Effects of different submersed macrophytes on sediment biogeochemistry

ABSTRACT Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3 − reduction from denitrification to dissimilatory NO3 − reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H2S with NO3 − and transported S0 to the sediment surface for aerobic oxidation.

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Coastal hypoxia and sediment biogeochemistry

Biogeosciences ◽

10.5194/bg-6-1273-2009 ◽

2009 ◽

Vol 6 (7) ◽

pp. 1273-1293 ◽

Cited By ~ 339

Author(s):

J. J. Middelburg ◽

L. A. Levin

Keyword(s):

Organic Matter ◽

Bottom Water ◽

Water Exchange ◽

Transport Processes ◽

Ecosystem Dynamics ◽

Ecosystem Functions ◽

Oxygen Levels ◽

Concise Review ◽

Water Oxygen ◽

Sediment Biogeochemistry

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal-induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

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Organic contaminants in submersed macrophytes drifting in the Detroit River

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f97-150 ◽

1997 ◽

Vol 54 (10) ◽

pp. 2417-2427 ◽

Cited By ~ 6

Author(s):

J Lovett-Doust ◽

L Lovett-Doust ◽

M Biernacki ◽

T K Mal ◽

R Lazar

Keyword(s):

Organic Contaminants ◽

Dry Mass ◽

Terrestrial Plants ◽

Plant Debris ◽

Western Basin ◽

Submersed Macrophytes ◽

Detroit River ◽

Significant Burden ◽

Aquatic Food ◽

Time Of Year

Macrophytes drifting in the Detroit River were sampled and analysed for contaminants at monthly intervals from September 1990 to September 1991. Twelve species of submersed macrophytes were identified, as well as algae and leaves of terrestrial plants. Drifting plant debris was greatest in August-September, when Potamogeton spp. and Najas sp. predominated. Over the study period, a total of 60.57 times 106 kg fresh mass (3.0285 times 106 kg ash-free dry mass) of plant debris drifted out of Lake St. Clair into the Detroit River annually. Organochlorine content differed between plant taxa and according to the time of year. Annual contaminant burden of the Detroit River by upriver contributions was carried mostly by Potamogeton spp. and Najas sp. Total annual load of organochlorines in drifting plant debris was estimated to be 155 g, including 124 g of PCBs. These bioavailable contaminants may enter the detrital compartment of aquatic food webs, following plant senescence, or may be taken up directly by herbivores. Contaminants associated with plant debris drifting from Lake St. Clair and the Detroit River contribute a significant burden of bioavailable organic contaminants to the western basin of Lake Erie.

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