Nutrient status in the Yellow Sea Su Mei LIU Ocean University of China

Coastal waters receive large amounts of nutrients from point and non-point sources: However, excess nutrients can be highly damaging, leading to effects such as anoxia and hypoxia from eutrophication, nuisance algal blooms, dieback of seagrasses and corals, and reduced population of fish and shellfish In moderation, nutrient inputs to coastal seas can be considered beneficial. They result in increased production of phytoplankton, which in turn can lead to increased production of fish and shellfish Eutrophication also may change the plankton-based food web from one based on diatoms toward one based on flagellates or other phytoplankton, which are less desirable as food to organisms at higher trophic levels

( KORDI, 1998) Concentrations (  M) of nutrient species of the Yellow Sea SpeciesSummerWinter SurfaceNear- bottom SurfaceNear- bottom NH NO NO PO SiO

Isolines of means of vertically integrated nitrate, phosphate and silicate (  M) (Liu et al., 2003)

Vertical profiles of nutrients at section from the Changjiang Estuary (water depth: 20 m) to the Cheju Island (100 m)

Plots of vertical distributions for salinity and temperature at Section A in September 2002 Cruise (Liu, unpublished data)

Plots of nutrient species (NO 3 -, PO 4 3-, SiO 3 2-, DON, DOP ) at Section A (  mol l -1 ) (Liu, unpublished data)

Variability of salinity, temperature and nutrients (  mol l -1 ) at Anchor station E2 (Liu, unpublished data)

Variation trends of annual mean of the water column average temperature and salinity in the Yellow Sea (Lin et al., 2005) temperature salinity

Variation trends of annual mean of the water column average DO concentration in the Yellow Sea DO concentration (Lin et al., 2005)

Variation trends of annual mean of the water column average nutrient concentrations and N/P in the Yellow Sea PO 4 3- concentration SiO 3 2- concentration DIN concentration N / P (Lin et al., 2005)

Comparison of chlorophyll a (  g dm -3 ), primary production (mgC m -2 d -1 ) and phytoplankton abundancea (  10 4 cell m -3 ) in the Yellow Sea between two periods (Lin et al., 2005)

Changes in the structure and composition of the fish assemblages in the southern Yellow Sea were examined based on data collected from bottom trawl surveys in winter over the period 1985–2002. Species diversity showed a decreasing tendency before 1992 and an increasing trend thereafter for the whole fish assemblage (Xu and Jin, 2005) Temporal trends in diversity H and evenness indices J for the whole fish assemblage in the southern Yellow Sea

Deposition mmol m -2 yr -1 Contribution in terrigenous input Reference South North Sea71 27 ％ Rendell et al. ， 1993 Delaware Bay75 5％5％ Russell et al. ， 1998 Kattegat69 30 ％ Asman et al. ， 1995 North Atlantic coast ％ Galloway et al. ， 1996 Yellow Sea90.542% Bi, unpublished data Atmospheric nitrogen deposition Atmospheric nitrogen deposition supports 8-70 % of new production of surface ocean for the global （ Duce et al., 1986 ； Paerl et al., 1990 ）

In mediterranean sea, atmospheric phosphorus deposition represents 1/3 of input of total terregenous inorganic P （ Guerzoni et al., 1999 ）。 In the east part of mediterranean sea where P limits the growth of primary production, atmospheric P deposition may support up to 38 ％ of new production of surface ocean in summer and fall （ Markaki et al., 2003 ） Atmospheric phosphorus deposition

Plot of Chl-a concentrations (mg m -3 ) during the incubation periods in the south Yellow Sea (Zou et al., 2000)

Dissolved inorganic N:P and Si concentrations at three stations and for rainwater samples (Zou et al., 2000)

Aerosol sources at Qianliyan Island Using the NOAA HYSPLIT_4 model, backward trajectories of aerosols 48 hours before sampling are calculated to track their sources

Aerosol sources at Qianliyan Island

The concentrations of TSP （ µg m -3 ) and nutrients (nmol m -3 ) from land-source and sea-source at Qianliyan Island (Bi, unpublished data)

Element concentrations are plotted against rainfall (Zhang and Liu, 1994) NO Rainfall PO Rainfall SiO Rainfall

Dry and wet depositions of nutrients at Qianliyan Island (Bi, unpublished data)

Dry and wet deposition fluxes at Qianliyan (mmol m -2 yr -1 ) (Bi, unpublished data)

New production simulated by atmospheric deposition (AD-NP) and primary production of the Yellow Sea (PP) ( Bi, unpublished data; Zhang et al. ， 2005)

Comparison of nutrients in aerosols in dust storm and non-dust storm at Fulongshan Dust storm aerosols: low N and high Si high P (Bi, unpublished data)

Atmospheric deposition (  10 9 mol yr -1 ) of dissolved silicate to the Yellow Sea in comparison with other pathways and/or sources. In the table, dry deposition is estimated by the product of dust fallout and solubility of silica Coastal Ocean AtmosphereRiverKuroshio WatersTaiwan Strait Water WetDrySurfaceSub- surface Yellow Sea East China Sea (Zhang et al., 2005)

(Zhang and Liu, 1994) Frequency of toxic bloom events (% of annual occurrences) is plotted against monthly average depositions of nutrient elements (% of annual deposition). The figure shows close correlations between toxic blooms and atmospheric nutrient depositions. No bloom events were observed between December and March in the studied region, when the ambient water temperature is   C

Drainage area, water discharge and sediment loads of some major Chinese rivers RiverDrainage area (×10 6 km 2 ) Water discharge (×10 9 m 3 yr -1 ) Sediment load (×10 6 tons yr -1 ) Yalujiang Changjiang

Nutrient concentrations (  M) in rivers in China Data are from Liu and Zhang (2004); Zhang (2002); Liu et al., (2003) RiverNO 3 - NO 2 - NH 4 + PO 4 3- SiO 3 2- DIN/P Yalujiang Changjiang

The estimated monthly water discharge of the Changjiang emptying into the Yellow Sea (  10 9 m 3 ), and its percent of the Changjiang discharge (Liu et al., 2003)

Variability of nutrients (N and P) in the Changjiang. a Relationship between yearly fertilizer application over the drainage basin and riverine concentration (e.g. DIN) of Changjiang at river mouth over the last 20 years (1980–1999); b observed N/P ratio from various cruises at the river mouth (  2 = 0.22) (Zhang, 2002)

RiverNO 3 - NO 2 - NH 4 + PO 4 3- SiO 3 2- Xinyihe Xinmuhe Qiangweihe Shanhuohe Zhongshanhe Huaihe cannel Subei irragation trench Sheyanhe Yunmianhe Huangshahe Liminhe Xinyanggang The concentrations of nutrients in some rivers of the western part of the Yellow Sea (  mol/l) obtained in winter in 2004 and spring in 2005 (Zhang, unpublished data)

Relationship between nutrients in the major and tributaries of the lower reaches of the Huaihe (Zhang, unpublished data)

May 1996 Cruise Salinity (Liu and Zhang, 2004)

Salinity at C2 station in 1996 cruise (Liu and Zhang, 2004)

Nutrient Yields (mol km -2 day -1 ) from Yalujiang Watersheds SeasonCruiseNO 3 - NO 2 - NH 4 + PO 4 3- SiO 2 Flood08/ Flood08/ Dry05/ The areal yields of nutrient species over the drainage basin of Yalujiang can be estimated by the product of nutrient concentration in the upstream region with discharge divided by the catchment surface area (Liu and Zhang, 2004)

Nutrient Flux to the Yellow Sea

Chemical Flux (  10 6 mol month -1 ) of Nutrient Species towards the Yellow Sea from Yalujiang Estuary SeasonCruiseNO 3 -NH 4 + PO 4 3- SiO 2 Flood08/ Flood08/ Dry05/ (Liu and Zhang, 2004)

Seaward Nutrient Transport: Flood Season CA: erosion from the catchment area CT: waste drainage from the urbanized region RE: estuarine regeneration (Liu and Zhang, 2004)

Seaward Nutrient Transport: Dry Season CA: erosion from the catchment area CT: waste drainage from the urbanized region RE: estuarine regeneration (Liu and Zhang, 2004)

Nutrients in the Chinese estuaries Nutrients can be conservative and/or remobilized, depending upon the system studied Dissolved silica Nitrate (Zhang, 2002) Scavenging and/or remobilization through particles as reaction media are definitely significant in highly turbid Chinese systems NH 4 + PO 4 3–

Nutrient budgets (k mol s -1 ) for the Yellow Sea Negative and positive values of nutrient exchange and sink/source terms indicate the loss from and input into the Yellow Sea, respectively (Liu et al., 2003)

(from Jahnke et al., 2005) Summary of primary production and respiration on the South Atlantic Bight continental shelf Regeneration in sediment

Although the external nutrient loading has been reduced, nutrients could gradually be released back into the water column from the contaminated sediments and delay improvement of the water quality (Hu et al., 2001). Rate of release of nutrients from sediment in Tolo Harbour in Hong Kong (3) (62)

Concentration of chlorophyll a in the water column in the Archipelago Sea, northern Baltic (Suomela et al., 2005)

Sediments of the coastal environment play an important role in nutrient recycling  the NW Black Sea, the benthic fluxes of P and Si are in the same order of magnitude as compared to the annual nutrient input by the Danube River, whereas the NH 4 + flux from the sediment amounts to ～ 10% of the Danube input (Friedl, 1998)  the Port Phillip Bay, the benthic recycling accounted for 63 and 72 % of the annual N and P input (Berelson et al., 1998)  the Chesapeake Bay, fluxes from sediments supply about % of the nutrient loadings (Boynton and Kemp, 1985)  the South Atlantic, the benthic SiO 3 2- flux ( ～ 6.2  mol y -1 ) is about 3 times greater than the SiO 3 2- discharge of the Zaire River, which is the dominant terrestrial source in this region (Zabel et al, 1998)

Hypoxia can lowered survival of larval fish, mortality of some species of benthic invertebraes, and loss of habitat for some mobile species of fish and shefffish that require higher concentrations of oxygen, such as lobster and codfish (Rabalais and Turner, 2001; Mee, 2001) Processes of nitrification (CH 2 O) 106 (NH 3 ) 16 (H 3 PO 4 ) O 2  106CO HNO 3 + H 3 PO H 2 O Sediment nitrification is not only a major source of nitrate for denitrification, but is often an important component of oxygen consumption, accounting for as much as 30% of oxygen demand in estuarine and coastal marine sediments (Seitzinger and Nixon, 1985; Christensen and Rowe, 1994).

The number of HABs has been increasing dramatically after 1990s Frequency of harmful algal blooms (HABs) in the Changjiang Estuary large-scale (ca km 2 ) blooms of Prorocentrum dentatum in the region adjacent to the Changjiang Estuary in Zhang J., unpublished data; Li et al., 2002

(modified after Shapleigh 2000) Denitrification and Anaerobic Ammonium Oxidation (Anammox) Anammox may be a significant process in marine sediments too, where it can account for more than 60% of anaerobic N 2 production (Dalgaard and Thamdrup ， 2002; Thamdrup and Dalsgaard 2002) Denitrification (CH 2 O) 106 (NH 3 ) 16 (H 3 PO 4 ) HNO 3  106 CO N 2 +H 3 PO H 2 O

Nitrate in porewater samples (Liu, unpublished data)

Ammonium in porewater samples (Liu, unpublished data)

Phosphate in porewater samples (Liu, unpublished data)

Silicate in porewater samples (Liu, unpublished data)

Comparison of the benthic fluxes of nutrients in the Yellow Sea with the other areas (mmol/m -2 ·d -1 ) RegionPO 4 3- SiO 3 2- NH 4 + Narragansett Bay Chesapeake Bay Skagerrak ， North sea San Pedro Basin San Francisco Bay East Shelf of North Pacific 6 0~ ~1.0 Northwestern Black Sea ~0.3 East China Sea ~ ~3.4 Nansha Islands Bohai Laizhou Bay ~2.52 East China Sea Yellow Sea Archer and Devol, 1992; 2 Berelson et al., 1998; 3 Callender and Hammond, 1982; 4 Devol and Christensen, 1983; 5 Cocicsu et al., 1996; 6 Gomoiu, 1992; 7 Friedl et al., 1998; 8 Aller et al., 1985; 9 Zhou et al., 2001; 10 Liu et al., 2004; 11 Liu et al., 1999; 12 Liu, unpublished data

A schematic of the box model showing the mass balance of 226 Ra in the Yellow Sea (Kim et al., 2005) The submarine discharge of groundwater (i.e. about 1–6.7  m 3 yr -1 or 0.3–1.7 m yr -1 ) was calculated to be at least 40% of the river-water input (~2.3  m 3 yr -1 ). Then, the flux of Si through SGD (4–24  10 9 mol yr -1 ) to be 20–100% of that associated with river discharge (~23  10 9 mol yr -1 )