Application of Landscape Mosaics for the Biological Quality Assesment of Subtidal Macroalgae Communities Using the CFR Index

Abstract

The assessment of anthropogenic impacts on coastal waters is an important task to accomplish under the European Water Directive Framework (WFD2000/60/EEC). Macroalgae are one of the biological quality elements that must be considered, but their assessment has been generally limited to intertidal areas. In this work the suitability of using landscape mosaicing techniques for the application of the CFR index in subtidal areas is analyzed. The study was carried out at two impacted areas (urban and industrial discharges) and at a control site located on the coast of Cantabria (N Spain). Underwater video transects of 5–20 m length were recorded by scuba divers at three depth ranges and treated with specific application software in order to build landscape mosaics of the assessment sites. Each mosaic was then introduced into a Geographical Information System, where all distinguishable macroalgae species were identified and their coverages measured. Subsamples of different areas (0.25 m 2 , 0.5 m 2 , 1 m 2 and 2.5 m 2 ) were extracted from each mosaic for the estimation of the indicators which compose the CFR index (characteristic macroalgae coverage, fraction of opportunistics and characteristic macroalgae richness). The stations located near the industrial discharge obtained bad qualities at all depths, while the stations located near the urban discharge and the control site obtained moderate to high qualities depending on depth ranges and sample sizes. Deeper samples produced lower CFR values, mainly associated to lower characteristic macroalgae coverages. On the other hand, bigger samples produced higher CFR values, mainly associated to higher richness values, and more accurate results, due to smaller variability in the replicates. The use of landscape mosaicing techniques have provided a new tool for the study of subtidal environments by allowing the visualization of extensive subtidal areas, which has been very useful for the application of the CFR index.

Department

Center for Coastal and Ocean Mapping

Publication Date

4-2012

Volume

XIII

Journal Title

International Symposium on Oceanography of the Bay of Biscay

Pages

174

Conference Date

Apr 4 - Apr 11, 2012

Publisher Place

Santander, Spain

Document Type

Conference Proceeding

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