Meeting Abstract
62.2 Wednesday, Jan. 6 Where larval supply fails to forecast settlement ZIMMER, C.A.*; STARCZAK, V.R.; ZIMMER, R.K.; Univ. of California, Los Angeles; Woods Hole Oceanographic Inst., MA; Univ. of California, Los Angeles cazimmer@biology.ucla.edu
Forecasting larval settlement from supply is critical in designing marine protected areas and developing recovery strategies for highly impacted regions. Such predictions have been seriously data limited. We simultaneously measured biological, physical and geochemical variables in a subtidal, muddy habitat, including settlement selectivity (24 h, flush trays); infaunal density in ambient sediments; larval/juvenile density in surficial flocculated particulates (floc); time series of near-bottom (0.75 mab) larval concentrations (moored, automated, zooplankton pump) and of flow (1 mab; S4 electromagnetic current meter). Polychaetes, presented here, were the most abundant taxon at the site. Supply did not predict settlement. The variables fluctuated widely, being decoupled from each other and the tidal currents. Recruitment into tray sediments was suggestive of active choice, but means were not significantly different due to high variances. Moreover, time series of near-bed larval concentrations were extremely spiky. Floc, with high larval/juvenile densities (105-106/m3), may have an unsung role in settlement dynamics. Of the two most abundant species in floc, Mediomastus ambiseta was dominant at, and Sabellaria vulgaris (native to sands and cobbles) was absent from, the study site. Mediomastus was not collected in the near-bed plankton, but dominated the trays and cores, whereas Sabellaria was extremely abundant in near-bottom waters, but missing from the bed (trays and cores). With its substantial reservoir of potential settlers, floc touching down on the bottom may seed it with native fauna, while retaining species naturally residing elsewhere. Here, where larval supply failed to forecast settlement, mobile near-bed floc could be an important factor enhancing settlement variability.
