The role of nutrition in regulating the population dynamics of opportunistic, surface deposit feeders in a mesohaline community

The role of food resources in regulating seasonal population dynamics was determined in a benthic community typical of mesohaline regions in Chesapeake Bay. Four macroinvertebrates dominated the community: the bivalve Macoma balthica , the polychaetes Streblospio benedicti and Nereis succinea , and the amphipod Leptocheirus plumulosus. Several factors seem to regulate population dynamics at different times of the year. In March, growth and reproduction rates accelerated as temperature and phytodetrital sedimentation increased. In April, invertebrate growth rates plateaued while estimated community N requirements were equivalent to estimated N availability. In May, invertebrate growth and reproduction rates rapidly declined while estimated community energy requirements were greater than sedimenting energy supplies. In June, larval recruitment was heavy for S. benedicti and L. plumulosus ; however, these juveniles showed no apparent growth during June and their densities rapidly declined. The sudden appearance and disappearance of these juveniles was solely responsible for the boom‐and‐bust dynamics of S. benedicti and L. plumulosus . Essential W3‐polyunsaturated fatty acids and essential amino acids were present at high levels in spring but were present in only trace amounts during summer. Growth of juvenile S. benedicti and L. plumulosus recruits was most likely limited by food supply in June and July, especially by the availability of essential nutrients. Estimates of predation rates could not account for these population declines.