Simulations of Annual Cycle of Phytoplankton Production and the Utilization of Nitrogen in the Yellow Sea (original) (raw)
Continental Shelf Research, 2000
Chemical hydrography, chlorophyll a distribution and primary productivity in the southern East China Sea from the inner shelf to the o!shore region were examined for their temporal and spatial variability based on observations along a cross-shelf transect during 1991}1995. In summer, all surface waters were depleted in nutrients and low in chlorophyll, resulting in widespread subsurface chlorophyll a maxima. In other seasons, shelf waters were usually nutrient-laden, but phytoplankton biomass was limited by light availability in the turbid inner shelf water and the short exposure time of the upwelled water in the outer shelf. The main nitrogen source in the inner shelf was from river runo!. Nitrate de"cit, de"ned as the negative deviation from the conservative mixing line, was well correlated with phytoplankton biomass. In spite of the seasonal and spatial variability of chlorophyll a distribution, the euphotic zone integrated value of chlorophyll a was correlated well with that of primary production in shelf waters. This relationship was used to convert chlorophyll a data from 28 cruises to primary production. The results showed that the lowest productivity on the shelf was in summer with little spatial variation. The elevated primary productivity in the inner shelves in spring was due to a mild spring bloom. On the other hand, the elevated primary productivity in the middle and outer shelves in autumn was due to the intensi"cation of upwelling during the transition of the monsoon. The annual mean values of the euphotic zone integrated primary production in the shelf waters were quite uniform (513}576 mgC m\ d\) with an overall mean of 549$84 mgC m\ d\. The o!shore Kuroshio Water showed a weak seasonal variation 0278-4343/00/$ -see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 7 8 -4 3 4 3 ( 9 9 ) 0 0 0 7 9 -5 Fig. 1. Station locations for the KEEP-Box (ᮀ), KEEP-Key (᭡) cruises and Cruise 414 (;).
I. Monitoring Spring Phytoplankton Bloom Progression in
2013
There is evidence that primary productivity is inhibited in Suisun Bay, and that NH4 may be causing that inhibition. The main purpose of this study is to measure nutrients, primary production, nutrient uptake by phytoplankton and, phytoplankton biomass and species composition in Suisun Bay in the spring to determine if there is inhibition, and if so, to determine what is causing the inhibition. Suisun Bay is an area identified as critical habitat for the threatened Delta Smelt (Hobbs et al., 2006). Several important changes in the pelagic food web of this area have been documented over the last two decades indicating that food for Delta Smelt and other threatened fishes is in short supply (Müeller-Solger et al. 2002; Sommer et al. 2007). One of the most striking changes in Suisun Bay is the decline in phytoplankton between 1975- 1995 (Jassby et al. 2002) and the shift from large accumulations of phytoplankton biomass (>40 μg L-1 chlorophyll) during the summer (Cloern 1979) to muc...
Journal of Geophysical Research, 2004
1] Two cruises were carried out in the summer and winter of 1998 to study coupled physical-chemical-biological processes in the South China Sea and their effects on phytoplankton stock and production. The results clearly show that the seasonal distributions of phytoplankton were closely related to the coupled processes driven by the East Asian Monsoon. Summer southwesterly monsoon induced upwelling along the China and Vietnam coasts. Several mesoscale cyclonic cold eddies and anticyclonic warm pools were identified in both seasons. In the summer, the upwelling and cold eddies, both associated with rich nutrients, low dissolved oxygen (DO), high chlorophyll a (Chl a) and primary production (PP), were found in the areas off the coast of central Vietnam, southeast of Hainan Island and north of the Sunda shelf, whereas in the winter they form a cold trough over the deep basin aligning from southwest to northeast. The warm pools with poor nutrients, high DO, low Chl a, and PP were found in the areas southeast of Vietnam, east of Hainan, and west of Luzon during the summer, and a northwestward warm jet from the Sulu Sea with properties similar to the warm pools was encountered during the winter. The phytoplankton stock and primary production were lower in summer due to nutrient depletion near the surface, particularly PO 4 . This phosphorus depletion resulted in phytoplankton species succession from diatoms to dinoflagellates and cyanophytes. A strong subsurface Chl a maximum, dominated by photosynthetic picoplankton, was found to contribute significantly to phytoplankton stocks and production.
Nutrients and mixing, chlorophyll and phytoplankton growth
Deep Sea Research Part A. Oceanographic Research Papers, 1990
, we observed an event of windinduced mixing during a 4-day sequence of observations while operating in a Lagrangian sampling mode. The sharp increase in wind stress was followed by a sharp increase in nitrate concentration in the euphoric zone. The nitrate declined rapidly, and over the next 2 days the quantity of chlorophyll a in the ¢uphotic zone increased by a factor of three. The phytoplankton community was dominated by diatoms; this and other evidence indicates that the events observed were part of the spring bloom in the north Sargasso Sea. These observations are interpreted in terms of laboratory models for nutrient-dependent phytoplankton growth. The cell-quota model of Caperon and Droop provides an internally consistent explanation of the observed data. The data also suggest the notion of "nutrient switching" (rather than a multiplicative form of nutrient interaction) in the interaction of nitrate and silicate, although this could not be verified.
Limnology and Oceanography, 2003
Simulation modeling provides a means for testing the limits of our quantitative understanding of the factors that control phytoplankton biomass, growth rate, and primary productivity in the sea. We simulated the annual cycles of chlorophyll a (Chl a) concentration, primary productivity, nitrogen export, phytoplankton carbon to nitrogen (C : N) and carbon to Chl a ratios (C : Chl a) using a physiological model of phytoplankton carbon, nitrogen, and Chl a dynamics. The model was embedded within a one-dimensional physical model of vertical exchanges that included simple mortality and recycling terms. A sensitivity analysis allowed evaluation of the relative effects of changes in phytoplankton physiology, physical forcing, mortality, and nutrient cycling on Chl a distributions and phytoplankton C : N. Critical to the success of the model was the treatment of mortality, which included seasonal (temperature) and depth-related components, and the treatment of recycling efficiency, which was considered to be a function of the inorganic nitrogen concentration. The subtropical simulation compared favorably with data obtained at the Bermuda Atlantic Time-series Study (BATS) station. Our results illustrate the utility of physiological data in validation of biogeochemical models. In particular, model predictions of phytoplankton C : Chl a, which ranged from 30 to 170 g C (g Chl a) Ϫ1 , compared well with direct estimates based on 14 C labeling of Chl a. However, predictions of phytoplankton C : N, which ranged from ϳ5-9 g C (g N) Ϫ1 , could not be verified because of lack of data. This range of C : N suggests a slight limitation of phytoplankton growth rates by nutrients in surface waters.
2009
Two field studies were conducted to measure pigments in the Southern Yellow Sea (SYS) and the northern East China Sea (NECS) in April (spring) and September (autumn) to evaluate the distribution pattern of phytoplankton stock (Chl a concentration) and the impact of hydrological features such as water mass, mixing and tidal front on these patterns. The results indicated that the Chl a concentration was 2.43±2.64 (Mean ± SD) mg m -3 in April (range, 0.35 to 17.02 mg m -3 ) and 1.75±3.10 mg m -3 in September (from 0.07 to 36.54 mg m -3 ) in 2003. Additionally, four areas with higher Chl a concentrations were observed in the surface water in April, while two were observed in September, and these areas were located within or near the point at which different water masses converged (temperature front area). The distribution pattern of Chl a was generally consistent between onshore and offshore stations at different depths in April and September. Specifically, higher Chl a concentrations were observed along the coastal line in September, which consisted of a mixing area and a tidal front area, although the distributional pattern of Chl a concentrations varied along transects in April. The maximum Chl a concentration at each station was observed in the surface and subsurface layer (0-10 m) for onshore stations and the thermocline layer (10-30 m) for offshore stations in September, while the greatest concentrations were generally observed in surface and subsurface water (0-10 m) in April. The formation of the Chl a distributional pattern in the SYS and NECS and its relationship with possible influencing factors is also discussed. Although physical forces had a close relationship with Chl a distribution, more data are required to clearly and comprehensively elucidate the spatial pattern dynamics of Chl a in the SYS and NECS.
Phytoplankton chlorophyll distributions and primary production in the Southern Ocean
Journal of Geophysical Research, 2000
Satellite ocean color data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) were used to examine distributions of chlorophyll concentration within the Southern Ocean for the period October 1997 through September 1998. Over most of the Southern Ocean, mean chlorophyll concentrations remained quite low (<0.3-0.4 mg m-3). Phytoplankton blooms where chlorophyll concentration exceeded 1.0 mg m-3 were observed in three general areas, which included coastal/shelf waters, areas associated with the seasonal sea ice retreat, and the vicinity of the major Southern Ocean fronts. These chlorophyll distribution patterns are consistent with an iron-limited system. Mean chlorophyll concentrations from SeaWiFS are compared with values from the coastal zone color scanner (CZCS). The SeaWiFS global chlorophyll algorithm works better than the CZCS in Southern Ocean waters. Primary production in the Southern Ocean was estimated with the vertically generalized production model of Behrenfeld and Falkowski [1997]. Annual primary production in the Southern Ocean (>30øS) was estimated to be 14.2 Gt C yr-•, with most production (-80%) taking place at midlatitudes from 30 ø to 50øS. Primary production at latitudes >50øS was estimated to be 2.9 Gt C yr-•. This is considerably higher than previous estimates based on in situ data but less than some recent estimates based on CZCS data. Our estimated primary production is sufficient to account for the observed Southern Hemisphere seasonal cycle in atmospheric 02 concentrations. 1. Sea. Several studies combined CZCS data with satellitederived ice cover information to examine ice edge phytoplankton bloom dynamics [Sullivan et al., 1988; Comiso et al., 1990]. Comiso et al. [1993] examined CZCS pigment data for the entire Southern Ocean and analyzed their relationship to several geophysical features. They noted that phytoplankton blooms occur primarily in several regions including areas as-•Now at Advanced Studies Program, National Centers for Atmospheric Research, Boulder, Colorado.
Ecological Modelling, 2016
The East Sea (Japan Sea) ecosystem has experienced a significant warming and ever-increasing anthropogenic atmospheric deposition of nitrogen during recent decades. To understand the impacts of such environmental changes on the planktonic community, we set up a zero-dimensional European Regional Seas Ecosystem Model (ERSEM) in the Ulleung Basin, East Sea for the years 2001-2012. The model results show that as the winter maximum mixed layer depth (MMLD) changes, the growth and grazing loss of phytoplankton functional types (PFTs) are affected differently, resulting in differential success of PFTs in the upper mixed layer. Diatoms preempted the early spring growth by better utilization of light and nitrate. Diatoms' advantages lessened as the MMLD decreased. Flagellates and picophytoplankton showed mixed responses to decreased MMLD. Their net primary productivity (NPP) and peak biomass decreased but their annual biomass increased due to decreased grazing. Dinoflagellates always did better when MMLD decreased. The model results also indicate that with an increase in atmospheric deposition, the picophytoplankton and the flagellates increased in summer, whereas the dinoflagellates and the diatoms decreased. For the study period, the atmospheric deposition in the Ulleung Basin increased the annual net primary production by 4.58% (mean; range 3.77-10.58%). Biological variables showed the largest responses in summer with high year-to-year variability. Picophytoplankton increased the most (summer increase mean: 23.23%; summer increase range: 9.12-42.6%) while dinoflagellates decreased the most (summer decrease mean: −2.33%; summer decrease range: −9.09 to 10.13%). The changes in flagellates and diatoms were much less. Taking the results together, it is likely that as the warming and atmospheric deposition continue to intensify into the future; the phytoplankton community in the region will shift to smaller phytoplankton with consequent changes of food web structure to follow.
Physical control of spring–summer phytoplankton dynamics in the North Water, April–July 1998
Deep Sea Research Part II: Topical Studies in Oceanography, 2002
A 4-month multidisciplinary expedition, beginning at the end of winter to track the spring phytoplankton bloom to its terrnination in summer, was conducted from April to July 1998. The aim of the expedition was to investigate possible mechanisms responsible for the high biological productivity of the North Water, the most productive and largest polynya in the Northern Hemisphere. The aims of the present study were to investigate: (1) the effects of the physical forces, driving the formation of the polynya, on the dynamics of the phytoplankton stock in the polynya over the spring-summer period; and (2) the factors that limit the maximum biomass of phytoplankton. Contrasting physical characteristics, including ice concentration, surface mixed-layer depth (MLD), salinity and tempe rature in the surface mixed layer (SML), were observed between the east and west sides of the polynya. The Greenland (eastern) side of the polynya was characterized by a shallow SM L, wann temperature, and high sali nit y relative to the Ellesmere Island, Canada (western) side. Chlorophyll a (Chi) > 1 mg m-3 was observed in la te April on the eastern side, and in late May on the western side. The peak phytoplankton bloom occurred in the southeastern part of the polynya, with average Chi of 15mgm-3 (24o-300mgm-1 in the euphotic zone during the end of May and beginning of June. The increased phytoplankton biomass was associated with higher salinity and wanner tempe rature on the eastern side of the polynya. Low temperature in April and May decoupled the increase of Chi biomass from the shallowed SML, as predicted by Sverdrup's model. As Chi in the euphotic zone increased to 5 mg m-3, the proportion of light absorption by phytoplankton could not increase further with Chi biomass, which might have limited the increase of primary production in the water column. Although the initial nutrient inventories largely detennined the maximum biomass of phytoplankton, self-shading occurred in the build-up phytoplankton biomass to -5mgm-3, which retarded the timing of the peak bloom. Both sensible heat due to deep warm water entrainment into the SML and the biological heating .Corresponding author.