Winter Phytoplankton Assemblages of Coastal Yellow Sea Connected to Jiaozhou Bay,China

The daily species variation of phytoplankton assemblage of coastal Yellow Sea connected to Jiaozhou Bay in the sea-water around the Xiaoqingdao Island was studied for the three months of winter, 2003. A total of 79 taxa from four phyla, Bacil-lariophyta (52 species), Pyrrophyta (25 species), Chrysophyta (1 species), and Cyanophyta (1species) were determined. In general, the most important groups were Bacillariophyta and Pyrrophyta on cell abundance and species richness. In January, the dominant species was mainly composed of cosmopolitan species such as Skeletonema costatum, then it changed to cosmopolitan species Tha-lassiosira nordenskiodii in February, and finally, it recovered to Skeletonema costatum again in March. Cell abundance ranged from 1.02 to 130.71×103 cells L-1with a single peak on 6th Feb., and the average abundance was 28.11 ± 26.01×103 cells L-1 (n = 90) during the winter time. The trends of Shannon-Weiner diversity index and Pielou’s evenness index were contrary to cell abundance, whereas the species diversity and evenness were the lowest in February. Temperature and salinity were closely correlated to phytoplankton species composition and cell abundance. According to the variations of temperature and salinity, species sequence was obvious at the studied site. This implies that the phytoplankton community of inner Jiaozhou Bay would be influenced heavily by the coastal Yel-low Sea phytoplankton assemblages.

Solar light,seawater temperature,and nutrients,which one is more important in affecting phytoplankton growth?

Based on research results on the impacts of solar light,seawater temperature,and nutrient available to phytoplankton growth and changes in phytoplankton physiology and assemblage,we discussed the order of influence of these factors.By clarifying the mechanisms and processes of the impacts by these factors,we have determined the rising order of the importance as solar light,seawater temperature,and nutrient silicon (Si).Therefore,for human interests in sustaining economic development,the first thing to be considered is the input of nutrient Si into the ocean,followed by seawater temperature change.

Long-term phosphorus reduction and phytoplankton responses in an urban lake(USA)

Eutrophication is one of the primary factors causing harmful cyanobacteria blooms in freshwater lakes.This study investigated the long-term changes in water quality and summer phytoplankton assemblages in Oswego Lake,OR,USA,in relation to phosphorus reduction through hypolimnetic aeration and alum applications.Both water quality and phytoplankton assemblages were sampled biweekly during the summers from 2001 to 2013.The concentrations of total phosphorus,soluble reactive phosphorus,and total nitrogen decreased 66%,93%and 31%,respectively,in response to the hypolimnetic aeration and alum treatments since 2005.Summer phytoplankton assemblages showed a 62%reduction of cyanobacteria biovolume and a shift from cyanobacteria dominance(2001–2005)to diatom and chlorophyte dominance(2006–2013).Cluster analysis identified four statistically different groups of summer phytoplankton assemblages(denoted Groups 1–4).Nonmetric multidimensional scaling analysis indicated that the four groups were associated with different water quality conditions.Group 1 occurred prior to hypolimnetic aeration and was primarily comprised of cyanobacteria,associated with water conditions of high nutrients and high primary production.Group 2,dominated by cyanobacteria and chlorophytes,occurred between hypolimnetic aeration and alum surface application.Group 3 was dominated by diatoms and occurred after alum surface application.Group 4 included R-strategist phytoplankton that quickly respond to environmental changes and occurred in the years following alum injection,drawdown,and inflow alum treatment.Both Group 3 and 4 were associated with reduced nutrients in the lake.We conclude that these lake management practices had strong effects on both production and community compositions of phytoplankton,and advocate for future studies on large-scale climate impacts on lake ecosystems and to identify corresponding best management practices.