Does Water Quality Affect Size-frequency Distribution and Population Abundance of Porites astreoides?

Unplanned coastal development represents a major threat to coral reef health. High sediment loads due to run-off increase water turbidity thereby reducing the amount of light available for Symbiodinium spp. a single cell algae living within the coral tissues, that provides up to 90% of coral energetic requirements. Thus, it could be expected that under poor water quality (PWQ) coral energetic budget would be compromised limiting significantly vital life processes such as growth and reproduction. Hence, the aim of this study is to determine whether (1) size-frequency and (2) population abundance of the scleractinian coral Porites astreoides differ along a water quality gradient. We selected this species because it can be found inhabiting coral reefs with poor and good water quality (GWQ). To assess the population dynamics, three sites with GWQ and three with PWQ where selected in the Puerto Rican archipelago. We hypothesize that colonies in PWQ are energetically limited; therefore, colonies should be smaller and population abundance lower in comparison to sites with GWQ. However, preliminary results based on two GWQ sites and two with PWQ suggest that there is a significant difference in size-distribution frequency between all sites regardless of water quality. In fact, similarities are observed between sites with contrasting water quality suggesting that size-frequency distribution in P. astreoides varies spatially. Nevertheless, population abundance differed significantly only between two contrasting water quality sites. Our data suggest that population structure of P. astreoides is likely site-specific and other factors (e.g. grazer abundance, energy allocation, fecundity) may be influencing size-frequency and population abundance in this specie.