Analysis of Water Quality and Eutrophication Status of Artificial Lakes on Campus:A Case Study in Tibet University

In this paper,the artificial lake on the campus of Tibet University was taken as the research object.By detecting the water quality of the lake,the standard index method and comprehensive pollution index method were used to understand the water quality characteristics,pollution status,and main pollutants of the Siyuan Lake.On this basis,the comprehensive nutritional status index method was used to evaluate the eutrophication status of the Siyuan Lake.The results showed that the overall water quality of the artificial lake was good,showing as still clean,with TN and TP being the main pollution factors of the artificial lake.The main nutritional indicators were TN,TP,and transparency,with a comprehensive nutritional level of middle eutropher.Based on the environmental characteristics of the artificial lake area on the campus of Tibet University,reasonable treatment measures have been proposed.It hoped to prevent and improve the water environment through these measures,and provide reference for the protection and restoration of campus landscape water body.

Feeding Ecology and Establishment of the Naturally-Colonized Freshwater Cichlid, Sarotherodon galilaeus (Pisces: Actinopterigii: Perciformes) from a Man-Made Lake, South-Benin, West Africa

The freshwater cichlid, Sarotherodon galilaeus (Linné, 1758) is an economically and commercially important fisheries species that has naturally colonized and dominated a sand-dragged man-made freshwater lake of Ahozon (South-Benin) where the species made about 85.21% of the fish community. We investigated the feeding ecology of S. galilaeus in order to evaluate resource exploitation and the establishment of this species in Lake Ahozon. During wet, flood and dry seasons, 1189 individuals of S. galilaeus have been monthly sampled in the open water and in the aquatic vegetation habitats. The study showed that S. galilaeus consumed about seventy (70) food items dominated by algae (52.88%) composed of 28 families and 52 genera from blue-green algae, green algae, desmids, and diatoms, sand particles (23.95%), detritus (12.27%) and protozoans (7.68%). Minor preys were rotifers, copepods, cladodera, crustacea and insect parts. Foods items with higher diet occurrence were sand particles with a percentage occurrence of 72.33%, detritus (69.47%), and some algae such as Scenedesmus (58.96%), Closterium (55.68%), and Microcystis (51.30%). Significant (P ≤ 0.05) ontogenetic variations of empty stomachs were recorded. S. galilaeus exhibited a wide diet breadth (DB) ranging between 5.55 and 7.29 that tended to increase with fish sizes. Diet overlaps (Øjk) varied from 0.77 to 0.97, indicating high diet similarities between different life stage categories. The slope b = 0.560 obtained from Log (body weight)-Log (gut length) linear regression, and the mean ratio of GL/SL = 6.72 ± 2.23 support our findings that S. galilaeus exhibited detritivorous, herbivorous and omnivorous food habits. The broad spectrum of food resources consumed/utilized and the high diet breadth recorded leading to allometric growth, the active breeding and the high propagation of the species, were some indicators of the successful establishment of S. galilaeus in the man-made lake of Ahozon. Sustainable fisheries/ aquaculture exploitation of S. galilaeus and successful valorization of the man-made lake of Ahozon require an integrated management of the lake including the prevention of domestic waste dumpings, the protection of the foraging and spawning grounds, the fertilization of the lake, the introduction of predators to control the population of S. galilaeus , the protection of lake margin to avoid erosion, a planned harvest of the fish stock and a periodic ecological monitoring of Lake Ahozon.