Dots on the rocks: a comparison of percent cover estimation methods

Meese, Robert J.; Tomich, Patricia A.

doi:10.1016/0022-0981(92)90289-m

Cited by 157 publications

(140 citation statements)

References 16 publications

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“…Various procedures of underwater sampling and surveys have been evaluated for advantages and disadvantages when used to estimate cover of sessile marine organisms (e.g. Loya 1972, Chiappone & Sullivan 1991, Foster et al 1991, Meese & Tomich 1992, Dethier et al 1993, Benedetti-Cecchi et al 1996, Nadon & Stirling 2005. These studies identified the optimal compromise in terms of repeatability, precision, replication and costefficiency for estimating areal coverage.…”

Section: Introductionmentioning

confidence: 99%

Hierarchical segmentation-based software for cover classification analyses of seabed images (Seascape)

Teixidó¹,

Albajes‐Eizagirre²,

Bolbo³

et al. 2011

Mar. Ecol. Prog. Ser.

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An important aspect of marine research is to quantify the areal coverage of benthic communities. It is technically feasible to efficiently obtain images of marine environments at different depths and benthic habitats over large spatial and temporal scales. Currently, there is a large and growing library of digital images to analyze, representing a valuable benthic ecological archive. Benthic coverage is the basis of studies on biodiversity, characterization of communities and evaluation of changes over temporal and spatial scales. However, there is still a lack of automatic or semi-automatic analytical methods for deriving ecologically relevant data from these images. We introduce a software program named Seascape to obtain semi-automatically segmented images (patch outlines) from underwater photographs of benthic communities, where each individual patch (species/categories) is routinely associated to its area cover and perimeter. Seascape is an analog to the classical and better known discipline of landscape ecology approach, which focuses on the concept that communities can be observed as a patch mosaic at any scale. The process starts with a hierarchical segmentation, using a color space criteria adapted to the problem of segmenting complex benthic images. As an endproduct, we obtain a set of images segmented into classified homogenous regions at different resolution levels (hierarchical segmentation). To illustrate the versatility and capacity of Seascape, we analyzed 4 digital images from different habitats and depths: coral reefs (Pacific Ocean), coralligenous communities (NW Mediterranean Sea), deep-water coral reefs (NW Mediterranean Sea) and the Antarctic continental shelf (Weddell Sea). The development of this semi-automatic outline tool and its use for classification constitute an important step forward in the analysis and processing time of underwater seabed images at any scale.

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Section: Introductionmentioning

confidence: 99%

Hierarchical segmentation-based software for cover classification analyses of seabed images (Seascape)

Teixidó¹,

Albajes‐Eizagirre²,

Bolbo³

et al. 2011

Mar. Ecol. Prog. Ser.

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“…Na tentativa de procurar entender os padrões de distribuição e abundância das comunidades assume-se, implicitamente, que os métodos empregados fornecem uma estimativa precisa e consistente do número de organismos realmente presentes (Meese & Tomich, 1992). Mas, é preciso considerar que as informações sobre a distribuição e abundância dos organismos são geralmente a única base para decisões ecológicas e de manejo.…”

Section: Introductionunclassified

“…A comparação entre os métodos, de forma a identificar o mais representativo da realidade da comunidade e o mais adequado a ser utilizado, tem instigado alguns estudos recentes (Meese & Tomich, 1992;Dethier et al, 1993), apesar de a metodologia da amostragem em si já ser um objeto de discussão muito antigo.…”

Section: Introductionunclassified

Estudo comparativo de métodos de amostragem de comunidades de Costão

Sabino

Villaça

1999

Rev. Bras. Biol.

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Sampling methods for rocky shoresThis study compares three sampling methodologies of rocky shore communities: visual estimation, point intercept quadrats and destructive sampling. Visual estimation was performed in two sizes of sampling device and, point intercept quadrats was done with different numbers of marked dots. The sampling took place on the rocky shore of Forno beach, Búzios, RJ, in two different algae belts; one whose the landscape is characterized by Amphiroa sp., the other, Sargassum furcatum was the most conspicuous species. The data were analyzed by ANOVA and Kruskal-Wallis tests. Number of species, total percent cover, diversity and evenness indices were the variables used. The results shown that in general the methods compared were not statistically different one from the other in this community. There were significative differences between the methods when comparison was made between nondestructive and destructive sampling. However, smaller areas of sampling devices and fewer intercept points decreased the sampling power in respect of sampling species richness. All of the methods studied were considered similar in concern of total cover index and of diversity and evenness indices, with some exceptions. Present data are useful only for rocky communities with similar profiles. The choice of method must be made in regard of each situation.Key words: sampling methods, rocky shore, phytobenthos, Búzios, RJ. RESUMOO presente estudo compara três metodologias de amostragem de costão rochoso: estimativa visual, pontos de interseção e raspagem total do substrato. No método de estimativa visual, variou-se o tamanho do amostrador e, no de pontos de interseção, o número de pontos marcados. As amostras foram coletadas no costão da praia do Forno, Búzios, RJ, em duas faixas, uma dominada fisionomicamente por Amphiroa sp. e a outra, por Sargassum furcatum. Foram aplicados testes de ANOVA e KruskalWallis aos resultados encontrados, utilizando-se como variáveis os índices bionômicos de número de espécies, porcentagem total de recobrimento, índice de diversidade e índice de uniformidade. Os resultados provaram que nenhuma metodologia de amostragem semelhante mostrou-se estatisticamente diferente da outra. Existe diferença quando se comparam os métodos não-destrutivos ao método destrutivo. No entanto, amostradores com menor área ou menor número de pontos não amostram bem o índice número de espécies. Os métodos não apresentaram diferença significativa em relação à cobertura total e aos índices de diversidade e uniformidade, salvo algumas exceções. Os resultados do presente trabalho são aplicáveis apenas a comunidades de costão rochosos com perfis similares ao da comunidade estudada. A escolha do método deve ser considerada para cada situação.Palavras-chave: metodologia de amostragem, costão rochoso, fitobentos, Búzios, RJ.

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“…Percentage cover of green macroalgae on tidal flats was estimated visually for areas of 50 x 50 m. Meese & Tomich (1992) tested several percent cover estimation methods, i.e. visual estimation, evenly spaced dots, random d6ts, stratified random dots and electronic digitizing of photographic images for repeatability and robustness against observer bias.…”

Section: Distribution Of Periwinkles and Green Algaementioning

confidence: 99%

Grazing on green algae by the periwinkleLittorina littorea in the Wadden Sea

Wilhelmsen

Reise

1994

Helgolander Meeresunters

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On sedimentary tidal flats in the Wadden Sea near the Island of Sylt, the periwinkle Littorina littorea occurred preferentially on clusters and beds of mussels and on shell beds (100 to 350 m-2), achieved moderate densities on green algal patches or mats (20 to 50 m-2), and remained rare on bare sediments (<5 m-2). Green algae covering > 10 % of sediment surface appeared in summer on approximately one third of the tidal zone, mainly in the upper and sheltered parts and almost never on mussel and shell beds. In feeding experiments, L. fittorea ingested more of the dominant alga, Enteromorpha, than of U/va, irrespective of whether or not algae were fresh or decaying. The tough thalli of Chaetomorpha were hardly consumed. Snails feeding on Enteromorpha produced fecal pellets from which new growth of Enteromorpha started. In the absence of periwinkles, Enteromorpha developed on mussels and the attached fucoids. Experimentally increased snail densities on sediments prevented green algal development, but the snails were unable to graze down established algal mats. It is concluded that natural densities of L. httorea hardly affect the ephemeral mass development of green algae on sediments. However, where the snails occur at high densities, i.e. on mussel beds, green algal development may be prevented.

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Dots on the rocks: a comparison of percent cover estimation methods

Cited by 157 publications

References 16 publications

Hierarchical segmentation-based software for cover classification analyses of seabed images (Seascape)

Hierarchical segmentation-based software for cover classification analyses of seabed images (Seascape)

Estudo comparativo de métodos de amostragem de comunidades de Costão

Grazing on green algae by the periwinkleLittorina littorea in the Wadden Sea

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