The relationship between chromophoric dissolved organic matter and dissolved organic carbon in the European Atlantic coastal area and in the West Mediterranean Sea (Gulf of Lions)

The absorption coefficient of chromophoric dissolved organic matter (aCDOM) has been found to be correlated with fluorescence emission (excitation at 355 nm). In the coastal European Atlantic area and in the Western Mediterranean Sea (Gulf of Lions), a significant statistical dependence has been found between aCDOM and fluorescence with dissolved organic carbon (DOC) concentration. The relationship shows that, in the river plume areas (Rhine in the North Sea and Rhône in the Gulf of Lions), a consistent fraction of DOC (from 40% to 60% of the average of the DOC measured) is non-absorbing in visible light range, where the dissolved organic matter (DOM) is typically absorbent. In comparison, in the open sea, apparently not affected by the continental inputs, the entire DOC belongs to the chromophoric DOM whose specific absorption is lower (5 to 10 times) than that found in the river plume areas.     

Transportation of water,particulate and dissolved organic and inorganic matter between a salt marsh and the Ems-Dollard estuary,The Netherlands

Transport processes were studied in a gully between a salt marsh and an estuary. After storm tides, ebb currents in the gully reached high values. It is concluded that particulate matter (both organic and inorganic) are imported into the marsh. Coarse organic debris is exported during storm tides, but this amount is low when compared with the primary production on the marsh. Exports are shown for dissolved organic carbon, ammonia, phosphate and silica, while nitrate and possibly nitrite are imported. Organic matter derived from in situ production and net import is buried and partly mineralized in the marsh.     

Settleable and Non-Settleable Suspended Sediments in the Ogeechee River Estuary, Georgia, U.S.A.

Suspended particle dynamics were investigated in the Ogeechee River Estuary during neap tide in July 1996. Samples were operationally separated into ‘ truly suspended ’ (settling velocity <0·006 cm s⁻¹) and ‘ settleable ’ (settling velocity >0·006 cm s⁻¹) fractions over the course of a tidal cycle to determine whether these two fractions were comprised of particles with differing biological and chemical characteristics. Total suspended sediment, organic carbon and nitrogen, chlorophyll a and phaeopigment concentrations were measured in each fraction, as well as rates of bacterial hydrolytic enzyme activity [β-1,4-glucosidase (βGase) and β-xylosidase (βXase)]. The majority of the suspended sediment (by weight) was in the truly suspended fraction; all measured parameters were largely associated with this fraction as well. When compared to the settleable material, the truly suspended material was significantly higher in % POC (5·7±0·6 vs. 3·9±1·8), % chlorophyll (0·07±0·02 vs. 0·03±0·01), % phaeopigment (0·030±0·006 vs. 0·018±0·012), and weight-specific maximal uptake rates (V_maxper mg suspended sediment) of both enzymes (1·8±0·4 vs. 0·7± 0·2 nmol mg⁻¹ h⁻¹βGase and 1·1±0·3vs . 0·3±0·2 nmol mg⁻¹ h⁻¹βXase), providing clear evidence for a qualitative distinction between the two fractions. These results are interpreted to mean that the more organic-rich, biologically active material associated with the suspended fraction is likely to have a different fate in this Estuary, as ‘ truly suspended ’ sediments will be readily transported whereas ‘ settleable ’ sediments will settle and be resuspended with each tide. These types of qualitative differences should be incorporated into models of particle dynamics in estuaries.     

The satellite reversion of dissolved organic carbon (DOC) based on the analysis of the mixing behavior of DOC and colored dissolved organic matter: the East China Sea as an example

The retrieval of dissolved organic carbon (DOC) distribution by remote sensing is mainly based on the empirical relationship of DOC concentration and colored dissolved organic matter (CDOM) concentration in many literatures. To investigate the nature of this relationship, the distributions and mixing behaviors of DOC and CDOM are reviewed in the world’s major estuaries and bays. It is found that, generally, the CDOM concentration is well correlated with the salinity in most estuaries, while DOC usually shows a nonconservative behavior which leads to a weak correlation between the DOC concentration and the CDOM concentration. To establish a good satellite reversion of the DOC concentration, the East China Sea(ECS) was taken as an example, and the mixing behavior of DOC and CDOM as well as the influence of biogeochemical processes were analyzed except for the physical mixing process with the data from late autumn (November, 2010) and winter (December, 2009) cruises. In the two ECS cruises, the CDOM concentration was found to be tightly correlated with the salinity, influenced little by the photochemical or biological processes. The data from the winter cruise show that DOC followed a conservative mixing along the salinity gradient, while in the late autumn cruise it was significantly affected by the biological activities, resulting in a poor correlation between the DOC and the CDOM. Accordingly, an improved DOC algorithm (CSDM) was proposed: when the biological influence was significant (Chl a greater than 0.8 μg/dm3 ), DOC was retrieved by the conservative and biological model, and if the conservative mixing was dominant (Chl a less than 0.8 μg/dm3 ), the direct DOC concentration and CDOM concentration relationship was used. Based on the proposed algorithm, a reasonable DOC distribution for the ECS from satellite was obtained in this study, and the proposed method can be applied to the other large river-dominant marginal sea.     

The composition of phytoplankton within the Chesapeake Bay plume and adjacent waters off the Virginia coast,U.S.A.

Phytoplankton composition differences were used to identify and plot the extent of the Chesapeake Bay plume over the continental shelf. Distinct but different phytoplankton assemblages were noted within the plume for March, June and October 1980. The major constituents in the plume were Skeletonema costatum, a variety of other diatoms and an unidentified ultraplankton component assumed to consist of several cyanophycean and chlorophycean species. The shelf plankton outside of the plume was mainly characterized by the coccolithophores and other phytoplankters that formed different seasonal assemblages than what was within the plume. Patchiness and fluctuations in the shape, size and extent of the plume were noted. A total of 235 species is given, with their presence within the plume and at shelf stations indicated.     

江苏海岸带盐沼潮滩在小尺度下的沉积变化过程

在小尺度范围内,潮滩沉积的研究一般都是基于几个站位或断面进行短时日的调查和监测来获取数据,或多或少地存在数据的连续性不足等问题。基于此,本文在潮滩地貌典型的江苏平原海岸选取了约160 000 m²的盐沼潮滩作为研究对象,在多年的野外连续观测下,分析了人类围垦活动对盐沼潮滩沉积过程及变化的影响。结果表明：人类围垦活动（如堤坝建设等）对潮滩沉积和盐沼植被覆盖的变化有重要影响。围垦堤坝修建之前,研究区向陆一侧为盐沼植物（现为养殖池）,向海一侧为光滩,岸线形态比较平直。在2006年围垦堤坝修建后,研究区变为“凹岸”型的人工岸线,沉积环境变得更有利于泥沙的淤积。根据2007-2012年对滩面高程的野外观测,在风暴潮的影响下,潮滩最大淤积率高达23 cm/a。盐沼植被在泥沙快速淤积的基础上不断发育生长,盐沼植物覆盖面积不断扩张。同时外部的沙嘴也在不断增长,潮汐风浪侵蚀携带沙嘴外部泥沙进入盐沼滩地,盐沼植物在泥沙的覆盖下,出现萎缩退化,覆盖面积减少,但是对潮滩上的泥沙而言还是不断堆积增厚。柱状样岩芯的粒度垂向剖面特征也记录了盐沼潮滩沉积环境的变化。小尺度下盐沼潮滩沉积表现出的阶段性变化规律,揭示出合理的围垦活动有利于堤坝前的潮滩淤积和盐沼植被的扩张。     

南极罗斯海柱样沉积物中有机碳和氮元素地球化学特征及其来源

南极周边海域沉积物中的有机碳和氮元素地球化学特征对于深入研究全球碳循环和海洋生态环境演变具有重要意义。本文对取自南极罗斯海的RBA08C柱状样沉积物进行了有机碳和氮元素地球化学特征分析。结果表明：RBA08C柱样中TOC含量在顶部0~12cm呈现随柱深增加而降低的趋势, 自12cm以深含量总体相对稳定; TN总体具有与TOC相同的变化趋势, 两者含量变化呈现较强正相关性, 说明可能具有相同来源; 沉积物TOC/TN比值和δ13C值揭示RBA08C柱样有机质主要为海洋生源沉积, 其含量变化应主要受控于上层水体生产力、沉积速率和氧化还原环境等因素的共同作用; RBA08C柱样的TOC埋藏率约为50%, 与位于普里兹湾埃默里冰架边缘的IS-4站柱样相同, 加之较为相近的TOC和TN含量及变化趋势, 表明两者可能具有相近的沉积速率, 其所在的海区是南极海域较重要的碳循环和碳储区。     

Argo: A new tool for environmental monitoring and assessment of the world’s oceans, an example from the N.E. Pacific

Argo is an international project that is deploying profiling drifters in all of the oceans of the world, with the exception of the Arctic Ocean. Though still in its implementation phase the Argo array is now supplying an impressive amount of data which offers new opportunities to assess and monitor the environmental status of many regions of the world oceans. Recently, changes in the Gulf of Alaska have been documented by other means that suggest large changes in the T/S relationships and related changes in nutrient supply and productivity. This paper examines these unusual changes to demonstrate the use of the Argo database to determine the physical status of an ecosystem. While the methods of analysis are general, they are here specifically applied to the N.E. Pacific Ocean. We show how it is possible to monitor the baroclinic geostrophic circulation fields in near real-time and correlate these changes with alterations in the stratification of the upper water column.