On May 22nd
2017, we visited the Old Dan Bank site. Old Dan Bank is located in a shallow open
water area, with depths of 3ft-4ft. As you approached a prop scar found within
the location, the water became very shallow. On the outskirts of the reef, sea
grass was abundant. However, there was less sea grass at this location compared
to the other locations overall. It was partly cloudy with a high of 85 degrees
Fahrenheit and a low of 79 degrees Fahrenheit*. At this site, several species
of green algae dominated the bank. However, compared to Koch Key there was a
higher green algal diversity, a lower fish diversity, and a higher coral
diversity at Old Dan Bank. This was due to the lack of mangroves at Old Dan
Bank. The lack of mangroves also meant that there was less structure in this
ecosystem. This site was shallower, less turbid, and had better light
penetration compared to both Koch Key and Old Sweat Bay. A similarity between
every location was that they all suffered from human impacts.
Many algae dominated Old
Dan Bank. The species observed included: Caulerpa
sertularioides, Halodule wrightii, Syrogodium filiforme, Thalassi testudinium,
Aurainuillea spp., Caulerpa prolifera, Anadyomene, Halimeda incrassata,
Caulerpa paspaloides, Penicillus dumetosus, Penicillus pyriformis, Udotea spp.,
Dictyosphaeria spp., and Halimeda
tuna. Aside from the green algae listed, there was brown alga present as
well. The species of brown alga was Sargassum
fluitans. The diversity of algae at Old Dan Bank could have been due to the
decreased turbidity. Decreased turbidity and lack of mangroves allows for more
light penetration and therefore, more photosynthesis can occur. Also, there was
less structure at Old Dan Bank because of the absence of mangroves.
Green alga specimen found on Old Dan Bank. |
Human impacts varied at
each location visited on May 22nd, 2017. At Koch Key, the main human
impact was fishing and littering. Many abandoned fishing lines were seen in the
mangrove branches and roots. In addition to the lines, there were many sunken
glass bottles and metal cans due to reckless behavior. As for Old Sweat Bay,
the only human impact observed on a large scale, was the dredging of the
channel. At our location, Old Dan Bank, the human impact was more severe than
the other locations. Our site was damaged by a large, recent prop scar. This
prop scar caused a loss of several coral and alga species.
At this location we were
able to observe many different species. One that was very interesting was the
upside down jellyfish (Cassiopeia cassiopeia).
Although there was very few of these species present, it is common for Cassiopeia cassiopeia to be found in
sandy bays. However, they were more abundant in mangrove forests such as, Zane
Grey Creek. This species of jellyfish obtains its food from a symbiotic relationship
with photosynthetic zooxanthellae. The upside down jellyfish feeds off of the
sugars provided by the zooxanthellae.
Cassiopeia cassiopeia photographed at Old Dan Bank by Kayli! |
Even though Old Dan Bank
was dominated by green algae, we were able to observe some diversity of
invertebrates, fishes, and corals as well. Some of the invertebrates included:
orange icing sponge, reticulated brittle star, reticulated hermit crab, turbo
snail, queen conch, conical spined sea star, Tripneustes, mantis shrimp, and loggerhead sponges. Some of the
fishes included: blue striped lizard fish, slippery dick, bandtail puffer, and bicolored
damselfish. As for the corals, there was Manicina
areolata, Porites furcata, Cladocora arbuscula, and Siderastrea siderea.
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