• Characterization of methane-seep communities in a deep-sea area designated for oil and natural gas exploitation off Trinidad and Tobago

      Amon, Diva; Gobin, J; Van Dover, CL; Levin, LA; Marsh, L; Raineault, NA (Frontiers, 2017-10-30)
      Exploration of the deep ocean (>200 m) is taking on added importance as human development encroaches. Despite increasing oil and natural gas exploration and exploitation, the deep ocean of Trinidad and Tobago is almost entirely unknown. The only scientific team to image the deep seafloor within the Trinidad and Tobago Exclusive Economic Zone was from IFREMER in the 1980s. That exploration led to the discovery of the El Pilar methane seeps and associated chemosynthetic communities on the accretionary prism to the east of Trinidad and Tobago. In 2014, the E/V Nautilus, in collaboration with local scientists, visited two previously sampled as well as two unexplored areas of the El Pilar site between 998 and 1,629 m depth using remotely operated vehicles. Eighty-three megafaunal morphospecies from extensive chemosynthetic communities surrounding active methane seepage were observed at four sites. These communities were dominated by megafaunal invertebrates including mussels (Bathymodiolus childressi), shrimp (Alvinocaris cf. muricola), Lamellibrachia sp. 2 tubeworms, and Pachycara caribbaeum. Adjacent to areas of active seepage was an ecotone of suspension feeders including Haplosclerida sponges, stylasterids and Neovermilia serpulids on authigenic carbonates. Beyond this were large Bathymodiolus shell middens. Finally there was either a zone of sparse octocorals and other non-chemosynthetic species likely benefiting from the carbonate substratum and enriched production within the seep habitat, or sedimented inactive areas. This paper highlights these ecologically significant areas and increases the knowledge of the biodiversity of the Trinidad and Tobago deep ocean. Because methane seepage and chemosynthetic communities are related to the presence of extractable oil and gas resources, development of best practices for the conservation of biodiversity in Trinidad and Tobago waters within the context of energy extraction is critical. Potential impacts on benthic communities during oil and gas activities will likely be long lasting and include physical disturbance during drilling among others. Recommendations for the stewardship of these widespread habitats include: (1) seeking international cooperation; (2) holding wider stakeholder discussions; (3) adopting stringent environmental regulations; and (4) increasing deep-sea research to gather crucial baseline data in order to conduct appropriate marine spatial planning with the creation of marine protected areas.
    • Environmental impacts of the deep-water oil and gas industry: a review to guide management strategies

      Cordes, EE; Jones, DOB; Schlacher, TA; Amon, Diva; Bernardino, AF; Brooke, S; Carney, R; DeLeo, DM; Dunlop, KM; Escobar-Briones, EG; et al. (Frontiers, 2016-09-16)
      The industrialization of the deep sea is expanding worldwide. Increasing oil and gas exploration activities in the absence of sufficient baseline data in deep-sea ecosystems has made environmental management challenging. Here, we review the types of activities that are associated with global offshore oil and gas development in water depths over 200 m, the typical impacts of these activities, some of the more extreme impacts of accidental oil and gas releases, and the current state of management in the major regions of offshore industrial activity including 18 exclusive economic zones. Direct impacts of infrastructure installation, including sediment resuspension and burial by seafloor anchors and pipelines, are typically restricted to a radius of ~100 m on from the installation on the seafloor. Discharges of water-based and low-toxicity oil-based drilling muds and produced water can extend over 2 km, while the ecological impacts at the population and community levels on the seafloor are most commonly on the order of 200–300 m from their source. These impacts may persist in the deep sea for many years and likely longer for its more fragile ecosystems, such as cold-water corals. This synthesis of information provides the basis for a series of recommendations for the management of offshore oil and gas development. An effective management strategy, aimed at minimizing risk of significant environmental harm, will typically encompass regulations of the activity itself (e.g., discharge practices, materials used), combined with spatial (e.g., avoidance rules and marine protected areas), and temporal measures (e.g., restricted activities during peak reproductive periods). Spatial management measures that encompass representatives of all of the regional deep-sea community types is important in this context. Implementation of these management strategies should consider minimum buffer zones to displace industrial activity beyond the range of typical impacts: at least 2 km from any discharge points and surface infrastructure and 200 m from seafloor infrastructure with no expected discharges. Although managing natural resources is, arguably, more challenging in deep-water environments, inclusion of these proven conservation tools contributes to robust environmental management strategies for oil and gas extraction in the deep sea.
    • From the Surface to the Deep-Sea: Bacterial Distributions across Polymetallic Nodule Fields in the Clarion-Clipperton Zone of the Pacific Ocean

      Lindh, MV; Maillot, BM; Shulse, CN; Gooday, AJ; Amon, Diva; Smith, CR; Church, MJ (Frontiers, 2017-09-08)
      Marine bacteria regulate fluxes of matter and energy essential for pelagic and benthic organisms and may also be involved in the formation and maintenance of commercially valuable abyssal polymetallic nodules. Future mining of these nodule fields is predicted to have substantial effects on biodiversity and physicochemical conditions in mined areas. Yet, the identity and distributions of bacterial populations in deep-sea sediments and associated polymetallic nodules has received relatively little attention. We examined bacterial communities using high-throughput sequencing of bacterial 16S rRNA gene fragments from samples collected in the water column, sediment, and polymetallic nodules in the Pacific Ocean (bottom depth ≥4,000 m) in the eastern Clarion-Clipperton Zone. Operational taxonomic units (OTUs; defined at 99% 16S rRNA gene identity) affiliated with JTB255 (Gammaproteobacteria) and Rhodospirillaceae (Alphaproteobacteria) had higher relative abundances in the nodule and sediment habitats compared to the water column. Rhodobiaceae family and Vibrio OTUs had higher relative abundance in nodule samples, but were less abundant in sediment and water column samples. Bacterial communities in sediments and associated with nodules were generally similar; however, 5,861 and 6,827 OTUs found in the water column were retrieved from sediment and nodule habitats, respectively. Cyanobacterial OTUs clustering among Prochlorococcus and Synechococcus were detected in both sediments and nodules, with greater representation among nodule samples. Such results suggest that vertical export of typically abundant photic-zone microbes may be an important process in delivery of water column microorganisms to abyssal habitats, potentially influencing the structure and function of communities in polymetallic nodule fields.
    • Habitat Configuration Alters Herbivory across the Tropical Seascape

      Swindells, KL; Murdoch, RJ; Bazen, WD; Harman, NW; Unsworth, RKF (Frontiers, 2017-02-28)
      There exists increasing evidence that top-down ecological processes such as herbivory are key in controlling marine ecosystems and their community structure. Herbivory has the potential to be altered by numerous environmental and ecological factors that operate at a variety of temporal and spatial scales, one such spatial factor is the influence of the marine landscape. We know little about how ecological processes such as herbivory change throughout the marine landscape and how the effects of these processes cascade. This is because most landscape scale studies observe species richness and abundance patterns. In terrestrial systems the landscape is well documented to influence ecological processes, but empirical evidence of this is limited in marine systems. In tropical seagrass meadows direct herbivory by parrotfish can be readily observed due to the clear hemispherical bite marks they leave on the seagrass. As with herbivory in other systems, this leaf consumption is thought to assist with leaf turnover, positively influencing leaf growth. Changes in its rate and extent are therefore likely to influence the characteristics of the plant. The faunal communities of seagrass meadows alter with respect to changes in the landscape, particularly with respect to connectivity to adjacent habitats. It might therefore be expected that a key ecological process such as herbivory will change with respect to habitat configuration and have cascading impacts upon the status of the seagrass. In the present study we examined indirect evidence of parrotfish grazing throughout the marine landscape and assessed this relative to plant condition. Seagrasses in locations of close proximity to mangroves were found to have double the amount of parrotfish grazing than sites away from mangroves. Evidence of herbivory was also found to be strongly and significantly negatively correlated to the abundance of plant attached epicover. The decreased epicover in the presence of elevated herbivory suggests increased leaf turnover. These results indicate that seagrass may have higher levels of ecosystem resilience in the presence of mangroves. Our research highlights how ecological processes can change throughout the marine landscape with cascade impacts on the resilience of the system.