Effects of short-duration oil exposure on bay anchovy (Anchoa mitchilli) embryos and larvae: mortality, malformation, and foraging.

Abstract

The Deepwater Horizon oil spill highlighted the need to understand the effects of oil exposure on marine eggs and larvae. To determine how short-duration exposure impacts the survivability of early life stages of the bay anchovy, Anchoa mitchilli, embryos and larvae ≤ 3-days-post-hatch (dph) were exposed to high-energy water accommodated fractions of weathered crude oil for 2 or 6h. Lethal and sublethal effects of short-duration oil exposure were observed, including crippling malformations and altered optimal swimming and foraging behavior of larvae without malformation. The probability of mortality for larvae exposed as embryos (37.37 and 77.31µg L-1 total polycyclic aromatic hydrocarbons or 'TPAH'), assessed 48h after exposure, increased from 0.06 to 0.15 (2h) and 0.10-0.23 (6h) relative to unoiled controls. When exposed as 1-dph larvae (8.80-37.37µg L-1 TPAH) and assessed 24h after exposure, the probabilities increased from 0.20 to 0.76 (2h) and 0.28-0.99 (6h). Among surviving larvae, probabilities of yolk-sac, finfold, notochord, and cranio-facial malformations increased with exposure concentration, duration, and time after exposure by up to 0.07 immediately following exposure of 1-dph larvae and 0.55 24h after exposure. When assessed 48h after exposure as embryos, the probability of larval malformation reached 0.43. First-feeding (3-dph) foraging behavior was altered immediately and 24h after 2h exposures (8.80-77.31µg L-1 TPAH). Time spent in motion and swim speed increased with exposure concentration by up to 331% and 189%, respectively. The number of bursts min-1 increased by 293% immediately and 152% 24h after exposure. Burst distance decreased by 201%. Pause duration and burst speed decreased by 391% and 250% immediately and 124% and 109% 24h after exposure. No effects were found for burst duration or tortuosity. Our results suggest potential cascading effects on fitness and trophic interactions.