ABSTRACTS 5A 13 STABILIZED COAL ASH AS A SETTLEMENT SUBSTRATUM: ACCEPTABILITY TO OYSTER LARVAE AND POTENTIAL FOR UPTAKE OF CONTAMINANT METALS. K.M. MHRT.I.FR and K.S. £&!££ (lntio. by P.M. C«ffn.y). Coll. of Marina Studies, Univ. of Delaware, Lawei. Coal ash, stabilized with eeaent, has been proposed as an alternative cultch material for flnflsh and shellfish reefs. However, coal ash contains potentially harmful trace and toxic metals. This study was designed to determine the acceptability of

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... e stabilized ash aa a settlement surface for oyster fCrassoatrea vlrglnlca) larvae, and to assess the potential for uptake of contaminant metals from ash by attached oysters. Five experimental substrata were used: oyster shell control, concrete control, and three different ash mixtures. Of approximately 4700 spat, 32.lt and 30.4% settled on oyster shell control and the ash mixture containing bottom ash, respectively. The remaining ash mixtures (primarily fly ash, with less surface texture) had 16.7% and 13.3% of total spat set, while the concrete control had 7.5% of the total spat set. Potential for metals uptake was determined using two substrata: oyster shell and stabilized ash containing bottom ash. Of eight metals analyzed to date, Fe, Mn, and Zn were present in significantly higher quantities in ashgrown oyster tissue. There was no significant difference for Cd and Cu tissue concentrations and concentrations of Cr, Nl, and Pb were below detection limits. Stabilized coal ash appears to be an acceptable settlement substratum for oyster larvae. Hetridium senile is well known for its ability to reproduce asexually, forming large clones. Clone structure was examined in New England populations, using polymorphic enzymes as markers to assess clonal affinity. Samples designed to minimize contributions of cloning show that there are marked differences among populations in the impact of asexual reproduction, with greatest importance of cloning found in the vicinity of Cape Cod. Some samples are composed of many clone mates, even though sampling covers wide areas. On the other hand, although it is conventional wisdom that local aggregations of H. senile are products of cloning, examination of samples collected along transects through aggregations show that this is not always the case. Sometimes clusters are clonal, as expected, but they often are not. There is no obvious geographic pattern to the differences in clonal composition of clusters of Hetridium. The idea that local population density builds up through cloning 1s too simple. Instead it is the product of a complex interaction between cloning and recruitment of sexually produced larvae.