Phytoplankton Carbon Production Research Articles

Modeling Spatiotemporal Patterns of Ecosystem Metabolism and Organic Carbon Dynamics Affecting Hypoxia on the Louisiana Continental Shelf.

The hypoxic zone on the Louisiana Continental Shelf (LCS) forms each summer due to nutrient enhanced primary production and seasonal stratification associated with freshwater discharges from the Mississippi/Atchafalaya River Basin (MARB). Recent field studies have identified highly productive shallow nearshore waters as an important component of shelf-wide carbon production contributing to hypoxia formation. In this study we present results from a three-dimensional hydrodynamic-biogeochemical model named CGEM (Coastal Generalized Ecosystem Model) applied to quantify the spatial and temporal patterns of hypoxia, carbon production, respiration, and transport between nearshore and middle shelf regions where hypoxia is most prevalent. We first demonstrate that our simulations successfully reproduced spatial and temporal patterns of carbon production, respiration, and bottom-water oxygen gradients compared to field observations. We then used interannual simulations to identify transport of particulate organic carbon (POC) from nearshore areas where riverine organic matter and phytoplankton carbon production are greatest. The spatial disconnect between carbon production and respiration in our simulations was driven by westward and offshore POC flux, a pattern that supported heterotrophic respiration on the middle shelf where hypoxia is frequently observed. These results validate the importance of offshore carbon flux to hypoxia formation, particularly on the west shelf where hypoxic conditions are more variable.

Concentrations, Sources, and Dry Deposition Fluxes of Different Forms of Phosphorus in Qingdao Aerosols in Summer

Total suspended particulate (TSP) samples were collected in Qingdao from June to July 2016. Different forms of phosphorus in these samples-including total phosphorus (TP), dissolved phosphorus (DP), dissolved inorganic phosphorus (DIP), and dissolved organic phosphorus (DOP) were analyzed to investigate their distribution characteristics and sources, as well as their dry deposition fluxes. Results showed that the mass concentration of TP in aerosols was (49.3±30.6) ng·m-3, and the concentration of DP was (15.5±10.4) ng·m-3, accounting for 30.9%±11.0% of TP. DIP dominated in dissolved state P, contributing about 60%. The sources of different forms of P were analyzed, showing that the P in Qingdao aerosols in summer was derived from both crustal and anthropogenic sources, with the latter including biomass burning and agricultural fertilization. TP was mainly derived from soil sources, which contributed 38%, while the contribution of agricultural activities and industrial sources was about 20%. DIP in DP was mainly derived from agricultural activities and combustion sources, with contributions of 51% and 24%, respectively. DOP was mainly derived from soil sources and agricultural activities, contributing 41% and 27% respectively. The dry deposition flux of TP in Qingdao was (51.7±31.7) μg·(m2·d)-1, of which 23.2%±8.2% was the water-soluble fraction. DOP in the total dry deposition flux of DP was non-negligible, accounting for 40%. The atmospheric deposition of soluble P would support phytoplankton carbon production of (0.5±0.3) mg·(m2·d)-1, contributing about 1% to new productivity in the Yellow Sea.

Concentration, Solubility, and Dry Deposition Flux of Trace Elements in Fine and Coarse Particles in Qingdao During Summer

PM2.5 and total suspended particulate (TSP) samples were synchronously collected in Qingdao from June to July 2016. The total and water-soluble concentrations of 12 trace elements in these samples were analyzed to investigate their distribution characteristics in fine and coarse particles as well as their dry deposition fluxes. The results showed that the total mass concentrations of Al, Fe, Sr, Mn, and Ba, which are expected to mainly originate from crustal sources, were generally distributed in the coarse particles, and the part mass in the coarse mode accounted for 55%-60% of their total concentrations. Cr, Ni, V, Zn, Pb, As, and Cd, which mainly originate from anthropogenic contributors, generally existed in fine particles where the part mass accounted for 65%-85% of their total concentrations. The soluble mass concentrations of trace elements, whether from crustal or anthropogenic sources, were mainly distributed in the fine particles. The proportions of Al, Fe, Mn, and Ba in soluble mass concentration existing in the fine particles were 50%-80% and 70%-90% for Cr, Ni, V, Zn, Pb, As, and Cd. The solubility of trace elements was higher in fine particles than in coarse particles. The soluble concentrations of trace elements exhibited a positive correlation with acid compounds, and the solubility exhibited a negative correlation with pH in the fine particles, implying that acidification processes play a key role in determining the solubility of trace elements in fine particles. The soluble fractions in the total dry deposition flux of Al and Fe were only 1%-2%; that of Sr, Ba, Cr, and Pb were about 30%-40%; and that of Mn, Ni, V, Zn, As, and Cd were about 50%-60%. The atmospheric deposition of soluble Fe supported phytoplankton carbon production of (194±150) mg·(m2·d)-1, contributing about 10% of the primary productivity in the Yellow Sea.

The production of organic carbon by phytoplankton in Lake Taihu and its influence factors

2007年1-12月对中国科学院太湖湖泊生态系统站栈桥附近进行了每月1次以及太湖4个典型湖区每季度1次的有机碳生产实验,分析了太湖浮游植物群落的有机碳生产情况及其影响因子.结果表明,浮游植物有机碳生产与光照、温度以及浮游植物的群落组成有着密切的关系.春、夏季浮游植物光合效率比秋、冬季高,空间上蓝藻占优势的湖区较高,水草区较低.;The organic carbon production of phytoplankton near the Trestle monthly and at four stations quarterly in Lake Taihu fromJanuary 2007 to December 2007 was investigated, and its influence factors were analyzed. The results showed that there wereobvious temporal and spatial differences in the production of organic carbon in Lake Taihu. The high values of organic carbonproduction were recorded in spring and summer. The production of organic carbon was higher in the area where the phytoplanktonwas dominated by Cyanophyta and lower in the aquatic areas.

Net heterotrophy in productive prairie wetlands with high DOC concentrations

Millions of productive wetlands dot the North American Great Plains. Although these wetlands are key ecological features of the Canadian prairies, their microbial food webs remain relatively unstudied. Over 3 yr, pelagic primary (PP) and bacterial production (BP) and biomass were monitored in 2 wetlands in Central Saskatchewan, Canada. PP ranged from 8.8 to 3911.0 mg C m -3 d -1 (x = 612.0 mg C m -3 d -1 ), while rates of BP ranged from 8.2 to 678.0 mg C m -3 d -1 (x = 140.0 mg C m -3 d -1 ). Nutrients, light and temperature did not appear as major factors influencing these rates. Seasonal mean ratios of PP:BP revealed that both wetlands were net autotrophic (x PP:BP = 7.4; range 0.08 to 42.6), which was not surprising given their eutrophic status. On a smaller temporal scale, these wetlands were, on average, net heterotrophic (PP:BP < 1) on 33% of the sampling dates. High pelagic bacterial carbon demand (greater than twice the phytoplankton carbon production) indicated that bacterial metabolism was not dependent on autochthonous carbon sources. Biological availability of dissolved organic carbon (DOC) was low in both wetlands (x = 3.8%). But this percentage of high ambient concentrations was enough to satisfy bacterial carbon demand. Based on seasonal averages, BP and bacterial numbers decreased across increasing trophic gradients (as chl a or total phospho- rus). This phenomenon could also be observed across a seasonal gradient of changing chl a concen- trations. Prairie wetlands not only experience periods of net heterotrophy, but bacterial carbon demand and production per unit biomass are high, suggesting an important role for bacteria in the metabolism of these eutrophic ecosystems.

Ocean annual phytoplankton carbon and new production, and annual export production estimated with empirical equations and CZCS data

Summary Empirical equations are parameterized for use with chlorophyll a, derived from satellite ocean colour data, to calculate phytoplankton carbon production, phytoplankton new production, and export production. For environments in a high variance (HV) pigment statistical class, annual phytoplankton particulate organic carbon production (AIP) is linearly related to annual average in situ chlorophyll a within the near-surface layer. Linear relations were also obtained between AIP and annual new nitrogen production, and between AIP and particulate organic carbon annually exported from the euphotic zone for environments in that class. We found no relation between AIP and CSFC, or between the annual production variables, for oceanic environments characterized by low pigment variance (LV). Ratios of export production to AIP, called e, and new production to nitrogen annually used in phytoplankton production, called f, are widely used to express marine food web processes. The trends of these ratios with AIP differ between HV and LV environments. This is a result of differences in the coupling between nitrogen and carbon transfer in pelagic food webs, which contain different organism size classes in HV compared to LV environments. We applied the empirical equations to CZCS data to estimate global new and export production. The HV environments are responsible for about 40% of global ocean annual phytoplankton carbon production and 70% of global ocean annual new and export production.

Dynamics in bacterioplankton production in a shallow, temperate lake (Lake Neusiedl, Austria): evidence for dependence on macrophyte production rather than on phytoplankton

The seasonal dynamics in bacterioplankton abundance and production were studied at 3 characteristic stations (open water, large pond within the reed belt and within the reed Phragmites australis) in the shallow Lake Neusiedl, Austria, and related to phytoplankton primary production and dissolved organic carbon (DOC). DOC concentrations ranged from about 1 to 2.5 mm01 1-' with humic DOC contributing between 4 0 % during the winter and 55% during the summer. Phytoplankton production was highest in the pond withln the reed belt, where the attenuation was lowest, reaching 110 mg C m-' d-' during a distinct phytoplankton bloom in August. Bacterial abundance ranged from 2 X 106 cells ml-' during winter to about 10 X 10' cells ml-l during summer. Bacterial production calculated by thymidine (TdR) and leucine (leu) incorporation, respectively, were in good agreement at the stations in the reed belt, but bacterial production based on leu incorporation was significantly lower than bacterial production based on TdR incorporation at the open water station. Based on a bacterial growth yield of 16% determined in an earlier study, bacterioplankton carbon demand was always at least 1 order of magnitude higher than carbon production of phytoplankton, indcating that bacterioplankton metabohsm in Lake Neusiedl is heavily dependent on non-phytoplankton sources of DOC. The bacterial carbon demand (ranging from 225 to 870 mg C m-2 d-' depending on the sampling site and substrate used) could be matched by the production of the reed P. australis amounting to 750 to 4510 mg C m-* d-'. Since there is no major allochthonous organic matter input from other sources, this macrophyte production is obviously channeled to the pelagic food web via the bacterioplankton.

Zooplankton and micronekton biomass off Somalia and in the southern Red Sea during the SW monsoon of 1992 and the NE monsoon of 1993

Spatial and seasonal variations in mesozooplankton, macrozooplankton and micronekton biomass distribution were studied in the Somali Basin and the southern Red Sea and Gulf of Aden. Cruises were made in May–June and July–August 1992 during the SW monsoon, and in January–February 1993 during the NE monsoon. Samples were taken in day and night series from stratified layers to depths of 600 or 1000 m, using an RMT1 + 8, combining two nets with mesh size of 0.34 mm and 4.5 mm, respectively. During the SW monsoon the mean zooplankton biomass from RMT1 samples (displacement volume 0–300 m, night) were low in the southern Red Sea and the Gulf of Aden, 14.0–17.5 ml m-2. At 11°N in the Somali Current, where coastal upwelling occurs, the maximum biomass value of 38.0 ml m −2 was recorded. Downstream from the upwelling in the Great Whirl, biomass values were lower, ranging from 21.0 to 35.9 ml m −2. In the Somali Basin south of 5°N the mesozooplankton biomass was lower than in the Somali Current and northern areas. During the NE monsoon large phytoplankton blooms occurred in the southern Red Sea and the Gulf of Aden, and the mean zooplankton biomass almost doubled to 23.9–40.2 ml m −2 compared with the SW monsoon. Primary production in the northern Somali Basin was much higher during the NE monsoon than recorded during earlier studies, and biomass values for the zooplankton therefore were not as low as might be expected. No statistical significant difference was found in the season's mean biomass values. This is remarkable because in the northern Somali Basin the mean phytoplankton carbon production during the NE monsoon was about two-thirds of the production during the SW monsoon. This seeming paradox is probably due to large mesh sizes that did not retain the small size (herbivorous) zooplankton fraction present during the SW monsoon. The mean macrozooplankton and micronekton biomass from RMT8 samples (0–300 m night) in the southern Red Sea, the Gulf of Aden and the Somali Basin showed no significant seasonal difference. However, biomasses of mesopelagic fish and large crustaceans were high in the southern Red Sea during the SW monsoon, and were high in the Somali Current during the NE monsoon, whereas in the northern Somali Basin biomasses remained about the same. Biomasses of large crustaceans in the Gulf of Aden were higher during the NE monsoon. The pelagic swimming crab Charybdis smithii was found during the SW monsoon in the equatorial and northern Somali Basin, attaining high displacements. The species was not found in the Somali upwelling area during this season, whereas during the NE monsoon the highest displacements for C. smithii were recorded. Vertical profiles of biomass from RMTI and RMT8 samples show that zooplankton and micronekton occur in the oxygen minimum zone and that the lowest oxygen concentrations in the sampled depth range (0.11 ml 1 −1) do not seem to hamper diurnal vertical migration.