 Nutrient Limitation What’s happening in the Chesapeake Bay and how does it compare to our results?

Past Data

Seasonal Trends  Winter shows little growth  Light is limiting  Spring shows elevated growth in both P and N+P treatments but not in the N treatments  P is limiting  Summer shows elevated growth in N and N+P treatments but not in P treatments  N is limiting

Seasonal Trends

Our Results How do our class results compare to the bioassays conducted by other researchers that have been done during the same season of the year? ?

Why?  The input of nitrogen into the Bay is closely tied to the annual flow of water into the Bay.  Freshwater inflow is generally much richer in nitrogen than phosphorus but this does not tell the whole story.

Oxygen Concentration (mg per liter) JFM A MJJASOND River inputs of nitrogen and phosphorus are especially high in the late winter and early spring. Phosphorus moves into the well-oxygenated sediments. Sediments remove nitrogen from the water during late spring/early summer. Anoxic sediments release phosphorus into the water column during the late summer and early fall. MONTH

The Big Picture  Year-round reductions in phytoplankton will only be possible if inputs of both nitrogen and phosphorus are reduced  The primary issue now hampering the Bay’s clean-up is summoning the political and social will of citizens within the watershed to finance the implementation of these nutrient control technologies