Browsing by Author "Wimalasiri, H.B.U.G.M."
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Item Preliminary Study of Bioluminescence Species in the Southern Bay of Bengal(Uva Wellassa University of Sri Lanka, 2016) Wimalasiri, H.B.U.G.M.; Jinadasa, S.U.P.; Dissanayake, D.C.T.; Weidemann, A.; Wijesekera, H.Marine organisms ranging from bacteria to fish make their own chemically induced light called bioluminescence, it is used to hunt, frighten predators, attract mates, communicate, or camouflage them. The bioluminescence phenomenon was studied in the southern Bay of Bengal during August 2015 onboard R/V Roger Revelle operating from Colombo, Sri Lanka. The intensity of light produced by bioluminescence spices was measured using Recoverable Bathy Photometer (RBP). The RBP recorded light intensity while free falling at a speed of about 1-1.5 m/s. Several RBP profiles in the upper 200 m were collected at six different sites encompassing a region 5 - 8N, 85.5 - 88.5E. All samples were collected in the night time to minimize interferences from other light sources. Zooplankton samples were collected using 150 1.11T1 mesh size plankton net from each location to identify light producing zooplankton species. The RBP measurements showed the existence of bioluminescent organisms in all the sampling locations and high light intensity was found up to 150-200 m water depths. Sapphirina sp belonging to the family Sapphirinidae of phylum Arthropoda was identified as one of the light emitting zooplankton species. Studies are underway to examine the luminous substances, and vertical and spatial distribution of these species, especially around Sri Lankan coastal waters. Key words: Bioluminescence, Recoverable bathy photometer, Zooplankton, Bay of Bengal.Item Sea Urchin Abundance and Diversity at Selected Locations in Southern and Eastern Coasts of Sri Lanka(Uva Wellassa University of Sri Lanka, 2019-02) Wimalasiri, H.B.U.G.M.; Balawardhana, D.G.T.C.; Haputhanthri, S.S.K.Sea urchins are a vital group of herbivores in both temperate and tropical food webs because they control macroalgal cover, and consequently influence primary productivity and phase shifts on reefs. Sea urchin gonads is a delicacy in many countries. Due to the commercial value, sea urchin has identified as a cultivable marine invertebrate species. This study aims to identify the abundance and diversity of sea urchin at five selected sites in the southern (Midigama, Kottegoda, andNilwella) and eastern coasts (Pulmudei and Trincomalee) of Sri Lanka. The study was carried out using Random transect sampling method and transects were vertical to shoreline with the length varying from 5m -20m at the selected sites to estimate the sea urchin abundance during January to August, 2018. At the field, a quadrate of 0.5m x 0.5m was laid along transects all the sea urchin species were counted within the plot. Density and diversity of Sea urchin in two regions were estimated, and their means were compared.According to the results, a total of 12 sea urchin species were detected among the five sampling sites. On the Southern and Eastern coast, sea urchin abundance is recorded as 18individuals m-2, and 10 individuals m-2 respectively. Shannon Weinner index of diversity is highest in Midigama in Southern coast than other locations. Dominant species was Stomopneustes variolaris(Black sea Urchin) both in eastern and southern regional coasts. The abundance of S. variolaris was significantly higher in the Southern Coast compared to Eastern coast (P<0.05). If Sri Lanka initiated commercial catching of sea urchins, special management measures would be needed to prevent overexploitation of sea urchins. It is recommended to study other aspects of sea urchins including reproductive biology and stock size estimation. This study would provide some baseline information for the management of sea urchin population around Sri Lanka .Item Zooplankton Studies in East Coast of Sri Lanka(Uva Wellassa University of Sri Lanka, 2019-02) Koshika, K.; Wimalasiri, H.B.U.G.M.; Jayasinghe, R.P.P.K.; Guruge, K.P.G.K.P.Zooplankton plays a vital role in marine environment by transferring the energy to higher trophic levels through the food web. However, the studies on zooplankton in the coastal water of Sri Lanka especially in the East coast are deficient. The present study was conducted to investigate zooplankton abundance in East coast of Sri Lanka in marine resources survey using the Research Vessel: Dr. Fridtjof Nansen during June to July 2018. Twenty-five samples were obtained from five transects using WP2 plankton net with 180µm mesh size. The samples were collected vertically from 30 m, 100 m and 200 m depths. In the laboratory; zooplankton was identified to the lowest possible taxonomic groups using standard keys and counted. The results revealed that zooplankton are dominated by the Phylum Arthropoda (63%), followed by Chordata (20.6%), Sarcomastigophora (7.4%), Chaetohnatha (4%), Cnidaria (2.5%), Annelida (1%), Echinodermata (0.4%), Mollusca (0.4%) and Ciliophora (0.2%). The highest (13053.57 m-3) and lowest (5747.43 m-3) abundance were recorded at transects near Mullaitivu and Batticaloa respectively. The study showed that there was no significant difference (p>0.05) of the abundance of zooplankton among the sampling stations. However, abundance of the zooplankton between shallow and offshore sampling stations were significantly different (p <0.05). The abundance of zooplankton at the depth of 100 m indicated an increasing trend towards Batticaloa. Offshore (100 m and 200 m) zooplankton abundance (2697 m-3) at 30 m depth was higher than the abundance of nearshore samples (1298 m-3). This study revealed that there are spatial variations of zooplankton in East coast of Sri Lanka and it may affect the fish production in the area. Therefore, further comprehensive studies on zooplankton are recommended to find out the possible reasons for such variations which could be useful in managing the marine environment.