Effects of sediment compaction on macroinfauna in a protected coastal wetland in Taiwan

Abstract

We examined the effects of recreational trampling on wetland sediments, saltmarshes, and macroinfauna in November 2006 and April and July 2007. We used penetration resistance to measure sediment compaction at the Kaomei wetland, a protected intertidal coastal wetland harbor- ing the largest tuberous bulrush marsh grass bed in Taiwan. We also examined the relationship of sediment compaction to visitor intensity and distribution of macroinfauna. Four compaction levels (low, medium-low, medium-high, and high) were identified using hierarchical cluster analysis. The spatial contour of sediment compaction was consistent with the level of visitor intensity, suggesting that human trampling is the main cause of sediment compaction in this wetland. Macroinfaunal abundance in low and medium-low compacted sediments was 4968 and 3376 ind. m -2 , while no macroinfauna was recorded in highly consolidated sediments. Compared to those at medium-low compaction, taxon richness and community density at medium-high compaction were significantly reduced by 80.5 and 52.6%, respectively. Polychaetes were more sensitive to sediment compaction than amphipods and bivalves, and could thus serve as a bioindicator of human trampling impact. A decrease in polychaete abundance may be attributed to their life history, which is controlled by sub- stratum compaction. Our results showed that 25.7% of the study area was significantly compressed and that muddy vegetated areas were more vulnerable than sandy areas. We conclude that losses of macroinfauna and microhabitats are serious, and we propose management strategies to prevent further deterioration of this wetland.