Adjacent Marine Area Research Articles

Nitrous oxide in the Changjiang (Yangtze River) Estuary and its adjacent marine area: Riverine input, sediment release and atmospheric fluxes

Abstract. Dissolved nitrous oxide (N2O) was measured in the waters of the Changjiang (Yangtze River) Estuary and its adjacent marine area during five surveys covering the period of 2002–2006. Dissolved N2O concentrations ranged from 6.04 to 21.3 nM, and indicate great temporal and spatial variations. Distribution of N2O in the Changjiang Estuary was influenced by multiple factors and the key factor varied between cruises. Dissolved riverine N2O 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. N2O concentrations in the river waters showed obvious seasonal variations with higher values occurring in both summer and winter. Annual input of N2O from the Changjiang to the estuary was estimated to be 15.0 × 106 mol/yr. N2O 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 N2O in the Changjiang Estuary. Average annual sea-to-air N2O fluxes from the studied area were estimated to be 7.7 ± 5.5, 15.1 ± 10.8 and 17.0 ± 12.6 μmol m−2d−1 using LM86, W92 and RC01 relationships, respectively. Hence the Changjiang Estuary and its adjacent marine area are a net source of atmospheric N2O.

The nitrogen isotopic composition of dissolved nitrate in the Yangtze River (Changjiang) estuary, China

The nitrogen isotopic composition of dissolved nitrate (δ 15N-NO 3 −) in surface water of the Yangtze River estuary was determined in four seasons of 2006. δ 15N-NO 3 − ranged from 0.4‰ to 6.5‰ and varied with seasons and geographic regions, reflecting the dynamics of nitrogen cycling in the estuarine ecosystem. δ 15N-NO 3 − was markedly lower in February than in other seasons and exhibited conservative mixing, which was probably attributed to the NO 3 − being sourced from the atmospheric deposition and agricultural fertilizer. In the upper estuary, the influence of riverine inputs was important during all surveys. In the turbidity maximum zone, nitrification was found with nitrate depleted in 15N in May, whereas denitrification resulting in heavy δ 15N-NO 3 − played an important role in August. More enriched δ 15N-NO 3 − values coinciding with losses of nitrate concentrations based on the conservative mixing model were found in the adjacent marine area in May, and may reflect obvious phytoplankton assimilation of dissolved nitrate. In this manner, δ 15N-NO 3 − may be a sensitive indicator of nitrogen sources and biogeochemical processing existing in this estuary in conjunction with the variations of dissolved nitrate and other environmental factors.

Methane in the Changjiang (Yangtze River) Estuary and its adjacent marine area: riverine input, sediment release and atmospheric fluxes

Dissolved methane (CH4) was measured in the waters of the Changjiang (Yangtze River) Estuary and its adjacent marine area during five surveys from 2002 to 2006. Dissolved CH4 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 CH4 decreased along the freshwater plume from the river mouth to the open sea. Dissolved CH4 in surface waters of the Changjiang was observed monthly at the most downstream main channel station Xuliujing (121o2′E, 31o46′N), which ranged from 16.2 to 126.2 nM with an average of 71.6 ± 36.3 nM. The average annual input of CH4 from the Changjiang to the Estuary and its adjacent area was estimated to be 2.24 mol s−1 equal to 70.6 × 106 mol year−1. Mean CH4 emission rate from the sediments of the Changjiang Estuary in spring was 1.97 μmol 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 CH4 fluxes from the Changjiang Estuary and its adjacent marine area were estimated to be 61.4 ± 22.6 and 16.0 ± 6.1 μmol 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 CH4.

Dynamics of particulate major and trace elements in the lower reaches of the Daugava River and adjacent area of the Gulf of Riga (Baltic Sea)

Suspended particulate matter (SPM) was collected in the freshwater–seawater mixing zone in the lower reaches of the Daugava River (Latvia) and adjacent marine area, during five cruises in 1998–2001. The study focused on biogeochemical phase exchange processes. SPM in the freshwater was found to be mainly allochthonous with a high content of organic matter, Mn and sorbed phosphate. Property-salinity plots suggested flocculation of humic-Fe complexes across the salinity gradient. The variability of sorbed phosphate was related to particulate Fe, although no dependence on pH and ionic strength was observed. The Mn contents of SPM mainly follow conservative mixing, but there are also indications of interface exchange of Mn in the mixing zone. The geochemical behaviour of particulate Al appears to differ from that of Fe. In early spring, trace element contents in SPM (Cr, Ni, Cu, Zn, Cd, Pb) correlate tightly with particulate organic matter, whose distribution is linked to phytoplankton distributions.

Assesment of load influence of the Akademik Vernadsky Antartic Station on the quality of adjacent marine area

Discharge of pollutants into Argentine Archipelago marine environment is assessed and the discharge loads are calculated as a follow-up of the work performed at the Ukrainian Antarctic Station “Akademik Vernadsky”. The calculations were made on the basis of the model used for development of “The Procedure for Accelerated Inventory of Environmental Pollution Sources”. Basic points of the used method-model are described to show its capacity to develop the measures and priorities to reduce pollution of the adjacent sea areas. Comparison is made between the calculated discharge value and the experimental data. The proper comparison of calculated data with experimental results makes it possible to come to the conclusion about the possibility to use the Procedure in practice to assess the effect of the Ukrainian Antarctic Station on the marine environment. The nomograms presented in the paper/report can be used for such assessment.&nbsp

Observações sobre o ciclo de vida da corvina, Micropogonias furnieri (Desmarest) (Teleostei, Sciaenidae), no litoral do Estado do Paraná, Brasil

A survey performed in the Guaratuba Bay (25o52'S; 48o39'W) and the adjacent marine area has provided additional data about the habits of the croaker in the southern coast of Brazil. A dynamic pattern of movements along the marine and estuarine waters was observed, but it does not indicate spawning activity in the study area. During autumn/winter, pre-adults and adults use the marine waters. In spring/summer, following gonadal maturation,the individuals leave this area and probably move to deeper waters, where they spawn. Until the end of summer, the estuary is then occupied by juveniles coming from the marine spawning area. In autumn/winter, these juveniles and the new pre-adults move to the marine zone adjacent to the bay and begin gonadal maturation. It is suggested that the Guaratuba Bay and the adjacent marine area constitute an important site for growth and recruitment of the early lifestages of M. furnieri and initial stages of reproductive activity.

Mercury in the Tinto-Odiel Estuarine System (Gulf of Cádiz, Spain): Sources and Dispersion

The Tinto and Odiel are small rivers draining one of the largest sulphide deposits in the world. As a result of these deposits and a large industrial complex, the adjacent marine area receives a high amount of metal input. Mercury distribution in the Tinto-Odiel estuary, the Huelva Ria and the Gulf of Cadiz was assessed in water and suspended particulatematter (SPM) and sediments. In the rivers and estuaries, dissolved (HgD)and particulate (HgP) mercury showed wide variations (13 to 200 pM and0.3 to 330 nmol g-1 respectively) depending on the presence or notof sulphidic waters, phosphogypsum deposits, detrital pyrite and oxyhydroxides.In the Ria, concentrations were lower than 10 pM and 4.5 nmol g-1 for HgD and HgP respectively. In surface waters of the Gulf of Cadiz, the average HgD concentration (pm standard deviation) was 2.9 pm 0.9 pM, which is similar to that of North Atlantic Central Waters. The surface sediments collected in the rivers, the Ria and the Gulf showed systematically enriched mercury compared to pre-industrial levels. Vertical mercury profiles in dated sediment cores were typical of anthropogenically influenced environments starting in the early Roman age. These distribution features suggest that most of the Hg discharged by the Huelva Ria is trapped in the sediments of the Gulf of Cadiz.