Brigitte Guillaumont

Quantification of Subpixel Cover Fractions Using Principal Component Analysis and a Linear Programming Method: Application to the Coastal Zone of Roscoff (France)

Abstract In this study, principal component analysis and the linear programming method “affine algorithm” were jointly used to provide an unmixing method and to calculate fractions bounds of main seaweeds and intertidal components from mixed pixels. The method was tested using CASI airborne imagery data taken over the Roscoff coastal zone (Brittany, France). The contribution of the number of spectral bands used to identify many component types was also examined. Between four and six components can be distinguished depending on the spectral richness of the original image. The accuracy of fraction cover types was estimated by comparing calculated proportions with ground data. Whatever the number of bands and ground categories, the coefficient of determination R 2 was higher than 0.62. Much more information and more accurate results were obtained with 13 spectral bands (R 2 from 0.81 to 0.96).

Spatial distribution and quantification of Fucus species and Ascophyllum nodosum beds in intertidal zones using spot imagery

Low tide SPOT images were selected from two French coast areas characterized by important Fucaceae populations (Pleubian-Brehat site in Northern Brittany and Re Island on the Atlantic coast).

Application of airborne imaging spectrometry system data to intertidal seaweed classification and mapping

The aim of this paper is to test the ability of imaging radiometers to describe the principal seaweed and seagrass beds along the coast of Brittany (France). In this work we used CASI, an instrument with programmable narrow bands. On the ground, regions of homogeneous vegetation cover were mapped using differential GPS positioning. Ground spectra were recorded with a field spectroradiometer (Spectron SE 590), for substratum and different species. Their analysis shows variations in relation to pigment characteristics, vegetation structure and environmental conditions. An algorithm sequence based on field work and according to the technical sensor characteristics, was developed to discriminate the dominant species. The classified CASI image was compared with ground data. The main results are the following: (a) the visible wavelengths allow good discrimination between green, red and brown algae. (b) the infrared wavelengths allow separation of two main types of brown species, seagrasses and the identification of floating seaweed.

Cold-Water Coral Habitats in Submarine Canyons of the Bay of Biscay

The topographical and hydrological complexity of submarine canyons, coupled with high substratum heterogeneity, make them ideal environments for cold-water coral (CWC) habitats. These habitats, including reefs, are thought to provide important functions for many organisms. The canyons incising the continental slope of the Bay of Biscay have distinct morphological differences from the north to the south. CWCs have been reported from this basin in the late 19th century; however, little is known about their present-day distribution, diversity and environmental drivers in the canyons. In this study, the characteristics and distribution of CWC habitats in the submarine canyons of the Bay of Biscay are investigated. Twenty-four canyons and three locations between adjacent canyons were sampled using a Remotely Operated Vehicle (ROV) or a towed camera system. Acquired images were annotated for habitat type (using the CoralFISH classification system), substrate cover and coral identification. Furthermore, the influence of hydrological factors and geomorphology on the CWC distribution was investigated. Eleven coral habitats, formed by 62 morphotypes of scleractinians, gorgonians, antipatharians and seapens, inhabiting hard and/or soft substrate, were observed. The distribution patterns were heterogenous at regional and local scales; the south Bay of Biscay and the southeastern flank favored soft substrate habitats. Biogenic and hard substrate habitats supported higher coral diversities than soft substrate habitats and had similar species compositions. A higher coral species turnover characterized soft substrate habitats. Substrate type was the most important driver of the patterns in both distribution and composition. Observations of coral reefs on steeper areas in the canyons and coral rubble on flatter areas on the interfluve/upper slope, support the hypothesis that canyons serve as refuges, being less accessible to trawling, although natural causes may also contribute to the explanation of this distribution pattern. The results of this study fed into a proposal of a Natura 2000 network in the Bay of Biscay where management plans are rare.