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1.
The northward migration of spring bloom was observed in the Sea of Japan from April to May 1997 by the Ocean Color and Temperature
Scanner (OCTS) on board the Advanced Earth Observing Satellite (ADEOS). This phenomenon is well simulated with a numerical
ecosystem model coupled with a hydrodynamic model. The hydrodynamic model is the Geophysical Fluid Dynamics Laboratory (GFDL)
Modular Ocean Model (MOM). The ecosystem model consists of five components: dissolved inorganic nitrogen (DIN), dissolved
inorganic phosphorus (DIP), phytoplankton, zooplankton and detritus. Results of the numerical ecosystem model suggest that
the mesoscale development of the spring bloom in the Sea of Japan is related to that of sea water temperature, and that the
bloom is limited by the depletion of DIN.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Boris Cisewski Volker H. Strass Monika Rhein Sören Krägefsky 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):78-94
Ten-month time series of mean volume backscattering strength (MVBS) and vertical velocity obtained from three moored acoustic Doppler current profilers (ADCPs) deployed from February until December 2005 at 64°S, 66.5°S and 69°S along the Greenwich Meridian were used to analyse the diel vertical zooplankton migration (DVM) and its seasonality and regional variability in the Lazarev Sea. The estimated MVBS exhibited distinct patterns of DVM at all three mooring sites. Between February and October, the timing of the DVM and the residence time of zooplankton at depth were clearly governed by the day–night rhythm. Mean daily cycles of the ADCP-derived vertical velocity were calculated for successive months and showed maximum ascent and descent velocities of 16 and –15 mm s?1. However, a change of the MVBS pattern occurred in late spring/early austral summer (October/November), when the zooplankton communities ceased their synchronous vertical migration at all three mooring sites. Elevated MVBS values were then concentrated in the uppermost layers (<50 m) at 66.5°S. This period coincided with the decay of sea ice coverage at 64°S and 66.5°S between early November and mid-December. Elevated chlorophyll concentrations, which were measured at the end of the deployment, extended from 67°S to 65°S and indicated a phytoplankton bloom in the upper 50 m. Thus, we propose that the increased food supply associated with an ice edge bloom caused the zooplankton communities to cease their DVM in favour of feeding. 相似文献
3.
Differences in ecosystem dynamics between the northern and southern parts of the Japan Sea have been investigated with two nitrogen based ecosystem models forced by climatological mixed layer depth and euphotic layer depth. Models having 4 and 9 compartments with the same biochemical parameters were applied to the northern and southern parts. The spring bloom in the southern part is earlier and smaller than that in the northern part according to both models, which is supported by satellite ocean color images. The difference of the timing is related to the variation of mixed layer depth, and the magnitude of blooming is also related to the concentrations of surface nutrient and herbivorous zooplankton in early spring. The simulated seasonal variations of ecosystem characteristics (standing stock of each compartment, primary production and the ratio of export flux of organic particles to the primary production) are not significantly different between two models. The ratio of export flux of organic particles to the primary production are about 36% and 23% in the northern and southern parts according to the 4-compartment model, while the values are 31% and 18% by 9-compartment model. These results suggest that the biological pump in the northern part is more active than that in the southern part of the Japan Sea. Sensitivity analyses have been carried out to examine the differences of the response to the models. 相似文献
4.
Michio Kawamiya Michio J. Kishi Yasuhiro Yamanaka Nobuo Suginohara 《Journal of Oceanography》1995,51(6):635-664
A vertical one-dimensional ecosystem model was constructed and applied to Station Papa. The model has seven compartments (phytoplankton, nitrate, ammonium, zooplankton, particulate organic matters, dissolved organic matters, dissolved oxygen) and was coupled with a mixed layer model for calculating diffusion coefficient which appears in the governing equations. The mixed layer model was driven by SST, SSS data observed at Station Papa in 1980 and ECMWF wind data for 1980, and the ecosystem model was driven by fixing nitrate concentration in deep layer to an observational value. The phytoplankton maximum in March was reproduced by the model although the maximum in fall-winter could not be reproduced. The model also suggests the importance of studying nitrification. As a whole, the model could reproduce characteristic features at Station Papa such as the summer ammonium maximum at 50 m depth, the summer dissolved oxygen maximum at 70 m depth and the absence of remarkable phytoplankton bloom. 相似文献
5.
George L. Hunt Jr. Phyllis Stabeno Gary Walters Elizabeth Sinclair Richard D. Brodeur Jeffery M. Napp Nicholas A. Bond 《Deep Sea Research Part II: Topical Studies in Oceanography》2002,49(26)
We propose a new hypothesis, the Oscillating Control Hypothesis (OCH), which predicts that pelagic ecosystem function in the southeastern Bering Sea will alternate between primarily bottom-up control in cold regimes and primarily top-down control in warm regimes. The timing of spring primary production is determined predominately by the timing of ice retreat. Late ice retreat (late March or later) leads to an early, ice-associated bloom in cold water (e.g., 1995, 1997, 1999), whereas no ice, or early ice retreat before mid-March, leads to an open-water bloom in May or June in warm water (e.g., 1996, 1998, 2000). Zooplankton populations are not closely coupled to the spring bloom, but are sensitive to water temperature. In years when the spring bloom occurs in cold water, low temperatures limit the production of zooplankton, the survival of larval/juvenile fish, and their recruitment into the populations of species of large piscivorous fish, such as walleye pollock (Theragra chalcogramma), Pacific cod (Gadus macrocephalus) and arrowtooth flounder (Atheresthes stomias). When continued over decadal scales, this will lead to bottom-up limitation and a decreased biomass of piscivorous fish. Alternatively, in periods when the bloom occurs in warm water, zooplankton populations should grow rapidly, providing plentiful prey for larval and juvenile fish. Abundant zooplankton will support strong recruitment of fish and will lead to abundant predatory fish that control forage fish, including, in the case of pollock, their own juveniles. Piscivorous marine birds and pinnipeds may achieve higher production of young and survival in cold regimes, when there is less competition from large piscivorous fish for cold-water forage fish such as capelin (Mallotus villosus). Piscivorous seabirds and pinnipeds also may be expected to have high productivity in periods of transition from cold regimes to warm regimes, when young of large predatory species of fish are numerous enough to provide forage. The OCH predicts that the ability of large predatory fish populations to sustain fishing pressure will vary between warm and cold regimes.The OCH points to the importance of the timing of ice retreat and water temperatures during the spring bloom for the productivity of zooplankton, and the degree and direction of coupling between zooplankton and forage fish. Forage fish (e.g., juvenile pollock, capelin, Pacific herring [Clupea pallasii]) are key prey for adult pollock and other apex predators. In the southeastern Bering Sea, important changes in the biota since the mid-1970s include a marked increase in the biomass of large piscivorous fish and a concurrent decline in the biomass of forage fish, including age-1 walleye pollock, particularly over the southern portion of the shelf. Populations of northern fur seals (Callorhinus ursinus) and seabirds such as kittiwakes (Rissa spp.) at the Pribilof Islands have declined, most probably in response to a diminished prey base. The available evidence suggests that these changes are unlikely the result of a decrease in total annual new primary production, though the possibility of reduced post-bloom production during summer remains. An ecosystem approach to management of the Bering Sea and its fisheries is of great importance if all of the ecosystem components valued by society are to thrive. Cognizance of how climate regimes may alter relationships within this ecosystem will facilitate reaching that goal. 相似文献
6.
A vertically resolved ecosystem model is developed to simulate the dynamics of the pelagic food web in St Helena Bay during a representative period of relaxation after an upwelling event. The proposed model aims at coupling three biogeochemical cycles (carbon, nitrogen and silicon), using several recently developed concepts of the stoichiometric approach. A consequence of this approach is that important qualitative aspects are introduced, such as indicators of phytoplankton physiological state or variable food C:N ratios. For instance, the sedimentation and exudation rates for phytoplankton vary according to physiological state. An attempt is made to parameterize and simulate the diel cycles for vertical migration and feeding rhythms of large zooplankton, two important mesoscale processes that are thought to influence the overall dynamics of the huge phytoplankton blooms in the region.Observations of the Anchor Station Experiment 1987 (ASE’87) are used to assess the quality of the model. There is overall agreement between observations and the corresponding simulated results. The timing, the magnitude, and the vertical structure of the phytoplankton bloom are well reproduced. The balances for carbon and nitrogen flows and stocks compare well to the numerous estimates found from the literature for the southern Benguela region.On the basis of the model results, the origin of the new nutrients, the fate of the carbon fixed by phytoplankton, and the importance of the microheterotrophic pathways are discussed. It is concluded that sediments of the St Helena Bay and surrounding areas may play a crucial role in increasing the level of phytoplankton production. The results also suggest that exudation is the main process by which the carbon fixed by phytoplankton would have been lost, and that microheterotrophic pathways would have been intense during the experiment. 相似文献
7.
A three-dimensional ecosystem model for the North Sea which includes competition between Pseudocalanus elongatus and the rest of the zooplankton biomass was applied to describe the seasonal cycle of zooplankton in 2003–2004. The paper presents the comparison of simulated stage-resolved abundances with copepod counts at several stations in the German Bight during the GLOBEC-Germany project from February to October 2004. A validation of influential state variables gives confidence that the model is able to calculate reliably the stage development and abundances of P. elongatus as well as the range of bulk zooplankton biomass, and thus the ratio of population biomass to total biomass. In the German Bight, the population is below 20% in spring. The ratio increases up to 50% during summer. The number of generations was estimated from peaks in egg abundance to about 4–8 generations of P. elongatus in the southern North Sea. A mean of four generations per year were estimated in the central North Sea, six to eight generations northwest of the Dogger Bank (tails end) and five generations in the German Bight. 相似文献
8.
V. Rousseau S. Becquevort J. -Y. Parent S. Gasparini M. -H. Daro M. Tackx C. Lancelot 《Journal of Sea Research》2000,43(3-4)
The trophic efficiency of the planktonic food web in the Phaeocystis-dominated ecosystem of the Belgian coastal waters was inferred from the analysis of the carbon flow network of the planktonic system subdivided into its different trophodynamic groups. A carbon budget was constructed on the basis of process-level field experiments conducted during the spring bloom period of 1998. Biomass and major metabolic activities of auto- and heterotrophic planktonic communities (primary production, bacterial production, nanoproto-, micro- and mesozooplankton feeding activities) were determined in nine field assemblages collected during spring at reference station 330. In 1998, the phytoplankton spring flowering was characterised by a moderate diatom bloom followed by a massive Phaeocystis colony bloom. Phaeocystis colonies, contributing 70% to the net primary production, escaped the linear food chain while the early spring diatom production supplied 74% of the mesozooplankton carbon uptake. The rest of mesozooplankton food requirement was, at the time of the Phaeocystis colony bloom, partially fulfilled by microzooplankton. Only one-third of the microzooplankton production, however, was controlled by mesozooplankton grazing pressure. Ungrazed Phaeocystis colonies were stimulating the establishment of a very active microbial network. On the one hand, the release of free-living cells from ungrazed colonies has been shown to stimulate the growth of microzooplankton, which was controlling 97% of the nanophytoplankton production. On the other hand, the disruption of ungrazed Phaeocystis colonies supplied the water column with large amounts of dissolved organic matter available for planktonic bacteria. The budget calculation suggests that ungrazed colonies contributed up to 60% to the bacterial carbon demand, while alternative sources (exudation, zooplankton egestion and lysis of other organisms) provided some 30% of bacterial carbon requirements. This suggests that the spring carbon demand of planktonic bacteria was satisfied largely by autogenic production. The trophic efficiency was defined as the ratio between mesozooplankton grazing on a given source and food production. In spite of its major contribution to mesozooplankton feeding, the trophic efficiency of the linear food chain, restricted to the grazing on diatoms, represented only 5.6% of the available net primary production. The trophic efficiency of the microbial food chain, the ratio between mesozooplankton grazing on microzooplankton and the resource inflow (the bacterial carbon demand plus the nanophytoplankton production) amounted to only 1.6%. These low trophic efficiencies together with the potential contribution of ungrazed Phaeocystis-derived production to the bacterial carbon demand suggest that during spring 1998 most of the Phaeocystis-derived production in the Belgian coastal area was remineralised in the water column. 相似文献
9.
Spatio‐temporal variability of zooplankton biomass and environmental control in the Northern Benguela Upwelling System: field investigations and model simulation 
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下载免费PDF全文 Bettina Martin Anja Eggert Rolf Koppelmann Rabea Diekmann Volker Mohrholz Martin Schmidt 《Marine Ecology》2015,36(3):637-658
Spatial and temporal distribution patterns of zooplankton are highly variable in the Northern Benguela Upwelling System. We studied the distribution of zooplankton (size class ≥ 0.33 mm) and used field data from four cruises that took place between March 2008 and February 2011, as well as simulation results of a regional ecosystem model. Remotely sensed sea surface temperatures (SST) and surface chlorophyll concentrations were analysed to investigate environmental influences on zooplankton biomass. The Intense Benguela Upwelling Index showed a distinct seasonal signal throughout the years and the highest upwelling peaks in August/September. Even though surface chlorophyll concentrations were very variable throughout the year, the highest concentrations were always detected in September, following the upwelling of nutrient‐rich water. In field catches, zooplankton biomass concentration in the upper 200 m was highest above the outer shelf and shelf‐break in December 2010 and February 2011, i.e. 6 months after the upwelling peaks. In contrast, zooplankton biomass simulated by the model in the surface water was highest in September. In March/April, biomass maxima were typically measured in the field at intermediate water depths, but the vertical distribution was also affected by extensive oxygen minimum zones. The ecosystem model reproduced this vertical pattern. Although general trends were similar, simulation data of zooplankton standing stocks overestimated the field data by a factor of 3. In upwelling systems, food webs are generally considered to be short and dominated by large cells. However, our field data indicate more small‐sized zooplankton organisms above the shelf than offshore. 相似文献
10.
《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(4):608-636
Temporal variability of acoustically estimated zooplankton biomass at the Bermuda Testbed Mooring (BTM) site in the Sargasso Sea (at 31°43′N, 64°10′W) is described for time scales from less than an hour to the seasonal cycle primarily using data obtained between August 1996 and November 2000, and from May 10 to November 13, 2003. Concurrent high frequency BTM observations of meteorological, physical, and bio-optical variables are used to interpret processes contributing to the zooplankton variability. Zooplankton biomass estimates are derived from regressions of backscatter intensity data measured with an upward looking 153-kHz acoustic Doppler current profiler (ADCP) and zooplankton net tow data collected near the BTM site as part of the Bermuda Atlantic Time-series Study (BATS). Our data show clear event-scale variations. Peaks are associated with annual spring blooms involving mixed layer shoaling and in some cases passages of mesoscale eddy features. Biomass peaks are often coincident with maxima seen in BTM chlorophyll fluorescence measurements (inferred phytoplankton biomass). Some storm events do not appear to manifest in significant perturbations of zooplankton distributions; however, Hurricane Fabian (2003) greatly impacted these distributions. Estimates of zooplankton biomass and relative vertical velocity show the vertical structure of daily migration patterns. Seasonal variations in migration patterns are also evident, with diel changes in zooplankton biomass most pronounced in spring and least pronounced in winter. In summary, our high temporal resolution time series of estimated zooplankton biomass in the open ocean provide information on scales inaccessible through conventional monthly ship-based sampling. These data have implications for upper ocean ecology and the vertical transport of carbon and nitrogen through the diel migration of zooplankton. 相似文献
11.
We review the spatial and temporal patterns of zooplankton in the eastern tropical Pacific Ocean and relationships with oceanographic factors that affect zooplankton distribution, abundance and trophic relationships. Large-scale spatial patterns of some zooplankton groups show broad coincidence with surface water masses, circulation, and upwelling regions, in agreement with an ecological and dynamic partitioning of the pelagic ecosystem. The papers reviewed and a new compilation of zooplankton volume data at large-scale show that abundance patterns of zooplankton biomass have their highest values in the upwelling regions, including the Gulf of Tehuantepec, the Costa Rica Dome, the equatorial cold tongue, and the coast of Peru.Some of the first studies of zooplankton vertical distribution were done in this region, and a general review of the topic is presented. The possible physiological implications of vertical migration in zooplankton and the main hypotheses are described, with remarks on the importance of the oxygen minimum zone (OMZ) as a barrier to both the vertical distribution and migration of zooplankton in the region. Recent results, using multiple-net gear, show that vertical distribution is more complex than previously thought. There are some well-adapted species that do live and migrate within the OMZ.Temporal patterns are reviewed and summarized with historical data. Seasonal variations in zooplankton biomass follow productivity cycles in upwelling areas. No zooplankton time series exist to resolve ENSO effects in oceanic regions, but some El Niño events have had effects in the Peru Current ecosystem. Multidecadal periods of up to 50 years show a shift from a warm sardine regime with a low zooplankton biomass to a cool anchovy regime in the eastern Pacific with higher zooplankton biomasses. However, zooplankton volume off Peru has remained at low values since the 1972 El Niño, a trend opposite to that of anchoveta biomass since 1984.Studies of trophic relations emphasize the difference in the productivity cycle in the eastern tropical Pacific compared to temperate or polar ecosystems, with no particular peaks in the stocks of either zooplankton or phytoplankton. Productivity is more dependent on local events like coastal upwelling or water circulation, especially in the equatorial countercurrent and around the equatorial cool-tongue. Micrograzers are very important in the tropics as are predatory mesozooplankton. Up to 70% of the daily primary productivity is consumed by microzooplankton, which thus regulates the phytoplankton stocks. Micrograzers are an important link between primary producers, including bacteria, and mesozooplankton, constituting up to 80% of mesozooplankton food. Oceanography affects zooplankton trophic relationships through spatial–temporal effects on primary productivity and on the distributions of metabolic factors, food organisms, and predators. This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific. 相似文献
12.
Anukul Buranapratheprat Tetsuo Yanagi K. Olaf Niemann Satsuki Matsumura Pramot Sojisuporn 《Journal of Oceanography》2008,64(5):639-656
Although plankton bloom incidents in the upper Gulf of Thailand (UGoT) have been reported, no dynamic investigation of the
phenomenon has been conducted. To address this need, a simple pelagic ecosystem model coupled with the Princeton Ocean Model
(POM) was employed to investigate seasonal variations in surface chlorophyll-a (chl-a) distributions to clarify phytoplankton
dynamics in this area. The results revealed patterns of seasonal chl-a distribution that correspond to local wind, water movement
and river discharge. High chl-a patchiness was found to be concentrated near the western coast following westward circulation
near the northern coast developed during the northeast monsoon. During the southwest monsoon high concentrations were observed
around the northeastern coast due to eastward flow. The simulated results could explain the seasonal shifting of phytoplankton
blooms, which typically arise along the western and eastern coasts during the northeast and the southwest monsoons, respectively.
Sensitivity analyses of simulated chl-a distributions demonstrate that water stability, including wind-induced vertical currents
and mixing, plays significant roles in controlling phytoplankton growth. Nutrients in the water column will not stimulate
strong plankton blooms unless upwelling develops or vertical diffusivity is low. This finding suggests an alternative aspect
of the mechanism of phytoplankton bloom in this region. 相似文献
13.
利用在本系列研究第一部分中所建立的耦合的生物物理模型,模拟了渤海浮游植物生物量和营养盐含量的年度循环特征.模拟结果显示:藻类的春季水华是由经过一冬积累在水体中的营养盐导致,而水华开始的时间在浅水区明显早于深水区,对此深水区水体层化结构的形成可能起着重要作用;另一方面,河载营养盐与悬起的沉积物所释放的营养盐是诱发夏季水华的共同原因.基于模型结果,我们还发现:渤海的浮游植物动力特性就整体而言依然受无机氮限制,但是在莱州湾,磷限制特性表现得非常明显,这主要是由于每年黄河都要携带大量的无机氮进入海水,从而导致莱州湾营养盐的氮磷比已远远超过16. 相似文献
14.
1 IntroductionNitrogen and phosphorus together constitute thematerial basis used by phytoplankton for photosyn-thesis; however, if the ratio of nitrogen atomic massto phosphorus atomic mass in an aquatic environmentmarkedly deviates, whether above or bell… 相似文献
15.
基于2020年8月至11月在南海北部获取的声学多普勒流速剖面仪观测数据,利用后向散射强度数据估算得到相对体积散射强度并用其表征浮游动物生物量的相对大小,对相对体积散射强度的半月变化与具有半月周期的潮流动能进行相关性分析,进而分析天文大潮对声学估算的浮游动物生物量的影响。结果表明：半月周期的相对体积散射强度与潮流动能之间呈负相关关系,即天文大潮时,潮流动能较强,水体相对体积散射强度较低,浮游动物生物量则较小,天文小潮时则情况相反。初步推测其原因为：天文大潮时,强潮流一方面导致浮游动物生存环境恶化,使其生物量下降,另一方面也改变了浮游动物垂直迁移特性,浮游动物迁移到近海底处使其难以被观测。 相似文献
16.
The Influence of Physical Factors on the Variation of Phytoplankton and Nutrients in the Bohai Sea 总被引：3，自引：0，他引：3
The cycle of the phytoplankton in a coastal water is controlled by the biological processes, solar radiation, water temperature and physical transport processes. A three-dimensional ecosystem dynamic model is adopted in this study to investigate the influence of different physical factors on the variation of phytoplankton and nutrients in the Bohai Sea. The simulation is carried out for the year 1982. The simulated annual cycle of the primary production and nutrients are in reasonable agreement with the observations in the pattern. Vertical mixing can both affect the vertical transportation of nutrients and horizontal distribution of primary production. In winter the vertical distribution of nutrients is homogeneous because of the intensive mixing, while in summer there is a high value of nutrients in the depth about 15 m due to the stratification. The high primary production plague and the weak mixing center is positional correspondence. The production of phytoplankton is sensitive to the photosynthetically active radiation, which is strongly influenced by the transparency. The increase of the transparency can promote the production in spring and autumn significantly, but has little effect on the production in summer. The change of the transparency can both affect the occurrence time and the amplitude of the phytoplankton bloom dramatically. Horizontal advection does not affect the variation trend of the annual cycle of chlorophyll-a, but does affect the relative magnitude of the phytoplankton bloom, especially in summer. Horizontal advection can dramatically alter the horizontal distribution of chlorophyll-a. The maximum concentration of chlorophyll-a without horizontal advection in summer is twice as high than that with advection and the high chlorophyll-a areas locate along the coast. The river discharge only has regional influence on the ecosystem. The Huanghe River with high nitrate concentration influ-ences the annual cycle of nitrogen of the Laizhou Bay significantly. 相似文献
17.
Fredrika Norrbin Hans Chr. Eilertsen Maria Degerlund 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1945
During a circumnavigation of the Svalbard archipelago in May 2006, simultaneous marine environmental (meteorology, heat flux, ocean turbulence, irradiance) and biological (phytoplankton and zooplankton biomass/species) data were sampled at selected stations. The zooplankton data were supplemented by high-resolution, high-speed VPR sampling down to 100 m depth at most stations. We were able to sample different phases of the phytoplankton spring bloom in Arctic as well as in Atlantic waters, and the stations represented different situations with respect to irradiance, turbulence and water-column stability. Phytoplankton growth and depth distribution were physically controlled, while zooplankton distributions were affected by biological parameters and turbulence. Development of the zooplankton followed the phytoplankton bloom phase, which was progressing in a direction from west to east in the waters north of Svalbard, and southwards in the Barents Sea. Our results also showed that the zooplankton did not avoid Phaeocystis pouchetii colonies, which have earlier been described as toxic. Despite an early retreat of the ice this year there was no apparent mismatch between the phytoplankton bloom and the dominant mesozooplankton, Calanus spp. 相似文献
18.
Eleanor Frajka-Williams Peter B. Rhines Charles C. Eriksen 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2144-2161
We investigated the 2005 spring phytoplankton bloom in the Labrador Sea using Seaglider, an autonomous underwater vehicle equipped with hydrographic, bio-optical and oxygen sensors. The Labrador Sea blooms in distinct phases, two of which were observed by Seaglider: the north bloom and the central Labrador Sea bloom. The dominant north bloom and subsequent zooplankton growth are enabled by the advection of low-salinity water from West Greenland in the strong and eddy-rich separation of the boundary current. The glider observed high fluorescence and oxygen supersaturation within haline-stratified eddy-like features; higher fluorescence was observed at the edges than centers of the eddies. In the central Labrador Sea, the bloom occurred in thermally stratified water. Two regions with elevated subsurface chlorophyll were also observed: a 5 m thin-layer in the southwest Labrador Current, and in the Labrador shelf-break front. The thin layer observations were consistent with vertical shearing of an initially thicker chlorophyll patch. Observations at the front showed high fluorescence down to 100 m depth and aligned with the isopycnals defining the front. The high-resolution Seaglider sampling across the entire Labrador Sea provides first estimates of the scale dependence of coincident biological and physical variables. 相似文献
19.
A one-dimensional coupled physical-biogeochemical model has been developed to simulate the ecosystem of the central Black Sea at the end of the 1980s when eutrophication and invasion by gelatinous organisms seriously affected the stability and dynamics of the system. The physical model is the General Ocean Turbulence Model (GOTM) and the biogeochemical model describes the foodweb from bacteria to gelatinous carnivores through 24 state variables including three groups of phytoplankton: diatoms, small phototrophic flagellates and dinoflagellates, two zooplankton groups: micro- and mesozooplankton, two groups of gelatinous zooplankton: the omnivorous and carnivorous forms, an explicit representation of the bacterial loop: bacteria, labile and semi-labile dissolved organic matter, particulate organic matter. The model simulates oxygen, nitrogen, silicate and carbon cycling. In addition, an innovation of this model is that it explicitly represents processes in the anoxic layer. Biogeochemical processes in anaerobic conditions have been represented using an approach similar to that used in the modeling of diagenetic processes in the sediments lumping together all the reduced substances in one state variable [Soetaert, K., Herman, P., 1996. A model of early diagenetic processes from the shelf to abyssal depths. Geochimica et Cosmochimica Acta 60 (6) 1019-1040]. In this way, processes in the upper oxygenated layer are fully coupled with anaerobic processes in the deep waters, allowing to perform longterm simulations.The mathematical modeling of phytoplankton and zooplankton dynamics, detritus and the microbial loop is based on the model developed by Van den Meersche et al. [Van den Meersche, K., Middelburg, J., Soetaert, K., van Rijswijk P.H.B., Heip, C., 2004. Carbon-nitrogen coupling and algal-bacterial interactions during an experimental bloom: Modeling a 13c tracer experiment. Limnology and Oceanography 49 (3), 862-878] and tested in the modeling of mesocosm experiments and of the Ligurian sea ecosystem [Raick, C., Delhez, E., Soetaert, K., Gregoire, M., 2005. Study of the seasonal cycle of the biogeochemical processes in the Ligurian sea using an 1D interdisciplinary model. Journal of Marine Systems 55 (3-4) 177-203]. This model has been extended to simulate the development of top predators, the aggregation of detritus as well as the degradation and chemical processes in suboxic/anoxic conditions (e.g. denitrification, anoxic remineralization, redox reactions).The coupled model extends down to the sediments ( depth) and is forced at the air-sea interface by the 6 hourly ERA-40 reanalysis of ECMWF data. The model has been calibrated and validated using a large set of data available in the Black Sea TU Ocean Base. The biogeochemical model involves some hundred parameters which are first calibrated by hand using published values. Then, an identifiability analysis has been performed in order to determine a subset of identifiable parameters (i.e. ensemble of parameters that can be together estimated from the amount of data we have at our disposal, see later in the text). Also a subset of 10 identifiable parameters was isolated and an automatic calibration subroutine (Levenberg Marquart) has been used to fine tune these parameters. Additionally, in order to assess the sensitivity of model results to the parameterization of the two gelatinous groups, Monte Carlo simulations were performed perturbing all the parameters governing their dynamics.In order to calibrate the particle dynamics and export, the chemical model was run off-line with the particle and microbial loop model in order to check its capacity of simulating anoxic waters. After a 104 year run, the model simulated profiles similar to observations but steady state was not reached suggesting that the Black Sea deep waters are not at steady state. The fully coupled model was then used to simulate the period 1988-1992 of the Black Sea ecosystem. The model solution exhibits a complex dynamics with several years of transient adjustment. This complexity is imparted by the explicit modeling of top predators. The integrated chlorophyll and phytoplankton biomasses, the maximum concentration and depth of maximum, mesozooplankton biomass, depth of oxycline, primary production, bacterial production, surface concentrations of nutrients and plankton simulated by the model and obtained from available data analysis were compared and showed a satisfactory agreement. Also, as in the data, the model shows a continuous development of phytoplankton throughout the year, with an intense spring bloom dominated by diatoms and a fall bloom dominated by dinoflagellates. Dinoflagellates dominate from summer until late fall while small phototrophic flagellates are never dominant in terms of biomass, but are present almost throughout the year except in winter. The model simulates an intense silicate removal associated to increased diatoms blooms which were promoted by increased nutrient conditions, and by the presence of gelatinous zooplankton. This silicate pumping leads to silicate limitation of diatoms development in summer allowing the development of dinoflagellates. 相似文献
20.
近年来,东海原甲藻赤潮在我国东海近岸海域频繁发生。本研究利用生物-物理耦合模型对发生于2005年的东海原甲藻赤潮进行后报模拟,并对控制其起始与发展的因素展开研究。该模型由东海原甲藻种群动力学模型与多层嵌套的水动力模型组合。通过对比模拟结果与室内实验结果,证实种群动力学模型能够很好地重现东海原甲藻在不同光照与磷营养限制条件下的生长过程,同时能够再现藻细胞内部磷含量及藻类对外部营养盐浓度的影响。耦合模型能够较好地再现模拟海域水动力（见Sun et al.,2016）与东海原甲藻赤潮的时空分布。模拟的赤潮发展过程与此前研究中的观测结果一致,且模拟结果表明模型能够捕捉到赤潮初期种群的次表层孕育现象。随后模拟结果被用于诊断决定赤潮垂直分布的决定性因素,结果表明磷酸盐是控制这一现象的关键因素。同时,表层风场在决定赤潮的分布中扮演着重要角色。模拟结果强调了营养盐限制在东海原甲藻次表层孕育及消散过程中的作用,本文所建立的耦合模型需要进一步优化并应用于其它条件下东海原甲藻赤潮的研究中。 相似文献