The role of ocean nutrient subsidies for beach and dune ecosystem services

Recent extreme coastal storms and tsunamis have caused erosion and flood damage in coastal communities around the globe. As vulnerability increases, there is growing interest in how to best protect coastal areas without... [ view full abstract ]

Recent extreme coastal storms and tsunamis have caused erosion and flood damage in coastal communities around the globe. As vulnerability increases, there is growing interest in how to best protect coastal areas without compromising other ecosystem services such as recreation, carbon sequestration, and species conservation. Coastal sandy beaches and dunes are of particular interest as sustainable, natural barriers with their shape, and thus their level of protection, dependent on the interaction of sediment and vegetation. Little is known, however, about how these systems are linked to coastal processes, particularly nutrient subsidies from the ocean, and their effect on vegetation. We examined the relationship between ocean productivity and beach grass production to coastal protection in the U.S. Pacific Northwest. Here, coastal communities are exposed to one of the most extreme wave climates in the world, and nearly half of the coast is backed by sand beaches and densely vegetated coastal dunes. We found that seaweeds and seagrasses washing onshore improve the available nutrient pool and that dune plants use these marine nutrients, addressing a deficiency that might otherwise constrain production in dune-building coastal vegetation. Understanding this land-sea relationship is key for evaluating the protection afforded to coastal communities by dunes and how alterations induced by climate change or human activity could shift this relationship.