Observing how the distance from the mouth of a Bahamian mangrove affects biodiversity

(1) The Browning School, New York, New York

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Mangroves are salt-tolerant shrubs that have elaborate root structures and are found on tropical coastlines. Their complex root structure, along with other characteristics, allow mangroves to filter out salt from saltwater. This filtration results in varying salinity levels throughout mangroves and can affect what type of organisms can live in mangroves. Looking at the biodiversity of different sections of a mangrove can give insight into what certain species are attracted to in their habitat. Our experiment focused on determining how the distance from the mouth of a mangrove affects biodiversity. We determined this biodiversity by selecting three sites located at different distances from the mouth of the mangrove. By using the assumption that salinity decreases as you move farther away from the mouth of the mangrove, we were able to compare each site's relative salinity with its biodiversity. At each location, we recorded all marine species and their abundance for a total of twenty minutes. From the data collected, we used a Simpson’s diversity index to calculate the biodiversity of each of the sites. We predicted that the site closest to the mouth would have the highest diversity since more animals are adapted to living in saltwater than freshwater. Once we collected the data, it was clear that the site 260 meters away from the mouth had the lowest diversity, and the sites that were 90 and 135 meters away were similar in biodiversity. We also observed that almost all of the fish found were either juvenile or under five inches, which supported our prediction that the majority of fish would be smaller because they use the compact roots as protection from predators. Overall, our hypothesis that biodiversity would be highest near the mouth was partially supported because although the 135-meter site was the most diverse, it was very similar to the 90-meter site. They were both significantly denser in biodiversity than the 240-meter site.

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