82 
Percent of Area Exceeding Criteria 
Figure VIM 1. Comparison of the published mesohaline/polyhaline water clarity criteria 
biological reference curve based on mid-channel water clarity measurements and a 
preliminary example of a shallow-water monitoring-based water clarity criteria biological 
reference curve. 
Source: : U.S. EPA 2003a; Virginia Institute of Marine Science—www2.vims.edu/vecos. 
CHLOROPHYLL A CRITERIA ASSESSMENTS USING 
SHALLOW-WATER MONITORING DATA 
Attainment of the chlorophyll a criteria in the shallow-water designated use areas 
will be based upon the adjacent open-water designated use assessments. As with 
dissolved oxygen assessments, open-water chlorophyll a assessments will rely on 
the mid-channel fixed station data combined with Dataflow and Dataflow calibration 
profile data. These data will be interpolated and analyzed, along with the fixed- 
station chlorophyll a data, using the Chesapeake Bay Program’s interpolator and 
CFD approach described in Chapter 2. The following sections describe the rationale 
for and development of protocols for using the in-situ fluorescence measurements 
from the Dataflow system to assess chlorophyll a criteria attainment in shallow and 
open-water tidal tributaries and embayments of Chesapeake Bay. 
The Dataflow system generates a data set that better represents the spatial variability 
of chlorophyll. The Dataflow cruise track transverses both the open and shallow 
water designated use areas (see Figure VII-10), recording hundreds of fluorescent 
measurements, very quickly and less expensively than the collection and laboratory 
analysis of individual samples. However, the conversion of the fluorescence data to 
chlorophyll a must be done carefully to ensure that they are comparable to the 
chlorophyll o data upon which the chlorophyll a criteria were based. 
chapter vii 
Shallow water Monitoring and Application for Criteria Assessment 
