Wednesday 5 February 2014 at 3:00pm

Title: “Ecosystem consequences of altered nutrient loads and ratios- more than just eutrophication”

Speaker: Patricia Glibert, Ph.D.
UMCES-HPL

Abstract:
Eutrophication is occurring globally with the most well recognized responses in aquatic systems being hypoxia and harmful algal bloom (HAB) expansion. Yet, the responses of an ecosystem to changing nutrient loads are complicated for many reasons. The amounts, forms, and stoichiometric proportions of nutrient loads vary widely throughout the world in part due to increased nutrient loading (primarily nitrogen) on the one hand, and efforts to reduce nutrient loading (primarily phosphorus) on the other. In many regions, nitrogen loads are now also disproportionately increasing in forms that are chemically “reduced” (ammonium, urea, organic nitrogen) rather than chemically “oxidized” (nitrate). Together these trends mean that nutrient loads in many regions are trending toward higher N:P and higher proportions of “reduced” to “oxidized” nitrogen. This talk will address effects of these changes on a range of scales, beginning with the physiology of algae, and then touching on the consequences of these changes through the food web. Examples will be drawn from a range of estuaries worldwide.

Finally, several projections for the year 2100 related to nutrient loading and HABs will be presented, focusing on output of a coupled, climate-forced, global coastal ocean model for the NW European shelf and East China Seas. We used these models together with climate projections, as well as patterns in nutrient loading and known HAB physiology, to assess how habitat suitability for several HAB species may change. Results of the projections suggest increasing nutrient loads and changing stoichiometric proportions, together with climate changes, may promote regionally differing increases in HABs. These effects may be exacerbated with management efforts targeting single nutrient removal strategies.

Host: J. Sook Chung, Ph.D.