Microplastic burden in Daphnia is aggravated by elevated temperatures.

Area of Science:

• Environmental Science
• Ecotoxicology
• Aquatic Biology

Background:

• Microplastic contamination is a growing threat to freshwater ecosystems.
• Filter-feeding zooplankton, such as Daphnia magna and Daphnia pulex, are particularly vulnerable.
• Understanding factors influencing microplastic ingestion is crucial for assessing ecological risk.

Purpose of the Study:

• To investigate the effects of food availability and temperature on microplastic ingestion by Daphnia.
• To analyze the physiological impact of microplastic exposure on these model organisms.
• To project potential microplastic burdens in natural habitats.

Main Methods:

• Experiments used Daphnia magna and Daphnia pulex exposed to polystyrene spheres (1 μm).
• Ingestion rates were measured under varying food concentrations and temperatures.
• Physiological state was assessed by measuring carbohydrate (glycogen) concentration.

Main Results:

• Microplastic ingestion rates significantly increased under low food conditions and high temperatures.
• Maximal microplastic enrichment within Daphnia reached 1160 times ambient concentration within one hour.
• Three-day exposure did not alter glycogen reserves beyond normal food/temperature effects.

Conclusions:

• Daphnia's feeding behavior, regulated by thoracic limb currents, drives increased microplastic uptake in adverse conditions.
• Warm temperatures and scarce food, typical of summer lake clear-water phases, will likely increase microplastic burdens in zooplankton.
• These findings highlight the vulnerability of freshwater filter-feeders to microplastic pollution under specific environmental scenarios.