Acoustic detection of macroalgae in a dynamic Arctic environment. Isfjorden (West Spitsbergen) case study

Abstract

Acoustic imaging of seabed morphology and benthic habitats is a fast-developing tool for investigating large areas of underwater environment. Even though single- and multi-beam echosounders have been widely used for this purpose for many years, there is still much to discover, especially in terms of processing water column echoes to detect macroalgae and other scatterers (e.g., fishes, or suspended sediments) that can provide us with important information about the underwater environment and its evolution. In difficult Arctic conditions, acoustic monitoring plays an important role in the investigation of bottom morphology and in imaging habitats. In July 2016, we carried out a multidisciplinary expedition to investigate macroalgae spatial distribution in Isfjorden and to measure significant environmental features (currents, salinity, turbidity) influencing their occurrence. An area of 4.3 km² was mapped using single- and multi-beam sonars along with underwater video recordings, CTD and ADCP measurements. We obtained a unique data set showing variability of acoustic properties among different macroalgae species, supported by very well correlated ground-truth data and environmental measurements. Modern processing techniques were used to analyze water column data signals for kelp detection. This study presents efficient tools for monitoring benthic communities and their environmental context, focusing on macroalgae acoustic characteristics.

Integrated Methodological Approach for the Documentation of Marine Priority Habitats and Submerged Antiquities: Examples from the Saronic Gulf, Greece

“…MBES systems are also used for mapping geomorphological features of the seafloor through backscatter analysis of the echoes. Mapping of underwater biological communities through MBES is considered one of the most effective techniques as it has been applied in many different cases [64][65][66], such as detecting P. oceanica meadows [67][68][69] and coralligenous formations [70]. In marine geoarchaeology, the MBES is now a basic tool for mapping submerged landscapes and delimiting ancient submerged structures or shipwrecks [71,72].…”