Mysids and environmental monitoring: a case for their use in estuaries

Mysids (Crustacea : Mysidacea) are ubiquitous members of the permanent, end emic hyper-benthic fauna of estuarine and other coastal ecosystems. They of ten occur in high numbers and their ecological importance, particularly the ir role in food chains as a link between the benthic and pelagic systems, i s becoming increasingly apparent. In general, mysids are omnivores, feeding on detritus, zooplankton and phytoplankton, and they contribute up to 40% of the standing stock of omnivores in some systems. In estuaries, specific mysid faunas often occur in discrete zones, usually as a result of differen t salinity tolerances, although responses to turbidity and water flow also determine mysid distributions. Many mysids are particularly sensitive to ch emical contaminants as illustrated by their relatively low 96-h LC50 values . Due to this sensitivity, the United States Environmental Protection Agenc y promotes the use of Americamysis (=Mysidapsis) bahia for laboratory toxic ity testing; however, there is growing interest in the use of local, endemi c species rather than the standard American mysid. At Plymouth, never and s ensitive techniques are being developed for assessing sublethal responses t o toxicants by use of the northern European estuarine mysid Neomysis intege r. This paper summarizes the ecological role of mysids in estuaries and des cribes their potential for use for estuarine environmental monitoring.