Field spectroscopy of estuarine intertidal habitats

Abstract

The recent introduction of portable, low‐cost hyperspectral radiometers for measuring the reflectance of marine intertidal habitats has considerable promise, first as a source of reference spectra for airborne and satellite remote sensing, and second as a survey technique in its own right. This paper reports on the results of an intercalibration exercise in which two designs of commercially available instruments were used to measure reflectance spectra across a diverse, intertidal site. The substrates sampled included seagrasses, macroalgae, and sediments which varied in wetness and grain size. Spectra were compared statistically using several measures of similarity, and the results showed a high degree of correlation between the measured reflectance spectra. There were no significant differences between instruments from different manufacturers in the shape of reflectance spectra, but the signal‐to‐noise ratio varied considerably between individual instruments. Spectra measured by operators with lesser experience in field spectrometry tended to be more variable than those of more experienced operators, indicating that training and adherence to set protocols are important when implementing this method in the field situation. Spatial plots derived from field spectra showed essentially the same trends in surface features as plots created using traditional sampling and remote sensing methods. Furthermore, the use of field spectrometry as a stand‐alone, low‐cost method for rapidly mapping the distribution of major habitat types was demonstrated by the results of a survey of a large intertidal sandbank.

Acknowledgements

This work was funded by EU contract no. EVK3‐CT‐2001‐00052. Bruno Jesus is supported by a PhD grant from FCT (PraxisXXI‐BD21634/99). Jan Peene, Jan Roggeveld, and Paul van Nugteren are thanked for their assistance with the Zandkreek and Hooge Springer field surveys.