A scaling approach to spatial variability in early diagenetic processes

Morse, John W.; DiMarco, Steven F.; Hebert, Andrew B.; Sell, Karen S.

doi:10.1007/978-94-017-3366-3_5

Cited by 4 publications

(4 citation statements)

References 2 publications

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“…The use of a 2‐D approach on a relatively small scale (1 cm) allowed for the detection of these ‘hot spots’ that would not have been identified by conventional whole‐core incubation techniques. Many studies have suggested that sampling resolution, modelling and methodology can play an important role, not only in the detection of microniches, but also in the evaluation and prediction of the distribution and diversity of microbial communities and microenvironments within sediments (Blomqvist, 1991; Brendel and Luther, 1995; Morse et al ., 2003; Zorn et al ., 2006; Stockdale et al ., 2009). However, there haven been relatively few studies on the importance of sedimentary microniches for the biogeochemical processes in benthic ecosystems.…”

Section: Discussionmentioning

confidence: 99%

Bioturbation and the role of microniches for sulfate reduction in coastal marine sediments

Bertics

Ziebis

2010

Environmental Microbiology

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The effects of bioturbation in marine sediments are mainly associated with an increase in oxic and oxidized zones through an influx of oxygen-rich water deeper into the sediment and the rapid transport of particles between oxic and anoxic conditions. However, macrofaunal activity also can increase the occurrence of reduced microniches and anaerobic processes, such as sulfate reduction. Our goal was to determine the two-dimensional distribution of microniches associated with burrows of a ghost shrimp (Neotrypaea californiensis) and to determine microbial activities. In laboratory experiments, detailed measurements of sulfate reduction rates (SRR) were measured by injecting, in a 1 cm grid, radiolabelled sulfate directly into a narrow aquarium (40 cm × 30 cm × 3 cm) containing the complex burrow of an actively burrowing shrimp. Light-coloured oxidized burrow walls, along with black reduced microniches, were clearly visible through the aquarium walls. Direct injection of radiotracers allowed for whole-aquarium incubation to obtain two-dimensional documentation of sulfate reduction. Results indicated SRR were up to three orders of magnitude higher (140-790 nmol SO(4) (2-) cm(-3) day(-1) ) in reduced microniches associated with burrows when compared with the surrounding sediment. Additionally, some of the subsurface sulfate-reducing microniches associated with the burrow system appeared to be zones of dinitrogen fixation. Bioturbation may also lead to decreased sulfate reduction in other microniches and the sum of the activity in all microniches might not result in a total increase of sulfate reduction compared with non-bioturbated control sediments.

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Section: Discussionmentioning

confidence: 99%

Bioturbation and the role of microniches for sulfate reduction in coastal marine sediments

Bertics

Ziebis

2010

Environmental Microbiology

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“…Figure 2 shows an image obtained by slicing a resin embedded sediment core, in which both grain scale and microenvironment features are evident. Scaling issues relevant to early diagenetic processes are examined further by Morse et al (2003). Aller (1982;2001) has reviewed and assessed the roles and significance of burrowing, tube construction, irrigation and faecal pellet microenvironments, introduced by macrobenthos.…”

Section: Introductionmentioning

confidence: 99%

Micro-scale biogeochemical heterogeneity in sediments: A review of available technology and observed evidence

Stockdale

Davison

Zhang

2009

Earth-Science Reviews

219

147

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The hypothesis that reducing conditions exist in localized zones of high organic matter, termed microniches, was first suggested over a century ago, but only relatively recently have high-resolution techniques been available to investigate them. In any sediment containing benthic fauna, bioturbation affects the distribution of a number of redox-sensitive components. Direct faecal deposition and the death of fauna may be expected to cause particles of labile organic matter (microniches) to be distributed heterogeneously within the sediment. This review discusses the significance and future direction of microniche studies by considering, exclusively, data obtained on a sub-mm scale that provide significant evidence for the existence and properties of microniches. Microelectrodes and planar optodes have shown the significant effect of burrowing organisms on localized O 2 distributions and revealed distinct depletions in O 2 due to microniches. Localized increases in pCO 2 and decreases in pH measured by optodes were attributed to elevated activity at microniches. Diffusive gradients in thin-films have shown isolated supersaturation of metals and sulphide, providing evidence for possible simultaneous oxidation of organic matter by sulphate and iron oxides. The stochastic nature of these data and the lack of information for the same precise location hinders interpretation in terms of sediment diagenesis. If microniches are known to account for a significant proportion of organic matter degradation, re-examination of the current understanding of sedimentary diagenesis may be needed. Further investigation on the distribution and frequency of microniches is required, including a wider range of analytes, in order to estimate their cumulative effect on element diagenesis, immobilisation/remobilisation processes and ultimately pollutant fate.

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“…It also causes heterogeneous ecological niches with scales ranging from micro-to hectometres. When studying such heterogeneous environments, the observational scale has to be chosen as a function of the scale of the studied ecological niche variability (Wu et al, 2000;Morse et al, 2003;Martiny et al, 2006;Wu and Li, 2006). This is a fundamental prerequisite to further identify potential parameters controlling the heterogeneity of the niches.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional distribution of living benthic foraminifera in anoxic sediment layers of an estuarine mudflat (Loire estuary, France)

et al. 2015

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Abstract. We present a new rapid and accurate protocol to simultaneously sample benthic living foraminifera in two dimensions in a centimetre-scale vertical grid and dissolved iron and phosphorus in two dimensions at high resolution (200 μm). Such an approach appears crucial for the study of foraminiferal ecology in highly dynamic and heterogeneous sedimentary systems, where dissolved iron shows a strong variability at the centimetre scale. On the studied intertidal mudflat of the Loire estuary, foraminiferal faunas are dominated by Ammonia tepida, which accounts for 92 % of the living (CellTracker Green(CTG)-labelled) assemblage. The vertical distribution shows a maximum density in the oxygenated 0–0.4 cm surface layer. A sharp decrease is observed in the next 2 cm, followed by a second, well-defined maximum in the suboxic sediment layer (3–8 cm depth). The presented method yields new information concerning the 2-D distribution of living A. tepida in suboxic layers. First, the identification of recent burrows by visual observation of the sediment cross section and the burrowing activity as deduced from the dissolved iron spatial distribution show no direct relation to the distribution of A. tepida at the centimetre scale. This lack of relation appears contradictory to previous studies (Aller and Aller, 1986; Berkeley et al., 2007). Next, the heterogeneity of A. tepida in the 3–8 cm depth layer was quantified by means of Moran's index to identify the scale of parameters controlling the A. tepida distribution. The results reveal horizontal patches with a characteristic length of 1–2 cm. These patches correspond to areas enriched in dissolved iron likely generated by anaerobic degradation of labile organic matter. These results suggest that the routine application of our new sampling strategy could yield important new insights about foraminiferal life strategies, improving our understanding of the role of these organisms in coastal marine ecosystems.

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A scaling approach to spatial variability in early diagenetic processes

Cited by 4 publications

References 2 publications

Bioturbation and the role of microniches for sulfate reduction in coastal marine sediments

Bioturbation and the role of microniches for sulfate reduction in coastal marine sediments

Micro-scale biogeochemical heterogeneity in sediments: A review of available technology and observed evidence

Two-dimensional distribution of living benthic foraminifera in anoxic sediment layers of an estuarine mudflat (Loire estuary, France)

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