Habitat mapping based on acoustic remote sensing methods have been rarely carried on ultra-shallow coastal transitional systems such as lagoons and estuaries. This is due to a number of practical and conceptual issues, including very low bathymetries, fine-scale patterns and processes, continuous environmental and biological gradients, high temporal variability, and complex water column properties. In this study we present the first results of an extensive survey carried out by a multidisciplinary team of the ISMAR- CNR, Italy during 2013 using a Kongsberg EM-2040 DC multibeam system. The survey interested all the lagoonal channel network, since, although numerous biological studies have been carried out to study the habitats in the tidal flats and salt marshes of the Venice lagoon, the channel seafloor and biota are still almost unexplored. The distinctive features of lagoon channels call for specific operative protocols, both for the acoustic surveys and for ground-truthing sampling.In particular, we will show the first results of a survey carried out in a natural tidal channel of the northern part of the Venice Lagoon (water depths from 15 m to less than 1 m). On the high resolution bathymetric data collected (5 cm DTM resolution) we performed a 2D FFT analysis to quantitatively describe the channel seafloor morphology (roughness, dune field wavelength, deposition and erosion areas, etc.). On the high resolution backscatter data, instead, we carried out a two-dimensional (2D) textural analysis with the TexAn software. We then performed an unsupervised classification of the backscatter data. As a result, we were able to identify different backscatter areas where several grab samples were collected for ground truthing. With the help of this sampling we calibrated the textural analyses and obtained a classification of the different kinds of substrate. The characterization of the substrate was then tested with a set of bottom photographs. For this purpose a specific protocol was developed to address the main issues of underwater photographic surveys include extreme turbidity, strong tidal currents, complex morphology, intense vessel traffic.
A comprehensive approach to habitat mapping in extremely shallow water: from acoustic survey to ground-truth.
Fantina Madricardo;Federica Foglini;
2014
Abstract
Habitat mapping based on acoustic remote sensing methods have been rarely carried on ultra-shallow coastal transitional systems such as lagoons and estuaries. This is due to a number of practical and conceptual issues, including very low bathymetries, fine-scale patterns and processes, continuous environmental and biological gradients, high temporal variability, and complex water column properties. In this study we present the first results of an extensive survey carried out by a multidisciplinary team of the ISMAR- CNR, Italy during 2013 using a Kongsberg EM-2040 DC multibeam system. The survey interested all the lagoonal channel network, since, although numerous biological studies have been carried out to study the habitats in the tidal flats and salt marshes of the Venice lagoon, the channel seafloor and biota are still almost unexplored. The distinctive features of lagoon channels call for specific operative protocols, both for the acoustic surveys and for ground-truthing sampling.In particular, we will show the first results of a survey carried out in a natural tidal channel of the northern part of the Venice Lagoon (water depths from 15 m to less than 1 m). On the high resolution bathymetric data collected (5 cm DTM resolution) we performed a 2D FFT analysis to quantitatively describe the channel seafloor morphology (roughness, dune field wavelength, deposition and erosion areas, etc.). On the high resolution backscatter data, instead, we carried out a two-dimensional (2D) textural analysis with the TexAn software. We then performed an unsupervised classification of the backscatter data. As a result, we were able to identify different backscatter areas where several grab samples were collected for ground truthing. With the help of this sampling we calibrated the textural analyses and obtained a classification of the different kinds of substrate. The characterization of the substrate was then tested with a set of bottom photographs. For this purpose a specific protocol was developed to address the main issues of underwater photographic surveys include extreme turbidity, strong tidal currents, complex morphology, intense vessel traffic.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
