Temperate habitats - east coast
Interlinking backscatter, grain size and benthic community structure
This project was run under the Marine Aggregate Levy Sustainability Fund Phase III (administered by CEFAS).
The final project report is here
The relationship between acoustic backscatter, sediment grain size and benthic community structure is examined using three different quantitative methods, covering image-and angular response-based approaches. Multibeam time-series backscatter (300 kHz) data acquired in 2008 off the coast of East Anglia (UK) are compared with grain size properties, macrofaunal abundance and biomass from 130 Hamon and 16 Clamshell grab samples. Three predictive methods are used; 1) image-based (mean backscatter intensity); 2) angular response-based (predicted mean grain size), and 3) image-based (1st principal component and classiﬁcation) from Quester Tangent Corporation Multiviewsoftware. Relationships between grain size and backscatter are explored using linear regression. Differences in grain size and benthic community structure between acoustically deﬁned groups are examined using ANOVA and PERMANOVA. Results for the Hamon grab stations indicate signiﬁcant correlations between measured mean grain size and mean backscatter intensity, angular response predicted mean grain size, and 1st principal component of QTC analysis (all p<0.001). Results for the Clamshell grab for two of the methods have stronger positive correlations; mean backscatter intensity (r2=0.619; p<0.001) and angular response predicted mean grain size (r2=0.692; p<0.001). ANOVA reveals signiﬁcant differences in mean grain size (Hamon) within acoustic groups for all methods: mean backscatter (p<0.001), angular response predicted grain size (p<0.001), and QTC class (p=0.009). Mean grain size (Clamshell) shows a signiﬁcant difference between groups for mean backscatter (p=0.001); other methods were not signiﬁcant. PERMANOVA for the Hamon abundances shows benthic community structure was signiﬁcantly different between acoustic groups for all methods (p<0.001). Overall these results show considerable promise in that more than 60% of the variance in the mean grain size of the Clamshell grab samples can be explained by mean backscatter or acoustically-predicted grain size. These results show that there is signiﬁcant predictive capacity for sediment characteristics from multibeam backscatter and that these acoustic classiﬁcations can have ecological validity.
McGonigle C, Collier JS, 2014, Interlinking backscatter, grain size and benthic community structure,Estuarine, Coastal and Shelf Science, Vol:147, ISSN:0272-7714, Pages:123-136 DOI