Short term fluctuating temperature alleviates Daphnia stoichiometric constraints

Abstract

In this study, we analysed how short term temperature fluctuation interacts with nutrient limitation in the vertical migrating Daphnia commutata. We hypothesize that short term (daily) temperature fluctuation will alleviate nutrient limitation. We carried out experiments analysing growth rates, phosphorus and RNA content of D. commutate grown under four different temperature regimes and two P-limited conditions. Our experiments showed that individuals grown under fluctuating temperature grew more than at the mean temperature. We estimated the expected sizes for the 15 °C treatment based on the Q10 and for the fluctuating temperature treatment. These expected sizes for both treatments resulted well below the observed ones. The P and RNA content of individuals grown at 10 °C were significantly higher than those at 20 °C, and when individuals grown at 10 °C were translocated to 20 °C they exerted an increased growth rate. Our results suggest that, under a regime of diel vertical migration, the temperature alternation would allow migrating organisms to alleviate the effect of severe nutrient limitation maintaining population growth. Under a scenario of global warming, where epilimnetic temperatures will increase, lake temperature will interact with nutrient limitation for consumers, but, organisms may be able to face these changes if they can still regularly move from a cold hypolimnion to a warmer epilimnion.

A common temperature dependence of nutritional demands in ectotherms

“…We observed that body C:P stoichiometry changes significantly with temperature, as indicated in previous work (Balseiro et al, 2021;Kendrick & Benstead, 2013;Woods et al, 2003) but in contrast to Ruiz et al (2020). Body C:P had a nonlinear U-shaped thermal response, with a minimum C:P located at the MaxTER C:P temperature.…”

“…Growth rate increases with increasing temperature and is in part responsible for the increase in ingestion, due to the extra demands for substrates (Hayes et al, 2015). Body C:P is expected to increase with temperature (Balseiro et al, 2021;Woods et al, 2003), while for GGEs decreasing, increasing and constant thermal responses were reported (Doi et al, 2010;Hagerty et al, 2014;Smith et al, 2021;Ye et al, 2019;Zheng et al, 2019). Based on these hypothesised mechanisms, we predict that ectotherm nutrient requirements change with temperature in a nonlinear fashion, as a response to nonlinear thermal reaction norms of metabolism and growth.…”