| 1. |
- Arnott, S. A., et al.
(författare)
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Selection of prey size and prey species by 1-group cod Gadus morhua: effects of satiation level and prey handling times
- 2000
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 198, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- We performed laboratory experiments to investigate feeding behaviour of 1-group Atlantic cod Gadus morhua and compared the results with stomach content records from wild 1-group cod feeding within a shallow bay on the west coast of Sweden. On the basis of the field observations, 3 prey species were investigated: juvenile shore crabs Carcinus maenas, brown shrimps Crangon crangon and 0-group plaice Pleuronectes platessa. When fed single species meals in the laboratory, satiation level was mostly independent of prey size, but cod consumed more plaice than shrimps and more shrimps than crabs. Once satiated on crabs, cod ate plaice if they were subsequently offered, but the reverse was not true. The time taken to ingest crabs was independent of the prey:cod (P:C) length ratio, cod length or stomach fullness, whereas plaice and shrimp ingestion times increased with P:C length ratio, and shrimp times also increased with stomach fullness. Consequently, the profitability of crabs increased up until the maximum edible size, whereas shrimp and plaice profitability peaked at P:C length ratios lower than the maximum edible sizes. For a given prey species, size selection in the field correlated closely with the size-dependent profitability relationships. Species selection had no apparent dependence upon handling-time profitability(, species-dependent satiation level or gastric evacuation rate. Additional factors of probable importance include prey evasiveness, prey abundance, habitat patchiness and abiotic factors such as prevailing light conditions.
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| 2. |
- Berntsson, Kent M., 1963, et al.
(författare)
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Rejection of unsuitable substrata as a potential driver of aggregated settlement in the barnacle Balanus improvisus
- 2004
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 275, s. 199-210
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Tidskriftsartikel (refereegranskat)abstract
- Many marine invertebrate larvae have the capacity to reject or accept settlement sites based on a broad range of cues. Species-specific settlement responses to different cues are often inferred from final settlement choice in the field. Little is known about species-specific larval behaviour in response to different cues and, in particular, how the behaviour is linked to final settlement. Rejection of unsuitable substrata may be an important driving force that leads to aggregated settlement patterns. This study examines rejection responses in relation to surface attractiveness for settlement under field and laboratory conditions in the barnacle Balanus improvisus. The attractiveness for settlement was manipulated by varying surface texture in combination with crude extract from conspecific adults. Active rejection behaviour was examined as a function of surface texture and conspecific pheromones in the field and then related to behavioural responses under static and flowing conditions in the laboratory. Recruitment was heavily reduced on substrata with ribbed microtexture compared to smooth substrata and unaffected by crude extract from conspecific adults. On average, 28% of the cyprids that encountered smooth settlement panels recruited. The proportion of cyprids recruiting on 2 microtextured substrata after encounter was 5 and 1% respectively. In behavioural experiments cyprids showed higher motion speed and dispersal rate on textured substrata, which indicated less exploratory behaviour than on smooth substrata, while an addition of conspecific extract increased intensities of surface exploration on all types of substrata. Flume experiments further demonstrated that cyprids are more prone to leave textured substrata and that the rejection rate was independent of conspecific extract. This work emphasises the role of larval behaviour as a potentially powerful mechanism determining final recruitment pattern. It is concluded that the choice of settlement site is an important factor in the settlement process of B. improvisus, and the results suggest that surface topography may be a stronger cue for settlement than chemical attraction by conspecific adults in this species. This study presents an example whereby rejection of unsuitable substrata leads to an increased larval pool on adjacent substrata that are suitable for settlement, and indicates that this process may drive aggregated settlement in the barnacle B. improvisus.
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| 3. |
- Björk, Mikael, et al.
(författare)
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In situ determination of PCB biodeposition by Mytilus edulis in a Baltic coastal ecosystem
- 2000
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Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599. ; 194, s. 193-201
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Tidskriftsartikel (refereegranskat)abstract
- Biodeposits of the blue mussel Mytilus edulis and pelagic and near-bed settling particulate matter were collected in situ over a 1 yr period in a coastal area of the Northern Baltic proper. The amounts of carbon and PCBs (polychlorinated biphenyls) in the collected biodeposits were compared to those in pelagic and near-bed settling material and rates of carbon and PCB biodeposition by mussels were estimated. The filter-feeding activity and subsequent release of faecal matter by the mussels increased gross sedimentation of carbon to benthos by 45 % if compared to areas with no mussels. By selectively feeding on particles rich in organic carbon the mussels also concentrated associated contaminants and thereby increased gross sedimentation of PCBs by 50 %. This suggests that mussel biodeposition will enhance the availability of PCBs to benthic deposit feeders living in or in the vicinity of mussel beds. Extrapolation of the experimental results to the total Swedish coastal zone of the Baltic proper indicates that mussel biodeposition is responsible for a significant part of PCB net sedimentation, i.e. 17 % or 96 kg yr(-1). Consequently, even when seen from a large geographical scale, mussels are important modifiers of PCB cycling by directing considerable amounts of PCBs towards the benthic food web and thereby influencing the retention time of these and probably many other contaminants in the coastal zone. It is also Likely that changes in mussel biomass, for example owing to shifts in primary production or salinity, will markedly affect the transport and fate of contaminants in the Baltic Sea.
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| 4. |
- Fistarol, Giovana, et al.
(författare)
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Allelopathic effect of Prymnesium parvum on a natural plankton community
- 2003
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 255, s. 115-125
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Tidskriftsartikel (refereegranskat)abstract
- The allelopathic effect of Prymnesium parvum (Prymnesiophyta), which produces toxins with haemolytic, ichthyotoxic and cytotoxic properties, was investigated on a natural plankton community. Under controlled conditions, 3 laboratory bioassays were performed by adding cell-free filtrate from a P. parvum culture into different size fractions (<150, <100 and 20 to 150 mum) of a natural Baltic Sea plankton community. The effect of P. parvum cell-free filtrate was determined by measuring chlorophyll a, cell numbers (phytoplankton, ciliates, bacteria), carbon (C-14) uptake by phytoplankton and the incorporation of H-3-leucine by bacteria. P. parvum cell-free filtrate affected the whole phytoplankton community, resulting in a decrease in both chlorophyll a and carbon uptake. Furthermore, the plankton groups present in the community exhibited different sensitivity to the cell-free filtrate. While growth of cyanobacteria and dinoflagellates was inhibited, that of diatoms and ciliates was not only completely suppressed, but no cells were present at the end of the experiment in the bottles with P. parvum filtrate. In all experiments, therefore, cyanobacteria and dinoflagellates were the most resistant groups, which led to their dominance in the treatments with filtrate compared to controls. Bacterial production was also negatively affected by P. parvum filtrate. The results show that compounds released by P. parvum induce changes in the plankton community structure, killing other members of the marine food-web, especially other phytoplankton (allelopathy), and suggest that secreted compounds of P. parvum are inhibitory to potential grazers (ciliates). It is proposed that allelopathy is an important process in the ecology of P. parvum.
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| 5. |
- Gibson, R. N., et al.
(författare)
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Ontogenetic changes in depth distribution of juvenile flatfishes in relation to predation risk and temperature on a shallow-water nursery ground
- 2002
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 229, s. 233-244
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Tidskriftsartikel (refereegranskat)abstract
- Stratified depth sampling was used to investigate the distributional changes of newly settled plaice Pleuronectes platessa and dabs Limanda limanda, and resident populations of shrimp Crangon crangon on a sandy beach. During the settlement period, the smallest newly settled plaice are found in deeper water than the larger fish that settled earlier. After settlement, plaice concentrate in water <1 m deep and there is a positive relationship between length and depth. Later in the year the fish gradually migrate into deeper water as they grow. Dabs settle later and in deeper water than plaice. Shrimp are concentrated in deeper water early in the year but migrate onshore in the summer, The movements of plaice are considered to be related to the predation risk caused by the shrimp and other predators in deeper water and to the higher temperatures in shallow water that promote faster growth. Once a size refuge from predators has been reached, the plaice move into deeper water. Intertidal pools probably serve as refuges for the smallest sizes of plaice because predators are less numerous in pools than in the sea. The use of shallow water by plaice represents the occupation of a niche which not only reduces predation and maximises growth, but may also greatly reduce competition for food in the earliest stages when densities are highest and competition with dabs is likely to be greatest.
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| 6. |
- Godhe, Anna, 1967, et al.
(författare)
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Oceanographic settings explain fluctuations in Dinophysis spp. and concentrations of diarrhetic shellfish toxin in the plankton community within a mussel farm area on the Swedish west coast
- 2002
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 240, s. 71-83
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Tidskriftsartikel (refereegranskat)abstract
- The influence of hydrographic, biological and meteorological variables on the abundance of Dinophysis spp. and the concentration of diarrhetic shellfish toxin (DST) in the plankton population were investigated in a mussel (Mytilus edulis) farm area on the Swedish west coast. This location provided an opportunity to simultaneously compare Dinophysis spp. cell numbers, concentration of DST in natural phytoplankton assemblages and toxicity of mussel tissues. Sampling was performed every other day from October 10 to November 5, 2000, and on each occasion, 5 randomly selected sites were sampled. During this period, 3 distinct water masses passed through the vicinity of the mussel farm. The second water mass, characterized by low salinity and nitrogen concentration, was probably advected into the area from surface waters in the nearby Skagerrak. This low salinity water also contained a high abundance of Dinophysis spp., and high concentrations of DST were recorded in the phytoplankton population. Multivariate analysis (projection to latent structures by means of partial least squares, PLS) determined that the principal variables influencing the concentration of DST in the plankton assemblage were the causative species (D. acuminata, D. acuta and D. norvegica) and salinity. The abundance of the 3 Dinophysis spp. was inversely correlated to salinity. A rapid increase in the toxicity of mussels in response to the high levels of DST was observed. The concentration of DST had doubled within 2 d of the appearance of Dinophysis spp. After 8 d, the water mass containing Dinophysis spp. was replaced and cell numbers again returned to low levels. The concentration of DST in the phytoplankton samples remained high for another 2 d after the number of Dinophysis spp. had declined and the toxicity of mussels continued to be high for the remainder of the study. Causes of the rapid intoxication versus slow detoxification of mussels are discussed. These results suggest that present monitoring programs are insufficient to provide early warning of toxic blooms to aquaculturists on the Swedish west coast.
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| 7. |
- Gremare, A., et al.
(författare)
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Feeding behaviour and functional response of Abra ovata and A-nitida compared by image analysis
- 2004
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 267, s. 195-208
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Tidskriftsartikel (refereegranskat)abstract
- An automated image analysis system was used to monitor sediment surface feeding activity of 2 bivalves (Abra ovata and A. nitida) inhabiting contrasting environments. A larger variety of feeding behaviours was recorded in A. nitida, whereas A. ovata mostly fed at the sediment surface. There were also clear differences in the behaviour of the 2 species during surface deposit feeding (i.e. a wider extension of the inhalant siphon in A. ovata, and the exhalant siphon being located below the sediment-water interface in A. ovata and above this interface in A. nitida). In A. nitida, increase in feeding activity resulted mostly from an increase in feeding intensity, and not from an increase in the amount of time devoted to feeding. In A. ovata, the most active bivalves tended to increase their activity mostly by increasing the amount of time devoted to feeding. This suggests that feeding intensity was limited in A. ovata but not in A. nitida. Food dilution and food addition experiments were carried out to assess the functional response in the 2 species. The results of the food dilution experiments were statistically insignificant due to high inter-individual variability. Food addition significantly affected feeding activity in A. ovata and A. nitida, although in different ways. In A. ovata, feeding activity was highest at intermediate food concentrations, and inhibited at the highest ones. In A. nitida, increased feeding activity was induced at higher concentrations than in A. ovata, and feeding activity was greatest at the highest food concentration. Such discrepancies in feeding behaviour and functional response in closely related species characterise the difficulty in delineating functional groups in benthic deposit-feeders.
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| 8. |
- Hansson, M., et al.
(författare)
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Effects of shrimp-trawling on abundance of benthic macrofauna in Gullmarsfjorden, Sweden
- 2000
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 198, s. 191-201
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Tidskriftsartikel (refereegranskat)abstract
- Hypotheses about effects of shrimp-trawling on large benthic macrofauna were tested in a manipulative experiment in Gullmarsfjorden, Sweden. The experiment lasted 1.5 yr and included 3 trawl sites and 3 control sites, each of which was sampled at 4 times before and 4 times after trawling was commenced (a total of 480 samples). Gear and intensities were chosen to approximate those before trawling was prohibited 6 yr before the experiment. The overall trend was that biomass and abundances of animals decreased as a consequence of trawling but few taxa differed significantly among treatments. The mean abundance of echinoderms, in particular the brittlestars Amphiura sp., decreased significantly and substantially after 7 to 12 mo of trawling. In general, however, changes in abundances of animals from one time of sampling to another, and from before to after trawling started, differed among sites. General models based on size and feeding strategy did not accurately predict differences among taxa in sensitivity to disturbances. Differences in overall impacts between this and previous experiments are discussed in terms of fishing intensity, natural variability and experimental design.
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| 9. |
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| 10. |
- Irigoien, X., et al.
(författare)
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Feeding of Calanus finmarchicus nauplii in the Irminger Sea
- 2003
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 262, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have shown that the passage from nauplius to copepodite is a key event in the population dynamics of Calan us finmarchicus. As a first step towards understanding if and how trophic interactions influence this event, we investigated the feeding of C. finmarchicus nauplii IV-VI in the Irminger Sea during spring and summer in a series of incubation experiments. Generally, feeding efficiencies were highest on large cells, whereas small flagellates were ingested at very low rates. Colonies of Phaeocystis sp. were not ingested. Among the larger cells, the diatoms Chaetoceros pelagicus and Tropodineis sp. and the ciliate Strombidium sp. were the main food sources. We observed a negative relationship between the percentage of diatoms in the food environment and the filtration rate on Strombidium sp. We therefore suggest that the combination of low feeding efficiency on small cells and the generally low concentrations of ciliates in oceanic waters explains why C, finmarchicus relies on phytoplankton blooms for recruitment from nauplius to the first copepodite stage.
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