Lophelia pertusa at VK826

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 (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.

In press in Deep Sea Research vol 1.

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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. (in press) “Short-term environmental variability in cold-water coral habitat at Viosca Knoll, Gulf of Mexico.” Deep-sea Research Vol 1. DOI: 10.1016/j.dsr.2009.10.012.

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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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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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Published in Deep-sea Research Vol. 1 (2008)

Ecological-niche factor analysis (ENFA) was applied to the reef framework-forming cold-water coral Lophelia pertusa. The environmental tolerances of this species were assessed using readily available oceanographic data, including physical, chemical, and biological variables. Lophelia pertusa was found at mean depths of 468 and 480 metres on the regional and global scales and occupied a niche that included higher than average current speed and productivity, supporting the theory that their limited food supply is locally enhanced by currents. Most records occurred in areas with a salinity of 35, mean temperatures of 6.2-6.7 °C and dissolved oxygen levels of 6.0-6.2 ml l-1. The majority of records were found in areas that were saturated with aragonite but had low concentration of nutrients (silicate, phosphate, and nitrate). Suitable habitat for L. pertusa was predicted using ENFA on a global and a regional scale that incorporated the north-east Atlantic Ocean. Regional prediction was reliable due to numerous presence points throughout the area, whereas global prediction was less reliable due to the paucity of presence data outside of the north-east Atlantic. However, the species niche was supported at each spatial scale. Predicted maps at the global scale reinforced the general consensus that the North Atlantic Ocean is a key region in the worldwide distribution of L. pertusa. Predictive modelling is an approach that can be applied to cold-water coral species to locate areas of suitable habitat for further study. It may also prove a useful tool to assist spatial planning of offshore marine protected areas. However, issues with eco-geographical datasets, including their coarse resolution and limited geographical coverage, currently restrict the scope of this approach.

Full citation

Davies, A.J., Wisshak, M., Orr, J.C. & Roberts, J.M. (2008) “Predicting suitable habitat for Lophelia pertusa” Deep-sea Research Volume 1, 55: 1048-1062.

http://dx.doi.org/10.1016/j.dsr.2008.04.010

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Published in JMBA UK 2009.

A three year study was undertaken during 2002 to 2004 from May to September to estimate abundance and density of harbour porpoises on the north coast of Anglesey, Wales, UK. There were no ecological data regarding the harbour porpoises in Anglesey waters so the ability to influence conservation measures was highly constrained.

Boat based transects using distance sampling techniques were applied so a robust estimate of density and abundance could be attained. The study area consisted of a block approximately 489 km2 extending from the east of Point Lynas to the west of South Stack on north coast of Anglesey. The study area was divided into 5 blocks consisting of 31 perpendicular transect lines to the shore. Each of the transect lines were surveyed 1–5 times by the end of the three year study.

Based on the assumption that g(0) = 1 the density of harbour porpoises for the 489 km2 study site was estimated to be 0.630 individuals/km2 (CV = 0.20) and the abundance is estimated to be 309 individuals (CV = 0.20). Heterogeneity in density and abundance was observed across the 5 blocks which showed Point Lynas and South Stack to have the highest densities. This distribution was closely associated to fine-scale oceanographic features which cause prey to be concentrated and may facilitate foraging for harbour porpoises. The study showed that Anglesey provides coastal habitats for the harbour porpoise and was the first study of this kind in North Wales, UK.

Full citation

Shucksmith R, Jones NH, Stoyle GW, Davies A, Dicks EF (2009) Abundance and distribution of the harbour porpoise ( Phocoena phocoena) on the north coast of Anglesey, Wales, UK. Journal of the Marine Biological Association of the United Kingdom, 89(5), 1051-1058.

http://dx.doi.org/10.1017/S0025315408002579

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Magnetic sensors have existed for many years and are widely used in different applications such as navigation systems, automation, position detection and current detection (amongst others). In this paper we explore a unique application of underwater magnetic sensing using a magneto-resistive sensor to monitor animal behaviour. Animal behaviour researchers have used several different techniques to study the behaviour of limpets. Most common are motographic methods using time-lapse photography. This technique is limited by low resolution, time consuming data analysis and sometimes an obscured field of view. Here, we present preliminary results from the use of a magneto-resistive sensor attached to the common limpet Patella vulgata. The (Honeywell HMC1052) 2-axis anisotropic magneto-resistive (AMR) sensor was fixed using epoxy putty to the shell of a limpet. The sensor has the capability to capture the limpet’s orientation with a resolution of 0.05°. This high resolution allows us to describe a range of behavioural responses which was not possible using earlier techniques. Limpet movement was truthed using time-lapse infra-red videography. Magneto-resistive sensors can quantify orientation behaviour, be used in extreme environments and provide superior data to qualitative and interpreted observations obtained from previous techniques. Several future developments may increase the applicability of this technique, such as using an artificial magnetic field to precisely locate animals at sub-GPS resolution.

Full citation

Wadke, P.M., Burrows, M.T., Meldrum, D. & Davies, A.J. (2007) “Using magneto-resitive sensors to monitor animal behaviour: a case study using limpets” Proceedings, Oceans 2007 MTS/IEEE Vancouver.

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Human activity in the deep sea is extending ever deeper, with recent research showing that this environment is more sensitive to human and natural impacts than previously thought. Some deep-water fish stocks have collapsed and fishing methods such as bottom trawling have raised international concern over the habitat damage they cause. It is likely that in its current form, deep-sea fishing is unsustainable. Diminishing reserves of hydrocarbons in shallow water are pushing exploration and production into deeper waters, which may cause damage to little known deep-sea habitats. The deep sea is also proposed as an environment where anthropogenic carbon dioxide could be stored to minimise the effect of its release into the atmosphere. At the same time, rising atmospheric carbon dioxide levels may be altering the chemical equilibrium of the global ocean by lowering pH. Many countries are now beginning to designate some deep-sea habitats as marine protected areas in measures to reduce the damage caused by fishing and other anthropogenic activities. This review examines these current and emerging issues in deep-sea conservation and discusses conservation status and the designation of protected areas. The enforcement of protected areas using satellite tracking of vessels is discussed and applied to an internationally agreed deep-water conservation area, which aims to protect cold-water coral habitats on the Darwin Mounds in the north east Atlantic Ocean.

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Davies, A.J., Roberts, J.M. & Hall-Spencer, J. (2007) “Preserving deep-sea natural heritage: Emerging issues in offshore conservation and management” Biological Conservation 138: 299-312.

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Published in Marine Ecology-Progress Series (2007)

The role of limpet grazing in preventing the development of algal canopies is a recurrent theme in intertidal ecology. Less is known about interactions of limpets with the long-term dynamics of established canopies. Aerial photographs indicate that intertidal canopy cover has declined over the past 44 yr in Strangford Lough, Northern Ireland. There has been a loss of the previously continuous cover of Ascophyllum nodosum (L.) Le Jolis in the mid-shore. A barnacle dominated assemblage now fills gaps in the A. nodosum canopy. The rates at which barnacle patches become established and grow have increased since 1990. Changes in canopy cover have been accompanied by increases in limpet densities since the 1980s. Measurements between 2003 and 2004 showed no increase in length of A. nodosum fronds when limpets Patella vulgata had access to the algal holdfasts. In contrast, when limpets were experimentally excluded from the holdfasts, there was net frond growth. In the Isle of Man, which is climatically similar to Strangford Lough but has fewer limpets, growth occurred regardless of limpet grazing. The breaking force for A. nodosum declined with increasing local densities of limpets. A. nodosum is a sheltered shore species, potentially vulnerable to changes in wave exposure. There is no evidence, however, that Strangford Lough has become windier over the past 3 decades. Variation in wave exposure among locations within the lough was not related to rates of barnacle patch creation or expansion. Limpet population density has increased following a series of mild winters. Climate change may have a role in causing canopy loss, not by direct effects on the growth of fucoids, but by increasing the severity of grazing through changes to limpet populations.

Full citation

Davies, A.J., Johnson, M.P. & Maggs, C.A. (2007) “Unexpected loss of Ascophyllum nodosum caused by limpet grazing” Marine Ecology-Progress Series 339: 131-141.

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Published in Estuarine, Coastal and Shelf Science (2006)

Both climate change and the North Atlantic Oscillation (NAO) may influence coastal systems by altering wave exposure. The effects of such climatic forcing are often coherent over relatively large geographic areas. Temporal trends in wave exposure at any particular shore are, however, the result of an interaction between site-specific fetch characteristics and changes in wind climate. This leads to contrasting trends in wave exposure at locations separated by no more than a few kilometres. Wave exposures were estimated at locations around a sea lough over 32 years to characterise these scales of variability. Locations separated by approximately 5 km had independent dynamics with respect to the temporal trend (correlation range -0.35 to 0.44) and to associations with the NAO (correlation range -0.18 to 0.40). Wave exposure can therefore be increasing for a section of shore while nearby areas have the opposite trend. Mean exposure at a location was not a good predictor of the temporal trend. More exposed sites were, however, sensitive to variations in the strength of the NAO. The reduction of large scale forcing to small-scale variability has implications for the detection and mitigation of potential climate change impacts.

Full citation

Davies, A.J. & Johnson, M.P. (2006) “Coastline configuration disrupts large-scale climatic forcing, leading to divergent temporal trends in wave exposure” Estuarine and Coastal Shelf Science 69 (3-4): 643-648.

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