A major settlement event associated with minor meteorologic and oceanographic fluctuations

Settlement of ophiuroids (Ophiopholis aculeata, Ophiura spp.) was measured using artificial collectors at 3-day intervals during their annual 2-week s ettlement period in July-August 1993 in St. Margaret's Bay, Nova Scotia. Hy drographic (temperature, salinity, current velocity, wave height and period ) and meteorologic conditions (atmospheric pressure and wind velocity) were recorded concurrently at the site or at nearby locations. A major settleme nt pulse occurred over one 3-day period, with declining settlement over the following 6 days. This pulse was associated with a shift in current direct ion and preceded by rapid temperature and salinity fluctuations. Similar ch anges in temperature occurred at a second site (4.5 km away), indicating at least bay-scale forcing. This period was characterised by the passage of w eak atmospheric pressure gradients and a low-energy sea state. These meteor ologic and oceanographic fluctuations were within the normal range for this time of year, indicating that major settlement events can occur at scales of days in association with minor fluctuations in the physical environment.