# Presentation: 238082

## LONG-TERM AND LARGE-SCALE TRENDS IN MERCURY BIOACCUMULATION SUWANNEE RIVER BASIN, FLORIDA

**LONG-TERM AND LARGE-SCALE TRENDS IN MERCURY BIOACCUMULATION SUWANNEE RIVER BASIN, FLORIDA**

## Lia C. Chasar

**Lia C. Chasar**
- Environmental Sciences Institute
- Florida A & M University
- United States Geological Survey
- National Water Quality Assessment Program
- Florida Integrated Science Center
**Ted R. Lange**
- Florida Freshwater Fish and Conservation Commission

## Primary Study Objective

_**Primary Study Objective**_
- To investigate the effects of source strength, cycling, and food web interactions on the bioaccumulation of mercury in stream ecosystems

***USGS National Water Quality Assessment Program (NAWQA)***
***Bioacumulation of Mercury in Stream Ecosystems***

## Food web complexity

- Penaeid shrimp

- Gray Snapper

- Blacktip Shark

**Schooner Bank**
**Florida Bay**

- Atwell, L. et al. 1998. Can. J. Fish. Aquat. Sci. 55:1114-1121
***Adapted by Robin Stewart, USGS, Menlo Park***

**Food web complexity**

- ↑trophic level ≈ ↑15N ≈ ↑Hg burden

**Notes:**
The relationship between del-15N and Hg in fish tissue (specifically apex predators) should provide information on the relative importance of trophic complexity to contaminant accumulation across systems

## Questions

**Stable isotopes useful in establishing trophic relationships in riverine systems? **
**surface water run-off**
**tributaries**
**sharp gradients in water chemistry and productivity**

## Questions

**Stable isotopes useful in establishing trophic relationships in riverine systems? **
**surface water run-off**
**tributaries**
**sharp gradients in water chemistry and productivity**
**Influence of local biogeochemical processes on  bioaccumulation of contaminants (sp. Mercury) in riverine systems?**
**i.e. variability within a river reach vs. entire basin?**

## Drivers for fluctuations?  (no apparent change in atm. dep.)

**Drivers for fluctuations?  (no apparent change in atm. dep.)**

**Notes:**
Although. Dep stations (from Okeefenokee and  Chassahowitzka) have only been running since 1996, their hasn’t  been any apparent overall decline in mercury dep in the basin...with samples from Fowler’s Bluff from this past year, another spike in values 

## Questions

**Stable isotopes useful in establishing trophic relationships in riverine systems? **
**surface water run-off**
**tributaries**
**sharp gradients in water chemistry and productivity**
**Influence of local biogeochemical processes on  bioaccumulation of contaminants (sp. Mercury) in riverine systems?**
**i.e. variability within a river reach vs. entire basin?**
**What drives temporal trend in mercury body burden of fish in Suwannee River basin?**

## The Suwannee River Basin

- (courtesy of Suwannee River Water Management District)

**Gulf of Mexico**

**Gulf of Mexico**

**Georgia**
**Florida**

*Suwannee River*

*Santa Fe River*

*Withlacoochee River*

*Alapaha River*

**2002**

**2002**

**2002**

**1993, 2002**

**1993, 2002**

**1993, 2002**

**1993, 2002**

**1993, 2002**

**1993, 2002**

**1993**

**1993**

**1987-2002**

**Notes:**
Compiled all of the FFWCC, Georgia DNR, and USFW data for Hg in LMB for the entire basin, pulled archived crayfish from FFWCC freezers and ran for THg and MeHg, and conducted a new transect including all the stations sampled in 1993 – adding several to fill in gaps of mid-upper Suwannee and collecting crayfish, redbreast sunfish and LMB...SO expanding long term data set by adding at least a few point other than lower Suwannee, evaluating smallscale (intra-station, few river miles) variability relative to basin scale variability, because of the gradients in water chemistry looking at influence of geochemistry

## River mile upstream from mouth of Suwannee River

- r2=0.89

- r2=0.68

## Role of 

**Role of **
**Trophic Complexity?**

## 15N only slight decrease with distance upstream

******15****N only slight decrease with distance upstream**
**Mean ********15****N = 5.04 (****±****1.19)****‰**

**Carbon**

**Nitrogen**

## Transport/transformation?

**Transport/transformation?**
**(pH, DOC vary in **
**both space and time)**

**Notes:**
Suwannee River Water Management District has water quality stations throughout the SRB (sampled monthly from 89 on?)

## Conclusions

- THg body burden in all three consumers has experienced decrease since 1987, however values have peaked repeatedly
- THg increases with increasing distance upstream for crayfish, redbreast sunfish and largemouth bass
- Stable isotopes indicate that local biogeochemical processes and mercury transport/transformation are likely more important than trophic level shifts in mercury bioaccumulation

## What’s next?

_**What’s next?**_

## Future Research:

**importance of water level**
**natural variability**
**seasonal wetting/drying river margins **
**extreme events**
**extended drought**
**flooding**
**forcing factors **
**pH**
**DOC**
**additional Hg loading**
**moving further downstream**
**continue decrease?**
**estuary as mixing zone?**
**pH, quality of DOC, SO****4 ****-**
**resource management**
**temporal trends/advisories**

_**Future Research:**_

## Project Support

- Florida Department of Environmental Protection
- Florida Fish and Wildlife Conservation Commission
- US Geological Survey
- Florida State University
- Washington State University

_**Additional Acknowledgements**_
- FDEP
- Kerry Tate
- Tom Atkeson
- Don Axelrad
- FFWCC
- Doug Richards
- Beth Sargent
- WSU
- Ray Lee
- USGS
- Terry Petrosky
- Lori Lewis

*Lookin’ for bugs in all the wrong places...*