Exposure to crude oil micro-droplets causes reduced food uptake in copepods associated with alteration in their metabolic profiles

• Published in: Aquatic toxicology 2017-03, Vol.184, p.94-102
• Main Authors: Hansen, Bjørn Henrik, Altin, Dag, Nordtug, Trond, Øverjordet, Ida Beathe, Olsen, Anders J., Krause, Dan, Størdal, Ingvild, Størseth, Trond R.
• Format: Article
• Language: English
• Subjects: Animals; Copepod filtration; Copepoda - drug effects; Copepoda - metabolism; Eating - drug effects; Endogenous metabolites; Environmental Exposure; Metabolite profiling; Metabolome - drug effects; Micro-droplets; Oil dispersion; Petroleum - toxicity; Petroleum Pollution; Water Pollutants, Chemical - toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2017.01.007

•The contribution of micro-droplets to oil dispersion toxicity was studied.•Micro-droplet exposure caused a reduction in food uptake in copepods associated with starvation-type alterations in metabolite profiles.•The toxic modes of action appear not to be dependent on crude oil type. Acute oil spills and produced water discharges may cause exposure of filter-feeding pelagic organisms to micron-sized dispersed oil droplets. The dissolved oil components are expected to be the main driver for oil dispersion toxicity; however, very few studies have investigated the specific contribution of oil droplets to toxicity. In the present work, the contribution of oil micro-droplet toxicity in dispersions was isolated by comparing exposures to oil dispersions (water soluble fraction with droplets) to concurrent exposure to filtered dispersions (water-soluble fractions without droplets). Physical (coloration) and behavioral (feeding activity) as well as molecular (metabolite profiling) responses to oil exposures in the copepod Calanus finmarchicus were studied. At high dispersion concentrations (4.1–5.6mg oil/L), copepods displayed carapace discoloration and reduced swimming activity. Reduced feeding activity, measured as algae uptake, gut filling and fecal pellet production, was evident also for lower concentrations (0.08mg oil/L). Alterations in metabolic profiles were also observed following exposure to oil dispersions. The pattern of responses were similar between two comparable experiments with different oil types, suggesting responses to be non-oil type specific. Furthermore, oil micro-droplets appear to contribute to some of the observed effects triggering a starvation-type response, manifested as a reduction in metabolite (homarine, acetylcholine, creatine and lactate) concentrations in copepods. Our work clearly displays a relationship between crude oil micro-droplet exposure and reduced uptake of algae in copepods.