Cindy Lee Van Dover

Man and the Last Great Wilderness: Human Impact on the Deep Sea

The deep sea, the largest ecosystem on Earth and one of the least studied, harbours high biodiversity and provides a wealth of resources. Although humans have used the oceans for millennia, technological developments now allow exploitation of fisheries resources, hydrocarbons and minerals below 2000 m depth. The remoteness of the deep seafloor has promoted the disposal of residues and litter. Ocean acidification and climate change now bring a new dimension of global effects. Thus the challenges facing the deep sea are large and accelerating, providing a new imperative for the science community, industry and national and international organizations to work together to develop successful exploitation management and conservation of the deep-sea ecosystem. This paper provides scientific expert judgement and a semi-quantitative analysis of past, present and future impacts of human-related activities on global deep-sea habitats within three categories: disposal, exploitation and climate change. The analysis is the result of a Census of Marine Life – SYNDEEP workshop (September 2008). A detailed review of known impacts and their effects is provided. The analysis shows how, in recent decades, the most significant anthropogenic activities that affect the deep sea have evolved from mainly disposal (past) to exploitation (present). We predict that from now and into the future, increases in atmospheric CO2 and facets and consequences of climate change will have the most impact on deep-sea habitats and their fauna. Synergies between different anthropogenic pressures and associated effects are discussed, indicating that most synergies are related to increased atmospheric CO2 and climate change effects. We identify deep-sea ecosystems we believe are at higher risk from human impacts in the near future: benthic communities on sedimentary upper slopes, cold-water corals, canyon benthic communities and seamount pelagic and benthic communities. We finalise this review with a short discussion on protection and management methods.

Ecology of Mid-Atlantic Ridge hydrothermal vents

Abstract In the past year, the number of explored deep-water vent sites on the Mid-Atlantic Ridge has doubled. The fauna of Atlantic vents consists for the most part of a subset of invertebrate types found elsewhere in chemosynthetic ecosystems, with taxonomic differentiation usually at the species or genus level. Despite this similarity in taxonomic composition, the ecology of Atlantic vents differs from the ecology of Pacific vents in ways that highlight aspects of biogeography, trophic ecology and sensory adaptations.

Hydrothermal vent fields and chemosynthetic biota on the world's deepest seafloor spreading centre.

The Mid-Cayman spreading centre is an ultraslow-spreading ridge in the Caribbean Sea. Its extreme depth and geographic isolation from other mid-ocean ridges offer insights into the effects of pressure on hydrothermal venting, and the biogeography of vent fauna. Here we report the discovery of two hydrothermal vent fields on the Mid-Cayman spreading centre. The Von Damm Vent Field is located on the upper slopes of an oceanic core complex at a depth of 2,300 m. High-temperature venting in this off-axis setting suggests that the global incidence of vent fields may be underestimated. At a depth of 4,960 m on the Mid-Cayman spreading centre axis, the Beebe Vent Field emits copper-enriched fluids and a buoyant plume that rises 1,100 m, consistent with >400 °C venting from the worlds deepest known hydrothermal system. At both sites, a new morphospecies of alvinocaridid shrimp dominates faunal assemblages, which exhibit similarities to those of Mid-Atlantic vents.

Novel Forms of Structural Integration between Microbes and a Hydrothermal Vent Gastropod from the Indian Ocean

ABSTRACT Here we describe novel forms of structural integration between endo- and episymbiotic microbes and an unusual new species of snail from hydrothermal vents in the Indian Ocean. The snail houses a dense population of γ-proteobacteria within the cells of its greatly enlarged esophageal gland. This tissue setting differs from that of all other vent mollusks, which harbor sulfur-oxidizing endosymbionts in their gills. The significantly reduced digestive tract, the isotopic signatures of the snail tissues, and the presence of internal bacteria suggest a dependence on chemoautotrophy for nutrition. Most notably, this snail is unique in having a dense coat of mineralized scales covering the sides of its foot, a feature seen in no other living metazoan. The scales are coated with iron sulfides (pyrite and greigite) and heavily colonized by ε- and δ-proteobacteria, likely participating in mineralization of the sclerites. This novel metazoan-microbial collaboration illustrates the great potential of organismal adaptation in chemically and physically challenging deep-sea environments.

A Call for Deep-Ocean Stewardship

The precautionary approach and collaborative governance must balance deep-ocean use and protection. Covering more than half the planet, the deep ocean sequesters atmospheric CO2 and recycles major nutrients; is predicted to hold millions of yet-to-be-described species; and stores mind-boggling quantities of untapped energy resources, precious metals, and minerals (1). It is an immense, remote biome, critical to the health of the planet and human well-being. The deep ocean (defined here as below a typical continental shelf break, >200 m) faces mounting challenges as technological advances—including robotics, imaging, and structural engineering—greatly improve access. We recommend a move from a frontier mentality of exploitation and single-sector management to a precautionary system that balances use of living marine resources, energy, and minerals from the deep ocean with maintenance of a productive and healthy marine environment, while improving knowledge and collaboration.

Impacts of anthropogenic disturbances at deep-sea hydrothermal vent ecosystems: A review

Deep-sea hydrothermal-vent ecosystems have stimulated decades of scientific research and hold promise of mineral and genetic resources that also serve societal needs. Some endemic taxa thrive only in vent environments, and vent-associated organisms are adapted to a variety of natural disturbances, from tidal variations to earthquakes and volcanic eruptions. In this paper, physicochemical and biological impacts of a range of human activities at vents are considered. Mining is currently the only anthropogenic activity projected to have a major impact on vent ecosystems, albeit at a local scale, based on our current understanding of ecological responses to disturbance. Natural recovery from a single mining event depends on immigration and larval recruitment and colonization; understanding processes and dynamics influencing life-history stages may be a key to effective minimization and mitigation of mining impacts. Cumulative impacts on benthic communities of several mining projects in a single region, without proper management, include possible species extinctions and shifts in community structure and function.

Understanding the biogeography of chemosynthetic ecosystems

Abstract ChEss is a recently-funded Census of marine life programme aimed at improving our knowledge of the biogeography of deepwater chemosynthetically driven ecosystems by promoting an international field phase of discovery and exploration. The main objectives are to assess and explain the diversity, distribution and abundance of hydrothermal vent and cold seep species. With the global mid-ocean ridge system extending ∼65 000 km, it is unlikely that its entire length would be examined in detail. The ChEss programme proposes to select a limited number of target areas chosen for the discovery of new vents and seeps. The intention is to identify the maximum scientific return that could be achieved from detailed investigation of the minimum number of sites at key locations. To narrow the field for exploration, a number of starting hypotheses and goals have been identified. A bio- and geo-referenced database for hydrothermal vent and cold seep species will be created. This database will be integrated with the Ocean Biogeographic Information System (OBIS). An international scientific committee will coordinate the programme, facilitate collaboration between participants, promote ship-time applications at national level and stimulate scientific innovation from a wider community.

Recruitment of marine invertebrates to hard substrates at deep-sea hydrothermal vents on the East Pacific Rise and Galapagos spreading center

Abstract Recruitment panels were placed at and near hydrothermal vent communities at three sites on the Galapagos spreading center and one site on the East Pacific Rise at 21°N. Deployment periods ranged from 26 days (Clam Acres, 21°N) to 260–320 days (Rose Garden, Garden of Eden, Mussel Bed, GSC) to 1216 days (Clam Acres). Recruitment of gastropod post-larvae and juveniles was observed on arrays deployed at Clam Acres for 26 days. Regardless of length of deployment, populations of polychaetes, mollusks, and barnacles colonizing the panels were predominantly post-larval, juvenile, or sub-adult stages. We suggest that some combination of competition, migration, and predation maintains these populations in immature stages. Size distributions of individuals within a taxon on panels deployed for 1216 days are broad, suggesting intermittent or continuous recruitment in many of the vent-associated species rather than a single episodic recruitment event. Folliculinid and foraminiferan protozoans were the most abundant eucaryotic organisms colonizing long-term deployments at Clam Acres. On the Galapagos spreading center, level of recruitment differed among the vent sites, with Rose Garden > Garden of Eden ⪢ Mussel Bed. Recruitment of vent-associated species was greater on panels placed within vent communities compared to panels placed adjacent to these communities. This observation is consistent with the maintenance of vent communities in discrete regions of hydrothermal flux.

Characterization of Symbiont Populations in Life-History Stages of Mussels From Chemosynthetic Environments

The densities of chemoautotrophic and methanotrophic symbiont morphotypes were determined in life- history stages (post-larvae, juveniles, adults) of two species of mussels (Bathymodiolus azoricus and B. heckerae) from deep-sea chemosynthetic environments (the Lucky Strike hydrothermal vent and the Blake Ridge cold seep) in the Atlantic Ocean. Both symbiont morphotypes were observed in all specimens and in the same relative proportions, regardless of life-history stage. The relative abundance of symbiont morphotypes, determined by transmission electron microscopy, was different in the two species: chemoautotrophs were dominant (13:1–18:1) in B. azoricus from the vent site; methanotrophs were dominant (2:1–3:1) in B. heckerae from the seep site. The ratio of CH4:H2S is proposed as a determinant of the relative abundance of symbiont types: where CH4:H2S is less than 1, as at the Lucky Strike site, chemoautotrophic symbionts dominate; where CH4:H2S is greater than 2, as at the seep site, methanotrophs dominate. Organic carbon and nitrogen isotopic compositions of B. azoricus (δ13C = −30‰; δ15N = −9‰) and B. heckerae (δ13C = −56‰; δ15N = −2‰) varied little among life-history stages and provided no record of a larval diet of photosynthetically derived organic material in the post-larval and juvenile stages.

Light at deep-sea hydrothermal vents

Ambient light spectral data were acquired at two deep-sea hydrothermal vents with a temperature of ∼350°C: the Hole-to-Hell site on the East Pacific Rise at 9°N and the Snake-Pit site on the Mid-Atlantic Ridge. Measurements were made with a simple, multi-channel photometer which simultaneously detected light in four 100 nm-wide bands over the wavelength range of 650–1050 nm. Most of the light detected is near-infrared (750–1050 nm), but there is a 19x greater photon flux than expected from thermal radiation alone at shorter wavelengths (650–750 nm) at the Hole-to-Hell vent. At Snake Pit, more light in the 750–850 nm band was observed 10 cm above the orifice where the temperature was 50–100°C than at the 351°C vent opening. These data suggest the presence of non-thermal light sources in the vent environment. Some possible non-thermal mechanisms are identified, but further data will be required to resolve them.