Warming pushes invasive freshwater mysids toward algae
Lab experiments found higher temperatures shifted an invasive freshwater crustacean from animal prey toward algae, with possible food-web effects.
By Lucas Ferreira · Science & Environment Writer
3 min read
Warmer water can change what an invasive freshwater crustacean eats, according to a study published in Limnology and Oceanography Letters. The finding matters because a shift in diet could change the animal’s role in lake and river food webs, the HUN-REN Centre for Ecological Research said.
The research focused on Limnomysis benedeni, a Ponto-Caspian mysid that has spread through freshwater systems in Central Europe, according to the HUN-REN Centre. The species can become abundant and feeds as an omnivore, consuming both microscopic algae and small animal prey.
Researchers at the Institute of Aquatic Ecology at the HUN-REN Centre for Ecological Research in Budapest tested how temperature affected the mysid’s feeding choices. The team offered the crustaceans an algal food source, Cryptomonas sp., together with several animal prey types: the ciliate Coleps sp., the rotifer Brachionus calyciflorus and juvenile Daphnia magna.
The experiments used three temperatures: 16°C, 23°C and 30°C. According to the research team, those levels represent typical and episodically high growing-season conditions in regional shallow lakes.
Diet shifted as water warmed
As temperatures rose, the mysids consumed a higher share of algae compared with animal prey, the study found. The authors reported that the change reflected both lower feeding on animal prey and, in some prey combinations, greater algal intake.
The effect was clearest when larger zooplankton were available, including juvenile Daphnia magna and Brachionus calyciflorus, according to the study. The researchers said that pattern fits with the idea that larger prey become more costly to capture and handle at higher temperatures.
The study did not find a consistent rise in total carbon intake as the water warmed. The authors interpreted that as a change in how feeding was distributed between food types, rather than a broad increase in overall consumption.
Lead author Varsha Rani said the results indicate that warming can alter the trophic role of invasive consumers. In the study’s interpretation, a species that acts partly as a predator under cooler conditions may act more like a competitor with some of its animal prey when temperatures rise.
Possible effects for plankton communities
The HUN-REN Centre said the findings could apply beyond this one mysid because many aquatic invaders are omnivorous. If their diets change with temperature, their effects on plankton communities may also vary across seasons and during warmer periods.
The authors also linked the results to future climate conditions. According to the HUN-REN Centre, more frequent heat waves and warmer winters could extend or intensify the seasonal influence of invasive omnivores on freshwater plankton.
The team said a key feature of the work was its use of multiple live prey combinations, rather than a single food source. That design allowed the researchers to test feeding choices under conditions closer to natural plankton food webs.
The study was conducted by Rani, Csaba F. Vad, Zsófia Horváth, Károly Pálffy, Péter Borza and Pavel Kratina. The paper is titled “Temperature-driven diet shift in an invasive omnivorous crustacean feeding on plankton,” with DOI 10.1002/lol2.70153.
This story draws on original reporting from Phys.org.