The Alverstoke site is situated within the Portsmouth Harbour Special Protection Area (SPA) and is a Site of Special Scientific Interest (SSSI), with these designations in place, the area, and species within it, are regulated by The Conservation of Habitats and Species Regulations 2010 (Habitat Regulations).
Little Anglesey Lake is a brackish lagoon, which experiences little rise or fall in water levels, these conditions support a very limited range of species. The species which do inhabit this lagoon are highly specialist to these environments. The flora and fauna of this area is considered as the most diverse known in lagoons in south-east England. Two species in particular are present in Little Anglesey Lake, the Lagoon Sand Shrimp (Gammarus insensibilis) and the Starlet Sea Anemone (Nematostella vectensis), which are both specially protected in the Wildlife and Countryside Act 1981.
The presence of these protected species and the nature of the overall environment means that considerations need to be made if working or constructing in the area. Another contributing factor which deterred designs away from The Jackie Spencer Bridge option would require either partial or complete drainage of this lagoon and damming of the downstream channel, which would cause a temporary loss of the lagoon or a temporary reduction in the natural functioning of the system. Thus, creating a degree of uncertainty over the long-term impact of the lagoon following re-instatement, as it is unclear as to what effect and/or how quickly specialist lagoon fauna, in particular the mentioned Lagoon Sand Shrimp and Starlet Sea Anemone, could re-colonise the site if lost.