Section 5. 
Implementation Plan for Nutrients Research 
Problem 
There is growing evidence that human activities have dramatically changed the amounts, 
distribution, and movement of major nutrient elements (nitrogen-N and phosphorus-P) in the 
landscape and have increased nutrient loading to receiving waters. Some of these changes affect 
use of the nation’s aquatic resources, and pose risks to human health and the environment (NRC 
2000). EPA is in the process of developing guidelines that States and Tribes must use to set 
nutrient criteria for our nation’s waters. For waters failing to meet WQS, States and Tribes will 
be required to develop TMDLs to eliminate the causes of non-attainment. Our current level of 
understanding of aquatic ecosystem function is inadequate to allow us to extrapolate knowledge 
of nutrient loading relationships for systems for wdiich we have intensive data to accurately 
predict adverse effects on specific systems with more limited data. NHEERL research will 
provide the scientific information on load-response relationships that are required to develop 
numeric nutrient criteria protective of aquatic life. 
This research implementation plan is ambitious. A complete understanding of the effects of 
nutrients on aquatic ecosystems will require additional research. The projects listed in this plan 
outline the objectives needed to establish the scientific basis for WQC and TMDLs associated 
with nutrients in coastal systems (coastal wetlands, embayments, estuaries, and near coastal 
waters). The decision to focus on coastal waters is based on the complexities of these systems 
and OW’s prioritization of research needs by waterbody type. The most important response 
categories for study are given below: 
Increase in algal production (or carbon supply as defined by Nixon 1995) and/or changes in algal 
community composition, which can result in harmful algal blooms (HABs), are principal 
causative agents for the three following effects: 
1. Low dissolved oxygen (DO) or hypoxia leading to fish kills or loss of shellfish and 
degradation of benthic habitats; 
2. Loss of natural SA V habitat^ important to fish and other biota and due to changes in water 
clarity, epiphytic growth, or smothering by invasive algae; 
3. Shifts in basic food webs leading to loss of commercially important fisheries and overall 
aquatic biodiversity. 
The following pathways define our current understanding of how nutrients affect each of these 
endpoints: 
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