Studies on methods for management of tropical lake ecosystems under human impact

在宋卡湖（Thale Sap Songkhla） 7个测点对塞奇盘深度、水温、盐度、pH、养分、有机质、重金属、DO、SS、叶绿素、浮游生物、底栖生物和浮游植物的光合作用进行了调查。湖水浑浊度很高，这是由于悬浮物浓度很高，影响了水质的准确分析。水温为28-31ºC， DO为6-8 ppm， pH为7-9，盐度为0- 33% C，浮游植物叶绿素a主要为2-18 mg/m^3（12月份为18-45 mg/m^3）。浮游植物的光合能力较高，为25 ~ 30 mgO_2/chl。一毫克/小时，在某些情况下有光抑制作用。底栖动物各站点共发现31种，单个站点发现5 ~ 15种。个体密度为120 ~ 1170只/m^2。与内陆海和沿海地区的正常水平相比，物种数量和个体密度偏低，特别是密度为内陆海和沿海地区正常水平的1/10至1/100。多角动物、软体动物和甲壳类的种类数量几乎相同，从生物地理学的角度来看，它们大多是在印度太平洋地区发现的热带和亚热带物种。它们大多是滤食性的，只有少数种类是杂食性和肉食性的。底栖生物生物量在湖的中部和西部较高，而在湖的东部和与外海相连的河道中较低，表明后者受到盐度变化和水流的环境压力。悬浮物含量为44 ~ 127 mg/l，燃烧损失为12 ~ 19%，表明湖水底泥重悬浮作用明显。重金属中Mg （49.6 ppm）、Ca （19.8 ppm）、Si （5.10 ppm）和AI （1.30 ppm）含量较高。

In Songkhla Lake (Thale Sap Songkhla), Secchi disc depth, water temperature, salinity, pH, nutrients, organic matter, heavy metals, DO, SS, chlorophylls, plankton, benthos and photosynthesis of phytoplankton were investigated at 7 stations.Turbidity of lake water was very high, which resulted from very high concentration of suspended solid and disturbed accurate analyses of water quality. Water temperature was 28-31ﾟC, DO 6-8 ppm, pH 7-9, salinity 0-33 % C, and phytoplankton chlorophyll a mostly 2-18 mg/m^3 (18-45 mg/m^3 in December). Photosynthetic capacity of phytoplankton was comparatively high, 25-30 mgO_2/chl. a mg/hr with photo-inhibition in some cases.As for benthic animals, 31 species were found all through the stations, 5-15 species at a station. Indivisual density was 120-1170/m^2. The number of species and individual density were low as compared with the normal levels found in inland seas and coastal areas, especially the density being 1/10 to 1/100 of the level in those areas. Polychastes, molluscs and crustaceans were found almost in the same number of species, and from biogeographical viewpoint most of them are tropical and subtripical species found in the Indo-Pacific areas. They are mostly filter-feeders, and only a few species are oninivorous and carnivorous. Benthos biomass was high in the central and western part of the lake and low in the eastern part and the channel connecting the lake with open ocean, suggesting the environmental stress due to salinity changes and water flow in the latter areas.Suspended solid was 44-127 mg/l and the ignition loss was 12-19%, suggesting prominent resuspension of bottom sediment in lake water. Among heavy metals Mg (49.6 ppm), Ca (19.8 ppm), Si (5.10 ppm)and AI (1.30 ppm)were abundant in lake water.