A few studies have investigated the uptake of petroleum hydrocarbons presented 

 to organisms in forms other than oil-in-water dispersions or water-soluble fractions. 

 Bioaccumulation of fuel oil hydrocarbons adsorbed onto kaolin particles and in- 

 gested by Mytilus edulis has been reported by Fossato and Canzonier ( 1976). Tissue 

 concentrations were measured in excess of 1,000 times the exposure concentration. 

 No accumulation of hydrocarbons was observed in the polychaete Neanthes 

 arenaceodeniata held for 28 days in sediments contaminated with No. 2 fuel oil. 

 Also, l4 C-2-methylnaphthalene spiked detritus was fed to the animal for 16 days 

 without accumulation of radioactivity in tissues (Rossi, 1977). Adetritivorousclam, 

 Macoma inquinata was found to take up naphthalenes from sea water but not sand 

 or detritus contaminated with Prudhoe Bay crude (Roesijadi et al., 1978). 



Concentrations of petroleum hydrocarbons that build up in tissues of organisms 

 during exposure to oil decrease rapidly upon return to clean seawater. The rate and 

 extent of depuration have been determined in a number of studies. Many of the 

 studies have utilized molluscs as test organisms (Lee et al., 1972). One of the most 

 detailed studies of accumulation and depuration has recently been described by 

 Clement et al. (1980). The clam Macoma halthica was found to fractionate hydro- 

 carbons present in a dispersion of Prudhoe Bay crude by preferential retention and 

 release of certain compound classes and homologs. Depuration was followed for 60 

 days, at which time exposed animals still contained tissue hydrocarbon concentra- 

 tions of about 1 10 ;ug 1 (wet weight) as compared with about 14 /ig, 1 for controls. 

 Fossato and Canzonier ( 1976) suggested that rapid loss of petroleum hydrocarbons 

 observed from some Mytilus etiulis was associated with spawning. Similar rapid loss 

 of polychlorinated biphenyls from oysters during spawning has been proposed by 

 Loweet al. ( 1972). Rossi and Anderson exposed male and gravid female polychaetes, 

 Neanthes arenaceodentata. to WSF of No. 2 fuel oil for 24 hours. The animals were 

 then transferred to clean seawater. Male worms were found to depurate naphtha- 

 lenes to undetectable levels within 17 days. Gravid females showed only minor 

 release of naphthalenes during this period. Females analyzed within 24 hours after 

 spawning contained barely detectable levels of naphthalenes. Zygotes and 

 trochophore larvae produced by the spawn had naphthalene concentrations similar 

 to those of the gravid females prior to spawning (Rossi and Anderson, 1977). 



Two major, highly innovative research programs to study the long-term effects of 

 sublethal levels of petroleum and other pollutants at the ecosystem level were de- 

 signed and tested in the seventies. Both of these made use of large microcosms that 

 would simulate a natural ecosystem. 



The Controlled Ecosystem Pollution Experiment (CEPEX) was intended to simu- 

 late the plankton community of open ocean waters (Menzel and Case, 1977). The 

 CEPEX structures were flexible plastic columns enclosing about 500 nv (650 yd') of 

 water. The CEPEX program used copper as the pollutant in most of their experi- 

 ments, although a few oils were tested. A major conclusion of the program was that 

 population structure and succession patterns of plankton are more useful as stress 

 measurements than metabolic ones. The CEPEX concept could be applied to studies 

 of oil impacts on pelagic plankton. Such studies would have been especially useful to 

 test the impact of l.xtoc I oil in the vicinity of the well-head. Arnold showed that 

 slightly weathered Ixtoc oil was acutely toxic to the eggs and newly hatched larvae of 

 redfish (Arnold et al., 1979). Canadian workers have conducted long-term CEPEX 

 type experiments by adding petroleum to plastic cylinders in freshwater lakes (Scott 

 and Shindler, 1978). They reported that the bacteria populations were enhanced. 

 However, the zooplankton populations in the oiled ponds were drastically reduced 

 when the ice cover.on the pond melted. The phytoplankton community structure was 

 changed by the oil but no clear pattern was obvious. The experiments did not include 

 a benthic element. 



Large microcosms established at the Marine Ecosystem Research Laboratory 

 (MERL) have both a pelagic (water column) and a benthic (sediment) component. 

 This allows studies of the transport of pollutants such as oil to the sediment and of 



106 



