Journal of Marine Science: Research & Development
Open Access

Abstract

Mollusc veligers are important component of ocean zooplankton as grazers on phytoplankton, prey to other pelagic organisms, and as possible indicators of ocean acidification being calcifying organisms. This study related oceanographic conditions and distribution and abundance of gastropod and bivalve veligers at 0-65m, 65-135m, and 135-200m depth strata in a seasonal coastal upwelling area in Eastern Sulu Sea, Northeastern Mindanao. The shell elemental composition of dominant veligers was also determined to generate baseline data. Seven bivalve veliger morphs belonging to seven families and nine gastropod veliger morphs belonging to five families were identified in samples. Gastropod veligers were more abundant than bivalve veligers, and abundance of both veligers are two- to threefold higher than those in non-upwelling areas. Except for two naticid morphs which were abundant at deeper, cooler and more saline waters, the rest of veligers were generally found at the uppermost (0-65m) chlorophyll a-rich stratum at sampling stations closest to shore and peaked in abundance during rising tide at sunset. Scanning electron microprobe analysis of dominant morphs indicated variable small amounts of C, O, Na, Al, Si, Mg, S, and Cl, but large amounts of Ca. Bivalve veligers showed greater Ca values than gastropod veligers. The presence of Si in three bivalve and three gastropod morphs is a new record, and we attribute this to species-specificity and veliger diet of mainly diatoms which are very abundant in the upwelling area. Amounts of Ca and other elements are similar to published values in veliger shells from normal non-acidified ocean habitats.

Biography

The corresponding and presenting author, Ephrime B. Metillo has completed his Ph.D. at the age of 26 years from the School of Zoology, University of Tasmania in Hobart, Tasmania, Australia through a scholarship from the Government of Australia. He has been a Professor at the Mindanao State University-Iligan Institute of Technology since 1998, and his main fields of interest are plankton biology and ecology and natural resource management. He has published 21 papers in ISI-indexed journals and reviewed several papers submitted to various ISI-indexed journals.