Effects of natural and human-induced hypoxia on coastal benthos

Abstract

Abstract. Coastal hypoxia (defined here as <1.42 ml L −1 ; 62.5 µM; 2 mg L −1 , approx. 30% oxygen saturation) develops seasonally in many estuaries, fjords, and along open coasts as a result of natural upwelling or from anthropogenic eutrophication induced by riverine nutrient inputs. Permanent hypoxia occurs naturally in some isolated seas and marine basins as well as in open slope oxygen minimum zones. Responses of benthos to hypoxia depend on the duration, predictability, and intensity of oxygen depletion and on whether H 2 S is formed. Under suboxic conditions, large mats of filamentous sulfide oxidizing bacteria cover the seabed and consume sulfide. They are hypothesized to provide a detoxified microhabitat for eukaryotic benthic communities. Calcareous foraminiferans and nematodes are particularly tolerant of low oxygen concentrations and may attain high densities and dominance, often in association with microbial mats. When oxygen is sufficient to support metazoans, small, soft-bodied invertebrates (typically annelids), often with short generation times and elaborate branchial structures, predominate. Large taxa are more sensitive than small taxa to hypoxia. Crustaceans and echinoderms are typically more sensitive to hypoxia, with lower oxygen thresholds, than annelids, sipunculans, molluscs and cnidarians.

Benthic Invertebrate Community Composition and Sediment Properties in Barnegat Bay, New Jersey, 1965−2014

“…The community structure of benthic macroinvertebrates is often used to assess habitat quality and to monitor the effects of human and natural stresses on marine and estuarine ecosystems (Borja, Dauer, and Grémare, 2012;Ellis et al, 2015;Grall and Glémarec, 1997;Hale, Cicchetti, and Deacutis, 2016;Levin et al, 2009). There are several reasons for that.…”

Genome and physiology of a model Epsilonproteobacterium responsible for sulfide detoxification in marine oxygen depletion zones

“…Hydrogen sulfide toxicity has been shown to be responsible for the severe mortality of marine organisms (6), the deterioration of coastal ecosystems, and drastic reductions in secondary production (5, 7), leading to "dead zones" in the ocean (5,6). Indeed, coastal dead zones have become an important environmental issue, as they pose a serious threat to benthic fauna and fishery-based economies (5,7).…”

Sedimentary phosphorus dynamics and the evolution of bottom‐water hypoxia: A coupled benthic–pelagic model of a coastal system

“…The onset of hypoxia alters nutrient cycling (Vahtera et al 2007) and is detrimental to benthic ecosystems, potentially reducing biodiversity due to mortality of species unable to tolerate low-oxygen or sulphidic conditions, thus altering community composition and function (Levin et al 2009). Proliferation of nearshore hypoxia is associated with enhanced nutrient inputs due to human activities, such as agricultural use of fertilizers and sewage discharge.…”