Results from controlled in situ experimentation conducted on the leeward reef tract of Curaçao, Netherlands Antilles, indicate that the coral Montastraea annularis exhibits a complex, yet consistent, cellular response to increasing sea surface temperature (SST) and decreasing irradiance. This was determined by simultaneously quantifying and tracking the tissue density of zooxanthellae and mucocytes using a novel technique that integrates the lectin histochemical stain wheat germ agglutinin (WGA) with high-resolution (200 nm) optical epifluorescence microscopy. Coral colonies growing at 6-m water depth (WD) and an irradiance of 100. 2 ± 6. 5 μmol m-2 s-1 were treated with a shading experiment for 11 days that reduced irradiance to 34. 9 ± 6. 6, 72. 0 ± 7. 0 and 90. 1 ± 4. 2 μmol m-2 s-1, respectively. While a significant decrease in the density of both zooxanthellae and mucocytes were observed at all shade levels, the largest reduction occurred between the natural non-shaded control (44,298 ± 3,242 zooxanthellae cm-2; 4,853 ± 346 mucocytes cm-2) and the highest shading level (13,982 ± 1,961 zooxanthallae cm-2; 2,544 ± 372. 9 mucocytes cm-2). Colonies were also sampled during a seasonal increase in SST of 1. 5°C, where the density of zooxanthellae was significantly lower (from 54,710 ± 1,755 to 34,322 ± 2,894 cells cm-2) and the density of mucocytes was significantly higher (from 6,100 ± 304 to 29,658 ± 3,937 cells cm-2). These observations of coral cellular response to environmental change provide evidence to support new hypotheses for coral survival and the complex role played by mucus in feeding, microbial associations and resilience to increasing SST.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Aquatic Science