Temperature Affects the Biological Control of Dinoflagellates by the Generalist Parasitoid .

The increase in emerging harmful algal blooms in the last decades has led to an extensive concern in understanding the mechanisms behind these events. In this paper, we assessed the growth of two blooming dinoflagellates ( and ) and their susceptibility to infection by the generalist parasitoid under a temperature gradient. The growth of the two dinoflagellates differed across a range of temperatures representative of the Penzé Estuary (13 to 22 °C) in early summer. growth increased across this range and was the highest at 19 and 22 °C, whereas growth was maximal at intermediate temperatures (15-18 °C). Interestingly, the effect of temperature on the parasitoid infectivity changed depending on which host dinoflagellate was infected with the dinoflagellate responses to temperature following a positive trend in (higher infections at 20-22 °C) and a unimodal trend in (higher infections at 18 °C). Low temperatures negatively affected parasitoid infections in both hosts (i.e., "thermal refuge"). These results demonstrate how temperature shifts may not only affect bloom development in microalgal species but also their control by parasitoids.