Immediate ecotoxicological effects of short-lived oil spills on marine biota

TLDR

Marine environments are frequently exposed to oil spills, yet the ecological impacts of the more common small spills have received little attention compared to large documented events. The study aims to address this gap by evaluating the immediate effects of small oil spills on marine biota. This was achieved through two supervised full‑sea releases of 5 m³ of crude oil, supplemented by on‑board mesocosm experiments and sampling of naturally occurring slicks. Rapid on‑board assays revealed high bioavailability and toxicity of dissolved and dispersed oil within 24 h, even at 8 m depth, causing selective plankton decline and demonstrating that small spills exert immediate adverse biological effects that could cumulatively impair ecosystem functioning.

Abstract

Marine environments are frequently exposed to oil spills as a result of transportation, oil drilling or fuel usage. Whereas large oil spills and their effects have been widely documented, more common and recurrent small spills typically escape attention. To fill this important gap in the assessment of oil-spill effects, we performed two independent supervised full sea releases of 5 m(3) of crude oil, complemented by on-board mesocosm studies and sampling of accidentally encountered slicks. Using rapid on-board biological assays, we detect high bioavailability and toxicity of dissolved and dispersed oil within 24 h after the spills, occurring fairly deep (8 m) below the slicks. Selective decline of marine plankton is observed, equally relevant for early stages of larger spills. Our results demonstrate that, contrary to common thinking, even small spills have immediate adverse biological effects and their recurrent nature is likely to affect marine ecosystem functioning.