The Mutualistic Symbiosis Between Zooxanthellae And Stony Corals

ABSTRACT: The mutualistic symbiosis between zooxanthellae and various stony corals originating from the order Sscleractinia, has been researched using various different methods. These methods are used to determine the role of zooxanthellae in symbiotic relationships with their host coral, in varying conditions. In 1979, K.M. Kevin & R.C.L Hudson determined the role of zooxanthellae and in Plesiastrea urvillei, a species of stony coral found in cold waters, and the significance of the symbiosis by testing response to calcification initiated by different nutrition levels and different light settings. In 1985, Esther C. Peters and Michael E.Q. Pilson used different levels of sedimentation on corals, from the species Astrangia danae, with symbiotic

Stony corals, including those from the order Scleractinia, are the base or building blocks of coral reefs. Without this symbiosis, reefs would not be the way they are today, they wouldn’t be able to sustain much life. The fact that this symbiosis exists between two organisms from different kingdoms, corals from animalia and zooxanthellae from plantae, makes the symbiosis intriguing. This relationship is known as a mutualistic symbiosis, in which providing each other with the necessities for them to not only survive, but also thrive, benefits both coral and zooxanthellae. “The symbiotic association between coral and its zooxanthellae must meet the different trophic requirements of the participants and be to their mutual benefit” (Kevin & Hudson 1979, pp. 166). The coral provides the zooxanthellae with a “protective habitat, carbon dioxide and nutrients needed for photosynthesis” (Zhao & Yu 2014, pp. 165), and in return the host coral is provided with food produced by the zooxanthellae through photosynthesis (Zhao & Yu 2014). To understand the importance of this relationship between organisms from different kingdoms, copious amounts of research has been done, which has broadened the current knowledge on this symbiosis. Due to the diversity of the methods and experimental techniques and species of stony coral with symbiotic zooxanthellae has lead to many

KEVIN, R.C.L HUDSON research, ESTHER C. PETERS, MICHAEL E.Q. PILSON used a stressful environment to look at the symbiosis between host coral and zooxanthellae. In this case, the symbiosis looked at was between the species of stony coral Astrangia danae and its symbiotic zooxanthellae and its response to the effects of heavy sedimentation. This was compared to the response of specimens of Astrangia danae without symbiotic zooxanthellae under the same conditions of heavy sedimentation. Four different conditions were tested; asymbiotic Astrangia danae covered in sediment, and some without, and symbiotic Astrangia danae some covered in sediment, and some without. The ones without sediment cover were used as controls. Symbiosis was measured by the symbiotic index. For the symbiotic control coral, the mean index was constant throughout the experiment (Peters & Pilson 1985). As for the symbiotic corals exposed to sediment, the index increased in the first 4 weeks, when sediment was applied once per day, and then dropped slightly as the sedimentation load increased to three times per day, and there was no increase in the zooxanthellae densities (Peters & Pilson 1985). However for both asymbiotic groups, the zooxanthellae densities increased during the entire experiment (Peters & Pilson