Abstract
This study was undertaken to provide biological information on the species distribution and abundance of sea stars as well as the physico-chemical status of the seawater of selected intertidal zones of Davao Gulf for sustainable use of marine resources. This study was conducted along the 10 selected intertidal zones of Davao Gulf specifically in Davao City, Philippines. Results showed a total of 2357 individuals identified. These species belong to 8 genera and 4 families of sea stars. Of these, 1842 species belong to family Astropectinidae, 484 species are under the family of Ophidiasteridae, 30 species for family Oreasteridae, and 1 species in the family of Acanthasteridae. Sampling was done from September 2010 to March 2011. The study revealed a diversity index of 28.45% using Shannon-Weiner showing low species richness and evenness. Majority of the sampling area (80%) are composed of sandy substrate while 20% have silty and muddy substrate. Of the sandy substrate, 30% of which have coral rubble, 40% have sea grasses and only 10% were observed with living corals. Species richness generally increases with increasing water quality, habitat diversity and or habitat suitability and is expected to decrease with human induced disturbance. Although statistics revealed there were no significant relationship between the number of sea star species and the physico-chemical parameters except for the BOD which recorded a much lower value compared to the criteria set by the government. Literature readings cites the possibility that the temperature might be the cause of the sudden change of BOD since temperature affects the rate of photosynthesis of plants, the metabolic rate of aquatic animals, rates of development, timing and success of reproduction, mobility, migration patterns and the sensitivity of organisms to toxins, parasites and diseases.
Highlights
Davao Gulf is a 308,000-hectare body of water, located in Mindanao, Philippines
This study was conducted along the 10 selected intertidal zones of Davao Gulf in Davao City, Philippines
A total of 2357 individuals were identified along the intertidal zones of Davao Gulf in Davao City, Philippines
Summary
Davao Gulf is a 308,000-hectare body of water, located in Mindanao, Philippines. It covers the coast of the southernmost tip of Davao Del Sur, to Davao City and Davao Del Norte and continues to line the shores of Compostela Valley (Sun Star Davao, 2011). The greatest diversity of sea stars occurs in coastal regions, as a group, they are well represented globally from the Antarctic, Pacific, Atlantic, and Indian Oceans where they inhabit mostly wave-exposed intertidal zones of coastal waters (Freeman, 2005). They are ecologically important because they can be important predators of other invertebrates like clams, barnacles and other attached marine life. Fish, birds, and other echinoderms are known to prey on sea stars They feed on arm tips, as their calcified bodies are difficult to eat and not very nutritious (Fell, 2008)
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