| 1. |
- Rodriguez-Grana, Laura, 1969, et al.
(författare)
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Food web of a SW Atlantic shallow coastal lagoon: spatial environmental variability does not impose substantial changes in the trophic structure
- 2008
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 362, s. 69-83
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Tidskriftsartikel (refereegranskat)abstract
- We performed a detailed analysis of the food web structure of Laguna de Rocha, a temporally open coastal lagoon in the Southwest Atlantic, characterised by spatial gradients in salinity, nutrient levels and trophic status. Carbon and nitrogen stable isotopes of main producers, invertebrate and vertebrate consumers, and stomach contents of ichthyofauna were analysed seasonally at freshwater (north) and marine-influenced (south) sites to determine whether environmental differences induced changes in food web structure. Contribution of primary and secondary food sources and trophic linkages were assessed with the multisource-partitioning model IsoSource and an index that quantifies the contribution of each organism as food for the ecosystem. Isotopic analyses were performed for 10 primary organic matter sources (OM), 13 invertebrates and 9 fish species. Suspended and sediment OM constituted the most important primary sources, while direct consumption of macrophytes and macroalgae was marginal. The small invertebrates Neomysis americana, Nephtys fluviatilis, Pseudodiaptomus richardii and an amphipod were the most important intermediate consumers at both sites (except F richardii, which was present only in the north). Top predators were the fish species Micropogonias furnieri, Paralichthys orbygnianus and Hoplias malabaricus, and the maximum estimated trophic level (between 3.4 and 4.8) varied seasonally, but not between sites. Fish stomach content analyses largely confirmed results from the IsoSource mixing model. Overall results indicated that, despite environmental differences between sites, the structure of the biological assemblages and general trophic patterns were similar at both sites.
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| 2. |
- Rodriguez-Grana, Laura, 1969, et al.
(författare)
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Gender specific ageing and non-mendelian inheritance of oxidative damage in marine copepods
- 2010
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Ingår i: Marine Ecology Progress Series. - 0171-8630. ; 401, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Ageing in the marine pelagic copepod Acartia tonsa results in decreased feeding and production rates associated with an increase in the accumulation of protein oxidative damage, as predicted by the oxidative stress hypothesis. In laboratory experiments, we estimated sex-specific ageing effects on feeding and oxidative damage and on egg production rates of adult females. We also determined maternal effects on offspring by measuring egg hatching success and oxidative damage of nauplii from mothers of different ages. Males manifested more oxidative damage with age than females, providing an alternative explanation for the shorter life span in males. Older females produced fewer offspring, and nauplii with higher protein oxidative damage, than younger females. This study forms an empirical basis to link ageing, life span, sex differences and maternal fitness in animals that also reflects natural copepod population dynamics. Individual ageing processes and the resulting age structure in the population modulate mortality risk, parental effects on offspring performance, reproductive investment, and pelagic energy fluxes.
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| 3. |
- Calliari, Danilo, 1969, et al.
(författare)
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Feeding and reproduction in a small calanoid copepod: Acartia clausi can compensate quality with quantity
- 2005
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 298, s. 241-250
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Tidskriftsartikel (refereegranskat)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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| 4. |
- 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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| 7. |
- 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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| 8. |
- Calliari, Danilo, 1969, et al.
(författare)
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Summertime herbivory and egg production by Acartia tonsa at the Montevideo coast Rio de la Plata
- 2004
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Ingår i: Ophelia. - 0078-5326. ; 58:2, s. 115-128
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Tidskriftsartikel (refereegranskat)abstract
- We present the first data on copepod feeding and production in the Rio de la Plata, and discuss their correlation to the physical and biological environment. Sampling was performed at a protected area on the Montevideo coast where temperature, salinity and size fractionated chlorophyll a and phaeopigments were monitored weekly from January through February 2003, plus two additional observations in March and April. Acartia tonsa ingestion was measured by gut fluorescence, and gut evacuation rates, egg production and egg hatching success were estimated using standard methods. Food availability was moderate/high, but quality appeared low as reflected by chlorophyll a:phaeopigment ratios <1. Ingestion correlated with both chl-a and pha, suggesting that A. tonsa fed also on detrital matter. Egg production rates were low (1.4-7.5 eggs female(-1) d(-1)) - except for one exceptional record of ca. 88 eggs female(-1) d(-1) - indicating low productivity rates. Egg hatching success ranged from 30-94% and tended to increase during the study period. Overall results suggest that at the study site A. tonsa fed on both phytoplankton and detritus, and that its production was limited by food quality.
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