Sensitivity of calcification to thermal history differs between sexes in the gonochoric reef-building corals Dichocoenia stokesi and Dendrogyra cylindrus

Abstract

Calcification and sexual reproduction in corals are energy consuming metabolic processes. In symbiotic corals, calcification is a daily process and depends on the ability of the coral colony to produce energy, through the photosynthesis of symbiotic algae or heterotrophy, while sexual reproduction in several broadcast spawning species is carried out once a year and depends on the amount of energy stored as lipids within the coral tissue. Calcification and reproduction are influenced by environmental parameters, such as light irradiance and sea surface temperature (SST). Reproduction may be inhibited by thermal stress and coral calcification rate decreases as SST increases above a certain threshold. However, it is unknown if there is a sex-related response of calcification rate to thermal history. Here, we test the differential sensitivities of calcification rates to thermal history by examining its recent historical variation in females and males of two common Caribbean gonochoric reef-building coral species, Dichocoenia stokesi and Dendrogyra cylindrus. Colony sex was determined by histological techniques, and sclerochronology was measured using densitometry from digitized X-ray images. Calcification rates were higher in male colonies than in females of both species, as previously reported in other gonochoric corals, and can be explained in terms of disparity in energy availability for calcification among sexes due to the differential energetic costs of eggs and sperm. Calcification rates of both species were negatively related to SST when data of both sexes were pooled together. When data were analyzed separately by sex, only female colonies, of both species, showed a significant dependence of calcification rate to SST. The fact that SST differentially affects coral calcification in female and male colonies, will have repercussions on population dynamics of the studied coral species in a global warming scenario.