Quantifying diet-borne metal uptake in Gammarus pulex using stable isotope tracers

Area of Science:

• Environmental Science
• Ecotoxicology
• Aquatic Ecology

Background:

• Gammarids, like Gammarus pulex, are crucial aquatic invertebrates for biomonitoring water quality.
• Understanding diet-borne metal uptake is vital for assessing ecological risks in aquatic ecosystems.

Purpose of the Study:

• To quantify copper and cadmium assimilation efficiencies in Gammarus pulex using a pulse-chase stable isotope method.
• To determine food ingestion rate (IR) and gut retention time (GRT) in G. pulex.
• To evaluate the contribution of diet-borne cadmium to overall bioaccumulation.

Main Methods:

• A pulse-chase stable isotope approach using (65)Cu, (106)Cd, and (53)Cr-labeled alder leaves was employed.
• Gammarus pulex were fed labeled leaves for 7.5 hours, followed by unlabeled leaves for 5 days.
• Metal concentrations in gammarids, food, water, and feces were analyzed to calculate assimilation efficiencies (AE), IR, and GRT.

Main Results:

• Gut passage time was estimated to be less than 9 hours, with a 24-hour GRT and 0.69 µg g⁻¹ d⁻¹ IR.
• Cadmium assimilation efficiency (AE) ranged from 5-47%, varying with the calculation method.
• Copper AE could not be determined due to rapid regulation and analytical challenges; chromium showed poor assimilation.

Conclusions:

• Diet-borne cadmium uptake is a significant contributor (66-95%) to cadmium bioaccumulation in Gammarus pulex.
• The stable isotope method is effective for studying metal assimilation in aquatic invertebrates.
• Further research is needed to understand copper dynamics and potential analytical improvements.