Theses and Dissertations

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    Density Distribution and Factors Influencing Sea Stars in Selected Islands of Lakshadweep India
    (Wildlife Institute of India, Dehradun, 2013) Jayaram, Sharmila; Hussain, S.A.; Gopi, G.V.; Apte, Deepak
    Coral reefs are the most fragile, complex and diverse ecosystem on earth. But recently, they arc under severe threat due to both natural (climate change, storms and disease outbreaks) and anthropogenic factors (overexploitation, coastal developmental activities and pollution). As evident from earlier studies, a major factor causing degradation of coral reefs is due to an asteroid species belonging to phylum Echinodermata which is considered second to storm damage. Thus to analyze the condition in Lakshadweep Islands I assessed the density of asteroids in four Islands of Lakshadweep. It was found that the five species detected belonging to three families (Oreasteridae, Linckiidae and Acanthasteridae) were having varied density across the four islands. Overall density estimates of the asteroids ranged from 0.05(S.E = 0.02) to 0.80(S.E = 0.09) per 250 square meter. The asteroid density was highest in the uninhabited Island named Bangaram. Correspondence Analysis (CCA) showed that major gradients in environmental variables influenced asteroid species distribution. Sample scores on ordination ' axis 1 were strongly correlated with water pH, water depth and dead coral. Out of the three strongly correlated environmental variables pH was found to be the most ecologically important variable that affects the asteroid distribution. Corallivorous asteroid population outbreaks are becoming a boon to the coral reef ecosystem all over the world and contribution of water pH variation of this outbreaks are being studied well. Thus management strategies in Lakshadweep Islands that 'accounts the variation of water pH are required to conserve the coral reef ecosystem.
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    An Investigation of the Relationship Between Green Turtle (Chelonia mydas herbibory and Seagrass in the Agtti Lagoon, Lakshadweep
    (Wildlife Institute of India, Dehradun, 2007) Lal, Aparna; Choudhury, B.C.; Sivakumar, K.
    Globally, nearshore ecosystems are being increasingly impacted upon by expanding coastal development. The almost complete dependence of marine mega herbivores like Green Turtles (Chelonia mydas) on these habitats for food together with their current low population levels in many regions highlights the need to understand this vital relationship. This study was an attempt within this framework. It aimed to quantify the intensity and potential impacts of Green Turtle grazing on the seagrass Cymodocea rotundata in the Agatti Lagoon, Lakshadweep. To map the habitat types in the lagoon, points generated from a grid were used, while 23 transects, perpendicular to the shore, formed the basic sampling unit to assess turtle density and map their distribution patterns across the lagoon. The study recorded exceptionally high turtle abundances within the lagoon with their distribution patterns being restricted to certain areas within the seagrass meadow. The magnitude and potential impacts of herbivory were quantified across the established gradient of turtle density in the lagoon. It was found that C. rotundata plant parameters like morphology, life history strategies, population dynamics and meadow level characteristics were significantly different in areas with less turtles, indicative of a response to turtle grazing, results supported by experimental evidence. It was found that increased shoot recruitment rather than increased shoot production could be a mechanism whereby seagrass deals with intense herbivory. This study shows that grazing intensity is an important factor potentially regulating the response of seagrasses to grazing.