Global Change and Biodiversity Linkages across the Sediment–Water Interface

Abstract

umans are dramatically altering the biosphere through fossil-fuel burning, residential and industrial development, agriculture, harvesting of natural resources, and long-distance transport of materials. These human activities can cause large-scale changes in marine ecosystems, including the diverse communities of organisms living in marine sediments (the soft-bottom benthos). The seafloor effects of some anthropogenic perturbations are mediated through the atmosphere and thus are inherently regional or global in scale; examples include ocean warming and sea-level rise, potentially resulting from the production of greenhouse gases. Other human impacts, such as coastal-zone eutrophication, species introductions, mariculture, and bottom fishing, may occur as single events on local scales (e.g., on the scale of an estuary or a mangrove swamp), but are becoming so widespread that they should be considered global phenomena. All these impacts are components of anthropogenic global change, with major potential to alter ecosystem services, patterns of biodiversity, and interactions between benthic and water-column habitats (known as bentho-pelagic coupling). Our goal in this article is to highlight potential effects of global change on marine soft-sediment ecosystems, which cover more than 80% of the ocean floor. We focus on alterations of biodiversity within marine sediments and linkages between biodiversity in the sediments and overlying communities. In particular, we address the ways in which changes in the biota within sediments may propagate upward through the epibenthos (organisms living on the seafloor), through emergent vegetation (e.g., mangroves, seagrasses, saltmarsh plants), and into the pelagic realm. We also consider how shifts in water-column biodiversity may propagate downward into the benthos.