Meeting Abstract
In the face of global climate change, marine organisms are challenged by multiple and interactive environmental stressors. In the subtropics, warming and intensified precipitation, and hence, reduced salinity are particularly relevant. Using the sea urchin, Heliocidaris crassispina, we investigated the effect of warming and hyposalinity on fertilization success and early development because these early life history stages have significant impacts on population dynamics of this commercially harvested species. Gametes were held at two salinities (24 psu and 32 psu) and exposed to a temperature gradient. Fertilization appeared to be less sensitive than blastula formation to warming as indicated by a higher critical temperature (LT50); this observation highlights a sensitivity difference for different developmental stages. When reared at one of the four combinations of temperatures (24°C and 28°C) and salinities (24 psu and 32 psu), larvae in the low salinity treatments had significantly lower survival rates but temperature alone had no effect on survivals. Temperature and salinity has a synergetic effect on larval growth. Larval cloning was documented under both warming and low salinity treatments. However, incomplete separation were observed only at 28°C suggesting the mechanism for cloning may be disrupted under high temperatures. We also observed significant difference between maternal lineages. Such intra-specific variations implies the present of genetic variations upon which natural selection can act, and hence, urchins may be able to adapt to future salinity and temperature stress.
