On the Gulf Coast, Mussel Watch Project samples have been collected and analyzed by the Texas A&M University's Geochemical and Environmental Research Group, while Battelle is responsible for the U.S. East and West Coasts. Science Applications International Corporation was responsible for the first four years of the Californian and Hawaiian portions of the West Coast effort.
Criteria for the selection and sampling of National Status and Trends Mussel Watch sites are provided below: - The NS&T Mussel Watch Project is not intended to quantify contaminants in "hot spots;" rather, mollusk collection sites were selected to be representative of their surroundings. Therefore, Mussel Watch sites were not located in areas such as New Bedford Harbor, where PCB concentrations are known to be uniquely high, or near waste discharge points or poorly flushed industrialized waterways. - Sampling substrates, where possible, are limited to natural substrates or structures containing them, such as rock (including rip-rap and jetties), sand, or mud. - Indigenous populations of mollusks must exist because caged mussels are not used in the regular monitoring effort. This criterion and constraint is one of the most important because mollusks are not uniformly distributed in the marine environment. - The NS&T Mussel Watch Project selected sites that were sampled by the earlier Environmental Protection Agency Mussel Watch monitoring program (Palmieri et al., 1984). Selecting sites that are coincident to the two monitoring efforts allows decadal comparisons between estuarine contaminants (Lauenstein et al., 1990). Some locations that formerly supported bivalve mollusks and were sampled by the Environmental Protection Agency no longer support bivalve populations. - Mussel Watch Project sites are collected in late fall and winter. Once a site and field sampling methods were established, repeat sampling was to occur within ±3 weeks of that sampling date. The rationale for winter sampling was to avoid collecting spawning organisms. When mollusks are collected at the same time of year, their spawning status is more likely to be the same as that of the previous year, improving the chances of discovering temporal trends.
The number of species sampled is kept to a minimum in order to facilitate the greatest number of spatial data comparisons. The species collected include the blue mussel (Mytilus edulis) from Maine to Delaware Bay. Mytilus edulis alternates with the California mussel (Mytilus californianus) for West Coast collections. From Delaware Bay south and throughout the Gulf of Mexico, the American oyster (Crassostrea virginica) was sampled. Areas distant from the conterminous United States and those specimens collected in fresh water require the collection of alternate species. Ostrea sandvicensis is taken at Hawaiian Islands sites. The species collected from Puerto Rico is the Mangrove oyster (Crassostrea rhizophorae), at a site in southern Florida, the smooth edged jewel box (Chama sinuosa) is collected, and on the Great Lakes the introduced species is the zebra mussel (Dreissena polymorpha).
Sites in Puerto Rico and in the Great Lakes were added in 1992. Three sites were established in Puerto Rico and seven sites were established in the Great Lakes region (Saginaw Bay, Lake Huron, Lake St. Clair, and Lake Erie).
Though the predominant mussel species collected for this project has been identified as M. edulis, there is some uncertainty whether mussels found on the U.S. West coast are the separate species Mytilus trossulus and Mytilus galloprovincialis, or whether all three taxonomic groups are simply hybrids of each other. The question of whether these groups are separate species or are a species complex is discussed in detail in Seed, 1992.
Analyses of co-occurring species have been performed by the National Status and Trends Program (NOAA, 1989). M. edulis and C. virginica on the East Coast, and Mytilus edulis and Mytilus californianus on the West Coast, were compared for trace element and organic contaminant concentrations. While differences were found between the abilities of C. virginica and M. edulis to concentrate certain trace elements, there was no clear difference between the bioaccumulation abilities of the two mussel species (NOAA, 1989).
Criteria for the selection and sampling of National Status and Trends Mussel Watch sites are provided below:
- The NS&T Mussel Watch Project is not intended to quantify contaminants in "hot spots;" rather, mollusk collection sites were selected to be representative of their surroundings. Therefore, Mussel Watch sites were not located in areas such as New Bedford Harbor, where PCB concentrations are known to be uniquely high, or near waste discharge points or poorly flushed industrialized waterways.
- Sampling substrates, where possible, are limited to natural substrates or structures containing them, such as rock (including rip-rap and jetties), sand, or mud.
- Indigenous populations of mollusks must exist because caged mussels are not used in the regular monitoring effort. This criterion and constraint is one of the most important because mollusks are not uniformly distributed in the marine environment.
- The NS&T Mussel Watch Project selected sites that were sampled by the earlier Environmental Protection Agency Mussel Watch monitoring program (Palmieri et al., 1984). Selecting sites that are coincident to the two monitoring efforts allows decadal comparisons between estuarine contaminants (Lauenstein et al., 1990). Some locations that formerly supported bivalve mollusks and were sampled by the Environmental Protection Agency no longer support bivalve populations.
- Mussel Watch Project sites are collected in late fall and winter. Once a site and field sampling methods were established, repeat sampling occurs within ±3 weeks of that sampling date. The rationale for winter sampling is to avoid collecting spawning organisms. When mollusks are collected at the same time of year, their spawning status is more likely to be the same as that of the previous year, improving the chances of discovering temporal trends.
The number of species sampled is kept to a minimum in order to facilitate the greatest number of spatial data comparisons. The species collected include the blue mussel (Mytilus edulis) from Maine to Delaware Bay. Mytilus edulis alternates with the California mussel (Mytilus californianus) for West Coast collections. From Delaware Bay south and throughout the Gulf of Mexico, the American oyster (Crassostrea virginica) iwas sampled. Areas distant from the conterminous United States and those specimens collected in fresh water require the collection of alternate species. Ostrea sandvicensis is taken at Hawaiian Islands sites. The species collected from Puerto Rico is the Mangrove oyster (Crassostrea rhizophorae), at a site in southern Florida, the smooth edged jewel box (Chama sinuosa) is collected, and in the Great Lakes the introduced species is the zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena bugensis) are collected.
Though the predominant mussel species collected for this project has been identified as M. edulis, there is some uncertainty whether mussels found on the U.S. West coast are the separate species Mytilus trossulus and Mytilus galloprovincialis, or whether all three taxonomic groups are simply hybrids of each other. The question of whether these groups are separate species or are a species complex is discussed in detail in Seed, 1992.
Analyses of co-occurring species have been performed by the National Status and Trends Program (NOAA, 1989). M. edulis and C. virginica on the East Coast, and Mytilus edulis and Mytilus californianus on the West Coast, were compared for trace element and organic contaminant concentrations. While differences were found between the abilities of C. virginica and M. edulis to concentrate certain trace elements, there was no clear difference between the bioaccumulation abilities of the two mussel species (NOAA, 1989).
Newly established sites are assigned a new site name and unique site code. Sites that have been minimally relocated may retain the same name or may be renamed if the new name better signifies the relocated site.
The number of species sampled is kept to a minimum in order to facilitate comparisons among sites. The species collected include the blue mussel (Mytilus edulis) from Maine to Delaware Bay. M. edulis alternates with the California mussel (Mytilus californianus) for West Coast collections. From Delaware Bay south and throughout the Gulf of Mexico, the American oyster (C. virginica) is sampled. Areas distant from the conterminous United States and those specimens collected in fresh water require the collection of alternate species. The Hawaiian oyster (Ostrea sandvicensis) is taken at Hawaiian Islands sites. The species collected in Puerto Rico is the mangrove oyster (Crassostrea rhizophorae). At a site in southern Florida, the smooth edged jewel box (Chama sinuosa) is collected. In the Great Lakes, the zebra mussel and quagga mussel (Dreissena polymorpha and D. bugensis, respectively), both introduced species(Wright et al., 1996), are harvested.