Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Elementa Science of the Anthropocene 5 (2017): 4, doi:10.1525/elementa.203.

Description: The deep sea encompasses the largest ecosystems on Earth. Although poorly known, deep seafloor ecosystems provide services that are vitally important to the entire ocean and biosphere. Rising atmospheric greenhouse gases are bringing about significant changes in the environmental properties of the ocean realm in terms of water column oxygenation, temperature, pH and food supply, with concomitant impacts on deep-sea ecosystems. Projections suggest that abyssal (3000–6000 m) ocean temperatures could increase by 1°C over the next 84 years, while abyssal seafloor habitats under areas of deep-water formation may experience reductions in water column oxygen concentrations by as much as 0.03 mL L–1 by 2100. Bathyal depths (200–3000 m) worldwide will undergo the most significant reductions in pH in all oceans by the year 2100 (0.29 to 0.37 pH units). O2 concentrations will also decline in the bathyal NE Pacific and Southern Oceans, with losses up to 3.7% or more, especially at intermediate depths. Another important environmental parameter, the flux of particulate organic matter to the seafloor, is likely to decline significantly in most oceans, most notably in the abyssal and bathyal Indian Ocean where it is predicted to decrease by 40–55% by the end of the century. Unfortunately, how these major changes will affect deep-seafloor ecosystems is, in some cases, very poorly understood. In this paper, we provide a detailed overview of the impacts of these changing environmental parameters on deep-seafloor ecosystems that will most likely be seen by 2100 in continental margin, abyssal and polar settings. We also consider how these changes may combine with other anthropogenic stressors (e.g., fishing, mineral mining, oil and gas extraction) to further impact deep-seafloor ecosystems and discuss the possible societal implications. 

Description: A.K. Sweetman D.O.B. Jones and R. Danovaro acknowledge funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement 603418 (MIDAS), and the European Union Horizon 2020 research and innovation programme under grant agreement 689518 (MERCES). L.-A. Henry and J.M. Roberts acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 678760 (ATLAS).

Description: Knowledge on basic biological functions of organisms is essential to understand not only the role they play in the ecosystems but also to manage and protect their populations. The study of biological processes, such as growth, reproduction and physiology, which can be approached in situ or by collecting specimens and rearing them in aquaria, is particularly challenging for deep-sea organisms like cold-water corals. Field experimental work and monitoring of deep-sea populations is still a chimera. Only a handful of research institutes or companies has been able to install in situ marine observatories in the Mediterranean Sea or elsewhere, which facilitate a continuous monitoring of deep-sea ecosystems. Hence, today’s best way to obtain basic biological information on these organisms is (1) working with collected samples and analysing them post-mortem and / or (2) cultivating corals in aquaria in order to monitor biological processes and investigate coral behaviour and physiological responses under different experimental treatments. The first challenging aspect is the collection process, which implies the use of oceanographic research vessels in most occasions since these organisms inhabit areas between ca. 150 m to more than 1000 m depth, and specific sampling gears. The next challenge is the maintenance of the animals on board (in situations where cruises may take weeks) and their transport to home laboratories. Maintenance in the home laboratories is also extremely challenging since special conditions and set-ups are needed to conduct experimental studies to obtain information on the biological processes of these animals. The complexity of the natural environment from which the corals were collected cannot be exactly replicated within the laboratory setting; a fact which has led some researchers to question the validity of work and conclusions drawn from such undertakings. It is evident that aquaria experiments cannot perfectly reflect the real environmental and trophic conditions where these organisms occur, but: (1) in most cases we do not have the possibility to obtain equivalent in situ information and (2) even with limitations, they produce relevant information about the biological limits of the species, which is especially valuable when considering potential future climate change scenarios. This chapter includes many contributions from different authors and is envisioned as both to be a practical “handbook” for conducting cold-water coral aquaria work, whilst at the same time offering an overview on the cold-water coral research conducted in Mediterranean laboratories equipped with aquaria infrastructure. Experiences from Atlantic and Pacific laboratories with extensive experience with cold-water coral work have also contributed to this chapter, as their procedures are valuable to any researcher interested in conducting experimental work with cold-water corals in aquaria. It was impossible to include contributions from all laboratories in the world currently working experimentally with cold-water corals in the laboratory, but at the conclusion of the chapter we attempt, to our best of our knowledge, to supply a list of several laboratories with operational cold-water coral aquaria facilities.

Description: The rate of discovery of reefs of the cold-water coral Lophelia pertusa (Linnaeus, 1758) has been remarkable, and attributable to the increased use of underwater video. These reefs form a major three-dimensional habitat in deeper waters where little other ‘cover’ for fish is available. They are common in the eastern North Atlantic, and occur at least in the western North Atlantic and off central Africa. There are also other non-reef records of Lophelia in the Atlantic, and in Indian and Pacific oceans. Thus, not only are these reefs a significant habitat on a local scale, but they may also provide an important habitat over a very wide geographic scale. The present study examined the association of fish species with Lophelia in the Northeast Atlantic, including the Trondheimsfjord and Sula Ridge in Norway, Kosterfjord in Sweden, Darwin Mounds west of Scotland, and Rockall Bank, Rockall Trough and Porcupine Seabight off Ireland. The fish fauna associated with a shipwreck west of Shetland was also studied. Data were collected from 11 study sites at 8 locations, using 52 hours of video and 15 reels of still photographs. Video and still photographs were collected from (1) manned submersible, (2) surface controlled remotely operated vehicle (ROV), (3) a towed “hopper” camera, (4) wide angle survey photography (WASP), (5) seabed high resolution imaging platform (SHRIMP), and (6) an in situ time-lapse camera “Bathysnap”. It was possible to identify 90 % of fish observed to species level and 6.5 % to genus or family level. Only 3.5 % of the fish were not identifiable. A guide to the fishes is given at http://www.ecoserve.ie/projects/aces/. Twenty-five species of fishes from 17 families were recorded over all the sites, of which 17 were of commercial importance and comprised 82 % of fish individuals observed. These commercial fish species contribute 90 % of commercial fish tonnage in the North Atlantic. The habitats sampled were comprised of 19 % reef, 20 % transitional zone (i.e. between living coral and debris zone), 25 % coral debris and 36 % off-reef seabed. Depth was the most significant parameter in influencing the fish associated with the reefs, both at the species and family level. There was a complete separation of sites above and below 400–600 m depth by multi-dimensional scaling (MDS) analysis. Less distinct assemblages of fish species were associated with each habitat. Fish species richness and abundance was greater on the reef than surrounding seabed. In fact, 92 % of species, and 80 % of individual fish were associated with the reef. The present data indicates that these reefs have a very important functional role in deep-water ecosystems as fish habitat.

Description: Cold-water corals create highly complex biogenic habitats that promote and sustain high biological diversity in the deep sea and play critical roles in deep-water ecosystem functioning across the globe. However, these often out of sight and out of mind ecosystems are increasingly under pressure both from human activities in the deep sea such as fishing and mineral extraction, and from a rapidly changing climate. This chapter gives an overview of the importance of cold-water coral habitats, the threats they face and how recent advances in understanding of both past and present cold-water coral ecosystems helps us to understand how well they may be able to adapt to current and future climate change. We address key knowledge gaps and the ongoing efforts at national and international scales to promote and protect these important yet vulnerable ecosystems.