East Anglia Offshore Windfarm: Zonal Environmental Assessment Benthic Report
B.2.2 Separation and Analysis of Fauna
On arrival at the MESL a nalytical laboratory, the samples were checked agai nst the fi eld notes in accordance with MESL’s standard operating procedures (Appendix Table 1) and signed against the li st of sampl es collected. The excess formalin was then poured through a 1mm mesh sieve and collected for licensed disposal. Each sample was gently eluted with tap water t hrough a 1mm mesh si eve to extract the low-density components (Crustacea and polychaetes) and co mbined with the material initially separated from the formalin in the sample. The larger macrofauna were remov ed from th e eluted material.
This stage in t he initial sorting process was carried out in the open air to redu ce the effects of residual formalin used to preserve the sample on the survey vessel.
The sediments were subsequ ently sorted under a ste reomicroscope with the aim of extracting the fauna. The entire sample of separated fauna was then pres erved in industrial methylated spirit (IMS) for analysis. Each of the extr acted samples was subsequently sorted into major faunal groups before being analysed to species level by trained taxonomists who sign a log sheet on completion of the anal ysis of each individual sample. All taxonomi c identification was thoroughly checked throughout the proces s both by senior analysts and a gainst a reference collection held for ease of use in the analytical laboratory.
Marine Ecological Surveys Li mited is a leading participant in t he National Marine Biological Analytical Quality Control (NMBAQC) scheme. Species identification was recorded i n a standard format usi ng species codes from Howson & Picton (1997). The data were entered into the MESL UNICORN (Access-based) database.
The blotted wet wei ght of major groups recorded from the benthi c grab samples was measured. These data were then used to estimate total biomass as ash-free dry weight (AFDW) in grams using conventional conversion factors for each of the faunal groups. The wet wei ght conversion factors are as follows in accordance with Eleftheriou & Basford (1989)2.
The sub-samples of sedi ment obtained in accordance with the procedures outl ined in Section B.2.1. were subject to full particle size analysis by Gardline Environmental Limited (GEL). The sedi ments were sieved over the ra nge 31.5mm-0.063mm on the Wentworth scale. The results were expressed as absolute percentage retained on each sieve size. These resul ts are summarised in Appendix Table 7 and are summarised i n Appendix Table 8 into fractions of % gravel , % sand an d % si lt for ease of broa d-scale substrate assessment.
2
Eleftheriou,A & Bas ford,D.J. 1989. The
macrofauna of the offshore northern North Sea. Journal of the Marine Biological Association, UK. 69, 123-143.
