Search

Seafloor measurements using single-beam, multi-beam, sub-bottom, and side-scan sonars which enable detailed mapping of solid objects in sediments, seafloor structure and depth can provide useful information for marine traffic as well as scientific studies. The measurements obtained using these technologies, which provide a large number of points, make possible the preparation of an accurate digital bathymetric model. The most widely used application of these kinds of measurements is undoubtedly to determine depths of marinas, berths and shipping channels, especially around large commercial ports. However, their importance in the discovery and investigation of undersea archaeological sites such as shipwrecks, ancient piers, and amphorae is not to be ignored. The data are also useful for geologists, since they can provide clues as to the type of seafloor and the composition of rocks underneath the sediments. They can also be helpful to nature conservationists in locating and studying undersea springs and grassy areas of the seafloor which provide habitat for marine fauna. In order to facilitate access to data by users, we are developing an “undersea information system” containing different layers of data in various forms and with different types of content. Findings from the latest research can be added to the system. A system set up in this way would allow for faster production of three-dimensional seafloor models, more detailed charts and a variety of thematic maps.

In this study, we focused on relatively inexpensive and commonly used fishermen class sonar in order to test its ability to detect stands of charophytes and other groups of submerged angiosperms in the shallow and turbid waters of the Curonian Lagoon. Based on the length of macrophytes, height thresholds (20 and 30 cm) were established in order to distinguish charophytes from submerged angiosperms in obtained echograms. The echograms were visually analysed by two experts. We successfully discriminated 3 echofeatures (bare bottom, stands of charophytes and submerged angiosperms), whereas angiosperms from different morphology groups could not be distinguished. Below 1 m depth, the stands of charophytes and submerged angiosperms were clearly distinguished, thus their maximum colonization depth could be delineated. The accuracy of the discrimination could be reduced by free-drifting mats of filamentous algae, resulting in the overestimation of charophytes. Our approach can be useful for the mapping of monospecific stands of submerged vegetation and could be an important additional tool for macrophyte monitoring and water quality assessment in shallow and turbid waterbodies. [ABSTRACT FROM AUTHOR]

Abstract: This review examines the various strategies and methods used to produce benthic habitat maps using acoustic remote sensing techniques, coupled with in situ sampling. The applications of three acoustic survey techniques are examined in detail: single-beam acoustic ground discrimination systems, sidescan sonar systems, and multi-beam echo sounders. Over the past decade we have witnessed the nascence of the field of benthic habitat mapping and, on the evidence of the literature reviewed in this paper, have seen a rapid evolution in the level of sophistication in our ability to image and thus map seafloor habitats. As acoustic survey tools have become ever more complex, new methods have been tested to segment, classify and combine these data with biological ground truth sample data. Although the specific methods used to derive habitat maps vary considerably, the review indicates that studies can generally be categorized into one of three over-arching strategies; 1) Abiotic surrogate mapping; 2) Assemble first, predict later (unsupervised classification); 3) Predict first, assemble later (supervised classification). Whilst there is still no widely accepted agreement on the best way to produce benthic habitat maps, all three strategies provide valuable map resources to support management objectives. Whilst there is still considerable work to be done before we can answer many of the outstanding technological, methodological, ecological and theoretical questions that have been raised here, the review concludes that the advent of spatial ecological studies founded on high-resolution environmental data sets will undoubtedly help us to examine patterns in community and species distributions. This is a vital first step in unraveling ecological complexities and thus providing improved spatial information for management of marine systems. [Copyright &y& Elsevier]

Seafloor measurements using single-beam, multi-beam, sub-bottom, and side-scan sonars which enable detailed mapping of solid objects in sediments, seafloor structure and depth can provide useful information for marine traffic as well as scientific studies. The measurements obtained using these technologies, which provide a large number of points, make possible the preparation of an accurate digital bathymetric model. The most widely used application of these kinds of measurements is undoubtedly to determine depths of marinas, berths and shopping channels, especially around large commercial ports. However, their importance in the discovery and investigation of undersea archaeological sites such as shipwrecks, ancient piers, and amphorae is not to be ignored. The data are also useful for geologists, since they can provide clues as to the type of seafloor and the composition of rocks underneath the sediments. They can also be helpful to nature conservationists in locating and studying undersea springs and grassy areas of the seafloor which provide habitat for marine fauna. In order to facilitate access to data by users, we are developing an "undersea information system" containing different layers of data in various forms and with different types of content. Findings from the latest research can be added to the system. A system set up in this way would allow for faster production of three-dimensional seafloor models, more detailed charts and a variety of thematic maps. [ABSTRACT FROM AUTHOR]