Short term effects of hypoxia and anoxia on sediment biogeochemistry
type: CreativeWork
description: Hypoxia and anoxia alter the behaviour, diversity and habitat of the benthic communities and cause accumulation of organic matter and nutrients. Most studies have focused on the effect of anoxia on benthic organisms and little information is available on nutrient sediment-water fluxes and rates of key biogeochemical processes. This study aimed to evaluate the oxygen concentration at which harmful effects start to occur, the rates that the system responds to different levels of oxygen saturation in the overlying water and the recovery times of system processes when re-aeration are restored. Sampling was carried out at Breydon Water, Great Yarmouth in June, 2010 and key biogeochemical processes were monitored in sediment/artificial seawater mesocosms maintained at constant temperature in the laboratory. The experimental work assessed the short term effect of different levels of oxygen by manipulating oxygen into five different treatments; oxic (96% saturation in the overlying water), hypoxia (25% saturation), one day of anoxia (24 hours without oxygen followed by re-aeration of up to 6 days), four days of anoxia (4 days without oxygen and subsequent re-aeration for 3 days) and seven days of anoxia (0% saturation). The effect of these oxygen concentrations on different biogeochemical processes (solute transport, oxygen uptake, nutrient fluxes, porewater chemistry, and enzyme activities) was quantified. Bromide used in solute transport assessments were analysed using inductively coupled plasma mass spectrometry and oxygen was measured using an oxygen minielectrode. Nutrient analysis was carried out using the SKALAR autoanalyser and enzyme activities were measured using microplate based assays. With decreasing oxygen supply, ammonium and phosphate are rapidly released into the water column, and nitrate concentrations decrease, reflecting the reducing conditions. In oxic conditions, rapid transport of water and oxygen into the sediments occurs through irrigation fluxes. S…
abstract: Hypoxia and anoxia alter the behaviour, diversity and habitat of the benthic communities and cause accumulation of organic matter and nutrients. Most studies have focused on the effect of anoxia on benthic organisms and little information is available on nutrient sediment-water fluxes and rates of key biogeochemical processes. This study aimed to evaluate the oxygen concentration at which harmful effects start to occur, the rates that the system responds to different levels of oxygen saturation in the overlying water and the recovery times of system processes when re-aeration are restored. Sampling was carried out at Breydon Water, Great Yarmouth in June, 2010 and key biogeochemical processes were monitored in sediment/artificial seawater mesocosms maintained at constant temperature in the laboratory. The experimental work assessed the short term effect of different levels of oxygen by manipulating oxygen into five different treatments; oxic (96% saturation in the overlying water), hypoxia (25% saturation), one day of anoxia (24 hours without oxygen followed by re-aeration of up to 6 days), four days of anoxia (4 days without oxygen and subsequent re-aeration for 3 days) and seven days of anoxia (0% saturation). The effect of these oxygen concentrations on different biogeochemical processes (solute transport, oxygen uptake, nutrient fluxes, porewater chemistry, and enzyme activities) was quantified. Bromide used in solute transport assessments were analysed using inductively coupled plasma mass spectrometry and oxygen was measured using an oxygen minielectrode. Nutrient analysis was carried out using the SKALAR autoanalyser and enzyme activities were measured using microplate based assays. With decreasing oxygen supply, ammonium and phosphate are rapidly released into the water column, and nitrate concentrations decrease, reflecting the reducing conditions. In oxic conditions, rapid transport of water and oxygen into the sediments occurs through irrigation fluxes. S…
author: Fadhullah, Widad Binti
language: en
date published: 2013-05
date modified: 2026-07-24T02:11:59Z
provider: University of East Anglia
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of East Anglia