ORIGINAL PAPER Assessment of AHS (Airborne Hyperspectral Scanner) sensor to map macroalgal communities on the Rı ´a de vigo and Rı ´a de Alda ´n coast (NW Spain) G. Casal • N. Sa ´nchez-Carnero • J. A. Domı ´nguez-Go ´mez • T. Kutser • J. Freire Received: 30 August 2011 / Accepted: 19 June 2012 / Published online: 15 July 2012 Ó Springer-Verlag 2012 Abstract Rı ´a de Vigo and Rı ´a de Alda ´n have high biological richness that is reflected in the number of environmental protection areas like the Atlantic Islands National Park and five places of community interest. Benthic algal communities play an important role in these ecosystems due to their ecological functions and support a great part of this biological richness. We tested by means of bio-optical modelling and Airborne Hyperspectral Scanner (AHS) images to what extent remote sensing could be used to map these communities in Rı ´a de Vigo and Rı ´a de Alda ´n (NW Spain). Reflectance spectra of dominating macroalgae groups were modelled for different water depths in order to estimate the separability of different bottom types based on their spectral signatures and the spectral characteristics of the AHS. Our results indicate that separation between three macroalgae groups (green, brown and red) as well as sand is possible when the bot- toms are emerged during low tide. The spectra differences decrease rapidly with increasing water depth. Two types of classifications were carried out with the three AHS images: maximum likelihood and spectral angle mapper (SAM). Maximum likelihood showed positive results reaching overall accuracy percentages higher than 95 % and kappa coefficients higher than 0.90 for the bottom classes: shal- low sand, deep sand, emerged rock, emerged macroalgae and submerged macroalgae. Sand and algae substrates were then separately analysed with SAM. These classifi- cations showed positive results for differentiation between green and brown macroalgae until 5 m depth and high differences between all macroalgae and sandy substrate. However, differences between red and brown macroalgae are only detectable when the algae are emerged. Introduction Benthic algal communities play an important role in coastal ecosystems due to their ecological functions. These com- munities are essential for many organisms as habitat (e.g. Cacabelos et al. 2010), mating and nursery grounds (e.g. Shaffer 2003), feeding areas (e.g. Lorentsen et al. 2004) and refuge (e.g. Gotceitas et al. 1997). Another relevant aspect is their important contribution to primary production (Mohammed and Fredriksen 2004), the sediment stabil- ization and coastline protection (Madsen et al. 2001), besides being a suitable indicator on the ecological status of coastal communities (Juanes et al. 2008). On the other hand, the interest of commercial use of some algal species has been increased during the last years in many parts of the world (e.g. Vasquez 2008; Vea and Ask 2011). The same situation is also found on the Galician coast (Cre- mades et al. 2004) where specific exploitation plans were established. In this zone, the three main groups of macroalgae, Chlorophyta, Phaeophyta and Rhodophyta (green, brown and red macroalgae, respectively), are represented. Each of Communicated by F. Bulleri. G. Casal (&)  N. Sa ´nchez-Carnero  J. Freire Grupo de Recursos Marinos y Pesquerı ´as, Facultad de Ciencias, Universidad de A Corun ˜a, Ru ´a da Fraga 10, 15008 A Corun ˜a, Spain e-mail: gcasal@udc.es J. A. Domı ´nguez-Go ´mez Centro de Estudios Hidrogra ´ficos (CEDEX), Paseo Bajo de la Virgen del Puerto 3, 28005 Madrid, Spain T. Kutser Estonian Marine Institute, University of Tartu, Ma ¨ealuse 14, Tallinn 12618, Estonia 123 Mar Biol (2012) 159:1997–2013 DOI 10.1007/s00227-012-1987-5