THE DEVELOPMENT OF THE DECAPOD ASSEMBLAGE AT A STEEL-SLAG DISPOSAL SITE WITH DISTURBANCE FROM A TYPHOON IN TAIWAN

摘要

This study describes the development of a biological assemblage on the seafloor after a massive habitat transformation. During 1984-1989, two million t of steel slag were disposed at 40-60 m depth in the coastal waters of southern Taiwan. After deposition, change in the benthic decapod assemblage was monitored for 9 yrs (1990-1998). During the first 6 yrs (1990-1995), in contrast to predictions, the overall structure of the assemblage in the disposal site was not significantly different from that of the nearby control site. However, during the later years (1996-1998), the total number of individuals at the disposal site was significantly reduced relative to the control area, assemblage variation was greater, and assemblage structure differed significantly from both the control site. Further analysis showed that typhoon Gloria, which hit the study site in July 1996, was the major cause of this assemblage structure shifting. Multi-dimensional scaling plots revealed that the assemblage structure after the event deviated from those of the earlier years. Interaction of a natural disturbance with unstable manmade substratum had a much greater impact on the development of the benthic decapod assemblage than waste disposal alone.