Abstract:Human activities have aggravated the offshore ecologic environment in the Liaodong Bay and endangered aquatic bioresources in these areas. The Liaodong Bay used to be an important fishing ground and the habitat of a variety of fish species such as Larimichthys polyactis, Trichiurus lepturus, and Fenneropenaeus chinensis. However, in recent years the fish resources have been diminishing because of water pollution, over-fishing and other human activities. Sustainable development is the key to healthy marine economy, which depends on good marine ecological environment. In this study we evaluated the offshore surface water quality of the Liaodong Bay by analyzing 18 samples collected in three consecutive seasons in 2013 including May (spring), August (summer), and October (autumn). We monitored the concentrations of six typical metallic pollutants (Cu, Pb, Zn, Cd, Hg, As) and employed the Nemerow Pollution Index and the Comprehensive Quality Index to evaluate the degree of heavy metal pollution. The concentrations of these heavy metals were highest in summer. The concentration of Pb did not meet the first-class seawater standard, which was 66.67% higher than the limit, however, all others complied with the first-class seawater standard. Concentrations of all heavy metals were below chronic safe concentration of organisms recommended by National Oceanic and Atmospheric Administration (NOAA) except for Cu. The Nemerow Pollution Index of the offshore surface seawater of the Liaodong Bay was in the range of 0.43-2.37, which was lower than 2.6, thus the pollution degree in 2013 was determined to be clean to slightly polluted. The Comprehensive Quality Index was between 0.39-0.97, which was lower than 1.0, therefore the water environment was acceptable and ranked as clean to slight clean. There were three areas that were relatively heavily polluted, including the Suizhong offshore area, north of the Liaodong Bay estuary area, and the Fuzhou Bay and Jinzhou Bay offshore areas.
