Artemia Occurrence, Salinity and Ionic Rates in Saline Crater Lakes of Western Uganda

摘要

Seven selected saline crater lakes in Western Uganda were surveyed for Artemia occurrence, salinity and ionic rates both in the wet and dry season. The Studied lakes included lakes Katwe, Munyanyange, Nyamunuka, Murumuri, Bunyampaka, Bagusa, and Kikorongo. In the field cyst-like materials along the lake shores and foam suspected to have Artemia cysts from the surface of each of the studied saline Crater Lake were collected in a plastic sample bottle. Presence of cysts was examined using the density separation technique. A zooplankton net of 50μm was used to filter water samples to be used for analysis of presence of Artemia biomass. Water samples for ionic composition analysis were taken from at least three geo-references points on each of the studied lakes. In-situ measurements of salinity were taken at each point of sample collection in each of the studied lakes. In the laboratory, collected water samples were analysed following APHA standard operating procedures. Seasonal differences in salinities and ionic rates within the studied lakes were tested for significance using a two tailed, paired t test. All the studied lakes had neither Artemia cysts nor biomass at the time of sampling both in the dry and wet season. Both in the dry and wet season, the salinity in all the study lakes was much higher than that of sea water while the ionic rates of Cl^-/SO₄^2- , Cl^-/Na⁺ + K⁺, and Mg²⁺/Ca²⁺in all the study lakes were all less than that of sea water (table 1 & figure 2). The dry season salinity of all the study lakes was found to be significantly higher than the salinity in the wet season (t-value = 0.0205). There were no significant seasonal differences in the ionic rates of Cl^-/SO₄^2- , Cl^-/Na⁺ + K⁺, and Mg²⁺/Ca²⁺in the studied lakes with t-values of 0.5665, 0.4082 and 0.4523 respectively. There is need for continuous monitoring of these saline lakes for the presence of Artemia resources since many other factors like temperature, the presence of wading migratory birds reported to be the dispersion agent for Artemia were witnessed in these lakes.