Keywords: 6145 0 S 11100 0 E Deep-sea benthic biology Megafauna Hydrocarbon seep Chemosynthetic environment Remotely operated vehicle Seafloor geology Habitat heterogeneity a b s t r a c t Release of hydrocarbons from sediments is important in increasing habitat heterogeneity on deep ocean margins. Heterogeneity arises from variation in abiotic and biotic conditions, including changes in substratum, geochemistry, fluid flow, biological communities and ecological interactions. The seepage of heavy hydrocarbons to the seafloor is less well studied than most other cold seep systems and may lead to the formation of asphalt mounds. These have been described from several regions, particularly the Gulf of Mexico. Here, we describe the structure, potential formation and biology of a large asphalt mound province in Block 31SE Angola. A total of 2254 distinct mound features was identified by side-scan sonar, covering a total area of 3.7 km 2 of seafloor. The asphalt mounds took a number of forms from small (o0.5 m diameter; 13% observations) mounds to large extensive (o50 m diameter) structures. Some of the observed mounds were associated with authigenic carbonate and active seepage (living chemosynthetic fauna present in addition to the asphalt). The asphalt mounds are seabed accumulations of heavy hydrocarbons formed from subsurface migration and fractionation of reservoir hydrocarbons primarily through a network of faults. In Angola these processes are controlled by subsurface movement of salt structures. The asphalt mounds were typically densely covered with epifauna (74.5% of mounds imaged had visible epifauna) although individual mounds varied considerably in epifaunal coverage. Of the 49 non-chemosynthetic megafaunal taxa observed, 19 taxa were only found on hard substrata (including asphalt mounds), 2 fish species inhabited the asphalt mounds preferentially and 27 taxa were apparently normal soft-sediment fauna. Antipatharians (3.672.3% s.e.) and poriferans (2.671.9% s.e.) accounted for the highest mean percentage of the observed cover, with actinarians (0.970.4% s.e.) and alcyonaceans (0.470.2% s.e.) covering smaller proportions of the area. Asphalt mounds represent a common and important habitat on several margin systems globally and should be recognised in future environmental assessment and management of these areas.

As human activities continue to move further offshore (Bett 2001;Glover and Smith 2003), they come into contact with deep-sea environments and populations that are often not well understood. Deep-ocean basins cover more than 60% of the Earth's surface, yet much of the deep-sea remains unexplored. Recent efforts have been made to address the historical under-sampling of the deep sea by establishing long-term seafloor observatories, some autonomous and some connected to shore stations via electro-optical cables. Here we describe the first results from two long-term autonomous observatory platforms used to study deep-sea ecology in the vicinity of oil and gas industry activity in the Atlantic Ocean offshore of Angola. AbstractThe DELOS (Deep-ocean Environmental Long-term Observatory System) project is a long-term research program focused on understanding the impacts of oil and gas extraction on deep-sea ecosystems. We have installed two seafloor observation platforms, populated with ROV-serviced sensor modules, at 1400 m water depth in the Southeast Atlantic off the coast of Angola. The 'impact' Near-Field platform is located 50 m from subsea oil production facilities. The 'control' Far-Field platform is 16 km distant from any industry seafloor activity. Each platform includes oceanographic, acoustic, and camera sensor modules. The latter carries two still cameras providing close-up and wide-angle views of the seabed. The Far-Field platform is also equipped with a sediment trap that deploys to 100 m above the seafloor. The instrumented platforms were installed in Feb 2009, and the sensor modules subsequently serviced in Aug 2009, Feb 2010, and Aug 2010. Here, we report on our first experiences of operating the observatories and present some of the first data. The oceanographic data (temperature, salinity, oxygen concentration) and biological observations (demersal fish and benthic invertebrates) suggest that the two study sites have near identical environmental characteristics. We, therefore, believe that these sites are appropriate as control and impact locations for long-term monitoring of potential anthropogenic effects referenced to natural background environmental variation. We suggest that DELOS-type observatories, particularly operated as pairs (or in networks), are a highly effective means of appropriately monitoring deep-water resource exploitation-both hydrocarbon extraction and mineral mining.

Deepwater represents a significant proportion of future oil and gas exploration and production. Scientists have however stated that the deepwater environment is less well understood than the dark side of the moon. At the same time there is increasing pressure from NGOs to postpone deepwater exploration until more is known about potential impacts. In partnership with the marine science community, and via capacity building in Angola, BP has developed and installed the world's first Deepwater Environmental Long-term Observatory System (DELOS) off the coast of Angola. Two environmental monitoring stations were installed, one in the near field and one in the far field 16 kms distant from, and upstream of, any infrastructure. These subsea platforms will be in place for around 25 years and, for the first time ever, will provide scientifically defensible data to distinguish between anthropogenic and natural change in the deep sea. Without this understanding future changes in the deepwater environment could be incorrectly attributed to E&P operations.The data collected will be fundamental in helping Industry and the scientific community to build a long-term picture of deep-sea processes and ecology. In particular, it will enable us to:Measure and monitor deep-sea biological communities Monitor the pace of recovery from any unforeseen impacts Differentiate between natural & anthropogenic changes and provide a linkage between marine biodiversity & climate change The development of the system from concept through to fabrication, installation, and first data recovery is outlined including a first use of non-corrosive Glass Reinforced Plastic (GRP) as the primary structural element for a deepwater subsea facility. The selection of the various instrumentation modules and their application is discussed.

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Environmental Risk Assessment is a key element of a successful Environmental Management System. Hazards arise in all oil and gas exploration and production activities and risk management decisions should be based upon an understanding of these hazards, both in terms of environmental effects and the probability of occurrence. The purpose of the assessment process is to ensure that environmental risks are evaluated in a comprehensive and structured manner and that rational approaches are adopted to both the setting of acceptance criteria and the decision making and prioritising which forms an integral part of the risk management process. This paper outlines various complementary techniques which can be employed to assist the risk management process and discusses their potential application in the preparation of an Environmental Case. Introduction In order to manage environmental issues successfully, it is necessary to evaluate all possible environmental hazards which could arise from both routine operations and accidental events. Risk management decisions should be based upon an understanding of these hazards, in terms of both environmental consequences and probability of occurrence. While routine discharges are not strictly speaking a "risk" in that we know that they will occur on a regular or ongoing basis, the UKOOA Environmental Risk Assessment Workgroup decided to include routine events in the assessment process in order to develop a comprehensive methodology which can be used to aid decision making for all environmental aspects of the E&P lifecycle (exploration, appraisal, production, decommissioning). Environmental assessments typically examine only the effects on the environment from accidental and operational discharges (e.g. oil spills, air emissions, waste disposal, ground contamination). In practice, the risk to the organisation extends more widely than this; reflecting regulatory, political and market pressures which stem from public concern about the environment, and which have a direct bearing on the company's profitability. Analysis of risk needs to take account of this wider context, including the potential for consumer action such as boycotts of products and services. There is therefore a need to incorporate these external elements into environmental management decisions. Individual organisations must set their own criteria which will take into account their company policy, area of operation and reputational goals. This paper outlines a methodology to address these factors in the risk management process. The Environmental Risk Management Process The effectiveness of any environmental assessment and risk management process is dependent upon careful planning and execution of the various tasks within the timeframe of the overall activity. Hazard identification and therefore risk-based decision making is easier if it is undertaken proactively as an integral part of the activity in question, rather than as a critical review of decisions already undertaken. If risk management decisions are to be made in a timely and efficient manner it is important that the evaluation process is started as early as possible subject to the availability of the necessary information. When used this way, environmental management decisions will add value rather than being seen as a restrictive or negative constraint on progress, requiring rework and additional cost. For a new development project, the environmental risk management process involves a number of stages, beginning with the evaluation of the overall sensitivity of the area and then becoming more precise and focused as the necessary detail becomes available in the project development cycle. P. 159^