Distribution characteristics of size-fractionated chlorophyll a and primary productivity in Beibu Gu

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The size-fractionated chlorophyll a and primary productivity in the Bering Sea during the summer of 2003

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 0.199～1.170 μg/dm^3, and the average value was 0.723 μg/dm^3 on the BR line. For the BSline, the surface chlorophyll a concentrations were 0.519～4.644 μg/dm^3 (average 1.605 μg/dm^3)and 0.568～14.968 μg/dm^3 (average 5.311 μg/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 4.0 μg/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.

Variability of size-fractionated phytoplankton standing stock in the Amundsen Sea during summer

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.

Variability of size-fractionated chlorophyll a in the high-latitude Arctic Ocean in summer 2020

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.

The distribution feature of size-fractionated chlorophyll a and primary productivity in Prydz Bay and its north sea area during the austral summer

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.

Distribution characteristics of size-fractionated chlorophyll a, primary production and new production in the Laizhou Bay, July 1997

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.

Size-fractionated phytoplankton standing stock and primary production in the Bohai Sea during late spring

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.

Standing stock of phytoplankton and primary productivity in Penaeus orientalis larval multiplication releasing area of the Xiangshan Bay

The standing stock of phytoplankton (phy. ) and primary productivity (pp) in the Xiangshan Bay were observed in 1992. The results showed higher biological parameters in the bay. The average chlorophyll a (chl a) concentration was (3. 50 5. 93 ) mg/m3 and the primary productivity (444. 5 871. 0) mg/(m2 d). The distribution of chl a and productivity showed distinct spatial and temporal patterns in the bay. The continent influence was Obvious at the top of the bay, lower seawater exchange and higher stability led to higher standing stock of phytoplankton and productivity. At the bay mouth, seawater exchanged continuously with adjacent waters by rapid currents, resulting in fast and unstable exchange and lower standing stock of phytoplankton and primary productivity. The seasonal characters of those parameters were pronounced, in the sequence of spring, summer, autumn and winter. The results of size--fractionated showed that the average contribution of the nano--and picoplankton (< 20pm) to total chl a and productivity were 75 % and 87%, respectively, indicating their importance in phytoplankton community biomass and productivity of the Xiangshan Bay.

Response of Phytoplankton Community Structure and Size- Fractionated Chlorophyll a in an Upwelling Simulation Experiment in the Western South China Sea

The South China Sea(SCS), which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure(PCS) response to the upwelling remains inadequate. In January 2014, the upwelling simulation experiment was performed in the western SCS. Results indicate that the nutrient-rich bottom water not only increased the total Chlorophyll a(Chl a) concentrations, but would potentially altered the PCS. Due to new nutrients added, microphytoplankton had more sensitivity response to nutrient uptake than other phytoplankton groups. The variation of nutrients induced by formation, weakening and disappearance of upwelling resulted in phytoplankton species succession from cyanophyta to bacillariophyta. It may be the leading factor of the changes in PCS and size-fractionated Chl a. The initial concentration of DIP less than 0.1 μmol L-1 could not sustain the phytoplankton growth. This indicates that phosphorus may be the limiting factor in the western SCS.

Size fractionated biomass and productivity of phytoplankton and new production in the Prydz Bay and the adjacent Indian sector of the Southern Ocean during the austral summer 1998/1999

The paper deals with the studies on the cell abundance, the composition of dominant species, size fractionated biomass and productivity of phytoplankton, new production, the environmentally restricted mechanism in the Prydz Bay and the adjacent Indian sector of the Southern Ocean during the austral summer 1998/1999. The results showed that there was marked feature of spatial zonation in the sea areas investigated. In the Prydz Bay and its adjacent continental shelf, the biomass and productivity of phytoplankton were high; those of continental slope and open ocean area were obviously low. The nutrient concentration had opposite distribution trend, due to the consumption of phytoplankton. It mainly affected by the vertical stability of water column, grazing pressure of zooplankton, temperature and light etc. The results of size-fractionation showed that the average contribution of netplankton to total chlorophyll a in studied sea areas was 52.2 %, those of nano- and picoplankton were 29.4 % and 18.4 %, respectively. The average contribution of netplankton to total primary production was 52.4 %, those of nano- and picoplankton were 28.7 % and 18.9 %, separately. It is same as previous conclusion that the contribution of picoplankton to productivity is slightly larger than that to biomass of phytoplankton communities. The average new production and f-ratio were 230.6 mg/ (m(2.)d) and 0.43, respectively.

PHYTOPLANKTON BIOMASS(chl a)IN THE TAIWAN STRAIT(1997-1999)

The concentration, distribution, size-fraction structure and diurnal variation of phyto-plankton biomass (chl a) in the Taiwan Strait were investigated during four cruises conducted in the sum-mer (August) of 1997, 1998, 1999 and winter (February-March ) of 1998, respectively. The resultsshowed that phytoplankton biomass in the Taiwan Strait was largely influenced by water masses and up-welling, high biomass mainly occurred at the frontal zones. Nano-and pico-phytoplankton dominated thephytoplankton biomass and primary productivity in the Taiwan Strait, they contributed 60%-80% to bi-

Identification of sources of lead in the atmosphere by chemical speciation using X-ray absorption near-edge structure(XANES) spectroscopy

Sources of Pb pollution in the local atmosphere together with Pb species, major ions, and heavy metal concentrations in a size-fractionated aerosol sample from Higashi-Hiroshima （Japan） have been determined by X-ray absorption near-edge structure （XANES） spectroscopy, ion chromatography, and ICP-MS/AES, respectively. About 80% of total Pb was concentrated in fine aerosol particles. Lead species in the coarse aerosol particles were PbC204, 2PbCO3-Pb（OH）2, and Pb（NO3）2, whereas Pb species in the fine aerosol particles were PbC204, PbSO4, and Pb（NO3）2. Chemical speciation and abundance data suggested that the source of Pb in the fine aerosol particles was different from that of the coarse ones. The dominant sources of Pb in the fine aerosol particles were judged to be fly ash from a municipal solid waste incinerator and heavy oil combustion. For the coarse aerosol particles, road dust was considered to be the main Pb source. In addition to Pb species, elemental concentrations in the aerosols were also determined. The results suggested that Pb species in size-fractionated aerosols can be used to identify the origin of aerosol particles in the atmosphere as an alternative to Pb isotope ratio measurement.