Development of an ecological quality evaluation system of Korean tidal flats

초록

A well-devised ecological evaluation system needs that the indicators that structure the system should be independent with natural controlling factors (e.g., salinity, mean grain size of surface sediment, etc.) or the effects of the factors should be accounted. There is a host of the systems available to assess tidal flat ecosystem. Nevertheless, we recognized the need to develop a better one with improved reliability and accuracy. In this study, two kinds of approach were done for the improvement: 1) we established different evaluation criteria for the different habitat types (i.e., criteria adapted to habitat types) to calibrate the effects of main controlling factors, tidal elevation and mean grain size, and 2) for the different sampling gears (grab vs. core sampler) to calibrate the gear effect on the variation of biological indicators. A number of environmental and biological indicators of a seven-grade system (I-III, good; IV-V, moderate; VI-VII, poor status) were suggested as follows: sediment AVS (acid-volatile sulfides) and heavy metal concentration; macrobenthos EIS (ecologically important species), productivity (wet weight biomass), biodiversity (alpha, beta and gamma diversity), and ecosystem health indices (ISEP, inverse function of Shannon-Wiener evenness proportion; KBQI, Korean benthic quality index); and presence of halophytes and water bird feeding grounds. Then, the general grades were calculated by weighted average of indicator grades estimated for each sample obtained in Korean tidal flats from 2008 to 2013. The frequencies of grade I and VII were less than 1%, respectively. The grades IV-V covered 68% of the tidal flats. The frequencies of grades I-III and IV-V varied across provinces between 12 and 25% and between 54 and 81%, respectively. Korean tidal flats better than moderate status (grades I-V) came up to 90%. The remaining 10% were found under poor status as requiring management action for the reinstatement.