It Takes Two to Tango: When and Where Dual Nutrient (N & P) Reductions Are Needed to Protect Lakes and Downstream Ecosystems.
Preventing harmful algal blooms (HABs) is needed to protect lakes and downstream ecosystems. Traditionally, reducing phosphorus (P) inputs was the prescribed solution for lakes, based on the assumption that P universally limits HAB formation. Reduction of P inputs has decreased HABs in many lakes, but was not successful in others. Thus, the "P-only" paradigm is overgeneralized. Whole-lake experiments indicate that HABs are often stimulated more by combined P and nitrogen (N) enrichment rather than N or P alone, indicating that the dynamics of both nutrients are important for HAB control. The changing paradigm from P-only to consideration of dual nutrient control is supported by studies indicating that (1) biological N fixation cannot always meet lake ecosystem N needs, and (2) that anthropogenic N and P loading has increased dramatically in recent decades. Sediment P accumulation supports long-term internal loading, while N may escape via denitrification, leading to perpetual N deficits. Hence, controlling both N and P inputs will help control HABs in some lakes and also reduce N export to downstream N-sensitive ecosystems. Managers should consider whether balanced control of N and P will most effectively reduce HABs along the freshwater-marine continuum.
Institute of Marine Sciences, University of North Carolina at Chapel Hill , 3431 Arendell Street, Morehead City, North Carolina 28557, United States.
Hans W
HW
Paerl
Department of Biology, Baylor University , One Bear Place #97388, Waco, Texas 76798, United States.
J Thad
JT
Scott
Dept. of Earth and Environmental Sciences, Wright State University , Dayton, Ohio 45435, United States.
Mark J
MJ
McCarthy
Dept. of Earth and Environmental Sciences, Wright State University , Dayton, Ohio 45435, United States.
Silvia E
SE
Newell
Marine Science Institute, The University of Texas at Austin , 750 Channel View Drive, Port Aransas, Texas 78373, United States.
Wayne S
WS
Gardner
University of Florida Institute of Food and Agricultural Sciences, and Florida Sea Grant College Program, Gainesville, Florida 32608, United States.
Karl E
KE
Havens
Dept. of Earth and Environmental Sciences, Wright State University , Dayton, Ohio 45435, United States.
Daniel K
DK
Hoffman
Department of Microbiology, The University of Tennessee , Knoxville, Tennessee 37996-0845, United States.
Steven W
SW
Wilhelm
Watershed Sciences Department and the Ecology Center, Utah State University , Logan, Utah 84322-5210, United States.
Wayne A
WA
Wurtsbaugh