Risk Assessment of Atrazine on Blue Crabs and

Chesapeake Bay Ecosystem

Caitlin AndrewsRussell FordDavid Lucero

Henrietta OakleySatish Serchan

Overview of the presentation

• Atrazine production and application

• Controversy surrounding Atrazine

• Chesapeake Bay and Blue Crab habitat

• Studies of Atrazine on crustaceans, Submerged Aquatic Vegetations (SAV)

• Alternatives to Atrazine

Purpose of this study

Blue CrabCrustaceans

SAVs

Amphibians

Atrazine

Blue Crab Alert

• Blue crabs-the stock has undergone an 85% decline since 1990. (SERC)– Complex migratory life cycle – Salinity gradient – SAVs and zooplanktons

Atrazine Use & Application

• Broad-leafed herbicideBroad-leafed herbicide– Inhibiting the photosynthesisInhibiting the photosynthesis

• 19581958

• Syngenta Corporation Syngenta Corporation

• CornCorn

• 76 to 85 million pounds annually76 to 85 million pounds annually

Atrazine Cont’d

• regulated under water statutesregulated under water statutes

•   Maximum Contaminant Level Maximum Contaminant Level – MCL of 3.0 ppbMCL of 3.0 ppb

• Surface and groundwater persistenceSurface and groundwater persistence– Chesapeake Bay show that levels can exceed Chesapeake Bay show that levels can exceed

100 μg/L (ppb)100 μg/L (ppb) with at least 30 days of with at least 30 days of persistence (EPA 2007)persistence (EPA 2007)

Controversy (EPA Story)

• Low acute toxicity (EPA)

• Not likely to be human carcinogen

• Hormonal effects on lab animals resulted from short term exposure

Dr. Tyrone Hayes Studies

• Scientific Advisory Panel hired by Syngenta

• > 0.1 ppb of Atrazine in surface water effectively turning males into hermaphrodites

• Compare EPA’s MCL 3.0 ppb to 0.1 ppb

Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low

ecologically relevant doses

• Tyrone B. Hayes, et al.

• UC Berkeley Laboratory for Integrative Studies in Amphibian Biology

Demasculinized frogs found near Mid-western Farm Fields where

Atrazine in use

Blue Crabs: An Indicator Species

Indicator Species

Ecological Reasons

Socioeconomic Reasons

Distributes itself based on ecological and

anthropogenic changes

Blue Crab Life Cycle

Megalopae

• Responsible for selecting a secure habitat which will influence their survival into adulthood.

Eel Grass

Smooth Cordgrass

Prefer structural complexity

-3D grass habitats

Actively seeks prey

Megalopae and juveniles live in estuaries in and close to the mouth of the nine large rivers and numerous other creeks that flow

into the Chesapeake Bay.

Atrazine in agriculturally dominated area reach as high as 100 μ /L for periods as

long as 30 days.

Atrazine’s Influence on the Food Chain

Phytoplankton in Chesapeake Bay

354 species of phytoplankton

The bloom and bust cycles of these species of

phytoplankton are complicated with a few species

dominating the resources in different sections of the

estuary.

Green algae and Dinoflagellates – lowest tolerance

(<50μg/L)

Diatoms – higher tolerance (250μg/L)

SAV’s Submerged Aquatic Vegetation

• How atrazine affects SAV’s– Chloroplast function– Oxygen production– Habitat

• Hypoxia• Habitat structure• Predator/prey relationships and trophic cascades

• Studied effects of atrazine on Elodea canadensis

• Found increased levels of fluorescence inversely associated with levels the effective quantum yield of photochemical conversion

• 50% inhibition in Oxygen production when atrazine concentrations were 50-75 ug/l – Damage to Chloroplast

function

• No Oxygen production at 500 ug/l atrazine

Microbioreactor Study

Effects of Hypoxia

• Increases cannibalism by adult Blue Crabs– Chronic hypoxia causes

predator densities to increase in shallower habitats

– Juvenile Blue Crab densities decrease exponentially in response

– Periodic hypoxic up swellings do not have the same affect; adult Blue Crabs migrate to suitable waters

• Changes habitat structure and function

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Hypoxia

• Alterations in predator/prey interactions– Species have different responses and tolerances– Crustaceans have relatively low hypoxia tolerance– Blue Crabs migrate from hypoxic regions, as well as

use them to hunt impaired species

• Change in behavior– Prey dumber by hypoxia – behavioral differences

observed – Species interactions important in ecosystem structure

Crustaceans: the Blue Crab

• How the Blue Crab will be affected by – Loss of SAV production

• SAV’s are primary producers, providing oxygen, nutrient cycling, and serving as food and shelter

– Hypoxia• Chesapeake Bay experiences

periodic low oxygen stress, especially in the summer

• Often has sublethal effects

• Alters habitat structure and function

– Predator/prey interactions

Land Use and Crustacean Abundances

• Negative correlation with agricultural land use and Blue Crab abundances

• Hypoxia associated with Ag land use– Seasonal (summertime)

hypoxia coincides with herbicide/pesticide/ fertilizer applications

– Atrazine part of this mix • supports negative

feedback loop

• Increases hypoxia

Summary

• 85% stock Blue Crab Decline since 1990

• High levels of Atrazine in Chesapeake Bay

• Dr. Tyrone B. Hayes extensive research of Demasculinized frogs

• Seen the affects of Atrazine on SAV

• So let’s just get rid of Atrazine?

Alternative

• University of Kentucky College of Agriculture:

• Reduce the use of atrazine with post-emergence herbicides

• Only use post-emergence herbicides

Pros

• The amount of herbicide needed will be better judged

• Can be cheaper since extra herbicide will not be used

• Can also be cheaper because post-emergence herbicide can be cheaper than pre-emergence

Cons

• May require re-application

• Requires more training and careful management by the farmer

• Can cost more because re-application is needed: more herbicide and energy needed

• Injury to corn crop can occur

Alternatives/Whats next?

• More testing needed; more field data vs. lab data

• Atrazine is one of many chemicals entering the watershed and the specific affects may be difficult to determine

• May have an additive quality, enforcing negative feedback loops in the presence of other pollutants