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1.
Realistic modelling of marine ecosystems is necessary for improving our understanding of the ocean’s biogeochemical state and for predicting their response to anthropic perturbations. An essential step in achieving this task is the use of mechanistic formulations to describe the biogeochemical processes involved in the dynamics of marine pelagic ecosystems. This study provides a review on some modelling strategies for some of the key processes involved in the dynamics of phytoplankton. It encompasses the most advanced work in terms of mechanistic understanding and, therefore, mainly deals with photosynthesis (including photoacclimation and photoinhibition), respiration, and nutrient uptake (including multi-limitation of algal growth by nutrients). We highlight, that in many ecosystem models, phytoplankton processes are still described more or less empirically, mainly due to a lack of biochemical knowledge, or if a mechanistic formulation exists, the parameters are often difficult to assess experimentally. As a result of this investigation, a preliminary structure for a generic phytoplankton model is delivered in the last section of this paper. This model includes a mechanistic representation of photosynthesis/photoinhibition based on photosystem II status, as well as new formulations for photoacclimation and dissolved organic matter exudation processes. The model sensitivity analysis with regard to its parameters and a comparison with chemostat experimental data are presented in a companion paper [Baklouti, M., Faure, V., Pawlowski, L., Sciandra, A., 2006. Investigation and sensitivity analysis of a mechanistic phytoplankton model implemented in a new modular numerical tool (Eco3M) dedicated to biogeochemical modelling. Progress in Oceanography]. Finally, this new class of multi-element, multi-species phytoplankton models will provide the basis for future studies on ecosystem modelling. 相似文献
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3.
Remote sensing applications are important in the fisheries sector and efforts were on to improve the predictions of potential fishing zones using ocean color. The present study was aimed to investigate the phytoplankton dynamics and their absorption properties in the coastal waters of the southeastern Arabian Sea in different seasons during the year 2010 to 2011. The region exhibited 73 genera of phytoplankton from 19 orders and 41 families. The numerical abundance of phytoplankton varied from 14.235×103 to 55.075×106 cells/L. Centric diatoms dominated in the region and the largest family identified was Thalassiosiraceae with main genera as Skeletonema spp., Planktionella spp. and Thalassiosira spp. Annual variations in abundance of phytoplankton showed a typical one-peak cycle, with the highest recorded during premonsoon season and the lowest during monsoon season. The species diversity index of phytoplankton exhibited low diversity during monsoon season. Phytoplankton with pigments Chlorophyll a, Chlorophyll b, Chlorophyll c, peridinin, diadinoxanthin, fucoxanthin, β-carotene and phycoerythrobilin dominated in these waters. The knowledge on phytoplankton dynamics in coastal waters of the southeastern Arabian Sea forms a key parameter in bio-optical models of pigments and productivity and for the interpretation of remotely sensed ocean color data. 相似文献
4.
Phytoplankton species interact through competition for light and nutrients; they also interact through grazers they hold in common. Both interactions are expected to be size-dependent: smaller phytoplankton species will be at an advantage when nutrients are scarce due to surface/volume considerations, while species that are similar in size are more likely to be consumed by grazers held in common than are species that differ greatly in size. While phytoplankton competition for nutrients and light has been extensively characterized, size-based interaction through shared grazers has not been represented systematically. The latter situation is particularly unfortunate because small changes in community structure can give rise to large changes in ecosystem dynamics and, in inverse modeling, to large changes in estimated parameter values. A simple, systematic way to represent phytoplankton interaction through shared grazers, one resistant to unintended idiosyncrasy of model construction yet capable of representing scientifically justifiable idiosyncrasy, would aid greatly in the modeling process.Here I develop a model structure that allows systematic representation of plankton interaction. In this model, the zooplankton community is represented as a continuous size spectrum, while phytoplankton species can be represented individually. The mechanistic basis of the model is a shift in the zooplankton community from carnivory to omnivory to herbivory as phytoplankton density increases. I discuss two limiting approximations in some detail, and fit both to data from the IronEx II experiment. The first limiting case represents a community with no grazer-based interaction among phytoplankton species; this approximation illuminates the general structure of the model. In particular, the zooplankton spectrum can be viewed as the analog of a control rod in a nuclear reactor, which prevents (or fails to prevent) an exponential bloom of phytoplankton. A second, more complex limiting case allows more general interaction of phytoplankton species along a size axis. This latter case would be suitable for describing competition among species with distinct biogeochemical roles, or between species that cause harmful algal blooms and those that do not. The model structure as a whole is therefore simple enough to guide thinking, yet detailed enough to allow quantitative prediction. 相似文献
5.
Three types of primary productivity (PP) models were evaluated in a mesoscale area around the South Shetland Islands (Antarctica). Input variables were: phytoplankton carbon biomass, Chlorophyll a, sea water temperature, daily irradiance, among others, collected in situ during an oceanographic cruise (COUPLING, January 2010). Models of the first type were based on Chl a measurements: the widely used model VGPM (Behrenfeld and Falkowski, 1997) and a derived version developed for the Western Antarctic Peninsula (Dierssen et al., 2000). The second type included two models based on phytoplankton carbon biomass: one developed for the whole Southern Ocean (Arrigo et al., 2008) and one based on the Metabolic Theory of Ecology developed by López-Urrutia et al. (2006), being the first time that a model with these features is used for Antarctic waters. The third type was an updated version of the carbon-based model CbPM (first described by Behrenfeld et al. (2005)) based on the Chl a/carbon biomass ratio modulation. The degree of agreement among the results between the different types of models turned out to be low (> 30% of difference), but high within models of the same type (< 10% of difference). Biomass-based model predictions differed the most from those estimated by the other two types. The differences in PP estimates were primarily attributed to the different ways these models treat the phytoplankton assemblage, along with the difference in input variables. Among the five models evaluated, the output from the modified version of the CbPM showed the lowest bias (0.55) being the most realistic. It made a special attempt to detect the factors controlling phytoplankton physiological state, showing a nutrient limitation towards the Drake area similar to the one observed for the in situ PP values. 相似文献
6.
《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(2):333-366
A new mixed layer multi-nutrient ecosystem model, incorporating diatoms, non-diatoms and zooplankton, is described that models the role of iron in marine biogeochemical cycles. The internal cell biochemistry of the phytoplankton is modelled using the mechanistic model of Flynn [2001. A mechanistic model for describing dynamic multi-nutrient, light, temperature interactions in phytoplankton. Journal of Plankton Research 23, 977–997] in which the internal cell concentrations of chlorophyll, nitrogen, silica, and iron are all dynamic variables that respond to external nutrient concentrations and light levels. Iron stress in phytoplankton feeds back into chlorophyll synthesis and changes in photosynthetic unit (PSU) size, thereby reducing their growth rate. Because diatom silicon metabolism is inextricably linked with cell division, diatom population density (cell m−3) is modelled as well as C biomass. An optimisation technique was used to fit the model to three time-series datasets at Biotrans (47°N, 20°W) and Kerfix (50°40′S, 68°25′E) and the observations for the Southern Ocean Iron-Release Experiment (SOIREE) iron-enrichment experiment (61°S, 140°E). The model gives realistic simulations of the annual cycles of nutrients, phytoplankton, and primary production at Biotrans and Kerfix and can also accurately simulate an iron fertilisation experiment. Specifically, the model predicts the high values of diatom Si:N and Si:C ratios observed in areas where iron is a limiting factor on algal growth. In addition, the model results at Kerfix confirm previous suggestions that underwater light levels have a more limiting effect on phytoplankton growth than iron supply. The model is also used to calculate C budgets and C and Si export from the mixed layer. The implications of these results for developing biogeochemical models incorporating the role of iron are discussed. 相似文献
7.
Estuaries exhibit a large range in their responses to nitrogen loadings determined in part by characteristics of the driver, such as magnitude and frequency, but also by such intrinsic characteristics as physical/chemical factors (e.g., depth, volume, hypsometry, salinity, turbidity) and biological factors (e.g., nature of ecological communities, trophic interactions). To address the richness of estuarine response to driver variables, the aim ultimately is to establish a simple estuarine classification scheme, beginning with a river-dominated subset of estuarine systems and focusing on the role of water residence time in the estuary. Residence time (or flushing time) is related to other drivers (streamflow, nutrient, and sediment loads) and drives much of the biological response of estuaries because of flushing effects on plankton, temperature, nutrients, and light. Toward this goal, nutrient–phytoplankton–zooplankton (NPZ) models have been used to examine a range of subjects including effects of nutrient limitation and zooplankton predation on phytoplankton dynamics and fish predation. This class of model can admit a wide range of behavior, including multiple steady-states and oscillatory behavior. The NPZ equations include terms for nutrient recycling, phytoplankton settling, benthic regeneration, and zooplankton mortality. Analysis of the equations suggests that both the nature of nitrogen loading (i.e., whether it is correlated with discharge or independent of it) and residence time are critical in determining the steady-state response of the system. 相似文献
8.
基于浮游植物吸收的海洋初级生产力模型的不确定性分析 总被引：1，自引：1，他引：0
Satellite-derived phytoplankton pigment absorption(a_(ph)) has been used as a key predictor of phytoplankton photosynthetic efficiency to estimate global ocean net primary production(NPP). In this study, an a_(ph)-based NPP model(Ab PM) with four input parameters including the photosynthetically available radiation(PAR), diffuse attenuation at 490 nm(K_d(490)), euphotic zone depth(Z_(eu)) and the phytoplankton pigment absorption coefficient(a_(ph)) is compared with the chlorophyll-based model and carbon-based model. It is found that the Ab PM has significant advantages on the ocean NPP estimation compared with the chlorophyll-based model and carbonbased model. For example, Ab PM greatly outperformed the other two models at most monitoring sites and had the best accuracy, including the smallest values of RMSD and bias for the NPP estimate, and the best correlation between the observations and the modeled NPPs. In order to ensure the robustness of the model, the uncertainty in NPP estimates of the Ab PM was assessed using a Monte Carlo simulation. At first, the frequency histograms of simple difference(δ), and logarithmic difference(δ~(LOG)) between model estimates and in situ data confirm that the two input parameters(Z_(eu) and PAR) approximate the Normal Distribution, and another two input parameters(a_(ph) and K_d(490)) approximate the logarithmic Normal Distribution. Second, the uncertainty in NPP estimates in the Ab PM was assessed by using the Monte Carlo simulation. Here both the PB(percentage bias), defined as the ratio of ΔNPP to the retrieved NPP, and the CV(coefficient of variation), defined as the ratio of the standard deviation to the mean are used to indicate the uncertainty in the NPP brought by input parameter to Ab PM model. The uncertainty related to magnitude is denoted by PB and the uncertainty related to scatter range is denoted by CV.Our investigations demonstrate that PB of NPP uncertainty brought by all parameters with an annual mean of5.5% covered a range of –5%–15% for the global ocean. The PB uncertainty of Ab PM model was mainly caused by a_(ph); the PB of NPP uncertainty brought by a_(ph) had an annual mean of 4.1% for the global ocean. The CV brought by all the parameters with an annual mean of 105% covered a range of 98%–134% for global ocean. For the coastal zone of Antarctica with higher productivity, the PB and CV of NPP uncertainty brought by all parameters had annual means of 7.1% and 121%, respectively, which are significantly larger than those obtained in the global ocean. This study suggests that the NPPs estimated by Ab PM model are more accurate than others, but the magnitude and scatter range of NPP errors brought by input parameter to Ab PM model could not be neglected,especially in the coastal area with high productivity. So the improving accuracy of satellite retrieval of input parameters should be necessary. The investigation also confirmed that the SST related correction is effective for improving the model accuracy in low temperature condition. 相似文献
9.
The distribution of phytoplankton and its correlation with environmental factors were studied monthly during August 2012 to July 2013 in the Yantian Bay. A total of 147 taxa of phytoplankton were identified, and the average abundance was in the range of 0.57×10~4 to 7.73×10~4 cell/L. A total of 19 species dominated the phytoplankton assemblages, and several species that are widely reported to be responsible for microalgae blooms were the absolutely dominant species, such as Skeletonema costatum, Navicula sp., Thalassionema nitzschioides,Pleurosigma sp., and Licmophora abbreviata. The monthly variabilities in phytoplankton abundance could be explained by water temperature, dissolved oxygen, salinity, dissolved inorganic nitrogen(DIN), and suspended solids. The results of a redundancy analysis showed that p H and nutrients, including DIN and silicate(SiO_4), were the most important environmental factors controlling phytoplankton assemblages in specific months. It was found that nutrients and pH levels that were mainly influenced by mariculture played a vital role in influencing the variation of phytoplankton assemblages in the Yantian Bay. Thus, a reduction of mariculture activities would be an effective way to control microalgae blooms in an enclosed and intensively eutrophic bay. 相似文献
10.
Goh Onitsuka Yutaka Yoshikawa Tomoyuki Shikata Kei Yufu Kazuo Abe Takahisa Tokunaga Katsunori Kimoto Takeshi Matsuno 《Journal of Oceanography》2018,74(4):351-365
The temporal evolution of a thin phytoplankton layer was observed by field measurements using a research vessel and mooring instruments in the Yatsushiro Sea, a semi-enclosed narrow embayment in Japan, in early August 2013. The subsurface chlorophyll maximum developed into a thin layer within 2 days just below the pycnocline at around 10-m depth, where turbulent mixing (the dissipation rate of turbulent kinetic energy) was weak (low). The layer persisted for 1.5 to 2 days and declined after irradiance drastically decreased at the sea surface. At the peak period, the layer thickness, which is defined as the full-width at half-maximum of the peak in chlorophyll a concentration, ranged from 0.6 to 1.4 m, and the maximum concentration reached 42.3 mg m?3. The horizontal extent of the layer was approximately 10 km along the longitudinal axis of the bay. The phytoplankton population characterized by the layer was dominated by a chain-forming centric diatom, Chaetoceros spp. The formation mechanisms of the thin diatom layer were investigated using the observed data and a vertical one-dimensional model that includes physical and biological processes. The results suggest that the development of the thin layer was caused by in situ growth and aggregation due to nutrient-dependent sinking of the species under weak turbulence. The study highlights that continuous multidisciplinary observations and understanding species-specific physiological responses to environmental variations are necessary to elucidate drastically fluctuating phytoplankton dynamics in a coastal water. 相似文献
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12.
Karine Granger Alain Mnesguen Sbastien Lefebvre Cdric Bacher Stphane Pouvreau 《Journal of Sea Research》2009,62(2-3):147
It is well known that temporal changes in bivalve body mass are strongly correlated with temporal variations in water temperature and food supply. In order to study the influence of the year-to-year variability of environmental factors on oyster growth, we coupled a biogeochemical sub-model, which simulates trophic resources of oysters (i.e. phytoplankton biomass via chlorophyll a), and an ecophysiological sub-model, which simulates growth and reproduction (i.e. gametogenesis and spawning), using mechanistic bases. The biogeochemical sub-model successfully simulated phytoplankton dynamics using river nutrient inputs and meteorological factors as forcing functions. Adequate simulation of oyster growth dynamics requires a relevant food quantifier compatible with outputs of the biogeochemical sub-model (i.e. chlorophyll a concentration). We decided to use the phytoplankton carbon concentration as quantifier for food, as it is a better estimator of the energy really available to oysters. The transformation of chlorophyll a concentration into carbon concentration using a variable chlorophyll a to carbon ratio enabled us to improve the simulation of oyster growth especially during the starvation period (i.e. autumn and winter). Once validated, the coupled model was a suitable tool to study the influence of the year-to-year variability of phytoplankton dynamics and water temperature on the gonado-somatic growth of the Pacific oyster. Four years with highly contrasted meteorological conditions (river inputs, water temperature and light) 2000, 2001, 2002 and 2003, were simulated. The years were split into two groups, wet years (2000 and 2001) and dry years (2002 and 2003). Significant variability of the response of oysters to environmental conditions was highlighted between the four scenarios. In the wet years, an increase in loadings of river nutrients and suspended particulate matter led to a shift in the initiation and the magnitude of the phytoplanktonic spring bloom, and consequently to a shift in oyster growth patterns. In contrast, in the dry years, an increase in water temperature—especially during summer—resulted in early spawning. Thus, the gonado-somatic growth pattern of oysters was shown to be sensitive to variations in river loadings and water temperature. In this context, the physiological status of oysters is discussed using a relevant indicator of energy needs. 相似文献
13.
Nutrient budgets averaged over tidal cycles off the Changjiang (Yangtze River) Estuary 总被引：1，自引：0，他引：1
During the spring tide period in November 2005, continuous observations were conducted over 25 h (approximately two M2 tidal cycles) at 12 stations within the Changjiang (Yangtze River) Estuary; and among them nine stations formed a closed rectangle. The observation items included current, salinity, suspended particulate matter (SPM), and nutrients. By establishing a simplified model, physical and chemical hydrography data were used to calculate the net and tidal-averaged budgets of seawater, salt, SPM, and nutrients in this rectangle. The results showed that the inflows and outflows of conservative seawater and salt, as well as SPM, matched well with deficits less than 10%; whereas the outputs of the five nutrient species were only 52%–86% of the respective inputs, suggesting the study area acted as a nutrient sink. Processes that might contribute to the nutrient budgets in the study area were discussed, including phytoplankton uptakes, exchanges at sediment-water interface, atmospheric depositions, nitrogen fixation, and denitrification. 相似文献
14.
A. V. Drits A. B. Nikishina T. N. Semenova V. M. Sergeeva K. A. Solovyev M. V. Flint 《Oceanology》2016,56(3):382-394
The distribution and feeding of dominant mesozooplankton species were studied in the estuary of the Ob River and adjacent inner Kara Sea shelf waters in September 2013. It was shown that the spatial distributions of Cyclops sp., Senecella siberica, Limnocalanus macrurus, Mysis oculata, Drepanopus bungei, Jashnovia tolli and Pseudocalanus sp. are related to the specific characteristics of the hydrographic regime in the estuarine frontal zone. The distributions of Cyclops sp., Senecella siberica, and Pseudocalanus sp. are mainly limited by salinity, while other species inhabit an area with a wide range of salinity values without clear preferences. Peaks of their abundance could be either consolidated or distanced in space. The populations of Jashnovia tolli, Drepanopus bungei, and Pseudocalanus sp. permanently inhabit the layer under the pycnohalocline; the populations of Cyclops sp. and Mysis oculata inhabit the upper mixed layer. Limnocalanus macrurus demonstrates a different vertical distribution pattern: the copepod undertakes diel vertical migrations in the southern part of the estuarine frontal zone; in its northern part, the population is concentrated below the pycnocline during day and night. The differences in the distributions of the studied species determine their feeding behavior and their role in phytoplankton grazing. The most intense utilization of biomass and production of autotrophic phytoplankton by zooplankton occur in the freshened water zone and the adjacent southern periphery of the estuarine frontal zone: the total daily phytoplankton consumption makes up 10–18% of the biomass and 60–380% of primary production. Daily zooplankton consumption of phytoplankton in the estuarine frontal zone decreases to 2–7% of the biomass and to 14% of primary production; in inner shelf waters, the values do not exceed 1% for both phytoplankton biomass and production. 相似文献
15.
An ecosystem model was used to (1) determine the extent to which global trends in the ratio of mesozooplankton production to primary production (referred to herein as the “z-ratio”) can be explained by nutrient enrichment, temperature, and euphotic zone depth, and (2) quantitatively diagnose the mechanisms driving these trends. Equilibrium model solutions were calibrated to observed and empirically derived patterns in phytoplankton biomass and growth rates, mesozooplankton biomass and growth rates, and the fraction of phytoplankton that are large (>5 μm ESD). This constrained several otherwise highly uncertain model parameters. Most notably, half-saturation constants for zooplankton feeding were constrained by the biomass and growth rates of their prey populations, and low zooplankton basal metabolic rates were required to match observations from oligotrophic ecosystems. Calibrated model solutions had no major biases and produced median z-ratios and ranges consistent with estimates. However, much of the variability around the median values in the calibration dataset (72 points) could not be explained. Model results were then compared with an extended global compilation of z-ratio estimates (>10 000 points). This revealed a modest yet significant (r=0.40) increasing trend in z-ratios from values ～0.01–0.04 to ～0.1–0.2 with increasing primary productivity, with the transition from low to high z-ratios occurring at lower primary productivity in cold-water ecosystems. Two mechanisms, both linked to increasing phytoplankton biomass, were responsible: (1) zooplankton gross growth efficiencies increased as their ingestion rates became much greater than basal metabolic rates and (2) the trophic distance between primary producers and mesozooplankton shortened as primary production shifted toward large phytoplankton. Mechanism (1) was most important during the transition from low to moderate productivity ecosystems and mechanism (2) was responsible for a relatively abrupt transition to values >0.1 in high productivity ecosystems. Substantial z-ratio variations overlying these mean trends remained unexplained by these mechanisms. Potential sources of this variability include zooplankton patchiness, unresolved effects of advection and unsteady dynamics, unresolved shifts in mesozooplankton sizes and species, and unresolved aspects of zooplankton bioenergetics. Comparison of the modeled z-ratio patterns and mechanisms diagnosed herein with those obtained using models with expanded biological dynamics embedded in global circulation models will help further elucidate the causes of this variation. 相似文献
16.
《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(1):95-123
Observations have shown that aggregates (“marine snow”) are an important fraction of the organic matter vertical flux in the ocean. There has been a separation in biological models describing this flux, with coagulation models focused on phytoplankton blooms for which particle concentrations are high and grazing is low and neglectable and with plankton models focused on food web interactions neglecting coagulation dynamics. This separation has partly resulted from the difficulty in describing the interactions among the multiple particle sources using a coagulation model for a food web. New approaches for describing particle dynamics now make it possible to do so. The present study examines the effect of combining the food web model of Fasham et al. (1990. Journal of Marine Research 34, 591–639) with a coagulation dynamics model and applying the combined model to describe the annual cycle of an oligotrophic plankton system. As part of the model formulation, the coagulation kernels had to be altered to include both the case of fractal particles interacting and the case of smaller particles being faster settling. Results show that coagulation can have an important effect on particle flux even in the low particle concentration oligotrophic environment by increasing average particle settling speed and by increasing the ratio of maximum to minimum daily vertical flux over the course of a yearly cycle. As part of this, coagulation forms large, rapidly sinking particles. Grazing and the accompanying formation of fecal pellets can compete with coagulation for particles, but the fecal pellets can also participate in the formation of large aggregates. Among the variables that can influence export rates are phytoplankton size and concentration as well as depth of the surface mixed layer. The results provide evidence for the importance of coagulation processes in enhancing particle export even in central ocean regions. 相似文献
17.
Atsushi Matsuoka Pierre Larouche Michel Poulin Warwick Vincent Hiroshi Hattori 《Estuarine, Coastal and Shelf Science》2009
The chlorophyll a specific absorption coefficient of phytoplankton, aφ∗(λ) is an important parameter to determine for primary production models and for the estimation of phytoplankton physiological condition. Knowledge of this parameter at high latitudes where nutrient rich cold water submitted to low incident light is a common environment is almost nonexistent. To address this issue, we investigated the light absorption properties of phytoplankton as a function of irradiance, temperature, and nutrients using a large data set in the southern Beaufort Sea during the open water to ice cover transition period. The aφ∗(λ) tended to increase from autumn when open water still existed to early winter when sea ice cover was formed, resulting from a biological selection of smaller-size phytoplankton more efficient to absorb light. There was no significant correlation between aφ∗(λ) and irradiance or temperature for both seasons. However, aφ∗(λ) showed a significant positive correlation with NO3 + NO2. Implications of the results for phytoplankton community adaptation to changing light levels are discussed. 相似文献
18.
Rivers transport nutrients and suspended sediment matter (SSM) as well as fresh water from land to coastal regions, where the biological productivity is high. In the coastal area, the buoyancy of fresh water leads to the formation of horizontal anticyclonic gyres and vertical circulations, which affect the variation of biological production such as plankton blooms. However, the primary production caused by the 3-D dynamics have not been quantitatively discussed, and observations can hardly capture the daily temporal variations of phytoplankton blooms. We developed an ocean general circulation model including a simple ecosystem model, to investigate the 3-D and temporal changes in phytoplankton blooms caused by riverine input such as flooding. The distribution patterns of nutrients and phytoplankton differ significantly from that of fresh water. The phytoplankton maxima shift from the downstream (right-hand side of the river mouth) to the upstream regions (left-hand side of the river mouth). The shift that occurs is categorized by the different nitrate origins: (1) river-originated nitrate is dominant in the downstream region; (2) subsurface-originated nitrate is dominant in the upstream region, and is transported by upwelling associated with vertical circulation and horizontal anticyclonic gyre; and (3) regenerated nitrate is dominant in the upstream region. The total primary production in phytoplankton blooms is maintained not only by river-originated nitrate but also by subsurface-originated nitrate that is 1.5 times larger than the river-originated. Several case studies (e.g., including SSM) were conducted in this study. 相似文献
19.
《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(11-12):2877-2908
The recent NE subarctic Pacific study of the Canadian JGOFS project was designed primarily to address why phytoplankton biomass and production at Ocean Station Papa (OSP: 50°N, 145°W) are not as high as the nitrate concentrations could potentially support. To examine the possible role of iron (Fe) limitation in concert with microzooplankton grazing and physical supply of nitrate, we have coupled a four-compartment Nitrogen–Phytoplankton–Zooplankton–Detritus planktonic ecosystem model with a 60-layer (each 2 m thick) one-dimensional mixed-layer model (Mellor–Yamada level 2.5), driven by annual forcing characteristic of OSP. Both the physical and ecological models are forced with the same annual heat budget, mean phytoplankton concentration was tuned with the equilibrium solution of the model, and the zooplankton parameter values were chosen to be representative of microzooplankton. Modelled sea surface temperature ranged between 6 (fixed – late winter) and 13–14°C, depending on the distribution and amount of phytoplankton and detritus calculated by the model. Simulations with Fe limitation reducing the maximum specific growth rate of phytoplankton (for Fe-replete conditions) by a factor of ∼3 best reproduced the annual cycle of surface layer nitrate, although the resulting annual f-ratio calculated from the fluxes into and out of the nitrogen compartment was marginally higher than recent estimates of f-ratio based on observations at OSP. The best simulations with Fe limitation agreed with observations of the annual cycle of surface nitrate concentration, the f-ratio, particulate nitrogen concentration in the euphotic layer, the export production, and the remineralization depth scale for sinking detritus, to within ∼50%, probably within the range of observational uncertainty and/or seasonal and interannual variability. Possible modifications include separating the detrital pool into suspended and sinking organic matter, decreasing the rate of remineralization with increasing depth, and examining the supply of nitrate to the surface layer by means of horizontal advection. The observational basis required to formulate these processes is marginal at present. 相似文献
20.
V. M. Sergeeva L. S. Zhitina S. A. Mosharov A. A. Nedospasov A. A. Polukhin 《Oceanology》2018,58(5):700-709
Phytoplankton community and its distribution were investigated in the south part of the Polar Front in the eastern Barents Sea in October 2014. Analysis of the spatial differences in the phytoplankton structure was performed in connection with changes of the temperature, salinity and biogenic regime. At the end of the growing season in the phytoplankton community was dominated by destruction processes and the concentration of nutrients in the upper mixed layer was higher than the limiting level. Coccolithophores (Emiliania huxleyi and Discosphaera cf. tubifer) dominanted over investigated area. The maximum values of abundance and biomass of coccolithophores reached 90.4 mln.cell/m3 and 30.8 mgC/m3, drawing up 82% of the total number and 93% of the total biomass of phytoplankton. Influence of transformed the waters of Atlantic origin was observed in the western part of the investigated area. The number of species in the phytoplankton community here was 1.5–2 times lower than in the eastern part of the occupied mostly by Barents Sea water. In the eastern part of the presence of large dinoflagellates Neoceratium spp. (Ceratium spp.) and Dinophysis spp., lower values of chlorophyll a concentration, a higher proportion of pheophytin in the amount of pigment chlorophyll + pheophytin, the high content of ammonia in the upper mixed layer showed that in this area the phytoplankton was at a later seasonal succession stage than the western part. 相似文献