NatureScot Research Report 1270 - Infaunal and PSA analyses of benthic samples collected from the Sound of Barra in 2018.
This report presents the findings of the analysis of 72 seabed samples collected off the Outer Hebrides in 2018. Precision Marine Survey Ltd. were commissioned to undertake faunal analysis and particle size analysis (PSA) of the samples and produce a brief interpretative report to characterise the benthic infaunal communities. The main findings are as follows. The samples collected within the Sound of Barra SAC were considered to include good examples of coarse sediment sub-types of the subtidal sandbank Annex I feature. The depths recorded and substrates described were similar across all monitoring boxes except S11, which was slightly deeper and muddier. Live maerl was collected at 52 out of 72 stations (primarily within the SAC). The physical and biological parameters measured at nine monitoring boxes appear to be consistent with those reported in 2016 and 2017. Forty seven stations within the Sound of Barra SAC (and some stations outside the SAC) were classified as SS.SMp.Mrl (maerl beds), most likely a variant of SS.SMp.Mrl.Pcal. Maerl beds are a Priority Marine Feature (PMF) and a sub-feature of the subtidal sandbanks Annex I habitat of the SAC. Other stations were often characterised by maerl influenced variants of SS.SCS biotopes, notably SS.SCS.ICS.MoeVen or SS.SCS.CCS.MedLumVen. Box S11 included rather different habitats characterised by the biotopes SS.SSa.OSa.OfusAfil or SS.SMx.CMx. Several species of conservation importance were also recorded during the Sound of Barra 2017 survey, including the PMF species including sandeels (Ammodytes marinus) and also occasional juvenile or immature specimens of the flame shell, Limaria hians.