RIASSUNTO
A. Skadsheim, V. Hoivangli and C. Labes-Carrier, Elf Marine Environment Centre (Elf Akvamiljo), Stavanger, Norway
Abstract
Accidental spills and production lead to discharges of petroleum hydrocarbons and surface active agents to the sea. The Norwegian government has set guidelines adopted from the OSPAR commission for assessment and studies of the environmental load from these discharges. The free water masses are poorly studied compared to the benthic processes in this context and we question how oil and surfactants might bioaccumulate in a simplified marine pelagic food chain comprised of algae, crustaceans and fish.
When test methods and species recommended for initial water based acute toxicity studies are to be implemented in more comprehensive studies like assessment of bioaccumulation various problems arose. An improvement of the OSPAR method for the production of Water Accommodated Fractions (WAFs) of oil is presented. Emphasis is on control of oil concentration and distribution in water, and on applicability for studies where larger volumes of WAF are required than for the demand in acute toxicity tests. Acute toxicity assessments of one oil, Blended Arabian Light topped at 150 C, and two non-ionic dispersants hexaetoxyparanonylphenol and a sophorolipid, were conducted on OSPAR recommended species. The toxicity responses were in line with observations made by others. At a given concentration the oil particle size during WAF preparation might influence subsequent expression of toxic effects. The same applied for the presence of emulsified oil particles in the WAFs where the organisms were exposed. Reasons for selecting other test organisms than those officially recommended for continued studies on bioaccumulation are presented and discussed.
Introduction
Oil exploration leads to accidental spills and the associated use of surfactants and in addition off-shore production of oil and gas leads to discharges of petroleum hydrocarbons and surface active substances to the sea. Surfactants strongly influence the dissolution of hydrocarbons and the formation and behaviour of oil particles. Although most marine organisms only briefly encounter such materials, some exposures may be acutely toxic, but the greatest concern is about how organisms over long time periods may accumulate the substances occurring at low concentrations and magnify the problem in food chains.
The free (pelagic) water ocean masses is poorly studied compared to benthic (bottom related) processes. However, as the Norwegian offshore activity extends to deeper waters and move northwards the contact with organisms connected to some of the worlds largest pelagic (herring) and benthic (cod) fisheries is increased. This concern is expressed in forthcoming Norwegian offshore monitoring regulations. A major question is thus to model concentration and time dependent exposures of petroleum chemicals to the pelagic food chain.
Guidelines for impact studies of offshore activities in the North-East Atlantic, including the Norwegian sector, are recommended by the OSPAR commission (commission for the Oslo and Paris Conventions for the Prevention of Marine Pollution, Annex 10, 5.15). Regulations and recommendations issued by the Norwegian Ministry of Environment are handled by the Norwegian Pollution Control Authority (SFT). The main lines are as follows for regulating the use of chemicals in order to assess hazards, discharges and environmental distribution: perform physical and chemical characterisation of the discharge, measure distribution by dilution or diffusion, conduct toxicity tests, bioaccumulation and biodegradation studies. Following problem definition and gathering of available data, studies may be requested at three levels which grade from clarifying studies to encompassing investigations (research projects). The key tasks are repeated with increasing efforts at each level.
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