2015 Natural England Brownsea Island Lagoon Condition Assessment dataset https://portal.medin.org.uk/portal/start.php?tpc=010_5f0fd7177f8cbeaa40ad552a13e875ba Natural England (NE) commissioned APEM to carry out a biological survey of the saline lagoon on Brownsea Island, within the Poole Harbour SPA and SSSI. Coastal lagoon communities are a key attribute of the SPA and SSSI coastal lagoon features The aim of this survey is to make a preliminary assessment of change within the lagoon absed on historical data. The methods employed within this study followed previous monitoring activities reporting on quantitative and qualitative characteristics of five key lagoonal quality features: benthos, nekton, flora and fauna amongst vegetation, epifauna and physicochemical condition. Results of sampling were compared with the previous survey of the lagoon undertaken by Herbert et al. (2010). These data were then used to indicate whether any changes in physicochemical parameters or biota were evident to make a preliminary assessment of change since this prevous survey. Six sampling stations were selected to correspond with historical sampling stations whilst a further six were added to provide greater coverage and detail on the condition of the lagoon. The sampling consisted of qualitative Phase I and quantitative Phase II survey. For the Phase I survey, the main biota present in and around the lagoon were recorded including the main vegetation taxa present, and records were taken of conspicous invertebrate fauna and megafauna (e.g. insects and birds). Preliminary biotope maps for the lagoon were produced in situ based on observed sediment types and biota which were further refined based on the results of the quantitative sampling. During the Phase I survey, notes were also taken relating to the nature of any isolating barriers and the presence of any potential anthropogenic pressures. The Phase II survey consisted of recording physicochemical parameters in the water column, collecting and analysing in situ semi-quantitative sweep net samples of the nekton, recording taxa found on vegetation, collecting benthic core samples for subsequent laboratory analysis (enumeration and biomass) and obtaining samples for particle size analysis. Core data were analysed to determine simiarity across invertebrate communities recorded at different stations using SIMPROF in PRIMER v6. The communtiy of organisms present in the lagoon was discussed and the presence of any lagoon specialists and/or non-native species was highlighted. Across the lagoon physicochemical data were found to be within the range expected of lagoonal systems and broadly comparable with the findings of Herbert et al. (2010), although sediments were found to be slightly coarser in nature in the current survey. Brownsea Island lagoon is a percolation lagoon with movement of water through the gravel below the dyke between the lagoon and adjacent littoral habitats. There were also two sluices to the southeast that provided more direct connection to the sea and woodland, marsh and freshwater pools to the west. The extent of the lagoon basin determined from aerial imagery was calculated in GIS to be 16.7 Ha. The main body of the lagoon was dominated by a biotope in the complex: Sublittoral mud in low or reduced salinity (lagoons) SS.SMu.SMuLS (Connor et al. 2004) that included large numbers of the Starlet anemone (Nematostella vectensis). The lagoon margin especially along the western boundary of the lagoon included the biotope Phragmites australis swamp and reed bedsâ?? SS.SMP.Ang.S4. Following Bamber et al. (1997) the subtidal biotopes in the lagoon would be ENLag.IMS.Ann and ENLag.Veg. The biological communities appear to have remained relatively similar between the current survey and that of Herbert et al. (2010). There appears to have been a slight increase in biodiversity manifested through higher taxon counts at comparable stations, although given the increased number of sampling stations a full comparison across the entire lagoon was not feasible. Station BS8 appeared notably impoverished in regards to the biotic community relative to other sampling stations, which likely derives from its partial separation from the main lagoon. The presence of Capitella as a main species here suggests organic enrichment, possibly a result of bird excrement. Station BS12 was close to a sluice and to a site previously sampled qualitatively; it included species that reflect greater saline influence. This preliminary condition of assessment based on historical data from Herbert et al. (2010) indicated that the lagoon has remained in similar condition over the last five or so years. The increased sampling stations in the current survey indicated a greater range of species than previously recorded and the results confirm that the lagoon is home to a range of lagoonal specialist taxa as well as a significant population of the nationally rare starlet anemone (N. vectensis). 20160222