Biodiversity survey techniques: ROBIO and DOBO landers

The global demand for hydrocarbons and mineral resources is steadily depleting conventional reserves on land and in coastal waters. In recent years, considerable advances in technological ability have extended extractive industries into deeper water beyond the continental shelf. The composition, distribution and diversity of species assemblages in these environments are important aspects of the long-term stability and maintenance of the marine ecosystem. The introduction of oil extraction into poorly studied deep-sea environments has the potential to affect marine biodiversity through hydrodynamic activity associated with large underwater structures and extraction. In addition to existing exploration technology, environmental and diversity survey technologies are needed to meet the demand of modern environmental legislation

The ROBIO and DOBO Landers: deep-sea biodiversity surveys in areas of anthropogenic activity

The global demand for hydrocarbons and mineral resources is steadily depleting conventional reserves on land and in coastal waters. In recent years, considerable advances in technological ability have extended extractive industries into deeper water beyond the continental shelf. The composition, distribution and diversity of species assemblages in these environments are important aspects of the long-term stability and maintenance of the marine ecosystem. The introduction of oil extraction into poorly studied deep-sea environments has the potential to affect marine biodiversity through hydrodynamic activity associated with large underwater structures and extraction. In addition to existing exploration technology, environmental and diversity survey technologies are needed to meet the demand of modern environmental legislation. This article examines two technologies for monitoring biological indicators in the marine ecosystem - the robust diversity lander (ROBIO) and the deep-ocean benthic observer (DOBO). Both of these underwater vehicles are designed with experimental flexibility to be operated in a variety of baited or unbaited operational modes in response to user specific requirements. The data from both landers can contribute to ongoing monitoring programs with the aim of establishing environmental and biological baseline information prior to, and during, industrial activity

Depth zonation and latitudinal distribution of deep-sea scavenging demersal fishes of the Mid-Atlantic Ridge, 42 to 53°N

Scavenging fishes of the Mid-Atlantic Ridge (MAR) were investigated using a baited autonomous lander equipped with a time-lapse camera between 924 and 3420 m water depth along 3 east–west transects at 42, 51 and 53°N across the MAR. We photographed 22 taxa at bait. Community structure analysis revealed 3 main assemblages, shallow (924 to 1198 m), intermediate (1569 to 2355 m) and deep (2869 to 3420 m), dominated by 3 species, Synaphobranchus kaupii, Antimora rostrata and Coryphaenoides (Nematonurus) armatus, respectively. Abyssal species in the axial valley region were C. armatus, Histiobranchus bathybius and Spectrunculus sp. Compared with continental margin regions A. rostrata were abundant and grew to a large size in the 2 northern transects, whereas S. kaupii were reduced in abundance and maximum depth of occurrence. The size, abundance and depth distribution of C. armatus was consistent with the hypothesis that these fish are part of a population mixing freely across the deep North Atlantic Basin. Temperature and latitude influenced distribution. (1) Five taxa were found only in the southern transect: Pseudotriakis microdon, Centroscymnus coelolepis, Simenchelys parasitica, Anguilliformes sp. and Lepidion 1 sp. (guentheri?). (2) Eight taxa were confined to the 2 northern transects: Bathyraja sp., Coryphaenoides 1 sp. (leptolepis?/mediterraneus?), Coryphaenoides 2 sp. (leptolepis?/mediterraneus?), Macrourus berglax, young macrourids, Lepidion 2 spp. (schmidti?), Anarhichas denticulatus and an unidentified zoarcid (Lycodonus n. sp.?/Lycenchelys alba?). (3) Eight species were ubiquitous across all 3 transects: Etmopterus princeps, Hydrolagus affinis, H. bathybius, S. kaupii, C. armatus, A. rostrata, Lepidion eques and Spectrunculus 1 sp.

In situ comparison of activity in two deep-sea scavenging fishes occupying different depth zones

The activity of two scavenging deep–sea fishes occupying the same niche in overlapping depth zones were compared by in situ measurements of swimming speeds, tail–beat frequencies and by arrival time at baits. At 4800 m on the Porcupine Abyssal Plain, the grenadier Coryphaenoides (Nematonurus) armatus was the dominant scavenger, arriving at baits after 30 min, and swimming at relatively slow speeds of 0.17 body lengths (BL) sec-1. At 2500 m in the relatively food rich Porcupine Seabight both C. (N.) armatus and the blue–hake, Antimora rostrata, were attracted to bait, but A. rostrata was always the first to arrive and most of the bait was consumed before the C. (N.) armatus arrived. A. rostrata swam at mean speeds of 0.39 BL sec−1, similar to related shallow water species at equivalent temperatures. Observations on tail–beat frequency from video sequences confirmed the greater activity of A. rostrata. The data indicate that, given sufficient food supply, high pressure and low temperature do not limit activity levels of demersal deep–sea fishes. Low activity of C. (N.) armatus is an adaptation to poor food supply in the abyss, where these fishes dominate, but prevents it competing with the more active A. rostrata in shallower depths

Deep-sea scavenging demersal fish fauna of the Nazaré Canyon system, Iberian coast, north-east Atlantic Ocean

A baited imaging lander was deployed six times in the Nazaré Canyon at depths from 909 to 4361 m during August 2005 to investigate the demersal scavenging fishes. Species observed and lander-derived abundance estimates were similar to previous data from the Porcupine Seabight and abyssal plain, north-east Atlantic Ocean

Scavenging interactions between the arrow tooth eel Synaphobranchus kaupii and the Portuguese dogfish Centroscymnus coelolepis

A scavenging interaction between the arrow tooth eel Synaphobranchus kaupii and the Portuguese dogfish Centroscymnus coelolepis, both ubiquitous components of fish assemblages at bathyal depths, was observed. Using a baited camera between 1297 and 2453 m in the eastern Atlantic Ocean continental slope, it was shown that despite consistently rapid arrival times of S. kaupii (2 h before feeding, thus contradicting conventional scavenging assumptions in the presence of a food fall

Abyssal scavenging demersal fauna at two areas of contrasting productivity on the Subantarctic Crozet Plateau, southern Indian Ocean

The Crozet Plateau is situated below typical high-nutrient, low-chlorophyll (HNLC) waters of the southern Indian Ocean. The area to the east of the Crozet Islands experiences high levels of surface productivity during the austral summer due to natural iron enrichment from terrestrial sources and favourable light conditions. The demersal scavenging fauna at two areas of contrasting productivity, to the east and south of the islands, were investigated using two landers equipped with baited cameras and traps. Five species of scavenging fish were observed along with five groups of invertebrates during a single deployment of the RObust BIOdiversity (ROBIO) lander. Further deployments of the Fish RESPirometry (FRESP) video lander yielded no additional scavenging fish species. A modelled arrival and departure curve for the abyssal grenadier Coryphaenoides armatus suggests a region of low food availability compared to other regions worldwide. The ROBIO-derived abundance estimate for C. armatus of 187 ind. km–2 is comparable with published trawl-derived estimates. Significantly more amphipods were collected to the south of the islands, which was subject to lower organic matter supply. Reasons for this are unknown but may be due to differing current direction/velocities, or increased fish predation at the enriched site. The numerically dominant amphipod species present was Paralicella caperesca, followed by Eurythenes gryllus and Orchomenella gerulicorbis. A further five species were observed in low numbers, some occurring only once. One, Paracallisoma sp. nov, was a new species