The complete disappearance of a long standing sacoglossan sea slug population following Hurricane Irma, despite recovery of the local algal community

Abstract

Hurricanes often have large impacts on shallow marine ecosystems and the organisms living within. Here we document the impact of hurricane Irma to a long-standing population of sacoglossan sea slugs in the Florida Keys, USA. For many decades, researchers have been studying a population of clarki ecotype Elysia crispata at a borrow pit (limestone excavation) on Crawl Key, FL. This sea slug has been of interest due to an unusual relationship with its food algae termed kleptoplasty, where the slug sequesters chloroplasts taken from the food algae inside of its own cells and uses them for photosynthesis. Following Hurricane Irma, multiple intensive searches failed to find any E. crispata. This population, which at one point numbered in the thousands, has now been completely eliminated from this habitat for over two years following the hurricane. However, the algal population which previously sustained these slugs has fully recovered. Although this habitat now appears to be ideal for these slugs in terms of food availability, they have failed to recolonize. The reasons for this are unclear, but are likely due to the very short dispersal larval stage in this species. The loss of this population is unfortunate as it was the one best studied populations of photosynthetic sea slugs.