MEPS 127:149-155 (1995)  -  doi:10.3354/meps127149

We examined the likely cause of the dramatic decrease in abundance experienced by a population of reef-building polychaetes Phragmatopoma virgini Kinberg, 1867 at the low rocky intertidal of the Mehuin Marine Reserve, southern Chile. The abundance level there contrasts strongly with the levels of abundance that this species has outside the area. To determine if this decrease resulted from processes operating in the post-settlement stage, we offered textured and untextured cement plates as substrata for settling P. virgini. In addition, in order to assess the effect of mobile consumers on post-settlement mortality, we enclosed settlement plates in cages. After 18 mo of monitoring the abundance of recruits on the artificial plates, we determined that recruitment occurs throughout the year, but with a clear seasonal variation in intensity. Recruitment densities were highest on rough textured plates. The exclusion of consumers resulted in a major increase in the number of recruits on both types of surface. The higher density of recruits on the rough surfaces was probably the result of microenvironmental conditions that enhance settlement and survival of the new settlers by providing a refuge from mobile consumers, specifically dislodgement by rasping invertebrates. We concluded that the decrease observed in the population of P. virgini at the Marine Reserve is the result of higher post-settlement mortality produced by predation activity of high densities of mobile consumers within this reserve.

Polychaeta . Settlement . Phragmatopoma . Rocky intertidal . Marine reserve