| 1. |
- Azour, Farivar, et al.
(författare)
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Invasion rate and population characteristics of the round goby Neogobius melanostomus: effects of density and invasion history
- 2015
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 24:1, s. 41-52
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Tidskriftsartikel (refereegranskat)abstract
- Round goby Neogobius melanostomus is currently one of the most wide-ranging invasive fish species in Europe and North America. The present study demonstrates how the distribution of round goby has expanded from 2008 to 2013 at a rate of about 30 km yr(-1) along the Danish coastline in the western Baltic Sea. Further analyses showed that fish from an established high-density round goby population were slow-growing and displayed poorer condition (weight at age and hepatosomatic index) compared to fish sampled from recently invaded locations (i.e. at the forefront of the distribution range). The established population revealed a broad age distribution and a 1:1 gender ratio, while fish from a recently invaded site were primarily of intermediate ages with a male-biased gender ratio. Otolith analyses suggested that the oldest individuals from the recently invaded area experienced superior growth conditions only in the most recent years, suggesting immigration into the area as adults. Our results suggest that intraspecific competition for food may cause continued dispersal of the species and that population demographics likely relate to invasion history.
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| 2. |
- Bergström, Ann-Kristin, et al.
(författare)
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Phytoplankton responses to nitrogen and phosphorus enrichment in unproductive Swedish lakes along a gradient of atmospheric nitrogen deposition
- 2008
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 4, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- Lake sampling and in situ nutrient enrichment enclosure experiments with nitrogen (N) and phosphorus (P) were conducted in unproductive Swedish lakes along a gradient of increasing atmospheric N-deposition. The regional and seasonal patterns of nutrient limitation of phytoplankton were clearly related to the amounts of N-deposition and N-inputs the lakes received. In areas of low N-deposition in northern Sweden, N-limitation of phytoplankton was evident throughout the summer season due to high catchment N-retention and very low dissolved inorganic N (DIN) inputs during the early summer. High N-deposition in the south was accompanied by high lake DIN-concentrations during the early summer and subsequent P-limitation of phytoplankton. However, P-limitation did not persist over the summer and, as a consequence of a declining DIN-pool, the lakes switched to dual- and co-limitation by N and P, and then to N-limitation. Generally, the lakes were N-limited rather than P-limited during the summer. We conclude that N-limitation is probably a natural state of the unproductive lakes studied, but P-limitation of variable intensity and duration has been induced by elevated atmospheric N-deposition.
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| 3. |
- Clark, M. S., et al.
(författare)
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Delayed arm regeneration in the Antarctic brittle star Ophionotus victoriae
- 2007
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 1:1, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- We describe the levels of natural arm damage in the Antarctic brittle star Ophionotus victoriae and the rate of arm regeneration over the period of 1 yr, as measured in our aquarium facilities at Rothera Point, West Antarctic Peninsula. The natural incidence of arm damage in O. victoriae is high (97 % of individuals examined). The rate of regeneration was 0.44 mm wk(-1), which is slow, but within the range of data from temperate brittle stars and also in line with data from the literature showing a general trend of decreasing arm regeneration rate with temperature. The Q(10) for arm regeneration rate of 2.6 across brittle stars is within the expected biological range. However, O. victoriae arm regeneration experiences a lag phase of up to 5 mo before reproducible amounts of new tissue are produced. Such a long lag phase has not been documented for any other brittle star species and produces a range of Q(10) values from 3.6 (when compared to the slowest documented lag phase for a temperate brittle star) to exceptionally high Q(10) values of 14.9 and 15.4 (when either fastest or average regeneration times are considered for temperate brittle stars and this Antarctic species). This indicates that the initial process of arm regeneration in O. victoriae is either different to that of other brittle stars or it is dependent on factors other than the effects of temperature on enzyme-mediated biochemical reactions, such as gonadal cycles and seasonality.
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| 4. |
- Ejdung, Gunilla, et al.
(författare)
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Predation by crustaceans on native and non-native Baltic clams
- 2009
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Ingår i: Aquatic biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 6, s. 15-24
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Tidskriftsartikel (refereegranskat)abstract
- We studied the effect of crustacean predators on native/non-native Macoma balthica bivalves in aquarium experiments. North Sea M balthica (NS Macoma) were recently observed in the southern Baltic Sea. They differ genetically and in terms of morphology, behaviour and evolutionary history from Baltic Sea M balthica (BS Macoma), and this may affect predation pressure and community structure. We hypothesised that predators consume more of the prey they co-exist with. NS Macoma and BS Macoma were exposed to crustacean predators common in the North Sea (Carcinus maenas and Crangon crangon) and in the Baltic Sea (C. crangon and Saduria entomon). Contrary to our hypotheses, the North Sea predators ate more BS Macoma, and S. entomon ate more NS Macoma. The crush-limited C. maenas preyed more on globular BS Macoma, whereas S. entomon, which do not crush but pry open the bivalve shell, ate more NS Macoma, which have a lighter (thus probably thinner) shell than BS Macoma. When NS and BS Macoma were offered together, BS Crangon ate more NS Macoma. We also studied BS Crangon consumption of M. balthica to assess whether sizes offered fall within the size spectrum that C. crangon can eat. Small (20 to 40 mm long), medium (40 to 50 mm) and large (50 to 60 mm) C. crangon especially ate small M. balthica. Differences in shape, size and meat/shell weight ratio between the BS and NS Macoma partly explained the differences in the susceptibility to predation by native and non-native predators.
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| 5. |
- Ejdung, Gunilla, et al.
(författare)
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Uptake of diatoms in Baltic Sea macrozoobenthos during short-term exposure to severe and moderate hypoxia.
- 2008
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 3:1, s. 89-99
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Tidskriftsartikel (refereegranskat)abstract
- he effect of severe and moderate hypoxia on food uptake of benthic macrofauna was studied in the laboratory. The hypothesis was that low oxygen concentrations negatively affect feeding at oxygen levels that have little effect on the studied animals' survival. The bivalve Macoma balthica, the priapulid Halicryptus spinulosus, the amphipods Monoporeia affinis (subadult & juvenile) and Pontoporeia femorata (subadult) were offered the C-14-labelled diatom Skeletonema costatum in 0.8 to 10.6 mg O-2 l(-1). Feeding was measured as radioactivity uptake. Subadult amphipods were studied one species at a time (single) or together (mixed). Feeding changed in all amphipods at the lowest oxygen concentrations, but no effect was found for M. balthica and H. spinulosus. At the lowest concentration (0.8 mg O-2 l(-1)) feeding by subadult M affinis (single) was only 17% of the full oxygen saturation (10.6 mg O-2 l(-1)), and, at 1.6 mg O-2 l(-1), 14% of the feeding at 8.9 mg O-2 l(-1). Juvenile M affinis consumed more labelled algae at 3 Mg O-2 l(-1) than at higher oxygen concentrations. M balthica feeding was not affected. Little radioactivity uptake was registered for H. spinulosus at any oxygen concentration, showing that H. spinulosus is not a surface deposit feeder. The amphipods were the most sensitive to week-long oxygen deficiency. Survival decreased significantly in the lowest oxygen concentrations (0.8; 1.6 mg O-2 l(-1)). Of the subadult M. affinis 15 and 65%, respectively, survived, compared with 0 and 58% for P. femorata. Juvenile M. affinis mortality was high in all oxygen concentrations, whereas most M balthica and H. spinulosus survived.
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| 6. |
- Eriksson Wiklund, Ann-Kristin, et al.
(författare)
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Behavioural and physiological responses to pharmaceutical exposure in macroalgae and grazers from a Baltic Sea littoral community
- 2011
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 14:1, s. 29-39
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Tidskriftsartikel (refereegranskat)abstract
- Gammarus spp. and Fucus vesiculosus from the Baltic Sea littoral community were exposed to 3 concentrations of the pharmaceuticals ibuprofen and propranolol. Both physiological and behavioural parameters were measured to examine potential effects in the organisms. For Gammarus spp., respiration, feeding rate and activity with and without predator cues were measured, and gross production to respiration ratio (GP/R) and chlorophyll fluorescence were measured for F. vesiculosus. The results showed that propranolol decreased the activity related to movement, and Gammarus spp. could not compensate for the reduced movement when subjected to predator cues. The feeding rates of Gammarus spp. exposed to propranolol were more than 2 times higher at all concentrations compared to the control. Ibuprofen did not significantly affect any of the measured parameters of Gammarus spp. The GP/R was lower in algae exposed to propranolol. The effects of propranolol on both behaviour and physiology of Gammarus spp., in combination with the stress responses in the algae, might cause unexpected indirect and cascade effects which eventually could have implications at both community and ecosystem scales.
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| 7. |
- Hu, Marian, 1981
(författare)
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Metabolic energy demand and food utilization of the hydrothermal vent crab Xenograpsus testudinatus (Crustacea: Brachyura)
- 2012
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 15:1, s. 11-25
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Tidskriftsartikel (refereegranskat)abstract
- The hydrothermal vent crab Xenograpsus testudinatus (Crustacea: Brachyura) is endemic near Kueishan Island, Taiwan, where it lives in shallow waters close to the hydrothermal vents located in this area. X. testudinatus is adapted to a sulfur-rich and thus potentially toxic environment. It has established a specialized feeding strategy focusing on dead zooplankton organisms killed by the toxic discharges from the vents. During slack water, when there is little or no current, the crabs leave their crevices to feed on this ‘marine snow’. In the present study, we investigated the physiological aspects of nutritional adaptations of X. testudinatus. The crabs showed high digestive capacities of major digestive enzymes and particularly high activities for proteolytic enzymes. This feature can be regarded as an adaptation to irregular food availability. Furthermore, enzymes were stable at elevated temperatures, in a wide pH range, and in the presence of inorganic inhibitors like Cu2+, Fe2+, or Co2+. These enzyme properties can be considered essential to functioning in a vent habitat over long exposure times. Moreover, X. testudinatus is able to store significant amounts of lipid (50 to 60% of dry mass in the midgut gland), which may help to overcome periods of food scarcity. Fatty acid profiles revealed high amounts of saturated and monounsaturated components (mainly 16:0, 16:1(n-7), 18:1(n-9), and 18:1(n-7)). These findings reflect physiological adaptations and energetic strategies that enable this crab to exist in this extreme hydrothermal vent habitat. KEY WORDS: Hydrothermal vents · Crustacea · Xenograpsus testudinatus · Digestive enzymes · Fatty acids · Toxic environment · Heavy metals
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| 8. |
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| 9. |
- Jacoby, Charles A., et al.
(författare)
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Vertical distribution, behavior, chemical composition and metabolism of Stauroteuthis syrtensis (Octopoda : Cirrata) in the northwest Atlantic
- 2009
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 5:1, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- The cirrate octopod Stauroteuthis syrtensis is a mesopelagic species commonly collected in the North Atlantic. Individuals were observed at depths > 600 m and typically within 100 m of the bottom in three similar to 900 m deep canyons indenting the southern edge of Georges Bank. When first sighted, most octopods were floating passively with their webbed arms gathered into a small ball. When disturbed, they expanded their webs to form a 'balloon' shape, swam slowly by Sculling their fins, pulsed their webs like medusae and, in some cases, streamlined their arms and webs and moved away smoothly by rapidly sculling their fins. The bodies of 9 octopods comprised 92 to 95 % water, with tissue containing 9 to 22 % carbon (C) and 2 to 4 % nitrogen (N). These values were similar to those reported for medusae and ctenophores. Oxygen (O(2)) consumption rates of 4.6 to 25.8 mu mol 02 g(-1) C h(-1) were within ranges reported for medusae, ctenophores, and deep-water cephalopods. The stomachs of S. syrtensis, dissected immediately after capture, contained only the calanoid copepod Calan us finmarchicus. Calculations indicated that S. syrtensis need 1.3 to 30.1 ind. d(-1) of C. finmarchicus to meet their measured metabolic demand. Excretion rates (0.3 to 12.4 mu g NH(4)(+) g(-1) C h(-1) and 0.06 to 4.83 mu g PO(4)(3-) g(-1) C h(-1)) were at least an order of magnitude lower than rates reported for other octopods or gelatinous zooplankters. O:N ratios (11 to 366) suggested that S. syrtensis catabolized lipids, which may be supplied by C. finmarchicus. Vertical distribution, relatively torpid behavior and low metabolic rates characterized S. syrtensis as a benthopelagic and relatively passive predator on copepods.
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| 10. |
- Maire, O., et al.
(författare)
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Quantification of sediment reworking rates in bioturbation research: a review
- 2008
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 2:3, s. 219-238
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Tidskriftsartikel (refereegranskat)abstract
- This review lists and discusses the different methods currently available to assess sediment reworking by benthic infauna. Direct methods are used to estimate the amount of sediment transported by infauna at the sediment-water interface during a given period of time. Particle-tracer methods are used to quantify the vertical distribution of particle tracers within the sediment column. Tracers are classified based on their mode of introduction at the sediment-water interface (i.e. whether they occur naturally or are deliberately introduced at the onset of the experiment). The main characteristics of each method, including modelling aspects, are presented, and their respective advantages and drawbacks are outlined with a particular emphasis on their accuracy, spatial (i.e. both horizontal and vertical) and temporal resolutions. Direct and particle-tracer methods assess different components of sediment reworking. Selection of the most appropriate approach depends on the specific question(s) to be answered, as well as other factors, including the behaviour of the organisms studied, the spatial and temporal scales considered, and whether the experiments are carried out in situ or under controlled laboratory conditions.
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| 11. |
- Moran, Damian, et al.
(författare)
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Mortality structures population size characteristics of juvenile yellowtail kingfish Seriola lalandi reared at different densities
- 2011
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 11:3, s. 229-238
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Tidskriftsartikel (refereegranskat)abstract
- A study was undertaken to measure the effects of conspecific density on the growth, mortality and deformity rate of yellowtail kingfish Seriola lalandi Valenciennes during the first feeding period. Newly hatched larvae were stocked in replicate tanks at initial densities of 40, 60 and 100 ind. l(-1) until 30 d post-hatch (DPH). Live prey was administered at frequent intervals in an effort to maintain absolute prey density for all treatments. There was a negative relationship between conspecific density and mean individual length during the first half of the trial, which was attributed to food depletion between supplementary feedings at higher conspecific densities. The effect size (partial eta-squared) of conspecific density decreased considerably during the trial, to the point where the initial stocking density had no discernible effect on cohort growth or mortality rate. The apparent morphological deformity rate ranged from 17 to 32%, but did not differ between treatments. Jaw malformations were the most commonly observed deformity (12 to 30%). The weights of juveniles at the end of the trial were log-normally distributed, with some disproportionately large individuals skewing the weight distributions. There was substantial variation in mortality between and within treatments (74 to 97%), and the conspecific densities of each replicate at 30 DPH did not reflect the relative ordering of the initial treatments. Median individual weight was highly correlated with mortality and weight variance, and the positive skewness of populations decreased as mortality increased. Both trends indicated a strong population size-structuring mechanism. Given the controlled experimental conditions the size-structuring mechanism was not predation or cannibalism. Differential feeding success and an unidentified size-specific mortality agent are hypothesized to be the mechanisms by which mortality was able to strongly influence population size distributions.
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| 12. |
- Moran, Damian
(författare)
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Sampling effort required to obtain repeatable average size estimates of juvenile fish
- 2011
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 11:3, s. 239-242
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Tidskriftsartikel (refereegranskat)abstract
- Larval and juvenile fish cohorts often have skewed size distributions due to inter-individual variation in growth rates. A resampling analysis was used to investigate how much sampling effort is required to achieve repeatable average size estimates in populations of juvenile yellowtail kingfish Seriola lalandi Valenciennes. One hundred juveniles (30 d post-hatch) were measured for total length and wet weight from 9 cohorts reared in captivity. From an analysis of cohort size distribution the mean was determined to be a suitable measure of the average for length, while the median was best for weight. One thousand resamples of mean length and median weight were performed for each cohort data set, with sample sizes ranging from 2 to 100 individuals. The point at which increasing sample size resulted in only a negligible increase in precision (variance between resamples <0.1%) corresponded to n = 19 for mean length and n = 30 for median weight. Since yellowtail kingfish display a magnitude of size heterogeneity similar to other marine species with small pelagic larvae reared in captivity, the sample sizes determined in the present study can act as a general guideline for larval fish studies.
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| 13. |
- Nohren, E., et al.
(författare)
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Response of epibenthic faunal assemblages to varying vegetation structures and habitat patch size
- 2010
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 9:2, s. 139-148
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Tidskriftsartikel (refereegranskat)abstract
- Vegetation in shallow coastal marine systems increases habitat complexity and attracts epibenthic fauna. However, these areas are often subjected to dynamic changes such as eutrophication and sedimentation, which may lead to a reduction in patch size and/or a shift in species composition; although, few studies have been performed to show how these alterations affect the fauna assemblages. The aim of this study was to examine whether 4 structurally different types of vegetation, Fucus vesiculosus, Sargassum muticum, Zostera marina and filamentous algae, attract a unique assemblage of epibenthic fauna, compared to each other and to bare sand. Further, the importance of patch size (0.25, 0.5, 1.0 and 2.0 m(2)) on faunal species richness, biomass and assemblage composition within the different vegetation types was investigated. Experimental patches of vegetation were placed in a bay and samples were retrieved after 72 h. Pairwise tests (presence/absence data) showed that the faunal assemblages were significantly different between the vegetation types and also bare sand. Further, the 3 algal treatments (but not the seagrass Z. marina treatment) attracted higher species richness and a higher biomass of motile epibenthic fauna compared to the bare sand habitat. Among the 4 macrophytes, S. muticum, an invasive species found within the study area, and F. vesiculosus attracted the highest species richness and biomass, which suggests that the co-occurrence of these 2 species (in the absence of space or nutrient competition) results in an important habitat for epibenthic fauna. There was no overall effect of patch size, although within the F. vesiculosus and Z. marina treatments, patch size-dependent variations were found.
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| 14. |
- Samarra, F. I. P., et al.
(författare)
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Seasonal movements of killer whales between Iceland and Scotland
- 2015
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 24:1, s. 75-79
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the movements and distribution of killer whales Orcinus orca is important for evaluating the threats they face, as well as their impact as top predators in different ecosystems. Killer whales in the Northeast Atlantic are thought to follow specific prey stocks but their seasonal movements are still poorly understood. Here, we used recent killer whale photographic data collected in Iceland and Scotland to show that some individual whales repeatedly move between these locations. Unlike other killer whales that appear to follow the movements of particular herring stocks, the whales we studied appear to feed on the Icelandic summer-spawning herring stock in winter, and then move outside the summer distribution range of this herring stock. Based on these new photographic recaptures and previously published movements of killer whales between Iceland and Scotland, we infer that movements between both locations have been occurring for several years at least. Although based on only 7 identified individuals, our results provide the first evidence of regular seasonal movements between Iceland and Scotland, and suggest individual or group variability in the movement patterns of killer whales that prey on herring. Understanding killer whale movements will aid our understanding of prey specialization, the whales' potential impacts on local prey resources, and their susceptibility to fluctuations in the availability of different prey species.
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| 15. |
- Smith, B.C., et al.
(författare)
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Toxin profile change in vegetative cells and pellicle cysts of Alexandrium fundyense after gut passage in the eastern oyster Crassostrea virginica
- 2011
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Ingår i: Aquatic biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 13:2, s. 193-201
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Vegetative cells and pellicle cysts of the toxic dinoflagellate Alexandrium fundyense Balech were fed to the eastern oyster Crassostrea virginica Gmelin under controlled conditions. Para lytic shellfish toxins (PSTs) were measured in vegetative cells and pellicle cysts prior to feeding and directly after passage through the oyster alimentary canal and defecation as intact cells. Oysters fed with vegetative cells and those fed with pellicle cysts accumulated toxins. One experimental treatment tested for direct uptake of toxins from the water (oysters and A. fundyense cells were separated by a screen); PSTs were not accumulated from the water by the oysters. There were no significant changes in total, per-cell toxicity after passage through the oyster alimentary canal, suggesting limited transfer of toxins from intact cells to the oysters. However, there were statistically significant changes in the toxin composition of cells following gut passage. Vegetative cells and pellicle cysts from feces had increased amounts of saxitoxin (STX) and decreased amounts of gonyautoxin 4 (GTX4) per cell, compared to amounts prior to gut passage. Following gut passage, pellicle cysts showed better survival in the feces than vegetative cells, which is consistent with the view of pellicle-cyst formation as a successful survival strategy against adverse conditions.
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| 16. |
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| 17. |
- Svärd, C., et al.
(författare)
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Fasting affects the surface and diving metabolic rates of Steller sea lions Eumetopias jubatus
- 2009
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Ingår i: Aquatic Biology. - Oldenorf/Luhe : Inter-Research. - 1864-7782 .- 1864-7790. ; 8:1, s. 71-82
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Tidskriftsartikel (refereegranskat)abstract
- Changes in metabolic rates were measured in 3 captive female Steller sea lions Eumetopias jubatus that experienced fasts during summer and winter. We measured metabolic rates (via O2 consumption) before (MRs, surface) and after (DMR, dive + surface interval) the sea lions dove to 10–50 m depths. Measurements were obtained prior to and immediately after 9 to 10 d fasts, and during a 14 d recovery period. The sea lions lost significantly more body mass (Mb) during the winter fast (10.6%), compared with the summer (9.5%). Mass-corrected dive metabolic rate (cDMR = DMR × Mb–0.714) was not affected by dive depth or duration, but increased significantly following the winter fasts (13.5 ± 8.1%), but did not change during summer (–1.1 ± 3.2%). However, mass-corrected surface metabolic rate (cMRs) decreased significantly after both the summer (–16.4 ± 4.7%) and winter (–8.0 ± 9.0%) fasts. Consequently, the ratio between cDMR and cMRs was significantly higher in winter, suggestive of an increased thermal challenge and convective heat loss while diving. Increased cMRs following the fast indicated that digestion began during foraging and was not deferred, implying that access to ingested energy was of higher priority than optimizing diving ability. cDMR was elevated throughout the recovery period, independent of season, resulting in a 12% increase in foraging cost in winter and a 3% increase in summer. Our data suggest that Steller sea lions are more sensitive to changes in body condition due to food shortages in the winter compared with the summer.
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| 18. |
- Tiselius, Peter, 1958, et al.
(författare)
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High reproduction, but low biomass: mortality estimates of the copepod Acartia tonsa in a hyper-eutrophic estuary
- 2008
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 2:1, s. 93-103
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Tidskriftsartikel (refereegranskat)abstract
- Production, abundance and mortality of the copepod Acartia tonsa were studied for a period of 9 d in a hyper-eutrophic estuary, Mariager Fjord, Denmark. The estuary is characterised by oxygen-depleted and often sulphidic bottom water, and a relatively sparse mesozooplankton community with low species diversity. During the study, an intense phytoplankton bloom consisting mainly of the diatom Skeletonema costatum developed with chlorophyll a concentrations reaching 46 mu g l(-1). Egg production rate (EPR) in A. tonsa ranged from 30 to 65 eggs female(-1) d(-1), and egg hatching success was > 90 %, yet the abundance of copepods remained low (1 to 3 nauplii l(-1), 0.3 to 1.5 copepodites l(-1)). Calculated daily copepod mortality ranged from 18 % for nauplii, 16 % for Copepodite Stage C 1, up to 70 % for C2 and C3, then declining for older stages. The vertical distribution of copepodites in relation to the depth range of mussel beds suggests strong predation by suspension-feeding Mytilus edulis at depths of 5 to 10 m. Moreover, anoxia and the presence of sulphide in deep water, which prevented hatching of A. tonsa eggs and decreased the survivorship of older life stages sinking below 20 m depth, further contributed to the low copepod abundance.
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| 19. |
- Titelman, Josefin, et al.
(författare)
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Copepod feeding stimulates bacterioplankton activities in a low phosphorus system
- 2008
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Ingår i: Aquatic Biology. - : INTER-RESEARCH. - 1864-7782 .- 1864-7790. ; 2:2, s. 131-141
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Tidskriftsartikel (refereegranskat)abstract
- Zooplankton sloppy feeding releases high-quality dissolved organic matter, which is readily used by microbes. We hypothesized that in phosphorus (P) limited environments, released dissolved DNA may be a particularly important source of P for bacteria. In an incubation experiment with water from the Bothnian Bay, Sweden, we investigated the short-term effect of copepod feeding activity on bacterial production, DNA uptake and phosphatase activity. Consistent patterns in bacterial activity measures suggested that copepod feeding activity stimulated phosphatase activity, DNA uptake and production. The P taken up as dissolved DNA exceeded cellular P requirements. We speculate that bacterioplankton cells in the Bothnian Bay store excess P intracellularly during times of extensive sloppy feeding, which may then subsequently be utilized to prevent P limitation of growth.
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| 20. |
- Titelman, Josefin, 1973, et al.
(författare)
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Copepod feeding stimulates bacterioplankton in a low phosphorus system
- 2008
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 2:2, s. 131-141
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: Zooplankton sloppy feeding releases high-quality dissolved organic matter, which is readily used by microbes. We hypothesized that in phosphorus (P) limited environments, released dissolved DNA may be a particularly important source of P for bacteria. In an incubation experiment with water from the Bothnian Bay, Sweden, we investigated the short-term effect of copepod feeding activity on bacterial production, DNA uptake and phosphatase activity. Consistent patterns in bacterial activity measures suggested that copepod feeding activity stimulated phosphatase activity, DNA uptake and production. The P taken up as dissolved DNA exceeded cellular P requirements. We speculate that bacterioplankton cells in the Bothnian Bay store excess P intracellularly during times of extensive sloppy feeding, which may then subsequently be utilized to prevent P limitation of growth.
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| 21. |
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| 22. |
- Tjensvoll, Ingrid, et al.
(författare)
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Rapid respiratory responses of the deep-water sponge Geodia barretti exposed to suspended sediments
- 2013
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 19:1, s. 65-73
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Tidskriftsartikel (refereegranskat)abstract
- Sponges often dominate deep-water benthic faunal communities and can comprise up to 90% of the benthic biomass. Due to the large amount of water that they filter daily, sponges are an important link between benthic and pelagic ecosystems. Across the Tromso-flaket, Barents Sea, Norway, there are high biomasses of deep-water sponges. This area is also an important fishing ground, with fishing activity in some areas >27000 trawl hours yr(-1). Bottom trawling suspends large quantities of sediment into the water column, with measured concentrations up to 500 mg l(-1). This is the first study on the effects of suspended sediment exposure on deep-water sponges. In a laboratory experiment, Geodia barretti (Bowerbank 1858) (Class: Demospongiae) was exposed to 5 different sediment concentrations (0, 10, 50, 100 and 500 mg l(-1)). Respiration rates were measured before, during and after the exposure period. The results demonstrate that G. barretti physiologically shuts down when exposed to concentrations of 100 mg l(-1) (86% reduction in respiration), with thresholds of responses occurring between 10 to 50 mg l(-1). However, rapid recovery to initial respiration levels directly after the exposure indicates that G. barretti can cope with a single short exposure to elevated sediment concentrations. Given the high bottom-trawling frequency in Tromso-flaket, sponges may be frequently exposed to suspended sediments. Therefore, it is important that further investigations on the effects of suspended sediments on filter feeding organisms focus on the effects of repeated and long-term suspended sediment exposures to evaluate the overall ecological impacts.
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| 23. |
- Wallin, Anders, et al.
(författare)
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Benthic communities in relation to wave exposure and spatial = sitions on sublittoral boulders in the Baltic Sea
- 2011
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 12:2, s. 119-128
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Tidskriftsartikel (refereegranskat)abstract
- Boulders are an important substrate for Baltic Sea benthic communities. Although previous studies have examined benthic species on sublittoral boulders in the Baltic Sea, information on benthic assemblages and how they vary in relation to structuring factors is limited. The aim of the present study was to describe the benthic communities, including both algae and animal taxa, on sublittoral boulders in relation to spatial positions on the boulders (4 levels) and differences in wave exposure (2 levels). The multivariate results, including 29 algae and 25 animal taxa, from the field sampling showed a significant interaction between the 2 main factors. Changes in the biomass of both annual an perennial macroalgae as well as Mytilus edulis and Balanus improvisus, were found among different positions on wave-exposed boulders, a pattern which was less clear on boulders from sheltered sites, showing that water movement influences small-scale spatial patterns on sublittoral boulders. Apart from water movement, the physical factors substrate slope and light intensity were also associated with the small-scale patterns found in benthic communities. The difference in these factors may influence both settlement and post-settlement processes for both algae and animals, and possible mechanisms leading to the patterns found are discussed.
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| 24. |
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