Christina Nau - Coastal Ecology Field Trip Assignment

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Hillsborough Community College *

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2001C

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Geography

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Oct 30, 2023

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Christina Nau Professor Arellano OCE-2001-650 14 October 2023 Coastal Ecology Virtual Field Trip Assignment (70 points) 1. The three types of mangroves found in the Tampa Bay area are the red, black, and white mangroves. Mangroves are a protected species in Florida that help hold the ground in place, prevent erosion, and are a good habitat for marine and aquatic organisms. They all produce detritus or food for herbivore organisms, and mollusks love them. (Greely 2018) The red mangroves have prop roots that go downward, lush pointy green leaves, and propagules that hang down from the branches which enable them to reproduce. The propagules get about 6 inches in length and once they become too heavy, they break off the branches and fall into the water below to eventually root themselves in the sediment to start the reproduction process, which can start up to a year later. The red mangroves have prop roots and are the only type of mangrove that have yellow leaves, which are called sacrificial leaves, or leaves that have salt secretions on them. When these leaves fall into the water, they become food also known as detritus for the herbivore organisms that reside below. (Greely 2018) The black mangrove roots aerate upwards (pneumatophores), and they have the darkest leaves of the mangroves, dark green, that are a little pointy, but not nearly as pointy as the red

mangrove. Their leaves all secrete salt on the back side of them, and you can actually lick the leaves to taste the salt that the plant secretes onto them if you would like. They also have flowers on their branches for reproduction. (Greely 2018) Lastly are the white mangroves, which usually grow closest to the shore. They have medium-colored green leaves, which are oval-shaped and have two little salt glands at the base of the leaves, where they secrete salt that kind of look like whiteheads or pimples. They have a regular rooting system in the ground like all other trees. (Greely 2018) Some physiological adaptations in the mangroves for water uptake and conservation are through ion compartmentation, osmoregulation, the selective transport of ions, the balance between ion supplies to the shoot, and room for the salt influx from the environment. Mangroves also have salt-excreting leaves, and a thick epidermis to help with the salt and water uptake. Mangrove leaves tend to be more succulent so smaller and thicker allowing for cooling and a bigger retention to conserve water use. This is because they have well- developed large-celled water-storing tissues within them. Many species of mangroves contain salt glands in or on their leaves, which allows salt to be secreted on them. The lower leaf surface is said to have dense covered hairs which raise the secreted saltwater droplets away from the leaves surface to prevent osmotic withdrawal of water. Therefore, the leaves may thicken with high salinity content in the surrounding area. Root elongation and the suberization of cell walls also avoid salt to help maintain water, as root elongation maintains room in the plant. Most mangroves have a thick-walled epidermis alongside a waxy cuticle and sunken stomata, which reduce water loss through the stomata and salt glands. Overall, to regulate water uptake, mangroves have thickening of leaves to have a greater retention time

for leaf nitrogen and to conserve water efficiently, so as saltwater salinity increases, their water conservation rises as well. (Parida and Jha 2010) The three salt-eliminating mechanisms mangroves use to live in saltwater are salt secretion, salt exclusion, and salt accumulation. Salt-excluding mangroves eliminate excess salt by an ultrafiltration mechanism at the root cell membranes. Salt-secreting mangroves regulate internal salt levels by secreting excess salt through glands, which sometimes results in salt deposits on their leaves. Lastly, salt accumulators accumulate high concentrations of salts in their cells and tissues to avoid salt damage by sequestering ions to the vacuoles in the leaf, translocation outside the leaf, cuticular transpiration, and efficient leaf turnover to salt shedding. (Parida and Jha 2010) 2. The mangrove environment consists of mangrove trees that shed salt-covered leaves which become food once broken down for organisms such as decomposers and bacteria that live below. The ground surrounding mangroves is very soft, so soft that your feet may sink, which is common near mangroves that have prop roots, such as the red. Mangroves do not have fast-moving waters or big waves, rather they have stiller water so they can stabilize themselves better. On the other hand, the low-energy beach environments have very little to no vegetation near the water, but some upland a little bit. In mangrove habitats, there are the mangroves themselves, as well as seagrasses in the surrounding area, so a bountiful amount of vegetation. All beaches along the Gulf Coast are considered low energy because of how low their wave heights are. Their waters produce small, ripple-like waves, unlike the beaches on the East Coast of Florida or in California that are high-energy, and you can surf on them. In low-energy beach habitats, there is not much fine mud or silt, but rather coarser, larger

sand particles and crushed shells, so that is why soft-bodied animals do not reside there since they prefer finer-grained mud and silts like in the mangrove habitat. We would therefore expect less diversity in the low-energy beach environment than in the mangrove or seagrass communities. Both the mangrove and low-energy beach environments contain water that is oxygenated and slow-moving, as well as rich sediments even though their contents differ. (Greely 2018) To test the mangrove core, Dr. Greely took a PVC pipe which she pushed into the sediment to collect a sample right next to the mangroves. The sample was not evenly stratified, as there were a lot of water, different size grains, and difference in coloration, showing lots of inorganic and organic processes. At the surface, where the water meets the sediment, you will expect the highest oxygen concentration. As you go deeper into the core, darker materials and grains occur, which is known as organic composition. A lot of leaf and plant material is directly near mangroves, which creates this organic breakdown. That also means that there is less oxygen as you get deeper into the core, which releases hydrogen sulfide. Bacteria break down the plant material within the sediment which is then reused by the plant again. Once she got this core sample, she moved a couple of yards away from the mangroves to collect another sample. While push-coring, she could immediately smell the release of the hydrogen sulfide gas. Upon examination, the sediments are of a lighter shade and there is not as much dark organic matter and a lot more shell material. She also noticed some worms in the sample. Lastly, she took a final core sample far away from the mangroves near a seagrass bed. Here, there were lots of very dark organic breakdowns, but from seagrass and not mangroves this time. She noticed that the layering was darker and darker as

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