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- Calliari, Danilo, 1969, et al.
(author)
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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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In: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 362:1, s. 18-25
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Journal article (peer-reviewed)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.
(author)
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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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In: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 312, s. 177-188
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Journal article (peer-reviewed)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.
(author)
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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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In: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 314, s. 239-255
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Journal article (peer-reviewed)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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| 5. |
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| 6. |
- Thor, Peter, 1965, et al.
(author)
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Post-spring bloom community structure of pelagic copepods in the Disko Bay, Western Greenland
- 2005
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In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 27:4, s. 341-356
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Journal article (peer-reviewed)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. |
- Calliari, Danilo, 1969, et al.
(author)
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Feeding and reproduction in a small calanoid copepod: Acartia clausi can compensate quality with quantity
- 2005
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In: Marine Ecology-Progress Series. - 0171-8630. ; 298, s. 241-250
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Journal article (peer-reviewed)abstract
- We analyzed the feeding, egg production rate (EPR), and the egg hatching success (EHS) of resulting eggs of adult Acartia clausi subject to realistic food levels (100 mu g C l(-1)) of 7 algae. Feeding was maximum (ca. 20 ml ind.(-1) d(-1)) with Thalassiosira weissflogii and minimum (ca. 0 ml ind.(-1) d(-1)) with Dunaliella tertiolecta and Prymnesium parvum. EPR was highest with T weissflogii, Tetraselmis sp., Rhodomonas sp., and Ditylum brightwellii (21 to 26 eggs ind.(-1) d(-1)) and moderate with Prorocentrum minimum (15 eggs ind.(-1) d(-1)). EHS was highest in R minimum (84%), followed by Rhodomonas sp. (80%), D, brightwellii (60%), T weissflogii (52%) and Tetraselmis sp. (40%). Supplementary nutritional effects (higher EHS and gross growth efficiency) appeared when A. clausi fed on mixtures of algae with contrasting effects on EPR and EFIS (T weissflogii and P. minimum) offered as mixed suspensions, or alternating between unialgal suspensions on a 12:12 h basis. However, realized fecundity (RF) was fairly stable for most single and mixed diets (range 12.3 to 17.3 nauplii female(-1) d(-1)), with the exception of Tetraselmis sp. (8.9 nauplii female(-1) d(-1)). Such stable RF was attained by compensating low EFIS with enhanced feeding and EPR, and consequently lower population growth efficiency. That represents a strategy with a high cost in terms of metabolism and predation risk.
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| 9. |
- Leandro, S. M., et al.
(author)
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Growth and development of nauplii and copepodites of the estuarine copepod Acartia tonsa from southern Europe (Ria de Aveiro, Portugal) under saturating food conditions
- 2006
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In: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 150:1, s. 121-129
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Journal article (peer-reviewed)abstract
- A temperature-dependent growth model is presented for nauplii and copepodites of the estuarine calanoid copepod Acartia tonsa from southern Europe (Portugal). Development was followed from egg to adult in the laboratory at four temperatures (10, 15, 18 and 22 degrees C) and under saturating food conditions (> 1,000 mu g C l(-1)). Development times versus incubation temperature were fitted to a Belehradek's function, showing that development times decreased with increasing incubation temperature: at 10 degrees C, A. tonsa need 40.3 days to reach adult stage, decreasing to 8.9 days when reared at 22 degrees C. ANCOVA (homogeneity of slopes) showed that temperature (P < 0.001) and growth phase (P < 0.01) had a significant effect on the growth rate. Over the range of temperatures tested in this study, highest weight-specific growth rates were found during naupliar development (NI-NVI) and varied from 0.185 day(-1) (10 degrees C) to 0.880 day(-1) (22 degrees C) with a Q (10) equal to 3.66. During copepodite growth (CI-CV), the weight-specific growth rates ranged from 0.125 day(-1) (10 degrees C) to 0.488 day(-1) (22 degrees C) with a Q (10) equal to 3.12. The weight-specific growth rates (g) followed temperature (T) by a linear relationship and described as ln g=-2.962+0.130 T (r(2)=0.99, P < 0.001) for naupliar stages and ln g=-3.134+0.114T (r(2)=0.97, P < 0.001) for copepodite stages. By comparing in situ growth rates (juvenile growth and fecundity) for A. tonsa taken from the literature with the temperature-dependent growth model defined here we suggest that the adult females of A. tonsa are more frequently food limited than juveniles.
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| 10. |
- Leandro, S. M., et al.
(author)
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Temperature-dependent development and somatic growth in two allopatric populations of Acartia clausi (Copepoda : Calanoida)
- 2006
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In: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 322, s. 189-197
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Journal article (peer-reviewed)abstract
- This study compares the effect of temperature on the post-embryonic development time and weight-specific growth rate in 2 populations of Acartia clausi from different biogeographic areas (northern and southern Europe). Development was followed from nauplius 1 to adult at 3 temperatures (10, 15 and 18 degrees C) at saturating food conditions. The relationship between development time and temperature was established by fitting Belehradek's function. The northern population had a shorter generation time at all temperatures. At 10 degrees C, the development time was estimated to be 33.9 and 36.4 d decreasing to 16.3 and 17.4 d at 18 degrees C for the northern and southern populations, respectively. Prosome length decreased with temperature, and the southern population had longer individuals at all temperatures. ANCOVA revealed a significant (p < 0.001) positive effect of temperature on the growth rates, and nauplii grew faster than copepodites (except at 18 degrees C in the southern population and 20 degrees C in the northern population). Significant differences between populations were noted during larval growth, with nauplii from the north growing faster at high temperatures (18 degrees C). The results indicate that the 2 A. clausi allopatric populations subjected to different temperature regimes have different temperature responses, in particular at high temperatures.
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