Daphnia fatty acid composition reflects that of their diet

Abstract

We conducted a series of experiments feeding Daphnia pulex nine different phytoplankton monocultures with widely varying fatty acid composition and nutritional values to test the extent to which Daphnia fatty acid composition was affected by diet. In general, Daphnia fatty acid composition matched that of their diet much more closely than it did the fatty acid composition of Daphnia consuming other diets. However, Daphnia had consistently less saturated fatty acids and more arachidonic acid than did their diet, and Daphnia consuming cyanobacteria had substantially less saturated fatty acids and more monounsaturated fatty acids than their diets. Daphnia that consumed cryptophytes, which are rich in v3 polyunsaturated fatty acids (PUFAs), had on average 47% 6 8% (61 SD) v3 PUFAs within their fatty acid pool, whereas Daphnia that consumed v3 PUFA-poor cyanophytes only had 6% 6 3% v3 PUFAs. The ratio of v3 to v6 fatty acids in Daphnia was also strongly dependent on diet, and averaged < 10 : 1, 2 : 1, and 1 : 1 for Daphnia that consumed cryptophytes, chlorophytes, and cyanophytes, respectively. Furthermore, the sum of C 20 and C 22 v3 and v6 fatty acids in Daphnia was highly correlated with that of their diet (r 2 5 0.94). These results suggest analyses of Daphnia fatty acid composition may be a powerful means of inferring diet in the field. These results also suggest the nutritional benefits of consuming v3-rich phytoplankton will transfer up the food web, making zooplankton both more efficient at converting phytoplankton biomass to their own biomass as well as much more nutritious for the zooplanktivorous fish that consume them.

Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels

“…In 3-level systems, high FCE was associated with a relative abundance of cryptomonads and diatoms, which dominated under low-light/high-nutrient conditions. These taxa have high concentrations of essential fatty acids (23) and are high-quality food for zooplankton (18). In our experiment, these taxa were also associated with low seston C/P.…”

“…The mechanisms accounting for these responses are difficult to discern because of potential covariation between different aspects of phytoplankton food quality (11,16,18,22,23). Based on our regressions, phytoplankton compositional food quality had the strongest effects on FCE (presumably because taxonomic identity is related to edibility and nutritional quality), but considering herbivore efficiency alone, stoichiometric quality had much stronger effects (Table S2).…”

“…The response of both carnivore efficiency and FCE to nutrients may represent a ''carryover effect'' across 3 trophic levels. When algal cells have high concentrations of P and/or essential fatty acids, zooplankton also may exhibit high concentrations of these resources and thus represent higher-quality food for fish, which have high P requirements for rapid growth (16,23,25). In laboratory experiments, differences in zooplankton P content, resulting from differences in phytoplankton P status, have been shown to affect fish growth (16).…”

Effects of cadmium and nitrogen on lipid composition of Chlorella vulgaris (Trebouxiophyceae, Chlorophyta)

“…In addition, Bigogno et al (2002) demonstrated that, in the green oleaginous alga Parietochloris incisa, changes in growth phase and conditions that resulted in TAG increases also resulted in a simultaneous decrease in the proportions of MGDG, DGDG, SQDG and PL, which agrees with the changes in AMPL at the lowest N treatment and Cd stress in this study. Fatty acid production by C. vulgaris exhibited a high degree of plasticity with changing culture conditions, with most fatty acids having long chain length groups of 16 and 18 carbon atoms (Brett et al, 2006;Petkov & Garcia, 2007;Villar-Argaiz et al, 2009). Pinto et al (2011) showed that SAFA and MUFA content of Gracilaria tenuistipitata increased with increasing Cd concentration, which is in agreement with our study showing increased SAFA and MUFA production by C. vulgaris in the presence of Cd.…”

Microzooplankton feeding behaviour: grazing on the microbial and the classical food web of African soda lakes

“…Phytoplankton communities in tropical saline-alkaline lakes are commonly dominated by filamentous cyanobacteria, which are mostly considered as low-quality food (e.g. Arnold, 1971) leading to low zooplankton population growth rates (Brett et al, 2006). Thus, B. plicatilis populations in L. Nakuru and L. Bogoria might be adapted to this condition by keeping feeding rates high and GTT low.…”