East Anglia Offshore Windfarm: Zonal Environmental Assessment Benthic Report
C.1.2 Multivariate Statistical Analysis of EAOW Sediment Data
The pie diagrams presented in Figure 8 and Figure 9 are a conveni ent visual method of expressing the overall proportions of silt, sand and gravel of which the EAOW sediment samples were composed. Ho
Figure 10 r eveals that the substrat a of the area of interest were representative of a total of four d istinct sediments at a Euc lidean Distance of 50.
wever,
presenting PSD data in such a mann er is of limited usefulness given that each sedi ment category represents an agglomeration of detailed data under broa d headings and, as such, the nuances of the
sediment
composition at each stati on may be subsumed.
In order to make full use of the detailed PSD results presented in Appendix Table 7 the data have been analysed using sophisticated multivariate statistical techniques. Such techniques provide sensitive analytical tools which are capabl e of provi ding not onl y detailed insight into sediment composition, but also the rel ationships between s amples obtained from the area. A variety of analytical techniques within the PRIME R software package were util ised in order to facilitate more detailed analyses of the data and to pro vide greater insight into the composition of the sea floor across the EAOW zone.
A group average sorting dendrogram (based on Euclidian Distance) and a correspondi ng two-dimensional multidimensional scaling (MDS) ordination was produced i n PRIMER using the sediment data acquired from across the EAOW zone. The outputs of thes analyses are presented in Figure 10.
The low stress val ue for the MDS indicates that this image presents a reliable spatial interpretation of the i nter-relationships between the sediment samples acquired from across the survey area.
The sediment groups have been categorised as Sediment Group A, Sediment Group B, Sediment Group C and Sediment Group D. A photographi c example of each EAOW sediment group is presented in Plate 8.
Table 1. The mean proportions of gravel, sand and silt which comprised each of the EAOW zonal multivariate sediment groups. Each group has been assigned a group description based on the Folk Scale of classification.
