Oxygen and organic matter thresholds for benthic faunal activity on the Pakistan margin oxygen minimum zone (700–1100m)

Levin, Lisa A.; Whitcraft, Christine R.; Mendoza, Guillermo; Gonzalez, Jennifer P.; Cowie, Gregory L.

doi:10.1016/j.dsr2.2008.05.032

Cited by 124 publications

(133 citation statements)

References 44 publications

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“…Aller, 2001). In shallow waters, interface and surface-deposit feeders are generally favored over subsurface-deposit feeders if bottomwater oxygen levels decline (Pearson and Rosenberg, 1978;Levin et al, 2009b). Particle mixing and bio-irrigation are consequently restricted to surface layers of sediment.…”

Section: Effect Of Oxygen On Macrobenthos and Consequences For Sedimementioning

confidence: 99%

Coastal hypoxia and sediment biogeochemistry

2009

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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 bottomwater 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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Section: Effect Of Oxygen On Macrobenthos and Consequences For Sedimementioning

confidence: 99%

Coastal hypoxia and sediment biogeochemistry

2009

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“…In the Arabian Sea investigations, oxygen has been shown to be an important factor limiting the density, body size and taxonomic groups of macrofauna found in OMZs. At OMZ margins in both the Pacific and Indian Oceans, macrofaunal species richness exhibits a positive correlation with bottom-water oxygen concentration, although organic carbon content exerts strong control on evenness and dominance (Levin and Gage, 1998;Levin et al, 2009;A. Raman, personal communication, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Worldwide, OMZs exhibit a high proportion of annelids and low representation of echinoderms with strong diversity shifts linked to oxygen gradients (e.g., Levin et al, 2009). Within the Indian Ocean, these patterns have been reported for the Oman (Levin et al, 2000) and Pakistan (Hughes et al, 2009;Levin et al, 2009) margins, as well as on the W. Indian margin Hunter et al, 2011Hunter et al, , 2012 and in the Bay of Bengal (Gooday et al, 2010;A. Raman, unpubl.).…”

Section: Introductionmentioning

confidence: 99%

Macrofaunal colonization across the Indian margin oxygen minimum zone

et al. 2013

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Abstract. There is a growing need to understand the ability of bathyal assemblages to recover from disturbance and oxygen stress, as human activities and expanding oxygen minimum zones increasingly affect deep continental margins. The effects of a pronounced oxygen minimum zone (OMZ) on slope benthic community structure have been studied on every major upwelling margin; however, little is known about the dynamics or resilience of these benthic populations. To examine the influence of oxygen and phytodetritus on shortterm settlement patterns, we conducted colonization experiments at 3 depths on the West Indian continental margin. Four colonization trays were deployed at each depth for 4 days at 542 and 802 m (transect 1-16 • 58 N) and for 9 days at 817 and 1147 m (transect 2-17 • 31 N). Oxygen concentrations ranged from 0.9 µM (0.02 mL L −1 ) at 542 m to 22 µM (0.5 mL L −1 ) at 1147 m. All trays contained local defaunated sediments; half of the trays at each depth also contained 13 C / 15 N-labeled phytodetritus mixed into the sediments. Sediment cores were collected between 535 m and 1140 m from 2 cross-margin transects for analysis of ambient (source) macrofaunal (> 300 µm) densities and composition. Ambient macrofaunal densities ranged from 0 ind m −2 (at 535-542 m) to 7400 ind m −2 , with maximum values on both transects at 700-800 m. Macrofaunal colonizer densities ranged from 0 ind m −2 at 542 m, where oxygen was lowest, to average values of 142 ind m −2 at 800 m, and 3074 ind m −2 at 1147 m, where oxygen concentration was highest. These were equal to 4.3 and 151 % of the ambient community at 800 m and 1147 m, respectively. Community structure of settlers showed no response to the presence of phytodetritus. Increasing depth and oxygen concentration, however, significantly influenced the community composition and abundance of colonizing macrofauna. Polychaetes constituted 92.4 % of the total colonizers, followed by crustaceans (4.2 %), mollusks (2.5 %), and echinoderms (0.8 %). The majority of colonizers were found at 1147 m; 88.5 % of these were Capitella sp., although they were rare in the ambient community. Colonists at 800 and 1147 m also included ampharetid, spionid, syllid, lumbrinerid, cirratulid, cossurid and sabellid polychaetes. Consumption of 13 C / 15 N-labeled phytodetritus was observed for macrofaunal foraminifera (too large to be colonizers) at the 542 and 802/817 m sites, and by metazoan macrofauna mainly at the deepest, better oxygenated sites. Calcareous foraminifera (Uvigerina, Hoeglundina sp.), capitellid polychaetes and cumaceans were among the major phytodetritus consumers. These preliminary experiments suggest that bottom-water oxygen concentrations may strongly influence ecosystem services on continental margins, as reflected in rates of colonization by benthos and colonizer processing of carbon following disturbance. They may also provide a window into future patterns of

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“…The system undergoes extreme change in oxygen regime over the course of a year: the shelf water column remains oxygenated from November to May and becomes suboxic/anoxic during July-October. Hypoxia (O 2 ≤ 62.5 µM; Levin et al, 2009) starts in June, followed by suboxia (denitrifying condition, O 2 ≤ 4.46 µM; see Naqvi et al, 2010, and references therein) during July-August and often by anoxia (sulfidic condition; Naqvi et al, 2010, and references therein) during September-October . However, anoxia (sulfidic condition) remains limited only to the nearshore region of the shelf and is not a regular occurrence (e.g., years 1997, 2000, 2003 and 2007).…”

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confidence: 99%

Benthic mineralization and nutrient exchange over the inner continental shelf of western India

et al. 2014

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Abstract. The western Indian continental shelf is one of the most productive coastal systems of the world ocean. This system experiences extreme changes in its oxygen regime, being normoxic from November to May and suboxic (denitrifying)/anoxic from June to October, owing to the biogeochemical response to cyclical monsoonal influence. In order to understand the impact of the seasonally varying oxygen regime on benthic mineralization, nutrient exchange and, in turn, on the shelf ecosystem, we carried out the first ever intact-core incubations during two contrasting seasons -spring intermonsoon and fall intermonsoon (late southwest monsoon) at a 28 m-deep fixed site on the inner shelf off Goa, dominated by fine-grained cohesive sediments. The results showed that incomplete sediment oxygen consumption (SOC) occurred during April as opposed to the complete SOC and subsequent sulfide flux observed in the fall intermonsoon incubations. The sediments acted as a perennial net source of DIN (dissolved inorganic nitrogen i.e. NO Slow oxidation of organic carbon (C org ) under anoxia, lower temperature and reduced benthic faunal activity appeared to decrease benthic mineralization by 25 % as suggested by the drop in the C org oxidation rate from 63.8 mmol C m −2 d −1 in April to 47.8 mmol C m −2 d −1 in October. This indicated a higher preservation of C org during the late southwest monsoon. Sediment porosity, C org content and nutrients did not show significant variations from April to October. Porewaters were found to be enriched with NH

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Oxygen and organic matter thresholds for benthic faunal activity on the Pakistan margin oxygen minimum zone (700–1100m)

Cited by 124 publications

References 44 publications

Coastal hypoxia and sediment biogeochemistry

Coastal hypoxia and sediment biogeochemistry

Macrofaunal colonization across the Indian margin oxygen minimum zone

Benthic mineralization and nutrient exchange over the inner continental shelf of western India

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