NATURAL VARIABILITY OF BENTHIC SPECIES COMPOSITION IN THE DELAWARE BAY

Biological monitoring of aquatic biota is used to assess the impact of changes in the environment. Critical to the development of a sound bi ological monitoring protocol is the judicious selection of organisms a nd organism characteristics to be monitored. Accurate interpretations of change necessitate description of the natural variability of the sy stem. We introduce a state-space model for compositional monitoring da ta, and illustrate how one can incorporate spatial structure and covar iates to assess natural variability. The methods are illustrated on be nthic survey data from Delaware Bay, and applied to proportional compo sition at the genus level. The distribution of benthic macroinvertebra tes in Delaware Bay depends significantly on salinity. There is residu al spatial dependence in the data after accounting for the salinity ef fect.