Spatial and Temporal Variations of Microphytobenthos on the Common Reed Phragmites australis bed in a Marine Protected Area of Yeoja Bay, Korea

To characterize seasonal variation of microphytobenthos (MPB) biomass and composition in a Phragmites australis bed, the algal pigments in the top 20 mm of the sediments in a macrophyte marsh in a marine protected area in Yeoja Bay (Korea) were investigated monthly using high-performance liquid chromatography from November 2009 to December 2010, and compared with the upper and middle parts of a bare intertidal flat. Chlorophyll a (chla) concentration showed similar seasonal trends at all the sites, with bimodal peaks in April and August. The seasonal chla peaks were more pronounced on the bare flat than on the P. australis bed. While high amounts of pheophorbides a suggest an increased grazing activity during April-September on the bare flat, high ratios of pheophytins a/pheophorbides a on the P. australis bed indicate high levels of microbial degradation. While the dominance of diatoms characterized by high fuco/chla ratios appeared at all sites, the peaks of some accessory pigments (chlb, lutein, and zeaxanthin) at the P. australis bed led to the compositional difference in algal pigments from the bare sites. Altogether, our results suggest that the MPB biomass and composition in the P. australis bed are mediated by the vascular plant canopy.