A study was made of the relationships between water quality and benthic invertebrates in the Penobscot, Damariscotta and Sheepscot estuaries, representing heavily polluted, moderately polluted and relatively unpolluted conditions, respectively. Preliminary hydrographic, sedimentary and faunal surveys were conducted to determine comparable areas in each estuary to be analyzed for interaction between level of pollution and invertebrate benthic fauna present. Field studies conducted in each area included an analysis of the qualitative and quantitative distribution of benthic invertebrates, the seasonal composition of the meroplankton, the settlement of larvae and the hydrography of the area. Laboratory studies included: the determination of particle size distribution of sediments and the amount of volatile solids present; the facility with which different indigenous species of benthic invertebrates can be cultured in the laboratory; the temperature, dissolved oxygen and salinity tolerances of larvae and adults; experiments on temperature as a factor influencing the spawning of adults; the influence of different substrates upon larval settlement; the effect of water quality upon survival, reproduction, development and growth of benthic invertebrates. (Author)