Comments to USEPA Science Advisory Board Pertaining to Numeric - - PowerPoint PPT Presentation

Comments to USEPA Science Advisory Board

Pertaining to Numeric Nutrient Criteria for Florida’s Southern Inland Flowing Waters (FSIFW) Tom DeBusk DB Environmental (DBE), Inc. December 13, 2010

Overview

• SAB Charge, with respect to numeric criteria for

FSIFW:

– Data sources appropriate? – Assessment endpoints appropriate? – Compare reference conditions and stressor response

• Existing data demonstrate:

– Macroinvertebrates in south Florida canals are constrained by habitat and flow characteristics, and show lack of response to nutrients – Chlorophyll not an appropriate response variable for nutrients, especially in EAA canals, due to high color – Despite marked variability in water quality (with respect to color, chlorophyll and nutrients) among S. FL canals, excellent fisheries are common

Reedy Creek

Legend Monitoring Stations

Permitted Discharge of Treated Effluent Bonnet Creek

RC-12 RC-14 C-12

Water Chemistry Water Chemistry Macroinvertebrate Macroinvertebrate Flow Flow

2 4 6 8 10km Orange Co. Osceola Co.

US-192 Interstate - 4

Highway Highway County Line County Line Stream Channel Stream Channel

Natural stream Channelized stream Decades-long macroinvertebrate monitoring program in natural and channelized streams in central Florida

Natural stream (RC-14) >>> <<< Channelized stream (C-12)

Macroinvertebrate metrics as a function of water column TP (ug/L) & stream type

Florida Biotic Index Abundance (Individuals per Artificial Substrate)

10 20 30 40 50 5 10 15 20 <100 <100 100-200 200-400 C-12 RC-14

100 200 300 400

Total Taxa Richness

channelized natural

FDEP Forested Creek FDEP Canal Site DBE Canal Site

DBE and FDEP canal macroinvertebrate sampling stations

20 40 60 80 100 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

FDEP sampling DBE sampling

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700

Grab Sample Total P (mg/L) Impaired Healthy Exceptional

SCI Score

6-month Total P (mg/L)

DBE and FDEP macroinvertebrate metrics (Stream Condition Index [SCI]) from canal sampling sites

No evidence of biological community improvement across range of TP concentrations

FDEP’s “Benchmark Streams” exhibit much higher SCI scores than canals. However, even in these systems with favorable habitats the relationship with TP is weak

20 40 60 80 100 200 400 600 800

FDEP Canal Sampling DBE Canal Sampling FDEP Benchmark Streams

SCI Score

Grab Sample Total P (µg/L) Impaired Healthy Exceptional

In south Florida, poor canal habitat is exacerbated by management for floodwater conveyance

Indian Prairie Canal

Removal of shoreline vegetation between DBE’s 1st Qtr (left) and 3rd Qtr (below) sampling events

2007 Lakes Data DB Canal Survey

50 100 150 200 250 100 200 300

Chlorophyll a (µg/L) TP (µg/L)

1 2 3 4 5

TN (mg/L)

Relationships between nutrients and chlorophyll concentrations in south Florida canals (N=14) are compared to water quality in 48 Florida lakes during 2007 (FWC 2008, using Lakewatch water quality data).

Brow003

TN - 1.16 mg/L TP - 123 µg/L

• Chl. a - 5.4 µg/L

S-177

TN - 0.71 mg/L TP - 7 µg/L

• Chl. a - 2.7 µg/L

WPB East

TN - 4.02 mg/L TP - 98 µg/L

• Chl. a - 4.7 µg/L

Three S. Florida canal sites have different water clarity and markedly different TN and TP levels, but all support excellent

• fisheries. Differences in clarity are related to color, not chlorophyll
• r nutrient levels.

South Florida is dominated by canals, so the unique characteristics of these systems (poor macroinvertebrate assemblages; varied and often poor relationships between chlorophyll and nutrients; good fisheries) must be addressed when establishing FSIFW nutrient criteria