Environmental Management
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Item Herpetofaunal diversity and endemism in a fragmented forest patch: a study in Dombagaskanda forest reserve(2023) Sandeepa, S. P. M.; Chandrasekara, W. U.Fragmented forest patches provide refuge for distressed animal forms including amphibians and reptiles (herpetofauna) but an array of adverse anthropogenic impacts often threatens them. Surrounded by human settlements, the Domabagaskanda Forest Reserve (DFR) is one such small, threatened, fragmented forest patch (area 192 ha) in the wet zone of the country. In this research, we studied the variation of the herpetofaunal diversity along a seasonal and spatial scale in the DFR and evaluated their endemism and conservation status against the National Red List 2012 of Sri Lanka. The research design included surveying herpetofauna within (viz. forest zone and monastery zone) and around the DFR (viz. outer buffer zone) during the wet season (November to December 2022) and dry season (January to March 2023) using a quadrat sampling strategy. The herpetofauna diversity in these three zones was calculated using the species richness (SR), Shannon-Weiver index (H’), and Pielou’s evenness index (J’). The canopy cover, air and soil temperature, humidity, and tree diameter in the quadrat sampling areas were also measured. A total of 125 individuals belonging to 14 reptilian and 11 amphibian species were identified. They showed a distinct spatial variation where their total abundance and diversity within the monastery zone were greater (N=40, SR=14, H’=2.507, J’=0.9501) than in the forest zone (N=26, SR=13, H’=2.418, J’=0.9427) and the peripheral buffer zone (N=21, SR=9, H’=1.934, J’=0.8801). They also showed a seasonal variation where their total abundance and diversity were higher during the dry season than in the wet season. Five (05) reptile and 08 amphibian species were endemic to Sri Lanka, representing 42% reptilian and 73% amphibian endemism. The endemism percentage (%) of herpetofauna within the DFR is 56.5%, which is 13 times higher than that in the outer buffer zone (4.6%). Of the 05 endemic reptile species, 02 are endangered, whereas of the 08 endemic amphibian species, 04 are endangered. Despite its small size, results suggest that the DFR is a rich biodiversity repository with a high herpetofaunal endemism, of which most are endangered. Results also insist on the grave need to protect and conserve small, fragmented forest patches, similar to DFR, from further human threats.Item Variation of water quality parameters and brush park fish diversity: a study in Negombo estuary(2023) Ratnayake, R. P. P.; Chandrasekara, W. U.In the Negombo estuary, the brush park fishery is confined to two small zones along its Eastern Katunayake side and the Western Dungalpitiya side, with approximately 50 brush parks each. In this research, we investigated what factors, whether seasonal or water-quality related, contributed to the brush park fishery being confined into these two zones. Three (03) randomly selected brush parks were sampled from each zone during the rainy season (November to December 2022), and the fishes in each brush park were identified to the maximum possible taxonomic category and enumerated separately. Further, the water quality parameters within those selected brush parks were measured using standard field and laboratory procedures. This procedure was repeated for another set of 03 brush parks in each zone during the dry season (February to April 2023). The fish diversity in each brush park was calculated using the Shannon-Weiver (H’) and Pielou’s evenness (J’) indices. Fish abundance data and water quality data between the two zones and between the two seasons were analysed parametrically and nonparametrically as appropriate. Altogether, 18 taxa belonging to 16 finfish and shellfish families were recorded. Of the water quality parameters measured, the salinity, electrical conductivity, dissolved phosphates, and Ch-a increased significantly at both zones during the dry season. These water quality changes induced many marine species, including Siganus sp. and Acanthophagous berda to migrate into the two zones, resulting in Siganus sp. contributing about 42% and Acanthophagous berda contributing about 33% of the fish catch at Dungalpitiya and Katunayake, respectively. When the salinity, in particular, dropped near zero in both zones during the rainy season, these marine species migrated back. The same salinity drop induced the freshwater Macrobrachium rosenbergii to migrate into the two zones in large numbers during the rainy season, contributing about 61% and 30% of the fish catch at Katunayake and Dungalpitiya, respectively. It was apparent that M. rosenbergii dominates the brush park fish catch during the rainy season, while the marine Siganus sp. and A. berda dominate it during the dry season. The brush park fish diversity was higher in both zones during the dry season than in the wet season. For example, the SR, N, H’, and J’ at Katunayake during the dry season were 15, 425, 1.651, and 0.6098, while 7, 87, 0.5189, and 1.01 during the wet season. Results also suggest that the seasonal and zonal changes of salinity, dissolved phosphates, and Ch-a govern the brush park fish diversity in the Negombo estuary.