Differential response of benthic macrofauna and meiofauna to hypoxia in the Gullmar Fjord basin

Josefson, Alf B.; Widbom, Bertil

doi:10.1007/bf00392952

Cited by 181 publications

(106 citation statements)

References 30 publications

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“…Previous studies have reported that abundance peaks coincide with lower oxygen concentrations for macrofauna than for megafauna (Thomsen et al, 1985;Wishner et al, 1995;Levin 2002). Such patterns are consistent with the generally greater tolerance to hypoxia of foraminiferans than metazoan macrofauna, which in turn are more tolerant than megafauna (Josefson & Widbom, 1988;Moodley et al, 1997;Levin 2003) The rapid changes in megafaunal community composition across the lower transition zone, noted above, are probably another expression of an edge effect. Some macrofaunal species also had narrow ranges on the Pakistan and Oman margins, for example, the polychaete Linopherus sp.…”

Section: Edge Effectssupporting

confidence: 64%

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Faunal responses to oxygen gradients on the Pakistan margin: A comparison of foraminiferans, macrofauna and megafauna

Gooday

Levin

Silva

et al. 2009

Deep Sea Research Part II: Topical Studies in Oceanography

143

103

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The Pakistan margin is characterized by a strong midwater oxygen minimum zone (OMZ) that intercepts the seabed at bathyal depths (150 to 1300 m). We investigated whether faunal abundance and diversity trends were similar among protists (foraminiferans and gromiids), metazoan macrofauna and megafauna along a transect (140-1850 m water depth) across the OMZ during the 2003 intermonsoon (March-May) and late/post monsoon (August-October) seasons. All groups exhibited some drop in abundance in the OMZ core (250-500 m water depth; O 2 : 0.10-0.13 ml l -1 = 4.46-5.80 μM l -1 ) but to differing degrees. Densities of foraminiferans >63 µm were slightly depressed at 300 m, peaked at 738 m, and were much lower at deeper stations. Foraminiferans >300 µm were the overwhelmingly dominant macrofaunal organisms in the OMZ core.Macrofaunal metazoans reached maximum densities at 140 m depth, with additional peaks at 850, 940 and 1850 m where foraminiferans were less abundant. The polychaete Linopherus sp. was responsible for a macrofaunal biomass peak at 950 m. Apart from large swimming animals (fish and natant decapods), metazoan megafauna were absent between 300 and 900 m (O 2 <0.14-0.15 ml l -1 = 6.25-6.69 μM l -1 ) but were represented by a huge, ophiuroid-dominated abundance peak at 1000 m (O 2 ~0.15-0.18 ml l -1 = 6.69-8.03μM l -1 ). Gromiid protists were confined largely to depths below 1150 m (O 2 >0.2 ml l -1 = 8.92 μM l -1 ). The progressively deeper abundance peaks for foraminiferans (>63 µm), Linopherus sp. and ophiuroids probably represent lower OMZ boundary edge effects and suggest a link between body size and tolerance of hypoxia. Macro-and megafaunal organisms collected between 800 and 1100 m were dominated by a succession of different taxa, indicating that the lower part of the OMZ is also a region of rapid faunal change. Species diversity was depressed in all groups in the OMZ core, but this was much more pronounced for macrofauna and megafauna than for foraminiferans. Oxygen levels strongly influenced the taxonomic composition of all faunal groups. Calcareous foraminiferans dominated the seasonally and permanently hypoxic sites (136-300 m); agglutinated foraminiferans were relatively more abundant at deeper stations where oxygen concentrations were >0.13 ml l -1 (= 5.80 μM l -1 ). Polychaetes were the main macrofaunal taxon within the OMZ; calcareous macrofauna and megafauna (decapods, 3 echinoderms) were rare or absent where oxygen levels were lowest. The rarity of larger animals between 300 and 700 m on the Pakistan margin, compared with the abundant macrofauna in the OMZ core off Oman, is the most notable contrast between the two sides of the Arabian Sea. This difference probably reflects the slightly higher oxygen levels and better food quality on the western side.

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Section: Edge Effectssupporting

confidence: 64%

“…Field and experimental evidence suggests that foraminiferans and metazoan meiofauna generally tolerate hypoxia better than larger metazoans (Josefson & Widbom, 1988;Moodley et al 1997). Foraminiferans were the overwhelmingly dominant eukaryotic group among those analysed in the core of the Pakistan margin OMZ.…”

Section: Protists (Foraminiferans and Gromiids)mentioning

confidence: 96%

Faunal responses to oxygen gradients on the Pakistan margin: A comparison of foraminiferans, macrofauna and megafauna

Gooday

Levin

Silva

et al. 2009

Deep Sea Research Part II: Topical Studies in Oceanography

143

103

View full text Add to dashboard Cite

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“…The intensity of these processes was considered to differ under wellmixed and stratified conditions. When lasting for long enough periods, anoxia may completely eradicate the larger benthic animals (e.g., Rabalais et al, 2002), and it may take years before significant populations of macrofauna return (Josefson & Widbom, 1988). In contrast, smaller organisms are less affected and may recover more rapidly upon restoration of oxic conditions (Josefson & Widbom, 1988).…”

Section: Sediment Parametersmentioning

confidence: 99%

“…When lasting for long enough periods, anoxia may completely eradicate the larger benthic animals (e.g., Rabalais et al, 2002), and it may take years before significant populations of macrofauna return (Josefson & Widbom, 1988). In contrast, smaller organisms are less affected and may recover more rapidly upon restoration of oxic conditions (Josefson & Widbom, 1988). As larger animals contribute most to bioturbation and bio-irrigation, anoxia also affects the degree to which the sediments are mixed or to which water is pumped in the sediment.…”

Section: Sediment Parametersmentioning

confidence: 99%

Modeling eutrophication and oligotrophication of shallow-water marine systems: the importance of sediments under stratified and well-mixed conditions

Soetaert

Middelburg

2009

Eutrophication in Coastal Ecosystems

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A one-dimensional model that couples water-column physics with pelagic and benthic biogeochemistry in a 50-m-deep water column is used to demonstrate the importance of the sediment in the functioning of shallow systems, the eutrophication status of the system, and the system's resilience to oligotrophication. Two physical scenarios, a well-mixed and a stratified water column, are considered and both are run along a gradient of increasing initial pelagic-dissolved inorganic nitrogen (DIN) concentration. Where the mixed layer extends to the bottom, more nutrients and less light are available for growth. Under low to moderately eutrophic conditions (pelagic DIN \30 mmol m -3 ), this leads to higher productivity in well-mixed waters, while the stratified system is more productive under highly eutrophic conditions. Under stratification, the build-up of nitrate and depletion of oxygen below the mixed layer does not notably change the functioning of the sediment as a sink for reactive nitrogen. In sediments underlying well-mixed waters, sedimentary denitrification, fueled mainly by in situ nitrification, is slightly more important (8-15% of total benthic mineralization) than under stratified waters (7-20%), where the influx of bottom-water nitrate is the most important nitrate source. As a consequence of this less efficient removal of reactive nitrogen, the winter DIN concentrations are higher in the stratified scenario. The model is used to estimate the long-term benefits of nutrient reduction scenarios and the timeframe under which the new steady-state condition is approached. It is shown that a 50% reduction in external nitrogen inputs ultimately results in a reduction of 60-70% of the original pelagic DIN concentration. However, as the efflux of nitrogen from the sediment compensates part of the losses in the water column, system oligotrophication is a slow process: after 20 years of reduced inputs, the pelagic DIN concentrations still remain 2.7 mmol m -3 (mixed) and 3.9 mmol m -3 (stratified) above the ultimate DIN concentrations.

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“…The deep water in the fjord is generally exchanged once annually, but low oxygen concentrations occur in some years because of limited or no water exchange. The benthic community reduction and recovery at Alsbäck in relation to changing oxygen conditions have been studied by Josefson and Widbom (1988), Nilsson and Rosenberg (2000) and Rosenberg et al (2002). The available material includes fauna and bottom water oxygen concentration time series over 31 years (1977Fig.4g).…”

Section: Temporal Gradients Following Oxygen Depletion Events In a Dementioning

confidence: 99%

Assessment of marine benthic quality change in gradients of disturbance

2009

TemaNord

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Differential response of benthic macrofauna and meiofauna to hypoxia in the Gullmar Fjord basin

Cited by 181 publications

References 30 publications

Faunal responses to oxygen gradients on the Pakistan margin: A comparison of foraminiferans, macrofauna and megafauna

Faunal responses to oxygen gradients on the Pakistan margin: A comparison of foraminiferans, macrofauna and megafauna

Modeling eutrophication and oligotrophication of shallow-water marine systems: the importance of sediments under stratified and well-mixed conditions

Assessment of marine benthic quality change in gradients of disturbance

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