Microplastics do not increase bioaccumulation of petroleum hydrocarbons in Arctic zooplankton but trigger feeding suppression under co-exposure conditions.

Arctic sea ice has alarmingly high concentrations of microplastics (MPs). Additionally, sea ice reduction in the Arctic is opening new opportunities for the oil and maritime industries, which could increase oil pollution in the region. Yet knowledge of the effects of co-exposure to MPs and crude oil on Arctic zooplankton is lacking. We tested the influence of MPs (polyethylene, 20.7 µm) on polycyclic aromatic hydrocarbon (PAH) bioaccumulation and oil toxicity in the key arctic copepod Calanus hyperboreus after exposure to oil with and without dispersant. Up to 30% of the copepods stopped feeding and fecal pellet production rates were reduced after co-exposure to oil (1 µL L-1) and MPs (20 MPs mL-1). The PAH body burden was ~3 times higher in feeding than in non-feeding copepods. Copepods ingested both MPs and crude oil droplets. MPs did not influence bioaccumulation of PAHs in copepods or their fecal pellets, but chemical dispersant increased bioaccumulation, especially of ≥4 ring-PAHs. Our results suggest that MPs do not act as vectors of PAHs in Arctic marine food webs after oil spills, but, at high concentrations (20 MPs mL-1), MPs can trigger behavioral stress responses (e.g., feeding suppression) to oil pollution in zooplankton.

Lipid class and fatty acid content of the leptocephalus larva of tropical eels.

The leptocephalus larva of eels distinguishes the elopomorph fishes from all other bony fishes. The leptocephalus is long lived and increases in size primarily through the synthesis and deposition of glycosaminoglycans. Energy stored during the larval stage, in the form of glycosaminoglycan and lipids, is required to fuel migration, metamorphosis and metabolism of the subsequent glass eel stage. Despite the importance of energy storage by leptocephali for survival and recruitment, their diet, condition and lipid content and composition is essentially unknown. To gain further insight into energy storage and condition of leptocephali, we determined the lipid class and fatty acid concentration of larvae collected on a cross-shelf transect off Broome, northwestern Australia. The total lipid concentration of two families and four sub-families of leptocephali ranged from 2.7 to 7.0 mg g wet weight(-1), at the low end of the few published values. Phospholipid and triacylglycerol made up ca. 63 % of the total lipid pool. The triacylglycerol:sterol ratio, an index of nutritional condition, ranged from 0.9 to 3.7, indicating that the leptocephali were in good condition. The predominant fatty acids were 16:0 (23 mol%), 22:6n-3 (docosahexaenoic acid, DHA, 16 mol%), 18:0 (8.2 mol%), 20:5n-3 (eicosapentaenoic acid, EPA, 6.7 mol%), 18:1n-9 (6.4 mol%) and 16:1n-7 (6.3 mol%). The DHA:EPA ratio ranged from 2.4 to 2.9, sufficient for normal growth and development of fish larvae generally. The leptocephali had proportions of bacterial markers >4.4 %, consistent with the possibility that they consume appendicularian houses or other marine snow that is bacteria rich.