Widespread rocky reef occurrence in the central English Channel and the implications for predictive habitat mapping

Reefs are one of the marine habitats listed in Annex I of the European Union's Habitats Directive, which aims to establish a coherent European ecological network of Special Areas of Conservation. EU Member States are required to prepare and propose a national list of sites for evaluation under the scheme, but currently the occurrence of reefs in the United Kingdom's nearshore and offshore areas is not well documented. Here we report on our search for rocky reefs in the central English Channel, which unexpectedly revealed an extensive reef system covering an area of 1100 km². Prior to our work, it was generally perceived that the seabed in this area comprised mostly gravel, with a few isolated rock outcrops.Our approach to determining the location, extent and character of these reefs incorporated broad, medium and fine-scale analyses over a 3200 km² area of seabed, using single- and multi-beam acoustic data, ground-truthed by underwater video and stills imagery. A benthic terrain model was developed in ArcGIS to map topographic features at the broad and medium scales. Biotope assignments were made at the fine scale through detailed analysis of video footage obtained from 30 sampling stations. The study area has a complex geological history and lies at the centre of a major bedload-parting zone. Together, these strongly influence the seabed character and the distribution of biotopes. An integrated assessment of the physical and biological features was used to map the study area to level 4 of the EUNIS habitat classification system.Similar physical conditions exist in other areas of the UK continental shelf, raising the prospect of predicting where other rocky reef systems might occur. In the absence of a co-ordinated national seabed survey programme, such predictions, coupled with interpretation of existing single-beam bathymetry data, can help prioritise areas where limited survey resources could be most effectively deployed.     

A comparison of zoning analyses to inform the planning of a marine protected area network in Raja Ampat,Indonesia

Marine protected areas (MPAs) are often managed using several management zones, each of which allows different human-uses. Decision support tools can be applied to provide advice on potential zoning configurations. However, few studies used decision support tools to systematically determine good locations for different types of zones that accommodate multiple and often conflicting objectives. Previous studies have mostly used scores to integrate multiple objectives and identify different zoning configurations or explored priority areas for each zone separately. Neither of these approaches ensure that solutions meet both biodiversity and human-use objectives. Nor do they deal with the fact that in zoning plans the whole is not the same as the sum of the parts, the importance of a site depends on how the rest of the sites are managed. The aim of this study was to identify different zoning configurations for the Raja Ampat MPA network in Eastern Indonesia that address biodiversity, sustainable fisheries and community resource access objectives. Identifying zoning configurations is particularly difficult here given the importance of protecting high biodiversity reefs and other conservation values, and the high reliance of local communities on their marine resources. Potential areas for no-take zones were identified that have a small and equitable impact across the fishing grounds of different fishing communities whilst ensuring each community has access to a ‘sustainable fishing zone’. Access to fishing grounds for each community is complicated due to marine tenure restricting where individuals can fish and reliance on traditional types of fishing vessels that restrict long distance travel. This approach for zoning was compared to three others. The first focused on identifying areas only for the no-take zone, a traditional systematic planning approach, and the second on both zones without explicitly accounting for the issue of resource access for each community. The solutions unfairly impacted particular communities. Finally, it is demonstrated how a pre-existing zoning proposal, driven by negotiation can be integrated into systematic planning.     

Mapping benthic habitat in regions of gradational substrata: An automated approach utilising geophysical,geological, and biological relationships

The relationship between acoustic backscatter, sediment characteristics and benthic habitat is examined using high-resolution sidescan sonar data collected at the Loch Linnhe artificial reef site on the west coast of Scotland. The site is typical for the continental shelf of NW Europe, with a mix of seabed environments from muddy to coarse, stony substrata on a 10–100 m length scale. A sidescan sonar mosaic was produced and classified according to derived backscatter parameters (mean, median and standard deviation of the backscatter values) using an unsupervised classification procedure. The accuracy of the final classified map was assessed by comparison with a ground-truthing survey in which the biological habitat was derived from underwater video footage. The sidescan correctly predicted seabed surface characteristics of observed biological habitat with 78% accuracy. A second, and more challenging test of the acoustic data to correctly predict biological habitat was made by comparing it with data from 21 grab sampling stations. These stations were divided into three groups using multivariate statistical techniques based on their backscatter properties. Benthic assemblage structure was found to be significantly distinct between the high and low, and the medium and low backscatter stations. There was a low to moderate but significant correlation between the multivariate patterns of acoustic backscatter, benthic assemblage structure, and particle size distribution. The work shows that even in areas with subtle and gradational changes in substratum, the sidescan was able to predict biological community with an acceptable accuracy.     

Coastal and marine resource management in the Galapagos Islands and the Archipelago of San Andres: Issues,problems and opportunities

Tourism and fisheries comprise the economic backbone of the Galapagos Islands, Ecuador and the Archipelago of San Andres, Colombia. The health of fishery resources, the environment and their dependant industries is discussed against a background of policy development and user conflicts, supported by a range of technical studies undertaken between 1998 and 2002, setting the scene for an examination of a more participatory and effective role for local stakeholders in the management of their island resources. Local stakeholders have been involved in guiding plans on future management of both islands’ resources including Biosphere Reserve designation of the San Andres Archipelago and the development of a Special Law for Galapagos. Their participation is deemed essential to progress in marine resource management and zoning initiatives within the islands.     

基于生物资源的万山海洋牧场生境适宜性评估

万山群岛海域生态环境日益恶化、渔业资源持续衰退,因此建设万山群岛海洋牧场,修复海域生态环境、实现渔业资源可持续利用迫在眉睫。针对现阶段基于海洋生物资源的海洋牧场适宜性评估的研究较少,本研究利用渔业资源调查和全球物种数据库记录数据及13个环境因素数据,采用物种分布模型MaxEnt对选择的白姑鱼、日本金线鱼、红星梭子蟹和浅缝骨螺潜在分布区进行预测,探讨海洋生物地理分布与海洋环境因素之间的关系进而进行万山海洋牧场生境适宜性评估,结果表明:(1)各模型AUC值均大于0.9,说明构建的模型对这些物种潜在分布的模拟效果较好,后续可采用MaxEnt模型对4种生物的栖息地分布区进行预测;(2)海底浮游植物密度、海底温度以及海底硅酸盐浓度是影响这4种海洋生物栖息地分布的关键环境因子;(3)基于该4种海洋物种MaxEnt模型的HSI分布区所存在重叠区域来看,海洋牧场拟建设区域应为纬度21.85°N~22.15°N,经度113.6°E~114.2°E。研究结果可为万山海洋牧场规划和建设提供科学依据。     

Implications of defining fisheries closed areas based on predicted habitats in Shetland: A proactive and precautionary approach

During 2010 a set of 22 voluntary closed areas, distributed around Shetland, were proposed by local industry in order to help protect and conserve threatened habitats from potential physical disturbance from scallop dredging. Initially, closed areas were implemented on a precautionary basis over predicted beds of maerl and horse mussel (Modiolus modiolus) derived from historical data. Horse mussel and maerl beds are classed as priority habitats which have been identified as being threatened and requiring conservation under the UK Biodiversity Action Plan (UK BAP). Legalisation of the voluntarily adopted closed areas occurred in 2011. Detailed surveys were conducted to map each closed area with specific reference to the defining features located within. Closed areas were surveyed using a hull mounted multibeam system and ground-truthed with an underwater camera system. Information was imported to a Geographic Information System (GIS) in order to create georeferenced habitat maps of the two species of interest. The appropriateness of each closed area was assessed and a proposed methodology and procedure outlined for any future closed areas. The primary aim was to provide information on which to test the validity of initial closed area boundaries and subsequently allow managers to refine and add to them in the future. The survey illustrated the need to have good quality acoustic and visual survey work undertaken whenever areas have been closed based on historical data and/or predicted habitats. Predicted beds were not found to be representative of the survey findings. The survey highlighted the lack of good quality, robust, accurate, and up to date species information for the waters around Shetland, especially with regard to priority marine features. Although some were neither fully protecting the UK BAP habitats they were designed to protect nor were protecting any UK BAP habitats, a degree of protection had been conferred to some priority features in the first iteration of implementation of closed areas. Survey data were subsequently used to legally alter the closed area boundaries to more appropriately reflect the distribution of priority features. Recommendations were made on appropriate procedures for defining a species bed and on the wider implications of the study’s findings for other fisheries areas developing spatial management plans.     

Modelling the distribution of hard seabed using calibrated multibeam acoustic backscatter data in a tropical,macrotidal embayment: Darwin Harbour,Australia

Spatial information on the distribution of seabed substrate types in high use coastal areas is essential to support their effective management and environmental monitoring. For Darwin Harbour, a rapidly developing port in northern Australia, the distribution of hard substrate is poorly documented but known to influence the location and composition of important benthic biological communities (corals, sponges). In this study, we use angular backscatter response curves to model the distribution of hard seabed in the subtidal areas of Darwin Harbour. The angular backscatter response curve data were extracted from multibeam sonar data and analysed against backscatter intensity for sites observed from seabed video to be representative of “hard” seabed. Data from these sites were consolidated into an “average curve”, which became a reference curve that was in turn compared to all other angular backscatter response curves using the Kolmogorov–Smirnov goodness-of-fit. The output was used to generate interpolated spatial predictions of the probability of hard seabed (p-hard) and derived hard seabed parameters for the mapped area of Darwin Harbour. The results agree well with the ground truth data with an overall classification accuracy of 75% and an area under curve measure of 0.79, and with modelled bed shear stress for the Harbour. Limitations of this technique are discussed with attention to discrepancies between the video and acoustic results, such as in areas where sediment forms a veneer over hard substrate.     

Phase-reversed seabed reflections in seismic data: examples related to mud volcanoes from the South Caspian Sea

The sediment–water interface is usually marked by an increase in acoustic impedance and is therefore displayed in a seismic section as a positive polarity reflection. Here, we use the term “seabed phase reversal” to describe areas of seafloor which are instead expressed as a negative polarity reflection in seismic data. We describe in detail a number of examples of seafloor phase reversals and use a simple one-dimensional geophysical model to test the hypothesis that they are the result of the presence of gas within the seafloor sediment. Our examples are all related to seismically imaged mud volcanoes located within the South Caspian Sea. Sections of phase-reversed seafloor at the summit area of these volcanoes have been mapped to reveal the existence of seafloor mud pools (salses) and recently erupted mud flows which show a strong similarity to smaller-scale features at onshore volcanoes in Azerbaijan. Synthetic geophysical modelling indicates that under the physical conditions likely to occur when the seabed sediment is gas-bearing, the seafloor will be expressed as a strong negative polarity reflection. Unlike other indicators of seafloor gas, such as pockmarks, which merely record the transient expulsion of fluids from sedimentary basins, seafloor phase reversals indicate the presence of gas in marine sediment at the time of survey acquisition. They therefore are of significance to engineering and site survey operations as well as the identification of biological communities and gas flux calculations.     

南黄海西部地区浅层气地震特征

通过近年来南黄海西部地区的浅层地震调查,发现该地区浅层气地震特征丰富而多变,特别是多处海底面、海水层中的浅层气地震记录,揭示本区存在较多浅层气,且部分浅层气由海底逸出,释放到海水层中。该区的浅层气地震特征按空间位置分为3大类:(1)地层中的特征:声学空白、声学幕、声学扰动、不规则强反射顶界面、两侧相位下拉;(2)海底面的特征:海底麻坑、大型塌陷坑;(3)海水层中的特征:声学羽流、云状扰动、点划线反射。选择相应特征的典型浅层气地震记录,进行了声学成因解释,讨论了大型塌陷坑的浅层气成因、海水层中声学反射与浅层气体的成因关系以及浅层气地震特征的气体浓度指示作用。根据南黄海西部地区浅层气地震特征,绘制了该区的浅层气分布图。     

Remote Acoustic Habitat Assessment Techniques Used to Characterize the Quality and Extent of Oyster Bottom in the Chesapeake Bay

Underwater acoustic technologies may be used for remote sensing of estuarine and coastal benthic habitat in addition to more traditional methods of assessing the seabed. These systems use reflected sound energy to identify surface objects, texture, and subbottom density discontinuities, and to classify benthic habitat. We evaluated the ability of subbottom profiling systems, side scan sonar, and acoustic seabed classification systems (ASCS) to assess oyster habitat in the Chesapeake Bay. Our criteria were the systems' abilities to assess the quality and quantity of oyster shell resources and to integrate with Geographical Information Systems (GIS) technology for the charting of the seabed. Although all systems examined have previously been used for benthic habitat assessment, we found that ASCS offered the most promise as a stand alone system for mapping complex and heterogeneous habitat typical of oyster bottoms. The results from this study suggest that ASCS technology is highly suited for the identification and charting of oyster shell as well as distinguishing among different combinations of shell and fine sediments. Such systems also offer excellent linkage with GIS display and analysis capability.     

Remote Acoustic Habitat Assessment Techniques Used to Characterize the Quality and Extent of Oyster Bottom in the Chesapeake Bay

Underwater acoustic technologies may be used for remote sensing of estuarine and coastal benthic habitat in addition to more traditional methods of assessing the seabed. These systems use reflected sound energy to identify surface objects, texture, and subbottom density discontinuities, and to classify benthic habitat. We evaluated the ability of subbottom profiling systems, side scan sonar, and acoustic seabed classification systems (ASCS) to assess oyster habitat in the Chesapeake Bay. Our criteria were the systems' abilities to assess the quality and quantity of oyster shell resources and to integrate with Geographical Information Systems (GIS) technology for the charting of the seabed. Although all systems examined have previously been used for benthic habitat assessment, we found that ASCS offered the most promise as a stand alone system for mapping complex and heterogeneous habitat typical of oyster bottoms. The results from this study suggest that ASCS technology is highly suited for the identification and charting of oyster shell as well as distinguishing among different combinations of shell and fine sediments. Such systems also offer excellent linkage with GIS display and analysis capability.     

Zoning design for cross-border marine protected areas: The Red Sea Marine Peace Park case study

In marine protected areas (MPAs), zoning schemes can help balance multiple resource uses. Literature on ocean zoning design methods points out the need for analytical tools that guarantee stakeholder involvement and that address the unique spatial characteristics of the sea, especially under multiple jurisdictions. I illustrate the use of a method of spatial multi-criteria analysis (MCA) that combines data of the land and ocean environment with stakeholder preferences to identify areas most suitable for varying levels of protective zoning. To solicit preferences, I apply social science survey techniques at an early stage in the process. I synthesize the resulting preferences with physical data using a geographical information system. This comprehensive approach addresses some of the challenges of designing zoning for a cross-border, multi-jurisdictional MPA such as varying levels of information between countries, limited cooperation between managers and scientists, differing statutory regimes, and difficulties bringing stakeholders together to solicit their opinions. As a case study, I developed a zoning proposal for the Red Sea Marine Peace Park (RSMPP), a proposed MPA to be jointly managed by Jordan and Israel in the northern Gulf of Aqaba.     

Seafloor habitat definition for spatial management in fisheries: A case study on the continental shelf of southeast Australia

The importance of habitat to fisheries production on Australia's southeast continental shelf is part of a five-year study of ecosystem functioning and its implications for a sustainable fishery. Benthic habitats from 40 m to ∼200 m were studied, based on identification of suitable sites from local fishers' information. Results presented here concentrate on data from a single mesohabitat at 40–60 m depth collected over two days. Macrohabitats within this mesohabitat were discriminated as soft, hard and rough from visual inspection of acoustic echograms. Subsequent analysis of the return echoes using roughness and hardness indices did not significantly improve real-time visual discriminations. Macrohabitats were sampled with an underwater video camera, sediment sampler, benthic sled, demersal trawl, gillnets and fish traps to relate the acoustic classifications to biological habitats. There were distinct differences in the benthic and fish communities between macrohabitats discriminated by acoustics. We concluded that discrimination of habitats from visual inspection of echograms, plus limited verification with physical sampling, could provide sufficient information for spatial management. However, successful management of individual species, the fish community and the ecosystem requires an understanding of the association of fishes with habitat at the macrohabitat and mesohabitat level, and its variability through time.     

Bloom of the Yessotoxin producing dinoflagellate Protoceratium reticulatum (Dinophyceae) in Northern Chile

Potential spawning habitat is defined as the area where environmental conditions are suitable for spawning to occur. Spawning adult data from the first quarter (January–March) of the International Bottom Trawl Survey have been used to study the inter-annual variability of the potential spawning habitat of North Sea plaice from 1980 to 2007. Generalised additive models (GAM) were used to create a model that related five environmental variables (depth, bottom temperature and salinity, seabed stress and sediment type) to presence–absence and abundance of spawning adults. Then, the habitat model was applied each year from 1970 to 2007 to predict inter-annual variability of the potential spawning habitat. Predicted responses obtained by GAM for each year were mapped using kriging. A hierarchical classification associated with a correspondence analysis was performed to cluster spawning suitable areas and to determine how they evolved across years. The potential spawning habitat was consistent with historical spawning ground locations described in the literature from eggs surveys. It was also found that the potential spawning habitat varied across years. Suitable areas were located in the southern part of the North Sea and along the eastern coast of England and Scotland in the eighties; they expanded further north from the nineties. Annual survey distributions did not show such northward expansion and remained located in the southern North Sea. This suggests that this species' actual spatial distribution remains stable against changing environmental conditions, and that the potential spawning habitat is not fully occupied. Changes in environmental conditions appear to remain within plaice environmental ranges, meaning that other factors may control the spatial distribution of plaice spawning habitat.     

Inter-annual variability of North Sea plaice spawning habitat

Potential spawning habitat is defined as the area where environmental conditions are suitable for spawning to occur. Spawning adult data from the first quarter (January–March) of the International Bottom Trawl Survey have been used to study the inter-annual variability of the potential spawning habitat of North Sea plaice from 1980 to 2007. Generalised additive models (GAM) were used to create a model that related five environmental variables (depth, bottom temperature and salinity, seabed stress and sediment type) to presence–absence and abundance of spawning adults. Then, the habitat model was applied each year from 1970 to 2007 to predict inter-annual variability of the potential spawning habitat. Predicted responses obtained by GAM for each year were mapped using kriging. A hierarchical classification associated with a correspondence analysis was performed to cluster spawning suitable areas and to determine how they evolved across years. The potential spawning habitat was consistent with historical spawning ground locations described in the literature from eggs surveys. It was also found that the potential spawning habitat varied across years. Suitable areas were located in the southern part of the North Sea and along the eastern coast of England and Scotland in the eighties; they expanded further north from the nineties. Annual survey distributions did not show such northward expansion and remained located in the southern North Sea. This suggests that this species' actual spatial distribution remains stable against changing environmental conditions, and that the potential spawning habitat is not fully occupied. Changes in environmental conditions appear to remain within plaice environmental ranges, meaning that other factors may control the spatial distribution of plaice spawning habitat.     

The impact of scour processes on a smothered reef system in the Irish Sea

The Irish Sea, like many marine areas, is threatened by anthropogenic activities. In particular the Pisces Reef system, a series of smothered rocky reefs are subject to fishing pressures as a result of their position within a Nephrops norvegicus fishery. In an area of sediment deposition and retention the reefs modify the environment by increasing the energy of near-bottom currents which results in localised scouring. This is the first study to attempt to characterise and investigate the ecological functioning of the Pisces Reef system. A multidisciplinary approach was essential for accurate investigation of the area. To facilitate more effective management of the benthic habitats of the Reef system, this study integrates acoustic, seismic, grab sampling and video ground-truthing methods for benthic habitat discrimination. Orientation of the scour hollows also suggest that seabed features could be used to infer dominant flow regimes such as the Irish Sea Gyre. The data revealed significant geology–benthos relationships. A unique biotope was described for the reef habitat and it was demonstrated that scouring may influence community composition through disturbance mechanisms. This study provides preliminary information required for management of a unique habitat within a uniform region.     

海底沉积物物理参数的声学反演模式

声学反演方程是声学探测沉积物物理参数的基础方程。基于声学理论和统计理论的声速反演沉积物物理参数的两种模式,运用南海海底沉积物声学物理数据验证、比较了两种反演模式,以反演孔隙度、含水量为例,得出基于双参数经验方程反演模式的适用性较强,但精度有待于提高;基于声速理论的反演模式反演南海海底沉积物物理参数有待于进一步完善。     

Zoning strategies for marine protected areas in Taiwan: Case study of Gueishan Island in Yilan County,Taiwan

According to the United Nations (UN) Millennium Ecosystem Assessment, there has been a dramatic decline in global biodiversity. The UN has made a global appeal for all countries to mitigate their impact on the environment. Marine environmental protection is one of the most critical and urgent issues in the world and many countries have commenced establishing marine protected areas (MPAs) by implementing ecosystem-based management (EBM) concepts. MPA planning has been considered one of the simplest and most effective methods to protect marine environments. Taiwan has recently developed policies that have focused on its marine environment, and there are plans to increase the size of Taiwan׳s MPAs to 20% of its total ocean territory by 2020, thereby achieving a sustainable ocean. To achieve this goal, the government must address specific difficulties associated with the location of MPAs and relevant zoning strategies. This study establishes MPA protection principles and a zoning framework for MPAs in Taiwan by using Gueishan Island in Yilan County as a case study site to examine specific zoning strategies. The protection of 3 objectives (hydrothermal vents, cetacean, and fisheries resources) is discussed in this paper. Multi-criteria spatial analysis and a geographic information system are applied to identify the most crucial area to protect. To understand the stakeholders׳ opinions and concerns regarding the proposed zoning framework, this research conducted in-depth interviews with experts and stakeholders. MPAs zoning strategies are formulated at the conclusion of this study that could assist in protecting critical marine resources and avoiding conflicts among various usages of the marine area.     

The application of physical surrogates to predict the distribution of marine benthic organisms

The identification of marine habitats based on physical parameters is increasingly important for marine reserve design, allowing characterisation of habitat types over much wider areas than is possible from often patchy biological data. Marine management zones often contain a wide array of physical environments, which may not be captured in the biological sampling effort. The mismatch between biological and physical information leads to uncertainty in the application of bio-physical relationships at the broader management scale. In this study, a case study from northern Australia is used to demonstrate a methodology for defining uncertainties which result from the extrapolation of bio-physical associations across areas where detailed biological data is absent. In addition, uncertainties relating to the interpolation of physical data sets and that resulting from the cluster analysis applied to the physical data are calculated and mapped, providing marine managers with greater robustness in their analysis of habitat distributions.