Ecological Methods Reveal New Microfossil Signals of Cyclone Activity in a Tropical Reef Setting

Microfossils recovered from the nearshore sedimentary record provide an important proxy for quantifying the tropical cyclone event history of a region. Temporally brief allochthonous microfossil assemblages found in shallow water or terrestrial settings and determined to have originated in deeper water are often interpreted to indicate the source sediments are a tempestite. Whilst this method has been employed widely and successfully, because the dynamics of storm event deposition is still incompletely understood, the characteristics of this known microfossil signal are not fully resolved. There has also been little exploration of the possibility that other microfossil signals indicative of high-intensity storm activity may exist that differ from the expected allochthonous assemblage. In this study, we examine foraminifera assemblages before and after a known tropical cyclone event, Cyclone Hamish, with the aim to better resolve signal characteristics. Our results identify no allochthonous microfossil material associated with Cyclone Hamish. Instead, using a collection of methods typical of ecological studies, we find a previously unidentified combination of microfossil signals that are directly the result of a cyclone event. Subsequent sampling in the years following Cyclone Hamish identifies that the surface foraminifera assemblage returns to its pre-cyclone form, but results imply that it is unlikely the community ever reaches steady state.