THE SEASONAL SETTLEMENT OF POLYCHAETE LARVAE BEFORE AND AFTER POLLUTION ABATEMENT IN LOS ANGELES - LONG BEACH HARBORS, CALIFORNIA
Reish, Donald J.
Department of Biological Sciences, California State University, Long Beach, California 90840 USA
A monthly settlement of polychaete larvae on suspended test panels was studied in 1950-51 and repeated in 1973-75 after the initiation of pollution abatement in 1968 in Los Angeles - Long Beach Harbors. Panels were suspended in the water column from outer to inner harbors and collected monthly. The panels were scraped and the polychaetes identified to the lowest possible taxon. Oil refinery wastes were no longer discharged into the inner harbor after 1968. Prior to abatement, many of the inner harbor stations had little or no dissolved oxygen present in the water, but was usually over 5.0 mL/L after 1968. A combined total of 37 polychaete species were collected of which 20 were taken in 1950-51 and all 37 in 1973-75. An average of 2.7 species per station per collection period was taken prior to pollution abatement compared to 7.5 in 1973-75. Polychaete species averaged 2.9 and 1.8 species per station per collection period in 1950-51 in outer and inner harbor, respectively. This compared to 9.6 and 6.1 in 1973-75 in outer and inner harbor, respectively. Seasonal differences occurred regardless of location in the harbors with the greater number of species taken in Setember in both studies. Fewer numbers of species were collected during the December-February period in both studies. The most frequently occurring species in 1950-51 were also common in 1973-51 plus some additional species. These species were (*indicates seasonal occurrence): Capitella capitata, *Hydroides pacifica, *Paleonotus bellis, *Platynereis bicanaliculata, and Polydoora spp. The additional common species collected in 1973-75 include Armandia brevis, *Ctenodrilus serratus, *Halosydna johnsoni, *Polyophthalmus pictus and members of Family Spirorbinidae. Polychaetes have been used in different ways to monitor environmental conditions including the benthos, sediment bottle collectors and species present on boat floats. The seasonal settlement of polychaete larvae on suspended panels is another monitoring technique which serves to indicate not only its presence but also whether or not the species are able to survive during the time following settlement.