Meeting Abstract

60.3  Saturday, Jan. 5  Impacts of invasive Gracilaria vermiculophylla on the reproductive ecology of native benthic invertebrates NEWTON, C*; GUIDONE, M; THORNBER, CS; Northeastern University; Sacred Heart University; University of Rhode Island

The recent invasions of the red alga, Gracilaria vermiculophylla, to the Atlantic and Eastern Pacific Oceans have the potential to significantly alter intertidal soft sediment communities. In particular, G. vermiculophylla increases habitat complexity and provides a novel hard substrate in an otherwise two dimensional habitat. Following our observations that the native omnivorous mud snail Ilyanassa obsoleta utilizes G. vermiculophylla for egg capsule deposition, our field surveys demonstrated that the in situ abundance of egg capsules on G. vermiculophylla matched abundances on a native red alga Ceramium virgatum and were at least 11-50 times greater than on all other co-occuring macrophytes. Additionally, through mesocosm experiments, we showed that I. obsoleta preferentially deposits eggs on the invasive G. vermiculophylla over native substrates. However, despite the thick layer of egg capsules found on G. vermiculophylla, no detrimental effects were seen on thalli growth. In contrast, growth of the native red alga, C. virgatum was significantly reduced when egg capsules were present, suggesting G. vermiculophylla can out-compete native macrophytes in areas of I. obsoleta abundance, while facilitating reproduction of the native mud snail. This novel interaction has the potential to significantly alter biological interactions in soft sediment communities through a variety of different mechanisms, including alteration of trophic cascades via the increase in mud snail abundance. Furthermore, facilitation of the reproductive success of I. obsoleta may lead to increases in the occurance of cercarial dermatitis (swimmers itch), as I. obsoleta is a known intermediate host organism.