LOCAL-SCALE POPULATION TRENDS OF THE POLYCHAETE CHAETOPTERUS PERGAMENTACEUS AND THE RELATIONSHIP TO PHYSICAL PROCESSES AND ORGANIC MATTER GRADIENTS
Thompson, M. & Schaffner, L. C.
The College of William & Mary, School of Marine Science, Virginia Institute of Marine Science, Gloucester Point, VA 23062, USA
The suspension feeding polychaete Chaetopterus pergamentaceus is a key functional species of many coastal environments. Populations of this large tubicolous annelid are widely distributed at subtidal depths in the lower, polyhaline Chesapeake Bay estuary. Population trends on a local scale that may be linked to physical processes or organic matter supply gradients will indicate factors and mechanisms that affect the individual yet regulate overall population structure. Over a two year period, investigations into local population trends across energy and production gradients were conducted. Twelve randomly selected sites were sampled within a 54 km2 study region, the northeastern portion of which experiences lower energy conditions, decreased sediment mixing rates, more fine grained sediments, and potentially differences in sediment carbon, nitrogen and chlorophyll a compared to the southwestern portion. Preliminary evidence suggests no difference in growth rates among juveniles between sites. However, intra- and interannual differences in the adult population may be related to phasing of organic matter changes. Temporal population trends between sites will be discussed in relationship to physical processes and organic matter gradients.