Vertical gradients of meiofauna and bacteria in subtidal sandy sediments from two high-energy surf zones in Algoa Bay, South Africa

Malan, D. E.; McLachlan, Anton

doi:10.2989/025776185784461117

Cited by 10 publications

(7 citation statements)

References 10 publications

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“…This zone is thus generally characterized by low faunal biomass (McLachlan 1977b(McLachlan , 1980 which increases sometimes dramatically landwards and more gradually seawards of this point. The biomass maxima for sublittoral meiofauna at the Namibian sites are within the range of values measured off other South African sandy beaches (Malan & McLachlan 1985).…”

Section: Nematode Feeding Typessupporting

confidence: 80%

Interstitial meiofauna of Namib sandy beaches

McGwynne¹,

Merwe²,

McLachlan³

1989

South African Journal of Zoology

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Section: Nematode Feeding Typessupporting

confidence: 80%

Interstitial meiofauna of Namib sandy beaches

McGwynne¹,

Merwe²,

McLachlan³

1989

South African Journal of Zoology

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“…Organic matter and subsieves (the fractlon passing through a 63 um sieve) average 2.2 "10 and 2.7 "/ o respectively. The pH and oxygen saturation decrease with depth into the sediment, but no anoxic conditions are encountered to a depth of 60 cm (the greatest depth sampled) (Malan & McLachlan 1985). These authors further showed that meiofaunal dry biomass averages 11 19 mg with nematodes dominating and harpacticoid copepod numbers being low.…”

Section: Methodsmentioning

confidence: 57%

“…Bacterial biomass averages 6197 mg m-' and increases in an offshore direction. More information on this beach may be found in McLachlan et al (1984) and Malan & McLachlan (1985).…”

Section: Methodsmentioning

confidence: 99%

“…Oxygen consumption during the very calm sampling periods averaged 9.4 + 6.1 m1 O2 m-' h-' compared to 16.0 + 2.8 m1 O2 m-'h-' during slightly rougher conditions. (Table 1) with oxygen penetrating to depths exceeding 60 cm (Malan & McLachlan 1985). There must therefore be considerable water exchange between the interstitial system and the overlying water.…”

Section: Oxygen Consumptionmentioning

confidence: 99%

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In situ benthic oxygen fluxes in a near-shore coastal marine system: a new approach to quantify the effect of wave action

Malan¹,

McLachlan²

1991

Mar. Ecol. Prog. Ser.

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A simple benthic chamber, with a flexible membrane to allow for wave-induced interstitial water flow, is described. The membrane has a low permeability to oxygen, compared to other materials previously employed in chamber studies. Polyethylene and latex rubber (condoms) are highly permeable to oxygen and clearly unsuitable for oxygen-related studies. Glass syringes tested for oxygen permeability were far superior to plastic syringes, the latter being completely inappropriate even in short-term studies. A study at Kings Beach. South Africa, using chambers with flexible membranes showed that oxygen consumption was significantly higher in chambers with flexible tops ( p <0.005) than in chambers with solid tops. The difference in the respective fluxes [18.5 2 2 7 (95 CI) compared to 10.7 f 4.6 m1 O2 m-2 h-'] was positively correlated with the effect of wave action at this medium energy exposed beach. Use of chambers with solid tops could result in underestimates in oxygen consumption of >50% at the study site. It is concluded that wave action, with its resultant interstitial water flow, can significantly affect the oxygen consun~ption of shallow water sediments.

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“…On sandy beaches, the meiofauna constitutes an important structural and functional component of the benthos (Malan & McLachlan 1985;McLachlan & Turner 1994;Kotwicki et al 2005): meiofauna can rival the macrofauna in terms of standing stocks in beach sediments, they contribute significantly to secondary production in these ecosystems, and they play a vital role in making small organic particles available to bacteria for mineralization and in optimizing conditions for microbial growth (Koop & Griffiths 1982).…”

Section: Introductionmentioning

confidence: 99%

Bottom‐up control in the benthos of ocean‐exposed sandy beaches?

Schlacher

Hartwig

2012

Austral Ecology

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Bottom-up control is a fundamental structuring force in food webs. Food webs of ocean-exposed sandy beaches are predicted to be bottom-up controlled systems, underpinned by imported organic matter rather than in situ primary production.This ecological model of resource-based regulation of biological assemblages is juxtaposed against a prevailing paradigm built around a dominance of physical drivers in sandy beach ecosystems. Surprisingly, given the apparently ubiquitous energetic subsidies of beach food webs, the central premise of bottom-up control has not been tested. Here we experimentally manipulated in situ nutrient levels on a sandy beach to test food web responses at the levels of primary producers (benthic microalgae) and their grazers (meiofauna). The meiofauna community as a whole appeared most strongly influenced by the local physical environment, particularly changes in sediment grain size -this supports the traditional 'environmental control paradigm'. We also detected a significant, positive response of two consumer groups of the meiofauna (nematodes, ostracods) to nutrient enrichment that supports a model of biological, bottom-up control. Although the predicted response of elevated producer biomass following nutrient enrichment was not detected, intense grazing pressure on new, stimulated production may have masked positive responses by the primary producers. Multichannel regulation of food webs is likely for many exposed sandy beaches, albeit an often lower importance of in situ bottom-up forces compared with stronger environmental control.

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Vertical gradients of meiofauna and bacteria in subtidal sandy sediments from two high-energy surf zones in Algoa Bay, South Africa

Cited by 10 publications

References 10 publications

Interstitial meiofauna of Namib sandy beaches

Interstitial meiofauna of Namib sandy beaches

In situ benthic oxygen fluxes in a near-shore coastal marine system: a new approach to quantify the effect of wave action

Bottom‐up control in the benthos of ocean‐exposed sandy beaches?

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