The Nancy Foster was our base in the GoM

Near-bed hydrodynamic conditions were recorded for almost one year in the Viosca Knoll area (lease block 826), one of the most well-developed cold-water coral habitats in the Gulf of Mexico. Here, a reef-like cold-water coral ecosystem, dominated by the coral Lophelia pertusa, resembles coral habitats found off the southeastern US coast and the North East Atlantic. Two landers were deployed in the vicinity and outside of the coral habitat and measured multiple near-bed parameters, including temperature, salinity, current speed and direction and optical and acoustic backscatter. Additionally, the lander deployed closest to the coral area was equipped with a sediment trap that collected settling particles over the period of deployment at 27 day intervals. Long-term monitoring showed, that in general, environmental parameters, such as temperature (6.5–11.6 °C), salinity (34.95–35.4) and current speed (average 8 cm s⁻¹, peak current speed up to 38 cm s⁻¹) largely resembled conditions previously recorded within North East Atlantic coral habitats. Major differences between site VK 826 and coral areas in the NE Atlantic were the much higher particle load, and the origin of the particulate matter. Several significant events occurred during the deployment period beginning with an increase in current speed followed by a gradual increase in temperature and salinity, followed by a rapid decrease in temperature and salinity. Simultaneously with the decrease in temperature and salinity, the direction of the current changed from west to east and cold and less turbid water was transported upslope. The most prominent event occurred in July, when a westward flow lasted over 21 days. These events are consistent with bottom boundary layer dynamics influenced by friction (bottom Ekman layer). The Mississippi River discharges large quantities of sediment and dominates sedimentation regimes in the area. Furthermore, the Mississippi River disperses large amounts of terrestrial organic matter and nutrients, resulting in increased primary productivity, whereby marine organic matter is produced that will sink to the seafloor and can serve as food for the cold-water corals and associated species. As a result mass fluxes from the sediment trap were higher (1120–4479 mg m⁻² day⁻¹) than those observed in the North East Atlantic and were highest during periods of westward-flow, which corresponded to warm turbid water. During eastward-flow, colder and less turbid water was pushed upslope, resulting in lower mass fluxes. Trap samples had a low CaCO₃, high organic carbon content and high C/N ratios, suggesting a fluvial origin. The high sediment load in the water column can be a limiting factor for coral growth, especially since the corals can be smothered with sediment. However, eastward-flows provided periods of relatively clearer water that can remove sediment from the coral area and allow corals to expel sediment from their polyps. Around Viosca Knoll food supply comes from two possible sources. During April and June several fluorescence peaks were observed near the seabed, showing the arrival of phytodetritus in the area. Furthermore, a consistent diel vertical migration of zooplankton was observed that might provide an additional food source.

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F. Mienis, G.C.A. Duineveld, A.J. Davies, S.W. Ross, H. Seim, J. Bane & T.C.E. van Weering (2012) “The influence of near-bed hydrodynamic conditions on cold-water corals in the Viosca Knoll area, Gulf of Mexico” Deep-sea Research vol 1 60(1): 32-45.

 DOI

doi:10.1016/j.dsr.2011.10.007

The framework-forming coral Lophelia pertusa

Andrew J. Davies and John Guinotte

Cold-water corals are found in all the oceans of the world. Usually below 200 metres, they create structurally complex habitat that gives rise to a unique deep-sea ecosystem in, what otherwise may be a relatively featureless area. Numerous other filter-feeding organisms are found, along with fish that may use the coral as a nursery ground. Yet, we don’t know where many occurrences of cold-water coral are….

This is where habitat suitability modelling comes in. By using the best available scientific information and powerful statistical tools, we are able to predict, based on the species environmental requirements where they are likely to occur. Mine and John’s work, published in PLoS ONE is an important step towards turning habitat suitability modelling into a viable tool for the protection of vulnerable marine ecosystems in the deep sea. This paper represents several years of work, designing and constructing new approaches to allow us to model coral distributions at high resolution. The outputs speak for themselves, with a 1 km resolution, we may finally be able to say to other researchers, go here, you have a good chance of finding coral in this area. Or, we may be able to say, there is a high probability of coral occurrence here, perhaps we could designate this area closed to bottom contact fishing or other exploitation.

Read the abstract below, or download the PDF from either my site or the PLoS ONE site.

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Davies AJ, Guinotte JM (2011) Global Habitat Suitability for Framework-Forming Cold-Water Corals. PLoS ONE 6(4): e18483. doi:10.1371/journal.pone.0018483

Abstract

Predictive habitat models are increasingly being used by conservationists, researchers and governmental bodies to identify vulnerable ecosystems and species’ distributions in areas that have not been sampled. However, in the deep sea, several limitations have restricted the widespread utilisation of this approach. These range from issues with the accuracy of species presences, the lack of reliable absence data and the limited spatial resolution of environmental factors known or thought to control deep-sea species’ distributions. To address these problems, global habitat suitability models have been generated for five species of framework-forming scleractinian corals by taking the best available data and using a novel approach to generate high resolution maps of seafloor conditions. High-resolution global bathymetry was used to resample gridded data from sources such as World Ocean Atlas to produce continuous 30-arc second (~1 km²) global grids for environmental, chemical and physical data of the world’s oceans. The increased area and resolution of the environmental variables resulted in a greater number of coral presence records being incorporated into habitat models and higher accuracy of model predictions. The most important factors in determining cold-water coral habitat suitability were depth, temperature, aragonite saturation state and salinity. Model outputs indicated the majority of suitable coral habitat is likely to occur on the continental shelves and slopes of the Atlantic, South Pacific and Indian Oceans. The North Pacific has very little suitable scleractinian coral habitat. Numerous small scale features (i.e., seamounts), which have not been sampled or identified as having a high probability of supporting cold-water coral habitat were identified in all ocean basins. Field validation of newly identified areas is needed to determine the accuracy of model results, assess the utility of modelling efforts to identify vulnerable marine ecosystems for inclusion in future marine protected areas and reduce coral bycatch by commercial fisheries.

There have been very few studies of temporal processes at chemosynthetic ecosystems, even at relatively more accessible shallow water sites. Here we report the development and deployment of a simple cabled video observatory at ≈ 30 m water depth in Gullmarsfjorden, Sweden. The camera provides a live video feed to the internet of faunal activity in the experiments, which to date have included 5 separate whale-fall deployments. Our data suggest that the time to decomposition of small cetacean carcasses at shelf-depth settings is considerably slower than at deep-sea sites. We have also provided a new methodology for the deployment of low-cost live video observatories at up to 30 m water depth, which can be used both for research and outreach activities.

Published in Cahiers de Biologie Marine 51.

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Glover AG, Higgs ND, Bagley PM, Carlsson R, Davies AJ, Kemp KM, Last KS, Norling K, Rosenberg R, Wallin K-A, Källström B, Dahlgren TG (2010) “A live video observatory reveals temporal processes at a shelf-depth whale-fall” Cahiers de Biologie Marine 51: 375-381.

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Spatial heterogeneity in coral reef communities is well documented. This “species turnover” (beta diversity) on shallow warm-water reefs strongly conforms to spatial gradients in the environment as well as spatially autocorrelated biotic processes such as dispersal and competition. But the extent to which the environment and spatial autocorrelation create beta diversity on deep cold-water coral reefs such as those formed by Lophelia pertusa (Scleractinia) is unknown. The effects of remotely sensed and ground-truthed data were tested on the community composition of sessile suspension-feeding communities from the Mingulay Reef Complex, a landscape of inshore Lophelia reefs off the Scottish west coast. Canonical correspondence analysis determined that a statistically significant proportion (68%) of the variance in community composition could be explained by remotely sensed environmental variables (northerly and easterly aspect, seabed rugosity, depth), ground-truthed environmental variables (species richness and reef macrohabitat) and geospatial location. This variation was further partitioned into fractions explained by pure effects of the environment (51%), spatially structured environmental variables (12%) and spatial autocorrelation (5%). Beta diversity in these communities reflected the effects of both measured and unmeasured and spatially dependent environmental variables that vary across the reef complex, i.e., hydrography. Future work will quantify the significance and relative contributions of these variables in creating beta diversity in these rich communities.

Published in Coral Reefs 29.

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Henry L-A, Davies AJ, Roberts JM (2010) “Beta diversity of cold-water coral reef communities off western Scotland” Coral Reefs 29(2): 427-436.

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Not all introduced (invasive) species in a region will spread from a single point of introduction. Long-distance dispersal or further introductions can obscure the pattern of spread, but the regional importance of such processes is difficult to gauge. These difficulties are further compounded when information on the multiple scale process of invasive species range expansion is reduced to one-dimensional estimates of spread (e.g. km yr⁻¹). We therefore compared the results of two different metrics of range expansion: maximum linear rate of spread and accumulation of occupied grid squares (50 × 50 km) over time. An analysis of records for 54 species of introduced marine macrophytes in the Mediterranean and northeast Atlantic revealed cases where the invasion process was probably missed (e.g. Atlantic Bonnemaisonia hamifera) and suggested cases of secondary introductions or erratic jump dispersal (Dasysiphonia sp. and Womersleyella setacea). A majority of species analysed showed evidence for an accumulation of invaded sites without a clear invasion front. Estimates of spread rate are increasing for more recent introductions. The increase is greater than can be accounted for by temporally varying search effort and implies a historical increase in vector efficiency and/or a decreased resistance of native communities to invasion.

In press in the journal, Proceedings of the Royal Society Series B: Biological Sciences.

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Mineur F, Davies AJ, Maggs CA, Verlaque M, Johnson MP (In press) Fronts, jumps and secondary introductions suggested as different invasion patterns in marine species, with an increase in spread rates over time. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2010.0494

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The Lophelia pertusa community at Viosca Knoll (VK826) is the most extensive found to date in the Gulf of Mexico. As part of a multi-disciplinary study, the physical setting of this area was described using benthic landers, CTD transects and remotely operated vehicle observations. The site was broadly characterised into three main habitats: (1) dense coral cover that resembles biogenic reef complexes, (2) areas of sediment, and (3) authigenic carbonate blocks with sparse coral and chemosynthetic communities. The coral communities were dominated by L. pertusa but also contained numerous solitary coral species. Over areas that contained L. pertusa, the environmental conditions recorded were similar to those associated with communities in the north-eastern Atlantic, with temperature (8.5–10.6 °C) and salinity (ca. 35) falling within the known species niche for L. pertusa. However, dissolved oxygen concentrations (2.7–2.8 ml l⁻¹) and density (σ_Θ, 27.1–27.2 kg m⁻³) were lower and mass fluxes from sediment trap data appeared much higher (4002–4192 mg m⁻² d⁻¹). Yet, this species still appears to thrive in this region, suggesting that L. pertusa may not be as limited by lower dissolved oxygen concentrations as previously thought. The VK826 site experienced sustained eastward water flow of 10–30 cm s⁻¹ over the 5-day measurement period but was also subjected to significant short-term variability in current velocity and direction. In addition, two processes were observed that caused variability in salinity and temperature; the first was consistent with internal waves that caused temperature variations of 0.8 °C over 5–11 h periods. The second was high-frequency variability (20–30 min periods) in temperature recorded only at the ALBEX site. A further pattern observed over the coral habitat was the presence of a 24 h diel vertical migration of zooplankton that may form part of a food chain that eventually reaches the corals. The majority of detailed studies concerning local environmental conditions in L. pertusa habitats have been conducted within the north-eastern Atlantic, limiting most knowledge of the niche of this species to a single part of an ocean basin. Data presented here show that the corals at VK826 are subjected to similar conditions in temperature, salinity, and flow velocity as their counterparts in the north-east Atlantic, although values for dissolved oxygen and density (sigma-theta: σ_Θ) are different. Our data also highlight novel observations of short-term environmental variability in cold-water coral habitat.

Published in Deep Sea Research vol one 57.

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Davies, A.J., Duineveld, G.C.A., van Weering, T.C.E., Mienis, F., Quattrini, A.M., Seim, H.E., Bane, J.M. & Ross, S.W. (2010) “Short-term environmental variability in cold-water coral habitat at Viosca Knoll, Gulf of Mexico.” Deep-sea Research Vol 1. 57(2): 199-212.

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In 2006 and 2007, multiple deployments of current meters and optical sensors on landers and moorings were made in the first detailed in situ study of the particle supply to the coral community in the Mingulay Reef complex in the Sea of Hebrides at 140 m water depth. Two distinct and predictable supply mechanisms were resolved. One mechanism consisted of the rapid downwelling of surface water caused by hydraulic control of tidal flow that transports particles from the surface to the corals in less than an hour. The rapid downwelling was recorded on the reef top as a pulse of warm, fluorescent, and relatively clear water at the onset of the flood and ebb tides. The pulse was strongest after flood tide and lasted for up to 3 hours. The second mechanism consisted of advection onto the reef of deep bottom water with a high suspended matter load. This advection occurred during peak tides and was combined with topographical current acceleration on the reef top enhancing delivery of particles to the corals.

Published as feature article in Limnology and Oceanography

http://www.aslo.org/lo/pdf/vol_54/issue_2/0620.pdf

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Davies, A.J., Duineveld, G.C.A., Lavaleye, M.S.S., Bergman, M.J.N., van Haren, H. & Roberts, J.M. (2009) “Downwelling and deep-water bottom currents as food supply mechanisms to the cold-water coral Lophelia pertusa (Scleractinia) at the Mingulay Reef Complex.” Limnology and Oceanography 54(2): 620-629.

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An important aim of large, pan-European scientific projects with numerous research groups is to integrate and visualize the acquired distributed data sets and results. The large volume of diverse data gathered and the need to disseminate results among the scientific community and beyond requires using a Geographic Information System (GIS). This article presents our experiences in creating a unified Web-based GIS for HERMES. The HERMES-GIS is based on Web Mapping Services that include direct links to the World Data Center for Marine Environmental Science and its large, long-term geoscience data archive and publication unit, PANGAEA (http://www.pangaea.de). It incorporates metadata and data from all project partners to provide users with basic analytical and visualization tools for archived (distributed) and personal (local) data, and it is also a policymaking tool. Additionally, we illustrate two important GIS applications inside the HERMES community— the use of data models to integrate several subdisciplines and the use of predictive habitat modeling.

Publication in Oceanography 22(1).

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De Mol B, Querol N, Davies AJ, Schäfer A, Foglini F, Gonzales-Mirelis G, Kopke K, Dunne D, Shewe I, Trincardi F, Canals M (2009) HERMES-GIS: a tool to connect scientists. Oceanography 22(1): 144-153.

http://www.tos.org/oceanography/

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Many aquatic organisms rely on the suspension of particulate matter for food or for building materials, yet these conditions are difficult to replicate in laboratory mesocosms. Consequently, husbandry and experimental conditions may often be sub-optimal. The VOrtex Resuspension Tank (VORT) is a simple and reliable system for the resuspension of food or sediments using an enclosed airlift. The particle rain from the lift is mixed in the tank by two water inputs that provide directional current flow across the study organism(s). The vortex mixing creates a turbulent lateral water flow that allows the distribution of particulate matter outwards from the sediment outflow. By calibrating a VORT it is possible to control sedimentation rate by manipulating water and air flow rates. As an example application, three VORTs were maintained under different sediment loading to assess the sediment fraction utilisation and tube growth rates of the tube-building polychaete worm Sabellaria spinulosa. S. spinulosa consistently utilised a lower mean particle size than that of the background sediment when provided with well sorted medium sands. Under sediment starved conditions, there was net erosion of colonies whereas under intermediate and high sediment rates there was consistent cumulative growth throughout a 15 d experiment. This highlights the importance of suspended sediment for S. spinulosa and also the suitability of the VORT system for maintaining organisms with suspended matter requirements.

Publication in Journal of Experimental Marine Biology and Ecology 370.

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Davies, A.J., Last, K.S., Attard, K. & Hendrick, V.J. (accepted) “Maintaining turbidity and current flow in laboratory aquarium studies, a case study using Sabellaria spinulosa” Journal of Experimental Marine Biology and Ecology 370, 35-40.

http://dx.doi.org/10.1016/j.jembe.2008.11.015

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Published in Marine Ecology-Progress Series (2008)

Limpets, predominantly Patella vulgata, have been associated with damaged or receding canopies of Ascophyllum nodosum. Although the damage results from limpet grazing, the benefits that limpets gain from this behaviour are unclear as A. nodosum is thought to be well defended from grazers by anti-herbivore compounds. In this study, P. vulgata individuals were enclosed at densities between 80 and 320 m-2 at two sites within Strangford Lough. Limpet growth and limpet survival were compared between unsubsidised controls and treatments in which limpet diets were subsidised by fronds of A. nodosum. When subsidised, limpet residual growth rates were significantly higher and mortality was lower than in unsubsidised control treatments. Individual limpets consumed a similar amount of A. nodosum regardless of limpet density. Higher densities of limpets therefore consumed more A. nodosum per replicate. The effects of A. nodosum in maintaining limpet densities could resonate through sheltered rocky communities. The importance of a macroalgal subsidy in supporting limpet populations may have been underestimated or overlooked in earlier studies. Therefore, the extensive and productive macroalgal canopies that characterise many sheltered temperate rocky shores could be more sensitive to increased limpet abundances than previously thought.

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Davies, A.J., Johnson, M.P. & Maggs, C.A. (2008) “Subsidy by Ascophyllum nodosum increases growth rate and survivorship of Patella vulgata” Marine Ecology Progress Series, 366: 43-48.

http://dx.doi.org/10.3354/meps07453

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