Parameter sensitivity study of the biogeochemical model in the China coastal seas

In order to develop a coupled basin scale model of ocean circulation and biogeochemical cycling,we present a biogeochemical model including 12 components to study the ecosystem in the China coastal seas（CCS）.The formulation of phytoplankton mortality and zooplankton growth are modified according to biological characteristics of CCS.The four sensitivity biological parameters,zooplankton assimilation efficiency rate（ZooAE_N）,zooplankton basal metabolism rate（ZooBM）,maximum specific growth rate of zooplankton（μ_（20）） and maximum chlorophyll to carbon ratio（Chl2C_m） are obtained in sensitivity experiments for the phytoplankton,and experiments about the parameter μ_（20＇）,half-saturation for phytoplankton NO_3 uptake（K_（NO_3）） and remineralization rate of small detritusN（SDeRRN） are conducted.The results demonstrate that the biogeochemical model is quite sensitive to the zooplankton grazing parameter when it ranges from 0.1 to 1.2 d^（-1）.The K_（NO_3） and SDeRRN also play an important role in determining the nitrogen cycle within certain ranges.The sensitive interval of KNO_3 is from 0.1 to 1.5（mmol/m^3）^（-1）,and interval of SEdRRN is from 0.01 and 0.1 d^（-1）.The observational data from September 1998 to July 2000 obtained at SEATS station are used to validate the performance of biological model after parameters optimization.The results show that the modified model has a good capacity to reveal the biological process features,and the sensitivity analysis can save computational resources greatly during the model simulation.

Modeling the Effects of Nutrient Dynamics and Surface Circulation on the Productivity of Hooghly Estuary

River estuarine environment plays a key role in the cycling of biological and chemical parameters and a significant region for the transaction of freshwater and seawater. In the present study, a first attempt has been made towards the development of a coupled three-dimensional hydrodynamic circulation model with four compartment （nitrate, phytoplankton, zooplankton and detritus） biogeochemical model in the Hooghly estuary （21 °36′-22° 16′1 and 87°42＇-88°15′E） to simulate the varying effect of plankton biomass with the heavy input of anthropogenic litter from industrial effluents of Haldia port which is effecting the chemical and biological processes that control the plankton dynamics in the estuary. In-situ observational data for physico-chemical and biological parameters are collected from Calcutta University during 2010 are assimilated using multiscale OA （objective analysis） for different seasons and incorporated in ROMS （Regional Ocean Modeling System） to develop a high resolution （0.5 km x 0.5 kin） biogeochemical model. Recent analysis on physico-chemical parameters of the estuary is done as it is one of the largest estuaries in India and is the habitat for vast biodiversity. Influence of high nitrate （above 34 μg/L） and phosphate （5.22 μg/L） is predominant whereas DO （dissolved oxygen） is low （4.07 mg/L） in the Haldi River mouth which is sliding the productivity （less than 1 mg/L） and also affects water quality.

Phosphorus Biogeochemical Cycle Research in Mountainous Ecosystems

Phosphorus(P),as a limiting nutrient,plays a crucial role in the mountainous ecosystem development.Its biogeochemical cycle in mountainous ecosystems determines the bioavailability and sustainable supply of P,and thus becomes a crucial process which needs to be fully understood and described for ecological and environmental conservation.However,most of research about P biogeochemical processes has been carried out in aquatic environment and agronomic field,but rare researches have been done in mountain ecosystem.In the present review,we summarize researches on P biogeochemical cycle concerning mountain ecosystem in recent decades,including rock weathering,the release,transformation and bioavailability of P,interactions between the P biological cycle and microbial and plant life,as well as the development of models.Based on the state of art,we propose the future work on this direction,including the integration of all these research,the development of a practical model to understand the P biogeochemical cycle and its bioavailability,and to provide a reference for ecological and environmental conservation of mountainous ecosystems and lowland aquatic systems.

Are trends in SeaWiFS chlorophyll time-series unusual relative to historic variability

For selected locations in the Atlantic and Pacific Ocean, we compared surface ocean chlorophyll time series extracted from SeaWiFS imagery from 1997-2004 with the results of an ocean coupled circulation and biogeochemical model covering the period 1958-2004. During the 1997-2004 time period, linear trends in model and satellite time series were significantly correlated at most of the 44 sites we studied. Eleven sites were selected for further study, and we used the longer time series of the model to assess whether trends observed during the SeaWiFS period at these 11 sites were unusual in relation to those observed over the longer historical period covered by the model. The results show that the trends observed during the SeaWiFS period were not unusual and fell well within the range in magnitude of linear trends observed in other 8-year periods of model output. This result implies that the SeaWiFS satellite ocean color time series is not yet sufficiently long, on its own, to directly observe any long term changes in phytoplankton chlorophyll that may be occurring in the surface waters of the open ocean as a result of increased ocean stratification linked to global climate changed.

Vertical Chlorophyll and Dimethylsulfide Profile Simulations in Southern Greenland Sea

Biogenetic sulfide dimethylsulfide(DMS)plays a major role on the global climate,especially in Arctic Ocean.Accurate simulate DMS concentration is an important task.Here we introduced both biogeochemical depth-averaged model G93 and its extension model-one dimensional DMS model.Both surface concentrations,vertical profiles of chlorophyll(CHL)and DMS are simulated using the two models within southern Greenland Sea(0°E–10°E,70°N–75°N)during year 2012.As the input data for the models simulations,the spatial monthly mean of methodology forcings including sea surface temperature(SST),wind speed(WIND),cloud cover(CLD),sea ice concentration(ICE)and mixed layer depth(MLD)are calculated.Satellite 8-day time series of chlorophyll-a(CHL)are used as observation data for CHL related parameter calibrations.Simó’s imperial formula is used as the monthly DMS observation data.The Genetic Algorithm technique is used for the parameter calibrations.The simulation results show that the most DMS related surface concentrations exhibit the normal distributions with peak during May.CHL,DMS and DMSP(dimethylsulphoniopropionate)vertical profiles are obtained for July,August and September in year 2012.CHL had the higher variation of subsurface concentration maximum(SCM)in July with the lower surface concentration value.DMS had surface higher and subsurface lower profile for the all three months.DMSP also had subsurface high in July.The SCM CHL diurnal variation in the subsurface also can be resulted from diurnal changes in MLD and vertical mixing variations,plus photolysis and wind-driven ventilations.

Recent Trends in Satellite-Derived Chlorophyll and Aerosol Optical Depth Together with Simulated Dimethylsulfide in the Eastern China Marginal Seas

The biogenic compound dimethylsulfide(DMS)produced by a range of marine biota is the major natural source of re-duced sulfur to the atmosphere and plays a major role in the formation and evolution of aerosols,potentially affecting climate.The spatio-temporal distribution of satellite-derived chlorophyll_a(CHL)and aerosol optical depth(AOD)for the recent years(2011-2019)in the Eastern China Marginal Seas(ECMS)(25°-40°N,120°-130°E)are studied.The seasonal CHL peaks occurred during late April and the CHL distribution displays a clear zonal gradient.Elevated CHL was also observed along the northern and western coastlines during summer and winter seasons.Trend analysis shows that mean CHL decreases by about 10%over the 9-year study period,while AOD was higher in south and lower in north during summertime.A genetic algorithm technique is used to calibrate the key model parameters and simulations are carried out for 2015,a year when field data was available.Our simulation results show that DMS seawater concentration ranges from 1.56 to 5.88 nmol L^(−1) with a mean value of 2.76 nmol L^(−1).DMS sea-air flux ranges from 2.66 to 5.00mmol m^(−2) d^(−1) with mean of 3.80mmol m^(−2) d^(−1).Positive correlations of about 0.5 between CHL and AOD were found in the study region,with higher correlations along the coasts of Jiangsu and Zhejiang Provinces.The elevated CHL concentration along the west coast is correlated with increased sea-water concentrations of DMS in the region.Our results suggest a possible influ-ence of DMS-derived aerosol in the local ECMS atmosphere,especially along the western coastline of ECMS.

Biogeochemical transport of iodine and its quantitative model

Iodine deficiency disorders(IDD) are among the world's most prevalent public health problems yet preventable by dietary iodine supplements.To better understand the biogeochemical behavior of iodine and to explore safer and more efficient ways of iodine supplementation as alternatives to iodized salt,we studied the behavior of iodine as it is absorbed,accumulated and released by plants.Using Chinese cabbage as a model system and the 125I tracing technique,we established that plants uptake exogenous iodine from soil,most of which are transported to the stem and leaf tissue.The level of absorption of iodine by plants is dependent on the iodine concentration in soil,as well as the soil types that have different iodine-adsorption capacity.The leaching experiment showed that the remainder soil content of iodine after leaching is determined by the iodine-adsorption ability of the soil and the pH of the leaching solution,but not the volume of leaching solution.Iodine in soil and plants can also be released to the air via vaporization in a concentration-dependent manner.This study provides a scientific basis for developing new methods to prevent IDD through iodized vegetable production.

Production of dissolved organic carbon in the South China Sea:A modeling study

The South China Sea(SCS)is the largest semi-enclosed marginal sea in the western Pacific.The alternation of East Asian monsoon causes a significant seasonal pattern of chlorophyll,primary productivity,and export flux of sinking particles.However,the source and sink of dissolved organic carbon(DOC)pools with different bioavailability are less studied.Here we evaluated the seasonal production of DOC in labile,semi-labile and refractory forms using a coupled physical-biogeochemical model.This study aims to understand the dynamics and budgets of organic matters in the SCS.Model results show that the production of labile,semi-labile and refractory DOC is highly correlated with the net primary productivity(NPP)which is higher in winter and lower in summer,reflecting a dependence of DOC on the NPP.The seasonal variation in Pearl River discharge dominates the DOC production in the northern coastal region.In the northeast,the Kuroshio intrusion associated frontal system is attributed to cause high winter production.The DOC production in the southwest is controlled by both winter mixing and summer upwelling.The production of refractory DOC with the least bioavailability favors carbon sequestration.Its annual mean production is 1.8±0.5 mg C m^(−2) d^(−1),equivalent to 26%of the export flux of particulate organic carbon at 1000 m.

A meta-analysis of the canopy light extinction coefficient in terrestrial ecosystems

The canopy light extinction coefficient （K） is a key factor in affecting ecosystem carbon, water, and energy processes. However, K is assumed as a constant in most biogeochemical models owing to lack of in-site measurements at diverse terrestrial ecosystems. In this study, by compiling data of K measured at 88 terrestrial ecosystems, we investigated the spatiotemporal variations of this index across main ecosystem types, including grassland, cropland, shrubland, broadleaf forest, and needleleaf forest. Our results indicated that the average K of all biome types during whole growing season was 0.56. However, this value in the peak growing season was 0.49, indicating a certain degree of seasonal variation. In addition, large variations in K exist within and among the plant functional types. Cropland had the highest value of K （0.62）, followed by broadleaf forest （0.59）, shrubland （0.56）, grassland （0.50）, and needleleaf forest （0.45）. No significant spatial correlation was found between K and the major environmental factors, i.e., mean annual precipitation, mean annual temperature, and leaf area index （LAI）. Intra-annually, significant negative correlations between K and seasonal changes in LAI were found in the natural {K=2/π[cosαcosθsina^-1（tanθtanα）＋（1＋cos^2a-cos^2θ^1/2）],a＋θ〉π/2 K=cosαcosθ,α＋θ≤π/2 k K is usually calculated with the Beer Lambert Law （Monsi and Sakei, 1953）：K = - In （Ii/Io） cosθ/（LAIΩ）,（2）ecosystems. In cropland, however, the temporal relation- ship was site-specific. The ecosystem type specific values of K and its temporal relationship with LAI observed in this study may contribute to improved modeling of global biogeochemical cycles.