Survival and reproductive outcomes of arsenic and phosphorus exposure in Chironomus riparius Meigen (Diptera: Chironomidae)

Arsenic is an important pollutant of surface waters, and contamination is quickly becoming a worldwide issue. Exposed parent rock is subjected to weathering and oxidative processes that release arsenic into the environment. Due to its chemical similarity to phosphorus, it is readily taken up and incorporated by plants in aquatic systems, and the presence of phosphorus has been documented to increase absorption of arsenic. With increased use of fertilizers in agricultural settings, runoff events have the potential to boost phosphorus concentrations in arsenic contaminated waterways. While well documented in plants, this synergistic interaction has yet to be examined in insects. Chironomus riparius is a ubiquitous aquatic collector, with a relatively high pollution tolerance. Ten first instars hatched from a single egg mass were transferred to each of 15 beakers with reconstituted freshwater and exposed factorially to 0, 10, 150, 400, or 1000 μg As/l and 0, 14, or 1400 μg PO₄/l. This was repeated three times. Survival was monitored daily until emergence. Average number of egg masses laid per female and the number of eggs per egg mass were recorded for each treatment. After three days at room temperature, egg masses were evaluated for percent egg hatch. Results from this study provide insight into the impacts of arsenic and phosphorus pollution on survival and reproduction of an important primary aquatic consumer.