The Saemangeum tidal flat: Long-term environmental and ecological changes in marine benthic flora and fauna in relation to the embankment

The present article presents a historical overview of the Saemangeum reclamation projects and key findings from the ecological studies of the Saemangeum tidal flat, highlighting the ecological impact against the grand reclamation project, as a model example, in Korea. First, the scientific efforts given to the area of interest, mainly the inner part of the dikes, during the construction periods of series of four dikes (1991–2006) were summarized in terms of the change of environmental condition followed by the ecological responses over the past 20 years. As part of review, we selected and reanalyzed our series of the Saemangeum data including the current works relating to the microphytobenthos and macrozoobenthos, where the spatio-temporal variations cross the benthos in association with dike effects were carefully discussed in detail. The species composition in the upper intertidal zone, situated relatively far from the dikes, have been lesser changed between the periods of before (1988) and during the dike construction (2003–05). However, the benthic assemblages appeared to be changed in the mid to the lower intertidal zones of several transects and such phenomenon strengthened for the locations near the completed dike, e.g., Sandong transect near the dike of sector IV. Meanwhile, changes of the representative zoning in benthic assemblages during the dike construction were much clearly observed for the faunal species rather than flora. Such long-term ecological impacts including the timely increase of the opportunistic species during the dike construction were further evidenced the compositional change of the dominant benthos spanning two decades or so. In general, a long-term change in benthic community structure clearly reflected the community level impact apparently due to the attenuation of tidal energy by the embankment, varying the degree of impacts depending on the geographical location. Interdisciplinary monitoring and modeling studies are highly recommended to track natural variations in water quality and ecosystem health. Overall a long-term ecological monitoring should be applied to direct sound policy toward conservation of tidal wetlands, by emphasizing the significant biodiversity decline and coastal landscape depreciation.