Title: “The Influence of Direct and Indirect Interactions in Small Biogenic Habitats Associated with the Giant Irish Moss from Basin Head, Prince Edward Island”

Abstract:  Trophic interactions are often explored in literature through a terrestrial scope, with only a small amount of recent detail towards their aquatic counterpart. This Thesis first investigates the role of various complex habitats (Seagrasses, Seaweeds, Mollusks shells, and their associated mimics) as potential mediators of trophic interactions (both direct and indirect), with general conclusions suggesting that as habitats become more complex, prey survival rates increase. This Thesis then shifts to a more narrow focus within the Basin Head Marine Protected Area (MPA), the only known MPA in Prince Edward Island (PEI). The Basin Head lagoon is home to various predator and prey species used in experiments throughout this thesis. However, the main reason for its establishment in 2005 was for the protection and further conservation of the giant Irish moss (Chrondrus crispus), that is exclusively found in this lagoon, which relies on a unique association with the blue mussel (Mytilus edulis) to form small patchy habitats (clumps) on the seabed. The role of these clumps (later referred to as IMBM) as a habitat mediator for various interactions between a non-indigenous predator, the European green crab (Carcinus maenas), the native consumer, the Atlantic mud crab (Panopeus herbstii) and the bottom level European oyster prey (Crassotrea virginica) has not been studied, with results outlying its key influence as a habitat for safe refuge. Finally, there are currently ongoing efforts in the MPA to actively control the ongoing green crab population via various trapping efforts, to little avail. The final chapter of this Thesis investigates a means of potential biological control against this invasive species, with results proving its effectiveness, with potential implications suggesting new methods of trapping for the removal of the green crab.