Carbon requirements of a population of the estuarine copepod Eurytemora affinis

Abstract-The bioavailability of Cd, Se, and Zn associated with detritus of different biological origins to the marine copepod Acartia spinicauda was examined under laboratory conditions using the radiotracer approach. Three types of detritus, from the macroalga Ulva lactuca, cell debris of the diatoms Thalassiosira weissflogii and Thalassiosira rotula derived after natural decomposition or extraction, and copepod fecal pellets, were examined. The assimilation of metals from the ingested natural phytoplankton assemblage was also experimentally quantified. The assimilation efficiencies (AEs) of metals in copepods fed with different types of detritus were 47-83% for Cd, 30-59% for Se, and 41-75% for Zn. These values were comparable to the AEs measured previously for copepods fed on living algal cells, indicating that metals associated with biogenic particles were directly available to marine copepods. Labeling time had no effect on the metal AEs in copepods fed on detritus derived from U. lactuca. The metal AEs were higher in copepods fed on the freshly prepared diatom debris than on naturally decomposing debris. Zn associated with fecal pellets was assimilated at comparable efficiencies to those associated with macroalgal and microalgal debris, but Cd and Se were assimilated at a lower efficiency when associated with fecal pellets. The AEs of Cd (84-94%) in copepods fed on the natural phytoplankton assemblage were the highest among all the experiments. There was no obvious effect of the metal distribution in the cytosol of the natural phytoplankton assemblage on the metal AE. The calculated elimination rates of the metals were independent of detritus type and were similar to previous studies. Our study indicated that detritus is a potential food source for marine copepods and the metals associated with the detritus can be efficiently used with a relatively high AE. Detritus may thus play an important role in the overall biogeochemical cycling of metals in the ocean.

Section: Results-mentioning

confidence: 99%

mentioning

confidence: 99%

The assimilation of detritus‐bound metals by the marine copepod Acartia spinicauda

Wang

2002

“…Lengths were transformed to body mass using length-mass regressions (Dumont et al 1975;Hernroth 1985) and assuming 5% carbon content of wet mass. Mesozooplankton productivity was estimated from measured abundance, body mass, and literature data on development time at 15uC (Heinle and Flemer 1975). Since the mesozooplankton community was dominated by copepods, all other groups were ignored in the calculations.…”

Section: Methodsmentioning

confidence: 99%

Efficiency of a phytoplankton‐based and a bacterial‐based food web in a pelagic marine system

Berglund

Müren

Båmstedt

et al. 2007

151

138

The food web efficiency in two contrasting food webs, one phytoplankton based and one bacteria based, was studied in a mesocosm experiment using seawater from the northern Baltic Sea. Organisms included in the experiment were bacteria, phytoplankton, protozoa, and mesozooplankton (copepods). A phytoplankton-based food web was generated by incubating at a high light level with the addition of nitrogen and phosphorus (NP). A bacteria-based food web was created by adding carbon, nitrogen, and phosphorus (CNP) and incubating at a lower light level. In the CNP treatment bacteria dominated the productivity (91%), while in the NP treatment phytoplankton were dominant producers (74%). The phytoplankton community in the NP treatment was dominated by autotrophic nanoflagellates. The food web efficiency, defined as mesozooplankton productivity per basal productivity (phytoplankton + bacteria), was 22% in the phytoplankton-based food web and 2% in the bacteria-based food web. This discrepancy could be explained by 1-2 extra trophic levels in the bacteria-based food web where carbon passed through flagellates and ciliates before reaching mesozooplankton, while in the phytoplankton-based food web there was a direct pathway from phytoplankton to mesozooplankton. The results were supported by stable isotope analysis of mesozooplankton. We propose that climate change, with increased precipitation and river runoff in the Baltic Sea, might favor a bacteria-based food web and thereby reduce pelagic productivity at higher trophic levels.

“…Both of these copepod species feed on both phytoplankton and microzooplankton (Heinle 1966;Heinle and Flemer 1975). Fish added to the ϩfish, ϩsediment, and ϩbenthos treatments were juvenile mummichogs (F. heteroclitus).…”

Section: Methodsmentioning

confidence: 99%

Variability in responses to nutrients and trace elements, and transmission of stressor effects through an estuarine food web

Breitburg¹,

Sanders²,

Gilmour³

et al. 1999

112

Aquatic systems are increasingly exposed to multiple stressors from anthropogenic sources. These stressors can vary in the consistency and magnitude of responses they elicit in biota and in how the presence of additional stressors modifies their effects. Understanding how the biological environment and temporal dynamics influence responses to stressors, and how stressors interact, is important to predicting their effects in the natural environment. We examined temporal variability in responses of an experimental estuarine food web to elevated trace elements and nutrients, as well as non-additive effects of the combination of these two stressors. Experiments were conducted four times during spring through autumn 1996 in 20 l-m 3 mesocosms. We measured a range of system-, population-, and individual-level parameters to quantify responses of phytoplankton, bacterioplankton, heterotrophic nanoflagellates, copepods, fish, and benthic invertebrates to trace element and nutrient additions.The response to trace element additions was more variable both temporally and among phytoplankton and higher trophic level taxa than was the response to nutrient additions. Most taxa increased, either significantly or showed a trend toward increasing, in response to nutrient additions in all four mesocosm runs. In contrast, the direction as well as the magnitude of responses to trace element additions varied considerably among taxa and experimental runs. Two distinct types of nutrientϫtrace element interactions were important. First, temporal dynamics of nutrient ratios appeared to affect the temporal pattern of toxicity of trace elements to phytoplankton. Second, in the June mesocosm run when trace element additions reduced production, abundance, or growth of many organisms, these reductions were often proportionately greater in nutrient addition tanks than where no nutrients were added. Our results suggest that considerable temporal and taxonomic variation in responses to trace element loadings are likely to be seen in field settings even under constant loadings to the system and that trace elements may mask the magnitude of the response to high nutrient loadings in eutrophic systems. More generally, the presence of multiple stressors may either increase or dampen the temporal and spatial variability seen in aquatic systems, depending on the interactions among stressors and the influence of background environmental conditions and sensitive species on the expression of stressor effects.Stressors vary considerably in the specificity of their effects; some stressors may affect nearly all organisms within AcknowledgmentsWe thank B. Albright, D. Butera, L. Cole, D. Connell, R. DeKorsey, T. Huber, A. Imirie, S. Sellner, J. Smallwood, M. Ward, M. Weinstein, T. Wiegner, and W. Yates for their help in running experiments and data analysis; S. Nixon, S. Grainger, and E. Buckley for suggestions on mesocosm design and unpublished data from their seagrass mesocosm experiments; M. Bundy for advice on copepod feeding strategies; E. Perry f...