The distribution of nutrients and the effect of side transport of nutrients on anchovy spawning ground to the southern waters of Shandong Peninsula are discussed based on the data collected in June 2000,May and June 2001.The coastal current and upwelling are the main physical processes of nutrient transport to the southern waters of Shandong Peninsula.The concentrations of nutrients,Chla,the density of anchovy eggs,larva and juvenile fish increase obviously where they are greatly affected by these processes,while the contents of nutrients and Chl-a,the density of anchovy eggs,larva and juvenile fish decrease significantly where these processes diminish or disappear.The investigation suggest that the side transport of nutrients by Lubei(North Shandong) coastal current in the northern area causes the Chl-a content to be high and dense anchovy eggs,larva and juvenile fish to be dense in the coastal area of the Chengshan Cape.In the southern area,the riverine input from Subei irrigation ditch with high content of nutrients inshore and upwelling in the western edge of the Huanghai Sea Cold Water offshore should be responsible for high Chl-a concentration and dense anchovy eggs,larva and juvenile fish.It is possible that these processes of nutrient transport have controlled the anchovy spawning ground to the southem waters of Shandong Peninsula.

Investigations of sediment-water fluxes of nutrients in the Bohai Sea were carried out in September-October 1998 and April-May 1999.The exchange fluxes of nutrients between sediment and sea water were determined by incubating the core-top sediments with overlying water aerated with air.The benthic fluxes of NO₃^-,NO₂^-,NH₄⁺,DIN,DON and TDN in the first cruise and the fluxes of NO₃^-,NO₂^-,NH₄⁺,DIN,DON,TDN,PO₄3^-,DOP and TDP in the second cruise were measured.The exchange fluxes of nutrients in fall were higher than in spring.The benthic nutrient fluxes represented 15%~55% of nutrient budgets in the Bohai Sea.

Subterranean estuaries (STE) are important seawater-groundwater mixing zones with complex biogeochemical processes, which play a vital role in the migration and transformation of dissolved materials. In this study, we first investigated the spatial distributions of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorous (DIP), dissolved inorganic silicon (DSi) and metal elements (As, Ba, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in STE including upper intertidal, seepage face and subtidal zones. We then estimated submarine groundwater discharge (SGD) and associated nutrient and metal element fluxes. From the generalized Darcy’s law method, SGD was estimated to be 30.13 cm/d, which was about 7 times larger than the inflow (4.16 cm/d). The nutrient and metal fluxes from SGD were estimated to be (5.33 ± 4.99) mmol/(m²·d) for DIN, (0.22 ± 0.03) mmol/(m²·d) for DIP, (16.20 ± 2.05) mmol/(m²·d) for DSi, (1325.06 ± 99.10) μmol/(m²·d) for Fe, (143.41 ± 25.13) μmol/(m²·d) for Mn, (304.06 ± 81.07) μmol/(m²·d) for Zn, (140.21 ± 13.33) μmol/(m²·d) for Cu, (84.49 ± 2.94) μmol/(m²·d) for Pb, (37.38 ± 5.51) μmol/(m²·d) for Ba, (27.88 ± 3.89) μmol/(m²·d) for Cr, (10.10 ± 6.33) μmol/(m²·d) for Ni, and (6.25 ± 3.45) μmol/(m²·d) for As. The nutrient and metal fluxes from SGD were relatively higher than those from the inflow, suggesting that nearshore groundwater acted as the sources of nutrients and metal elements discharging into the sea. The environmental potential pollution of coastal seawater was evaluated by pollution factor index (P_i), comprehensive water quality index (CWQI), and ecological risk index (ERI). Pb mainly caused potential danger of nearshore environment with considerable contamination (P_i = 5.78 ± 0.19), heavy pollution (CWQI = 4.09) and high ecological risk (ERI = 18.00). This study contributed to better understanding the behavior of nutrients and metal elements and improving the sustainable management of STE under the pressure of anthropogenic activities and climate change.

The nutrients contents and distributions are discussed briefly, based on the data obtained in 1998~1999.Besides explanation of the results, a 20-a time series data of nutrients and biological parameters for central Bohai Sea are reviewed.It is found that both concentration and relative content of nutrients have been changed dramatically.The increase of nitrogen and decrease of phosphate and silicate led to the dramatically increase of N/P ratio and the decrease of Si/N ratio.The situation of nitrogen limiting in central Bohai Sea is gradually changing to that of relative lack of phosphate and silicate The decrease of the Huanghe River input to the Bohai Sea may be responsible for this change.These in turn may limit the growth of diatom and thus promote the development of pyrrophyta if other conditions (e.g.temperature and hydrodynamics) are suitable.We conclude that this may be the major inducement factor of pyrrophyta red tide in the Bohai Sea.

How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems. Increasing evidence shows that similar to water in an oasis in the desert, there are stable nutrient supplies to coral reefs in oligotrophic oceans. Here, with emphasis on the fluxes of organic matter, we summarize at the ecosystem level (1) the multiple input pathways of external nutrients, (2) the storage of nutrients in reef organisms, (3) the efficient retaining and recycling of dissolved and particulate organic matter within coral reef ecosystems, (4) the distinctly high phytoplankton productivity and biomass inside and near oceanic coral reefs, and (5) the export of reef-related organic carbon to adjacent open oceans. These properties enable coral reefs to function as ecological “pumps” for gathering nutrients across ecosystems and space, retaining and recycling nutrients within the ecosystem, supporting high phytoplankton productivity, and exporting organic carbon to adjacent open oceans. Particularly, the high phytoplankton productivity and biomass make waters around coral reefs potential hotspots of carbon export to ocean depths via the biological pump. We demonstrate that organic carbon influx is vital for coral reef ecosystems’ carbon budget and carbon export. The concept of the coral reef ecological pump provides a framework to improve the understanding of the functioning of the coral reef ecosystem and its responses to disturbance. Prospects of the coral reef ecological pump in coral reef studies are discussed in changing oceans driven by human activities and global change in the Anthropocene.

The distribution of nitrate,nitrite,ammonia,phosphate and silicate in pore-water and their exchange between sediments and overlying waters (benthic flux) were determined at nine locations on the shelve of Huanghai and East China Seas.On the basis of the redox potential of sediments and nutrients distributions in the pore-waters,it is found that the benthic sediments are being in a suboxic to anoxic environment in the Huanghai and East China Seas.The nutrients distribution in the pore-waters is mainly controlled by the sediment environment,and ammonia is the major inorganic nitrogen in the pore-waters.On the basis of benthic fluxes of untrients calculated using Fick's first law,there is remarkable efflux of ammonia,dissolved inorganic nitrogen(DIN),phosphate and silicate from the sediments to the overlying waters in the study area,and their benthic fluxes are 299.3~2 214.8,404.4~2 159.5,5.5~18.8 and 541.3~1 781.6 μmol/(m²·d) respectively,and perhaps they are the major source of dissolved inorganic nitrogen,phosphate and cate for the overlying water.At most stations,the nitrate flux was from the overlying waters to the sediments,which suggests that suboxic organic matter decomposition via denitrification is dominated in the most area of Huanghai and East China Seas.High benthic fluxes appearing in the coastal area and relatively low benthic fluxes occurring in the shelf area are found and are consistent with primary productivity zoning in the study area.On the other hand,the ammonia flux displays an exponential decrease with water depth increase and an exponential increase with the bottom water temperature.However,others do not display this trend.

This research investigated eight stations in Clarion-Clipperton Fracture Zone (CCFZ) in the eastern tropical Pacific in 2017 to study the spatial distribution characteristics of nutrients and chlorophyll a (Chl a) concentration, and compared nutrient concentrations and molar ratios with those of other investigations 20 years ago in the same area. The study found that dissolved inorganic nutrient (N, P and Si) concentrations were lowest in the upper layer, and increased from surface to some depths, then they decreased a little to the bottom. N was the limited nutrient factor for the growth of phytoplankton community. Although nutrient concentrations and molar ratios have no obvious changes in 2017 comparing those in 1998−2003, supplemented from the equatorial Pacific, nutrient concentrations in the study area were higher than those in seamounts in the North Pacific and Station ALOHA. Furthermore, this study used Generalized Additive Models (GAMs) to infer the underlying bottom-up factors controlling phytoplankton abundance (Chl a concentration), showing that depth, salinity and ${\rm{PO}}_4^{3 - }{\text -}{\rm{ P}} $ concentration were major factors controlling the growth of phytoplankton community. Furthermore, this study can provide basic data and theoretical support for the development of polymetallic nodule area and its long-term impact assessment on the environment.

Being the mightiest river emptying into the East China Sea (ECS) and the Pacific Ocean, compounded with the large increase of nitrogen and phosphorus input due to anthropogenic activities, the Changjiang River (Yangtze River) has become a dominating source of these nutrients to the estuary. The high nutrient concentrations notwithstanding, however, outside of the estuary the high biological productivity of the Changjiang diluted water (CDW) are most probably fueled mainly by nutrient-rich subsurface waters originating from the upwelled Kuroshio waters. This is because while the buoyancy of the CDW spreads it out on the ECS continental shelf, the CDW entrains subsurface waters along with the nutrients. Nutrients thus supplied are several times more than those supplied by the Changjiang River.

Four cruises were conducted during 2002-2003 in the Changjiang Estuary and adjacent coastal areas. The data presented show a clear coast to open sea gradient in nutrients related to the river inputs. Maximum values of chlorophyll a were typically observed at intermediate salinities at surface water and coincided with non-conservative decreases in nutrients along the salinity gradient, indicating that removal of nutrients was related to phytoplankton uptake. The seasonal variations of nutrient concentrations were just opposite to those of chlorophyll a, indicating that the seasonal variations of nutrients were mainly controlled by phytoplankton uptake, whereas riverine inputs merely weakened or balanced its extent. During the estuarine mixing, phosphate demonstrated some remobilization during all the four cruises; whereas both conservative and non-conservative behaviors for dissolved inorganic nitrogen and silicate were observed in the study area, indicating that both biotic and abiotic events may affect their behaviors during the estuarine mixing. Under the influence of freshwater inputs with high value of ratio of nitrogen to phosphorus, the estuarine and coastal waters impacted by the Changjiang plume were high (> 30) in ratio of nitrogen to phosphorus, but rates of primary production were apparently not constrained by any kind of nutrient elements. However, the low (< 1) ratio of silicate to nitrogen in most of the study area might be linked with the rapidly increasing frequency of harmful algal bloom(HAB) incidents in recent years in the coastal waters impacted by the Changjiang plume.

Spatial and temporal distributions of nutrients (N and P) and heavy metals (Cu, Zn, Pb and Cd) in the intertidal sediments at Dongtan wetland of the Changjiang River (Yangtze River) Estuary were examined by laying one transect running seaward to landward during January, April, June, August and October of 2005. Total nitrogen (TN) and heavy metal concentrations in the intertidal sediment showed an increasing trend from open bare flat to the high marsh, with the maximum concentrations in the high marsh and the minimum values in open bare flat. In contrast, sediment total phosphorus (TP) concentrations changed little among sampling sites. One-way ANOVA found that there were significantly temporal variations of nutrients and heavy metals concentrations in the intertidal sediment (P <0.05). The concentrations of heavy metals generally showed an increasing trend from January to October. As compared with other large estuaries, heavy metal contamination in the intertidal sediment of the Changjiang River Estuary was relatively low.