| 1. |
- Calliari, Danilo, 1969, et al.
(författare)
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Instantaneous salinity reductions affect the survival and feeding rates of the co-occurring copepods Acartia tonsa Dana and A-clausi Giesbrecht differently
- 2008
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 362:1, s. 18-25
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Tidskriftsartikel (refereegranskat)abstract
- Salinity variability at short time scales constitutes a severe restriction to marine life in coastal and estuarine ecosystems. In these environments zooplankters may experience rapid salinity variations due to diverse processes, yet lethal or sub-lethal responses to such changes have been scarcely studied. We assessed short-term (12 h) survival and time-integrated clearance (F; mL ind(-1) h(-1)) and ingestion rates (1, mu gC ind(-1) h(-1)) after 1, 2, 4, 8 and 12 h of two widespread and abundant coastal copepods, Acartia tonsa and A. clausi, subjected to instant salinity changes from 32 PSU to 26, 20,14, 8 and 4 PSU (A. tonsa) and from 32 to 26, 20 and 14 PSU (A. clausi). We expected that A. tonsa, which occur naturally in environments where sharp salinity gradients are common would tolerate wider salinity changes than A. clausi, which less frequently encounter sharp gradients in nature. For A. tonsa mortality for the extreme haline shock (change from 32 to 4 PSU) was 31%, whereas A. clausi reached 22% Mortality already at a change from 32 to 14 PSU; in comparison, mortality for A. tonsa at the 32/14 PSU treatment was only 3%. F and I decreased significantly at extreme treatments, and the total clearance in experimental bottles with salinity shocked animals (F-tot, mL h(-1)) was only 5% of rates measured in non-shocked control bottles for A. tonsa (32/4 PSU change) and 20% for A. clausi (32/14 PSU change); corresponding total ingestion (I-tot, mu gC h(-1)) represented 9.5% of that in control bottles for A. tonsa and 24% for A. clausi. In comparison, the 32/14 PSU treatment did not affect either clearance or ingestion rates in A. tonsa. Results suggest that in the field A. tonsa is not likely to suffer significant mortalities due to sudden salinity reductions in the Surrounding medium - except under extreme circumstances- while A. clausi cannot tolerate changes > 18 PSU. However, in both species feeding activity could be severely compromised by salinity reductions. The decreased feeding rate may have direct implications for processes ranging from energy acquisition at individual level to organic matter transfers at ecosystem level and thus deserves more attention in experimental studies and population modelling. (C) 2008 Elsevier B.V. All rights reserved.
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| 2. |
- Calliari, Danilo, 1969, et al.
(författare)
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Salinity modulates the energy balance and reproductive success of co-occurring copepods Acartia tonsa and A-clausi in different ways
- 2006
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 312, s. 177-188
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Tidskriftsartikel (refereegranskat)abstract
- We assessed metabolic balance, RNA content, and egg hatching success (EHS) in Acartia tonsa and A. clausi over a wide salinity range (2 to 33 and 16 to 33, respectively). For A. tonsa, the energy partitioning between ingestion, production and respiration was relatively constant with small differences in gross growth efficiency (GGE) and cost of growth (CG). In contrast, A. clausi exhibited significantly reduced ingestion and GGE, and highly elevated CG at salinities <= 20. In both species, RNA levels mirrored egg production. EHS was generally high in both species, but decreased by 80% for A. clausi at 16. These results contribute to the understanding of distribution patterns of both species along salinity gradients. The observed responses would allow the dominance of A. tonsa at low salinities, although its higher energetic requirement and feeding activity subject it to stronger predation pressure than competing A. clausi.
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| 3. |
- Juul-Pedersen, T., et al.
(författare)
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Sedimentation following the spring bloom in Disko Bay, West Greenland, with special emphasis on the role of copepods
- 2006
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 314, s. 239-255
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Tidskriftsartikel (refereegranskat)abstract
- The sedimentation of particulate organic material was investigated in Disko Bay, West Greenland, during June 2001. Post spring-bloom conditions were encountered, with seasonally decreasing phytoplankton biomass associated with the pycnocline. Calanus finmarchicus, C. glacialis, and C. hyperboreus dominated the zooplankton community, comprising up to 88% of the copepod biomass. Faecal pellet production by C. finmarchicus and C. glacialis was positively correlated to the available food (chlorophyll a > 10 mu m). Results from short-term sediment trap deployments (6 h) showed that particulate organic carbon (POC) sedimentation from the euphotic zone was, on average, 628 mg C m(-2) d(-1), with copepod faecal pellets contributing, on average, 29% of this amount. The faecal pellet contribution to the vertical sinking export of POC was equivalent to that of phytoplankton and amorphous detritus. Yet, on average, 35% of the copepod faecal pellet production was retained within the euphotic zone. The POC: PON (particulate organic nitrogen) ratio of the suspended material in the euphotic zone (8.1 +/- 0.4) was comparable to that of the material collected in the sediment traps just below the euphotic zone (8.0 +/- 0.9). In addition, the daily loss rates of POC and PON within each sampling depth were similar, and the carbon to nitrogen ratio in the sediment traps did not change with depth. These results indicate that the pelagic system had a low retention efficiency of nitrogen just after the spring bloom.
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| 4. |
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| 6. |
- Thor, Peter, 1965, et al.
(författare)
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Post-spring bloom community structure of pelagic copepods in the Disko Bay, Western Greenland
- 2005
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 27:4, s. 341-356
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Tidskriftsartikel (refereegranskat)abstract
- Community structure of pelagic copepods was investigated in the upper 200 m in the Disko Bay, Western Greenland, during the post-spring bloom period in June, 2001. This was the first study of the copepod community in West Greenland coastal waters sampled using smaller mesh sizes (50 mu m as opposed to 200 mu m). The mesozooplankton was dominated by copepods who constituted 82% of the total abundance and 95% of the total mesozooplankton biomass (> 50 mu m). Nauplii of Calanus, Pseudocalanus and Oithona dominated by number and the copepodites and adults were dominated by Oithona spp., Oncaea sp., Pseudocalanus sp., harpacticoids, Calanus finmarchicus, C. glacialis, and C. hyperboreus. Multivariate tests showed that the species/stage abundance composition of copepods changed significantly with depth. With one exception, all depth intervals showed unique significantly different compositions. Accordingly, the copepod community structure was influenced primarily by depth rather than by chlorophyll a concentration. Factors other than herbivorous grazing, such as omnivory, predator avoidance or association to marine snow aggregates of specific species, may have influenced the depth distribution of the total copepod community in the Disko Bay. Nevertheless, subsequent Pearson product moment correlations showed positive significant correlations between the vertical distribution of the three Calanus spp. and Pseudocalanus spp. and chlorophyll a concentrations, which points towards these species as prime components in the classic diatom-copepod food chain.
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| 7. |
- Bellas, Juan, et al.
(författare)
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Effects of selected PAHs on reproduction and survival of the calanoid copepod Acartia tonsa.
- 2007
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Ingår i: Ecotoxicology (London, England). - : Springer Science and Business Media LLC. - 0963-9292 .- 1573-3017. ; 16:6, s. 465-74
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Tidskriftsartikel (refereegranskat)abstract
- The effects of selected polycyclic aromatic hydrocarbons on the marine calanoid copepod Acartia tonsa were tested in laboratory short-term toxicity tests in order to facilitate risk assessment of those compounds to the marine pelagic environment. Photo-induced toxicity of pyrene was also investigated under naturally relevant UV light regimes. Lethal and sublethal effects on egg production rate, hatching and potential recruitment rate were evaluated after 48 h exposure to fluoranthene, phenanthrene and pyrene. The 48 h-median lethal concentrations (LC(50)) reducing survival by 50% were 594, 2,366 and >640 nM for fluoranthene, phenanthrene and pyrene, respectively, whilst lower concentrations induced different sublethal effects. Median effective concentrations (EC(50)) affecting the egg production rate and the recruitment rate were 433 and 385 (fluoranthene), 1,245 and 1,012 (phenanthrene) and 306 and 295 nM (pyrene), respectively. An increase in toxicity of pyrene was detected after incubation under UV light, resulting in LC(50) values of 201 nM (24 h) and 138 nM (48 h) and EC(50) values of 79 nM (egg production rate) and 41 nM (recruitment rate). Finally, a comparison between effective concentrations and worst-case environmental concentrations reported in literature indicated that pyrene may pose a threat to A. tonsa from exposure in the field, and that the risk of adverse effects is high for fluoranthene.
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| 8. |
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| 9. |
- Selander, Erik, 1973, et al.
(författare)
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Copepods induce paralytic shellfish toxin production in marine dinoflagellates
- 2006
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Ingår i: Proceedings of the Royal Society B-Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 273:1594, s. 1673-1680
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Tidskriftsartikel (refereegranskat)abstract
- Among the thousands of unicellular phytoplankton species described in the sea, some frequently occurring and bloom-forming marine dinoflagellates are known to produce the potent neurotoxins causing paralytic shellfish poisoning. The natural function of these toxins is not clear, although they have been hypothesized to act as a chemical defence towards grazers. Here, we show that waterborne cues from the copepod Acartia tonsa induce paralytic shellfish toxin (PST) production in the harmful algal bloom-forming dinoflagellate Alexandrium minutum. Induced A. minutum contained up to 2.5 times more toxins than controls and was more resistant to further copepod grazing. Ingestion of non-toxic alternative prey was not affected by the presence of induced A. minutum. The ability of A. minutum to sense and respond to the presence of grazers by increased PST production and increased resistance to grazing may facilitate the formation of harmful algal blooms in the sea.
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