Spatial and Temporal Scales of Disturbance to the Seafloor: A Generalized Framework for Active Habitat Management
Simon F. Thrush, Carolyn J. Lundquist, and Judi E. Hewitt
Abstract. The direct effects of marine habitat disturbance by commercial fishing have been well documented. However, the potential ramifications to the ecological function of seafloor communities and ecosystems have yet to be considered. Ecological research has demonstrated that natural disturbance processes play an important functional role in seafloor ecosystems by affecting spatial heterogeneity. When the space and time scales of human disturbance are greater than those the natural ecosystems are adapted to, changes in community structure and function are inevitable. Changes restricting the size, density, and distribution of organisms can lead to functional extinction and threaten resilience at all levels of biological diversity. This is particularly true in soft-sediment ecosystems, where the organisms create much of the heterogeneity within the habitat and also play crucial roles in many processes. Thus, there is a need to develop a scientific framework for the management of seafloor habitats, focusing on sustaining fisheries and maintaining biodiversity. Simple heuristic models can indicate disturbance regimes that, through their frequency, extent, or intensity, could result in catastrophic changes across the seafloor landscape . Our model implies that when disturbance is infrequent relative to recovery time and only a small proportion of the landscape is affected, the system is stable, but when the disturbance frequency is shorter than the recovery time and/or a large proportion of the system is disturbed, the system may flip into an altered state. Once features have been lost, it may not be a simple matter of reducing the disturbance regime to ensure their recovery. Even such a simple model emphasizes the need to understand the scales of mobility and the processes affecting recovery. We need to carefully and explicitly consider the implications of alterations of these ecosystems; they may not only reflect loss of conservation and natural heritage values but also loss of opportunity and the ecosystem services provided by diverse and heterogeneous seafloor ecologies.