Echinodermata with 14% and Crustacea with 12% of the total number of individuals recorded. Others contributed 9% and enumerated epifaunal taxa less than 1%.
105. Biomass was recorded as blotted weight and then converted in ash free dry weight (AFDW) following (Elefthriou and Besford, 1985). Weight for mollusca included shells and the biomass for both enumerated and non‐enumerated epifauna species was included in ‘Others’. The phylum contributing the most (Figure 3.7) was the Echinodermata which accounted for 66% of the total AFDW. This was due to high abundance of Ophelia borealis and Nephtys cirros, followed by Crustacea which contributed 17% and Polychaeta which contributed 13 %. Mollusca and Others contributed each less than 10%. Biomass data are presented in Appendix R.
Figure 3.7 Contribution to Biomass by All Major Groups (AFDW). Epifauna is Included in ‘Others’. Biomass (AFDW)
1% 13%
17%
Others
Polychaetes Crustaceans Molluscs Echinodermata
66% 3%
106. Amongst the top ten most abundant taxa recorded from the grab samples, five were also amongst the most frequently recorded (Table 3.4). The two most abundant species were both found in 69% of the samples (27 sites out of 39) and were the polychaeta species O. borealis and N. cirrosa. These two species were also the two most frequently recorded in grabs. Another polychaeta species, belonging to the genus Notomastus was the third most abundant species, recorded at 17 sites. The most abundant echinoderm recorded was the pea urchin Echinocyamus pusillus (recorded in about 28% of the samples), while the most abundant mollusc recorded was the bivalve Kurtiella bidentata (which was not recorded in the top ten most frequent species). No
Benthic Characterisation Report November 2013
East Anglia THREE and FOUR Offshore Cable Corridor
