Environmental Quality Assessment Of Fish And Shellfish Farming Areas And Characteristics Of Plankton Community Structure In Liusha Bay

Liusha Bay (20°22’~20°31’N,109°55’~110°1’E) is located insouthwest of Leizhou Peninsula, Zhanjiang City, Guangdong Province,forits superior natural and geographical conditions, becoming one of the mainproducing areas of Chinese Dunker (" pearl "). In recent years, farmershave introduced the short and quick farming cycle of cage fish and Gulfscallop. Thus cage culture, scallop hanging culture and pearl oysterfarming coexist in Liusha Bay. Natural disasters caused pearl industry gointo the trough between2007and2008, the traditional pearl farmers havetransferred a lot of fish cage culture industry, expanding a large number ofcages near inner bay and intersection of outer bay and inner bay, whichresulting in reducing water exchange capacity, deterioration of waterquality prevails, breeding disease outbreaks has become the norm. In viewof this, for environmental monitoring of water quality in different areas inLiusha Bay, and propose appropriate mitigation measures monitoring results, to restore pearl breeding dominance. In May, August, November in2012and January in2013, Each of the regional water quality, planktonand surface sediment sampling and monitoring in Liusha Bay, and the useof related pollution index evaluation method for each factor evaluation andanalysis of the monitoring results, while the use of redundancy analysis(RAD) features plankton community structure analysis and the correlationbetween environmental factors, the main results are as follows:1The surface water quality influence of Liusha Bay existing farmingpattern in different zones.In order to research farming activities impact on the environmentalsurrounding water, During may2012and January2013, we have carriedout four water quality investigations around the breeding areas, and wehave obtained the data of DO,NH4-N,NO2-N,NO3-N,DIP and COD. Wehave analyzed their distribution and evaluated the Pollution-condition byusing water quality evaluation index method (P) and evaluation index oforganic pollution (A).the result showed that water quality evaluation indexchanged with season significantly：in spring P＞1,showed water qualitystatus was poor,in summer,autumn and winter0.7＜P＜1,showed waterquality status was better than spring. During spring, summer and winter A＞4，showed, in autumn3＜A＜4，showed water quality status was betterthan any other season.P was the main limiting factor. The spatialdistribution，the most polluted area was farming areas inside of the bay,farming areas outside of the bay was in middle polluted condition. Theresults may provide some reference of layout and scale of farming inLiusha Bay.2Analysis of fish and shellfish farming areas community structure characteristics of phytoplankton in Liusha BayFrom May2012to January2013, Annual survey conducted andanalysis on phytoplankton in different farming areas in Liusha Bay. Theresults show that4phylum32genera91species have been identified inLiusha Bay. Diatom was the dominant group of25genera and79speciesaccounted for86.8%of the total, Dinoflagellates contain4genera and9species.2genera and2species of cyanobacteria;1species of greenalgae.Phytoplankton abundance is between64.9×104and418.5×104ind/m3, Skeletonema costatum was the dominant specie throughout the year.Diversity index analysis showed that the stream has been in Sandy Baywaters slightly polluted state. While the use of redundancy analysis (RAD)method analyzes the relationship between phytoplankton communitystructure characteristics and environmental factors, the results showed thatTP, NO3-N, TN, PO4-P and TN seasonal changes affect the diversity ofphytoplankton community structure in the main factor. Concluded that thediversity of phytoplankton has significant seasonal variation, which is thechanging environmental factors have a good correlation.3Zooplankton species composition and community structurecharacteristics of the change of time and space in Liusha BayFrom May2012to January2013, Annual survey conducted andanalysis on zooplankton in different farming areas in Liusha Bay. The results showed that the four surveys were collected64kinds of zooplankton,Subeucalanus subcrassus and Macruran larva were dominant specieswhich were appeard in multiple seasons, and each season dominant speciesdifference is obvious. Zooplankton abundance in outer bay is more thanculture zones inner bay. Winter diversity index (H ’=2.61) and evenness (J=0.84) were higher than in other seasons. The results show thatzooplankton in Liusha Bay is affected by Water temperature and nitrogenenvironment factor, etc, community structure changes greatly.4Distribution characteristics of C, N and P in Liusha Bay surface sedimentand its pollution assessmentBetween May2012and January2013, The sediment and watersamples have been collected each quarter in Liusha Bay, Sediment organiccarbon (TOC), the mass fraction of total nitrogen (TN) and totalphosphorus (TP), as well as bottom water dissolved oxygen (DO) andtemperature (T) measure have been measured, combining with dynamicanalysis, We have researched the surface sediment rich nutrientsdistribution characteristics and the degree of pollution of carbon, nitrogenand phosphorus. The results show that the physical terrain of Liusha Baydetermines the slow flow water in inside the Bay and the slow waterexchange between inside the Bay and outside the Bay. DO of underlyingwater rose from spring to winter significantly. The annual average underlying water DO of inner bay was lower than that of the outer bay. Themass fraction of TOC and TP in surface sediment had no significantseasonal changes, but the mass fraction of TN in spring and summersignificantly was much higher than in autumn and winter. The massfraction of TOC and TN in farming area was significantly higher than thecontrol area, and both were highest in the inner bay. TP content did nothave apparent spatial difference. The annual average pollution index forTOC, TN and TP were1.29,2.98and0.92, which indicated the bay had amedium level organic carbon pollution and low level nitrogen pollution,And the existing pattern of farming to accelerate rich nutrients deposit ofthe culture zones.