Recent Trends in Coastal Environmental Quality: 

 Results from the Mussel Watch Project 1986 to 1993 



Thomas P. O'Connor and Benoit Beliaeff^ 



N0AAN/0RCA21 



National Status and Trends Program 



Silver Spring, MD 20910 



INTRODUCTION 



DOCUMENT 

 LIBRARY 



Woods Hole Oceanographic 

 Institution 



r\ m 



The National Oceanic and Atmospheric Administration (NOAA) created the National Status and Trends 

 (NS&T) Program in 1984 to address national concerns over the quality of the coastal marine environ- 

 ment. One of its goals is to assess spatial distributions and temporal trends in chemical contamination. 

 To meet that goal, the NS&T Mussel Watch Project was formed in 1986 to measure concentrations of 

 a broad suite of trace metals and organic chemicals in surface sediments and whole soft-parts of mus- 

 sels and oysters collected from about 300 coastal and estuarine sites. Here we summarize results from 

 eight years of annually collecting and analyzing mollusks. The most important of these results indi- 

 cates that contamination is decreasing for chemicals whose use has been banned, such as chlorinated 

 hydrocarbons, or severely curtailed, such as cadmium. For other chemicals there is no evidence, on a 

 national scale, for either an increasing or decreasing trend. There are some sites where trace element 

 concentrations are both "high" and increasing. 



CHEMICALS MONITORED 



The elements and groups of organic compounds listed in Table 1 are the subjects of this report. The 

 elements are all potential contaminants in the sense that their concentrations in the environment have 

 been altered by human activities (Nriagu, 1989). Three of the organic groups, total DDT (ZDDT), total 

 chlordane (£Cdane), and total dieldrin (XDield) are chlorinated pesticides. Uses of DDT and dieldrin 

 were banned in the United States in the 1970s. Chlordane use on U.S. crops ended in 1983, and its use 

 for termite control effectively ended in 1988 (Shigenaka, 1990). Polychlorinated biphenyls (LPCB) 

 are a mixture of chlorinated compounds first used in the 1920s for a number of industrial purposes. 

 Their high heat capacities and low dielectric constants were exploited for use in electrical transformers 

 and capacitors. PCB use in the United States began being phased out in 1971, and a ban on new uses 

 took effect in 1976. Large changes in concentrations of ZDDT and LPCB were seen at some locations 

 in the 1970s following bans on their further use (Meams et al., 1988), but the compounds are still found 

 in tissues and sediments. PCB-containing devices are still in use, chlordane remains in the ground as a 

 termiticide, and DDT remains in the environment because of its resistance to degradation. The pesti- 

 cide DDT is metabolized to DDE and DDD in the environment, but those compounds degrade very 

 slowly under environmental conditions. The three butyltin compounds, aggregated as ZBT, are found 

 in mollusks because tributyltin (TBT) has been used as an antifouling agent in the paint commonly 

 used on boats and some underwater marine facilities. Its use on vessels under 75 feet long was banned 

 in 1988 by the U.S. Organotin Anti-Fouling Paint Act. Tributyltin degrades to dibutyltin and then 

 monobutyltin, which itself does not persist, so unlike the chlorinated compounds, ZBT should degrade 

 relatively quickly (Seligman et al., 1988). Consequently, the NS&T Program should find substantial 

 decreases in ZBT concentrations during the next several years. 



'Permanent address: IFREMER, BP 1 105, 4431 1 Nantes Cedex 03, FRANCE 

 ^All tables and figures are located at the end of this report. 



