GIS Modeling of Wave Exposure at the Seabed: A Depth-attenuated Wave Exposure Model

Bekkby, Trine; Isachsen, Pål Erik; Isæus, Martin; Bakkestuen, Vegar

doi:10.1080/01490410802053674

Cited by 41 publications

(31 citation statements)

References 24 publications

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“…Simple indices are based on the number of angular sectors open to waves (the 'Baardseth Index'; Baardseth 1970). More complex indices are based on the summed distance to the nearest land in angular sectors, weighted by incidence and speeds of wind in those sectors, and can be modified by the presence of shallow water close inshore (Thomas 1986) and wave refraction effects (Bekkby et al 2008).The development of geographical information systems (GIS) and the ready availability of computing power have made automated calculation of numerical wave exposure indices feasible and desirable. While such indices remain a substitute for estimates of wave climate, as can be delivered by physical models (Booij et al 1999) and direct or indirect measurements (Jones & Demetropoulos 1968, Friedland & Denny 1995, they have real value as predictors of the structure of biological communities (Burrows et al 2008), effects of wave action on single species (Isaeus 2004) and the outcome of interactions (Jonsson et al 2006).…”

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confidence: 99%

Influences of wave fetch, tidal flow and ocean colour on subtidal rocky communities

Burrows¹

2012

Mar. Ecol. Prog. Ser.

104

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Community assemblages on subtidal rock change markedly along gradients of wave energy, tidal flow, and turbidity. The importance of these assemblages for rare and delicate species, for shellfish, as nursery areas for fish, and for their contribution to ecosystem functioning in coastal areas has prompted much conservation effort in many countries. I applied a rapid method of calculating a large high-resolution (200 m scale) map of wave exposure < 5 km from the UK coastline to compare with UK subtidal biodiversity records from diver surveys from the 1970s to the 2000s. Satellite-derived estimates of ocean colour, and tidal flows from hydrodynamic models were also extracted for each site. Ordinal logistic regression of categorical abundance data gave species-distribution patterns with wave fetch and depth and dependence on chlorophyll and tidal flows: macroalgae declined with increasing chlorophyll and increased with tidal flow. Multivariate community analysis showed shifts from algae to suspension-feeding animals with increasing depth and in areas of high chlorophyll and tidal flow and a change from delicate forms in waveshelter to robust species at wave-exposed sites. The strongest positive influence on species diversity was found to be the presence of the kelp Laminaria hyperborea: sites with 0% cover had a median of 6 species, while those with > 40% cover had a median of 22 species. Laminaria hyperborea, and the most diverse communities, is found in areas of estimated low chlorophyll concentrations and in the most wave-exposed environments, which are often but not always in areas of high tidal flow.KEY WORDS: Wave fetch · Wave exposure · Subtidal rock · Community structure 445: 193-207, 2012 present both problems and opportunities for a wide variety of marine organisms, and the biomechanical implications for living in a wave-beaten environment are relatively well understood (Denny 1988). Direct negative effects are on the structural integrity of attached animals and plants being torn apart by drag forces (Friedland & Denny 1995), broken through repeated flexing (Mach et al. 2007) or smashed by wave-borne debris (Shanks & Wright 1986), and on the ability of mobile species or settling stages to remain attached to the rock (Vadas et al. 1990). Positive effects of waves are harder to find, but waveinduced water flow can increase the supply of (1) food to suspension feeders, and thence enhances growth rate (Burrows et al. 2010); (2) larvae to the rock surface and thence enhances settlement rate (Burrows et al. 2010); and (3) nutrients to growing algae (Dayton 1985). (4) At the community level, increased environmental stress in extreme wave exposure may give tolerant species a refuge from competition and predation (Menge & Sutherland 1987). Varying exposure to different levels of wave flow can result in changes in growth forms that help adapt to life in fast-moving water. Animals grow more robust shells and devote more resources to attachment (Crothers 1983), while plants may change frond morphology to r...

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Influences of wave fetch, tidal flow and ocean colour on subtidal rocky communities

Burrows¹

2012

Mar. Ecol. Prog. Ser.

104

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Section: Discussionmentioning

confidence: 99%

“…No attempt was made to specifically account for water depth at a site. This model however, could easily incorporate depth following the work of Bekkby et al (2008) if a sufficiently large depth range is present in the study area or the sites of interest.While our study is focused on algal communities associated with shallow temperate reefs, exposure is an important force shaping a range of marine communities, and fetch-based indices should be equally applicable to ecological questions involving other assemblages in temperate and tropical waters (e.g. Fulton & Bellwood 2004).…”

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Quantifying wave exposure in shallow temperate reef systems: applicability of fetch models for predicting algal biodiversity

Hill¹,

Pepper²,

Puotinen³

et al. 2010

Mar. Ecol. Prog. Ser.

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Management and conservation of ecosystems relies on biodiversity data; however, broad-scale biological data are often limited. Predictive modelling using environmental variables has recently proven a valuable tool in addressing this gap. Wave exposure is a particularly important environmental variable that structures shallow reef systems, but it is rarely quantified across the large areas often used for predictive studies. Therefore, we investigated approaches that quantify exposure and can be readily applied across a large area. We generated 6 quantitative indices that emphasise different aspects of exposure using a numerical wave model and cartographic fetch models. The utility of these indices for predictive modelling in shallow temperate reef systems was assessed by how well they explained community and genera-level algal patterns in Tasmania, Australia, which is a region that experiences a wide range of wave exposure conditions. Exposure indices were significant predictors of algal patterns, explaining up to 18% of community level patterns and up to 37% of the variance associated with the occurrence and cover of algal genera. Fetch-based indices in particular appear to be a viable option for quantifying exposure on shallow reefs. These indices can be generated within a Geographic Information System (GIS) program for specific sites of interest, along coastlines or on a grid, and are potentially accessible to ecologists. Quantification of exposure across broad regions using fetch indices will allow ecologists to makes advances in predictive modelling studies, but also facilitate studies that test the generality of hypotheses and mechanisms driving patterns previously observed using qualitative measures.KEY WORDS: Wave exposure index · Cartographic fetch modelling · Macro-algae · Biodiversity · Predictive models Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 417: [83][84][85][86][87][88][89][90][91][92][93][94][95] 2010 tion of shallow reef communities requires knowledge of biodiversity patterns across large regions. Because collecting biological data is labour intensive, difficult and expensive for the large areas relevant to management, these data are often limited and patchy. Where biological data are limited or lacking, predicting patterns of biodiversity using relationships between biodiversity and physical variables can facilitate conservation decision-making (Lehmann et al. 2002, Beger & Possingham 2008, Foster & Dunstan 2010.A range of physical data is now available across large regions to aid in the development of predictive models for the marine environment. These include data on sea surface temperature or ocean colour from satellites (e.g. MODIS and SeaWiFS) or Argo floats, ocean chemistry measurements (e.g. CSIRO Atlas of Regional Seas, CARS; Condie & Dunn 2006), bathymetry (e.g. Whiteway 2009) and sediment grain-size data (e.g. Marine Sediment database, MARS; Geoscience Australia). While these physical data have proven useful for ecosys...

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“…Baxter et al (2008) reviewed the status of Scottish seas and established a spatial baseline against which future marine and coastal policy can be measured and modelled. GESAMP (2001) noted that this type of spatial modelling approach was appropriate for locating aquaculture operations and was highly suited to maximizing sustainable economic return without environmental detriment, confirming the notion that the initial selection of the most appropriate sites will help prevent negative downstream effects on a farm's success and ensure long-term sustainability and environmental resilience.…”

Section: Discussionmentioning

confidence: 99%

Using physical environmental parameters and cage engineering design within GIS-based site suitability models for marine aquaculture

Falconer¹,

Hunter²,

Scott³

et al. 2013

Aquacult. Environ. Interact.

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Defining the physical suitability of an area for marine cage fish farming is of great importance, as each cage type has its own engineering tolerance levels and is designed to cope with a certain range of environmental conditions. Currently, there are no definitive, objective methods used to evaluate the suitability of coastal and offshore sites with respect to the physical limits of the location and the engineering design of a specific cage type. This study developed models which incorporate physical environmental parameters and cage engineering design within a GIS (graphical information system) environment, providing a valuable decision support tool for farmers, regulators and policy makers. The Western Isles of Scotland, UK, were selected as a study area due to the wide range of coastal and offshore environments. In addition, we selected 4 cage types designed for different wave exposure conditions (sheltered, moderately exposed, exposed and offshore). The models have been developed for worst-case scenarios, such as maximum significant wave height, conditions which are often difficult to predict. As shown in this study, the models can be used to assess the risk of using the selected cage type in a certain area and to highlight specific locations for development. The results indicate there is scope for further expansion of the aquaculture industry in the Western Isles using cages designed for exposed and offshore conditions, whereas there is limited potential for new developments using cages designed for moderately exposed environments. This allows stakeholders to make a robust decision about what cage type to use and where to locate it.

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GIS Modeling of Wave Exposure at the Seabed: A Depth-attenuated Wave Exposure Model

Cited by 41 publications

References 24 publications

Influences of wave fetch, tidal flow and ocean colour on subtidal rocky communities

Influences of wave fetch, tidal flow and ocean colour on subtidal rocky communities

Quantifying wave exposure in shallow temperate reef systems: applicability of fetch models for predicting algal biodiversity

Using physical environmental parameters and cage engineering design within GIS-based site suitability models for marine aquaculture

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