A Southeast Atlantic deep‐ocean observatory: first experiences and results

Abstract

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.

A Deeper Perspective: 5 Years of the DELOS Project

“…However, the last two decades have seen a rapid proliferation in deepwater exploration and production and it now accounts for more than 20% of all offshore production globally (Sandrea and Sandrea, 2010), and is expected to double again by 2030. Nevertheless, very little is known about the physical environment and biological activity in many of these deep-sea regions (Bagley et al 2007;Vardaro et al 2013). Although environmental baseline and operational monitoring surveys carried out as part of exploration and development activities provide some useful information, often producing specimens previously unknown to science (Walls et al 2010), these infrequent and patchy records do not enable us to develop an understanding of long-term changes, both natural and potentially anthropogenic (man-made).…”

“…This paper presents the results of the first 5 years of the Deep-ocean Environmental Long-term Observatory System (DELOS) offshore Angola (Walls et al 2005(Walls et al , 2010Bagley et al 2006Bagley et al , 2007Vardaro et al 2013), the first long-term monitoring system to be located in the Southeast Atlantic. The system comprises two sea floor platforms situated in 1400 m water depth in the vicinity of the Greater Plutonio oil production field and will provide long-term (>25 years) environmental monitoring data to both science and the oil industry.…”

“…A more detailed description of the DELOS design, construction and installation was presented at the 2010 SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production held in Rio de Janeiro, in Brazil (12-14th April, 2010;Walls et al 2010), and readers are referred to this and other publications on DELOS (e.g. Walls et al 2007;Bagley et al 2006Bagley et al , 2007Vardaro et al 2013) for further information on the design of the system. Fig.…”

“…3 also shows the seafloor bathymetry in the vicinity of DELOS. In general the bathymetry is characterised by a relatively uniform, shallowly sloping (<1°) seabed of fine-grained sediments (Vardaro et al 2013), deepening from the northeast to the southwest of the field.…”

Environmental Impacts of the Deep-Water Oil and Gas Industry: A Review to Guide Management Strategies

“…Long-term monitoring in the deep sea is generally rare (e.g., Hartman et al, 2012), and long-term environmental monitoring of deep-water oil and gas developments is extremely limited. A significant exception is found in the two observatory systems that were installed in deep waters off Angola to record long-term natural and anthropogenic changes in the physical, chemical, and biological environment and to allow an understanding of the pace of recovery from unforeseen impacts (Vardaro et al, 2013). Monitoring should also be carried out after production has ceased and throughout de-commissioning.…”