Hot and sick? Impacts of warming and a parasite on the dominant zooplankter of Lake Baikal

Abstract

Climate warming impacts ecosystems through multiple interacting pathways, including via direct thermal responses of individual taxa and the combined responses of closely interacting species. In this study, we examined how warming and infection by an oomycete parasite (Saprolegnia) affect the dominant zooplankter of Russia's Lake Baikal, the endemic copepod Epischurella baikalensis. We used a combination of laboratory experiments, long-term monitoring data, and population modeling. Experiments showed a large difference in the thermal optima of host and parasite, with strong negative effects of warm temperatures on E. baikalensis survival and reproduction and a negative effect of Saprolegnia infection on survival. Saprolegnia infection had an unexpected positive effect on E. baikalensis reproductive output, which may be consistent with fecundity compensation by females exposed to the parasite. Long-term monitoring data suggested that Saprolegnia infections were most common during the warmest periods of the year. Population models, parameterized with experimental and literature data, correctly predicted the timing of Saprolegnia epizootics, but overestimated the negative effect of warming on E. baikalensis populations. Models suggest that diel vertical migration may allow E. baikalensis to escape the negative effects of increasing temperatures and parasitism and enable E. baikalensis to persist in the face of moderate warming of Lake Baikal. Our results contribute to understanding of how warming and parasitism interact to affect the pelagic ecosystems of cold lakes and oceans and how the consequences of these interacting stressors can vary seasonally, spatially, and interannually.

Temperature modifies trait-mediated infection outcomes in aDaphnia–fungal parasite system

“…Elevated temperature can have major impacts on host-parasite interactions and infection outcomes, shaping disease epidemics [1]. A growing body of work demonstrates that parasites often outperform their hosts at elevated temperatures, suggesting that a warmer world will be sicker [2][3][4]. However, this outcome is not universal (e.g.…”

Experimental warming and browning influence autumnal pelagic and benthic invertebrate biomass and community structure

“…Thus, a mismatch between increased resource availability of likely reduced nutritional quality (Diehl et al, 2022; Hixson & Arts, 2016) and metabolic costs may have driven the negative responses in copepods and rotifers with warming. However, this mechanism is speculative as we did not collect data on nutritional quality and can be related to other mechanisms, such as warming‐induced increases in zooplankton parasitism and disease (Ozersky et al, 2020; Shocket et al, 2018).…”

“…warming-induced increases in zooplankton parasitism and disease (Ozersky et al, 2020;Shocket et al, 2018).…”

Basal Parasitic Fungi in Marine Food Webs—A Mystery Yet to Unravel

“…Other representatives can be found in Table 1. Oomycota, as other zoosporic fungi, reproduce asexually by means of flagellated zoospores that are produced in zoosporangia [21,113,114], and, as members of the ARM clade, they have been recognized as endoparasites [115]. Despite similarities in life cycles, it is important to highlight the fundamental difference between oomycetes and zoosporic fungi-oomycetes are stramenopiles, a heterotrophic sister group of, e.g., brown algae and diatoms [104].…”