Publications

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2018
Dunn, DC, Vandover CL, Etter RJ, Smith CR, Levin LA, Morato T, Colaco A, Dale AC, Gebruk AV, Gjerde KM, Halpin PN, Howell KL, Johnson D, Perez JAA, Ribeiro MC, Stuckas H, Weaver P, Participants SW.  2018.  A strategy for the conservation of biodiversity on mid-ocean ridges from deep-sea mining. Science Advances. 4   10.1126/sciadv.aar4313   AbstractWebsite

Mineral exploitation has spread from land to shallow coastal waters and is now planned for the offshore, deep seabed. Large seafloor areas are being approved for exploration for seafloor mineral deposits, creating an urgent need for regional environmental management plans. Networks of areas where mining and mining impacts are prohibited are key elements of these plans. We adapt marine reserve design principles to the distinctive biophysical environment of mid-ocean ridges, offer a framework for design and evaluation of these networks to support conservation of benthic ecosystems on mid-ocean ridges, and introduce projected climate-induced changes in the deep sea to the evaluation of reserve design. We enumerate a suite of metrics to measure network performance against conservation targets and network design criteria promulgated by the Convention on Biological Diversity. We apply these metrics to network scenarios on the northern and equatorial Mid-Atlantic Ridge, where contractors are exploring for seafloor massive sulfide (SMS) deposits. A latitudinally distributed network of areas performs well at (i) capturing ecologically important areas and 30 to 50% of the spreading ridge areas, (ii) replicating representative areas, (iii) maintaining along-ridge population connectivity, and (iv) protecting areas potentially less affected by climate-related changes. Critically, the network design is adaptive, allowing for refinement based on new knowledge and the location of mining sites, provided that design principles and conservation targets are maintained. This framework can be applied along the global mid-ocean ridge system as a precautionary measure to protect biodiversity and ecosystem function from impacts of SMS mining.

2014
Zapata-Hernandez, G, Sellanes J, Thurber AR, Levin LA.  2014.  Trophic structure of the bathyal benthos at an area with evidence of methane seep activity off southern Chile (similar to 45 degrees S). Journal of the Marine Biological Association of the United Kingdom. 94:659-669.   10.1017/s0025315413001914   AbstractWebsite

Through application of carbon (C) and nitrogen (N) stable isotope analyses, we investigated the benthic trophic structure of the upper-slope off southern Chile (similar to 45 degrees S) including a recent methane seep area discovered as part of this study. The observed fauna comprised 53 invertebrates and seven fish taxa, including remains of chemosymbiotic fauna (e.g. chemosymbiotic bivalves and siboglinid polychaetes), which are typical of methane seep environments. While in close-proximity to a seep, the heterotrophic fauna had a nutrition derived predominantly from photosynthetic sources (delta C-13 > -21 parts per thousand). The absence of chemosynthesis-based nutrition in the consumers was likely a result of using an Agassiz trawl to sample the benthos, a method that is likely to collect a mix of fauna including individuals from adjacent non-seep bathyal environments. While four trophic levels were estimated for invertebrates, the fish assemblage was positioned within the third trophic level of the food web. Differences in corrected standard ellipse area (SEA(C)), which is a proxy of the isotopic niche width, yielded differences for the demersal fish Notophycis marginata (SEA(C) = 5.1 parts per thousand) and Coelorinchus fasciatus (SEA(C) = 1.1 parts per thousand), suggesting distinct trophic behaviours. No ontogenic changes were detected in C. fasciatus regarding food sources and trophic position. The present study contributes the first basic trophic data for the bathyal area off southern Chile, including the identification of a new methane seep area, among the furthest south ever discovered. Such information provides the basis for the proper sustainable management of the benthic environments present along the vast Chilean continental margin.

2012
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.

2000
Gooday, AJ, Bernhard JM, Levin LA, Suhr SB.  2000.  Foraminifera in the Arabian Sea oxygen minimum zone and other oxygen-deficient settings: taxonomic composition, diversity, and relation to metazoan faunas. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 47:25-54.   10.1016/s0967-0645(99)00099-5   AbstractWebsite

Previous work has shown that some foraminiferal species thrive in organically enriched, oxygen-depleted environments. Here, we compare 'live' (stained) faunas in multicorer samples (0-1 cm layer) obtained at two sites on the Oman margin, one located at 412m within the oxygen minimum zone (OMZ) (O(2) = 0.13 ml l(-1)), the other located at 3350 m, well below the main OMZ (O(2) similar to 3.00 ml l(-1)). While earlier studies have focused on the hard-shelled (predominantly calcareous) foraminifera, we consider complete stained assemblages, including poorly known, soft-shelled, monothalamous forms. Densities at the 412-m site were much higher (16,107 individuals.10 cm(-2) in the > 63-mu m fraction) than at the 3350-m site (625 indiv.10 cm(-2)). Species richness (E(S(100))), diversity (H', Fishers Alpha index) and evenness (J') were much lower, and dominance (R1D) was higher, at 412 m compared with 3350 m. At 412 m, small calcareous foraminifera predominated and soft-shelled allogromiids and sacamminids were a minor faunal element. At 3350 m, calcareous individuals were much less common and allogromiids and saccamminids formed a substantial component of the fauna. There were also strong contrasts between the foraminiferal macrofauna( > 300-mu m fraction) at these two sites; relatively small species of Bathysiphon, Globobulimina and Lagenammina dominated at 412 m, very large, tubular, agglutinated species of Bathysiphon, Hyperammina, Rhabdammina and Saccorhiza were important at 3350 m. Our observations suggest that, because they contain fewer soft-shelled and agglutinated foraminifera, a smaller proportion of bathyal, low-oxygen faunas is lost during fossilization compared to faunas from well-oxygenated environments. Trends among foraminifera (> 63 mu m fraction) in the Santa Barbara Basin (590 and 610m depth; O(2) = 0.05 and 0.15 ml(-1) respectively), and macrofaunal foraminifera(> 300 mu m) on the Peru margin (300-1250 m depth: O(2) = 0.02-1.60 mi l(-1)), matched those observed on the Oman margin. Tn particular, soft-shelled monothalamous taxa were rare and large agglutinated taxa were absent in the most oxygen-depleted ( < 0.20 mi l(-1)) stations. Foraminifera often outnumber metazoans (both meiofaunal and macrofaunal) in bathyal oxygen-depleted settings. However, although phylogenetically distant, foraminifera and metazoans exhibit similar population responses to oxygen depletion; species diversity decreases, dominance increases, and the relative abundance of the major taxa changes. The foraminiferal macrofauna ( > 300 mu m) were 5 times more abundant than the metazoan macrofauna at 412 m on the Oman margin but 16 times more abundant at the 3350 m site. Among the meiofauna (63-300 mu m), the trend was reversed, foraminifera were 17 times more abundant than metazoan taxa at 412 m but only 1.4 times more abundant at 3350 In. An abundance of food combined with oxygen levels which are not depressed sufficiently to eliminate the more tolerant taxa, probably explains why foraminifera and macrofaunal metazoans flourished at the 412-m site, perhaps to the detriment of the metazoan meiofauna. (C) 1999 Elsevier Science Ltd. All rights reserved.