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Glacial meltwater has been suggested as a significant source of potentially bioavailable iron to the oceans. However, the supply of dissolved iron (dFe) in glacial meltwaters is poorly constrained as few sites have been studied, and because the chemical processing of Fe during transport from glaciers to the adjacent coastal ocean is not well understood. In order to better constrain glacial fluxes of dFe to the ocean, iron concentrations, iron stable isotopes (δ 56 Fe), and other supporting chemical and physical measurements were made along a ~4 km long glacial meltwater river on Svalbard and in estuarine waters that it flows into. Dissolved iron concentrations in the Bayelva River decreased from a maximum of 734 nM near the glacier to an average value of 116 nM near the mouth of the river. Measurements in the Kongsfjorden estuary suggest that 3 to 10 nM of dFe from the Bayelva River is stabilized in glacial waters by the time it mixes into the ocean. Incubation of Bayelva River waters over two weeks in both the light and dark show similar results, with the majority of dFe being quickly precipitated and 4 to 7 nM Fe stabilized in the dissolved phase. Evidence suggests that Fe is most likely lost from the dissolved phase by aggregation and adsorption of nanoparticulate and colloidal Fe to particles. Dissolved δ 56 Fe was between -0.11‰ and +0.09‰ for all river samples and did not vary systematically with dFe concentrations. We infer that the Fe is lost from the dissolved phase by a process that fractionates Fe isotopes by less than 0.05‰, indicating that the Fe bonding environment does not change during precipitation. This is consistent with DOC loss that is much faster than predicted photo-oxidation rates, suggesting that DOC is also lost through adsorption and precipitation. Dissolved Fe concentrations in the Bayelva River (15-734 nM), and Fe concentrations which are stabilized in the dissolved phase (4-7 nM) are much lower than some previous estimates of Fe in glacial meltwaters, with roughly 80 % of dFe lost during transit in the Bayelva River and roughly 90% of the remaining dFe lost in the estuary. This may mean that glaciers are a less significant source of dissolved Fe to the global oceans than has been previously hypothesized, that cold base glaciers of the type studied here do not contribute significantly to the dissolved Fe flux, or that the flux of reactive particulate Fe to the oceans is more important than the dissolved flux. In Arctic regions with similar proglacial environments, bedrock composition, weathering intensity, and as precipitation of colloidal and nanoparticulate Fe may all play an important role in regulating the glacial meltwater iron flux to the ocean.

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Dissolved methane (CH 4 ) was measured in the waters of the Changjiang (Yangtze River) Estuary and its adjacent marine area during five surveys from 2002 to 2006. Dissolved CH 4 concentrations ranged from 2.71 to 89.2 nM and had seasonal variation with the highest values occurring in summer and lowest in autumn. The horizontal distribution of dissolved CH 4 decreased along the freshwater plume from the river mouth to the open sea. Dissolved CH 4 in surface waters of the Changjiang was observed monthly at the most downstream main channel station Xuliujing (12182 0 E, 31846 0 N), which ranged from 16.2 to 126.2 nM with an average of 71.6 ± 36.3 nM. The average annual input of CH 4 from the Changjiang to the Estuary and its adjacent area was estimated to be 2.24 mol s -1 equal to 70.6 9 10 6 mol year -1 . Mean CH 4 emission rate from the sediments of the Changjiang Estuary in spring was 1.97 lmol m -2 day -1 , but it may be higher in summer due to hypoxia in the bottom waters and higher temperatures. The annual sea to air CH 4 fluxes from the Changjiang Estuary and its adjacent marine area were estimated to be 61.4 ± 22.6 and 16.0 ± 6.1 lmol m -2 day -1 , respectively, using three different gas exchange models. Hence the Changjiang Estuary and its adjacent marine area are net sources of atmospheric CH 4 .

Abstract. Dissolved nitrous oxide (N 2 O) was measured in the waters of the Changjiang (Yangtze River) Estuary and its adjacent marine area during five surveys covering the period of [2002][2003][2004][2005][2006]. Dissolved N 2 O concentrations ranged from 6.04 to 21.3 nM, and indicate great temporal and spatial variations. Distribution of N 2 O in the Changjiang Estuary was influenced by multiple factors and the key factor varied between cruises. Dissolved riverine N 2 O was observed monthly at station Xuliujing of the Changjiang, and ranged from 12.4 to 33.3 nM with an average of 19.4 ± 7.3 nM. N 2 O concentrations in the river waters showed obvious seasonal variations with higher values occurring in both summer and winter. Annual input of N 2 O from the Changjiang to the estuary was estimated to be 15.0 × 10 6 mol/yr. N 2 O emission rates from the sediments of the Changjiang Estuary in spring ranged from −1.88 to 2.02 µmol m −2 d −1 , which suggests that sediment can act as either a source or a sink of N 2 O in the Changjiang Estuary. Average annual sea-toair N 2 O fluxes from the studied area were estimated to be 7.7 ± 5.5, 15.1 ± 10.8 and 17.0 ± 12.6 µmol m −2 d −1 using LM86, W92 and RC01 relationships, respectively. Hence the Changjiang Estuary and its adjacent marine area are a net source of atmospheric N 2 O.

[1] Atmospheric deposition can deliver new nutrients to the surface water and support primary productivity. Here we report a phytoplankton bloom that developed in the Yellow Sea in the spring of 2007 3-4 days following a dust storm accompanied by precipitation. Our data indicate that atmospheric deposition dominated the supply of new nutrients to the surface water in the central Yellow Sea during the dust event. Dust-derived nitrogen (N) supply was sufficient to support the observed phytoplankton growth, while, dust-derived iron (Fe) supply far exceeded that required by the biota. Granger causality test results further supported that dust-derived nutrients deposition was the cause for the observed bloom with a lag of 3-5 days. Our results contribute to the growing database linking phytoplankton blooms to atmospheric deposition derived fertilization effects. Both dry and wet deposition contributed nutrients to the surface ocean during this event; however, the nutrient loading from dry deposition alone was not sufficient to satisfy the demand of the phytoplankton in this bloom event.