Publications

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Book Chapter
Blair, NE, Levin LA, Demaster DJ, Plaia G, Martin C, Fornes W, Thomas C, Pope R.  2001.  The biogeochemistry of carbon in continental slope sediments. Organism-sediment Interactions. ( Aller JY, Woodin S, Aller RC, Belle W. Baruch Institute for Marine Biology and Coastal Research. , Eds.).:243-262., Columbia: Published for the Belle W. Baruch Insitute for Marine Biology and Coastal Research by the University of South Carolina Press Abstract
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Grosholz, ED, Levin LA, Tyler C, Neira C.  2009.  Changes in community structure and ecosystem function following Spartina alterniflora invasion of Pacific estuaries. Human impacts on salt marshes : a global perspective. ( Silliman BR, Grosholz E, Bertness MD, Eds.).:23-40., Berkeley: University of California Press Abstract
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Springer, AE, Stevens LE, Anderson DE, Partnell RA, Kreamer DK, Levin LA, Flora S.  2008.  A comprehensive springs classification system. Integrating geomorphic, hydrogeochemical, and ecological criteria. Aridland springs in North America: ecology and conservation. ( Stevens LE, Meretsky VJ, Eds.).:49-75., Tucson: University of Arizona Press and the Arizona-Sonora Desert Museum Abstract
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Dibacco, C, Levin LA, Sala E.  2006.  Connectivity in marine systems: the importance of larval and spore dispersal. Connectivity Conservation. ( Crooks KR, Sanjayan A, Eds.).:157-183., Cambridge: Cambridge University Press Abstract
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Levin, LA, Gooday A.  2003.  The Deep Atlantic Ocean. Ecosystems of the deep oceans. ( Tyler PA, Ed.).:111-178., Amsterdam ; New York: Elsevier Abstract
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Levin, LA.  2005.  Ecology of cold seep sediments: Interactions of fauna with flow, chemistry and microbes. Oceanography and Marine Biology - an Annual Review, Vol. 43. 43( Gibson RN, Atkinson RJA, Gordon JDM, Eds.).:1-46., Boca Raton: Crc Press-Taylor & Francis Group Abstract

Cold seeps occur in geologically active and passive continental margins, where pore waters enriched in methane are forced upward through the sediments by pressure gradients. The advective supply of methane leads to dense microbial communities with high metabolic rates. Anaerobic methane oxidation presumably coupled to sulphate reduction facilitates formation of carbonates and, in many places, generates extremely high concentrations of hydrogen sulphide in pore waters. Increased food supply, availability of hard substratum and high concentrations of methane and sulphide supplied to free-living and symbiotic bacteria provide the basis for the complex ecosystems found at these sites. This review examines the structures of animal communities in seep sediments and how they are shaped by hydrologic, geochemical and microbial processes. The full size range of biota is addressed but emphasis is on the mid-size sediment-dwelling infauna (foraminiferans, metazoan meiofauna and macrofauna), which have received less attention than megafauna or microbes. Megafaunal biomass at seeps, which far exceeds that of surrounding non-seep sediments, is dominated by bivalves (mytilids, vesicomyids, lucinids and thyasirids) and vestimentiferan tube worms, with pogonophorans, cladorhizid sponges, gastropods and shrimp sometimes abundant. In contrast, seep sediments at shelf and upper slope depths have infaunal densities that often differ very little from those in ambient sediments. At greater depths, seep infauna exhibit enhanced densities, modified composition and reduced diversity relative to background sediments. Dorvilleid, hesionid and ampharetid polychaetes, nematodes, and calcareous foraminiferans are dominant. There is extensive spatial heterogeneity of microbes and higher organisms at seeps. Specialized infaunal communities are associated with different seep habitats (microbial mats, clam beds, mussel beds and tube worms aggregations) and with different vertical zones in the sediment. Whereas fluid flow and associated porewater properties, in particular sulphide concentration, appear to regulate the distribution, physiological adaptations and sometimes behaviour of many seep biota, sometimes the reverse is true. Animal-microbe interactions at seeps are complex and involve symbioses, heterotrophic nutrition, geochemical feedbacks and habitat structure. Nutrition of seep fauna varies, with thiotrophic and methanotrophic symbiotic bacteria fueling most of the megafaunal forms but macrofauna and most meiofauna are mainly heterotrophic. Macrofaunal food sources are largely photosynthesis-based at shallower seeps but reflect carbon fixation by chemosynthesis and considerable incorporation of methane-derived C at deeper seeps. Export of seep carbon appears to be highly localized based on limited studies in the Gulf of Mexico. Seep ecosystems remain one of the ocean's true frontiers. Seep sediments represent some of the most extreme marine conditions and offer unbounded opportunities for discovery in the realms of animal-microbe-geochemical interactions, physiology, trophic ecology, biogeography, systematics and evolution.

Gallo, ND, Levin LA.  2016.  Fish ecology and evolution in the world's oxygen minimum zones and implications of ocean deoxygenation. Advances in Marine Biology, Vol 74. 74( Curry BE, Ed.).:117-198., San Diego: Elsevier Academic Press Inc   10.1016/bs.amb.2016.04.001   Abstract

Oxygen minimum zones (OMZs) and oxygen limited zones (OLZs) are important oceanographic features in the Pacific, Atlantic, and Indian Ocean, and are characterized by hypoxic conditions that are physiologically challenging for demersal fish. Thickness, depth of the upper boundary, minimum oxygen levels, local temperatures, and diurnal, seasonal, and interannual oxycline variability differ regionally, with the thickest and shallowest OMZs occurring in the subtropics and tropics. Although most fish are not hypoxia-tolerant, at least 77 demersal fish species from 16 orders have evolved physiological, behavioural, and morphological adaptations that allow them to live under the severely hypoxic, hypercapnic, and at times sulphidic conditions found in OMZs. Tolerance to OMZ conditions has evolved multiple times in multiple groups with no single fish family or genus exploiting all OMZs globally. Severely hypoxic conditions in OMZs lead to decreased demersal fish diversity, but fish density trends are variable and dependent on region-specific thresholds. Some OMZ-adapted fish species are more hypoxiatolerant than most megafaunal invertebrates and are present even when most invertebrates are excluded. Expansions and contractions of OMZs in the past have affected fish evolution and diversity. Current patterns of ocean warming are leading to ocean deoxygenation, causing the expansion and shoaling of OMZs, which is expected to decrease demersal fish diversity and alter trophic pathways on affected margins. Habitat compression is expected for hypoxia-intolerant species, causing increased susceptibility to overfishing for fisheries species. Demersal fisheries are likely to be negatively impacted overall by the expansion of OMZs in a warming world.

Levin, LA, Plaia G, Huggett CL.  1994.  The influence of natural organic enhancement on life histories and community structure of bathyal polychaetes. Reproduction, larval biology, and recruitment of the deep-sea benthos. ( Young CM, Eckelbarger KJ, Eds.).:261-283., New York: Columbia University Press Abstract
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Levin, LA, Talley T.  2000.  Influences of vegetation and abiotic environmental factors on salt marsh benthos. Concepts and controversies in tidal marsh ecology. ( Weinstein M, Kreeger D, Eds.).:661-708., Dordrecht ; Boston: Kluwer Academic Abstract
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Levin, LA, Bridges TS.  1995.  Pattern and diversity in reproduction and development. Ecology of marine invertebrate larvae. ( McEdward LR, Ed.).:1-48., Boca Raton: CRC Press Abstract
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Levin, LA, Gooday AJ.  1992.  Possible roles for xenophyophores in deep-sea carbon cycling. Deep-sea food chains and the global carbon cycle. ( Rowe GT, Pariente V, Eds.).:93-104., Dordrecht ; Boston: Kluwer Academic Publishers Abstract
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Gooday, AJ, Levin LA, Linke P, Heeger T.  1992.  The role of benthic foraminifera in Deep-sea food webs and carbon cycling. Deep-sea food chains and the global carbon cycle. ( Rowe GT, Pariente V, Eds.).:63-91., Dordrecht ; Boston: Kluwer Academic Publishers Abstract
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Levin, LA, Nittrouer CA.  1987.  Textural characteristics of sediments on deep seamounts in the eastern Pacific Ocean between 10°N and 30°N. Seamounts, islands, and atolls. ( Keating BH, Fryer P, Batiza R, Boehlert GW, Eds.).:187-203., Washington, D.C.: American Geophysical Union Abstract
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Levin, LA, Sibuet M.  2012.  Understanding Continental Margin Biodiversity: A New Imperative. Annual Review of Marine Science, Vol 4. 4( Carlson CA, Giovannoni SJ, Eds.).:79-+., Palo Alto: Annual Reviews   10.1146/annurev-marine-120709-142714   Abstract

Until recently, the deep continental margins (200-4,000 m) were perceived as monotonous mud slopes of limited ecological or environmental concern. Progress in seafloor mapping and direct observation now reveals unexpected heterogeneity, with a mosaic of habitats and ecosystems linked to geomorphological, geochemical, and hydrographic features that influence biotic diversity. Interactions among water masses, terrestrial inputs, sediment diagenesis, and tectonic activity create a multitude of ecological settings supporting distinct communities that populate canyons and seamounts, high-stress oxygen minimum zones, and methane seeps, as well as vast reefs of cold corals and sponges. This high regional biodiversity is fundamental to the production of valuable fisheries, energy, and mineral resources, and performs critical ecological services (nutrient cycling, carbon sequestration, nursery and habitat support). It is under significant threat from climate change and human resource extraction activities. Serious actions are required to preserve the functions and services provided by the deep-sea settings we are just now getting to know.

Conference Proceedings
Tegner, MJ, Levin LA.  1982.  Do sea urchins and abalones compete in California kelp forest communities? Echinoderms, proceedings of the International Conference, Tampa Bay. ( Lawrence JM, Ed.).:265-271., RotterdamSalem, NH: A.A. Balkema ;Distributed in USA & Canada by MBS Abstract
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Levin, LA, Gage J, Lamont P, Cammidge L, Patience A, Martin C.  1997.  Infaunal community structure in a low-oxygen organic rich habitat on the Oman Continental Slope, NW Arabian Sea. The responses of marine organisms to their environments : Proceedings of the 30th European Marine Biology Symposium, University of Southampton, Southampton, United Kingdom. ( Hawkins LE, Hutchinson S, Jensen AC, Sheader M, Williams JA, Eds.).:223-230., Southampton: Southampton Oceanography Centre, University of Southampton Abstract
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Journal Article
Rice, SA, Levin LA.  1998.  Streblospio gynobranchiata, a new spionid polychaete species (Annelida : Polychaeta) from Florida and the Gulf of Mexico with an analysis of phylogenetic relationships within the genus Streblospio. Proceedings of the Biological Society of Washington. 111:694-707. AbstractWebsite

Streblospio gynobranchiata, a new species of spionid polychaete, is described from Florida and the Gulf of Mexico. This species is distinguished by the presence of strap-like branchiae, beneath which larvae are brooded, in the genital body region of the females. Data from experimental crosses conducted in the laboratory are presented that indicate incipient reproductive isolation between S. gynobranchiata from Florida and S. benedicti from North Carolina and California. The spermatophores produced by males of S. gynobranchiata and S. benedicti are described for the first time. Morphological, developmental, and reproductive characteristics are used in combination to construct a cladogram that suggests possible phylogenetic relationships between known species in the genus Streblospio.

Thornhill, DJ, Struck TH, Ebbe B, Lee RW, Mendoza GF, Levin LA, Halanych KM.  2012.  Adaptive radiation in extremophilic Dorvilleidae (Annelida): diversification of a single colonizer or multiple independent lineages? Ecology and Evolution. 2:1958-1970.   10.1002/ece3.314   AbstractWebsite

Metazoan inhabitants of extreme environments typically evolved from forms found in less extreme habitats. Understanding the prevalence with which animals move into and ultimately thrive in extreme environments is critical to elucidating how complex life adapts to extreme conditions. Methane seep sediments along the Oregon and California margins have low oxygen and very high hydrogen sulfide levels, rendering them inhospitable to many life forms. Nonetheless, several closely related lineages of dorvilleid annelids, including members of Ophryotrocha, Parougia, and Exallopus, thrive at these sites in association with bacterial mats and vesicomyid clam beds. These organisms are ideal for examining adaptive radiations in extreme environments. Did dorvilleid annelids invade these extreme environments once and then diversify? Alternatively, did multiple independent lineages adapt to seep conditions? To address these questions, we examined the evolutionary history of methane-seep dorvilleids using 16S and Cyt b genes in an ecological context. Our results indicate that dorvilleids invaded these extreme habitats at least four times, implying preadaptation to life at seeps. Additionally, we recovered considerably more dorvilleid diversity than is currently recognized. A total of 3 major clades (designated "Ophryotrocha,""Mixed Genera" and "Parougia") and 12 terminal lineages or species were encountered. Two of these lineages represented a known species, Parougia oregonensis, whereas the remaining 10 lineages were newly discovered species. Certain lineages exhibited affinity to geography, habitat, sediment depth, and/or diet, suggesting that dorvilleids at methane seeps radiated via specialization and resource partitioning.

Neira, C, Levin LA, Mendoza G, Zirino A.  2014.  Alteration of benthic communities associated with copper contamination linked to boat moorings. Marine Ecology-an Evolutionary Perspective. 35:46-66.   10.1111/maec.12054   AbstractWebsite

Although copper (Cu) is an essential element for life, leaching from boat paint can cause excess environmental loading in enclosed marinas. The effects of copper contamination on benthic macrofaunal communities were examined in three San Diego Bay marinas (America's Cup, Harbor Island West and East) in Southern California, USA. The distribution of Cu concentration in sediments exhibited a clear spatial gradient, with hotspots created by the presence of boats, which in two marinas exceeded the effect range medium (ERM). Elevated sediment Cu was associated with differences in benthic assemblages, reduced species richness and enhanced dominance in America's Cup and Harbor Island West, whereas Harbor Island East did not appear to be affected. At sites without boats there were greater abundances of some amphipods such as the species Desdimelita sp., Harpinia sp., Aoroides sp., Corophium sp., Podocerus sp., bivalves such as Lyonsia californica, Musculista senhousia, Macoma sp., and polychaetes such as Diplocirrus sp. In contrast, at sites with boats, densities of Pseudopolydora paucibranchiata, Polydora nuchalis, Euchone limnicola, Exogone lourei, Tubificoides spp. were enhanced. The limited impact on Harbor Island East suggests not only lower Cu input rates and increased water flushing and mixing, but also the presence of adequate defense mechanisms that regulate availability and mitigate toxic impacts. At all three marinas, Cu in tissues of several macrobenthic species exhibited Cu bioaccumulation above levels found in the surrounding environment. The annelids Lumbrineris sp. and Tubificoides spp., and the amphipod Desdimelita sp. contained high levels of Cu, suggesting they function as Cu bioaccumulators. The spionid polychaetes Polydora nuchalis and Pseudopolydora paucibranchiata had much lower Cu concentrations than surrounding sediments, suggesting they function as Cu bioregulators. The macrobenthic invertebrates in San Diego Bay marinas that tolerate Cu pollution (e.g. P.nuchalis, P.paucibranchiata, Euchone limnicola, Typosyllis sp., Tubificoides sp.) may function as indicators of high-Cu conditions, whereas the presence of Cu-sensitive species (e.g. Podocerus sp., Aoroides sp., Harpinia sp., Macoma sp., Lyonsia californica) may indicate healthier conditions (less Cu-stressed). Parallel responses by faunas of Shelter Island Yacht Basin, also in San Diego Bay, suggest potential for development of regional Cu contamination assessment criteria, and call for functional comparisons with other marinas and coastal water bodies.

Breitburg, DL, Salisbury J, Bernhard JM, Cai WJ, Dupont S, Doney SC, Kroeker KJ, Levin LA, Long WC, Milke LM, Miller SH, Phelan B, Passow U, Seibel BA, Todgham AE, Tarrant AM.  2015.  And on top of all that... Coping with ocean acidification in the midst of many stressors. Oceanography. 28:48-61.   10.5670/oceanog.2015.31   AbstractWebsite

Oceanic and coastal waters are acidifying due to processes dominated in the open ocean by increasing atmospheric CO2 and dominated in estuaries and some coastal waters by nutrient-fueled respiration. The patterns and severity of acidification, as well as its effects, are modified by the host of stressors related to human activities that also influence these habitats. Temperature, deoxygenation, and changes in food webs are particularly important co-stressors because they are pervasive, and both their causes and effects are often mechanistically linked to acidification. Development of a theoretical underpinning to multiple stressor research that considers physiological, ecological, and evolutionary perspectives is needed because testing all combinations of stressors and stressor intensities experimentally is impossible. Nevertheless, use of a wide variety of research approaches is a logical and promising strategy for improving understanding of acidification and its effects. Future research that focuses on spatial and temporal patterns of stressor interactions and on identifying mechanisms by which multiple stressors affect individuals, populations, and ecosystems is critical. It is also necessary to incorporate consideration of multiple stressors into management, mitigation, and adaptation to acidification and to increase public and policy recognition of the importance of addressing acidification in the context of the suite of other stressors with which it potentially interacts.

Moseman-Valtierra, S, Levin LA, Martin RM.  2016.  Anthropogenic impacts on nitrogen fixation rates between restored and natural Mediterranean salt marshes. Marine Ecology-an Evolutionary Perspective. 37:370-379.   10.1111/maec.12289   AbstractWebsite

To test the effects of site and successional stage on nitrogen fixation rates in salt marshes of the Venice Lagoon, Italy, acetylene reduction assays were performed with Salicornia veneta- and Spartina townsendii-vegetated sediments from three restored (6-14years) and two natural marshes. Average nitrogen fixation (acetylene reduction) rates ranged from 31 to 343 mu mol C2H4.m(-2.)h(-1) among all marshes, with the greatest average rates being from one natural marsh (Tezze Fonde). These high rates are up to six times greater than those reported from Southern California Spartina marshes of similar Mediterranean climate, but substantially lower than those found in moister climates of the Atlantic US coast. Nitrogen fixation rates did not consistently vary between natural and restored marshes within a site (Fossei Est, Tezze Fonde, Cenesa) but were negatively related to assayed plant biomass within the acetylene reduction samples collected among all marshes. Highest nitrogen fixation rates were found at Tezze Fonde, the location closest to the city of Venice, in both natural and restored marshes, suggesting possible site-specific impacts of anthropogenic stress on marsh succession.

Thurber, AR, Levin LA, Orphan VJ, Marlow JJ.  2012.  Archaea in metazoan diets: implications for food webs and biogeochemical cycling. ISME Journal. 6:1602-1612.   10.1038/ismej.2012.16   AbstractWebsite

Although the importance of trophic linkages, including 'top-down forcing', on energy flow and ecosystem productivity is recognized, the influence of metazoan grazing on Archaea and the biogeochemical processes that they mediate is unknown. Here, we test if: (1) Archaea provide a food source sufficient to allow metazoan fauna to complete their life cycle; (2) neutral lipid biomarkers (including crocetane) can be used to identify Archaea consumers; and (3) archaeal aggregates are a dietary source for methane seep metazoans. In the laboratory, we demonstrated that a dorvilleid polychaete, Ophryotrocha labronica, can complete its life cycle on two strains of Euryarchaeota with the same growth rate as when fed bacterial and eukaryotic food. Archaea were therefore confirmed as a digestible and nutritious food source sufficient to sustain metazoan populations. Both strains of Euryarchaeota used as food sources had unique lipids that were not incorporated into O. labronica tissues. At methane seeps, sulfate-reducing bacteria that form aggregations and live syntrophically with anaerobic-methane oxidizing Archaea contain isotopically and structurally unique fatty acids (FAs). These biomarkers were incorporated into tissues of an endolithofaunal dorvilleid polychaete species from Costa Rica (mean bulk delta C-13 = -92 +/- 4 parts per thousand; polar lipids -116 parts per thousand) documenting consumption of archaeal-bacterial aggregates. FA composition of additional soft-sediment methane seep species from Oregon and California provided evidence that consumption of archaeal-bacterial aggregates is widespread at methane seeps. This work is the first to show that Archaea are consumed by heterotrophic metazoans, a trophic process we coin as 'archivory'. The ISME Journal (2012) 6, 1602-1612; doi:10.1038/ismej.2012.16; published online 8 March 2012

Moy, LD, Levin LA.  1991.  Are Spartina marshes a replaceable resource? A functional approach to evaluation of marsh creation efforts Estuaries. 14:1-16.   10.2307/1351977   AbstractWebsite

Marsh creation has come into increasing use as a measure to mitigate loss of valuable wetlands. However, few programs have addressed the functional ecological equivalence of man-made marshes and their natural counterparts. This study addresses structural and functional interactions in a man-made and two natural marshes. This was done by integrating substrate characteristics and marsh utilization by organisms of two trophic levels. Sediment properties, infaunal community composition, and Fundulus heteroclitus marsh utilization were compared for a man-made Spartina salt marsh (between ages 1 to 3 yr) in Dills Creek, North Carolina, and adjacent natural marshes to the east and west. East natural marsh and planted marsh sediment grain-size distributions were more similar to each other than to the west natural marsh due to shared drainage systems, but sediment organic content of the planted marsh was much lower than in either natural marsh. This difference was reflected in macrofaunal composition. Natural marsh sediments were inhabited primarily by subsurface, deposit-feeding oligochaetes whereas planted marsh sediments were dominated by the tube-building, surface-deposit feeding polychaetes Streblospio benedicti and Manayunkia aestuarina. Infaunal differences were mirrored in Fundulus diets. Natural marsh diets contained more detritus and insects because oligochaetes, though abundant, were relatively inaccessible. Polychaetes and algae were major constituents of the planted marsh Fundulus diet. Though natural-marsh fish may acquire a potentially less nutritive, detritus-based diet relative to the higher animal protein diet of the planted marsh fish, Fundulus abundances were markedly lower in the planted marsh than in the natural marshes, indicating fewer fish were being supported. Lower Spartina stem densities in the planted marsh may have provided inadequate protection from predation or insufficient spawning sites for the fundulids. After three years, the planted marsh remained functionally distinct from the adjacent natural marshes. Mitigation success at Dills Creek could have been improved by increasing tidal flushing, thereby enhancing access to marine organisms and by mulching with Spartina wrack to increase sediment organic-matter content and porosity. Results from this study indicate that salt marshes should not be treated as a replaceable resource in the short term. The extreme spatial and temporal variability inherent to salt marshes make it virtually impossible to exactly replace a marsh by planting one on another site.

Davis, JLD, Levin LA, Walther SM.  2002.  Artificial armored shorelines: sites for open-coast species in a southern California bay. Marine Biology. 140:1249-1262.   10.1007/s00227-002-0779-8   AbstractWebsite

Artificial hard substrates have been used to stabilize naturally soft bay shorelines for centuries. Despite the loss of over half of the natural shoreline in many bays, little attention has been paid to the communities inhabiting armored shorelines and to the ecological implications of armoring. The goal of the present study was to examine factors affecting spatial and temporal variation of intertidal, hard-substrate biota (emergent species and fishes), with emphases on the influence of exposure, distance from the open ocean, and similarity to open-coast, hard-substrate communities. We examined community composition at eight San Diego Bay (California, USA) sites (an exposed and a protected site at four bay locations) in June and November 2000 and two open-coast sites in August 2000. At all bay sites, the shore was armored with granite boulders, a form of shoreline stabilization referred to as "riprap." Community structure was more variable spatially than temporally on the scales we studied, affected more by distance from the bay mouth and exposure to wave energy than by differences between June and November. Exposed sites near the bay mouth were more similar to natural open-coast sites, sharing about 45% of their species, than protected sites and sites farther from the mouth, which shared as few as 8%. Species richness was generally higher in exposed than protected bay sites. Species tended to occur higher in the intertidal zone at exposed than protected sites, and higher in November, when sea level was higher, than in June. Such results will be useful to shoreline managers who examine the ecological implications of hardening long stretches of coastline and may suggest ways to incorporate artificial structures into ecosystems in a more meaningful way.

Cowie, GL, Levin LA.  2009.  Benthic biological and biogeochemical patterns and processes across an oxygen minimum zone (Pakistan margin, NE Arabian Sea). Deep-Sea Research Part Ii-Topical Studies in Oceanography. 56:261-270.   10.1016/j.dsr2.2008.10.001   AbstractWebsite

Oxygen minimum zones (OMZs) impinging on continental margins present sharp gradients ideal for testing environmental factors thought to influence C cycling and other benthic processes, and for identifying the roles that biota play in these processes. Here we introduce the objectives and initial results of a multinational research program designed to address the influences of water depth, the OMZ (similar to 150-1300 m), and organic matter (OM) availability on benthic communities and processes across the Pakistan Margin of the Arabian Sea. Hydrologic, sediment, and faunal characterizations were combined with in-situ and shipboard experiments to quantify and compare biogeochemical processes and fluxes, OM burial efficiency, and the contributions of benthic communities, across the OMZ. In this introductory paper, we briefly review previous related work in the Arabian Sea, building the rationale for integrative biogeochemical and ecological process studies. This is followed by a summary of individual volume contributions and a brief synthesis of results. Five primary stations were studied, at 140, 300, 940,1200 and 1850 m water depth, with sampling in March-May (intermonsoon) and August-October (late-to-postmonsoon) 2003. Taken together, the contributed papers demonstrate distinct cross-margin gradients, not only in oxygenation and sediment OM content, but in benthic community structure and function, including microbial processes, the extent of bioturbation, and faunal roles in C cycling. Hydrographic studies demonstrated changes in the intensity and extent of the OMZ during the SW monsoon, with a shoaling of the upper OMZ boundary that engulfed the previously oxygenated 140-m site. Oxygen profiling and microbial process rate determinations demonstrated dramatic differences in oxygen penetration and consumption across the margin, and in the relative importance of anaerobic processes, but surprisingly little seasonal change. A broad maximum in sediment OM content occurred on the upper slope, roughly coincident with the OMZ; but the otherwise poor correlation with bottom-water oxygen concentrations indicated that other factors are important in determining sediment OM distributions. Downcore profiles generally showed little clear evidence of in-situ OM alteration, and there was little sign of OM enrichment resulting from the southwest monsoon in sediments collected in the late-to-postmonsoon sampling. This is interpreted to be due to rapid cycling of labile OM. Organic geochemical studies confirmed that sediment OM is overwhelmingly of marine origin across the margin, but also that it is heavily altered, with only small changes in degradation state across the OMZ. More negative stable C isotopic compositions in surficial sediments at hypoxic sites within the OMZ core are attributed to a chemosynthetic bacterial imprint. Dramatic changes in benthic community structure occurred across the lower OMZ transition, apparently related to OM availability and quality as well as to DO concentrations. High-resolution sampling, biomarkers and isotope tracer studies revealed that oxygen availability appears to exert threshold-type controls on benthic community structure and early faunal C processing. Biomarker studies also provided evidence of faunal influence on sediment OM composition. Together, the results offer strong evidence that benthic fauna at sites across the margin play important roles in the early cycling of sediment OM through differential feeding and bioturbation activities. (C) 2008 Published by Elsevier Ltd.