Abundance and Isotopic Composition of Planktonic Microcrustaceans in a Central Amazon Floodplain Lake: Implications for the Trophic Dynamics of the Plankton Community (original) (raw)
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Stable isotope variability of meso-zooplankton along a gradient of dissolved organic carbon
Freshwater Biology, 2009
1. The d 13 C and d 15 N signatures of zooplankton vary with dissolved organic carbon (DOC), but inconsistent and limited taxonomic resolution of previous studies have masked differences that may exist among orders, genera or species and are attributable to dietary and ⁄ or habitat differences. Here we investigate differences among the isotopic signatures of five zooplankton taxa (Daphnia, Holopedium, large Calanoida, small Calanoida and Cyclopoida) in Precambrian shield lakes with a sixfold range of DOC concentration. 2. d 13 C signatures of Daphnia, small calanoids and large calanoids became more depleted with increasing lake DOC, whereas Holopedium and cyclopoid d 13 C became enriched with increasing DOC concentration. 3. The variability of d 13 C and d 15 N isotopic signatures among zooplankton groups was reduced in high-DOC, compared to low-DOC lakes, especially for d 13 C. Differences in d 13 C and POM-corrected d 15 N accounted for up to 33.7% and 19.5% of the variance, respectively, among lakes of varying DOC concentration. 4. The narrow range of signatures found in higher DOC lakes suggests that different taxa have similar food sources and ⁄ or habitats. In contrast, the wide range of signatures in low-DOC lakes suggests that different taxa are exploiting different food sources and ⁄ or habitats. Together with the variable trends in zooplankton isotopic signatures along our DOC gradient, these results suggest that food web dynamics within the zooplankton community of temperate lakes will change as climate and lake DOC concentrations change.
Journal of Plankton Research, 2015
The importance of allochthonous versus authochthonous carbon in the diet of zooplankters has been discussed at length in the recent literature, the more so for lakes with dissolved organic matter (DOM) concentrations between 3.5 and 25 mg L 21 . Here, we investigated the sources of carbon for Boeckella gracilipes (Copepoda, Calanoida) in three Patagonian shallow lakes that have different but relatively moderate DOM concentrations (,5 mg L 21 ). We linked their d 13 C values with parameters such as water color (absorbance 440 nm, abs440 ), dissolved organic carbon (DOC) concentrations and the ratio Color abs440 :Chlorophyll a (Chl a). We also determined the isotopic composition of seston and phytoplankton composition. Our results showed a direct relationship between the d 13 C values of B. gracilipes and seston (r 2 ¼ 0.64, P,0.001), and we demonstrated the importance of phytoplankton to B. gracilipes as its d 13 C signal was strongly related to the abundance of the mixotrophic nanoflagellate Chrysochromulina parva (r 2 ¼ 0.86, P , 0.001). We further found an inverse relationship between DOM and the ratio Color abs440 :Chl a and B. gracilipes d 13 C values (r 2 ¼ 0.67 and 0.56, respectively), which also supported the importance of authochthonous carbon for the copepod. We conclude that phytoplankton, particularly mixotrophic algae, rather than allochthonous carbon, supports the copepod B. gracilipes in shallow Patagonian lakes.
Isotopic analysis of the sources of organic carbon for zooplankton in
2015
Shallow high-latitude lakes and ponds are usually characterized by an oligotrophic water column overlying a biomass-rich, highly productive benthos. Their pelagic food webs often contain abundant zooplankton but the importance of benthic organic carbon versus seston as their food sources has been little explored. Our objectives were to measure the d 13 C and d 15 N isotopic signatures of pelagic and benthic particulate organic matter (POM) in shallow water bodies in northern Canada and to determine the relative transfer of this material to zooplankton and other aquatic invertebrates. Fluorescence analysis of colored dissolved organic matter (CDOM) indicated a relatively strong terrestrial carbon influence in five subarctic waterbodies whereas the CDOM in five arctic water columns contained mostly organic carbon of autochthonous origin. The isotopic signatures of planktonic POM and cohesive benthic microbial mats were distinctly different at all study sites, while non-cohesive microbial mats often overlapped in their d 13 C signals with the planktonic POM. Zooplankton isotopic signatures indicated a potential trophic link with different fractions of planktonic POM and the non-cohesive mats whereas the cohesive mats did not appear to be used as a major carbon source. The zooplankton signals differed among species, indicating selective use of resources and niche partitioning. Most zooplankton had d 13 C values that were intermediate between the values of putative food sources and that likely reflected selective feeding on components of the pelagic or benthic POM. The results emphasize the likely importance of benthic-pelagic coupling in tundra ecosystems, including for species that are traditionally considered pelagic and previously thought to be dependent only on phytoplankton as their food source.
Proceedings of the National Academy of Sciences, 2011
Cross-ecosystem subsidies to food webs can alter metabolic balances in the receiving (subsidized) system and free the food web, or particular consumers, from the energetic constraints of local primary production. Although cross-ecosystem subsidies between terrestrial and aquatic systems have been well recognized for benthic organisms in streams, rivers, and the littoral zones of lakes, terrestrial subsidies to pelagic consumers are more difficult to demonstrate and remain controversial. Here, we adopt a unique approach by using stable isotopes of H, C, and N to estimate terrestrial support to zooplankton in two contrasting lakes. Zooplankton (Holopedium, Daphnia, and Leptodiaptomus) are comprised of ≈20-40% of organic material of terrestrial origin. These estimates are as high as, or higher than, prior measures obtained by experimentally manipulating the inorganic 13 C content of these lakes to augment the small, natural contrast in 13 C between terrestrial and algal photosynthesis. Our study gives credence to a growing literature, which we review here, suggesting that significant terrestrial support of pelagic crustaceans (zooplankton) is widespread. allochthony | terrestrial subsidy E xternal inputs strongly influence ecosystems. Alterations of
Water, 2018
Interest in Stable Isotopes Analyses (SIA) is increasing in freshwater ecology to better clarify ecosystems' functioning. By measuring carbon and nitrogen isotopic signatures, food sources and organism trophic levels can be tracked, providing quantitative estimates of bi-dimensional niches. In order to describe some general patterns of carbon and nitrogen stable isotope signatures in lakes, we applied SIA to zooplankton community in five subalpine lakes sampled in spring and summer along a trophic gradient (from oligotrophy to hypereutrophy). Within zooplankton taxa, temporal variation in food sources and trophic levels were compared to find out taxon-specific patterns. Carbon and nitrogen isotopic signatures differed among the five lakes, reflecting depth, topography, and trophic status of the lakes. Carbon isotopic signatures varied more considerably in deeper and larger lakes (Mergozzo and Pusiano) than in a shallower and smaller lake (Lake Endine). Nitrogen isotopic signatures were generally more enriched in lakes Pusiano and Moro than in Lake Mergozzo, whereas in summer, they were depleted in all lakes. These observations indicate that zooplankton taxa specific trophic roles differed among lakes and in time.
Stable isotope analysis of the origins of zooplankton carbon in lakes of differing trophic state
Oecologia, 2000
Carbon stable isotope analysis was carried out on zooplankton from 24 United Kingdom lakes to examine the hypothesis that zooplankton dependence on allochthonous sources of organic carbon declines with increasing lake trophy. Stable isotope analysis was also carried out on particulate and dissolved organic matter (POM and DOM) and, in 11 of the lakes, of phytoplankton isolates. In 21 of the 24 lakes, the zooplankton were depleted in 13C relative to bulk POM, consistent with previous reports. δ13C for POM showed relatively little variation between lakes compared to high variation in values for DOM and phytoplankton. δ13C values for phytoplankton and POM converged with increasing lake trophy, consistent with the expected greater contribution of autochthonous production to the total organic matter pool in eutrophic lakes. The difference between δ13C for zooplankton and that for POM was also greatest in oligotrophic lakes and reduced in mesotrophic lakes, in accordance with the hypothesis that increasing lake trophic state leads to greater dependence of zooplankton on phytoplankton production. However, the difference increased again in hypertrophic lakes, where higher δ13C values for POM may have been due to greater inputs of 13C-enriched organic matter from the littoral zone. The very wide variation in phytoplankton δ13C between lakes of all trophic categories made it difficult to detect robust patterns in the variation in δ13C for zooplankton.
1997
and taxonomic structure of plankton community carbon biomass for the 0.2-2000 pm equivalent spherical diameter range were determined at the equator at 175"E in September 1990 and April 1994. Total biomass of the plankton community ranged from 1944 to 3448 mg C mM2. Phytoplankton, zooplankton and bacteria carbon biomasses were 604 1669 mg C m-*, 300-797 mg C m-', and 968-1200 mg C rne2, and the percentages were 31-54%, 15-26%, and 29-54%, respectively. Biomass of heterotrophic bacteria was always the largest fraction and Prochlorococcus biomass was second. Heterotrophic and autotrophic flagellates and dinoflagellates in the nanoplankton size range and copepods (adults and copepodites) in the mesoplankton range were also high. Relatively small biomass was observed in the microplankton size range. The differences in integrated biomass of plankton community for El Niiio type oligotrophic conditions of September 199G1993 and non-El Niiio type mesotrophic conditions of April 1994 were generally small compared with the interannual difference during 199&1993. However, the percentage of Prochlorococcus in phytoplankton carbon biomass was larger in non-El Niiio year. Biomasses of cyanobacteria, diatom, dinoflagellates, nauplii of copepods, and crustaceans other than copepods were larger in the non-El Niiio year. Primary production increased significantly from El Nirio to non-El Nirio years. Carbon flow through the plankton food chain was estimated using the plankton carbon biomass data, primary production measurements, and published empirical relationships. 0
Do Littoral Macrophytes Influence Crustacean Zooplankton Distribution
In a meso-eutrophic reservoir, cladoceran and copepod assemblages were characterised in two sampling sites: One located in the pelagic zone (site 1) and the other in the shallow littoral zone (site 2), the latter colonised by emergent macrophytes. Samples were collected biweekly from June to July 2001 and from May to July 2002 at the two sites. At site 1, crustacean zooplankton samples were obtained by vertical hauls using a Wisconsin type net of 64 mm mesh size. At site 2 several random samples were obtained using a van Dorn bottle. Those samples were pooled together and the total sample was sieved through a 64 mm mesh size. Macrophyte relative abundance for each species was visually estimated. Macrophyte community was composed of Glyceria declinata, Eleocharis palustris and Carex sp. A Mann-Whitney U-test was carried out to test for statistically significant differences between sites, for environmental parameters and crustacean zooplankton species densities. Alona rectangula, Alona costata, Alona quadrangularis and Chydorus sphaericus were only found in littoral samples. Daphnia longispina, Daphnia pulex, Ceriodaphnia pulchella, Bosmina longirostris, Diaphanosoma brachyurum, Copidodiaptomus numidicus, and Acanthocyclops robustus were found at both sites. However, Daphnia and Bosmina densities did not differ significantly between the pelagic and littoral sites. Ceriodaphnia, Diaphanosoma, and C. numidicus densities were significantly higher in the pelagic site, whereas A. robustus densities showed the opposite pattern.
Rapid Communications in Mass …, 2003
A literature survey of zooplankton stable isotope studies revealed inconsistencies between authors concerning (a) fixation and (b) allowance for gut clearance of zooplankton prior to d13C and d15N determinations. To address whether commonly used preservation techniques induce changes in stable isotope values, fresh lake zooplankton (control) were compared with preserved (ethanol, methanol, formaldehyde, gluteraldehyde, frozen and shock frozen) material. Differences of up to 1.1% for carbon and 1.5% for nitrogen isotopic signatures were found. Even freezing, the most frequently used method identified from the literature, caused significant changes compared with the control. We advocate the use of fresh material prepared immediately whenever possible, or complementary testing of the preservative method to be used. Larger organisms are routinely eviscerated, or specific tissues are dissected, and analysed for stable isotopes to reduce errors introduced via the gut contents. Yet zooplankton gut clearance is rarely performed: the gut content assumed to be negligible relative to organism mass. Experimental determinations of relative gut mass, from both original and compiled data, range from 1–26% for different zooplankton species. Using reported isotopic values of basal resources from natural systems, we calculated that, when analysing bulk zooplankton, inclusion of the gut mass may introduce substantial errors of >3%. Thus it appears prudent to perform the simple procedure of gut clearance, especially for copepod species.
Zooplankton and the Ocean Carbon Cycle
Marine zooplankton comprise a phylogenetically and functionally diverse assemblage of protistan and metazoan consumers that occupy multiple trophic levels in pelagic food webs. Within this complex network, carbon flows via alternative zooplankton pathways drive temporal and spatial variability in production-grazing coupling, nutrient cycling, export, and transfer efficiency to higher trophic levels. We explore current knowledge of the processing of zooplankton food ingestion by absorption, egestion, respiration, excre-tion, and growth (production) processes. On a global scale, carbon fluxes are reasonably constrained by the grazing impact of microzooplankton and the respiratory requirements of mesozooplankton but are sensitive to uncertainties in trophic structure. The relative importance, combined magnitude, and efficiency of export mechanisms (mucous feeding webs, fecal pellets, molts, carcasses, and vertical migrations) likewise reflect regional variability in community structure. Climate change is expected to broadly alter carbon cycling by zooplankton and to have direct impacts on key species.