposure to acidified water, the pH of coelomic fluid was significantly reduced. Levels of the chaperon Hsp70 were elevated while key cellular players in immunity, coelomocytes. were reduced by approximately 50%. Following long-term exposure (six months) levels of Hsp70 returned to control values, whereas immunity was further impaired, evidenced by the reduced phagocytic capacity of coelomocytes and inhibited activation of p38 MAP-kinase. Such impacts of reduced seawater pH may have serious consequences for resistance to pathogens in a future acidified ocean.
|
|
| 10. |
- Nilsson Sköld, Helen, 1970, et al.
(författare)
-
Motoric impairment following manganese exposure in asteroide chinoderms
- 2015
-
Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 167, s. 31-37
-
Tidskriftsartikel (refereegranskat)abstract
- In the oceans, naturally occurring manganese (Mn) is released from the sediments during events of hypoxia. While neuro- and immuno-toxic effects of bioavailable manganese are well documented for crustaceans, studies of similar effects of manganese on other marine invertebrates are comparatively few. Here, we developed a new functional test “the repeated turning assay” to investigate if manganese exposure at ∼12 mg L−1 affected motoric behaviour of two asteroid echinoderms, the Common sea star, Asterias rubens, and the Black brittle star, Ophiocomina nigra. By measuring of the turning-over capacity, from dorsal to ventral position, after one and two weeks of manganese exposure, we showed that for both species Mn exposure significantly delayed the ability to turn. After a recovery period of two weeks, the capacity of turning-over was not restored to that of unexposed animals neither for A. rubens nor for O. nigra. Further investigation of sea stars showed that Mn accumulated ∼5 fold in the tube feet, organs involved in their turning-over activity, and the high concentration remained after the recovery period. In the tube feet we also recorded an increased activity of acetylcholinesterase (AChE), here used as a proxy for neuromuscular disturbances. The results indicated that Mn induces neuromuscular disturbance in echinoderms which is important news, given that previous studies have concluded that adult echinoderms are relatively tolerant to Mn.
|
|
| 11. |
- Asplund, Maria. E., 1970, et al.
(författare)
-
Ocean acidification and host-pathogen interactions: blue mussels, Mytilus edulis, encountering Vibrio tubiashii
- 2014
-
Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 16:4, s. 1029-1039
-
Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification (OA) can shift the ecological balance between interacting organisms. In this study, we have used a model system to illustrate the interaction between a calcifying host organism, the blue mussel Mytilus edulis and a common bivalve bacterial pathogen, Vibrio tubiashii, with organisms being exposed to a level of acidification projected to occur by the end of the 21st century. OA exposures of the mussels were carried out in relative long-term (4 months) and short-term (4 days) experiments. We found no effect of OA on the culturability of V.tubiashii, in broth or in seawater. OA inhibited mussel shell growth and impaired crystalline shell structures but did not appear to affect mussel immune parameters (i.e haemocyte counts and phagocytotic capacity). Despite no evident impact on host immunity or growth and virulence of the pathogen, V.tubiashii was clearly more successful in infecting mussels exposed to long-term OA compared to those maintained under ambient conditions. Moreover, OA exposed V.tubiashii increased their viability when exposed to haemocytes of OA-treated mussel. Our findings suggest that even though host organisms may have the capacity to cope with periods of OA, these conditions may alter the outcome of host–pathogen interactions, favouring the success of the latter.
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Between-individual variation in haemocyanin concentrations in the Norway lobster Nephrops norvegicus following exposure to hypoxia and manganese
- 2003
-
Ingår i: Marine Biology. - 0025-3162. ; 143:2, s. 267-273
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental hypoxia and the release of reduced manganese (Mn) are often combined stress factors in marine sediments. Previous investigations have shown that hypoxia induces variable responses in the concentration of the respiratory pigment haemocyanin (Hc) of crustaceans. A recent study demonstrated that the magnitude and direction of the changes was dependent on the initial level of Hc in individuals of the Norway lobster Nephrops norvegicus. The changes also took place within 24 h rather than days as suggested by previous studies. In this present study we investigated changes of Hc in individual N. norvegicus in uncontaminated sea water after exposure to and release from realistic hypoxic stress (PO2 = 6.0 kPa). Furthermore we investigated how concomitant exposure to realistic concentrations of manganese (20 mg 1(-1)) modified the responses we observed. We confirmed a between-individual variation in response and a change in Hc towards an optimum level after hypoxia, but also showed that changes that took place post-hypoxic exposure occurred over a timescale similar to that of the hypoxic response itself. Manganese exposure resulted in no significant changes in Hc whereas Mn exposure combined with hypoxia resulted in a significant decrease (15%) in all individuals independent of initial Hc. N. norvegicus was thus unable to compensate for the effects of hypoxia by synthesis of Hc after exposure to naturally occurring Mn concentrations.
|
|
| 15. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Effects of depth and overgrowth of ephemeral macroalgae on a remote subtidal NE Atlantic eelgrass (Zostera marina) community
- 2022
-
Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X. ; 177
-
Tidskriftsartikel (refereegranskat)abstract
- We conducted a short-term field sampling complemented with time integrating stable isotope analysis to ho- listically investigate status and ecological interactions in a remote NE Atlantic Zostera marina meadow. We found high nutrient water concentrations, large biomass of fast-growing, ephemeral macroalgae, low abundance, and biodiversity of epifauna and a food web with thornback ray (Raja clavata) as intermediate and cod (Gadus morhua) as top predator. We observed no variation with increasing depth (3.5–11 m) except for decreasing shoot density and biomass of Zostera and macroalgae. Our results indicate that the Finnøya Zostera ecosystem is eutrophicated. During the past three to four decades, nutrients from aquaculture have steadily increased to reach 75% of anthropogenic input while the coastal top predator cod has decreased by 50%. We conclude that bottom-up regulation is a predominant driver of change since top-down regulation is generally weak in low density and exposed Zostera ecosystems such as Finnøya.
|
|
| 16. |
|
|
| 17. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Gödning och överfiske förstör fiskens barnkammare
- 2005
-
Ingår i: Miljöforskning för ett uthålligt samhälle: I havets dunkla djup. - 1650-4925. ; 4
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nya resultat visar att övergödning och överfiske gynnar vissa faunagrupper så att alger kväver det viktiga ålgräset, som utgör barnkammare för torsk och abborre. Ålgräset har minskat med 60 procent på 20 år skriver Susanne P Baden och Per O Moksnes i artikeln Gödning och överfiske förstör fiskens barnkammare.
|
|
| 18. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Manganese accumulation by the antennule of the Norway lobster Nephrops norvegicus (L.) as a biomarker of hypoxic events.
- 2003
-
Ingår i: Marine Environmental Research. - 0141-1136. ; 55:1, s. 59-71
-
Tidskriftsartikel (refereegranskat)abstract
- In laboratory tests, manganese accumulation by the appendages of the sediment burrowing Norway lobster, Nephrops norvegicus (L.) (including the lateral antennules) was approximately three times greater [600 mug Mn g(-1) (dry weight) after 5 days in 20 mg Mn l(-1)] than that by the carapace. The accumulation was linearly dose-dependent (10-40 mg Mn l(-1)) and duration-dependent (2-30 days), and showed no decrease after 3 weeks in undosed seawater. A high manganese uptake to the lateral antennules during hypoxia in the field was verified from the SE Kattegat, Sweden. These results indicate that accumulation of Mn on the mobile appendages of the Norway lobster fulfils most of the criteria for a biomarker of exposure to hypoxia. Using these measurements in conjunction with Mn concentrations in the internal tissues, it may be possible to resolve both the timing and the extent of the Mn exposure and the underlying hypoxic event. (C) 2002 Elsevier Science Ltd. All rights reserved.
|
|
| 19. |
|
|
| 20. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Relative importance of trophic interactions and nutrient enrichment in seagrass ecosystems: A broad-scale field experiment in the Baltic-Skagerrak area.
- 2010
-
Ingår i: Limnology and Oceanography. - 1541-5856. ; 55:3, s. 1435-1448
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction of eutrophication and predation in structuring seagrass Zostera marina L. ecosystems was assessed in a field experiment in three regions along an estuarine salinity gradient, from southern Finland to the Skagerrak area of the Swedish west coast. All regions are considered to be affected by eutrophication and overfishing but differ in the abundance of intermediate predators (e.g., small fish, shrimp, and crabs), mesograzers, and the biomass of epiphytic algae. Using transplanted Zostera (eelgrass), nutrient levels and intermediate predator abundance were manipulated in a full-factorial cage experiment. On the Swedish west coast, where ambient densities of mesograzers are very low, epiphytic algae responded strongly to nutrient enrichment, resulting in significantly reduced growth of eelgrass. At the Baltic sites however, where ambient densities of mesograzers are high, no significant growth of epiphytic algae was detected, and only grazer biomass responded to nutrient enrichment. Predation from small fish, shrimp, and crabs decreased the biomass of mesograzers by . 98% on the Swedish west coast, but natural predators had no significant effect on mesograzers biomass at the Baltic sites. Predation and nutrient enrichment interacted to affect the growth of eelgrass by controlling the biomass of mesograzers and nuisance algae. The differing effect of nutrient enrichment and grazing in the three regions may therefore be a result of the prevailing low and high predation pressure on mesograzers in Zostera. This absence or presence of predation may derive from interregional changes in trophic interactions, possibly caused by a combination of eutrophication and overfishing.
|
|
| 21. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Shift in seagrass food web structure over decades is linked to overfishing
- 2012
-
Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 451, s. 61-73
-
Tidskriftsartikel (refereegranskat)abstract
- Empirical field studies in seagrass have revealed that overgrowth by filamentous algae which reduces seagrass growth can be explained by a top-down cascading effect caused by declines in top predators, which is enforced by eutrophication. On the Swedish west coast, 60% of the seagrass has disappeared since the 1980s. We hypothesised that overfishing, responsible for a >90% decline in the cod stock, and the 4 to 8 times increase in nutrient load since the 1930s have altered the seagrass structure and function during recent decades. We used quantitative samples from the 1980s and 2000s and analysed the trends in abundance of the 4 feeding guilds: top predatory fish, intermediate predatory fish, crustacean omnivores and mesoherbivores. Since the 1980s, the commercial catch of gadoids on the Swedish west coast has decreased by >90 %, and here we found that the biomass of top predators (gadoids and trout) that forage in seagrass has decreased by approximately 80%. In contrast, the biomass of intermediate predatory fish (gobids and sticklebacks) has increased 8 times during summer and 11 times during autumn, while mesoherbivores (idoteids and gammarids >7 mm) have more or less disappeared from the seagrass bed. We thus found clear evidence that a shift in seagrass food web structure has taken place over the last 3 decades. Combining these findings with our recent empirical results from field cage experiments in the Skagerrak seagrass, where we manipulate top-down and bottom-up regulation, we conclude that lack of grazers in concert with eutrophication most likely contributed to the overgrowth by filamentous algae and disappearance of the seagrass on the Swedish west coast.
|
|
| 22. |
- Baden, Susanne P., 1952, et al.
(författare)
-
Vanishing seagrass (Zostera marina, L.) in Swedish coastal waters
- 2003
-
Ingår i: Ambio. - 0044-7447. ; 32:5, s. 374-377
-
Tidskriftsartikel (refereegranskat)abstract
- Along the Swedish Skagerrak coast eelgrass (Zostera marina) is a dominant phanerogam on shallow soft bottoms. Eelgrass meadows are important biotopes for many crustacean and fish species being either migratory or stationary. During the 1980s, inventories of the shallow coastal areas with eelgrass have been carried out along the Swedish west coast as a basis for coastal zone management. In the present study we revisited 2000 ha of eelgrass meadows in 5 coastal regions along 200 km of the Skagerrak coast. The inventory was made with the same methods (aquascope) as during the 1980s, but increasing the mapping accuracy by using a Global Positioning System (GPS). The results from this study show that the areal extension of Zostera marina has decreased 58% in 10-15 years with great regional variations. The decline was mainly restricted to the shallow parts of the meadow. The causes and ecological consequences are discussed.
|
|
| 23. |
- Boström, C., et al.
(författare)
-
Distribution, structure and function of Nordic eelgrass (Zostera marina) ecosystems: Implications for coastal management and conservation
- 2014
-
Ingår i: Aquatic conservation. - : Wiley. - 1052-7613. ; 24:3, s. 410-434
-
Forskningsöversikt (refereegranskat)abstract
- This paper focuses on the marine foundation eelgrass species, Zostera marina, along a gradient from the northern Baltic Sea to the north-east Atlantic. This vast region supports a minimum of 1480km2 eelgrass (maximum >2100km2), which corresponds to more than four times the previously quantified area of eelgrass in Western Europe. Eelgrass meadows in the low salinity Baltic Sea support the highest diversity (4-6 spp.) of angiosperms overall, but eelgrass productivity is low (<2g dw m-2 d-1) and meadows are isolated and genetically impoverished. Higher salinity areas support monospecific meadows, with higher productivity (3-10g dw m-2 d-1) and greater genetic connectivity. The salinity gradient further imposes functional differences in biodiversity and food webs, in particular a decline in number, but increase in biomass of mesograzers in the Baltic. Significant declines in eelgrass depth limits and areal cover are documented, particularly in regions experiencing high human pressure. The failure of eelgrass to re-establish itself in affected areas, despite nutrient reductions and improved water quality, signals complex recovery trajectories and calls for much greater conservation effort to protect existing meadows. The knowledge base for Nordic eelgrass meadows is broad and sufficient to establish monitoring objectives across nine national borders. Nevertheless, ensuring awareness of their vulnerability remains challenging. Given the areal extent of Nordic eelgrass systems and the ecosystem services they provide, it is crucial to further develop incentives for protecting them. © 2014 The Authors.
|
|
| 24. |
- Dunca, Elena, et al.
(författare)
-
Using ocean quahog (Arctica islandica) shells to reconstruct palaeoenvironment in A-resund, Kattegat and Skagerrak, Sweden
- 2009
-
Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 98:1, s. 3-17
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Shells of Arctica islandica collected between 1884 and 2004 from A-resund, Kattegat and Skagerrak (Swedish West Coast) were used to monitor local climate variations and the influence of human activities on the local environment. For this purpose, we analysed the growth, structure and chemical composition of these shells and compared them with shells collected from Kiel Bay, Norway and Iceland. The growth rate of the studied shells registers an NAO periodicity of ca 8 years. However, the observed signal is weak because of other environmental interferences that are either of natural or anthropogenic origin. For example, the oxygen isotope ratios show temperature fluctuation, but also the influx of low salinity water. Higher contents of S, N, Cu, Zn, As, Cd and P in shell portions formed during the last century are related to human activities such as mining and industrial development. Our study indicates that in order to use Arctica shells as archives of climate change it is necessary to study the full range of environmental data that is recorded in the shells by using a multi element and isotope approach in combination with different analytical techniques including investigation of growth rates and shell structure.
|
|
| 25. |
- Eklöf, Johan, 1978, et al.
(författare)
-
Sjögräsängar - hotade av både övergödning och överfiske?
- 2009
-
Ingår i: HavsUtsikt: Om svensk havsforskning och havets resurser. - 1104-0513. ; 1
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Sjögräsängar är viktiga som barnkammare för många fiskarter, men är hotade av människan genom bland annat övergödning. Nu visar resultat från forskning utförd av svenska forskare i Sverige och i Östafrika på att även överfiske av stora rovfiskar skulle kunna ge negativa effekter på sjögräset. Detta visar hur viktigt det är att man inom förvaltningen använder sig av en kombination av åtgärder när sjögräsängarna ska räddas.
|
|
| 26. |
- Gullström, Martin, 1968, et al.
(författare)
-
Spatial patterns and environmental correlates in leaf-associated epifaunal assemblages of temperate seagrass (Zostera marina) meadows
- 2012
-
Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 159:2, s. 413-425
-
Tidskriftsartikel (refereegranskat)abstract
- We estimated and tested variability of seagrass leaf-associated epifaunal assemblages at a range of scales. Sampling was performed in 36 seagrass (Zostera marina) meadows within three regions along the Swedish west coast following a hierarchical design (samples separated by 10 s m, km or 100 km). Results showed strongest variability (43-81%) at the intermediate amongst-meadow (km) scale using biomass of functional categories, while considering taxa composition the within-meadow (10 s m) scale contributed most to variability (60%). Using functional categories, we found that embayment exposure and seagrass shoot density were the most important predictor variables explaining part of the variability in biomass of suspension feeders (bivalves and barnacles) and grazers. In contrast, variability in epifaunal taxa composition was predicted mainly by sediment chemistry, substratum coverage and geographical positioning. Our findings suggest that models to develop predictive power and mechanistic understanding should focus on variables and processes varying at small and intermediate scales rather than those varying at larger scales.
|
|
| 27. |
- Hernroth, Bodil, et al.
(författare)
-
Alteration of host-pathogen interactions in the wake of climate change - Increasing risk for shellfish associated infections
- 2018
-
Ingår i: Environmental Research. - : Elsevier BV. - 0013-9351 .- 1096-0953. ; 161, s. 425-438
-
Forskningsöversikt (refereegranskat)abstract
- © 2017 Elsevier Inc. The potential for climate-related spread of infectious diseases through marine systems has been highlighted in several reports. With this review we want to draw attention to less recognized mechanisms behind vector-borne transmission pathways to humans. We have focused on how the immune systems of edible marine shellfish, the blue mussels and Norway lobsters, are affected by climate related environmental stressors. Future ocean acidification (OA) and warming due to climate change constitute a gradually increasing persistent stress with negative trade-off for many organisms. In addition, the stress of recurrent hypoxia, inducing high levels of bioavailable manganese (Mn) is likely to increase in line with climate change. We summarized that OA, hypoxia and elevated levels of Mn did have an overall negative effect on immunity, in some cases also with synergistic effects. On the other hand, moderate increase in temperature seems to have a stimulating effect on antimicrobial activity and may in a future warming scenario counteract the negative effects. However, rising sea surface temperature and climate events causing high land run-off promote the abundance of naturally occurring pathogenic Vibrio and will in addition, bring enteric pathogens which are circulating in society into coastal waters. Moreover, the observed impairments of the immune defense enhance the persistence and occurrence of pathogens in shellfish. This may increase the risk for direct transmission of pathogens to consumers. It is thus essential that in the wake of climate change, sanitary control of coastal waters and seafood must recognize and adapt to the expected alteration of host-pathogen interactions.
|
|
| 28. |
- Hernroth, Bodil, 1951, et al.
(författare)
-
Bacteriostatic suppression in Norway lobster (Nephrops norvegicus) exposed to manganese or hypoxia under pressure of ocean acidification
- 2015
-
Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 159, s. 217-224
-
Tidskriftsartikel (refereegranskat)abstract
- Future ocean acidification (OA) and warming following climate change elicit pervasive stressors to the inhabitants of the sea. Previous experimental exposure to OA for 16 weeks at pH levels predicted for 2100 has shown to result in serious immune suppression of the Norway lobster, Nephrops norvegicus. The lobsters are currently affected by stressors such as periodical hypoxia inducing high levels of bioavailable manganese (Mn). Here, we aimed to investigate possible effects of interactions between OA and these stressors on total hemocyte counts (THCs) and on recovery of inoculated bacteria in the lobsters, measured as a proxy for bacteriostatic response. The effects were judged by following numbers of culturable Vibrio parahaemolyticus in hepatopancreas, 4 and 24 h post inoculation in lobsters kept in replicate tanks with six different treatments: either ambient (pCO2∼ 500 atm/pH ∼ 8.1 U) or CO2-manipulated seawater (OA;pCO2 ∼ 1550 atm/pH ∼ 7.6 U) for 8 weeks. During the last 2 weeks, additional stress of either hypoxia (∼23% oxygen saturation) or Mn (∼9 mg L−1) was added except in control treatments. Our results showed clear effect on bacteriostatic response in Norway lobsters exposed to these stressors. In lobsters kept in ambient seawater without additional stressors, the number of culturable bacteria in hepatopancreaswas reduced by ∼34%. In combined treatment of ambient seawater and hypoxia, the reduction was∼23%, while in the Mn-exposed animals, there was no reduction at all. This was also the case in all OA treatments where mean numbers of culturable V. parahaemolyticus tended to increase. In lobsters from ambient seawater with or without hypoxia, the THC was not significantly different as was also the case in OA without additional stressors. However, in OA treatments combined with either hypoxia or Mn, THC was reduced by ∼35%. While the reduction of culturable V. parahaemolyticus in lobsters was clearly affected by these stressors, we found no notable effects on growth, survival or hemolytic properties of the bacteria itself. Thus, we conclude that this predicted stress scenario is beneficial for the pathogen in its interaction with the host. As OA proceeds, it may force the health of the ecologically and economically important N. norvegicus to a tipping point if exposed to more short-term stressors such as the periodical events of hypoxia and Mn. This could impact lobster condition and biomass and may as well increase the risk for bacterial transmission to consumers.
|
|
| 29. |
|
|
| 30. |
- Hernroth, Bodil, 1951, et al.
(författare)
-
Impact of ocean acidification on antimicrobial activity in gills of the blue mussel (Mytilus edulis)
- 2016
-
Ingår i: Fish and Shellfish Immunology. - : Elsevier BV. - 1050-4648 .- 1095-9947. ; 55, s. 452-459
-
Tidskriftsartikel (refereegranskat)abstract
- Here, we aimed to investigate potential effects of ocean acidification on antimicrobial peptide (AMP) activity in the gills of Mytilus edulis, as gills are directly facing seawater and the changing pH (predicted to be reduced from ∼8.1 to ∼7.7 by 2100). The AMP activity of gill and haemocyte extracts was compared at pH 6.0, 7.7 and 8.1, with a radial diffusion assay against Escherichia coli. The activity of the gill extracts was not affected by pH, while it was significantly reduced with increasing pH in the haemocyte extracts. Gill extracts were also tested against different species of Vibrio (V. parahaemolyticus, V. tubiashii, V. splendidus, V. alginolyticus) at pH 7.7 and 8.1. The metabolic activity of the bacteria decreased by ∼65–90%, depending on species of bacteria, but was, as in the radial diffusion assay, not affected by pH. The results indicated that AMPs from gills are efficient in a broad pH-range. However, when mussels were pre-exposed for pH 7.7 for four month the gill extracts presented significantly lower inhibit of bacterial growth. A full in-depth proteome investigation of gill extracts, using LC-Orbitrap MS/MS technique, showed that among previously described AMPs from haemocytes of Mytilus, myticin A was found up-regulated in response to lipopolysaccharide, 3 h post injection. Sporadic occurrence of other immune related peptides/proteins also pointed to a rapid response (0.5–3 h p.i.). Altogether, our results indicate that the gills of blue mussels constitute an important first line defence adapted to act at the pH of seawater. The antimicrobial activity of the gills is however modulated when mussels are under the pressure of ocean acidification, which may give future advantages for invading pathogens.
|
|
| 31. |
- Hernroth, Bodil, 1951, et al.
(författare)
-
Manganese induced immune suppression of the lobster, Nephrops norvegicus
- 2004
-
Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 70:3, s. 223-231
-
Tidskriftsartikel (refereegranskat)abstract
- Manganese (Mn) is one of the most abundant elements on earth, particularly in the soft bottom sediments of the oceans. As a micronutrient Mn is essential in the metabolic processes of organisms. However, at high concentrations the metal becomes a neurotoxin with well-documented effects. As a consequence of euthrophication, manganese is released from bottom sediments of coastal areas and the Norway lobsters, Nephrops norvegicus, can experience high levels of bioavailable Mn2+. Here, we present the first report showing that Mn also affects several fundamental processes in the mobilisation and activation of immunoactive haemocytes. When N. norvegicus was exposed to a realistic [Mn2+] of 20 mg l(-1) for 10 days 24.1 mug ml(-1) was recorded in the haemolymph. At this concentration the total haemocyte count was reduced by ca. 60%. By using BrdU as a tracer for cell division, it was shown that the proliferation rate in the haematopoietic tissue did not increase, despite the haemocytepenia. A gene coding for a Runt-domain protein, known to be involved in maturation of immune active haemocytes in a variety of organisms, was identified also in haemocytes of N. norvegicus. The expression of this gene was >40% lower in the Mn-exposed lobsters as judged by using a c DNA probe and the in situ hybridisation technique. In response to non-self molecules, like lipopolysaccharide, (LPS), the granular haemocytes of arthropods are known to degranulate and thereby release and activate the prophenoloxidase, system, necessary for their immune defence. A degranulation assay, tested on isolated granular haemocytes, showed about 75% lower activity in the Mn-exposed lobsters than that for the unexposed. Furthermore, using an enzymatic assay, the activation per se of prophenoloxidase by LPS was found blocked in the Mn-exposed lobsters. Taken together, these results show that Mn exposure suppressiA fundamental immune mechanisms of Norway lobsters. This identifies a potential harm that also exists for other organisms and should be considered when increasing the distribution of bioavailable Mn, as has been done through recently introduced applications of the metal.
|
|
| 32. |
- Hernroth, Bodil, 1951, et al.
(författare)
-
Simulated climate change causes immune suppression and protein damage in the crustacean Nephrops norvegicus
- 2012
-
Ingår i: Fish & Shellfish Immunology. - : Elsevier BV. - 1050-4648 .- 1095-9947. ; 33:5, s. 1095-1101
-
Tidskriftsartikel (refereegranskat)abstract
- Rising atmospheric carbon dioxide concentration is causing global warming, which affects oceans by elevating water temperature and reducing pH. Crustaceans have been considered tolerant to ocean acidification because of their retained capacity to calcify during subnormal pH. However, we report here that significant immune suppression of the Norway lobster, Nephrops norvegicus, occurs after a 4-month exposure to ocean acidification (OA) at a level predicted for the year 2100 (hypercapnic seawater with a pH lowered by 0.4 units). Experiments carried out at different temperatures (5, 10, 12, 14, 16, and 18 °C) demonstrated that the temperature within this range alone did not affect lobster immune responses. In the OA-treatment, hemocyte numbers were reduced by almost 50% and the phagocytic capacity of the remaining hemocytes was inhibited by 60%. The reduction in hemocyte numbers was not due to increased apoptosis in hematopoetic tissue. Cellular responses to stress were investigated through evaluating advanced glycation end products (AGE) and lipid oxidation in lobster hepatopancreata, and OA-treatment was shown to significantly increase AGEs', indicating stress-induced protein alterations. Furthermore, the extracellular pH of lobster hemolymph was reduced by approximately 0.2 units in the OA-treatment group, indicating either limited pH compensation or buffering capacity. The negative effects of OA-treatment on the nephropidae immune response and tissue homeostasis were more pronounced at higher temperatures (12–18 °C versus 5 °C), which may potentially affect disease severity and spread. Our results signify that ocean acidification may have adverse effects on the physiology of lobsters, which previously had been overlooked in studies of basic parameters such as lobster growth or calcification.
|
|
| 33. |
|
|
| 34. |
- Holmes, Janet M, et al.
(författare)
-
The effects of the metal ions Mn2+ and Co2+ on muscle contraction in the Norway lobster, Nephrops norvegicus (L.)
- 1999
-
Ingår i: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology. - : Springer Science and Business Media LLC. - 0174-1578 .- 1432-136X. ; 169, s. 402-410
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of the metal ions manganese and cobalt on force production by the abdominal superficial flexor muscle of the Norway lobster, Nephrops norvegicus, have been studied in response to both neuronal stimulation and electrical field stimulation applied to an isolated neuromuscular preparation, and by selectively blocking synaptic transmission with Ivermectin. In response to both forms of stimulation, low concentrations of manganese added to the standard N. norvegicus saline increased the contractile force produced by the muscle, whereas higher concentrations of manganese inhibited both responses in a dose-dependent manner, until force was completely abolished at concentrations above 2.9 mM manganese. Cobalt ions produced similar effects, and no significant difference was found between the concentration of the two ions at 50% force inhibition (K-m) or between the two stimulation methods (manganese: 1.22 mM; cobalt: 1.29 mM, P = 0.86). This suggests that they have a similar mode of action, and a postsynaptic site of inhibition. These K-m values are considerably higher than the concentrations of these ions known to accumulate in the haemolymph of N. norvegicus under eutrophic conditions, and it therefore seems unlikely that accumulations of manganese or cobalt ions under such conditions would cause any significant inhibition of muscle contraction force.
|
|
| 35. |
- Jephson, Therese, et al.
(författare)
-
Trophic interactions in Zostera marina beds along the Swedish coast
- 2008
-
Ingår i: Marine Ecology - Progress Series. - : Inter-Research Science Center. - 1616-1599 .- 0171-8630. ; 369, s. 63-76
-
Tidskriftsartikel (refereegranskat)abstract
- We compared eelgrass Zostera marina communities in 3 regions in Sweden believed to be affected by eutrophication and overfishing, to determine whether bottom-up or top-down processes control the biomass of epiphytic macroalgae and grazers. Nitrogen and carbon isotope signatures were analyzed to explore the food webs and to identify the grazing species feeding on filamentous algae and/or eelgrass. Mixing model (IsoSource version 1.3.1) analysis of the isotope signatures indicated that the amphipods Gammarus locusta and Microdeutopus gryllotalpa fed primarily on filamentous algae and that only 2 small gastropod species consumed eelgrass. Moreover, the grass shrimp Palaemon elegans and F adspersus were ca. 1 trophic level above amphipods and algae, but according to the mixing model played different trophic roles in the different areas. The highest biomass of filamentous algae was found in the west coast beds housing grazers with the lowest biomass and mean size (predominantly G. locusta and M. gryllotalpa, 0.5 to 3 mm). In contrast, the Baltic Sea beds had low algal biomass, but the grazers (mostly G. locusta and Idotea baltica) had higher biomass and were significantly larger (mean size ca. 10 mm). An overall negative correlation was found between grazer biomass and biomass of filamentous algae. The significantly smaller grazers and absence of isopod grazers on the west coast may be due to substantial consumption by small predatory fish. This supports the suggestions that, in Swedish eelgrass beds, grazers are top-down controlled, and overexploitation. of large predators and eutrophication play an important role in the recent increases in algal biomass.
|
|
| 36. |
- Krång, Anna Sara, 1972, et al.
(författare)
-
The ability of the amphipod Corophium volutator (Pallas) to follow chemical signals from con-specifics
- 2004
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 310:2, s. 195-206
-
Tidskriftsartikel (refereegranskat)abstract
- The amphipod Corophium volutator (Pallas) is a tube-dwelling species that only occasionally leaves its burrow. Animals that do crawl on the sediment are mainly males, apparently in search of females. This study was designed to determine whether C volutator males and females release chemical signals that attract con-specifics, and if so, whether these signals are gender specific. Laboratory experiments were conducted on the over-wintering generation during their reproductive season, using a Y-maze choice test apparatus. The results show that C volutator females release chemical signals that attract males. In the field, the attractant may guide males in search of burrowed females. In addition, male odour tends to attract males, while females do not follow chemical signals from con-specifics. We thereby show, on gender-specific chemical attraction of this species. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 37. |
- Loo, Lars-Ove, 1954, et al.
(författare)
-
Suspension Feeding in Adult Nephrops Norvegicus (L) and Homarus Gammarus (L) (Decapoda)
- 1993
-
Ingår i: Neth J Sea Res. - 0077-7579. ; 31:3, s. 291-297
-
Tidskriftsartikel (refereegranskat)abstract
- Suspension feeding in adults of the Norway lobster Nephrops norvegicus (40-74 g) and the European lobster Homarus gammarus (280-350 g) was tested in experiments offering planktonic food items of different sizes from 200 to 600 mu m and measuring the clearing capacity. Both lobster species were found to effectively clear water of food particles comprising nauplii of the brine shrimp Artemia salina of about 600 mu m in size. These were reduced to 50% of the initial concentration within 5 h and to 90% within 12 h. When N. norvegicus was offered food particles averaging 200 mu m, a significant reduction in average size occurred, indicating that the minimum retention size is around 200 mu m. Fluorescently dyed Artemia salina were recovered in the stomach and intestine of lobsters proving that the filtered particles are passed to the digestive tract. Results from other experiments, using the blood pigment (haemocyanin) concentration as an index of nutritional state, indicated that the lobsters can get some nutritional advantage from suspension feeding. Suspension feeding in larger decapods has not been described previously, so the significance of this finding is discussed with respect to changes in behaviour and ecological role.
|
|
| 38. |
|
|
| 39. |
- Moksnes, Per-Olav, 1965, et al.
(författare)
-
Trophic cascades in a temperate seagrass community
- 2008
-
Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 117:5, s. 763-777
-
Tidskriftsartikel (refereegranskat)abstract
- We assessed the relative importance of bottom-up and top-down processes in structuring an eelgrass community in Sweden, a system impacted both by eutrophication and overfishing. Using artificial seagrass as substrate, we manipulated nutrient levels and predator abundance in a full-factorial cage-experiment. The results revealed a seagrass community dominated by strong top-down processes controlling the aggregate biomass of mesograzers and macroalgae. In the absence of predators the large amphipod Gammarus locusta became very abundant resulting in a leaf community with low biomass of algae and smaller mobile fauna. One enclosed gobid fish predator reduced the abundance of adult G. locusta by > 90%, causing a three to six times increase in the biomass of algae, smaller mesograzers and meiofauna. Numerous small predators in uncaged habitats reduced the biomass of G. locusta and other mesograzers by > 95% in comparison to the fish treatment, further increasing the biomass of epiphytic algae and meiofauna. Although water column nutrient enrichment caused a temporal bloom of the filamentous macroalgae Ulva spp., no significant nutrient-effects were found on the algal community at the end of the experiment. The only lasting nutrient-effect was a significant increase in the biomass of G. locusta, but only in the absence of ambient predators. These results demonstrate that mesograzers can respond to enhanced food supply, increase their biomass and control the algal growth when predation rates are low. However, in the assessed system, high predation rates appear to make mesograzers functionally extinct, causing a community-wide trophic cascade that promotes the growth of ephemeral algae. This top-down effect could penetrate down, despite a complex food-web because the interaction strength in the community was strongly skewed towards two functionally dominant algal and grazer species that were vulnerable to consumption. These results indicate that overexploitation of gadoid fish may be linked to increased macroalgal blooms and loss of eelgrass in the area through a trophic cascade affecting the abundance of mesograzers.
|
|
| 40. |
- Nyqvist, Anna, 1961, et al.
(författare)
-
Dynamics of Seagrass Meadows on the Swedish Skagerrak Coast
- 2009
-
Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:2, s. 85-88
-
Tidskriftsartikel (refereegranskat)abstract
- Seagrasses have declined in many places around the world, and the Swedish Skagerrak coast is no exception. Between the 1980s and 2000, the cover of eelgrass (Zostera marina L.) on the Swedish Skagerrak coast decreased about 60%. In the present study, the sites that were investigated in the 1980s and 2000 were revisited (1655 ha) in 2003 and 2004 to investigate long and short term temporal and spatial differences in eelgrass coverage. The distribution of eelgrass was mapped from a small boat using an aquascope and a GPS receiver. No variation in total (about 150 km) or regional (about 20 km) eelgrass cover was found between 2000 and 2004, but there were substantial changes (both losses and gains) in meadow size on a local (less than about 2 km) scale. The results have implications for management of shallow soft bottoms, particularly because it was shown that even though no eelgrass is found in a single survey in a specific area, there could be eelgrass growing there in the following years.
|
|
| 41. |
- Oweson, Carolina A. M., 1976, et al.
(författare)
-
Manganese induced apoptosis in haematopoietic cells of Nephrops norvegicus (L.)
- 2006
-
Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X. ; 77:3, s. 322-328
-
Tidskriftsartikel (refereegranskat)abstract
- Manganese (Mn) is highly abundant as MnO2 in marine sediments. During hypoxia in bottom waters, the reduced bioavailable fraction of manganese, Mn2+, increases. Thereby, Norway lobster, Nephrops norvegicus, can experience concentrations up to 1000 times normoxic levels. A previous study has shown that exposure to a realistic concentration of 20 mg l(-1) of Mn for 10 days reduced the number of circulating haemocytes in N. norvegicus significantly. Here we aimed to investigate if apoptosis contributes to the Mn-induced haemocytopenia, with the overall hypothesis that Mn induces apoptosis in a time and concentration dependent manner. N. norvegicus were exposed to Mn (0, 5, 10 and 20 mg l(-1)) for 5 and 10 days. After 5 days of exposure the total haemocyte counts were not affected. However, after 10 days there was a gradual decrease in cell numbers, reaching a reduction by 44% when the animals were exposed to 20 mg Mn l(-1). Apoptosis in cells, released from the haematopoietic tissue, was investigated by using TUNEL assay, which detects specific DNA strand breaks. The fraction of apoptotic cells gradually increased from 2.5% in un-exposed lobsters to 15% in those exposed to 20 mg l(-1) but there was no difference related to the exposure time. A gradual increase of apoptosis was further confirmed by electrophoretic DNA-ladder formation, however to a lower extent in lobsters exposed during 5 days. Cell viability, determined by metabolic activity and cell membrane integrity, was not reduced, indicating that apoptosis rather than necrosis caused reduced number of haemocytes. It was concluded that apoptosis seemed to increase already after 5 days of 5 mg l(-1) of Mn-exposure, although exposure for 10 days was required before it was reflected in the haemocyte numbers. Reduced numbers of haemocytes may increase the prevalence for infections in N. norvegicus in their natural habitat. (c) 2006 Elsevier B.V. All rights reserved.
|
|
| 42. |
- Persson, Malin, et al.
(författare)
-
Trophic role of the omnivorous grass shrimp Palaemon elegans in a Swedish eelgrass system
- 2008
-
Ingår i: Marine Ecology-Progress Series. ; 371, s. 203-212
-
Tidskriftsartikel (refereegranskat)abstract
- Algal grazers are thought to play a critical role in preventing overgrowth by ephemeral algae in seagrass beds. We studied the interaction between the omnivorous grass shrimp Palaemon elegans, the algal grazer Gammarus locusta and the filamentous green alga Ulva sp. (syn. Enteromorpha sp.) to assess whether the shrimp has a positive or negative effect on the growth of ephemeral algae in eelgrass beds on the Swedish west coast. Laboratory experiments demonstrated that P. elegans were effective predators on gammarids <8 mm total length (TL), as well as effective grazers of filamentous Ulva sp. The shrimp appeared to prefer gammarid prey over algae, and only consumed significant amounts of Ulva sp. when the gammarid prey was too large to be consumed efficiently. The total consumption of Ulva sp. was positively affected by shrimp when gammarid prey were >5 mm TL, but negatively affected when G. locusta was smaller. In a field cage experiment, enclosed P. elegans decreased the abundance of gammarids by on average 68%, causing a trophic cascade that increased the biomass of filamentous Ulva sp. 7-fold. These results suggest that P. elegans on the Swedish northwest coast feed mainly on amphipods, including the algal grazer G. locusta, resulting in a positive net trophic effect on the growth of filamentous Ulva sp. This study indicates that P. elegans may be an important link between overexploitation of cod in northwest Sweden and the recent increase of algal mats and loss of eelgrass in the area.
|
|
| 43. |
- Pihl, Leif, 1951, et al.
(författare)
-
Shift in fish assemblage structure due to loss of seagrass Zostera marina habitats in Sweden
- 2006
-
Ingår i: Estuarine Coastal and Shelf Science. - London : Elsevier BV. - 0272-7714 .- 1096-0015. ; 67:1-2, s. 123-132
-
Tidskriftsartikel (refereegranskat)abstract
- The areal extent of Zostera marina in the archipelago of the Swedish Skagerrak has decreased by 60% over two decades. To investigate the effects of Z. marina loss on the local fish assemblages, the fish fauna was compared between existing seagrass beds and sites where seagrass had vanished. A field study was carried out at four shallow locations in the outer archipelago of the coast in June 2004. Within each location two sites were sampled, one with an existing Z. marina bed and another where Z. marina had disappeared. Fish were sampled semi-quantitatively with a beach seine. Samples were taken during both day and night and captured fish were examined to species, enumerated and measured in the field, and released thereafter. The number of fish species was found to be significantly higher in Z. marina habitats compared to areas where seagrass was missing, and density and biomass of fish were generally lower in areas dominated by bare sediment compared to those in the seagrass habitats. Several species and groups of fishes (i.e., gadoids, labrids, syngnathids) were absent or occurred in low densities at sites where Z. marina was missing. For example, juvenile 0-group cod density was reduced by 96% at sites where Z. marina had disappeared. Such a reduction in recruitment of cod is in the same order of magnitude as the combined effect of seal predation and mortality due to by-catches in the eel fyke-net fishery estimated for the archipelago of the Swedish Skagerrak. Hence, the results clearly indicate a shift in the fish assemblage, including a loss of taxa at the family level as a result of degradation in habitat-forming vegetation. (c) 2005 Elsevier Ltd. All rights reserved.
|
|
| 44. |
- Riera, R, et al.
(författare)
-
Severe shifts of Zostera marina epifauna: Comparative study between 1997 and 2018 on the Swedish Skagerrak coast
- 2020
-
Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X. ; 158:111434
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction between bottom-up and top-down processes in coastal ecosystems has been scarcely studied so far. Temporal changes in trophic interactions of Zostera marina along the Swedish west coast are relatively well studied, with the exception of epifaunal communities. Epifauna was used as a model study to explore resource (bottom-up) or predator (top-down) regulated in a vegetated ecosystem. We conducted a 21-year comparative study (1997 and 2018) using epifauna of 19 Zostera marina meadows along the Swedish Skagerrak coast. Large changes were observed in the composition of small (0.2–1 mm) and large (> 1 mm) epifauna. In the small-sized epifauna, the nematode Southernia zosterae and harpacticoids showed an increase of 90% and a decrease of 50% of their abundances, respectively. In the large-sized epifauna, the polychaete Platynereis dumerilii and chironomid larvae were absent in 1997 but thrived in 2018 (> 2000 ind. m−2). Mesoherbivores (Idoteids and gammarids) were locally very abundant in 1997 but disappeared in 2018. An 83% decline of mytilids settling in Zostera marina leaves was observed. Our results showed that epifauna is predominantly top-down regulated. An in- tegrative framework of the study area is outlined to shed light on the causes and consequences of the en- vironmental shifts reported in Zostera meadows from the northern Skagerrak area throughout the last three decades.
|
|
| 45. |
- Svensson, Carl Johan, 1976, et al.
(författare)
-
Temporal mismatches in predator-herbivore abundance control algae blooms in nutrient-enriched seagrass ecosystems.
- 2012
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 471, s. 61-71
-
Tidskriftsartikel (refereegranskat)abstract
- Blooming filamentous algae recurrently overgrow macroalgae and seagrass in many coastal ecosystems, leading to potential losses in the functions and services these habitats provide. The seasonal reoccurrence of algal blooms is partly caused by excessive input of nutrients into coastal ecosystems. At the same time, overfishing of top predators has led to increased densities of smaller predators that reduce herbivore abundance. Managers of coastal ecosystems are in urgent need of information on how overfishing may act synergistically with eutrophication to promote algal blooms. In the present study, we model the interaction between the opportunistic filamentous algae Ulva spp. and the effective mesograzer (small invertebrate herbivore) Gammarus locusta L. under different nutrient regimes and predation rates by intermediate-size fish (4 to 12 cm). The aim is to assess how productivity, herbivory and predation interact to regulate seasonal algal growth under a range of scenarios, including temporal matching or mismatching between trophic groups. The model is parameterised with nutrient and demographic data from a seagrass ecosystem on the west coast of Sweden. Model simulations show that both nutrient level and herbivore abundance regulate seasonal algal biomass in the seagrass meadow. Their relative importance is dynamic and sensitive to the arrival times of herbivores in relation to the start of algal development in spring. Thus, herbivore presence and timing are crucial factors for the control of algal biomass, particularly during times when resource levels are ambient to slightly elevated. Simulations also show that it is mainly the predation rate and timing of predators, rather than food limitation, that limit herbivore abundance. As predation rates by invertebrates and smaller fish can be linked to the presence of larger and commercially targeted fish, overfishing may have similar effects to eutrophication in the seagrass ecosystems.
|
|
| 46. |
- Thormar, Jonas, et al.
(författare)
-
Eelgrass (Zostera marina) food web structure in different environmental settings.
- 2016
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- This study compares the structure of eelgrass (Zostera marina L.) meadows and associated food webs in two eelgrass habitats in Denmark, differing in exposure, connection to the open sea, nutrient enrichment and water transparency. Meadow structure strongly reflected the environmental conditions in each habitat. The eutrophicated, protected site had higher biomass of filamentous algae, lower eelgrass biomass and shoot density, longer and narrower leaves, and higher above to below ground biomass ratio compared to the less nutrient-enriched and more exposed site. The faunal community composition and food web structure also differed markedly between sites with the eutrophicated, enclosed site having higher biomass of consumers and less complex food web. These relationships resulted in a column shaped biomass distribution of the consumers at the eutrophicated site whereas the less nutrient-rich site showed a pyramidal biomass distribution of consumers coupled with a more diverse consumer community. The differences in meadow and food web structure of the two seagrass habitats, suggest how physical setting may shape ecosystem response and resilience to anthropogenic pressure. We encourage larger, replicated studies to further disentangle the effects of different environmental variables on seagrass food web structure.
|
|
