Measuring fragmentation of seagrass landscapes: which indices are most appropriate for detecting change?

Sleeman, Jai C.; Kendrick, Gary A.; Boggs, Guy S.; Hegge, Bruce

doi:10.1071/mf04300

Cited by 44 publications

(42 citation statements)

References 51 publications

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“…Hargis et al (1998) found that this mea-sure, like many others, was related in a linear fashion to increasing fragmentation, up to 40% disturbance of a landscape. Sleeman et al (2005) extended the analysis of fragmentation from simulated to more realistic patterns of fragmentation in eelgrass, but did not evaluate a fractal metric. Like Hargis et al (1998), these authors found that measures are highly correlated over a range of fragmentation, with no single preferred measure.…”

Section: What Generates the Parabolic Relationship Of Fish To Eelgrasmentioning

confidence: 99%

Fractal measures of habitat structure: maximum densities of juvenile cod occur at intermediate eelgrass complexity

Thistle

Schneider²,

Gregory³

et al. 2010

Mar. Ecol. Prog. Ser.

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Habitat patchiness is known to alter the relation of a population to both its predators and its prey. We developed a biologically interpretable measure of habitat complexity to test whether juvenile fish density depends on degree of patchiness. In Newfoundland coastal waters, juvenile fish species, including Atlantic cod Gadus morhua, are associated with eelgrass Zostera marina. However, the association of density with eelgrass cover is dependent upon site and the scale of analysis. We tested for non-monotonic relationships (with an intermediate optimum) between 5 spatial characteristics of eelgrass and density of 3 juvenile (Age-0) fish species: Atlantic cod, Greenland cod G. ogac, and white hake Urophycis tenuis. We used aerial photography to determine eelgrass perimeter and area measurements at multiple scales, fractal dimensions of perimeter (D P ) and area (D A ), and a measure that combines perimeter and area complexity at these scales (β P/A ) . Fish densities were estimated at each site using a seine net. We found parabolic relationships between β P/A and density for all 3 species, indicating highest fish densities at sites of intermediate patchiness and edge regularity. Furthermore, we determined that β P/A provided a less ambiguous estimate of spatial configuration than other measures. This intermediate maximum may reflect a trade-off, whereby eelgrass sites of intermediate spatial complexity provide juvenile fish with both optimal protective cover and opportunity to feed. This pattern may apply to any species requiring open areas in which to forage as well as shelter to offset predation risk.

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Section: What Generates the Parabolic Relationship Of Fish To Eelgrasmentioning

confidence: 99%

Fractal measures of habitat structure: maximum densities of juvenile cod occur at intermediate eelgrass complexity

Thistle

Schneider²,

Gregory³

et al. 2010

Mar. Ecol. Prog. Ser.

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“…We acknowledge that other authors [40,66,74,75] successfully estimated those seascape metrics, and their experience has been fundamental for the selection of parameters in this study. For example, Hawkins and Hartnoll [74] estimated the species richness in intertidal benthic communities and highlighted the importance of calibrating the sample area based on the organism dimensions.…”

Section: Discussionmentioning

confidence: 99%

“…The results indicated that the set of metrics used to characterize a coral reef must be defined and tailored to the case study area. Sleeman et al [75] tested several metrics on seagrass meadow and reported the importance of defining a standard area for a meaningful interpretation of the ecological relevance of the metric. Garrabou et al [40] investigated the spatial and temporal dynamics on rocky bottom benthic communities and successfully introduced the novel used of a set of area-perimeter-edge, shape, contagion interspersion and diversity metrics.…”

Section: Discussionmentioning

confidence: 99%

High Resolution Orthomosaics of African Coral Reefs: A Tool for Wide-Scale Benthic Monitoring

Palma¹,

Casado

Pantaleo³

et al. 2017

Remote Sensing

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Abstract:Coral reefs play a key role in coastal protection and habitat provision. They are also well known for their recreational value. Attempts to protect these ecosystems have not successfully stopped large-scale degradation. Significant efforts have been made by government and research organizations to ensure that coral reefs are monitored systematically to gain a deeper understanding of the causes, the effects and the extent of threats affecting coral reefs. However, further research is needed to fully understand the importance that sampling design has on coral reef characterization and assessment. This study examines the effect that sampling design has on the estimation of seascape metrics when coupling semi-autonomous underwater vehicles, structure-from-motion photogrammetry techniques and high resolution (0.4 cm) underwater imagery. For this purpose, we use FRAGSTATS v4 to estimate key seascape metrics that enable quantification of the area, density, edge, shape, contagion, interspersion and diversity of sessile organisms for a range of sampling scales (0.5 m × 0.5 m, 2 m × 2 m, 5 m × 5 m, 7 m × 7 m), quadrat densities (from 1-100 quadrats) and sampling strategies (nested vs. random) within a 1655 m 2 case study area in Ponta do Ouro Partial Marine Reserve (Mozambique). Results show that the benthic community is rather disaggregated within a rocky matrix; the embedded patches frequently have a small size and a regular shape; and the population is highly represented by soft corals. The genus Acropora is the more frequent and shows bigger colonies in the group of hard corals. Each of the seascape metrics has specific requirements of the sampling scale and quadrat density for robust estimation. Overall, the majority of the metrics were accurately identified by sampling scales equal to or coarser than 5 m × 5 m and quadrat densities equal to or larger than 30. The study indicates that special attention needs to be dedicated to the design of coral reef monitoring programmes, with decisions being based on the seascape metrics and statistics being determined. The results presented here are representative of the eastern South Africa coral reefs and are expected to be transferable to coral reefs with similar characteristics. The work presented here is limited to one study site and further research is required to confirm the findings.

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“…These metrics have been transferred to marine studies and are currently widely used for management of seagrass seascapes, including ones formed by P. oceanica (Chefaoui, 2014;Montefalcone et al, 2013;Sleeman et al, 2005). However, recent studies concerning terrestrial ecosystem conservation have highlighted their limits (Kupfer, 2012;Šímová and Gdulová, 2012) the same observation being made for seascapes (Manderson, 2016).…”

Section: New Analysis Tools For Management Purposesmentioning

confidence: 99%

Seascape ecology in Posidonia oceanica seagrass meadows: Linking structure and ecological processes for management

Abadie

Pace

Gobert

et al. 2018

Ecological Indicators

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A B S T R A C TSeagrass meadows constitute marine habitats in shallow water temperate and tropical coastal areas worldwide that have a high ecological and economic importance. Amongst the 60 or so seagrass species, the endemic Mediterranean species Posidonia oceanica forms meadows that are arguably the most important shallow water coastal habitat in the region but which are subjected to high anthropogenic pressures. Because of the relatively large size of the plant, the meadows formed by this seagrass have high architectural and morphological complexity, which results in different morphotypes or seascapes. While numerous studies of P. oceanica architectural characteristics for continuous meadows of the seagrass are available, few works have addressed seascape ecological features and the influence of environmental factors (natural and anthropogenic) thereon. In the present review, we give an overview of P. oceanica meadow architectural and morphological characteristics and how these contribute to Mediterranean landscapes and seascapes. Studies addressing the influence of natural and anthropogenic factors on morphometric features of different meadow types and landscape ecological characteristics of P. oceanica habitat are also reviewed, as well as their influence on ecosystem processes. Finally, by considering the available data and tools for seascape studies, we present a discussion on methods to assess seagrass seascapes within the framework of coastal management. Our review highlights several gaps in P. oceanica seascape ecology knowledge such as the lack of data on the spatial distribution of this engineer species, and the possibility to use modern techniques and procedures for analysing structural and ecosystemic data.

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Measuring fragmentation of seagrass landscapes: which indices are most appropriate for detecting change?

Cited by 44 publications

References 51 publications

Fractal measures of habitat structure: maximum densities of juvenile cod occur at intermediate eelgrass complexity

Fractal measures of habitat structure: maximum densities of juvenile cod occur at intermediate eelgrass complexity

High Resolution Orthomosaics of African Coral Reefs: A Tool for Wide-Scale Benthic Monitoring

Seascape ecology in Posidonia oceanica seagrass meadows: Linking structure and ecological processes for management

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