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Browsing Other University Publications by Subject "Abundance"

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    Assessment of zooplankton abundance in relation to water quality parameters: a case study in Magalla reservoir in the Northwestern province of Sri Lanka
    (Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Abeysinghe, A. M. P. M.; Perera, H. A. C. C.; Hewageegeana, N.
    The study was conducted in the freshwater reservoir Magalla in Nikaweratiya, Sri Lanka. The aim of the study was to assess the abundance of zooplankton in relation to selected water quality parameters. Four sampling sites were chosen; site 1 - wastes were added by nearby residences, site 2 - a bathing area, site 3 - receiving urban wastes, and site 4 - minimally disturbed (Reference site). Sampling was carried out once a month from May to December 2023. Standard methods were used for in situ analysis of water quality parameters, including water temperature (°C), dissolved oxygen concentration (mg/L), pH, total dissolved solids (mg/L), electrical conductivity (μS/cm), salinity (%) and transparency (cm). Zooplankton was collected using a 300 μm plankton net, preserved in 5% formalin and observed using a Sedgewick-rafter counting slide under a light microscope. Data were analysed using Minitab software (Version 19). According to Principal Component Analysis, water transparency, total dissolved solids and temperature were highest in sites 1 and 2, conductivity and salinity were highest in site 3 and dissolved oxygen concentration, and pH were highest in the reference site. Nineteen zooplankton species belonging to five main groups, namely, protozoa, ostracodes, cladocerans, rotifers, and copepods, were identified. Zooplankton abundance peaked in July and August, with the highest values observed at the reference site, while sites impacted by waste had significantly lower abundance. Zooplankton abundance plummeted in October and November, with the lowest values observed at site 3, which was contaminated by waste. The abundance of zooplankton at sites 1, 2, and 3 differed significantly (p < 0.05) from the reference site, and there was no significant difference among the three sampling sites according to the Kruskal Wallis test and Mann-Whitney U Test. This study revealed the effect of water quality parameters on the abundance and diversity of zooplankton in the Magalla reservoir, highlighting the importance of maintaining optimal water conditions to support a diverse and healthy zooplankton community.
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    In situ investigation of microplastic-associated bacterial communities in surface water of Kandy lake, Sri Lanka: abundance, composition, and bacterial diversity
    (Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Welagedara, W. K. H.; Gunathilaka, H. M. S. A. T.; Jayarathne, L.; Magana-Arachchi, D. N.
    Microplastics (MPs) have become a major concern due to their widespread environmental presence. Kandy Lake, a renowned landmark in the heart of Kandy, suffers from severe pollution. This study focused on MP contamination in Kandy Lake and aimed to characterize associated microorganisms. Water samples were collected from Kandy Lake: six samples from inlets and two samples each from the lake and the main outlet. From each collection point, a 100 mL sample was collected and filtered through a 5 mm metal sieve, followed by Whatmann Glass Membrane filters (0.7 μm nominal pore size). Microplastic particles were manually sorted and identified based on their morphological characteristics. Particles were then transferred to autoclaved distilled water and shaken for 1 hour at 170 rpm in an orbital shaker to detach bacterial cells. These MP suspensions were cultured on Luria Bertani agar and incubated at 37 °C for 24 - 48 hrs to isolate bacterial cultures. Genomic DNA was extracted from pure cultures using a modified cetyltrimethylammonium bromide method and amplified using universal bacterial primers targeting the 16S rRNA gene. A commercial sequencing service sequenced the amplified DNA products and deposited them in GenBank under accession numbers PP708094–PP708113. The average abundance of MPs ranged from 11.6 - 13.0 MP particles/L, with the highest concentrations observed at the lake's outlet. Raman spectroscopy data from the inlet and lake sites identified polystyrene as the predominant type of microplastic, while polypropylene was the dominant type at the outlet. Surface water samples were dominated by fibres, together with black-coloured MPs ranging from 3 - 5 mm in size. The cultured bacteria yielded 20 identified species, classified into four major groups. Six were identified as potential pathogens, belonging to the genera Bacillus, Achromobacter, Stenotrophomonas, Acinetobacter, Burkholderia, and Serratia. The study reveals a significant presence of microplastics in Kandy Lake, which carry potential pathogenic microorganisms, highlighting the exigency for intervention to address microplastic pollution in the lake.