Climate related shifts in the NCP ecosystem, and consequences for future spatial planning

Een uitgebreide meetinspanning op de Noordzee, in combinatie met wiskundige en statistische modellering, laat zien dat de klimaatveranderingen in de vorm van een verandering in de overheersende windrichting, een toename van de windsnelheid, een toename van de zeewatertemperatuur, als wel als een toenemende CO2 concentratie van de atmosfeer, niet alleen leidt tot een verandering van de samenstelling van het zeewater in de vorm van bijvoorbeeld opgelost anorganisch koolstof en zuurgraad, maar ook tot een, zei het beperkte, verlaging van de productiviteit van op en in de zeebodem levende filterende organismen, die op hun beurt het voedsel zijn van bodembewonende vissen

Preservation of atmospheric dimethyl sulphide samples on Tenax in sea-to-air flux measurements

The low concentration of dimethyl sulphide (DMS) in the atmosphere makes it necessary to concentrate the gas before gas-chromatographic analysis. One of the preferred methods has been to use a cold Tenax adsorbent in this concentration step. DMS concentration onto Tenax-TA traps is shown to be sensitive to temperature and to humidity. Implementation of cooling and concentration devices for the measurement of DMS over the air-sea interface is difficult since these measurements are typically made in exposed conditions where temperature control can be problematic. Instead of concentrating DMS in traps. collecting bulk air in Tedlar bags allows storage for at least one week without loss of DMS. This approach allows the concentration and analysis to be postponed until return to the laboratory where analytical conditions can be much better controlled improving precision and accuracy in DMS measurement needed for gas flux estimation. (C) 2002 Elsevier Science Ltd. All rights reserved

Simultaneous use of relaxed eddy accumulation and gradient flux techniques for the measurement of sea-to-air exchange of dimethyl sulphide

The sea-to-air flux of the biogenic volatile sulphur compound dimethyl sulphide was assessed with the relaxed eddy accumulation (REA) and the gradient flux (GF) techniques from a stationary platform in the coastal Atlantic Ocean. Fluxes varied between 2 and 16 µmol m-2 d-1. Fluxes derived from REA were on average 7.1±5.03 µmol m-2 d-1, not significantly different from the average flux of 5.3±2.3 µmol m-2 d-1 derived from GF measurements. Gas transfer velocities were calculated from the fluxes and seawater DMS concentrations. They were within the range of gas transfer rates derived from the commonly used parameterizations that relate gas transfer to wind speed.

Primary production and eddy correlation measurements of CO2 exchange over an intertidal estuary

Field measurements by eddy correlation indicate an average CO2 uptake of 1.9 g C m-2 d-1 by the intertidal Wadden Sea estuary in spring 2008. The flux did not show a dependency on the tide and fluxes during high and low tide were comparable. We hypothesize that biological production in the water column and in microbial mats that cover sediments lead to an undersaturation of CO2 that is strong enough to support the observed fluxes. The total carbon uptake by this intertidal estuary from day of the year 101–168 is estimated to be -1.7 Tg C. Extrapolation of this flux over three months in spring suggests that the uptake of CO2 by this estuary over this period is comparable to 24% of the yearly carbon flux over the North Sea and the European estuarie

Direct measurements of biogenic dimethylsulphide fluxes from the oceans : a synthesis

Author Posting. © National Research Council Canada, 2004. This article is posted here by permission of National Research Council Canada for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 61 (2004): 836-844, doi:10.1139/F04-047.This paper provides a brief overview of the state-of-the-art of techniques that are currently used for field measurements of trace gas fluxes and the subsequent derivation of gas transfer rates over the oceans. Special attention is given to the relaxed eddy accumulation (REA) and gradient flux (GF) techniques, which rely on empirical functions thus far mainly validated over land. The universality of these functions and their application at sea have not yet been fully evaluated. New experiments have shown that the emission of dimethylsulphide (DMS) can be measured by the REA and GF techniques. Moreover, these measurements have provided parameterizations of gas exchange rates that are within the range of relationships between wind speed and gas transfer that have recently been derived from eddy correlation (EC) and deliberate tracer measurements. Using DMS as a model, gas is potentially a powerful approach to intercalibrate the REA, GF, and EC techniques, test their applicability in the marine environment, and investigate processes that determine trace gas exchange across the ocean surface

Concentração e fluxo de CO2 sobre o reservatório hidrelétrico de Balbina (AM)

The reservoir Balbina (59º 28’ 50w, 1º 53’ 25” S), located near the city of Manaus, Amazonas, in Central Amazônia, Brazil, is the second largest hydroelectric reservoir in an area located in the Amazon Basin. In this reservoir, CO2 measurements were performed at high frequency (10 Hz), CO2 flux with gas analyzer infrared (IRGA) coupled to a floating chamber and meteorological variables with a buoy instrumented to 2 m from the lake surface. The average CO2 concentration was 392 and 426 ppm for the day and night, respectively, and the daily average emission rate was 40.427±24.040 μmol-1.m-2.d-1. The accumulation of CO2 in the lake overnight, beyond respiration, shows to be affected by low wind speeds, waterside convection, physical processes involving high concentrations of CO2 for the surface and the presence of land breeze. The fluxes show no statistically significant difference with the meteorological variables and were considerably lower than a previous study for the same lake. However, the values are in agreement with other studies in Amazonian tropical lakes and other reservoirs. © 2017, ABES - Associacao Brasileira de Engenharia Sanitaria e Ambiental. All rights reserved