Overview of Effects of Oil Spills on Marine Mammals

Abstract

The 1989 Exxon Valdez oil spill (EVOS) in Alaska killed tens of killer whales (Orcinus orca), hundreds of harbor seals (Phoca vitulina), thousands of sea otters (Enhydra lutrius), and hundreds of thousands of birds (sea birds, shorebirds, and marine-associated birds) and greatly impacted marine habitats that contain the forage fish and marine invertebrates that fuel higher trophic levels [1–4]. These numbers represent the documented deaths from that spill, which undoubtedly killed many more animals. More than 20 years after the EVOS, long-term individual effects (e.g., impaired health and reproduction) and population impacts, especially in the nearshore ecosystem, are most evident for killer whales, sea otters, and some marine birds. The ongoing effects and slow recovery of some species are attributed to long-term exposure to spilled oil sequestered in nearshore habitats and, in the case of the social killer whale, to the legacy of key pod member mortalities from the oil [5–9].While apparently not as devastating to marine mammals as the EVOS, there is evidence the massive MC-252 Deepwater Horizon (DWH) oil spill in 2010 impacted reproduction and health of coastal bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico [10]. Considering that marine mammals are common, highly visible, charismatic, and potentially vulnerable to oil, it is somewhat surprising that we know relatively little about the effects of oil on individuals and populations. The majority of what has been published in books and peer-reviewed journals comes from a handful of laboratory experiments and the investigations on marine mammals that followed the EVOS. Oil spills can affect marine mammals through a variety of direct and indirect pathways. Direct pathways include inhalation, ingestion, and dermal exposure, each of which can initiate a suite of physiological responses with health and long-term survival and/or reproduction consequences. For most overvIew of effects of oIl spIlls on MarIne MaMMals