Spatial patterns of oxygen states affect lake food web structure through the response of cold-water fish

Le résumé fourni par la source

Surface water warming and bottom water oxygen depletion, accelerated by global warming, limit the distribution of cold-water fish in the pelagic areas of temperate lakes. Surface warning is well known to cause drastic changes to food web structure by limiting the distribution of top predators. Hypoxic conditions that are spatially heterogeneous compared with water temperature can develop in temperate lakes, but knowledge of how these conditions affect the distribution of cold-water fish and food webs is lacking. We investigated the offshore distribution of cold-water fish (kokanee and rainbow trout) in a lake using a hydroacoustic system and environmental DNA. We focused on how their distributions were related to water temperatures and dissolved oxygen concentrations. We found that kokanee were concentrated in areas with relatively favorable dissolved oxygen concentrations during the summer, when their vertical distribution was strongly constrained by low oxygen concentrations and high temperatures. Zooplankton, their food resource in the pelagic zone, were distributed at relatively high density in areas with relatively few kokanee. Our finding suggests that hypoxic conditions and the spatial patterns thereof play critical roles in shaping the spatial structure of pelagic food webs as the climate warms.

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