Benthic Oxygen Demand Research Articles

Material supply to the European continental slope: A budget based on benthic oxygen demand and organic supply

Two sites were selected adjacent to the Northeast Atlantic continental shelf to examine material supply to and loss from the benthos. At both a bathyal mid-slope (2000 m water depth) and an abyssal (4800 m water depth) site an in situ technique was used to measure sediment community oxygen consumption. At the mid-slope site a sediment trap mooring provided a measure of the annual vertical flux of material, whereas at the abyssal site, vertical flux was deduced from data obtained nearby. At the mid-slope site, vertical flux was similar to values determined elsewhere in the mesotrophic Northeast Atlantic, but oxygen demand was somewhat higher than values reported for other comparable regions. Vertical flux was, however, sufficient to fuel only 20% of the benthic oxygen demand. A strong seasonal signal was seen from time lapse photographs of the seabed in terms of the quantity of phytodetritus lying on it, but no significant seasonal variation in oxygen consumption was detected. Similarly, on fine spatial scales (between cores) the existence of a detrital layer appeared to have no effect on oxygen demand. It is concluded that substantial quantities of material are transported down slope to this mid-slope region, to provide the organic carbon required by the sediment and that this may be assumed to be the case for the entire particulate pool, including the inorganic fraction. In contrast to the bathyal station, at the deep site on the Porcupine Abyssal Plain, the organic carbon required to fuel benthic oxygen demand was similar to the estimated vertical supply.

Response of benthic oxygen demand to particulate organic carbon supply in the deep sea near Bermuda

OVER the past decade an increasing body of evidence has accumulated indicating that much, perhaps most, of the deep sea floor is an environment of substantial temporal variability1–4. This variability is driven largely by seasonal changes of processes occurring in the surface waters2,3,5. The coupling of the deep sea floor environment to the surface waters is the result of rapid vertical transport of particulate matter through the water column6–8, affording only limited time for degradation before arrival at the sea floor. Studies in the Pacific Ocean have indicated that temporal variations in particulate organic carbon fluxes to the sea floor are accompanied by temporal variability in sediment oxygen demand by as much as a factor of four1,2. We report here time-series studies of oxygen fluxes into the sediments of the oligotrophic Atlantic near Bermuda which contrast sharply with these previous reports. At the Bermuda site, despite large seasonal variations in particulate organic carbon fluxes, in situ measured sediment oxygen consumption does not vary significantly. These results imply that large areas of the sea floor may be characterized by seasonally invariant sediment oxygen demand.

Nutrient regeneration and oxygen demand in Bering Sea continental shelf sediments

Measurements of seabed oxygen demand and nutrient regeneration were made on continental shelf sediments in the southeast Bering Sea from 1 to 15 June 1981. The mean seabed oxygen demand was relatively modest (267 μM O 2 m −2 h −1), equivalent to a utilization of 60 mg organic carbon m −2 day −1. The seasonal build up of ammonium over the mid-shelf domain was generated at least in part by the bottom biota, as previously suggested ( Whitledge et al., 1986 , Continental Shelf Research, 5, 109–132), but on the outer shelf nitrate replaced ammonium as the dominant inorganic nitrogen compound that was regenerated from the sediments. Comparison of oxygen consumption with the organic matter in sedimenting particulate matter (sampled with sediment traps) could imply that benthic processes were not accounting for the fate of considerable quantities of organic matter. Benthic oxygen demand rates, however, probably lag behind the input of the spring bloom to the bottom, thus extending the remineralization process out over time. Consumption by small microheterotrophs in the water column was also a likely sink, although shelf export and advective transport north were possible as well. Estimated nitrification rates in surface sediments could account for only a small fraction of the abrupt increase in nitrate observed in the water column over the shelf just prior to the spring bloom.

Carbon cycling in coastal sediments: Estimating remineralization in Buzzards Bay, Massachusetts

Accurately estimating rates of remineralization of organic matter in sediments (early diagenesis) is a prominent problem for benthic ecologists as well as organic geochemists. McNichol et al. (1988) employed a novel approach to the problem by separating CO{sub 2} produced by respiration from CaCo{sub 3} dissolution, thus theoretically eliminating the need to measure the reduction of terminal electron acceptors in respiration (O{sub 2} NO{sub 3}, SO{sub 4} etc.). Pioneered by Emerson et al. (1980) and Sayles (1981) for deep-sea sediments, this method employs measurements of Ca{sup 2+} in porewater to differentiate between carbonate dissolution and respiration. McNichol et al. (1988) were able to plot metabolic CO{sub 2} profiles over the surface 20 to 30 cm of sediment over an annual cycle at a single station in Buzzards Bay, MA. They used the carbon dioxide profiles in a vertical exchange and reaction model to estimate total organic carbon remineralization per year. Lower Buzzards Bay where McNichol et al. (1988) worked is well studied because of its proximity to the research institutions in Woods Hole. It is the authors intention in this paper to compare the results of these older benthic metabolism studies in Buzzards Bay with those inferred from the modelmore » of the porewater carbon dioxide profile. The published data from three studies have been converted from mL O{sub 2} M{sup {minus}2}H{sup {minus}1} to millimoles and plotted over a 12-month period, thus illustrating the seasonal change in total benthic oxygen demand. The temperature data available at the sites plotted over the year have a somewhat similar patter, and as expected the oxygen demand correlates reasonably well with the temperature.« less

Water Quality Management of Keelung River, Northern Taiwan

The Keelung River is one of the major tributaries of the Tansui River in Northern Taiwan. It has been heavily polluted by municipal and industrial wastewater. Based on the anaerobic CBOD and DO models, nitrification in the Keelung River and flushing time of pollutants, the calibration and verification of water quality parameters were investigated and discussed. The results of sensitivity analysis showed that K1 is the most sensitive parameter and K2 is the least sensitive to DO values in non-tidal river reaches. For the tidal reaches, the analysis indicated that Kd and K2 have larger effects on the DO values and D1 has the least effect relatively. In order to meet the water quality standards of the Keelung River, a great amount of benthic oxygen demand should be removed in addition to the secondary treatment of all point sources at downstream reaches. From the analysis of the waste load allocation, it was found that the amount of removed waste will be underestimated due to the fact that the nitrification process in the Keelung River is ignored.

Benthic oxygen consumption on continental shelves off eastern Canada

The consumption of phytoplankton production by the benthos is an important component of organic carbon budgets for continental shelves. Sediment texture is a major factor regulating benthic processes because fine sediment areas are sites of enhanced deposition from the water column, resulting in increased organic content, bacterial biomass and community metabolism. Although continental shelves at mid- to high latitudes consist primarily of coarse relict sediments ( Piper, Continental Shelf Research, 11, 1013–1035), shelf regions of boreal and subarctic eastern Canada contain large areas of silt and clay sediments ( Fader, Continental Shelf Research, 11, 1123–1153). We collated estimates of benthic oxygen consumption in coarse (<20% silt-clay, <0.5% organic matter) and fine sediments (20% silt-clay, 0.5% organic matter) for northwest Atlantic continental shelves including new data for Georges Bank, the Scotian Shelf, the Grand Banks of Newfoundland and Labrador Shelf. Estimates were applied to the areal distribution of sediment type on these shelves to obtain a general relationship between sediment texture and benthic carbon consumption. Mean benthic oxygen demand was 2.7 times greater in fine sediment than in coarse sediment, when normalized to mean annual temperature. In terms of carbon equivalents, shelf regions with minimal fine sediment (Georges Bank, the Grand Banks of Newfoundland-northeast Newfoundland) consumed only 5–8% of annual primary production. Benthos of the Gulf of Maine (100% fine sediment) and the Scotian Shelf (35% fine sediment) utilized 16–19% of primary production. Although 32% of the Labrador Shelf area contained fine sediments, benthic consumption of pelagic production (8%) was apparently limited by low mean annual temperature (2°C). These results indicate that incorporation of sediment-specific oxygen uptake into shelf carbon budgets may increase estimates of benthic consumption by 50%. Furthermore, respiration and production by large macrofauna allow an even greater proportion of primary production to enter benthic pathways. Fine sediment areas (shelf basins or “depocenters”) are postulated to be sites of enhanced biological activity which must be considered in the modelling of shelf carbon budgets and the role of the benthos in demersal fisheries.

Experimental evaluation of pollution potential of anionic surfactants in the marine environment

A study of the influence of temperature and salinity on the biodegradation of a commercial anionic surfactant (LAS) in waters and sediments of the Bay of Cádiz (SW Spain) is reported. The assays were carried out using batch reactors, and the surfactant concentrations used were similar to those found in the urban effluents which discharge into the bay. Temperature was found to have a decisive effect on the degradation rate. At temperatures of 20–25°C, degradation exceeded 90% within less than 10 days of assay whereas at temperatures under 10°C, degradation scarcely took place (the percentage of degradation did not exceed 5% after 21 days of assay). Variation in salinity, particularly marked during wet seasons, disturbs the activity of bacterial flora and slows down biodegradation of surfactant. All this means that the pollution potential of urban waste containing detergents undergoes significant seasonal variation. The rate of surfactant degradation was remarkably accelerated in the presence of sediments, except in those tests where anoxic conditions were established. This occurs where there is high benthic oxygen demand from sediments containing high percentage of easily-biodegradable organic matter.

Oxygen Consumption and Dissolved Inorganic Nutrient Production in Marine Coastal and Shelf Sediments of the Middle Atlantic Bight

AbstractThe benthic oxygen demand and inorganic nutrient release have been investigated in the coastal zone of the Mid‐Atlantic Bight of the United States using in situ and ship‐board incubations to estimate fluxes across the sediment‐water interface. Oxygen demand ranged from ca. 70 ml m−2 hr−1 nearshore in warm (25°C) muddy sediments to ca. 4 ml m−2 hr−1 in cold (6°C), coarse‐grained sediments offshore. Ammonium ion flux was out of the sediments in all but 4 of 29 incubations, while nitrate was often found to be utilized within or on the sediments, decreasing in 10 of 29 incubations. Those locations with fluxes of nitrate out of the sediment had concentrations in the pore water that were generally high, sometimes up to several mM l−1. Nitrate fluxes were always well below those of ammonia, even where high almost equivalent concentrations of both NH4 and NO3 were found at the same locale.On George's Bank only 13 % of total N demand by the phytoplankton was estimated to be supplied by the benthos, whereas in New York Bight the supply amounted to 42 % of the demand. This difference can be attributed to higher pelagic biological and advective (mixing and upwelling) inputs to George's Bank compared to the relatively well stratified New York Bight in late summer and autumn.

Benthic oxygen demand in Lake Apopka, Florida

The benthic oxygen demand of Lake Apopka, Florida was determined using laboratory core uptake and flow through system techniques. The core-uptake for 5 stations in Lake Apopka averaged 67 mg O 2 m −2-h and partitioning experiments indicated that the oxygen uptake was primarily biological, with bacterial respiration dominating. No significant statistical correlations were found between core oxygen uptake rates and TKN levels ( r = 0.33), percent volatile solids ( r = 0.49), or macroinvertebrate densities ( r = 0.59). Sediment oxygen uptake rates ( D B ) were logarithmically related to flow rate in the following form D B = − A + B In flow. Flow-through system sediment oxygen uptake at each station approached similar maximum uptake rates of 130 mg O 2 m −2-h at high (> 200 l h −1) flow rates. Lake Apopka is an extremely shallow, wind mixed system and sediment uptake rates are expected to approximate this value during periods of intense wind mixing. The relatively low sediment uptake rates obtained for Lake Apopka, a hypereutrophic lake, supports the view that during eutrophication sediment respiration is progressively replaced by respiration in the water column.

Sediment Oxygen Demand and Nutrient Release

Benthic oxygen demand rates in rivers ranged from 0.10 gm/m to 5.30 gm/sq m/day and were found to increase linearly with dissolved oxygen concentrations in the water overlying the sediment deposits. The oxygen uptake was found to be more closely related to the nutrient composition of the interstitial water of the sediments than to the nutrient composition of the sediment solids. Ammonia nitrogen release rates ranged from an apparent net uptake of 44 mg/sq m/day to a release of 505 mg/m, whereas total dissolved phosphorus exchange rates varied from a net uptake of 13 mg/sq m/day to a release of 138 mg/sq m/day. The release of ammonia nitrogen was related to the nitrogen content of both the interstitial water and solids portions of the sediment and it appeared that biochemical mechanisms were principally responsible for ammonia nitrogen exchange processes. The exchange of total dissolved phosphorus was unrelated to measured nutrients within the sediments or overlying waters but was related to oxygen depletion, consistent with the widely accepted view that phosphorus exchange is controlled principally by oxidation-reduction reactions with iron, manganese, or sulfur, or all three.

An Ecophysiological Study of the Meiofauna of the Swartkops Estuary

Benthic oxygen demand was measured by dark and light bottle technique at two beaches in the Swartkops estuary, near Port Elizabeth. Respiration of nematodes was measured by polarographic micro-rcspirometer technique. Secondary production was 82 g C/m2/y in sandy areas and 863 g C/m2/y in muddy areas rich in the prawn Callianassa kraussi. Meiofauna production was 1,72 g C/m2/y in sand and 0,24 g C/m2/y in mud. The meiofauna] contribution to secondary production was 2,1% and 0,03% for these two areas respectively. The largest proportion of secondary production was due to micro-organisms: 92% in sand and 73,5% in mud. Macrofauna accounted for 5,75% and 24,4%. It is concluded that meiofauna in these exposed sand and mud flat areas is not quantitatively important, but the qualitative importance may be considerable.