Blog By Laura Wardrop and Antonio Aidan Arruza
Our first day at the Keys Marine Lab in Long Key, Florida was spent on a boat snorkeling in the warm water, and exploring different sites. This report is on what we observed at the location Old Dan Bank, and how it compares to the other two locations we saw today.The first location we went to was Koch Key, a mangrove island in the middle of Florida Bay.The second location was Old Dan Bank, a bank of sand and vegetation lining part of the waterways in Florida Bay.The third and last location of the day was Old Sweat Bank, a bank of seagrass lined next to one of the channels of Florida Bay.
The substrate of Old Dan Bank is composed mainly of shells. In contrast, Koch Key had substrate consisting of fine silt and Old Sweat Bank had shells mixed into the little amount of silt that was present. The silt of Koch Key was formed from the decomposition of leaves from the mangroves. The shells and sand of Old Dan Bank consist of the calcareous remnants of animals with exoskeletons and calcareous algae. The sediment of Old Sweat Bank also has calcareous remains, but not to the same extent of Old Dan Bank. Neither Old Dan Bank or Old Sweat bank have silt in the substrate, since the seagrass floats away after it dies off due to the current. Overall, this taught us about each environment as a whole, how it works, what influences it, and through comparisons we are able to draw these interesting conclusions.
|Porites furcata, Thalassia testudinum, and Holopsamma helwigi (not certain)|
|Purple caribbean anemone|
The biodiversity of invertebrates at Old Dan Bank was relatively high. To name a few, we saw purple caribbean anemones, tulip snails, cushion stars, brittle stars, and Echinometra lucunter (rock-boring urchin). An important aspect to note is how corals, sponges, and seagrass are mixed together here at Old Dan Bank. This adds more variety for critters to hide, find food, and live. Interestingly, biodiversity of corals was higher here compared to Koch Key but lower compared to Old Sweat Bank. We think competition for space is why we have a lower number of them here than at Old Sweat Bank. Koch Key had less corals because they are unable to attach to the silty substrate of the mangrove ecosystem. The depth here was around four feet with visibility being better than that of other sites like Koch Key. Allowing the seagrass and alga to receive more sunlight, therefore increasing the primary productivity of the ecosystem. Since we only had one dive at each location we did not have enough information to see which trophic cascades impacted the area.