The Effect Of Sewage Effluents To The Seaweed Community In The Intertidal Zone

Most of the World’s coastal zone were eutrophicated by increased nutrient loads from surface runoff and city sewage with the development of costal city. Many studies were reported on the effect of eutrophication on the phytoplankton and red tides, while the report of the effect of eutrophication on the community of seaweed was still rare.The field survey was conducted in the outfall of the Lingshui River in Dalian and Huangjinshan area in Lvshun. The spatial variation of structure and concentration of nutrients from sewage, and the community of seaweed in different nutrient zone were studied. In addition, the comparative studies between Enteromorpha linza and Ceramium tenerrimum by the N and P nutrition physiology, and life history strategy. The results were as follows:1.The concentration of nutrients from sewage were reducted rapidly, followed by the variation of high NH4+and low NO3-to high NO3-and low NH4+. The structure of seaweed community was changed due to the increased nutrients load, which result in the desending of the species richness and the asending of degree of dominance of main species.2. NO3-and PO43-were taken up in the form of active uptake by E. linza and C tenerrimum. NH4+was taken up in the form of passive diffusion by E. linza, while in the form of active uptake by C. tenerrimum. E. linza could be more favor to high N than C. tenerrimum. E. linza exhibited higher growth rate than C. tenerrimum under same N condition, which suggested that the species has more demand to the resoures of nutrients.3. The r-strategy species usually has the capacity of higher population growth and fertility, which contribute to their domination in community. Due to the higher demand to the nutrients, the innate rate of increase and fertility of these species were inhibited in the state of low nutrient. Accordingly, spatial niche was saved, which provided the conditions to other species. While in the state of eutrophication, high nutrients would meet the demand of r-strategy species, so that the available substrata were mostly occupied, which result in the loss of biodiversity and the asending of degree of dominance of main species.