Temperature correlates with the daily release oflarvae and their settlement in a temperate Australian ascidian

The distribution and abundance of planktonic larvae may have important consequences for subsequent
patterns of distribution and abundance in the benthic phase of a marine invertebrate's life history. Here I
report daily patterns of larval release and settlement for the colonial, subtidal ascidian Podoclavella moluccensis Sluiter.
The correlation between these variables and their relationship with seawater temperature was
examined. Podoclavella typically releases larvae for a S-6 week period in late spring. Significant differences
in the number of larvae released per day were detected between colonies (n = 5), but daily larval release was
not correlated with colony size, as measured by zooid number. An average of 8.3 (SE = 0.8, n = 5) larvae were
released per day by colonies over the 21 days of monitoring. The release of larvae was positively correlated
with seawater temperature and in turn subsequent settlement was positively correlated with larval release:
larval release accounted for 37 % of the variation in settlement.