A cruise was undertaken from 3rd to 8th November 2004 in Changjiang(Yangtze) River Estuary and its adjacent waters to investigate the spatial biomass distribution and size composition of phytoplankton.Chlorophyll-a(Ch...A cruise was undertaken from 3rd to 8th November 2004 in Changjiang(Yangtze) River Estuary and its adjacent waters to investigate the spatial biomass distribution and size composition of phytoplankton.Chlorophyll-a(Chl-a) concentration ranged 0.42-1.17 μg L-1 and 0.41-10.43 μg L-1 inside and outside the river mouth,with the mean value 0.73 μg L-1 and 1.86 μg L-1,respectively.Compared with the Chl-a concentration in summer of 2004,the mean value was much lower inside,and a little higher outside the river mouth.The maximal Chl-a was 10.43 μg L-1 at station 18(122.67°E,31.25°N),and the region of high Chl-a concentration was observed in the central survey area between 122.5°E and 123.0°E.In the stations located east of 122.5°E,Chl-a concentration was generally high in the upper layers above 5 m due to water stratification.In the survey area,the average Chl-a in sizes of >20 μm and <20 μm was 0.28 μg L-1 and 1.40 μg L-1,respectively.High Chl-a concentration of <20 μm size-fraction indicated that the nanophytoplankton and picophytoplankton contributed the most to the biomass of phytoplankton.Skeletonema costatum,Prorocentrum micans and Scrippsiella trochoidea were the dominant species in surface water.The spatial distribution of cell abundance of phytoplankton was patchy and did not agree well with that of Chl-a,as the cell abundance could not distinguish the differences in shape and size of phytoplankton cells.Nitrate and silicate behaved conservatively,but the former could probably be the limitation factor to algal biomass at offshore stations.The distribution of phosphate scattered considerably,and its relation to the phytoplankton biomass was complicated.展开更多
Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in t...Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in the Jiaozhou Bay, China. In spring, the phytoplankton community structure was similar among the three stations, and was mainly composed of nanophytoplankton, such as, Skeletonema costatum and Cylindrotheca closterium. The structure became significantly different for the three stations in summer, when the dominant species at Stas A, B and C were Chaetoceros curvisetus, Pseudo-nitzschia delicatissima, C. affinis, C. debilis, Coscinodiscus oculus-iridis and Paralia sulcata respectively. Tintinnopsis beroidea and T. tsingtaoensis were the dominant species in spring, whereas the microzooplankton was apparently dominated by Strombidium sp. in summer. Pico- and nanophytoplankton had a relatively greater growth rate than microzooplankton both in spring and summer. The growth rate and grazing mortality rate were 0.18~0.44 and 0.12~1.47 d-1 for the total phytoplankton and 0.20~0.55 and 0.21~0.37 d-1 for nanophytoplankton in spring respectively. In summer, the growth rate and grazing mortality rate were 0.38~0.71 and 0.27~0.60 d-1 for the total phytoplankton and 0.11~1.18 and 0.41~0.72 d-1 for nano- and microphytoplankton respectively. The carbon flux consumed by microzooplankton per day was 7.68~39.81 mg/m3 in spring and 12.03~138.22 mg/m3 in summer respectively. Microzooplankton ingested 17.56%~92.19% of the phytoplankton standing stocks and 31.77%~467.88% of the potential primary productivity in spring; in contrast, they ingested 34.60%~83.04% of the phytoplankton standing stocks and 71.28%~98.80% of the potential primary productivity in summer. Pico- and nanophytoplankton appeared to have relatively greater rates of growth and grazing mortality than microphytoplankton during the experimental period. The grazing rate of microzooplankton in summer was a little bit greater than that in spring because of the relatively higher incubation temperature and different dominant microzooplankton species. Microzooplankton preferred ingesting nanophytoplankton to microphytoplankton in spring, while they preferred ingesting picophytoplankton to nanophytoplankton and microphytoplankton in summer. Compared with the results of dilution experiments performed in various waters worldwide, the results are in the middle range.展开更多
Spatial distribution of phaeopigment and size-fractionated chlorophyll a(Chl a) concentrations were examined in relation to hydrographic conditions in the northern South China Sea(NSCS) during a survey from 20 August ...Spatial distribution of phaeopigment and size-fractionated chlorophyll a(Chl a) concentrations were examined in relation to hydrographic conditions in the northern South China Sea(NSCS) during a survey from 20 August to 12 September, 2014. The total Chl a concentration varied from 0.006 to 1.488 μg/L with a mean value of 0.259±0.247(mean±standard deviation) μg/L. Chl a concentration was generally higher in shallow water(<200 m) than in deep water(>200 m), with mean values of 0.364±0.311 μg/L and 0.206±0.192 μg/L respectively. Vertically, the maximum total Chl a concentration appeared at depths of 30–50 m and gradually decreased below 100 m. The size-fractionated Chl a concentrations of grid stations and time-series stations(SEATS and J4) were determined, with values of pico-(0.7–2 μm), nano-(2–20 μm) and micro- plankton(20–200 μm) ranging from 0.001–0.287(0.093±0.071 μg/L), 0.004–1.149(0.148±0.192 μg/L) and 0.001–0.208(0.023±0.036 μg/L), respectively. Phaeopigment concentrations were determined at specifi c depths at ten stations, except for at station A9, and varied from 0.007 to 0.572(0.127±0.164) μg/L. Nano-and pico-plankton were the major contributors to total phytoplankton biomass, accounting for 50.99%±15.01% and 39.30%±15.41%, respectively, whereas microplankton only accounted for 9.39%±8.66%. The results indicate that the contributions of microplankton to total Chl a biomass were less important than picoplankton or nanoplankton in the surveyed NSCS. Diff erent sized-Chl a had similar spatial patterns, with peak values all observed in subsurface waters(30–50 m). The summer monsoon, Kuroshio waters, Zhujiang(Pearl) River plume, and hydrological conditions are speculated to be the factors controlling the abundance and spatial heterogeneity of Chl a biomass in the NSCS.展开更多
The size-fractionated composition of phytoplankton greatly influences the transfer efficiency of biomass in pelagic food chains and the biological carbon flux from surface waters to the deep sea.To better understand p...The size-fractionated composition of phytoplankton greatly influences the transfer efficiency of biomass in pelagic food chains and the biological carbon flux from surface waters to the deep sea.To better understand phytoplankton abundance and composition in polynya,ice zone,and open ocean regions of the Amundsen Sea Sector of the Southern Ocean(110°W-150°W),its size-fractionated distribution and vertical structure are reported for January to February 2020.Vertical integrated(0-200 m)chlorophyll(Chl)a concentrations within Amundsen polynya regions are significantly higher than those within ice zone(t test,p<0.01)and open ocean(t test,p<0.01)regions,averaging 372.3±189.0,146.2±152.1,and 49.0±20.8 mg·m^(−2),respectively.High Chl is associated with shallow mixed-layer depths and near-shelf regions,especially at the southern ends of 112°W and 145°W.Netplankton(>20μm)contribute 60%of the total Chl in Amundsen polynya and sea ice areas,and form subsurface chlorophyll maxima(SCM)above the pycnocline in the upper water column,probably because of diatom blooms.Net-,nano-,and picoplankton comprise 39%,32%,and 29%of total Chl in open ocean stations,respectively.The open-ocean SCM migrates deeper and is below the pycnocline.The Amundsen Sea SCM is moderately,positively correlated with the euphotic zone depth and moderately,negatively correlated with column-integrated net-and nanoplankton Chl.展开更多
Investigations of chlorophyll a and primary productivity were carried out inthe Bering Sea along the BR line and the BS line during the Second Chinese National Arctic ResearchExpedition in the summer of 2003.The resul...Investigations of chlorophyll a and primary productivity were carried out inthe Bering Sea along the BR line and the BS line during the Second Chinese National Arctic ResearchExpedition in the summer of 2003.The results showed that the surface chlorophyll a concentrationswere 0.199~1.170μg/dm^(3),and the average value was 0.723μg/dm^(3) on the BR line.For the BSline,the surface chlorophyll a concentrations were 0.519~4.644μg/dm^(3)(average 1.605μg/dm^(3))and 0.568~14.968μg/dm^(3)(average 5.311μg/dm^(3))during the early and late summer,respectively.The average value in the late summer was much higher than that in the early summer.The high values(more than 4.0μg/dm^(3))occurred at stations of the BS line in the southern Bering Strait.Thechlorophyll a concentrations in the subsurface layer were higher than those in the surface layer.The results of the size-fractionated chlorophyll a showed that the contribution of the picoplanktonto total chlorophyll a was the predominance at the early summer and the contribution of thenetplankton was the predominance at the late summer.The carbon potential primary productivitiesvaried between 0.471 and 1.147 mg/(m^(3)·h)on the BR line,with average rates of 0.728 mg/(m^(3)·h).The primary productivities on the BS line were much higher than those of the BR line,ranging from1.227 mg/(m^(3)·h)at the early summer to 19.046 mg/(m^(3)·h)at the late summer.The results of thesize-fractionated primary productivity showed that the contribution of the nanoplankton to totalproductivity was the predominance at the early summer and the contribution of the netplankton waspredominance at the late summer.The assimilation number of photosynthesis was 0.45~2.80 mg/(mg·h)in the surveyed stations.展开更多
The distributions of chlorophyll a concentration, primary production and new productionwere observed in the Laizhou Bay of the Bohai Sea in both spring and neap tides during July 1997. The results showed that there we...The distributions of chlorophyll a concentration, primary production and new productionwere observed in the Laizhou Bay of the Bohai Sea in both spring and neap tides during July 1997. The results showed that there were marked features of spatial zonation in the surveyed area, due to the differences between the geographic environment and the hydrological conditions. Chlorophyll a, primary production and new production were all higher in spring tides than that in neap tides in the Laizhou Bay. The highest values of these parameters were encountered in the central regions of the bay. At most stations, chlorophyll a concentrations at the bottom were higher than that at the surface. The results of size-fractionated chlorophyll a and primary production showed that contributions of nanocombining pi-coplankton ( <20 μm) to total chlorophyll a and primary production were dominant in phytoplankton community biomass and production of the Laizhou Bay. The environmental factors, primary production and new production in the Laizhou Bay are compared with other sea areas.展开更多
During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-frac...During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chi a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be found. Chlorophyll a concentration vertically decreased from surface to bottom in the Liaodong Gulf and the Bohai Gulf, while it increased in the Laizhou Bay, the strait and the central region of the Bohai Sea, and the highest value was encountered at the bottom. Size-fractionation results showed that nano - combining pico -plankton ( < 20 μm) predominated in phytoplankton communities of the Bohai Sea during late spring. The average contribution to total Chl a in each station ranged 76% -95 % (mean is 87 %). The contribution of net (> 20 μm), nano - (2- 20 fan) and picoplankton (< 2 μm) was 13% , 63% and 24% to total production, and 9% , 53% and 38% to total Chl a, respectively. It proved the importance of nano - and pico -plankton in phytoplankton communities in the Bohai Sea e-cosystems. In this paper the factors, such as light intensity and zooplankton grazing pressure, governing standing stock and production of phytoplankton in the Bohai Sea were also discussed.展开更多
The size structure of phytoplankton has considerable effects on the energy flow and nutrient cycling in themarine ecosystem,and thus is important to marine food web and biological pump.However,its dynamics in the high...The size structure of phytoplankton has considerable effects on the energy flow and nutrient cycling in themarine ecosystem,and thus is important to marine food web and biological pump.However,its dynamics in the high-latitude Arctic Ocean,particularly ice-covered areas,remain poorly understood.We investigated size-fractionated chlorophyll a(Chl a)and related environmental parameters in the highly ice-covered Arctic Ocean during the summer of 2020,and analyzed the relationship between Chl adistribution and water mass through cluster analysis.Results showed that inorganic nutrients were typically depleted in the upper layer of the Canada Basin region,and that phytoplankton biomass was extremely low(mean=0.05±0.18 mg·m^(−3))in the near-surface layer(upper 25 m).More than 80%of Chl a values were<0.1 mg·m^(−3) in the water column(0-200 m),but high values appeared at the ice edge or in corresponding ice areas on the shelf.Additionally,the mean contribution of both nanoplankton(2-20μm)(41%)and picoplankton(<2μm)(40%)was significantly higher than that of microplankton(20-200μm)(19%).Notably,the typical subsurface chlorophyll maximum(0.1 mg·m^(−3))was found north of 80°N,where the concentration of sea ice reached approximately 100%.The Chl aprofile results showed that the deep chlorophyll maximum of total-,micro-,nano-,and picoplankton was located at depth of 40,39,41,and 38 m,respectively,indicating that nutrients are the primary factor limiting phytoplankton growth in the ice-covered Arctic Ocean during summer.These phenomena suggest that,despite the previous literatures pointing to significant light limitation under the Arctic ice,the primary limiting factor for phytoplankton in summer is still nutrient.展开更多
The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12'S, 70°30'E, 73°E and 75(30'E) at December 18-26,...The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12'S, 70°30'E, 73°E and 75(30'E) at December 18-26, 1998 and January 12-18, 1999 in Prydz Bay and its north sea area, Antarctica. The results showed that surface chlorophyll a concentration were 0. 16 -3. 99 μg dm-3. The high values of chlorophyll a concentration (more than 3.5 μg dm -3) were in Prydz Bay and in the west Ladies Bank. The average chlorophyll a concentration at sub-surface layer was higher than that at surface layer; its concentration at the deeper layers of 50 m decreased with increasing depth and that at 200 m depth was only 0. 01 -0. 95μg dm -3. The results of size-fractionated chlorophyll a showed that the contribution of the netplanktion to total chlorophyll a was 56% , those of the nanoplankton and the picoplankton were 24% and 20% respectively in the surveyed area. The potential primary productivity at the euphotic zone in the surveyed area was 0. 11 - 11. 67 mgC m-3h-1 and average value was 2.00 ±2.80 mgC m h . The in-situ productivity in the bay and the continental shelf was higher and that in the deep-sea area was lower. The assimilation number of photosynthesis was 1.53±1. 11 mgC/(mg Chi a · h). The results of size-fractionated primary productivity show that the contribution of the netplanktion to total productivity was 58% , those of the nanoplankton and the picoplankton were 26% and 16% respectively. The cell abundance of phytoplankton was 1. 6 × 103 - 164. 8 × 103 cell dm-3 in the surface water.展开更多
The chlorophyll-a concentration is generally overestimated for the southern China coastalwaters if the default algorithm of the SeaDAS is employed. An algorithm is developed for retrieval of chlorophyll-a concentratio...The chlorophyll-a concentration is generally overestimated for the southern China coastalwaters if the default algorithm of the SeaDAS is employed. An algorithm is developed for retrieval of chlorophyll-a concentration in the Zhujiang Estuary, Guangdong Province, China, by using simulated reflectance data. The simulated reflectance is calculated corresponding to the SeaWiFS wavelength bands, via a general model by inputting measured water components, i.e. , the suspended sediment, chlorophyll-a, and yellow substance (DOC) concentration data of 130 samples. Empirical relationships of the chlorophyll-a concentration to 240 different band combinations are investigated based on the simulated reflectance data, and the band combination, R_5R_5/R_3R_4, is found to be the optimum one for the development of an algorithm valid for the Zhujiang Estuary. This algorithm is then employed to determine the chlorophyll-a concentration from SeaWiFS data. The estimated concentrations have a better accuracy than those obtained from the SeaDAS default algorithm when compared with sea truth data. The new algorithm is demonstrated to work well and is used to derive a series of image maps of the chlorophyll-a concentration distribution for the Zhujiang Estuary and adjacent coastal areas.展开更多
The response of the upper-ocean temperatures and currents in the tropical Pacific to the spatial distribution of chlorophyll-a and its seasonal cycle is investigated using a coupled atmosphere-ocean model and a stand-...The response of the upper-ocean temperatures and currents in the tropical Pacific to the spatial distribution of chlorophyll-a and its seasonal cycle is investigated using a coupled atmosphere-ocean model and a stand-alone oceanic general circulation model.The spatial distribution of chlorophyll-a significantly influences the mean state of models in the tropical Pacific.The annual mean SST in the eastern equatorial Pacific decreases accompanied by a shallow thermocline and stronger currents because of shallow penetration depth of solar radiation.Equatorial upwelling dominates the heat budget in that region.Atmosphere-ocean interaction processes can further amplify such changes. The seasonal cycle of chlorophyll-a can dramatically change ENSO period in the coupled model.After introducing the seasonal cycle of chlorophyll-a concentration,the peak of the power spectrum becomes broad,and longer periods(3 years) are found.These changes led to ENSO irregularities in the model. The increasing period is mainly due to the slow speed of Rossby waves,which are caused by the shallow mean thermocline in the northeastern Pacific.展开更多
A previously developed model was modified to derive three phytoplankton size classes (micro-, nano-, and pico-phytoplankton) from the overall chlorophyll-a concentration, assuming that each class has a specific absorp...A previously developed model was modified to derive three phytoplankton size classes (micro-, nano-, and pico-phytoplankton) from the overall chlorophyll-a concentration, assuming that each class has a specific absorption coefficient. The modified model performed well using in-situ data from the northern South China Sea, and the results were reliable and accurate. The relative errors of the size-fractioned chlorophyll-a concentration for each size class were: micro-:21%, nano-:41%, pico-:26%, and nano+pico:23%. The model was then applied on ocean color remote sensing data to examine the distribution and variation of phytoplankton size classes in northern South China Sea on a large scale.展开更多
Bayesian regularized BP neural network(BRBPNN) technique was applied in the chlorophyll-α prediction of Nanzui water area in Dongting Lake. Through BP network interpolation method, the input and output samples of t...Bayesian regularized BP neural network(BRBPNN) technique was applied in the chlorophyll-α prediction of Nanzui water area in Dongting Lake. Through BP network interpolation method, the input and output samples of the network were obtained. After the selection of input variables using stepwise/multiple linear regression method in SPSS i1.0 software, the BRBPNN model was established between chlorophyll-α and environmental parameters, biological parameters. The achieved optimal network structure was 3-11-1 with the correlation coefficients and the mean square errors for the training set and the test set as 0.999 and 0.000?8426, 0.981 and 0.0216 respectively. The sum of square weights between each input neuron and the hidden layer of optimal BRBPNN models of different structures indicated that the effect of individual input parameter on chlorophyll- α declined in the order of alga amount 〉 secchi disc depth(SD) 〉 electrical conductivity (EC). Additionally, it also demonstrated that the contributions of these three factors were the maximal for the change of chlorophyll-α concentration, total phosphorus(TP) and total nitrogen(TN) were the minimal. All the results showed that BRBPNN model was capable of automated regularization parameter selection and thus it may ensure the excellent generation ability and robustness. Thus, this study laid the foundation for the application of BRBPNN model in the analysis of aquatic ecological data(chlorophyll-α prediction) and the explanation about the effective eutrophication treatment measures for Nanzui water area in Dongting Lake.展开更多
A one-year field study was conducted to determine the conversion ratio of phytoplankton biomass carbon (Phyto-C) to chlorophyll-a (Chl-a) in Jiaozhou Bay, China. We measured suspended particulate organic carbon (...A one-year field study was conducted to determine the conversion ratio of phytoplankton biomass carbon (Phyto-C) to chlorophyll-a (Chl-a) in Jiaozhou Bay, China. We measured suspended particulate organic carbon (POC) and phytoplankton Chl-a samples collected in surface water monthly from March 2005 to February 2006. The temporal and spatial variations of Chl-a and POC concentrations were observed in the bay. Based on the field measurements, a linear regression model Ⅱwas used to generate the conversion ratio of Phyto-C to Chl-a. In most cases, a good linear correlation was found between the observed POC and Chl-a concentrations, and the calculated conversion ratios ranged from 26 to 250 with a mean value of 56 μg ·μl^-1. The conversion ratio in the fall was higher than that in the winter and spring months, and had the lowest values in the summer. The ratios also exhibited spatial variations, generally with low values in the near shore regions and relatively high values in offshore waters. Our study suggests that temperature was likely to be the main factor influencing the observed seasonal variations of conversion ratios while nutrient supply and light penetration played important roles in controlling the spatial variations.展开更多
Nutrient and Chlorophyll-a (Chl-a) concentrations were investigated monthly along three transects extending from a mariculturc area to open waters around the Zhangzi Island area from July to December 2009. The objec...Nutrient and Chlorophyll-a (Chl-a) concentrations were investigated monthly along three transects extending from a mariculturc area to open waters around the Zhangzi Island area from July to December 2009. The objective of this study is to illus- trate food availability to the bottom-sowed scallop Patinopecten yessoensis under the influences of the Yellow Sea Cold Water Mass (YSCWM), freshwater input and feedbacks of cultivated scallops. Significant thermal stratification was present in open waters from July to October, and salinity decreased in July and August in surface layers in the mariculture area. Nutrient concentrations increased with depth in both areas in summer, but were similar through water column in November and December. On average, nutrient in- creased from summer to autumn in all components except ammonia. Nutrient concentrations lower than the minimum thresholds for phytoplankton growth were present only in upper layers in summer, but stoichiometric nitrogen limitation existed in the entire inves- tigation period. Column-averaged Chl-a concentration was lower in open waters than in mariculture area in all months. It increased significantly in mariculturc area in August and October, and was less variable in open waters. Our results show that nutrients limita- tion to phytoplankton growth is present mainly in upper layer in association with stratification caused by YSCWM in summer. Freshwater input and upwelling of nutrients accumulated in YSCWM can stimulate phytoplankton production in mariculture area. Farming activities may change stoichiometric nutrient ratios but have less influence on Chl-a concentration.展开更多
This study investigated the relationships among the parameters of dissolved oxygen, chlorophyll-a and phytoplankton composition in tilapia ponds. Each pond (a total of 18 ponds) was sampled once in the dry, winter sea...This study investigated the relationships among the parameters of dissolved oxygen, chlorophyll-a and phytoplankton composition in tilapia ponds. Each pond (a total of 18 ponds) was sampled once in the dry, winter season between January and March and again early in the rainy season between May and June. The data were analyzed by examining correlations among parameters as affected by season, altitude and culture system. Observations were made at sites located in 5 selected provinces of northern Thailand: Chiangrai, Chiangmai, Phayao, Lampang and Nakornsawan. Mean elevation of these areas range from 25 to 582 meters above sea level (masl) and were categorized into low (400 masl) elevation sites. Ponds were 0.8 - 2.0 m deep, 0.16 - 0.64 ha in area and could be further categorized into high and low input systems.Mean air temperature in winter ranged between 16.5°C - 35.8°C while mean water temperature ranged between 25.5°C - 27.1°C. In rainy season, air temperature ranged between 22.0°C - 37.3°C and water temperature ranged between 29.4°C - 31.8°C. The amount of chlorophyll-a in both seasons were comparable (p > 0.05), but chlorophyll-a in high input system was significantly higher (p 0.05) than in low input ponds. Only weak correlation was found between chlorophyll-a, DOmax and DOmin. Multifactor-ANOVA was used to analyze the difference of total bacteria and filamentous cyanobacteria in ponds based upon elevation, culture systems and season. Result shows that there is a significant interaction observed between elevation, culture system and season (p 0.05). Species diversity and composition of phytoplankton in fish ponds in 2 seasons revealed the presence of 90 genera of phytoplankton under all 7 divisions. Divisions Chlorophyta and Cyanophyta had the most number of genera identified in both seasons with Pediastrum spp., and Scendesmus spp., and Anabaena spp. as dominant genera/genus, respectively.展开更多
Climatological mean and annual variations of Chlorophyll-a (Chl-a) distribution, sea surface wind (SSW), and sea surface temperature (SST) from 1998 to 2008 were analyzed in the middle of the South China Sea (...Climatological mean and annual variations of Chlorophyll-a (Chl-a) distribution, sea surface wind (SSW), and sea surface temperature (SST) from 1998 to 2008 were analyzed in the middle of the South China Sea (SCS), focusing on the typical region off the east coast of Vietnam (8.5-14°N, 109.5-114°E). Based on remote sensing data and SCS summer monsoon index (SCSSMI) data, high Chl-a concentrations in the middle of the SCS in the southwest summer monsoon season (June-September) may be related to strong Ekman pumping and strong wind stress. The maximum of the monthly averaged cli- matological Chl-a in the summer appeared in August. According to the annual variation, there was a significant negative correlation (r = -0.42) between the SCSSMI and SST, a strongly positive correlation (r=0.61) between the SCSSMI and Chl-a, and a strongly negative correlation (r = -0.74) between the SST and Chl-a in the typical region off the east coast of Vietnam during 1998-2008. Due to the E1 Nifio event specifically, the phenomena of a low Chl-a concentration, high SST and weak SCSSMI were extremely predominant in the summer of 1998. These relationships imply that the SCSSMI associated with the SST could be used to predict the annual variability of summer Chl-a in the SCS.展开更多
Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general cir...Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general circulation model. This study indicates that enhanced meridional gradient of chlorophyll-a between the equator and off-equatorial regions can strengthen zonal circulation and lead to a decrease in equatorial sea surface temperature (SST). However, the circulation changes by themselves are not effective enough to affect SST in the equatorial cold tongue (CT) region. The comparison between the experiments indicates that the CT SST are more sensitive to chlorophyll-a distribution away from the equator. The off-equatorial chlorophyll-a traps more solar radiation in the mixed layer, therefore, the temperature in the thermoeline decreases. The cold water can then be transported to the equator by the meridional circulation within the mixed layer. Furthermore, the relation among CT SST, the surface heat flux, and the equatorial upwelling are discussed. The study implies the simulation biases of temperature on the equator are not only related to the local ocean dynamics but also related to some deficiency in simulating off-equatorial processes.展开更多
[Objective] The aim was to study the relationship between chlorophyll-a and environmental impact factors in deep reservoir in Karst Areas.[Method] Taking Aha Reservoir for example,the changes of chlorophyll-a content ...[Objective] The aim was to study the relationship between chlorophyll-a and environmental impact factors in deep reservoir in Karst Areas.[Method] Taking Aha Reservoir for example,the changes of chlorophyll-a content and its relationship with environmental impact factors were researched,and the water quality of Aha Reservoir was assessed by means of modified Carlson trophic state index.[Result] Chlorophyll-a content in Aha Reservoir was higher in March,April,May and September and lower from June to August,and there was obvious seasonal variation,namely its variation trend was spring>summer>autumn>winter.In addition,chlorophyll-a content showed extremely significant correlation with transparency and dissolved oxygen (P<0.01) and significant correlation with ammonia nitrogen (P<0.05).Meanwhile,trophic state index was higher in whole year in Aha Reservoir which was in moderate trophic state in August,October and November and eutrophic state in other months.[Conclusion] The study could provide scientific reference for discussing the mechanism of lake eutrophication.展开更多
基金Supported by the National Natural Sciences Foundation (No. 50339040)Knowledge Innovation Program of Chinese Academy of Sciences (KZCX2-YW-213 and KZCX3-SW-232)
文摘A cruise was undertaken from 3rd to 8th November 2004 in Changjiang(Yangtze) River Estuary and its adjacent waters to investigate the spatial biomass distribution and size composition of phytoplankton.Chlorophyll-a(Chl-a) concentration ranged 0.42-1.17 μg L-1 and 0.41-10.43 μg L-1 inside and outside the river mouth,with the mean value 0.73 μg L-1 and 1.86 μg L-1,respectively.Compared with the Chl-a concentration in summer of 2004,the mean value was much lower inside,and a little higher outside the river mouth.The maximal Chl-a was 10.43 μg L-1 at station 18(122.67°E,31.25°N),and the region of high Chl-a concentration was observed in the central survey area between 122.5°E and 123.0°E.In the stations located east of 122.5°E,Chl-a concentration was generally high in the upper layers above 5 m due to water stratification.In the survey area,the average Chl-a in sizes of >20 μm and <20 μm was 0.28 μg L-1 and 1.40 μg L-1,respectively.High Chl-a concentration of <20 μm size-fraction indicated that the nanophytoplankton and picophytoplankton contributed the most to the biomass of phytoplankton.Skeletonema costatum,Prorocentrum micans and Scrippsiella trochoidea were the dominant species in surface water.The spatial distribution of cell abundance of phytoplankton was patchy and did not agree well with that of Chl-a,as the cell abundance could not distinguish the differences in shape and size of phytoplankton cells.Nitrate and silicate behaved conservatively,but the former could probably be the limitation factor to algal biomass at offshore stations.The distribution of phosphate scattered considerably,and its relation to the phytoplankton biomass was complicated.
基金supported by the National Natural Science Foundation of China under contract Nos 40206020 and 40306025the National Fundamental Rescarch Program of China under contract No.2001CB409702.
文摘Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in the Jiaozhou Bay, China. In spring, the phytoplankton community structure was similar among the three stations, and was mainly composed of nanophytoplankton, such as, Skeletonema costatum and Cylindrotheca closterium. The structure became significantly different for the three stations in summer, when the dominant species at Stas A, B and C were Chaetoceros curvisetus, Pseudo-nitzschia delicatissima, C. affinis, C. debilis, Coscinodiscus oculus-iridis and Paralia sulcata respectively. Tintinnopsis beroidea and T. tsingtaoensis were the dominant species in spring, whereas the microzooplankton was apparently dominated by Strombidium sp. in summer. Pico- and nanophytoplankton had a relatively greater growth rate than microzooplankton both in spring and summer. The growth rate and grazing mortality rate were 0.18~0.44 and 0.12~1.47 d-1 for the total phytoplankton and 0.20~0.55 and 0.21~0.37 d-1 for nanophytoplankton in spring respectively. In summer, the growth rate and grazing mortality rate were 0.38~0.71 and 0.27~0.60 d-1 for the total phytoplankton and 0.11~1.18 and 0.41~0.72 d-1 for nano- and microphytoplankton respectively. The carbon flux consumed by microzooplankton per day was 7.68~39.81 mg/m3 in spring and 12.03~138.22 mg/m3 in summer respectively. Microzooplankton ingested 17.56%~92.19% of the phytoplankton standing stocks and 31.77%~467.88% of the potential primary productivity in spring; in contrast, they ingested 34.60%~83.04% of the phytoplankton standing stocks and 71.28%~98.80% of the potential primary productivity in summer. Pico- and nanophytoplankton appeared to have relatively greater rates of growth and grazing mortality than microphytoplankton during the experimental period. The grazing rate of microzooplankton in summer was a little bit greater than that in spring because of the relatively higher incubation temperature and different dominant microzooplankton species. Microzooplankton preferred ingesting nanophytoplankton to microphytoplankton in spring, while they preferred ingesting picophytoplankton to nanophytoplankton and microphytoplankton in summer. Compared with the results of dilution experiments performed in various waters worldwide, the results are in the middle range.
基金Supported by the Program for New Century Excellent Talents in University(No.NCET-12-1065)the Ocean Public Welfare Scientifi c Research Project(No.201105021-03)+3 种基金the National Natural Science Foundation of China(Nos.41276124,41176136)the Science Fund for University Creative Research Groups in Tianjin(No.TD12-5003)the Key Project of National Natural Science Foundation of Tianjin(No.12JCZDJC30100)to J Sunthe National Natural Science Foundation of China(No.41306118)to Y Feng
文摘Spatial distribution of phaeopigment and size-fractionated chlorophyll a(Chl a) concentrations were examined in relation to hydrographic conditions in the northern South China Sea(NSCS) during a survey from 20 August to 12 September, 2014. The total Chl a concentration varied from 0.006 to 1.488 μg/L with a mean value of 0.259±0.247(mean±standard deviation) μg/L. Chl a concentration was generally higher in shallow water(<200 m) than in deep water(>200 m), with mean values of 0.364±0.311 μg/L and 0.206±0.192 μg/L respectively. Vertically, the maximum total Chl a concentration appeared at depths of 30–50 m and gradually decreased below 100 m. The size-fractionated Chl a concentrations of grid stations and time-series stations(SEATS and J4) were determined, with values of pico-(0.7–2 μm), nano-(2–20 μm) and micro- plankton(20–200 μm) ranging from 0.001–0.287(0.093±0.071 μg/L), 0.004–1.149(0.148±0.192 μg/L) and 0.001–0.208(0.023±0.036 μg/L), respectively. Phaeopigment concentrations were determined at specifi c depths at ten stations, except for at station A9, and varied from 0.007 to 0.572(0.127±0.164) μg/L. Nano-and pico-plankton were the major contributors to total phytoplankton biomass, accounting for 50.99%±15.01% and 39.30%±15.41%, respectively, whereas microplankton only accounted for 9.39%±8.66%. The results indicate that the contributions of microplankton to total Chl a biomass were less important than picoplankton or nanoplankton in the surveyed NSCS. Diff erent sized-Chl a had similar spatial patterns, with peak values all observed in subsurface waters(30–50 m). The summer monsoon, Kuroshio waters, Zhujiang(Pearl) River plume, and hydrological conditions are speculated to be the factors controlling the abundance and spatial heterogeneity of Chl a biomass in the NSCS.
基金This research was financially supported by National Polar Special Program“Impact and Response of Antarctic Seas to Climate Change”(Grant no.IRASCC 01-02-01)
文摘The size-fractionated composition of phytoplankton greatly influences the transfer efficiency of biomass in pelagic food chains and the biological carbon flux from surface waters to the deep sea.To better understand phytoplankton abundance and composition in polynya,ice zone,and open ocean regions of the Amundsen Sea Sector of the Southern Ocean(110°W-150°W),its size-fractionated distribution and vertical structure are reported for January to February 2020.Vertical integrated(0-200 m)chlorophyll(Chl)a concentrations within Amundsen polynya regions are significantly higher than those within ice zone(t test,p<0.01)and open ocean(t test,p<0.01)regions,averaging 372.3±189.0,146.2±152.1,and 49.0±20.8 mg·m^(−2),respectively.High Chl is associated with shallow mixed-layer depths and near-shelf regions,especially at the southern ends of 112°W and 145°W.Netplankton(>20μm)contribute 60%of the total Chl in Amundsen polynya and sea ice areas,and form subsurface chlorophyll maxima(SCM)above the pycnocline in the upper water column,probably because of diatom blooms.Net-,nano-,and picoplankton comprise 39%,32%,and 29%of total Chl in open ocean stations,respectively.The open-ocean SCM migrates deeper and is below the pycnocline.The Amundsen Sea SCM is moderately,positively correlated with the euphotic zone depth and moderately,negatively correlated with column-integrated net-and nanoplankton Chl.
基金supported by the National Natural Science Foundation of China under contract Nos 40476004 and 40476003.
文摘Investigations of chlorophyll a and primary productivity were carried out inthe Bering Sea along the BR line and the BS line during the Second Chinese National Arctic ResearchExpedition in the summer of 2003.The results showed that the surface chlorophyll a concentrationswere 0.199~1.170μg/dm^(3),and the average value was 0.723μg/dm^(3) on the BR line.For the BSline,the surface chlorophyll a concentrations were 0.519~4.644μg/dm^(3)(average 1.605μg/dm^(3))and 0.568~14.968μg/dm^(3)(average 5.311μg/dm^(3))during the early and late summer,respectively.The average value in the late summer was much higher than that in the early summer.The high values(more than 4.0μg/dm^(3))occurred at stations of the BS line in the southern Bering Strait.Thechlorophyll a concentrations in the subsurface layer were higher than those in the surface layer.The results of the size-fractionated chlorophyll a showed that the contribution of the picoplanktonto total chlorophyll a was the predominance at the early summer and the contribution of thenetplankton was the predominance at the late summer.The carbon potential primary productivitiesvaried between 0.471 and 1.147 mg/(m^(3)·h)on the BR line,with average rates of 0.728 mg/(m^(3)·h).The primary productivities on the BS line were much higher than those of the BR line,ranging from1.227 mg/(m^(3)·h)at the early summer to 19.046 mg/(m^(3)·h)at the late summer.The results of thesize-fractionated primary productivity showed that the contribution of the nanoplankton to totalproductivity was the predominance at the early summer and the contribution of the netplankton waspredominance at the late summer.The assimilation number of photosynthesis was 0.45~2.80 mg/(mg·h)in the surveyed stations.
基金This study was supported by the National Natural Science Foundation of China under contract No. 497900102.
文摘The distributions of chlorophyll a concentration, primary production and new productionwere observed in the Laizhou Bay of the Bohai Sea in both spring and neap tides during July 1997. The results showed that there were marked features of spatial zonation in the surveyed area, due to the differences between the geographic environment and the hydrological conditions. Chlorophyll a, primary production and new production were all higher in spring tides than that in neap tides in the Laizhou Bay. The highest values of these parameters were encountered in the central regions of the bay. At most stations, chlorophyll a concentrations at the bottom were higher than that at the surface. The results of size-fractionated chlorophyll a and primary production showed that contributions of nanocombining pi-coplankton ( <20 μm) to total chlorophyll a and primary production were dominant in phytoplankton community biomass and production of the Laizhou Bay. The environmental factors, primary production and new production in the Laizhou Bay are compared with other sea areas.
基金This study was supported by the National Natural Science Foundation of China (NSFC) under contract No. 49790010.
文摘During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chi a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be found. Chlorophyll a concentration vertically decreased from surface to bottom in the Liaodong Gulf and the Bohai Gulf, while it increased in the Laizhou Bay, the strait and the central region of the Bohai Sea, and the highest value was encountered at the bottom. Size-fractionation results showed that nano - combining pico -plankton ( < 20 μm) predominated in phytoplankton communities of the Bohai Sea during late spring. The average contribution to total Chl a in each station ranged 76% -95 % (mean is 87 %). The contribution of net (> 20 μm), nano - (2- 20 fan) and picoplankton (< 2 μm) was 13% , 63% and 24% to total production, and 9% , 53% and 38% to total Chl a, respectively. It proved the importance of nano - and pico -plankton in phytoplankton communities in the Bohai Sea e-cosystems. In this paper the factors, such as light intensity and zooplankton grazing pressure, governing standing stock and production of phytoplankton in the Bohai Sea were also discussed.
基金supported by the National Key R&D Program of China (Grant no. 2019YFE0120900)the National Natural Science Foundation of China (Grant nos. 41941013, 41976230, 41206181, and 41976229)
文摘The size structure of phytoplankton has considerable effects on the energy flow and nutrient cycling in themarine ecosystem,and thus is important to marine food web and biological pump.However,its dynamics in the high-latitude Arctic Ocean,particularly ice-covered areas,remain poorly understood.We investigated size-fractionated chlorophyll a(Chl a)and related environmental parameters in the highly ice-covered Arctic Ocean during the summer of 2020,and analyzed the relationship between Chl adistribution and water mass through cluster analysis.Results showed that inorganic nutrients were typically depleted in the upper layer of the Canada Basin region,and that phytoplankton biomass was extremely low(mean=0.05±0.18 mg·m^(−3))in the near-surface layer(upper 25 m).More than 80%of Chl a values were<0.1 mg·m^(−3) in the water column(0-200 m),but high values appeared at the ice edge or in corresponding ice areas on the shelf.Additionally,the mean contribution of both nanoplankton(2-20μm)(41%)and picoplankton(<2μm)(40%)was significantly higher than that of microplankton(20-200μm)(19%).Notably,the typical subsurface chlorophyll maximum(0.1 mg·m^(−3))was found north of 80°N,where the concentration of sea ice reached approximately 100%.The Chl aprofile results showed that the deep chlorophyll maximum of total-,micro-,nano-,and picoplankton was located at depth of 40,39,41,and 38 m,respectively,indicating that nutrients are the primary factor limiting phytoplankton growth in the ice-covered Arctic Ocean during summer.These phenomena suggest that,despite the previous literatures pointing to significant light limitation under the Arctic ice,the primary limiting factor for phytoplankton in summer is still nutrient.
基金a part of“Studies on Response and Feedback Action of Antarctica to the Global Change”,the State tackling key problems project(98-927-01-02)the National Natural Science Foundation of China(No.49876032).
文摘The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12'S, 70°30'E, 73°E and 75(30'E) at December 18-26, 1998 and January 12-18, 1999 in Prydz Bay and its north sea area, Antarctica. The results showed that surface chlorophyll a concentration were 0. 16 -3. 99 μg dm-3. The high values of chlorophyll a concentration (more than 3.5 μg dm -3) were in Prydz Bay and in the west Ladies Bank. The average chlorophyll a concentration at sub-surface layer was higher than that at surface layer; its concentration at the deeper layers of 50 m decreased with increasing depth and that at 200 m depth was only 0. 01 -0. 95μg dm -3. The results of size-fractionated chlorophyll a showed that the contribution of the netplanktion to total chlorophyll a was 56% , those of the nanoplankton and the picoplankton were 24% and 20% respectively in the surveyed area. The potential primary productivity at the euphotic zone in the surveyed area was 0. 11 - 11. 67 mgC m-3h-1 and average value was 2.00 ±2.80 mgC m h . The in-situ productivity in the bay and the continental shelf was higher and that in the deep-sea area was lower. The assimilation number of photosynthesis was 1.53±1. 11 mgC/(mg Chi a · h). The results of size-fractionated primary productivity show that the contribution of the netplanktion to total productivity was 58% , those of the nanoplankton and the picoplankton were 26% and 16% respectively. The cell abundance of phytoplankton was 1. 6 × 103 - 164. 8 × 103 cell dm-3 in the surface water.
基金This research was supported by the project of the Chinese Academy of Sciences (CAS) under the contract No. KZCX2 - 202 the International Cooperation Program of Guangdong Province under the contract No. 99M05004Z the Scienc Foundation Program of Guan
文摘The chlorophyll-a concentration is generally overestimated for the southern China coastalwaters if the default algorithm of the SeaDAS is employed. An algorithm is developed for retrieval of chlorophyll-a concentration in the Zhujiang Estuary, Guangdong Province, China, by using simulated reflectance data. The simulated reflectance is calculated corresponding to the SeaWiFS wavelength bands, via a general model by inputting measured water components, i.e. , the suspended sediment, chlorophyll-a, and yellow substance (DOC) concentration data of 130 samples. Empirical relationships of the chlorophyll-a concentration to 240 different band combinations are investigated based on the simulated reflectance data, and the band combination, R_5R_5/R_3R_4, is found to be the optimum one for the development of an algorithm valid for the Zhujiang Estuary. This algorithm is then employed to determine the chlorophyll-a concentration from SeaWiFS data. The estimated concentrations have a better accuracy than those obtained from the SeaDAS default algorithm when compared with sea truth data. The new algorithm is demonstrated to work well and is used to derive a series of image maps of the chlorophyll-a concentration distribution for the Zhujiang Estuary and adjacent coastal areas.
基金supported by the National Basic Research Program of China (also called 973 Program,Grant Nos.2010CB428904, 2007CB411806,2006CB403600)the National Natural Science Foundation of China under Grant Nos.40775054, 40906012.
文摘The response of the upper-ocean temperatures and currents in the tropical Pacific to the spatial distribution of chlorophyll-a and its seasonal cycle is investigated using a coupled atmosphere-ocean model and a stand-alone oceanic general circulation model.The spatial distribution of chlorophyll-a significantly influences the mean state of models in the tropical Pacific.The annual mean SST in the eastern equatorial Pacific decreases accompanied by a shallow thermocline and stronger currents because of shallow penetration depth of solar radiation.Equatorial upwelling dominates the heat budget in that region.Atmosphere-ocean interaction processes can further amplify such changes. The seasonal cycle of chlorophyll-a can dramatically change ENSO period in the coupled model.After introducing the seasonal cycle of chlorophyll-a concentration,the peak of the power spectrum becomes broad,and longer periods(3 years) are found.These changes led to ENSO irregularities in the model. The increasing period is mainly due to the slow speed of Rossby waves,which are caused by the shallow mean thermocline in the northeastern Pacific.
基金Supported by the National Natural Science Foundation of China (Nos.U0933005,41076014,40906021,41176035)the National High Technology Research and Development Program of China (863 Program)(No.2007AA092001-02)
文摘A previously developed model was modified to derive three phytoplankton size classes (micro-, nano-, and pico-phytoplankton) from the overall chlorophyll-a concentration, assuming that each class has a specific absorption coefficient. The modified model performed well using in-situ data from the northern South China Sea, and the results were reliable and accurate. The relative errors of the size-fractioned chlorophyll-a concentration for each size class were: micro-:21%, nano-:41%, pico-:26%, and nano+pico:23%. The model was then applied on ocean color remote sensing data to examine the distribution and variation of phytoplankton size classes in northern South China Sea on a large scale.
文摘Bayesian regularized BP neural network(BRBPNN) technique was applied in the chlorophyll-α prediction of Nanzui water area in Dongting Lake. Through BP network interpolation method, the input and output samples of the network were obtained. After the selection of input variables using stepwise/multiple linear regression method in SPSS i1.0 software, the BRBPNN model was established between chlorophyll-α and environmental parameters, biological parameters. The achieved optimal network structure was 3-11-1 with the correlation coefficients and the mean square errors for the training set and the test set as 0.999 and 0.000?8426, 0.981 and 0.0216 respectively. The sum of square weights between each input neuron and the hidden layer of optimal BRBPNN models of different structures indicated that the effect of individual input parameter on chlorophyll- α declined in the order of alga amount 〉 secchi disc depth(SD) 〉 electrical conductivity (EC). Additionally, it also demonstrated that the contributions of these three factors were the maximal for the change of chlorophyll-α concentration, total phosphorus(TP) and total nitrogen(TN) were the minimal. All the results showed that BRBPNN model was capable of automated regularization parameter selection and thus it may ensure the excellent generation ability and robustness. Thus, this study laid the foundation for the application of BRBPNN model in the analysis of aquatic ecological data(chlorophyll-α prediction) and the explanation about the effective eutrophication treatment measures for Nanzui water area in Dongting Lake.
基金Supported by the Knowledge Innovation Project of Chinese Academy of Sciences (Nos.KZCX3-SW-214KZCX-YW-213-3)
文摘A one-year field study was conducted to determine the conversion ratio of phytoplankton biomass carbon (Phyto-C) to chlorophyll-a (Chl-a) in Jiaozhou Bay, China. We measured suspended particulate organic carbon (POC) and phytoplankton Chl-a samples collected in surface water monthly from March 2005 to February 2006. The temporal and spatial variations of Chl-a and POC concentrations were observed in the bay. Based on the field measurements, a linear regression model Ⅱwas used to generate the conversion ratio of Phyto-C to Chl-a. In most cases, a good linear correlation was found between the observed POC and Chl-a concentrations, and the calculated conversion ratios ranged from 26 to 250 with a mean value of 56 μg ·μl^-1. The conversion ratio in the fall was higher than that in the winter and spring months, and had the lowest values in the summer. The ratios also exhibited spatial variations, generally with low values in the near shore regions and relatively high values in offshore waters. Our study suggests that temperature was likely to be the main factor influencing the observed seasonal variations of conversion ratios while nutrient supply and light penetration played important roles in controlling the spatial variations.
基金financially supported by the Knowledge Innovation Program of Chinese Academy of Sciencesthe Science and Technology Ministry of China(No.2011CB403604)the IOCAS-Zhangzidao Fishery Eco-Mariculture Joint Laboratory
文摘Nutrient and Chlorophyll-a (Chl-a) concentrations were investigated monthly along three transects extending from a mariculturc area to open waters around the Zhangzi Island area from July to December 2009. The objective of this study is to illus- trate food availability to the bottom-sowed scallop Patinopecten yessoensis under the influences of the Yellow Sea Cold Water Mass (YSCWM), freshwater input and feedbacks of cultivated scallops. Significant thermal stratification was present in open waters from July to October, and salinity decreased in July and August in surface layers in the mariculture area. Nutrient concentrations increased with depth in both areas in summer, but were similar through water column in November and December. On average, nutrient in- creased from summer to autumn in all components except ammonia. Nutrient concentrations lower than the minimum thresholds for phytoplankton growth were present only in upper layers in summer, but stoichiometric nitrogen limitation existed in the entire inves- tigation period. Column-averaged Chl-a concentration was lower in open waters than in mariculture area in all months. It increased significantly in mariculturc area in August and October, and was less variable in open waters. Our results show that nutrients limita- tion to phytoplankton growth is present mainly in upper layer in association with stratification caused by YSCWM in summer. Freshwater input and upwelling of nutrients accumulated in YSCWM can stimulate phytoplankton production in mariculture area. Farming activities may change stoichiometric nutrient ratios but have less influence on Chl-a concentration.
文摘This study investigated the relationships among the parameters of dissolved oxygen, chlorophyll-a and phytoplankton composition in tilapia ponds. Each pond (a total of 18 ponds) was sampled once in the dry, winter season between January and March and again early in the rainy season between May and June. The data were analyzed by examining correlations among parameters as affected by season, altitude and culture system. Observations were made at sites located in 5 selected provinces of northern Thailand: Chiangrai, Chiangmai, Phayao, Lampang and Nakornsawan. Mean elevation of these areas range from 25 to 582 meters above sea level (masl) and were categorized into low (400 masl) elevation sites. Ponds were 0.8 - 2.0 m deep, 0.16 - 0.64 ha in area and could be further categorized into high and low input systems.Mean air temperature in winter ranged between 16.5°C - 35.8°C while mean water temperature ranged between 25.5°C - 27.1°C. In rainy season, air temperature ranged between 22.0°C - 37.3°C and water temperature ranged between 29.4°C - 31.8°C. The amount of chlorophyll-a in both seasons were comparable (p > 0.05), but chlorophyll-a in high input system was significantly higher (p 0.05) than in low input ponds. Only weak correlation was found between chlorophyll-a, DOmax and DOmin. Multifactor-ANOVA was used to analyze the difference of total bacteria and filamentous cyanobacteria in ponds based upon elevation, culture systems and season. Result shows that there is a significant interaction observed between elevation, culture system and season (p 0.05). Species diversity and composition of phytoplankton in fish ponds in 2 seasons revealed the presence of 90 genera of phytoplankton under all 7 divisions. Divisions Chlorophyta and Cyanophyta had the most number of genera identified in both seasons with Pediastrum spp., and Scendesmus spp., and Anabaena spp. as dominant genera/genus, respectively.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Nos. KZCX2-YW-Q11-04 and KZCX2-YW-QN514)the National Basic Research Program of China (Grant Nos. 2007CB816004 and 2012CB417402)the National Natural Science Foundation of China (Grant No. 41075041)
文摘Climatological mean and annual variations of Chlorophyll-a (Chl-a) distribution, sea surface wind (SSW), and sea surface temperature (SST) from 1998 to 2008 were analyzed in the middle of the South China Sea (SCS), focusing on the typical region off the east coast of Vietnam (8.5-14°N, 109.5-114°E). Based on remote sensing data and SCS summer monsoon index (SCSSMI) data, high Chl-a concentrations in the middle of the SCS in the southwest summer monsoon season (June-September) may be related to strong Ekman pumping and strong wind stress. The maximum of the monthly averaged cli- matological Chl-a in the summer appeared in August. According to the annual variation, there was a significant negative correlation (r = -0.42) between the SCSSMI and SST, a strongly positive correlation (r=0.61) between the SCSSMI and Chl-a, and a strongly negative correlation (r = -0.74) between the SST and Chl-a in the typical region off the east coast of Vietnam during 1998-2008. Due to the E1 Nifio event specifically, the phenomena of a low Chl-a concentration, high SST and weak SCSSMI were extremely predominant in the summer of 1998. These relationships imply that the SCSSMI associated with the SST could be used to predict the annual variability of summer Chl-a in the SCS.
基金This study is jointly supported by the National Natural Science Foundation of China under Grant Nos.40233031,40375030,40405017,40523001 and 40775054the National Key Programme 2006CB403600the Chinese Academy of Sciences(CAS)International Partnership Creative Group"The Climate System Model Development and Application Studies".
文摘Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general circulation model. This study indicates that enhanced meridional gradient of chlorophyll-a between the equator and off-equatorial regions can strengthen zonal circulation and lead to a decrease in equatorial sea surface temperature (SST). However, the circulation changes by themselves are not effective enough to affect SST in the equatorial cold tongue (CT) region. The comparison between the experiments indicates that the CT SST are more sensitive to chlorophyll-a distribution away from the equator. The off-equatorial chlorophyll-a traps more solar radiation in the mixed layer, therefore, the temperature in the thermoeline decreases. The cold water can then be transported to the equator by the meridional circulation within the mixed layer. Furthermore, the relation among CT SST, the surface heat flux, and the equatorial upwelling are discussed. The study implies the simulation biases of temperature on the equator are not only related to the local ocean dynamics but also related to some deficiency in simulating off-equatorial processes.
基金Supported by Social Development Project of Guiyang City (2009304,2010503)
文摘[Objective] The aim was to study the relationship between chlorophyll-a and environmental impact factors in deep reservoir in Karst Areas.[Method] Taking Aha Reservoir for example,the changes of chlorophyll-a content and its relationship with environmental impact factors were researched,and the water quality of Aha Reservoir was assessed by means of modified Carlson trophic state index.[Result] Chlorophyll-a content in Aha Reservoir was higher in March,April,May and September and lower from June to August,and there was obvious seasonal variation,namely its variation trend was spring>summer>autumn>winter.In addition,chlorophyll-a content showed extremely significant correlation with transparency and dissolved oxygen (P<0.01) and significant correlation with ammonia nitrogen (P<0.05).Meanwhile,trophic state index was higher in whole year in Aha Reservoir which was in moderate trophic state in August,October and November and eutrophic state in other months.[Conclusion] The study could provide scientific reference for discussing the mechanism of lake eutrophication.