MOLECULAR TOOLS IN MARINE ECOLOGY

Molecular tools have diver se applications in marine ecology. In micro bial systems, DNA sequences of rRNA and other genes have identified a variety of novel lineages of bacteria inhabiting marine environments t hat have resisted traditional culture methods. However, relatively few natural populations have been characterized due to the rather labor-i ntensive methodologies employed. Recent technological developments suc h as in situ PCR and flow cytometry promise to greatly enhance the spe ed at which microbial taxa can be identified and enumerated in field c ollected water and substrate samples; such advances will allow future work to employ the spatial and temporal field sampling required to mon itor the impact of natural and anthropogenic changes in the environmen t. This approach also holds promise for examining physiological status of field collected cells, garnering information on such elusive param eters as growth rates and the extent of nutrient limitation under natu ral conditions. Studies of macrobiota have similarly benefited from th e use of molecular approaches to species identification. This has been particularly true with regard to distinguishing among larval forms of closely related taxa which are nearly identical morphologically. Gene tic variation within species assayed by molecular tools has been usefu l in examining the stability of populations through time and in assess ing patterns of recruitment to geographically separated populations. E nhanced understanding of these ecological problems will also require i ntensive spatial and temporal monitoring of both larval and adult popu lations. Often, the newer techniques based on DNA sequence variation h ave practical advantages over allozyme techniques: e.g., PCR allows as say of minute quantities of DNA that may come from ethanol preserved s amples. However, when ample allozyme variation exists to address a giv en issue, these older techniques may be favored on a variety of criter ia, including spaed and cost. Hence, choice of methodology should be b ased on the expected efficiency of a given approach to a specific prob lem rather than the apparent sophistication of the method itself.