triggered, an offset positional fix was obtained and the grab was recovered onto the deck of the survey vessel.


35.


Each sample was discharged into a plastic box and a photograph was taken. The sample was then either accepted or rejected dependent on volume (sample sizes of above five litres were accepted). A maximum of three attempts were made at each station to obtain the correct sample size. Where all three samples were smaller than five litres in volume, the largest sample was retained for processing and a decision was made as to whether removing a sub-sample for particle size distribution (PSD) analysis was appropriate.


36. Where sample volumes allowed, three small sub-samples were obtained from the sediment in the box and the pooled sample of between 0.5 and 1.0L was retained in a labelled plastic bag for subsequent particle size distribution analysis.


37.


Following sub-sampling, the residual grab samples were washed with seawater over a 1mm sieve to remove fine particles. The residual samples were preserved in formalin and sealed for transportation to the laboratory.


38. Where S.spinulosa was observed within a grab sample, detailed field notes were prepared and additional photos were taken of any significant amounts identified during sieving.


39.


In the laboratory all fauna were extracted from each sample, identified to the highest taxonomic level and enumerated. The sub-samples of sediment were subject to full particle size analysis and were sieved over the range 31.5 to 0.063mm on the Wentworth scale. The results were expressed as absolute percentage retained on each sieve size.


10.4.2.2.3Sampling for Epifauna 40.


Epibenthic samples were obtained in the East Anglia Zone and the East Anglia THREE site using a 2m scientific beam trawl towed at speeds between 1 and 2 knots. A bottom time of 10 minutes or 500m distance per trawl was maintained throughout the different surveys. Following deployment of the trawl, each sample was brought aboard the vessel, discharged into a box or tray and was photographed.


41.


Fish and invertebrates sampled during trawling were sorted, enumerated, identified and weighed on board the survey vessel and, wherever possible, were returned to the sea alive. Invertebrates and fish species that could not be accurately identified during the survey were preserved in 10% formaldehyde and brought back to the laboratory for verification.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Chapter 10 Benthic Ecology Page 25


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