Temporal Coherence of Chlorophyll a during a Spring Phytoplankton Bloom in Xiangxi Bay of Three-Gorges Reservoir, China

Algal bloom phenomenon was defined as "the rapid growth of one or more phytoplankton species which leads to a rapid increase in the biomass of phytoplankton", yet most estimates of temporal coherence are based on yearly or monthly sampling frequencies and little is known of how synchrony varies among phytoplankton or of the causes of temporal coherence during spring algal bloom. In this study, data of chlorophyll a and related environmental parameters were weekly gathered at 15 sampling sites in Xiangxi Bay of Three-Gorges Reservoir (TGR, China) to evaluate patterns of temporal coherence for phytoplankton during spring bloom and test if spatial heterogeneity of nutrient and inorganic suspended particles within a single ecosystem influences synchrony of spring phytoplankton dynamics. There is a clear spatial and temporal variation in chlorophyll a across Xiangxi Bay. The degree of temporal coherence for chlorophyll a between pairs of sites located in Xiangxi Bay ranged from -0.367 to 0.952 with mean and median values of 0.349 and 0.321, respectively. Low levels of temporal coherence were often detected among the three stretches of the bay (Down reach, middle reach and upper reach), while high levels of temporal coherence were often found within the same reach of the bay. The relative difference of DIN between pair sites was the strong predictor of temporal coherence for chlorophyll a in down and middle reach of the bay, while the relative difference in Anorganic Suspended Solids was the important factor regulating temporal coherence in middle and upper reach. Contrary to many studies, these results illustrate that, in a small geographic area (a single reservoir bay of approximately 25 km), spatial heterogeneity influence synchrony of phytoplankton dynamics during spring bloom and local processes may override the effects of regional processes or dispersal.

Forecasting Daily Chlorophyll a Concentration during the Spring Phytoplankton Bloom Period in Xiangxi Bay of the Three-Gorges Reservoir by Means of a Recurrent Artificial Neural Network

A recurrent artificial neural network was used for 0-and 7-days-ahead forecasting of daily spring phytoplankton bloom dynamics in Xiangxi Bay of Three-Gorges Reservoir with meteorological, hydrological, and limnological parameters as input variables. Daily data from the depth of 0.5 m was used to train the model, and data from the depth of 2.0 m was used to validate the calibrated model. The trained model achieved reasonable accuracy in predicting the daily dynamics of chlorophyll a both in 0-and 7-days-ahead forecasting. In 0-day-ahead forecasting, the R-2 values of observed and predicted data were 0.85 for training and 0.89 for validating. In 7-days-ahead forecasting, the R-2 values of training and validating were 0.68 and 0.66, respectively. Sensitivity analysis indicated that most ecological relationships between chlorophyll a and input environmental variables in 0-and 7-days-ahead models were reasonable. In the 0-day model, Secchi depth, water temperature, and dissolved silicate were the most important factors influencing the daily dynamics of chlorophyll a. And in 7-days-ahead predicting model, chlorophyll a was sensitive to most environmental variables except water level, DO, and NH3N.

ALGAL GROWTH POTENTIAL AND NUTRIENT LIMITATION IN SPRING IN THREE-GORGES RESERVOIR, CHINA

In China, especially in Three-Gorges Reservoir, our knowledge of the algal growth potential and nutrient limitation was still limited. In the spring of 2006, the water column ratios of total nitrogen/total phosphorus were investigated and algal bioassays performed to determine algal growth potential of waters and nutrient limitation of mainstream and Xiangxi Bay of Three-Gorges Reservoir. The results showed sampling sites in mainstream were co-limited by N and P or P-limited alone, and sites in Xiangxi Bay were N-limited alone. Fe likely played an important role in determining the appearance and disappearance of algal blooms of Three-Gorges Reservoir. Native algae, Pseudokirchneriella subcapitata and Cyclotella meneghiniana, had high growth potential in Three-Gorges Reservoir.

Spring Diatom Blooming Phases in a Representative Eutrophic Bay of the Three-Gorges Reservoir, China

We investigated dynamics of the phytoplankton community and abiotic factors in Xiangxi Bay of the Three-Gorge Reservoir, China, by daily sampling, a specific site during a spring algal bloom (February 23-April 28, 2005). Among the 76 taxa observed, Asterionella formosa and Cyclotella spp. were the dominants, accounting for 47.2% and 29.9% of the total abundance, respectively. We determined the five distinct developing phases of the bloom by analyzing the dissimilarity of physicochemical parameters. Simultaneously, six phytoplankton community groups were distinguished by TWINSPAN classifications. The pattern for algal community succession was similar to that for the bloom phase shift, and the structural complexity of communities significantly decreased over time. Water temperature and silicate were the main factors that related to the development of the bloom and the shifts of the phytoplankton community.

The accumulation of alkylphenols in submersed plants in spring in urban lake, China

The concentrations of alkylphenols (APs) were investigated in water, sediments and submersed macrophytes from the Moon Lake, Wuhan city, China. The water samples contained APs, ranging up to 26.4 mu g l(-1) for nonylphenol (NP) and 0.68 mu g l(-1) for octylphenol (OP). APs were found in the sediment samples with concentrations ranging from 4.08 to 14.8 for NP and from 0.22 to 1.25 mu g l(-1) dry weight for OP. The samples from the site near former sewage inlet showed the highest concentrations of APs in both water and sediments. The results of distribution pattern and dynamics of NP and OP in submersed macrophytes of the Moon Lake showed that the two pollutants were all found in Myriophyllum verticillatum, Elodea nuttallii, Ceratophyllum oryzetorum, and Potamageton crispus collected from the Moon Lake. For NP, M. verticillatum had the highest capacity of accumulation, followed by E. nuttallii, C. oryzetorum and P. crispus. However the distribution pattern of OP differed from that of NP, and the highest amount of accumulation was observed in E. nuttallii, followed by M. verticillatum, P. crispus, and C. oryzetorum. The temporal pattern of APs was also observed in submersed macrophytes from March to May, and the highest accumulation period was in May. (c) 2008 Elsevier Ltd. All rights reserved.

Development and characterization of monoclonal antibodies to spring viraemia of carp virus

Five monoclonal antibodies (mAbs) against spring viraemia of carp (SVCV0504, isolated from common carp in China) were produced from mice immunized with purified virus preparations. The virion of SVCV contains five structural proteins, representing the nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and RNA-dependent RNA polymerase (Q. Western blotting analysis revealed that three mAbs (1145, IE10, and 11-17) recognized specifically to a single protein of 47 kDa (N), the mAb 3G4 reacted with, two SVCV0504 proteins of 69 kDa (G) and 47 kDa (N), while the mAb 1A9 reacted with three SVCV0504 proteins of 69 kDa (G), 50 kDa (P), and 47 kDa (N). By indirect ELISA, two mAbs (1H5 and 11-17) showed cross-reactivity with pike fry rhabdovirus (PFRV), but no cross-reactions with the Siniperca chuatsi rhabdovirus (SCRV), Scophthalmus maximus rhabdovirus (SMRV), Paralichthys olivaceus rhabdovirus (PoRV) were demonstrated with the five mAbs. Indirect immunofluorescence showed intense fluorescence in the cytoplasm of the SVCV0504-infected epithelioma papulosum cyprini (EPC) cells in areas corresponding to the location of granular structures. The sucrose gradient-purified SVCV0504 particles could be detected successfully by these mAbs using immunodot blotting. mAb 1A9 could completely neutralize 100 TCID50 (50% tissue culture infective dose) of SVCV0504 at a dilution of 1:8. This is the first report of development of the neutralizing mAbs against SVCV. The mAb 1A9 was analyzed further and could be used to successfully detect viral antigens in the infected-EPC cell cultures or in cryosections from experimentally infected crucian carp (Carassius auratus) by immunohistochemistry assay. Furthermore, a flow cytometry procedure for the detection and quantification of cytoplasmic SVCV0504 in cell cultures was developed with mAb 1A9. At 28 h after inoculation with the virus (0.01 PFU/cell), 10.12% of infected cells could be distinguished from the uninfected cells. These mAbs will be useful in diagnostic test development and pathogenesis studies for fish rhabdovirus. (c) 2008 Elsevier B.V. All rights reserved.

Macrozoobenthic community of Fuxian Lake, the deepest lake of southwest China

Located in the Yunnan-Guizhou Plateau in southwest China, Fuxian Lake covers an area of 211 km(2), with maximum depth of 155 m. It is known to have a unique fauna, including 14 described endemic species. In order to describe the zoobenthic community of the lake more completely, the present study was conducted from August 2002 to August 2003. Altogether 62 benthic taxa, including 22 oligochaetes, 21 molluscs and 18 insects were identified, of which the dominant taxa belonged to Potamothrix, Procladius and Paraprososthenia. The standing stocks of benthos were much higher in the littoral (824 ind/m(2) in density, 3.72 g/m(2) in biomass) than in the profundal region (23 ind/m(2) in density, 0.10 g/m(2) in biomass). Species richness was greatest in summer and standing stocks were larger in spring and summer than in other seasons. Analyses of functional feeding groups indicated that collector-gatherers and scrapers were predominant in entire lake. Stepwise multiple regression analysis demonstrated that the water depth is the most important factor affecting the distribution of macrozoobenthos. (C) 2008 Elsevier GmbH. All rights reserved.

Controlling factors of spring-summer phytoplankton succession in Lake Taihu (Meiliang Bay, China)

The spring-summer successions of phytoplankton and crustacean zooplankton were examined weekly in Meiliang Bay of the subtropical Lake Taihu in 2004 and 2005. During the study period, the ecosystem of Meiliang Bay was characterized by (i) clearly declined nitrogen compounds (nitrate, TN, and ammonium) and slowly increased phosphorus compounds (TP and SRP), (ii) increased total phytoplankton density and rapid replacement of chlorophyta (mainly Ulothrix) by cyanobacteria (mainly Microcystis), and (iii) rapid replacement of large-sized crustaceans (Daphnia and Moina) by small-sized ones (Bosmina, Limnoithona, and Ceriodaphnia). Results from the CCA and correlation analysis indicate that the spring-summer phytoplankton succession was primarily controlled by abiotic factors. Cyanobacteria were mainly promoted by increased temperature and decreased concentrations of nitrogen compounds. The pure contribution of crustacean was low for the variation of phytoplankton suggesting a weak top-down control by crustacean zooplankton in the subtropical Lake Taihu.

Field and experimental studies on the combined impacts of cyanobacterial blooms and small algae on crustacean zooplankton in a large, eutrophic, subtropical, Chinese lake

Field and experimental studies were conducted to evaluate the combined impacts of cyanobacterial blooms and small algae on seasonal and long-term changes in the abundance and community structure of crustacean zooplankton in a large, eutrophic, Chinese lake, Lake Chaohu. Seasonal changes of the crustacean zooplankton from 22 sampling stations were investigated during September 2002 and August 2003, and 23 species belonging to 20 genera were recorded. Daphnia spp. dominated in spring but disappeared in mid-summer, while Bosmina coregoni and Ceriodaphnia cornuta dominated in summer and autumn. Both maximum cladoceran density (310 ind. l(-1)) and biomass (5.2 mg l(-1)) appeared in autumn. Limnoithona sinensis, Sinocalanus dorrii and Schmackeria inopinus were the main species of copepods. Microcystis spp. were the dominant phytoplankton species and formed dense blooms in the warm seasons. In the laboratory, inhibitory effects of small colonial Microcystis on growth and reproduction of Daphnia carinata were more remarkable than those of large ones, and population size of D. carinata was negatively correlated with density of fresh large colonial Microcystis within a density range of 0-100 mg l(-1) (r = -0.82, P < 0.05). Both field and experimental results suggested that seasonal and long-term changes in the community structure of crustacean zooplankton in the lake were shaped by cyanobacterial blooms and biomass of the small algae, respectively, i.e., colonial and filamentous cyanobacteria contributed to the summer replacement of dominant crustacean zooplankton from large Daphnia spp. to small B. coregoni and C. cornuta, while increased small algae might be responsible for the increased abundance of crustacean zooplankton during the past decades.

Phosphorus fractions and alkaline phosphatase activity in sediments of a large eutrophic Chinese lake (Lake Taihu)

Spatial, vertical, and seasonal variations in phosphorus fractions and in alkaline phosphatase activity (APA) were investigated in sediments in a large-shallow eutrophic Chinese lake (Lake Taihu) in 2003-2004. The phosphorus content was highest in the most seriously polluted lake area. Iron-bound phosphorus (Fe(OOH)-P) dominated (47% on average) among the phosphorus fractions determined according to Golterman (Hydrobiologia 335:87-95, 1996). Notably, organically-bound P comprised a further significant additional portion (acid-soluble + hot NaOH-extractable organic P = 25%), which was highest at the most polluted sites. The Fe(OOH)-P content was the lowest in spring (April, 2004), suggesting that degradation of organic matter led to the release of iron-bound phosphates. Sediment APA showed a significant positive relationship with both organically-bound P and Fe(OOH)-P. Consequently, organically-bound P is an important portion of the sediment phosphorus in Lake Taihu. It is mainly derived from freshly-settled autochthonous particles and from external discharges. Organically-bound P induces APA and may lead to the release of bioavailable phosphates from the organic sediments, thereby accelerating lake eutrophication.

Characterization of complete genome sequence of the spring viremia of carp virus isolated from common carp (Cyprinus carpio) in China

The complete genome of spring viraemia of carp virus (SVCV) strain A-1 isolated from cultured common carp (Cyprinus carpio) in China was sequenced and characterized. Reverse transcription-polymerase chain reaction (RT-PCR) derived clones were constructed and the DNA was sequenced. It showed that the entire genome of SVCV A-1 consists of 11,100 nucleotide base pairs, the predicted size of the viral RNA of rhabdoviruses. However, the additional insertions in bp 4633-4676 and bp 4684-4724 of SVCV A-1 were different from the other two published SVCV complete genomes. Five open reading frames (ORFs) of SVCV A-1 were identified and further confirmed by RT-PCR and DNA sequencing of their respective RT-PCR products. The 5 structural proteins encoded by the viral RNA were ordered 3'-N-P-M-G-L-5'. This is the first report of a complete genome sequence of SVCV isolated from cultured carp in China. Phylogenetic analysis indicates that SVCV A-1 is closely related to the members of the genus Vesiculovirus, family Rhabdoviridae.

Studies on temporal and spatial variations of phytoplankton in Lake Chaohu

Temporal and spatial variations of the phytoplankton assemblage in Lake Chaohu, a large shallow eutrophic lake in China, were studied from September 2002 to August 2003. A total of 191 phytoplankton species was identified, among which Chlorophytes (101) ranked the first, followed by Cyanophytes (46) and Bacillariophytes (28). On average over the entire lake, the maximum total algal biomass appeared in June (19.70 mg/L) with a minimum (5.05 mg/ L) in November. In terms of annual mean biomass, cyanobacteria contributed 45.43% to total algal biomass, followed by Chlorophytes (27.14%), and Bacillariophytes (20.6%). When nitrate (NO3-N) and ammonium (NH4-N) concentrations dropped in spring, fixing-nitrogen cyanobacterium (Anabaena) developed quickly and ranked the first in terms of biomass in summer. It is likely that dominance of zooplanktivorous fish and small crustacean zooplankton favored the development of the inedible filamentous or colony forming cyanobacteria. The persistent dominance of cyanobacteria throughout all seasons may indicate a new tendency of the response of phytoplankton to eutrophication in Lake Chaohu.

Spatial analysis for spring bloom and nutrient limitation in Xiangxi bay of three Gorges Reservoir

The spatial and temporal dynamics of physical variables, inorganic nutrients and phytoplankton chlorophyll a were investigated in Xiangxi Bay from 23 Feb. to 28 Apr. every six days, including one daily sampling site and one bidaily sampling site. The concentrations of nutrient variables showed ranges of 0.02-3.20 mg/L for dissolved silicate (Si); 0.06-2.40 mg/L for DIN (NH4N + NO2N + NO3N); 0.03-0.56 mg/L for PO4P and 0.22-193.37 mu g/L for chlorophyll a, respectively. The concentration of chlorophyll a and inorganic nutrients were interpolated using GIS techniques. The results indicated that the spring bloom was occurred twice in space during the whole monitoring period (The first one: 26 Feb.-23 Mar.; the second one: 23 Mar.-28 Apr.). The concentration of DIN was always high in the mouth of Xiangxi Bay, and PO4P was high in the upstream of Xiangxi Bay during the whole bloom period. Si seems no obvious difference in space in the beginning of the spring bloom, but showed high heterogeneity in space and time with the development of spring bloom. By comparing the interpolated maps of chlorophyll a and inorganic variables, obvious consumptions of Si and DIN were found when the bloom status was serious. However, no obvious depletion of PO4P was found. Spatial regression analysis could explained most variation of Chl-a except at the begin of the first and second bloom. The result indicated that Si was the factor limiting Chl-a in space before achieved the max area of hypertrophic in the first and second bloom period. When Si was obviously exhausted, DIN became the factor limiting the Chl-a in space. Daily and bidaily monitoring of Site A and B, representing for high DIN: PO4P ratio and low DIN:PO4P ratio, indicated that the concentration of Si was decreased with times at both site A and B, and the dramatically drop of DIN was found in the end monitoring at site B. Multiple stepwise regression analysis indicated that Si was the most important factor affect the development of spring bloom both at site A and B in time series.

Community structure of small fishes in a shallow macrophytic lake (Niushan Lake) along the middle reach of the Yangtze River, China

This study describes the current status of the small fish community in Niushan Lake in China, and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on macrophyte cover conditions, the lake was divided into three major habitat types: (1) Potamogeton maackianus habitat, (2) Potamogeton maackianus and Myriophyllum spicatum habitat, and (3) uncovered or less-covered habitat. Fish were sampled quantitatively in the three habitat types by block nets seasonally from September 2002 to August 2003. A total of 10 469 individuals from 27 fish species were caught, among which 20 species were considered as small fishes. Rhodeus ocellatus, Paracheilognathus imberbis, Pseudorasbora parva, Micropercops swinhonis and Cultrichthys erythropterus were recognized as dominant small fishes according to their abundance and occurrence. It was noted that (1) small fishes predominated the total number of fish species in the lake, which reflected to some degree the size diminution phenomenon of fish resources; (2) many small fishes had plant detritus as their food item, which was consistent with the abundance of macrophyte detritus in the lake and implied the importance of detritus in supporting small fish secondary production. Canonical correspondence analysis suggested that the spatial distributions of most small fishes were associated with complex macrophyte cover conditions. Macrophyte biomass was positively correlated with species richness, diversity index and the catch per unit of effort (CPUE) of the fish community. Water depth had no significant effects on species diversity and distribution of the small fishes. Correspondence analysis revealed a higher occurrence of the small fishes and higher abundance of individuals in summer and autumn. Seasonal length-frequency distributions of several species indicated that more larval and juvenile individuals appeared in spring and summer. This study provides some baseline information which will be essential to long-term monitoring of small fish communities in the Yangtze lakes.

Daily dynamics of nutrients and chlorophyll a during a spring phytoplankton bloom in Xiangxi Bay of the Three Gorges Reservoir

We studied the daily dynamics of nutrients (total phosphorus [TP], total nitrogen [TN], and dissolved silicate [SiO2]) and chlorophyll a (chl a) during a spring bloom in Xiangxi Bay of the Three Gorges Reservoir in year 2005. According to the daily dynamics of chl a, the bloom occurred in two stages (23 February-25 March and 26 March-28 April). The concentration of SiO2 decreased at different layers of the water column with the development of the bloom. However, the decrease of SiO2 in the layers with high concentration of chl a was more dramatic than in the layers with low concentration of chl a. The concentration of TP was lowest value a few days after the peak of chl a during the first bloom period, and the lowest value of TN was found a few days after the peak of chl a during the second bloom period. Correlative analyses indicated that SiO2 and TP were limiting factors in the first bloom period, and SiO2 and TN were limiting factors in the second bloom period.