Loss of an erect sponge on a rock reef in Long Island Sound (north-west Atlantic)

Stratford Shoal is a topographic high dividing the west and central basins of Long Island Sound (north-west Atlantic). The southern end of the shoal has a linear, north–south-tending boulder reef along the crest. Repeated observations of the reef using remote and diver-held cameras from 1991 to 2010 found an apparently stable epibenthic community dominated by Haliclona oculata (branching sponge), Astrangia poculata (northern star coral), Mytilus edulis (blue mussel) and erect bryozoa. In 2012, when the boulder reef area was imaged as part of a benthic habitat mapping project, A. poculata was still abundant, but no H. oculata was found. A number of mechanisms (e.g. species interactions, disease, recruitment failure, thermal stress, sediment loading, freshwater input and physical disturbance) may have contributed, individually or synergistically, to the community shift. However, because of the ad hoc and aperiodic nature of the observations, drivers of the shift are indeterminate. As a result, whether the observed changes reflect a short-term disturbance or a long-term community state remains unclear, as do the effects of changes in the identity of the dominant species.