Export 3 results:
Sort by: Author Title Type [ Year  (Desc)]
Neira, C, Ingels J, Mendoza G, Hernandez-Lopez E, Levin LA.  2018.  Distribution of meiofauna in bathyal sediments influenced by the oxygen minimum zone off Costa Rica. Frontiers in Marine Science. 5   10.3389/fmars.2018.00448   AbstractWebsite

Ocean deoxygenation has become a topic of increasing concern because of its potential impacts on marine ecosystems, including oxygen minimum zone (OMZ) expansion and subsequent benthic effects. We investigated the influence of oxygen concentration and organic matter (OM) availability on metazoan meiofauna within and below an OMZ in bathyal sediments off Costa Rica, testing the hypothesis that oxygen and OM levels are reflected in meiofaunal community structures and distribution. Mean total densities in our sampling cores (400-1800 m water depth) were highest with 3688 ind. 10 cm(-2) at the OMZ core at 400 m water depth, decreasing rapidly downslope. Nematodes were overall dominant, with a maximum of 99.9% in the OMZ core, followed by copepods (13%), nauplii (4.8%), and polychaetes (3%). Relative copepod and nauplii abundance increased consistently with depth and increasing bottom-water O-2. Meiofaunal composition was significantly different among sites, with lower taxonomic diversity at OMZ sites relative to deeper, oxygenated sites. Vertical distribution patterns within sediments showed that in strongly oxygen-depleted sites less meiofauna was concentrated in the surface sediment than at deeper slope sites. Highest meiofaunal abundance and lowest diversity occurred under lowest oxygen and highest pigment levels, whereas highest diversity occurred under highest oxygen-concentrations and low pigments, as well as high quality of sedimentary pigment (chl a/phaeo) and organic carbon (C/N). The lower meiofaunal diversity, and lower structural and trophic complexity, at oxygen-depleted sites raises concerns about changes in the structure and function of benthic marine ecosystems in the face of OMZ expansions.

Levin, LA, Mengerink K, Gjerde KM, Rowden AA, Vandover CL, Clark MR, Ramirez-Llodra E, Currie B, Smith CR, Sato KN, Gallo N, Sweetman AK, Lily H, Armstrong CW, Brider J.  2016.  Defining "serious harm" to the marine environment in the context of deep-seabed mining. Marine Policy. 74:245-259.   10.1016/j.marpol.2016.09.032   AbstractWebsite

Increasing interest in deep-seabed mining has raised many questions surrounding its potential environmental impacts and how to assess the impacts' significance. Under the United Nations Convention on the Law of the Sea (UNCLOS), the International Seabed Authority (ISA) is charged with ensuring effective protection of the marine environment as part of its responsibilities for managing mining in seabed areas beyond national jurisdiction (the Area) on behalf of humankind. This paper examines the international legal context for protection of the marine environment and defining the significant adverse change that can cause "serious harm", a term used in the ISA Mining Code to indicate a level of harm that strong actions must be taken to avoid. It examines the thresholds and indicators that can reflect significant adverse change and considers the specific vulnerability of the four ecosystems associated with the minerals targeted for mining: (1) manganese (polymetallic) nodules, (2) seafloor massive (polymetallic) sulphides, (3) cobalt-rich (polymetallic) crusts and (4) phosphorites. The distributions and ecological setting, probable mining approaches and the potential environmental impacts of mining are examined for abyssal polymetallic nodule provinces, hydrothermal vents, seamounts and phosphorite-rich continental margins. Discussion focuses on the special features of the marine environment that affect the significance of the predicted environmental impacts and suggests actions that will advance understanding of these impacts.

Levin, LA, McCann LD, Thomas CL.  1991.  The ecology of polychaetes on deep seamounts in the eastern Pacific Ocean. Ophelia. :467-476. AbstractWebsite

Polychaetes were collected by the submersible ALVIN on 18 deep (788-3,353 m) seamounts in the eastern Pacific Ocean at 10-degrees, 13-degrees, 20-degrees and 30-degrees N off western Mexico. Polychaetes comprised 57.7% of all macrofauna collected. Average density over all locations was 942 polychaetes/m2. Thirty-eight families were represented among the 1,422 infaunal polychaetes collected. Five families, the Paraonidae, Cirratulidae, Syllidae, Ampharetidae, and Sabellidae, attained average densities > 1 individual/196 cm2 core. We evaluated effects of latitude, local setting, depth, and substrate on polychaete abundance, taxonomic composition, and lifestyles. Unusually high polychaete densities (7,194/m2) and low diversities were observed in a shallow caldera (788 m) at 13-degrees N. Excluding this site, the latitude exhibiting the highest polychaete densities (xBAR = 939/m2) was 10-degrees N. Of the seven settings examined, pit craters (within seamount calderas) supported the highest densities (xBAR = 1031/m2), and hydrothermal oxide fields and seamount bases exhibited the lowest polychaete densities (xBAR = 576-612/m2). Rippled foraminiferal sands on volcano summits supported large numbers of filter feeders, particularly sabellids. Regressions of total polychaete abundance on depth and on percent sand were not significant. Large, epifaunal, sediment-agglutinating protozoans (Phylum Sarcodina: Class Xenophyophorea) provided habitat for 34 polychaete species. Polychaete abundance and family composition were generally similar to those reported for other nearshore, deep-sea environments at comparable depths. With the exception of the shallowest site, species richness was typically high.