Publication Date:
2017-02-02
Description:
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.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
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isiRev