UNC's Paerl Argues for Balanced Nutrient Controls

Excess phosphorus and nitrogen produced by human activities on neighboring land is making its way into coastal waters and degrading both water quality and aquatic life. Although historically the priority has been to control phosphorus, Professor Hans Paerl, from the University of North Carolina, argues that nitrogen imbalance is equally damaging.

He adds that a dual nutrient strategy – tackling both phosphorus and nitrogen surplus -- is necessary to manage effectively this nutrient over-enrichment and resulting habitat degradation of coastal waters in the long-term. His perspective1 is published online in Springer’s journal Estuaries and Coasts.

The combination of human population growth, urbanization, and agricultural and industrial expansion is causing unprecedented and alarming rates of nutrient over-enrichment and accelerated plant growth in receiving waters worldwide. The increasing levels of nitrogen and phosphorus are of particular concern because an excess of these two nutrients promotes accelerated production of plant-based organic matter (or eutrophication) to the extent that excessive production, including harmful algal blooms, contributes to the expansion of marine ‘dead zones’ and leads to the destruction of fisheries habitat.

Paerl shows that the argument for reducing surplus phosphorus alone, to control eutrophication, is idealized and conceptually and technically inapplicable to many freshwater and marine ecosystems. He adds that focusing on phosphorus alone ignores the fact that natural and human influences that affect upstream waters have significant adverse consequences on downstream waters. Therefore, it is essential to look at nutrient control measures and their effects across the entire freshwater to marine continuum, not each one in isolation.

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