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University of Michigan Biological Station

The University of Michigan Biological Station (UMBS) was founded in 1909.

Social

Modes of chemical exposure: Groundwater and surface water entry of atrazine and effects on social behavior

Aquatic
Project Abstract: 
Aquatic organisms commonly encounter anthropogenic pollutants in their environment that induce negative physiological and behavioral changes. Previous work on chemical dispersion has established that exposure pattern of contaminants can differ depending on the method that the toxins are introduced to aquatic system (Edwards and Moore, 2015; Lahman and Moore, 2015; Sanford, 1997; Wolf, et al., 2014). The variation of chemical plume structure as a result of mode of entry may cause differing exposure regimes to a contaminant instigating varying effects to behavioral responses of aquatic organisms. The goal of this study is to understand how differing routes of exposure to toxins may alter social behaviors displayed by aquatic invertebrates. This study will use agonistic encounters in the native crayfish, Orconectes virilis, as a behavioral assay to investigate impact of sublethal concentrations of atrazine delivered in varying modes of introduction. Preceding research has shown that agonistic behavior, a social behavior commonly exhibited by crayfish, is important ecology and allocation resources for these keystone species (Bovbjerg, 1953; Martin and Moore, 2010; Wofford, Earley, and Moore, 2015). Given the dearth of research within this area of ecotoxicology, a significant gap in knowledge exists relating toxicant entry and organism behavior and I aim to fill this gap with my dissertation work.
Investigator(s): 
Alexandra Nicole Steele
Paul Moore
Years Active: 
2017
Methods: 
This experiment will have a 2 x 4 fully factorial design with the first factor being mode of exposure (overland runoff exposure or groundwater exposure) and the second factor being concentration of atrazine (0, 40, 80, and 160 µg/L). Each treatment will have 15 trials, creating a total of 120 trials to be performed in this study. Each animal will be used only once during the trials. An artificial stream system consisting of six flow through streams (165 × 35 × 40 cm L x W x H) will be constructed using cinder blocks lined with 4 mm polyethylene sheeting in order to expose crayfish to atrazine. Unfiltered water will be pumped into each stream from the Maple River at a constant flow of approximately 3.0 cm/s. O. virilis crayfish will be exposed to atrazine solution in pulses at a flow rate of 2.78 x 10-2 mL/s. Pulsed exposure will be utilized in order to mimic natural runoff events containing anthropogenic pollutants (Cold and Forbes, 2004; Handy, 1994). Pulses will be 1 hour in duration with 2 hours allowed between each pulse. Crayfish will remain in the exposure arena for a total of 24 hours allowing each crayfish to experience 8 pulses of atrazine exposure. To mimic waterborne exposure, atrazine solution will be delivered in the center of the water column of the artificial stream exposure arena. To mimic groundwater entry, atrazine solution will be delivered 2.5 cm beneath the substrate of the exposure arena (Edwards & Moore, 2014). The atrazine solution will be dispensed to the artificial streams using a gravity feed system. The gravity feed system will receive atrazine solution periodically via a weighted tipping bucket system. Immediately following removal from the exposure arena, fight trials with experimental crayfish and unexposed, socially naïve crayfish will occur for each exposure treatment. Opponents will be sized matched within a maximum of 10% difference in carapace length. Crayfish will be allowed to interact for 15 minutes in each fight trial (Wofford, Earley, & Moore, 2015). Each trial will be video recorded and Xcitex tracking software will be implemented to capture aggressive encounters of the crayfish. Fight frequency, duration, intensity, and time spent at each intensity level will be calculated and analyzed. Intensity levels will be determined using a pre-established crayfish ethogram (Martin & Moore, 2010). Agonistic behavior will be compared between treatments in order to determine if route of exposure to toxins differentially affects fighting behavior in crayfish.