pelagic algal communities from desirable (edible, nutritious) to undesirable (non-edible, 
nuisance, HAB species), and 3) shifts in emergent or marsh grass systems. 
Major challenges of this research are to identify practical measurement endpoints (response 
variables) and relate those responses to assessment endpoints (e.g., high performance liquid 
chromatograhy [HPLC] accessory pigments may be useful as measure of changes in the 
phytoplankton community leading to or associated with decreased fisheries production). We will 
investigate development of indices of tropic status associated with high nutrient conditions, such 
as ratios of algal biomass to zooplankton and/or fish, benthic and pelagic community metrics that 
reflect algal composition (e.g., percent blue-greens, and relative abundance of centric and 
pennate diatoms, algal size distributions). Developing load-response relationships, which reflect 
changes in food web structure, will be challenging due to the complex feedback mechanisms 
which accompany degraded habitats in coastal systems (Jude and Pampas 1992, Chow-Frazer 
1998). Increasing phytoplankton biomass may uncouple primary production from grazing. This 
then leads to algal blooms, possibly toxic or noxious algae (HABs) and successions in pelagic 
and benthic communities. The causal mechanisms for HABs remain poorly understood; some 
have always occurred and are entirely natural. However, other blooms are tied to nutrient 
enrichment, thus leading to more frequent and longer lasting blooms as nutrient loading increases 
(NRC 2000). Even more uncertainty exists regarding relationships between nutrient loading and 
basic changes in food webs supporting productive marine and freshwater ecosystems. In addition 
to nutrients, the activity of top consumers can exert strong controls on zooplankton and/or 
phytoplankton affecting phytoplankton size, abundance, and production. Biogeochemical 
processes resulting from blooms (i.e., enhanced sedimentation and redox changes) can cause 
changes in species diversity, size spectrum of organisms, and average tropic level of the 
community. The secondary effects of these water-column and sediment changes may be 
persistent changes in pelagic and benthic species assemblages and alterations in the nutrient 
recycling potential of aquatic habitats. Our approach is to determine nutrient load-response 
thresholds for endpoints reflecting shifts in the food web structure or species composition. 
The Scientific approach will be consistent with the general critical path (Figure 5). Essentially, 
the main components for this research are: 
1. Data gathering and literature review of food web information for coastal food web systems 
will be done collaboratively across Divisions, where existing nutrient-food web/community data 
are available, statistical analysis will be conducted. 
2. Conceptual models that include both bottom up effects models and bottom up-top down 
community models will be developed. The bottom up model (nutrients to primary production, 
Menge 2000) shows influences on aquatic communities, including the formation of some HABs 
and ultimately changes in important fish and shellfish populations. The community level model 
includes interactions among populations that form the food web and identify critical interactions 
that may lead to changes in species diversity, commercial harvest, eutrophication, and designated 
use. 
3. A classification scheme for coastal receiving waters that groups these waters according to 
their sensitivity to food web changes in response to excess nutrients will be provided. Existing 
59 
