Shifts in species abundance of large benthic foraminifera Amphistegina: the possible effects of Tropical Cyclone Ita

Abstract

On the Great Barrier Reef (GBR), the large benthic foraminifera Amphistegina lobifera, A. lessonii and A. radiata occur in shallow (<30 m) areas and have a clear distribution gradient. In April 2014, Severe Tropical Cyclone (TC) Ita impacted the northern region of the GBR. We surveyed the leeward slope of Yonge Reef at 6 and 18 m, in August 2013 and 2014. Results showed an overall decline in abundance of Amphistegina and a shift in proportion at both depths between 2013 and 2014. The shallow-dweller A. lobifera was severely affected; however, the deep-dweller A. radiata and the generalist A. lessonii only declined at 6 m and increased in abundance at 18 m. Patterns observed are likely linked to the occurrence of TC Ita. We propose that differing population-level source–sink dynamics should be considered when exploring persistence and recovery patterns over depth in foraminiferal communities.