Exposure to de-icers NaCl and beet juice brine alters the function of Malpighian tubules and anal papillae of chironomids (Chironomus riparius)

Salinization of freshwater by anthropogenic activities is a global issue and the use of de-icers in cold climates is turning out to be a major contributor to this problem. The most common de-icer is sodium chloride (NaCl) in the form of rock salt or brine but because the harmful accumulation of NaCl in nearby freshwater systems is well recognized novel organic de-icers like sugar beet juice have been developed. Detrimental effects of NaCl on freshwater animals are documented but potential effects of organic based de-icers are virtually unknown. Insects are one of the most abundant groups of freshwater animals where they perform services vital to ecosystem health. Hence, the aim of this study is to examine the effects of NaCl and a commercially available beet juice de-icer (BBJD) on the osmoregulatory physiology of a ubiquitous freshwater insect, the larvae of Chironomus riparius. Larvae were exposed to sub-lethal doses of de-icers for 24 hours and osmoregulatory status and the function of the Malpighian tubules (MTs) and anal papillae (AP) were assessed. Hemolymph [K+] was tightly regulated while [Na+] was elevated in both de-icers. BBJD caused some dehydration. Larvae reduced ion uptake by the AP where Na+ secretion occurred with the NaCl treatment. BBJD also altered MTs function such that they cleared more K+. BBJD presents its own significant challenges to the osmoregulatory physiology of C. riparius larvae and the relatively high levels of K+ from the sugar beets could pose a new issue for freshwater habitats.