Toxicity evaluation of surface waters from artificial lakes (Shihwa, Asan, Busa) and Mankyung river using sea urchin (Strongylocentrotus nudus) sperm and embryo

Abstract

The demand for lands in Korea caused active reclamation of shallow coastal areas including tidal flats. As a consequence of coastal reclamations, artificial lakes were formed between the mouth of river and sea, which prevents the exchange and mixing of water mass and its dissolved and particulate components between river water and seawater. River water does not flow directly to the sea but stay for some time in artificial lake. The only chance for this lake water to flow out and to contact with seawater is the sluice operation of water gate. Therefore, the water quality of lake water tends to be influenced by the water quality of inflowing river water. If the lake water is contaminated by the river water, it subsequently affect the sea water and marine ecosystem. In other words, the water quality of lake water before being discharged to the sea is crucial for the environmental safety of nearby coastal ecosystem. Here, we set the purpose of this study to know whether there are adverse effects in lake water to marine organism. We evaluated the toxicity of surface water from Lakes Shihwa, Asan, Busa, and Mankyung River using sperm and embryo of a sea urchin, Strongylocentrotus nudus. To enable the toxicity test of freshwater with marine organism, salinity adjustment technique was applied. In general, the proportion of fertilized eggs and normally developed larvae increased as the salinity of sample increased. In fertilization test, the fitting curve of Lake Shihwa sample located higher than that of control (artificial seawater), but those from other samples lower. Surface water from Mankyung River showed the highest toxicity among samples tested in this study. In development test, samples from Lakes Shihwa, Asan and Busa showed similar trends and the adverse effects were slight. But, in Mankyung River water, the highest rate of development was only 10.7%, indicating great adverse effects on the development. Consequently, it is necessary to improve the water quality o