creased from 0.01 to 1.0 ppb. The majority of the sixth zoeal stages died before 

 reaching the megalopa stage ( Bookhout et al., 1972). In similar studies on larvae of 

 the blue crab, Callinectes sapiclus, however, there was no indication that large num- 

 bers of the eighth zoeal stage occurred when the larvae were exposed to higher con- 

 centrations of mirex (Bookhout and Costlow, 1975). 



Studies on the effect of methoprene on the larvae of the mud crab, Rhithropanopeus 

 harrisii, indicated that while a variety of concentrations of this juvenile hormone 

 mimic did not increase mortality, the combination of high salinity (35 ppt) and 0. 1 

 ppm methoprene resulted in increases in morphological abnormalities of the mega- 

 lopa (Costlow, 1977). In lower salinities (5 ppt and 20 ppt), abnormal megalopa 

 rarely exceeded 4 percent, regardless of the length of an exposure to the compound. 

 Although some abnormal megalopa successfully metamorphosed to the first juvenile 

 crab, many died either as megalopa or during metamorphosis to the first crab. 



Toxic Industrial Compounds 



Many other industrial compounds developed since the late 1920s have been identi- 

 fied in estuarine sediments and waters over much of the United States. Some, such as 

 the phenolics, are derived from coke plants, oil refineries, chemical and pesticide 

 manufacturers, and other industrial complexes. Many of the phenolics occur natu- 

 rally in aquatic and terrestrial vegetation and may be released as a result of processes 

 employed by the pulp and paper industry. Buikema, McGinniss, and Cairns ( 1979) 

 identify various toxic effects for some of the phenolics. The few studies conducted on 

 the biological effects of many phenolics indicate that exposure to phenol and 

 pentachlorophenol concentrations as low as 4 mg 1 results in hemorrhaging at the 

 base of the fins of fish, and higher concentrations cause disruption of blood vessel 

 walls and gill epithelium. Other effects include the reduction of levels of the hormone 

 in fish, changes in blood glucose and blood lactate levels, immunoglobin levels, 

 blood protein levels, and tissue microelement levels. Little is known about the 

 cycling of phenol and phenolics (other than pesticides) in marine ecosystems or the 

 extent to which they persist in substrates and biological systems. 



The polychlorinated biphenyls (PCBs), one of the groups of chlorinated hydro- 

 carbons, are widely used in condensor dielectrics, heat transfer fluids, and hydraulic 

 fluids. They are widely distributed in marine and estuarine environments, and the 

 work of Peakall ( 1975) established that they are toxic to many organisms. The poly- 

 chlorinated naphthalenes have also been identified in the marine environment, but 

 relatively little is known about the effect of these compounds on estuarine and 

 marine systems. Many PCBs have been produced by Monsanto Company under the 

 trade name Aroclor®. Under the trade name Halowax®. the Koppers Company has 

 produced a series of polychlorinated naphthalenes. A number of studies have been 

 conducted to compare the effects of the PCBs and the PCNs within these series. 



Following the identification of Aroclor® 1 254 in the water, sediment, and fauna of 

 Escambia Bay, Florida (Duke et al., 1970), Nimmo conducted several studies on the 

 effects of this and related compounds on various estuarine and marine animals. 

 Whole body residues of Aroclor® 1 254 were found to be as high as 14 mg/ kg in the 

 pink shrimp Penaeus duorarum (Nimmo et al., 1971a), and subsequent studies on 

 juveniles of the same species indicated that approximately 1.0 jug/1 in seawater 

 would kill 50 percent of the experimental animals within 15 days (Nimmo et al., 

 1971b). 



Lethal effects of Aroclor® 1016 and 1 254 have been described for larval and adult 

 fiddler crabs using a combination of temperatures and salinities as synergistic factors 

 (Vernberg et al., 1977). Lethal levels of Aroclor® 1254 for the larval stages of the 

 fiddler crab were found to be approximately 10 ppb, but the same levels of Aroclor® 

 1254 appeared to have a more rapid effect on the larvae than that described for 

 Aroclor® 1016. At the combinations of salinity and temperature used in the experi- 

 ments, Aroclor® 1254 appeared to be more toxic than Aroclor® 1016. 



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