Temperature mesocosm data

Predicting the effects of climate change requires understanding complex
interactions among multiple abiotic and biotic factors. By influencing key
interactions among host species, parasites can affect community and
ecosystem structuring. Yet, our understanding of how multiple parasites
and abiotic factors interact to alter ecosystem structure remains limited.
To empirically test the role of temperature variation and parasites in
shaping communities, we used a multigenerational mesocosm experiment
composed of four sympatric freshwater crustacean species (isopods and
amphipods) that share up to four parasite species. Mesocosms were assigned
to one of four different treatments with contrasting seasonal temperatures
(normal and elevated) and parasite exposure levels (continuous and
arrested (presence or absence of parasite larvae in mesocosm)). We found
that parasite exposure and water temperature had interactive effects on
the host community. Continuous exposure to parasites altered the community
structure and differences in water temperature altered species abundance.
The abundance of the amphipod Paracalliope fluviatilis decreased
substantially when experiencing continuous parasite exposure and elevated
water temperatures. Elevated temperatures also led to parasite-induced
mortality in another amphipod host, Paracorophium excavatum.
Contrastingly, isopod hosts were affected much less, suggesting increasing
temperatures in conjunction with higher parasite exposure might increase
their relative abundance in the community. Changes in invertebrate host
populations have implications for other species such as fish and birds
that consume crustaceans as well as having impacts on ecosystem processes,
such as aquatic primary production and nutrient cycling. In light of
climate change predictions, parasite exposure and rise in average
temperatures may have substantial impacts on communities and ecosystems,
altering ecosystem structure and dynamics.