and upper trophic levels. In about 12 of the 20 major coastal 

 systems globally, the dominant fish species has been replaced by 

 another during the past decade. These major changes cannot 

 presently be attributed to long-term changes in the environment or 

 to fishing pressure. Coastal waters globally are also showing an 

 increased frequency of blooms of novel species of noxious and toxic 

 algae, which result in anoxia and large-scale deaths at all trophic 

 levels — events which increase carbon burial rates. Major 

 questions which have emerged are: To what extent is the altered 

 productivity and restructuring of the phytoplankton community a 

 consequence of long-term chemical perturbation, of altered biotic 

 interactions associated with increased toxic phytoplankton bloom, 

 and of changing fish stocks and associated grazing pressure? The 

 increased occurrence of noxious blooms suggests the following 

 hypotheses: coastal environments are undergoing a functional group 

 shift from diatom to flagellates; the selection vector is 

 predominantly a response to an unknown stress, triggering genetic 

 selection; the group selected is better adapted to the 

 environmental perturbation, and is competitively favored in 

 exploiting resources, although its suitability as prey and 

 allelochemical potential may contribute to functional instability, 

 community disequilibrium, and in the extreme case, to community 

 dysfunction. 



There are considerable quantitative data on the taxonomic 

 structure, rates, and routes of carbon fixation, flow, and 

 trophodynamics for a variety of coastal and shelf ecosystems. We 

 must now establish the selective mechanisms by which species and 

 functional groups within each trophic level are selected from the 

 range of potentially available genetic stocks, i.e., genetic 

 diversity; how this selection influences, and varies with, 

 population growth, development, and the processes linking the 

 various trophic levels; and how these linkages influence whole 

 community properties such as succession, diversity, resilience, and 

 equilibrium. We must seek to identify molecular and cellular 

 indices of stress which may serve as an early warning (signal) and 

 predictor of subsequent changes in community structure, function, 

 and dynamics; and to assess predator-prey interaction at the 

 molecular level, and allelochemical determinants of community 

 organization and processes. 



Gene Transfer in the Environment 



111-13 



