Coral reefs
We visited three different coral reef sites on Monday: the 11 Foot Mound reef, Long Key Ledge, and the "Elbow" Reef. 11 Foot Mound, as the name suggested, featured a mountainous like region of hard corals that was approximately 11 feet deep. The second location, Long Key Ledge, featured almost a ecotone, or a place where two biomes meet: the open ocean, and a coral reef. The third location, "Elbow" Reef, was different still. Characterized by the greater depth, we saw more open ocean fish. Based on observation, we decided the biodiversity increased throughout the sites, respectively.
On Wednesday, we visited an artificial reef, which had a surprisingly high percent coverage of coral, covering the pieces of the old Seven Mile Bridge almost entirely. However, where there was not concrete, the bottom substrate was sand, so the reef could be considered "patchy." This site was similar to the "Elbow" Reef we visited on Monday, and we saw a 9 ft Nurse shark!
By far, the most impressive reef was that of Looe Key. It was far more diverse, extensive, and had the greatest coverage of any site. We performed a quantitative assessment of the fish species there, but never got to analyzing the data. Visually, however, the increase in diversity was obvious.
In general, coral reefs are highly productive due to the large base of primary producers due to the symbiotic relationship that the corals have with photosynthetic zooxanthellae. Because of this, coral reefs support the greatest diversity we saw in any of the sites we visited.
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| A butterflyfish and characteristic substrate of Looe Key Photo taken by Lauren Wiley |
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| Picture shows a good representation of the ocean floor of the artificial reef |
Mangrove Forests
The mangrove forests of Koch Key were vastly different from coral reefs, marked by the differences in primary producers. While the primary producers in the coral reefs were microscopic zooxanthellae, the base of the food chain in the mangrove community were vascular plants, or the mangroves themselves. A staple component of this environment is the detrital food web, and it serves as a nursery for juvenile fish. There were far less colorful fish here, and there was less diversity. Most of the fish we saw were schoolmasters and juveniles of other species. The water is significantly more murky, a byproduct of the detrital processes, and there was significantly more macroalgae. While the clear waters of the reef make the environment almost oligotrophic, the turbid waters characteristic of the mangrove community are nutrient rich.
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| The murky, tannic acid stained waters underneath the mangrove prop roots provide a perfect habitat for many juvenile fish. Photo taken by Lauren Wiley |
Others/Sub-Components of the Habitats
The site we visited on Tuesday, Big Sponge, was characterized by high wave energy and, as the name suggests, sponges. There were large amounts of macro algae, especially Penicillia, Halimeda, and Udotea. My classmates and I were surprised at the diversity of this sandy bottomed habitat, and many species including angelfish, butterflyfish, trunkfish, and more were identified. Additionally, numerous juvenile lobster were seen hiding in the massive vase and barrel sponges. Because of the large amount of macro-algae found in the site, this site could be characterized as a macro-algae habitat, along with the site just off the coast of KML, which also contained a lot of seagrass. Seagrass and algae compete with one another, and as we learned at the Vester Marine Lab, each group has specific preferences and advantages over one another. Seagrasses prefer clear water, and they are good at trapping and holding sediment in place. Macro-algae, on the other hand, thrive in nutrient rich environments and are more short-lived. Both habitats were seen at these sites throughout the week.
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| Lots of Lobster at Big Sponge! Photo taken by Lauren Wiley |
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| Seagrass Bed and a Trunkfish! Photo taken by Angelina D. |
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