The effect of cylindrospermopsin on the bacterioplankton community:a microcosm experiment on water from Dishui Lake,Shanghai,China

Eutrophication and climate warming have intensified the global expansion of invasive cyanobacteria such as Cylindrospermopsis spp.and Chrysosporum spp.Cylindrospermopsin(CYN)produced by species of the latter two genera may harm phytoplankton,zooplankton,and fishes.However,effects of CYN on the bacterioplankton community have not been studied.Based on high-throughput sequencing,we explored the effect of CYN on the structure and function of the bacterioplankton community by adding pure CYN to in-situ water collected from a brackish coastal shallow lake:Dishui Lake,China.We found that most bacterioplankton taxa had a certain tolerance potential to CYN,but that high concentrations of CYN(40μg/L)caused a significant decrease in microbial abundance and functional groups.Of the dominant phyla,Actinobacteria had the strongest tolerance to CYN.Network analysis indicated that CYN caused shifts in the community structure of the bacterioplankton,reducing community stability and structural complexity.High CYN concentrations also reduced the correlation between the different bacterioplankton groups,and the abundances of some bacterial taxa associated with the denitrification function and the process of carbon transfer in the microbial food web were inhibited.Our study provide s new insight into the response of the bacterioplankton communities to harmful algal toxins produced by cyanobacteria.

Identification of a new Hazelnut disease in Liaoning Province:Hazelnut husk brown rot

Hazelnut husk brown rot has been identified as a new disease in Liaoning Province in recent years.The objective of this study as to identify the pathogen.[Method]In this study,a standard sample of hazelnut husk brown rot was collected from Songmudao Base in Dalian City,Liaoning Province.The pathogen was identified by the studies of the morphology,pathogenicity,and analyses of ITS and LSU sequences.The pathogen was isolated and purified,which was confirmed by Koch’s postulates.The symptoms after inoculation were the same as those collected directly from a diseased tree,which showed that it was the pathogenic fungus.The cultural characteristics and conidia and the morphology of the pathogenic fungi were similar to those of Botrytis cinerea’s.The ITS sequences and LSU sequences were compared to the associated strain sequences in GenBank,with 100%identity to Botrytis cinerea(GenBank accession number:MN589848.1)and Botrytis cinerea(GenBank accession number:KU140653.1),respectively.The infection status of the pathogen on the hazelnut husks was also observed.The studies suggested that the pathogen leading to the hazelnut husk brown rot as a new disease in Liaoning Province was Botrytis cinerea.

Spatial variations of macrozoobenthos and sediment nutrients in Lake Yangcheng: Emphasis on effect of pen culture of Chinese mitten crab

We determined the effect of Chinese mitten crab（CMC） pen culture on the quantified spatial distribution of the macrozoobenthic community and sediment nutrients in Lake Yangcheng.Redundancy analysis indicated that water temperature, macrophyte occurrence, sediment type, and crab culture were the main environmental factors that influence the spatiotemporal macrozoobenthic distribution. Macrozoobenthic assemblages in the lake were characterized by eutrophic indicator species. In the most polluted estuaries, the abundance and diversity indices of the whole community and abundance of chironomids and oligochaetes were significantly depressed, and sediment carbon（C） and phosphorus（P） were significantly enhanced compared with those in the western, middle（MB）, and eastern basin（EB）. Crab culture in this lake had significant effects on the species composition of the macrozoobenthic community in one of three CMC culture pens（CP）, and generally depressed the abundance of most chironomid and oligochaete species. Significantly increased diversity, evenness, sediment carbon and nitrogen content, and sediment C：P ratio in the CP were found compared with those in the three basins.However, no conspicuous difference in sediment P content between the CP and the two basins of MB and EB was detected. Our results showed that the enhanced diversity and evenness of macrozoobenthos might be associated with the joint effect of macrophyte planting and crab predation, and macrophyte planting may modify the effects of CMC culture by leading to disproportional accumulation of C and N in the sediment relative to P in the CP of the lake.

Rotifer community structure and its response to environmental factors in the Backshore Wetland of Expo Garden,Shanghai

We investigated rotifer community structure in the Backshore Wetland of the Expo Garden in Shanghai from September 2009 to August 2010.We identified 116 rotifer species,determined the dominant species and their relationships with environmental factors,and community diversity indices.Polyarthra trigla was the most common species over the four seasons and proportionally most dominant in spring and autumn,whereas Cephalodella exigua and Keratella cochlearis were the most dominant species in winter and summer,respectively.There was seasonal variability in species numbers,with the highest numbers in summer,followed by autumn and winter.The mean annual density was 815±1346 ind./L and the biomass was 0.3649±0.4940 mg/L.There were significant differences between months:the highest density(2723±2926 ind./L)and biomass(0.7938±0.8197 mg/L)occurred in June,while the lowest density(238±271 ind./L)and biomass(0.0476±0.0429 mg/L)occurred in May.Canonical correspondence analysis(CCA)indicated that temperature,pH,nitrite nitrogen(NO2-N),and total phosphorus(TP)were the most important abiotic factors affecting rotifer distribution.Our research showed that the adaptability of the rotifers to temperature was the important factor.

Changes in the phytoplankton community structure of the Backshore Wetland of Expo Garden, Shanghai from 2009 to 2010

Phytoplankton community structure,abundance,and species'spatial and temporal distributions were examined for the Backshore Wetland of Expo Garden in Shanghai from September 2009 to August 2010.A total of 371 phytoplankton species were identified from 109 genera 8 phyla.There were 18 dominant species in total,and Phormidium tenue was dominant during four seasons.The mean annual abundance and biomass were 711.11×10^(4) cells/L and 5.70 mg/L,respectively.The seasonal changing trend of existing stocks was bimodal,with main peaks of density and biomass occurring in the winter and a secondary peaks occurring in the summer.The Shannon–Wiener diversity index(H′),the Margalef species richness index(D),and Pielou's species evenness index(J)showed a clear seasonal trend.All of the indices showed a changing pattern,with the highest recorded values from the summer to autumn and the lowest recorded values from the winter to spring.The canonical correspondence analysis(CCA)showed that environmental factors,including water temperature,nitrate nitrogen,and pH were the main influencing factors to the change of phytoplankton community structure in the Backshore Wetland of Expo Garden in Shanghai.

Diel vertical migration of dominant planktonic crustaceans in the south branch of Yangtze Estuary,China

Zooplanktons are important food organisms of fishes,and their spatial and temporal distribution pattern has an important influence on the growth and reproduction of fishes in local habitats.The Yangtze River Estuary of China is rich in fishery resources,but the knowledge on the distribution pattern of zooplankton in this area is still very limited.The diel vertical migration(DVM)patterns and seasonal variations of the crustacean community,and their relationship with environmental factors were investigated in the south branch of the Yangtze Estuary,from June 2017 to May 2018.The results showed that the dispersion patterns of dominant crustacean taxa in the Yangtze Estuary were mostly aggregated.Migration amplitudes of crustacean were greater in spring and summer than in autumn and winter,and different migratory patterns occurred in different seasons.Sinocalanus dorrii,Schmackeria inopinus,Mesmackeria leuckarti,Bosmina longirostris,and B.fatalis,unlike S.forbesi,showed a significant DVM.The DVM patterns of crustaceans was possibly influenced by light dentisy,temperature,and total dissolved solids in the water column,and the fish predation effect;whereas,the nutrient concentration and pH were not supposed to be key factors.