The paradox high zooplankton biomass–low vegetal particulate organic matter in high turbidity zones: What way for energy transfer?. David, V.; Sautour, B.; Galois, R.; and Chardy, P. 333(2):202–218. Number: 2
The paradox high zooplankton biomass–low vegetal particulate organic matter in high turbidity zones: What way for energy transfer? [link]Paper  doi  abstract   bibtex   
Estuarine ecosystems are characterized by high zooplanktonic biomasses, essentially constituted by copepods and mysids whose nutritional requirements are mainly provided by phytoplankton, an easily available carbon form. The Gironde estuary is characterized by high turbidities which limit light penetration in the water column and therefore primary production. Consequently, primary production is low and its availability for higher trophic level is very limited. The main goal of this study was to characterize the total vegetal particulate organic matter (POM) in high turbidity zones of the Gironde estuary during summer (a critical period characterized by high heterotrophic bacterial degradation and high zooplanktonic biomasses) and to analyse its utilization by zooplankton, using prey/predator experiments and trophic biomarkers (fatty acids). The specific goals were to define (i) how vegetal POM was exploited by the different zooplanktonic groups (protozoa, copepods and mysids) and (ii) which alternative preys could be used when vegetal POM was not sufficient to ensure their nutritional requirements. Chlorophyll biomass was very low in the MTZ during summer 2002 (0.48±0.03 mg m−3). Total zooplankton grazing was low (19% d−1) probably due to a large contribution of detritus originating from terrestrial plants in vegetal POM compared to phytoplankton. The highest grazing pressure was exercised by the mysid Mesopodopsis slabberi due to its high abundances and by its almost entirely herbivorous diet (phytoplankton and small terrestrial detritus). Grazing rates (19.7±4.2 and 9.6 μgC cop−1 d−1 for juveniles and adults, respectively) seemed to be sufficient to satisfy their daily carbon requirement. Grazing rate of the copepod Eurytemora affinis (139 ngC cop−1 d−1) seemed to be insufficient to cover its nutritional requirements and the copepods probably needed to complete a great part of their diet from protozoa. Grazing rates of the mysid Neomysis integer (24.7±0.01 and 20.89±8.45 μgC cop−1 d−1 for juveniles and adults, respectively) were higher than those of M. slabberi when feeding only on phytoplankton. However, when other preys were introduced in its environment, N. integer only fed on the copepod E. affinis with a preference for nauplii. The study revealed the great importance of protozoa and bacteria in the trophic transfers between vegetal POM and zooplankton in the MTZ during summer, despite the low protozoa grazing pressure on vegetal POM (3.1%). The detritic food chain probably implies various trophic transfers with little direct relationships between vegetal POM and zooplankton.
@article{david_paradox_2006,
	title = {The paradox high zooplankton biomass–low vegetal particulate organic matter in high turbidity zones: What way for energy transfer?},
	volume = {333},
	issn = {0022-0981},
	url = {http://www.sciencedirect.com/science/article/pii/S0022098106000025},
	doi = {10.1016/j.jembe.2005.12.045},
	shorttitle = {The paradox high zooplankton biomass–low vegetal particulate organic matter in high turbidity zones},
	abstract = {Estuarine ecosystems are characterized by high zooplanktonic biomasses, essentially constituted by copepods and mysids whose nutritional requirements are mainly provided by phytoplankton, an easily available carbon form. The Gironde estuary is characterized by high turbidities which limit light penetration in the water column and therefore primary production. Consequently, primary production is low and its availability for higher trophic level is very limited. The main goal of this study was to characterize the total vegetal particulate organic matter ({POM}) in high turbidity zones of the Gironde estuary during summer (a critical period characterized by high heterotrophic bacterial degradation and high zooplanktonic biomasses) and to analyse its utilization by zooplankton, using prey/predator experiments and trophic biomarkers (fatty acids). The specific goals were to define (i) how vegetal {POM} was exploited by the different zooplanktonic groups (protozoa, copepods and mysids) and (ii) which alternative preys could be used when vegetal {POM} was not sufficient to ensure their nutritional requirements. Chlorophyll biomass was very low in the {MTZ} during summer 2002 (0.48±0.03 mg m−3). Total zooplankton grazing was low (19\% d−1) probably due to a large contribution of detritus originating from terrestrial plants in vegetal {POM} compared to phytoplankton. The highest grazing pressure was exercised by the mysid Mesopodopsis slabberi due to its high abundances and by its almost entirely herbivorous diet (phytoplankton and small terrestrial detritus). Grazing rates (19.7±4.2 and 9.6 μ{gC} cop−1 d−1 for juveniles and adults, respectively) seemed to be sufficient to satisfy their daily carbon requirement. Grazing rate of the copepod Eurytemora affinis (139 {ngC} cop−1 d−1) seemed to be insufficient to cover its nutritional requirements and the copepods probably needed to complete a great part of their diet from protozoa. Grazing rates of the mysid Neomysis integer (24.7±0.01 and 20.89±8.45 μ{gC} cop−1 d−1 for juveniles and adults, respectively) were higher than those of M. slabberi when feeding only on phytoplankton. However, when other preys were introduced in its environment, N. integer only fed on the copepod E. affinis with a preference for nauplii. The study revealed the great importance of protozoa and bacteria in the trophic transfers between vegetal {POM} and zooplankton in the {MTZ} during summer, despite the low protozoa grazing pressure on vegetal {POM} (3.1\%). The detritic food chain probably implies various trophic transfers with little direct relationships between vegetal {POM} and zooplankton.},
	pages = {202--218},
	number = {2},
	journaltitle = {Journal of Experimental Marine Biology and Ecology},
	shortjournal = {Journal of Experimental Marine Biology and Ecology},
	author = {David, Valérie and Sautour, Benoît and Galois, Robert and Chardy, Pierre},
	urldate = {2019-04-16},
	date = {2006-06-13},
	note = {Number: 2},
	keywords = {Zooplankton, Fatty acid biomarkers, Food chain, High turbidity zones, In situ experiments, Vegetal {POM}}
}
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