Tools to evaluate seafloor integrity: comparison of multi-device acoustic seafloor classifications for benthic macrofauna-driven patterns in the German Bight, southern North Sea


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Finn.Mielck [ at ] awi.de

Abstract

To determine the spatial resolution of sediment properties and benthic macrofauna communities in acoustic backscatter, the suitability of four acoustic seafloor classification devices (single-beam echosounder with RoxAnn and QTC 5.5 seafloor classification system, sidescan sonar with QTC Swathview seafloor classification, and multi-beam echosounder with QTC Swathview seafloor classification) was compared in a study area of approx. 6 km2 northwest of the island of Helgoland in the German Bight, southern North Sea. This was based on a simple similarity index between simultaneous sidescan sonar, single-beam echosounder and multi-beam echosounder profiling spanning the period 2011–2014. The results show a high similarity between seafloor classifications based on sidescan sonar and RoxAnn single-beamsystems, in turn associated with a lower similarity for the multi-beam echosounder system. Analyses of surface sediment samples at 39 locations along four transects (0.1 m2 Van Veen grab) revealed the presence of sandy mud (southern and western parts), coarse sand, gravel and cobbles. Rock outcrops were identified in the north-eastern and eastern parts. A typical Nucula nitidosa–Abra alba community was found in sandy muds to muddy sands in the northern part, whereas the southern part is characterised by widespread occurrence of the ophiuroid brittle star Amphiura filiformis. A transitional N. nitidosa–A. filiformis community was detected in the central part. Moreover, the southern part is characterised by a high abundance of A. filiformis and its commensal bivalve Kurtiella bidentata. The high number of A. filiformis feeding arms (up to ca. 6,800 per m2) can largely explain the gentle change of backscatter intensity along the tracks, because sediment composition and/or seafloor structures showed no significant variability.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
42703
DOI 10.1007/s00367-016-0488-9

Cite as
Holler, P. , Markert, E. , Bartholomä, A. , Capperucci, R. , Hass, H. C. , Kröncke, I. , Mielck, F. and Reimers, H. C. (2016): Tools to evaluate seafloor integrity: comparison of multi-device acoustic seafloor classifications for benthic macrofauna-driven patterns in the German Bight, southern North Sea , Geo-Marine Letters, pp. 1-17 . doi: 10.1007/s00367-016-0488-9


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