Population dynamics of the onuphid polychaete Diopatra cuprea (Bosc) along a tidal exposure gradient

Abstract

By means of a technique for mapping permanent quadrats, recruitment and survival were followed for an intertidal, sand flat population of Diopatra cuprea (North River Estuary, Beaufort, North Carolina). Relatively constant, distinctive densities were maintained for more than a year, for the three populations monitored in low (longest tidal exposure), medium and high (shortest tidal exposure) density areas. Mortality in the low density area was relatively high from late spring through early fall, coincident with increasing water and air temperatures. Peak mortality in the medium and high density areas occurred in winter. Although recruitment into all three sites was low, the high density area had a greater number of recruits than the other two sites. Highest adult survival offset lowest recruitment to maintain the medium density subpopulation (site B). Thus, this area has the lowest population turnover (6·1 years) of the three sites. The high density site had the greatest rate of population turnover (2·9 years), reflecting highest rates of mortality and recruitment. The use of long-term, individual monitoring is an effective method of studying variation in population dynamics.