Biological communities in a human modified coastal landscape
Shellfish aquaculture activities that occur in the intertidal environment can directly and indirectly affect the organisms that live on and within the sediment and higher trophic level organisms (e.g. fish) that utilize the habitat. These activities include the following:
1) Altered species composition and increased densities: Bivalve species compositions are altered by planting economically valuable species at high stocking densities.
2) Aquaculture structure deployment: The placement of structures such as fencing in the intertidal to create pens to outplant oysters into and deployment of nets over clam beds to keep predators out. Further, the practice of outplanting the oysters themselves on the beach changes a naturally soft-bottom habitat type to a mixed soft and hard bottom. These modifications may influence the abundance and type of organisms that can utilize and live in these habitats.
3) Predator management: Exclusion of predators (e.g. crabs, seastars) from aquaculture sites through net placement may increase predator concentrations on nearby beaches that are not protected, potentially reducing important food sources for other predators, such as birds.
To help understand the cumulative impacts of aquaculture we need to determine how community composition in natural, unfarmed habitats compares to communities in shellfish aquaculture habitats. Comparing diversity of three biological communities (epifaunal, infaunal and pelagic) in two very different landscapes the natural, unfarmed sites being relatively flat and simple versus the altered, more complex aquaculture sites is also important from an ecological perspective to understand how organisms respond to, and utilize, anthropogenically altered habitat.
While some aquaculture activities may act to decrease diversity (e.g. increasing commercial species density) others may increase it (e.g. putting oysters on the beach adds habitat complexity). Despite the extent of aquaculture in many regions, and the importance of maintaining diversity, very little research has been done to examine the effects of