Coral reefs in the Caribbean are under threat due to atrocities such as coral bleaching and disease. The growth and maintenance of the surviving population is dependent on sexual reproduction and the survivorship of the juvenile coral (Irizarry-Soto et al, 2009). Coral are able to reproduce by spawners and brooders (Irizarry-Soto et al, 2009). However, reproduction of corals can be difficult due to them being sensitive to their environment. This study seeks to look at the how the composition in juvenile corals vary across the different reefs and depths, to look at the juvenile survivorship and recruitment, and to compare the strategies of the successful coral survivors. It is hypothesized that the broadcasting species will have low recruitment and low survivorship than the brooding species (Irizarry-Soto et al, 2009).
To conduct this study, they tested the coral west of Puerto Rico in the La Paraguera Natural Reserce where there is a coral reef. To test the juvenile abundance and survivorship they surveyed a long a gradient where they were able to identify the coral using a criterion that determined the genus and species (Irizarry-Soto et al, 2009). They were able to determine Juvenile colonies that had sexually reproduced by looking at the fragments. They also used a criterion that was based on size that is based on the species found and the average size (Irizarry-Soto et al, 2009). Every time that there was a potential juvenile found they observed the surroundings and took pictures so that they could map where it was located. The juveniles that were able to be identified were counted in quadrats and each quadrat was photographed and mapped out.
To analyzed the data, they went surveyed the differences in juvenile coral densities from August of 2003 to August of 2005, using the repeat measurement ANOVA. To analyze the differences in survivorship they compared the differences among sites with a g-test of independence contingency table. To analyze the difference in survivorship based on reproduction they again used a g- test and contingency table.
Overall there was a survivorship of 54.9% of the all of the reefs tested. It was found that the brooders have a lower survivorship than the spawners (Irizarry-Soto et al, 2009). Looking at the survivorship of the different reefs, Enrique reef had a high survivorship. Pelotas had a low survivorship as there was a decrease from 2003 to 2005 but there was no change in densities of the coral. Turrumote had a high survivorship but a decrease in the densities. The lowest of survivorships was in Media Luna and the densities there decreased heavily as well. At Weinberg, there was a high survivorship and at El Hoya there was a high survivorship but coral densities decreased. Overall there was a decrease in juvenile densities from 2003 to 2005 but survivorship varied (Irizarry-Soto et al, 2009). It was found that it was four times better for spawners to survive in deep habitats than the brooders and brooders were better in shallow habitats (Irizarry-Soto et al, 2009). For recruitment, there was a low successful recruitment from 2003 to 2005. The Highest recruitment was in Media Luna with Weinberg coming in second. It was found that the species that had the highest recruits were less susceptible to bleaching (Irizarry-Soto et al, 2009). There was no pattern found between reproduction and recruitment. This study was conducted accurately, however as it concluded, the success of reproductive or recruitment should be done over a longer period of time so the time frame could have been extended. There could also be more information on the strategies of successful coral survivorship. The purpose of the paper was to assess juvenile coral survivorship overall the period of two years.