In situ filtration responses of Daphnia galeata to changes in food quality

Abstract

In the stoichiometric study of phyto-zooplankton interactions, a controversy exists about how Daphnia species regulate their feeding rate when submitted to low-quality food (i.e. high dietary carbon:phosphorus [C:P] ratio). In this study, we gathered data over 3 years on in situ clearance rates of a Daphnia galeata population, by conducting grazing experiments from April 1998 to October 2000 in the Esch-sur-Su ˆre reservoir (Grand-Duchy of Luxembourg). Observed clearance rates (2.5-13.5 mL individual -1 day -1 , mean 7.0 mL individual -1 day -1 ) were correlated with population and environmental variables. Mean body size of Daphnia individuals was the best predictor of clearance rate (r 2 = 0.639), followed by water temperature (r 2 = 0.262) and P concentration in the seston (r 2 0.241). When combined with body size, seston C:P or nitrogen:P ratios provided the best predictive regression model of clearance rate (r 2 = 0.852-0.897). The clearance rate was always correlated negatively with P concentration in the food. Thus, Daphnia reacts to a decrease of food quality (i.e. higher C:P ratio) by an increase of its feeding rate. However, the filtration response to food quality was inhibited by high population density. We suggest that, when food quality is low and population density high, this inhibition may favour fitness of future conspecific generations. In conclusion, our results emphasize the effect of P availability on transfer rate of organic matter between lacustrian autotrophs and herbivores and pose questions about consequent effects on nutrient biogeochemical cycles.

Foraging behavior by Daphnia in stoichiometric gradients of food quality

“…Furthermore, our ingestion rate experiments show changes in foraging rate can operate very quickly. Our ingestion rate experiments are consistent with previous results from Sterner and Smith (1993) and Vandonk and Hessen (1993), but we must point out that Plath and Boersma (2001) and Darchambeau and Thys (2005) found that individual Daphnia also increased their ingestion rate when exposed to poor food quality. One explanation for the differences among ingestion studies could be accounted for by different acclimation procedures reflecting internal stimuli for foraging (e.g., Plath 1998).…”

“…One explanation for the differences among ingestion studies could be accounted for by different acclimation procedures reflecting internal stimuli for foraging (e.g., Plath 1998). Experiments have shown that individuals acclimated under poor food quality conditions respond by accelerating feeding when presented with high-quality food, whereas individuals not acclimated behave differently (Plath and Boersma 2001;Darchambeau and Thys 2005).…”

PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies

“…A complete review of the different expected responses has been presented by Mitra et al (2007). For instance, when confronted with poor food quality, zooplankton can increase their ingestion rate (Plath and Boersma, 2001;Darchambeau and Thys, 2005), or decrease it as the food can become deleterious (Flynn and Davidson, 1993). Accounting for the complexities of these different types of behavior has not been implemented within PISCES as this would require a model with flexible stoichiometry.…”

Daphnia's dilemma of adjusting carbon budgets when facing limitations by food quantity and the essential organic compound cholesterol

“…However, organisms may increase their fitness using this excess of C for other purposes, such as storage, structure and defence (Hessen and Anderson, 2008). Recent studies with phosphorus (P)-limited Daphnia showed adjustments in ingestion rate (Darchambeau and Thys, 2005) and assimilation efficiency of (excess) C and P (DeMott et al, 1998). Furthermore, daphnids may compensate for poor food quality by increasing C excretion (He and Wang, 2008) and respiration (Darchambeau et al, 2003;Jensen and Hessen, 2007), which depends on acclimation time (Lukas and Wacker, 2014).…”