Description: The spatial variability in the mix of species making up Cold-water coral reef communities is not well known. In this study abundances of a selection of megafauna (Lophelia pertusa, Madrepora oculata, Paragorgia arborea, Primnoa resedaeformis, Mycale lingua, Geodia baretti, Acesta excavata and fish) were quantified throughout 9 manned submersible video transects from 3 reef complexes (Røst Reef, Sotbakken Reef and Traena Reef) on the Norwegian margin. Substrate type (coral structure, rubble, exposed hardground or soft sediment) was also recorded. Variations in the densities of these fauna (with respect to both reef complex and substrate type) were investigated, with spatial covariance between species assessed. For the majority of fauna investigated, densities varied by both reef and substrate. Spatial covariance indicated that some species may be utilising similar habitat niches, but that minor environmental differences may favour colonisation by one or other at a particular reef. Fish densities were generally higher in regions with biogenic substrate (coral structure and coral rubble substrates) than in areas of soft or hardground substrate. Further, fish were more abundant at the northerly Sotbakken Reef at time of study than elsewhere. Community structure varied by reef, and therefore management plans aimed at maintaining the biodiversity of reef ecosystems on the Norwegian margin should take this lack of homogeneity into account.

Description: Cold-watercoralreefs occur in many regions of the world's oceans. Fundamental questions regarding their functioning remain unanswered. These include the biogeochemical influence of reefs on their environment (“reef effects”) and the influence of hydrodynamic processes on reef nutrition. In a succession of field campaigns in 2007 and 2008, these questions were addressed at the Tislercold-watercoralreef, which is centered on a sill peak in the Norwegian Skagerrak. A variety of methodological approaches were used. These consisted of the collection of CTD and chlorophyll profiles, current measurements, sampling of particulateorganicmatter (POM) in the benthic boundary layer (BBL) across the reef with subsequent chemical analyses, and the chemical analysis of freshly released Lophelia pertusa mucus. CTD and chlorophyll profiles indicated that downstream of the sill crest, downwelling delivered warmer, fresher and chlorophyll richer water masses down to the BBL. Both sides of the reef received downwelling nutrition delivery, as flow direction over the reef reversed periodically. Several chemical composition indicators revealed that suspended POM was significantly fresher on the downstream side of the reef than on the upstream side. L. pertusa mucus from the TislerReef was labile in composition, as indicated by a low C/N ratio and a high amino acid degradation index (DI) value. Particulateorganic carbon (POC) content in the BBL was significantly depleted across the reef. Lateral depositional fluxes were calculated to be 18–1485 mg POC m−2 d−1, with a mean of 459 mg POC m−2 d−1. We propose that the combination of fresh, downwelling POM with mucus released from the reef was the cause of the greater lability of the downstream POM. Our data on POC depletion across the reef suggest that cold-watercoralreefs could play an important role in carbon cycling along continental margins. Research Highlights: ► Downwelling is important for reef nutrition of cold-watercoralreefs located on sills. ► Lophelia pertusa mucus is a labile organic substrate. ► POM on the downstream side of a reef can be more labile than on the upstream side. ► POC content in the BBL was significantly depleted across TislerReef. ► Cold-watercoralreefs could play an important role in carbon cycling in the oceans.

Description: Sinking of aggregated phytoplankton cells is a crucial mechanism for transporting carbon to the seafloor and benthic ecosystem, with such aggregates often scavenging particulate material from the water column as they sink. In the vicinity of drilling rigs used by the oil and gas industry, the concentration of particulate matter in the water column may at times be enriched as a result of the discharge of ‘drill cuttings’ – drilling waste material. This investigation exposed laboratory produced phytoplankton aggregates to drill cuttings of various composition (those containing no hydrocarbons from reservoir rocks and those with a 〈1% hydrocarbon content) and assessed the change in aggregate size, settling rate and resuspension behavior of these using resuspension chambers and settling cylinders. Results indicate that both settling velocity and seabed stress required to resuspend the aggregates are greater in aggregates exposed to drill cuttings, with these increases most significant in aggregates exposed to hydrocarbon containing drill cuttings.

Description: The dissolution of CaCO3 is one of the ways ocean acidification can, potentially, greatly affect the ballast of aggregates. A diminution of the ballast could reduce the settling speed of aggregates, resulting in a change in the carbon flux to the deep sea. This would mean lower amounts of more refractory organic matter reaching the ocean floor. This work aimed to determine the effect of ocean acidification on the ballast of sinking surface aggregates. Our hypothesis was that the decrease of pH will increase the dissolution of particulate inorganic carbon ballasting the aggregates, consequently reducing their settling velocity and increasing their residence time in the upper twilight zone. Using a new methodology for simulation of aggregate settling, our results suggest that future pCO2 conditions can significantly change the ballast composition of sinking aggregates. The change in aggregate composition had an effect on the size distribution of the aggregates, with a shift to smaller aggregates. A change also occurred in the settling velocity of the particles, which would lead to a higher residence time in the water column, where they could be continuously degraded. In the environment, such an effect would result in a reduction of the carbon flux to the deep-sea. This reduction would impact those benthic communities, which rely on the vertical flow of carbon as primary source of energy.

Description: Environmental conditions within deep-sea ecosystems such as cold-seep provinces or deep-water coral reefs vary temporally and spatially over a range of scales. To date, short periods of intense ship-borne activity or low resolution, fixed location studies by Lander systems have been the main investigative methods used to investigate such sites. Cabled research infrastructures now enable sensor packages to receive power and transmit data from the deep-sea in real-time. By attaching mobile research platforms to these cabled networks, the investigation of spatial and temporal variability in environmental conditions and/or faunal behaviour across the deep sea seafloor is now a possibility. Here we describe one such mobile platform: a tracked Deep Sea Crawler, controlled in real-time via the Internet from any computer worldwide. The Crawler has been extensively used on the NEPTUNE Canada cabled observatory network at a cold-seep site at ∼890 m depth in the Barkley Canyon, NE Pacific. We present both the technical overview of the Crawler development and give examples of scientific results achieved.

Description: Society’s needs for a network of in situ ocean observing systems cross many areas of earth and marine science. Here we review the science themes that benefit from data supplied from ocean observatories. Understanding from existing studies is fragmented to the extent that it lacks the coherent long-term monitoring needed to address questions at the scales essential to understand climate change and improve geo-hazard early warning. Data sets from the deep sea are particularly rare with long-term data available from only a few locations worldwide. These science areas have impacts on societal health and well-being and our awareness of ocean function in a shifting climate. Substantial efforts are underway to realise a network of open-ocean observatories around European Seas that will operate over multiple decades. Some systems are already collecting high-resolution data from surface, water column, seafloor, and sub-seafloor sensors linked to shore by satellite or cable connection in real or near-real time, along with samples and other data collected in a delayed mode. We expect that such observatories will contribute to answering major ocean science questions including: How can monitoring of factors such as seismic activity, pore fluid chemistry and pressure, and gas hydrate stability improve seismic, slope failure, and tsunami warning? What aspects of physical oceanography, biogeochemical cycling, and ecosystems will be most sensitive to climatic and anthropogenic change? What are natural versus anthropogenic changes? Most fundamentally, how are marine processes that occur at differing scales related? The development of ocean observatories provides a substantial opportunity for ocean science to evolve in Europe. Here we also describe some basic attributes of network design. Observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in European Seas adding needed certainty to estimates of future oceanic conditions. Observatory data can be analysed along with other data such as those from satellites, drifting floats, autonomous underwater vehicles, model analysis, and the known distribution and abundances of marine fauna in order to address some of the questions posed above. Standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit. The connection of ocean observatory effort into larger frameworks including the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring of Environment and Security (GMES) is integral to its success. It is in a greater integrated framework that the full potential of the component systems will be realised. Highlights ► Societies increasingly depend on timely information on ecosystems and natural hazards. ► Data is needed to improve climate-related uncertainty and geo-hazard early warning. ► Observatory networks coordinate and integrate the collection of standardised data. ► Ocean observatories provide opportunity for ocean science to evolve.