Changes In Community Structure Of Meiofauna In The Thermal Discharge Area From Power Plant

The studies of meiofauna from power plant in Ninghai in Xiangshan Bay were carried out inJune(summer),September(autumn),December(winter),2008and March(spring),2009. In this paper, wediscussed abundance, biomass, and community structure of meiofauna and tropes types of free-livingmarine nematodes. The main results were as follows:A total of10groups of meiofauna were identified including Nemateda, Copepoda, Ostracoda,Polychaeta, Oligochaeta, Tubellaria, Bivalvia, Gastrotricha, Crustacean larvae and Aquatic insect larvae.Nemateda, Copepoda, Ostracoda, Gastrotricha, Polychaeta and Tubellaria were dominant groups. Marinenematodes were the most dominant groups, accounting for67.07%. Others were ostracods (18.97%),copepods(6.13%), gastropods (4.74%), tubellaria (1.85%), polychaetes (0.68%) and crustacean larvae(0.19%) respectively.Siginificant seasonal variation of abundance was revealed. The average abundance of meiofauna infour seasons were21128.93±3987.44inds/10cm~2, the abundance in spring was the highest which was7947.01±1211.98inds/10cm~2, followed by summer, autumn and winter. The average biomass ofmeiofauna in four seasons were120430.73±8097.97μg(dwt)/10cm~2，seasonal trends in biomassconsistent with the abundance. In spatial distribution, the abundance of meiofauna in section A near theoutlet was lowest, which was3138.51±1011.21inds/10cm~2, and the section B which was500m faraway from the outlet was the highest10501.60±2257.84inds/10cm~2. In the depth distribution,stratification of meiofauna was significant,80%of total number lived in the surface layer (0~5)cm ofsediments except the section A in spring and summer which was accounted for45%in the layer (5~10)cm.The average abundance and biomass of marine nematodes in four seasons were14171.79±4621.43inds/10cm~2and5668.71±1848.57μg(dwt)/10cm~2respectively. The abundance wre spring:5307.60±1557.14inds/10cm~2, summer:4435.88±1777.53inds/10cm~2, autumn:2899.19±870.97inds/10cm~2,winter:1529.12±415.79inds/10cm~2. Seasonal trends in biomass consistent with the abundance. Theabundance of nematodes in section A was lowest,1207.21±113.60inds/10cm~2, the section distributionwas similarly in the distribution of meiofauna. There were85%of marine nematodes in the surface layer (0~5)cm of sediments.The trophic structure of marine nematodes was studies. The selective deposit feeders(1A) and theepigrowth feeders(2A) were the dominate group, which accounted for48.18%and37.57%respectively.There was also a significant seasonal variation in nematode trophic structure. In summer, depositfeeders(1A+1B) had a large number(54.51%), but there was a large number of the epigrowth feeders(2A) inautumn and winter(82.27%). In different sections, deposit feeders(1A+1B) were dominant groups in sectionA. And the percentage of trophic structure showed that the food source of nematodes was mainly detritusand there were abundant organic debris and benthic diatoms in the sampling areas.