Environments - Inshore Basins
Castle Harbour, a large basin at the northern end of the island chain, has a narrow entrance to the north of Ferry Reach and the north lagoon, and a wide island-dotted entrance to the south through Castle Roads. Present day connections (access) to both Castle Harbour and Ferry Reach are restricted by land fill for (or from) the Kindley Field airport and the construction of the Longbird Causeway.
At its deepest point, Castle Harbour is about 20 m deep with most of the basin between 6 and 12 m. In water deeper than 10 m, the sediments are mainly lime muds while in shallower depths, sediments are muddy sands.
In the central part of the basin, small pinnacle reefs
reveals that they were formed principly by colonies of Diploria
labyrinthiformis much larger than those presently inhabiting
the reefs and major contributors were Millepora (Which
is now quite rare on the reefs) and Agaricia. The
contrast in fauna is possibly due to the killing of the larger corals during
the construction of the airfield.