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GeoHab 2005 Agenda and Abstracts
Agenda
Abstracts
The HERMES project
(Hotspot Ecosystem Research on the Margins of European Seas)
Phil Weaver
Southampton Oceanography Centre, UK
Europe’s deep-ocean margin stretches over a distance of 15,000 km along the Atlantic ocean from the Arctic to the Iberian margin and from western to eastern Mediterranean, through to the Black Sea. The margin extends from the shelf edge at about 200m depth down to c.4000m depth where the abyssal plain or oceanic basins begin, covering 3 million km2 - an area about one third of that covered by Europe’s landmass. Most of this deep-ocean frontier lies within Europe’s Exclusive Economic Zone (EEZ) and is therefore of direct interest for the exploitation of biological, energy and mineral resources. A major aim of European policy is to develop these resources in an ecologically sustainable manner. This requires a profound knowledge of ocean margin ecosystem structure and dynamics considering the variety and complexity of the continental margin environments, which hold deep-sea corals, chemosynthetic life, and more or less specialised fauna in canyons. The HERMES project will address these issues by investigating some of the more important “hotspot” ecosystems in a coherent manner, integrating research on biodiversity and biological processes intimately with the physical factors controlling ecosystems (geology, sedimentology, physical oceanography, biogeochemistry). In addition, we will set present-day ecosystems in an historical framework by studying the sediment record to determine long-term environmental changes and the potential response of ecosystems to global change over decadal to millennial scales.
Our “hotspot ecosystems” include cold-water corals, canyons, cold seeps and anoxic ecosystems as well as some aspects of the open slope environments between the hotspots.
Figure 1: Map showing the HERMES study areas.
Large open circles indicate specific study sites.
Cold-water coral ecosystems
The colonial stone corals Lophelia pertusa and Madrepora oculata occur on the deep shelves along 4500 km of the northwestern European continental margin, and in Scandinavian fjords. The intense calcification of the coral colonies enables them to provide a three-dimensional complex habitat for a vast number of associated species that live within or alongside the coral ecosystem. With this large latitudinal spread of the coral ecosystem, we can analyse ecosystem response to different trophic regimes, comparing seasonally eutrophic, high latitudinal settings with more meso- to oligotrophic sites further south in the NE Atlantic and the Mediterranean Sea. These comparative studies will be carried out by assessing biodiversity trends (taxonomy and molecular genetics) and trophic food webs (biochemistry).
Site-specific life history studies will be performed on the coral skeletons using environmentally sensitive trace elements and stable isotopes. In order to define the physical forcing factors and the quality and quantity of carbon-flux rates, targeted long-term experiments using benthic landers equipped with CTD-probes, ADCPs, current meters, particle traps and time-lapse cameras will be deployed in a number of hydro-acoustically mapped and ROV-inspected coral sites. In some locations cold-water coral associations thrive in close vicinity to hydrocarbon fluid flow environments, such as in or near active pockmarks on the Norwegian Shelf, or on the flanks of mud volcanoes in the Gulf of Cadiz. These areas are prime sites for addressing whether coral communities are associated with seabed geosphere processes.
The aims of our study are to understand the structure, functioning and dynamics of deep-water coral ecosystems under different trophic regimes and under different climatic settings. We will investigate the change of biodiversity which affected deep-water coral ecosystems during the last glacial-interglacial cycle and forecast how the ecosystem will react to future environmental change. The links between deep-water circulation patterns and the likely geosphere-biosphere coupling of deep-water coral ecosystems in hydrocarbon provinces will be studied. The overall aim is to analyse and minimise the negative impacts of human activities on deep-water coral ecosystems through provision of mitigation options, risk assessments and recommendations for management and conservation.
Canyon ecosystems
Canyons were chosen as a focus for HERMES because they are key environments on the continental margin that are affected by dynamic geological and physical oceanographic processes. These processes regulate the distribution and the diversity of the fauna in a number of different ways, offering valuable comparisons to open slope environments. Canyons are hotspots of biodiversity, major pathways for the transportation and burial of organic carbon, and fast-track corridors for material transported from the land to the deep sea. Canyons act as temporary buffers for sediment and carbon storage. However, rapid, episodic flushing of canyons may mobilise large amounts of sediment, carrying it to the abyss and annihilating benthic ecosystems over a wide area. The frequency of these potentially catastrophic events and the fluxes of particles produced are largely unknown, as are the rates of recolonisation and restoration of the canyon ecosystems.
Our view of biological processes in canyons has changed considerably in the last few years because of the increased use of submersibles and ROVs. The results indicate the importance of various zooplankton groups acting as a link to fish and mammal populations. The species and their abundances differ from canyon to canyon and appear to be related to downward particle fluxes, topography and the hydrographic features of individual canyons. Canyons appear to be important in the channelling of macrophyte debris, which may have a significant effect on the relative abundance of some species. Few studies of the chemistry of canyons have been carried out, even though canyons play a crucial role in the redistribution of carbon and anthropogenic materials derived from marine primary production and terrestrial runoff. Because canyons channel and focus sediment distribution, anthropogenic tracers are relatively high in relation to surrounding slope areas. Canyons are being considered as potential disposal sites for various wastes, including carbon dioxide. These plans assume that canyons are isolated from the adjoining continental slope. We will test this assumption and determine the degree of interconnectivity between canyons and the open slope.
The aim, of our canyon studies is to compare and contrast key canyon systems distributed along the European Atlantic and Mediterranean ocean margins. We will do this by comparing the species richness and community structure of benthic communities both within and between canyons and relate these to environmental factors: physical (e.g. current regime), geological (e.g. sediment transport and grain size) and biogeochemical (input of organic matter and pollutants). We will determine whether canyons act as refugia, for instance as areas for fish aggregation and spawning, and whether they act as larval sources and sinks for other ocean margin ecosystems, including deep-water corals. In addition, we aim to determine why only some canyons act as feeding grounds for cetaceans. The overall aim is to provide the scientific context for broad management plans for European canyon systems. This is important in habitat conservation, the potential disposal of carbon dioxide, fisheries management, and in assessing the long-term effects of materials derived from terrestrial run-off that are transported to deep water by canyons.
Cold seep ecosystems
Cold-seep ecosystems have only recently been discovered on European margins where they occur in a variety of geological settings, including mud volcanoes, pockmarks and gas hydrates outcrops. The interplay between sea floor methane fluxes, other chemical compounds and sediment microbes favours carbonate precipitation and colonisation of these habitats by exceptionally rich benthic communities fuelled by chemical energy. These dense and endemic communities rely mainly on symbiosis with chemotrophic bacteria that produce large amounts of organic carbon through chemosynthesis. The presence of these unique ecosystems in regions of low animal density highlights the crucial role of local resource enrichments on benthic community composition and productivity.
To increase our understanding on the structure and dynamics of seep communities, we need to answer several questions including: how do environmental factors influence community structure? What are the chemical fluxes at the sediment interface? What are the interactions between abiotic and biotic factors? What is their role in substratum modification? The functioning and dynamics of such ecosystems and their role on earth climate and in element cycling are mostly unknown and are also important questions to address. Knowledge of the global carbon balance is incomplete without a systematic consideration of the amount of carbon cycled through biological processes. Until recently, the oceans were regarded primarily as a carbon sink, but the emerging role of the oceans as a source through methane advection has become an important research topic. Methane is an important greenhouse gas and understanding the interaction between physical, geological and biological regulation mechanisms for methane is critical for predicting climate change.
Anoxic ecosystems
Microbes occur in every niche in the ocean and comprise a significant part of the global biomass. In some continental margin ecosystems they dominate life almost exclusively, generating a great diversity of bacteria, archaea and some single cell eukaryotes. Natural chemical laboratories occur in areas of subsea discharge of fluids and gas (e. g. methane). These microbial communities and their symbiotic associates are nourished by the chemical energy rising from these sources and form the basis of cold seep ecosystems. These often take the form of dense and endemic benthic communities, in which the high production of organic carbon sustains large size or typical animals and very high biomasses. In high methane flux areas, the benthic biomass produced through chemosynthetic processes can be 1,000 to 50,000 times greater than the biomass resulting from photosynthetic production. The remarkable abundance of specialised invertebrates like giant tube worms or bivalves is one of the most striking features of seep communities and one of the best ‘indicators’ of fluid emission at the sea floor.
Systems such as gas chimneys, pockmarks and mud volcanoes in the Black Sea, Eastern Mediterranean, Gulf of Cadiz and the Norwegian margin represent distinct geological structures which are excellent target areas for our research. Recent geomicrobiological research provides evidence for a variety of these ecosystems holding a great diversity and biomass of bacteria and archaea.
The main questions to be addressed in HERMES include: 1) What are characteristics and driving forces of active geological structures harbouring anoxic microbial ecosystems? 2) Are there unique key microorganisms and biogeochemical pathways involved in this biosphere-geosphere coupling? 3) What is the resilience and response to external forces and global significance of these geo-ecosystems?
Open slope ecosystems
There is increasing evidence that continental slope ecosystems around Europe represent one of the major repositories of all marine biodiversity. However, although local diversity is moderately well documented for certain taxa at certain sites, very little is known about diversity at large spatial scales. If the distribution of biodiversity on continental slopes is far from being clarified, our comprehension of the mechanisms driving biodiversity attributes and distribution is even more uncertain. Convincing evidence exists that small-scale patchiness permits a large number of similar invertebrates to coexist by specialising on different types of patches or different successional stages. However, depth and latitudinal patterns in diversity that have been previously described for different taxa are often contradictory and whether this variation reflects geographic variability or differences in the responses of taxonomic groups is far from clear. We still need to identify major factors/processes such as gradients of productivity, oxygen availability, sediment heterogeneity, grain size, mineralogical composition and hydrodynamic forcing as well as past and present disturbance events expected to control biodiversity production and accumulation at large spatial scale. Understanding the role of these factors is of paramount importance for predicting the effects of global changes on biodiversity and ecosystem functioning in the deep seas and for identifying strategies for the sustainable use of the deep-sea resources along Europe’s margin.
Our aim is to understand the environmental and biotic factors influencing biodiversity (species richness and community structure) on European continental margins. In particular, we will address why biodiversity should apparently be greatest at mid-slope depths. Geological disturbance by events such as landslides will be investigated. The research will involve biologists, sedimentologists, physical oceanographers and biogeochemists. In addition, the pan-European operations of HERMES will be used to determine the ranges of key species along the ocean margin and in relation to physical oceanographic and topographic boundaries.
HERMES Geographic Information System (GIS)
The project will collect a large amount of spatial data and draw heavily on existing datasets. All this data will be collated into a GIS package to provide for the first time an environmental database covering the entire European ocean margin. The HERMES GIS will include: an inventory of margin hotspots together with integrated sea floor maps at various scales and resolutions using state-of-the-art techniques and technology, including deep towed sidescan sonars, sub-bottom profilers, ROV and AUV mounted multibeams and camera systems. Recent advances in deep-water positioning systems now enable the acquisition of geo-referenced data gathered at a variety of scales (ranging from regional down to visual) and for them to be fully integrated in a GIS environment. The HERMES GIS will also include spatial and temporal hydrographic data enabling visualisation of watermass distribution and circulation patterns. The likely changes in hydrographic conditions at hotspots, related to changes in thermohaline circulation resulting from different global change scenarios proposed by Earth System Science models, will be constrained. Parameters identified as ecosystem drivers will then be input into simulations to forecast local ecosystem responses to global change using the inverse mass balance models developed elsewhere in the project.
Modelling and Policy Advice
The project extends beyond the basic research, mapping and habitat classification into ecosystem modelling and policy advice. The modelling is aimed at improving our ability to forecast the effect on ecosystems of natural and anthropogenic perturbations. The results of the modelling will serve to explore the effects on the ecosystems of natural and anthropogenic impacts.
Finally, we will attempt to integrate the scientific output of the project with socio-economics and legal research to underpin the development of a comprehensive European Ocean and Seas Governance strategy. It will be the first time that such an approach has been adopted on a pan-European scale for the deep sea. The intended outcome is to develop concepts and strategies for the sustainable use of offshore marine resources, while taking into account the negative impact of human activities.
The project began on the 1st April 2005 and will run for 4 years.
Habitat mapping and national sea floor mapping strategies in Canada
R. A. Pickrill and V. E. Kostylev
Geological Survey of Canada (Atlantic), Dartmouth, NS, Canada
As the twentieth century drew to a close Canadian ocean management policy and the supporting marine science within the federal government was entering an exciting new era. Competition for declining offshore resources, fishery collapse, and mounting public pressure for improved management, led the federal government to enact Canada’s Ocean Act. This visionary legislation lays the framework for precautionary, sustainable management of our offshore lands; encapsulating the principles of conservation and ecosystem based management, and laying the foundation for systematic habitat mapping.
Management of offshore lands has been constrained by a lack of high quality information on marine ecosystems. However, converging technologies of GPS and multibeam mapping demonstrated the benefits of the new sea floor mapping technology, and led to the development of a proposal for a national program to map Canada’s offshore lands. SeaMap, an interdepartmental initiative would establish standards and set national priorities for sea floor mapping. The program is yet to be funded. But, the SeaMap proposal demonstrated a need and many of the underlining principals are guiding sea floor mapping and research directions within Natural Resources Canada and the Department of fisheries and Oceans over the ensuing years.
In 2002 research in NRCan was reorganised to improve alignment with government priorities; the resulting Geoscience for Ocean Management Program (GOM, www.gom.nrcan.gc.ca) acknowledged the role that sea floor mapping can contribute to habitat mapping and environmental stewardship. With one of the largest offshore territories, a relatively small population base, and a severe marine environment, Canada faces challenges to implement integrated and sustainable management of our offshore lands. Through a series of stakeholder workshops priority areas of national importance have been identified, while a habitat mapping strategy has been developed to optimise program outputs.
Three systematic approaches to habitat mapping have been developed;
1. High resolution regional mapping of seabed geology and habitats, based on acoustic surveys and groundtruthing (e.g. fishing banks)
2. Targeted high-resolution mapping of seabed features of value for conservation and fishery, and impacted marine habitats (e.g. sponge reefs, dump sites)
3. Broad-scale habitat mapping based on deterministic modeling of geological and oceanographic controls on benthic fauna (e.g. shelf-wide mapping) and extrapolation of local models to regional applications (e.g. Beaufort Sea habitat mapping).
The model applied in a particular project being defined by geographical extent, ability to collect new data, environmental constraints, the time frame and stakeholder needs, yet always building toward a national framework.
Recent applications of geological information in the selection
of candidate marine protected areas in Australia
Peter T. Harris
Marine and Coastal Environment Group, Geoscience Australia
Management of the marine environment in Australia’s EEZ is addressed by an Oceans Policy that was declared by the government in 1998. The Policy is being implemented through the generation of a series of regional marine plans (RMPs), followed by the selection of a network of representative marine protected areas (MPAs). The MPAs have multiple goals including fisheries management and the conservation of marine biodiversity. The southeast region of Australia has been the first part of the EEZ to undergo the RMP (in 2003) and MPA selection processes (currently in progress).
Abiotic geoscience information has been used extensively to provide crucial supporting information in these processes, to characterise habitats, bioregions and inform managers of the “representativeness” of different proposed MPA candidates. MPA candidates are first presented to stakeholders as “broad areas of interest” (BAOIs) that contain a representative suite of habitat types and include any rare or irreplaceable habitats. These are then reduced in area and borders are negotiated through stakeholder consultation supported by a scientific reference panel. The SE region contains 11 BAOI’s and so far stakeholder negotiations have been completed and MPAs nominated for two of these. In the deep-water, continental slope and abyssal areas, an interpreted map of 21 categories of different sea floor geomorphic features was used as a proxy for habitats. On the continental shelf, a “seascape” map (eg. Roff et al., 2003, Marine and Freshwater Ecosystems, 13(1): 77-90) was produced using multivariate analysis, which incorporated geomorphic features, water depth, tidal bed stress, wave-induced bed-stress, sediment grain size, sediment carbonate content, gravel content and mud content.
GIS analysis shows that the 11 broad areas of interest (BAOI) capture a representative sub-set of the geomorphic features that occur within the SE region. The two MPA’s, however, do not contain all of the feature types found within the larger BAOI. Similarly, the shelf seascapes contained within the BAOIs capture a representative sub-set of those that occur within the SE region. This experience has demonstrated that GIS analysis of abiotic data is an essential, valuable tool for selecting representative MPAs throughout the process of MPA network design and stakeholder consultation.
Video and multibeam observations of mega-benthic habitats in the Rockall Trough, Irish continental margin using a remotely operated vehicle; implications for managing deep-sea habitats
Janine Guinan1, Anthony Grehan1, Karine Olu-Leroy2, Margaret Wilson1, Colin Brown1
1) Department of Earth and Ocean Sciences,
National University of Ireland, Galway, Ireland
2) IFREMER, DRO-EP, Plouzané, France
A quantitative understanding of biological assemblages is a prerequisite to implementing sampling strategies and managing habitats. The management of vulnerable deep-sea habitats is important as human activity at continental margins increases e.g. deep-sea fishing, telecommunications cable routing and oil exploration.
Geo-referenced videographic datasets were collected during the first year of scientific use of the French remotely operated vehicle (ROV) Victor 6000 in the North East Atlantic. The main purpose of the cruise was to investigate carbonate mound structures (2-3 km in diameter rising 300 m above the seabed) and deep-sea coral communities previously identified in sonar records. Here we examine video datasets from ROV dives conducted in the SE and SW Rockall Trough, west of Ireland between depths 620-885 m. Multibeam data recently acquired by the Irish National Seabed Survey provided the regional bathymetry for the study locations.
A technique for the quantitative analysis of video datasets in deep-water surveys has been developed to study patterns of megabenthic habitats and deep-water corals, in particular the scleractinian coral Lophelia pertusa. Results of first trials of the SEABAT 8101/240khz multibeam system micro-bathymetry acquired with the Victor ROV are also presented.
Biological assemblages tend to exhibit significant change along physical (environmental) gradients in the deep-sea. These gradients include bathymetric relief, substrate type and hydrography. We have investigated quantitatively the hypothesis that cover of Scleractinian coral exhibits variability in relation to some or all of these environmental gradients at the scale of 10s of kilometres.
The coral cover variation was investigated (I) among transects within sites and (ii) among transects between sites. Distinct vertical patchiness was observed on carbonate mounds with dense coral cover associated with mound summits. The inter-mound seabed is characteristically depauperate of coral assemblages. Results show that mound summits occurring at similar depths at two sites exhibit variability in coral cover. One possibility is that the extent of this coral cover is related to increased current acceleration in the SW Rockall Trough.
Deep-water ROV surveys for scientific research can be costly and time consuming. A better understanding of the distribution of biological assemblages in relation to seabed morphology will greatly assist in constraining ROV survey planning and design to optimise vehicle bottom time.
Thematic maps for coastal planning
Oddvar Longva, Kari Helene Andresen, Ole Christensen,
Terje Thorsnes, and Aave Lepland
Geological Survey of Norway, Trondheim, Norway
Through the HASUT project a small area on the coast of Norway was mapped in detail regarding bathymetry, surface geology and biological diversity. This work is taken further as a Pilot study for Coastal Zone Management in the Aquareg Programme under the EU-programme INTERREG IIIC. The objective is to develop the "best practice" for management of the coastal zone, focusing on the development of aquaculture and coastal fisheries in Ireland, Spain and Norway. The pilot study will develop a suite of thematic maps for web-publication. Among the actual themes are depths, sediments, including properties like currents, deposition/erosion, anchoring and habitats. A first version of these maps will be presented.
The new British Geological Survey marine and coastal mapping
project: Recent progress
Alan Stevenson
British Geological Survey, Murchison House
The British Geological Survey has recently merged its marine, coastal and hydrocarbons research activities. The programme for the next 5 years will focus on delivering 3D mapping and modelling using multibeam and other high-resolution data that will address key questions related to the impacts of climate change and societal developments and will provide information required to define habitats, marine resources and conservation areas.
The proposed work is subdivided into four settings; estuaries and associated alluvium; open coast from the back of beach or cliff to wave base; continental shelf from wave base to shelf break and continental margins from the shelf break to deep-ocean base of slope. Data acquisition will concentrate on areas identified by stakeholders as being of importance to the UK science community, industry or marine managers. In particular, gaps in previous BGS reconnaissance mapping of the shelf areas include the coastal zone (to about 10m water depth), which now faces the most immediate pressures for environmental management and requires data for integrated coastal zone management. The coastal terrestrial, littoral and shallow marine settings exhibit high biodiversity, but because of the difficulties in charactering them, the extent and health of resources are poorly documented. Seabed sediment facies largely define the distribution of breeding, nursery and feeding grounds of many key species and, with additional turbidity and energy regime data, largely define nearshore marine landscapes.
The results of recent surveys in the nearshore zone and future plans will be presented at GeoHab 2005.
A quantitative approach for using multibeam sonar data to map benthic habitats
Curt E. Whitmire1, Robert W. Embley2, W. Waldo Wakefield1,
Susan G. Merle3, and Brian N. Tissot4
1) NOAA Fisheries – Northwest Fisheries Science Center, WA, USA
2) NOAA – Pacific Marine Environmental Laboratory, WA, USA
3) Cooperative Institute for Marine Resource Studies – Oregon State University, OR, USA
4) Washington State University Vancouver – Program in
Environmental Science, WA, USA
Dramatic declines in several species of demersal fishes off the U.S. west coast have resulted in the designation of eight commercially important species as being overfished. While the causes of those declines are not clearly understood, the fact remains that there is a dearth of abundance data for many groundfish species. One challenge in designing a systematic survey is that many species associate with heterogeneous substrata of varying relief. In many areas, the rugged sea floor topography precludes sampling by conventional techniques (e.g., bottom trawl). This has stimulated research that characterizes fish-habitat associations for the assessment of demersal fish species and the design of new survey methodologies.
Using spatial analytical techniques and a combination of data from remote sensing and in situ observations, three benthic habitat classes were mapped for a large rocky bank off the central Oregon coast known as Heceta Bank. Observational data from remotely operated vehicle (ROV) dives in 2000 and 2001 were used to establish habitat classes with seabed characteristics that have been statistically shown to correlate with demersal fish distributions. The observational habitat data were then extrapolated over the extent of a multibeam sonar survey conducted in 1998 using quantitative parameters derived from high-resolution bathymetric and acoustic backscatter imagery. The resultant map shows the predicted extents of three habitat classes: Rock Outcrop (high vertical relief), Boulder/Cobble (high acoustic reflectivity), and Mud/Sand (unconsolidated).
Groundfish distribution and bottom type in Hecate Strait
and Queen Charlotte Sound
Alan Sinclair1, Kim Conway2, Vaughn Barrie2, and Rick Stanley1
1) Fisheries & Oceans Canada, Pacific Biological Station, Nanaimo, BC, Canada
2) Geological Survey of Canada (Pacific), Sidney, BC, Canada
Associations between groundfish species spatial distribution and the surficial geology of Hecate Strait and Queen Charlotte Sound off the west coast of Canada were examined. The fish distributions were derived from commercial bottom trawl and research trawl survey catches. The species list includes elasmobranch, gadid, rockfish and sole species. The species distributions are overlaid on maps of surficial geology determined from seismic profiles, sidescan sonar, sediment samples and core samples. Five geological units have been determined, including bedrock, till, mud, and sand and gravel. These units are subdivided further. Associations between fish distributions and geology were examined using contingency analysis and ordination techniques.
Three main fish/surficial geology groups emerged. One consisted of species with relatively shallow depth distributions over thick transgressive sand and gravel bottom types or thin sand and gravel over bedrock. The species included big eye skate, spotted ratfish, English sole, Pacific cod, lingcod, Pacific halibut, petrale sole, and rock sole. A second group included species with slightly deeper depth distributions over a broader range of bottom types with more mud and less transgressive sand and gravel. The species in this group included arrowtooth flounder, long nose skate, spiny dogfish, Dover sole, rex sole, and sablefish. The third group included rockfish species with depth distributions overlapping the second group. The surficial geology was dominated by relatively hard till, bedrock, and transgressive sand over bedrock, with varying degrees of mud.
The associations between species distributions and surficial geology are confounded by depth. The geology is dominated by trangressive sand and gravel at depths up to 125 m while muds dominate at depths over 200 m and there is a clear progression between these dominant bottom types at intermediate depths. Individual species also occupy specific depth ranges. Species distributions by both depth and bottom type were further examined to identify species which simply occupied the available bottom types and those which selected specific bottom types.
Benthic habitat mapping prior to removal of
the Elwha Dam; preparing for change
Guy Cochrane, Jonathan Warrick, and Jodi Harney
Coastal and Marine Geology Program,
U.S. Geological Survey, California, USA
Two dams on the Elwha River of the Olympic Peninsula are currently slated for removal in early 2008. Dam removal will expose more than 14 million cubic meters of mixed grain-size sediment deposited in the reservoirs behind the dams, which will erode naturally and be transported to the Strait of Juan de Fuca. Increased sediment supply to the Strait may mitigate the current erosional trend along the river delta and adjacent shoreline. Removal of the dam should improve spawning for native salmon. A preliminary map of sea floor-sediment texture, derived from recently collected sonar, video, digital bed sediment images, and grab samples shows the area offshore of Elwha River mouth is dominated by coarse sediment, ranging in size from sands to boulders. Increased fine-grained sediment supply may bury or alter these nearshore habitats for locally productive kelp beds and geoducks.
Application of seabed character interpretations to broad scale habitat mapping: A case study from the eastern English Channel
R. Coggan1, S. Philpott2, D. Limpenny1, W. Meadows1, S. Birchenough1 and S. Boyd1
1) The Centre for Environment, Fisheries and Aquaculture Science, UK
2) British Geological Survey, UK
Seabed character maps provide a potentially valuable starting point for mapping seabed habitats, as they delineate distinct areas such as gravel banks or sand wave fields that can then be targeted for ground truth sampling to determine the composition of their biotic communities. As such, they are a useful approach to assessing the impacts of aggregate dredging operations at the site-specific level, and for placing these in context over a broader spatial scale. Seabed character maps are normally derived by interpreting a sonar mosaic constructed from adjoining, parallel sidescan survey tracks. The mosaics contain a great deal of detail, and while this is appropriate for the high resolution mapping required at site-specific levels (up to ~50 sq km), it is somewhat excess to requirement for lower resolution mapping at larger spatial scales (around 500 sq km). This implies that significant cost savings can be made when mapping broad scale areas if a survey strategy can be identified that will deliver reliable seabed character maps based on less that 100% sidescan coverage.
We surveyed a 600 sq km area of the eastern English Channel, to build a series of sidescan lines representing progressively greater density of sidescan coverage (closer track spacing) and used subsets of these lines to produce interpolated seabed character maps based on 4 km, 2 km and 1 km track spacing. A fourth map contained a central corridor where full coverage (100%) had been achieved. The suitability of the maps for broad scale surveys was assessed by comparing their relative accuracy and precision. Maps based on 4 km and 2 km line spacing failed to identify some significant seabed regions that were apparent on the map derived from 1 km line spacing. This latter map represented a 50% density of sidescan coverage, and the delineations of seabed regions in the central corridor were only marginally improved by the availability of 100% coverage. It was concluded that 50% coverage, equating to 1 km line spacing, was the most cost-effective strategy for mapping broad scale areas.
Ground-truth samples collected during the sidescan surveys were used to validate the seabed characterisations and provide information on the distribution of benthic fauna. Direct observations, made with a towed camera sledge, showed seabed characters consistent with expectation. Sediment samples from Shipek and Hamon grabs confirmed the general substrate type, although the Shipek grab appeared to under sample the coarser elements of the sediment. Benthic infaunal communities (sampled by 0.1m2 Hamon grab) tended to map more closely to sediment type and seabed character than epifaunal communities (sampled by 2-metre beam trawl). The study provides guidance for the application of seabed character interpretations to broad scale habitat mapping that will be of benefit to marine spatial planning and resource management.
The use of habitat mapping tools in the assessment of the re-habilitation
of the seabed following marine aggregate extraction
D.S. Limpenny, S.E. Boyd, K.M. Cooper, and W.J Meadows
The Centre for Environment, Fisheries and Aquaculture Science, UK
The commercial extraction of marine aggregates in the U.K. began in the 1960s and peaked at around 23 million tonnes per annum in 1989. Since then, the quantities removed from the seabed have remained relatively steady. Public concern regarding the potential environmental impacts of this activity has grown in recent years, particularly in light of proposed extraction activity in the eastern English Channel. Previous research on rates of rehabilitation of seabed habitats has focused more on short-term experimental studies rather than longer-term recovery of commercially dredged sites. Therefore, there is limited information that is directly applicable to the impacts of commercial dredging operations in U.K. waters, where the lifetime of a typical production licence is at least 15 years.
This research was undertaken to assess the status of the seabed sediments and associated benthic fauna within and outside areas where dredging had ceased, and to conduct follow up sampling to monitor progress towards physical and biological ‘recovery’. Annual surveys were conducted between 2000 and 2003 at 4 relinquished extraction sites which provided a range of dredging histories and environmental settings for investigation during this study. These investigations used a combination of acoustic mapping (sidescan sonar, swathe bathymetry, acoustic ground discrimination) photographic and biological sampling techniques to assess the rate and degree of physical and biological recovery at a number of relinquished aggregate extraction sites around the English coastline.
This research has improved our understanding of the ecological effects of marine aggregate extraction in U.K. waters and has also allowed an examination of the likely factors responsible for observed differences in the recovery of U.K. extraction areas. The study was able to refine our understanding of the recovery process and offered the following key conclusions:
• The physical effects of dredging can last for more than 10 years after the cessation of the activity.
• The fauna within areas exposed to high levels of dredging can remain in a perturbed state for at least 7 years after dredging has ceased.
• In general, sediments and fauna collected within areas exposed to high levels of dredging were more variable than those collected in other areas and this may be a symptom of perturbed conditions.
• It is likely that dredging intensity, or an associated variable, is an important factor in determining the nature of succeeding benthic assemblages.
• The geographic location of the extraction sites and the percentage of sand at the seabed within the sites explained regional differences in the fauna, and consequently the results tend to be site specific.
This work was funded by the Department for Environment, Food and Rural Affairs, the Office of the Deputy Prime Minister and The Crown Estate and forms part of a wider portfolio of related research projects undertaken by CEFAS.
Eastern English Channel large-scale seabed habitat maps:
Helping to support the sustainable management of offshore resources
S.L. Philpott1, J.W.C. James1, K.L. Howell2, C.M. Johnston2,
D.S. Limpenny3, J.E. Robinson4 and N.M. Simpson4
1) British Geological Survey, UK
2) Joint Nature Conservation Committee, UK
3) Centre for Environment, Fisheries and Aquaculture Research, UK
4) Marine Ecological Surveys Ltd, UK
This paper describes a 3 year programme which aims to provide integrated broadscale habitat maps in support of the sustainable management of offshore resources. The study covers approximately 4500 km2, within the central part of the Eastern English Channel. It is the intention of the study, which is in its initial stages, to produce habitat maps based on an inter-disciplinary approach, integrating geological, geophysical and biological data and interpretations, including new surveys using modern high resolution geophysical systems, ground truthed with sampling and video.
The immediate driver is the discovery of substantial aggregate resources in this area and the requirement to manage the sustainable development of this resource and minimise potential impacts. The area of resource also needs to be assessed within the broader context of the Eastern English Channel.
The project surveys and maps will allow us to distinguish between the habitats within this area, and therefore contribute to managing the whole resource sustainably, including considering parts of it for designation as Special Areas of Conservation (SACs) under the European Habitats Directive, and parts which may be suitable for resource exploitation. The project will also contribute towards improving the offshore sections of both the U.K. Marine Habitat Classification System (Conner et al., 2004) and the European Habitat classification system (EUNIS), through providing good quality epifaunal and infaunal data from a currently data poor habitat type. The project also aims to contribute to issues such as predicted impacts within the aggregate licence areas and their significance in a wider context. These issues can only be addressed with a knowledge of the resources, habitats and communities of the wider Eastern English Channel with which to compare those of the licence areas.
The primary output from this project will be the production of the first habitat and biotope maps for the Eastern English Channel. Using GIS to integrate the maps, this information will be used to identify and quantify the species and habitats, of both conservation and fisheries importance, that exist within the area and assess their significance in a wider regional context. All marine stakeholders will benefit from an opportunity to use these maps and associated survey data.
Variation of physical environments and habitats in the Hudson River Estuary
F.O. Nitsche1, R.E. Bell1, S. M. Carbotte1, W.B.F. Ryan1, A. Slagle1, and R. Flood2
1) Lamont-Doherty Earth Observatory of Columbia University, NY, USA
2) Marine Science Research Center Stony Brook University, NY, USA
As the human population of the planet moves towards coastal cities, major estuaries are crucial resources for transportation, commerce, and industrialization. To effectively manage these crucial resources detailed knowledge of the physical environment and habitats in estuaries is essential. Aiming to implement a science based management policy for the Hudson River Estuary the New York State Department of Environmental Conservation (NYSDEC) launched the Hudson River Estuary Benthic Mapping Project as part of their Hudson River Estuary Program.
As part of this project we have mapped the entire 240 km long Hudson River Estuary with the exception of several very shallow (<2 m) embayments. We have acquired full coverage high-resolution multibeam bathymetry and backscatter, as well as sidescan sonar data, both with <1 m resolution. Simultaneously, a dense network of sub-bottom profiles was acquired with line spacing of 80 m and 160 m in N-S and E-W directions respectively. In addition, we took over 400 sediment cores and 600 grabs to provide ground truth of the acoustic data and obtain detailed information on sediment lithology, physical properties and texture.
Integrating the different data sets using a Geographic Information System resulted in comprehensive and detailed substrate information. We created detailed maps of morphology, grain size distribution, and process-related sedimentary environments such as deposition, erosion/non-deposition, or sediment waves. The sediment grain size in the lower, marine-influenced part of the estuary is dominated by silt and clay; whereas the upper, fresh water dominated part of the estuary yields mainly sandy sediments. Local effects such as the contribution of tributaries, winnowing, and low-flow embayments modify this general pattern. In contrast to the grain size, the sedimentary environments vary strongly throughout the estuary. Although there is a local dominance of deposition at the estuarine turbidity maximum, there are usually large variations across the estuary. These variations most likely reflect differences in current strength, wave exposure, and morphology.
Although we have a good knowledge of the substrate as result of the benthic mapping, linking the different environments to actual habitats remains difficult. The differences in salinity result in different communities and make it difficult to apply a classification scheme entirely based on one acoustic data set to the whole system. High turbidity of the estuarine water makes it difficult or impossible to use standard biological investigations with divers, video, or photos to map distributions and composition of communities. Instead, we are using benthic samples from sediment grabs, observations from fishing, and sample catch studies by state and federal agencies.
The Outer Bristol Channel marine habitat study:
Interim results
J.W.C. James1, S.L. Philpott1, G.O. Jenkins1, A.S.Y. Mackie2,
T. Derbyshire2 and E.I.S. Rees2
1 British Geological Survey, Nottingham, UK
2 National Museums & Galleries of Wales, Cardiff, UK
3 University of Wales, Bangor, UK
The Outer Bristol Channel Marine Habitat Study has been designed to produce baseline biological and geological data, for an area of approximately 2400 km2 within the Bristol Channel, through an integrated survey programme.
A number of geophysical and biological sampling cruises have been undertaken. Equipment utilised includes multibeam, digital sidescan sonar, surface tow boomer. The results from the geophysical interpretation have been ground truthed by sea bed videos, photography and sampling. In total, 3000 line kilometres of multibeam data (including repeat lines), 1900 km of sidescan data, 150 km of surface tow boomer data and samples at 147 locations have been acquired. Videos at 12 locations across the study area have also been acquired.
The project is scheduled for completion in March 2006. The presentation gives an update on the progress to date and presents some of the interim results.
Benthic habitat mapping in Newman Sound – A Newfoundland Fjord
Alison Copeland1, Trevor Bell1, Evan Edinger2, John Shaw3, and Robert Gregory4
1) Department of Geography, Memorial University of Newfoundland, Canada
2) Departments of Geography and Biology, Memorial University of Newfoundland, Canada
3) Geological Survey of Canada - Atlantic, Bedford Institute of
Oceanography, Dartmouth, NS, Canada
4) Department of Fisheries and Oceans, St. John’s, Canada
This paper presents the results of a project to map the benthic habitats of Newman Sound, a fjord in eastern Newfoundland, Canada. The primary goal of the project was to assess the effectiveness and efficiency of using multibeam sonar to map habitats and biodiversity in a fjord environment. This assessment was carried out by groundtruthing the mapped multibeam backscatter and bathymetry. Newman Sound is a 32km long fjord divided into two basins by a shallow (11m deep) sill. Hydrography and the shape of the fjord suggest that circulation is primarily tidal, and the tidal range is 1m. Water temperatures are cool year round due to the influence of the Labrador Current; the fjord therefore contains a mostly boreal marine fauna with several arctic species.
Groundtruthing was conducted by collecting video imagery and benthic grab samples. These were combined with previously drawn maps and geophysical data to characterise benthic substrates and biota. Benthic grab samples were collected at 56 stations at water depths ranging from 4 to 312m. Video images were collected in shallow water using a drop camera (18 stations) and SCUBA video transects (9 stations). In deeper water (5 stations) an ROV was used. Sampling stations were chosen to represent a variety of backscatter values across a range of water depths.
Backscatter data indicated that the floor of the inner sound, a 60m deep basin, was covered by acoustically low reflectance substrate. Video and grab sample analysis showed organic-rich mud dominated by the tube dwelling polychaete Maldane sarsi. Silty mud was also found in large areas of the deep outer basin (maximum depth 320m) with similar backscatter values. This deepwater mud contained less organic material, and was sparsely inhabited by burrowing polychaetes and echinoderms. Bedrock exposed along the fjord showed abundant epilithic fauna, particularly the anemone Metridium senile. These habitats were difficult to sample, and were only represented by 2 video stations. Coarse textured substrates were more difficult to characterise as they appeared in various grain size combinations. These included muddy gravel in deep water (over 150m) with a rich diversity of burrowing and surface dwelling fauna, and shallow water cobble substrate dominated by macroalgae and encrusting fauna. Grab sampling on the inter-basin sill identified a rhodolith bed. This habitat was biologically the most diverse of those surveyed but was not acoustically distinguishable from gravel or cobble habitats.
In Newman Sound multibeam sonar was effective in mapping very low reflectance mud and sand substrates, as well as high reflectance bedrock exposures. Identifying coarse substrates with intermediate reflectance was more difficult, so more extensive groundtruthing in these habitats would be necessary to map them successfully. It is these coarse substrates which commonly contain the highest biological diversity, and therefore are of greatest interest for marine management and conservation.
Acoustic seabed classification and mapping of capelin
spawning habitats in coastal Newfoundland
Candace Rose-Taylor1, John T. Anderson2 and Trevor Bell1
1) Department of Geography, Memorial University of Newfoundland, Canada
2) Northwest Atlantic Fisheries Centre, Fisheries and Oceans Canada, Newfoundland, Canada
Historically capelin (Mallotus villosus) spawning in Newfoundland has been reported to occur on and near modern beaches. The only known demersal spawning occurred offshore on the Southeast Shoal of the Grand Bank of Newfoundland. Recently capelin have been observed spawning demersally several kilometers from shore in coastal northeast Newfoundland. These spawning sites are dominated by gravelly substrate, which in part may represent submerged beaches formed ca. 6000-9000 years ago when relative sea level was lower. As part of a multi-disciplinary study into the predator-prey dynamics of demersal capelin spawning in coastal Newfoundland, our goal is to use acoustic techniques to classify and map demersal capelin spawning habitats. In addition, we also intend to reconstruct submerged shorelines as a potential guide to spawning habitat. Normal incidence acoustic data (38 kHz) were collected at several sites where capelin spawning occurred. We used objective classification techniques and seabed bathymetric mapping to characterize capelin spawning habitats. We discuss the utility of these data to map the bathymetry and substrate composition of the seabed and to make predictions regarding potential demersal capelin spawning habitats.
Progress in mapping marine benthic habitats in the inland seas of the San Juan Islands, USA and Southern Georgia Strait, Canada – A major international effort
H. Gary Greene1, Vaughn Barrie2, Holly Lopez1, Janet Tilden1,
Charlie Endris1 and Brian Dieter1
1) Center for Habitat Studies, Moss Landing Marine Labs, Moss Landing, CA, USA
2) Geological Survey of Canada, Sidney, B.C., Canada
Recent habitat mapping efforts undertaken by the Geological Survey Canada, Pacific and the Center for Habitat Studies of Moss Landing Marine Laboratories has resulted in the comprehensive seafloor coverage of most of the inland seas of the San Juan Islands and southern Georgia Strait. After four years of mapping using the EM1002 95 kHz and EM3000 300 kHz multibeam bathymetric and backscatter data collected by the Canadian Hydrographic Service, we have nearly completed a major regional potential marine benthic habitat map for most of the trans-boundary region of Canada and the USA. This work has led to extensive quantification of habitat types that will be useful in the conservation and management activities of the region. We are presently embarking on documenting the habitat types through in situ observations using ROVs and seafloor sampling. In addition, the geology of the inland sea has been mapped with glacial features, dynamic bedforms and fault ruptured seafloor well defined. We will present seafloor images and interpretive maps that show in detail the complexities and diversity of substrate and morphology that form habitats.
Surficial geological habitat map of the Oregon and Washington