To address our research questions, we propose to set up two in situ mesocosm experiments in which we measure coral reef bleaching in response to different conditions for four consecutive weeks each.
The conditions in the first experiment are represented in Table 1.
We chose this experimental set up in order to test the combined effects of turbidity (high or low), cloud cover (represented by shaded and unshaded), and UV radiation (+UV and -UV) on coral reef bleaching. Using this set up, we plan to control the sea surface temperature (SST) and the temperature at the depth of the coral. DS5 multiprobes (see Image 1) will be built into the mesocosms so as to collect turbidity, temperature and radiation data from consistent locations and times without oversight. These electronic probes will also help reduce human error. Due to the extent of the controls in the experiment, we propose that it be conducted in the Virgin Islands where coral reef bleaching has been observed. Finally, the amount of coral reef bleaching will be measured by calculating the ratio of the area of bleached coral reef versus the area of unbleached coral reef.
A field experiment similar to what we are proposing was published in1993 by Gleason & Wellington in the Salvador Islands, Bahamas.
The experimenters transported coral reef species from 24m depths to 24m, 18m and 12m depths, thus increasing UV radiation exposure. They set up two conditions; the coral was either protected from UV radiation or exposed to UV radiation. They then measured the water temperature at hourly intervals.
Our experiment will effectively build on that of Gleason & Wellington by studying not only the effect of UV radiation on coral, but also other potentially confounding variables.
These variables include water turbidity, which can represent the strength and frequency of storms that effectively mix up water and its components, and cloud cover. These two additional factors represent ways in which coral is protected from UV radiation.
The conditions of the second mesocosm experiment are represented in Table 2.
The second experiment will use the same mesocosm set up as was used in experiment one, with three controlled temperature conditions. To measure the amount of bleaching, we will calculate a ratio of the area of bleached coral reef compared to the area of unbleached coral reef in each mesocosm.
Again, multiprobes will be built into the mesocosms so as to collect temperature and ambient radiation data from consistent locations and times without oversight, thus reducing human error.