Phytoplankton Assemblage And Its Dynamics In The Huiquan Bay, A Coastal Recreational Area Of Qingdao

For a better understanding of the phytoplankton structure and its relationshipwith environmental parameters in the No.1bathing beach of Qingdao in Huiquan Bay,monitoring works were carried out weekly to observe the phytoplankton communityand in situ environmental factors in a survey from September2010to January2012,totally134phytoplankton samples were collected from two stations. A total of94species in53genera of3classes were identified. Diatoms were preponderant in allseasons, and the average value of their contributions to the total phytoplanktonabundance was70.34%, with a peak reaching to98.60%.The annual mean chlorophylla concentration and phytoplankton abundance were3.18mg/m3and46.74cells/mlrespectively. The abundance of phytoplankton ranged from3.28cells/ml to483.92cells/ml, with2periods of high abundance appeared during the year-roundinvestigation, the higher one is from Jannuary to April, and the other is from August toSeptember.During this survey, Skeletonema costatum, Chaetoceros spp., Nitzschia spp.,Cylindrotheca closterium, and Navicula spp. were appeared as dominant species, andthree algal blooms of Skeletonema costatum were observed. The average of H’(Shannon-Weiner index) is2.59, which is higher than the observation in the JiaozhouBay (about0.70), a typical eutrophic location, but lower than the monitoring result ina clear coastal waters of Qingdao (about3.23). The annual average of DIN, DIP andDSi were15.88±9.63μmol/l、0.41±0.23μmol/l and6.24±3.93μmol/l, respectively, andno nutrient limitation was observed. In addition, statistical analysis displayed nosignificant correlation between phytoplankton abundances and nutrients (P>0.05),which was also frequently happened in eutrophic waters, such as Jiaozhou Bay.The scenario of correlation betwenen phytoplankton and nutrients varieddepending on different seasons. In autumns of2010and2011, the cell abundance ofdiatoms was significant correlation with DIN:DIP (P<0.05), suggested the DIN supplied a strong support on diatom growth. In winter of2010, DSi was significantnegative correlation with the phytoplankton abundance (P<0.05), but in winter of2011, no such significant correlations were observed, suggesting DSi was adequate in2011. In spring of2011, only Chaetoceros spp. was significant negative correlationwith DSi in phytoplankton assemblage (P<0.05), which suggested Chaetoceros spp.assimilated DSi strongly for their growths. In summer of2011, there was nosignificant correlation between phytoplankton abundances and nutrients (P>0.05),suggesting a strong exgenous nutrient from land rivers.During the opening season of No.1bathing beach, the average concentration ofchlorophyll a reached to7.26mg/m3, obviously higher than other periods, andpennate diatoms became the first dominant group among the phytoplanktoncommunity, meantime, a significant liner correlation between chlorophyll a andpennate diatoms was observed (P<0.01). Because of their raphes, pennate diatoms hadstronger ability to excrete mucilage than centric diatoms, which could damage theenvironmental amenity in the bathing beach area, and swimmers’ complaints on thelow amenity of this bathing beach suggested the above hypothesis maybe meet thefact. Also we leaned to consider that too much pennate diatoms could reduce theenvironmental amenity in such areas, and suggested pennate diatoms as a potentialbiological factor for environmental health assessment in such coastal recreationalwaters.