To assess the potential effects of petroleum hydrocarbons at population and ecosystem levels, especially for fish stocks and critical habitats such as mangroves and coral reefs.
Many of the studies conducted since 1985 have addressed these recommendations and have led us to a better understanding of the vulnerability of different habitats and different life history stages of a variety of marine organisms. Field and laboratory investigations have integrated studies of chemical fate and biological effects so that an improved understanding of the recovery process has been defined. In addition, oil spills have been monitored for longer periods of time and across wider far-field conditions to examine the chronic, long-term effects of spills. In their synthesis volume, Long-Term Environmental Effects of Offshore Oil and Gas Development, Boesch and Rabalais (1987) identified several important areas of research needs that complemented those identified in the Oil in the Sea report. Based on detailed consideration of the probability and severity of effects and the potential for resolution of uncertainties, they identified ten categories of potential long-term environmental effects. These were:
Chronic biological effects resulting from the persistence of medium and high molecular weight aromatic hydrocarbons and heterocyclic compounds and their degradation products in sediments and cold environments.
Residual damage from oil spills to biogenically structured communities, such as coastal wetlands, reefs and vegetation beds.
Effects of channelization for pipeline routing and navigation in coastal wetlands.
Effects of physical fouling by oil of aggregations of birds, mammals, and turtles.
Effects on benthos of drilling discharges accumulated through field development rather than from exploratory drilling.
Effects of produced water discharges into nearshore rather than open shelf environments.
Effects of noise and other physical disturbances on populations of birds, mammals, and turtles.
Reduction of fishery stocks due to mortality of eggs and larvae as a result of oil spills.
Effects of artificial islands and causeways in the Arctic on benthos and anadromous fish species.
Many of these concerns have now been fully addressed and are detailed in several synthesis reports written since 1987 (Box 5-1). Those topics not covered in synthesis reports will be addressed in this report.
The responses of organisms to petroleum hydrocarbons can be manifested at four levels of biological organization: (1) biochemical and cellular; (2) organismal, including the integration of physiological, biochemical and behavioral responses; (3) population, including alterations in population dynamics; and (4) community, resulting in alterations in community structure and dynamics. Impairment of behavioral, developmental, and physiological processes may occur at concentrations significantly lower than acutely toxic levels; such responses may alter the long-term survival of affected populations. Thus, the integration of physiological and behavioral disturbances may result in alterations at the population and community levels.
The effects of petroleum hydrocarbons in the marine environment can be either acute or chronic. Acute toxicity is defined as the immediate short-term effect of a single exposure to a toxicant. Chronic toxicity is defined as either the effects of long-term and continuous exposure to a toxicant or the long-term sublethal effects of acute exposure (Connell and Miller, 1984). Acute and chronic toxicity of petroleum hydrocarbons to marine organisms is dependent upon:
concentration of petroleum hydrocarbons and length of exposure,
persistence and bioavailability of specific hydrocarbons,
the ability of organisms to accumulate and metabolize various hydrocarbons,
the fate of metabolized products,
the interference of specific hydrocarbons (or metabolites) with normal metabolic processes that may alter an organism’s chances for survival and reproduction in the environment (Capuzzo, 1987), and
the specific narcotic effects of hydrocarbons on nerve transmission.
Many of the early studies of acute toxicity focused on the toxicity of individual compounds to marine organisms or the differential toxicity of crude and refined oils (Anderson, 1979). The findings from these types of studies can be summarized as follows: The acute toxicity of individual hydrocarbons is largely related to their water solubility. The acute toxicity of a specific oil type is the result of the additive toxicity of individual compounds, especially aromatic compounds. Narcotic effects of individual petroleum compounds are an important component of acute toxicity and are most closely related to low molecular weight volatile compounds (Donkin et al., 1990). Sublethal effects following acute or chronic exposure to petroleum hydrocarbons include disruption in energetic processes; interference with biosynthetic