The impact of sewage discharge on the macroalgae community in the Yellow Sea coastal area around Qingdao, China

The dynamics of macroalgal communities and the impact of sewage on their growth were studied in the tidal zone around Zhanqiao Pier of the Qingdao coastal area, in the northwest of the Yellow Sea, China, from September 2001 to September 2003. The tidal zone of the study area is divided into western and eastern sections by the Zhanqiao Pier. Inorganic nitrogen and phosphorus in seawater showed higher concentrations on the eastern side of Zhanqiao Pier than on the western side, because a sewer drains into the eastern side. The macroalgal communities on each side of the Pier showed an obvious difference due to the effect of this sewage discharge. A total of 47 macroalgal species including 10 greens, 11 browns and 26 reds was identified in this study. The species composition and biomass indicated higher values in the nutrient-rich area on the eastern side of Zhanqiao Pier compared with the nutrient-poor area on the western side of Zhanqiao Pier. Some ephemeral and filamentous species dominated seasonally on the eastern side of Zhanqiao Pier, in contrast to the western side where slow-growing species dominated throughout the year. Nutrient gradients and temperature were considered the main factors affecting the distribution of macroalgae communities in time and space. The results are consistent with the common observation that nutrient-poor areas are dominated by slow-growing rather than ephemeral algal species. Moreover, the species diversity in the whole study area had declined when compared to previous records.