Pesticide Usage

 

 

Biological Monitoring

March 13, 2007

A PDF of the Lab lecture PowerPoint is available: Click Here

Introduction:

Assessing the risk associated with human impacts is a critical step in maintaining standards of human and ecological health. Models for risk assessment have been proposed at all organizational levels, from the cellular to the community structure level. More complex models are generally more representative of an ecosystem, but information is often more difficult to evaluate. Simpler models are generally easier to evaluate but they may not be representative of the ecosystem. In addition, methods that better represent an ecosystem typically require considerably more time, effort, and cost. Acute toxicity tests monitor toxicity resulting from exposure of less than a few days. Chronic toxicity tests monitor toxicity resulting from exposure greater than a few weeks. Sublethal toxicity tests study effects of a toxic chemical on an organism below the threshold that would kill that organism. Mortality tests are run at a threshold that will result in mortality to some of the test organisms. Population studies are used to monitor changes of a community of organisms in an ecosystem, generally in reference to a human impact. The USEPA provides a publication on Biomonitoring.(EPA Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms Fifth Edition. October 2002. EPA-821-R-02-012). You can download a copy of this document by clicking here.

A method for assessing human impact on streams has been developed by a research group at VA Tech. This research report can be accessed by clicking here on Engel and Voshell 2002.

Objective:

To present several Biomontitoring methods which may be used to determine the effects of materials which may originate from agricultural and urban pest control activities on test organisms.

Organizational Levels:

There are a variety of levels on which biomonitoring actvities may be conducted. These include:

• Subcellular to Cell
• Cell to Tissue
• Tissue to Organ
• Organ to Organ System
• Organ System to Organism
• Organism to Populations
• Populations to Communities
• Communties to Ecosystems
• Ecosystems to Ecoregions (Biosphere)

Some definitions:

• Population - a group of organisms of the same species in the same location.
• Community - all of the populations in a particular location.
• Ecosystem - characteristic system resulting from the interactions of communities with abiotic components
• Ecology - the study of interrelationships of organisms and their environment.

1. Community Level: Biological Diversity in Stream Pollution Studies

Comparison of the diversity of macroinvertebrates living downstream from two local watersheds:

• Stroubles Creek
• Tom's Creek
• Both of these creeks will also be compared to a MAIS index, which is a set of standards that may be used to determine stream health in the Mid Atlantic Highlands Ecoregion.
• Terms Describing Water Habitats
  • Plankton - float on the surface of the water
  • Nekton - live suspended in the water with the ability to migrate moving independently of the currents
  • Benthic - organisms that live on the bottom of the body of water or on objects projecting from the bottom
  • Lotic - faster moving bodies of water such as streams and rivers.
  • Lentic - more still water such as lakes and ponds.

    (Most biomonitoring uses benthic macroinvertebrates or nektonic fishes)

• Two major types of metrics use are Structural and Functional
  • Structural - describes the composition of species in the ecosystem.
    • The following are structural categories of metrics.
      • Abundance - The total number or organisms or the total number in a given taxon or taxa. (e.g. Total organisms, Total organisms in an individual taxon)
      • Richness - The number of species. (e.g. The total number of species; EPT Index = The total number of Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies) (these orders are typically sensitive species and are not typically abundant or diverse in polluted streams)
      • Composition - The percentage of total species that are made up by a select group of species. (e.g. % EPT = the percentage of the total species that are from the mayfly, stonefly, and caddisfly orders.)
      • Balance - The extent to which a few species account for the total number of organisms. (% 5 Dominant Taxa = Of the 5 most common species how much do they account for the total abundance) Typically in polluted streams a few tolerant organisms will survive and dominate.
  • Functional - describes the role or function of the species in the ecosystem.
    • The following are functional categories of metrics.
      • Trophic Levels (e.g. % shredders; % scrapers etc.) - This may be related to the paper Whiles et al. (1993);
      • Habits (e.g., % Haptobenthos = % of organisms that cling or crawl on rock surfaces, this can be used as an indicator of sedimentation effects on habitat quality

2. Organism in a Solid Matrix: Biomonitoring Using an Earthworm Bioassay

Single Species: Earthworm (Eisenia foetida) contact filter paper and burrowing tests to evaluate the sub-lethal acute toxicity and acute mortality.

Earthworms play a vital role in soils; their feeding and burrowing activities enhance soil structure, fertility and incorporate plant residues into soil. Toxicity testing of chemicals on earthworms can give valuable information on the potential effects of pesticides on them. In addition, earthworms have several characteristics that make them suitable key bio-indicator organisms. They are ubiquitous; are large and easy to handle; can be readily collected and identified; are known to be affected by and take up a number of organic and inorganic pollutants; are easily bred in the laboratory; and their longevity makes it likely that few controls will die during the test period (Goats and Edwards, 1988). It has been proposed to use the earthworm as a marker species for soil invertebrates, as the rat and fathead minnow serve as marker species for mammals and fish, respectively (Roberts 1984). The earthworm has been selected as a key indicator organism for ecotoxicity testing of industrial pollutants by: the European Economic Community (EEC); the Organization for Economic Co-operation and Development (OECD); the Food and Agriculture Organization of the United Nations (FAO); the American Society for Testing Materials (ASTM, 1995); by many national pesticide registration authorities including the US EPA (Greene et al., 1989); and environmental pollution committees (Goats and Edwards, 1988). Earthworms are becoming widely used in testing the registration of new chemicals, particularly pesticides (Leland et al, 2001, 2003).

Several studies are currently used to study the effects of toxic chemicals on earthworms. The simplest of these involves exposing earthworms to toxic compounds in solutions or on wet filter paper. The next level of complexity is exposing earthworms to toxic compounds in contaminated soils. This is more complex because the sorption of the toxic compounds onto soils must be considered; it is for the same reason, however, more environmentally realistic. The next level of complexity is population studies of earthworm communities in the field. Although this is obviously the most environmentally realistic situation, it also generates highly variable data.

The results of some tests will be provided from an EPA earthworm avoidance test. This test is used to see if earthworms avoid soils contaminated with a given toxicant. A test that was developed at VA Tech measures the rate that earthworms burrow into soil when exposed to a bright light in order to evaluate sublethal toxicity. One of the sublethal effects of intoxicated earthworms is a “curling effect”. Earthworms showing this effect will curl at tight angles particularly at their posterior end.

 

3. Organisms in an Aqueous Matrix: Biomonitoring Using Daphnia magna

Daphnia magna is used routinely to evaluate the toxicity of aqueous runoff or aqueous extracts.

In Lab we will set up a test on toxicity of deltramethrin contaminated soil leachate. The general test conditions that we shall follow are decribed below. Tables 13 and 14 (pages 53 & 54) EPA Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms Fifth Edition. October 2002. EPA-821-R-02-012

Details regarding Daphnia as a test organism can be found in (EPA Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms Fifth Edition. October 2002. EPA-821-R-02-012; pages 140-158) For a PDF copy click here.

Classification of Daphnia
Phylum: Arthropoda
Class: Crustacea
Subclass: Branchiopoda
Order: Cladocera
Family: Daphniidae
Subfamily: Daphnii
Genus-species: Daphnia magna

Laboratory Exercise:
We will be testing the environmental effects of Decis 12EC (deltamethrin/insecticide) spill on soil using a Daphnia magna bioassay procedure. Data will be collected on 1) a deltamethrin standard dilution series ranging from 0.01 to 0.000001 µg/mL (10 ng to 0.001 ng/mL), 2) a contaminated soil extract 20 g/100 mL dilution series (200,000 to 20 µg/mL) and. 3) ) a control soil extract 20 g/100 mL dilution series (200,000 to 20 µg/mL).

5 Daphnia magna will be placed into 30/50 mL beakers containing 30 mL test solution and observed at 24 and 48 hours. The class will be divided into 4 groups and each group will be responsible for setting up and collecting data on one replicate group in each of the three dilution series tests. Data sheets for each group will be provided. The data will be pooled and returned to the students Friday, March 16, 2007.

 

Laboratory Report:

Students should submit a final report including comparison of the results (log probit graphs) and a brief discussion during lab. Log Probit paper is available: PDF-three cycle, PDF-four cycle, or PDF-five cycle

Report will be due in lab Tuesday, March 27, 2007

Homework Assignment:

We have provided two papers relating pesticide use to biomonitoring. Please try to grasp general concepts in these papers—the abstract, introduction, and discussion should suffice. We do not expect you to know methods and materials, etc. Answer the questions below and turn them in at the beginning of lab Tuesday, March 29th 2005.

Reading #1
Miskimmin, B.M. & D.W. Schindler. 1994. Long-term invertebrate community response to toxaphene treatment in two lakes: 50-year records reconstructed from lake sediments. Can. J. Fish. Aquat. Sci. 51: 923-932. (PDF of this article= Click Here)

1. What were some of the post-toxaphene changes that occurred in the lakes to the following invertebrates?

a) Cladocerans (Bosmina & Daphnia species)
b) Chaoborus species
c) Chironomids

2. Give one reason why the piscicide toxaphene was banned.
3. Did toxaphene have a residual effect on the stocked trout?

 

Reading #2

Hanazato, T and H. Hirokawa. 2004. Changes in vulnerabiliyt of Daphnia to an insecticide application depending on the population phase. Freshwater Biology. 49:402-409. (PDF of this article= Click Here)

1. What position do Daphnia play in the food chain?
2. Briefly state the objective of this study.
3. What do the results of these two workers show?

 

References:

EPA Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms Fifth Edition. October 2002. EPA-821-R-02-012

Engel, S. R. and J. R. Voshell. 2002. Volunteer biological monitoring: Can it accurately assess the ecological condition of streams? American Entomologist. 48: 164-177.

Greene, J. C.; Bartels, C. L.; Warren-Hicks, W. J.; Parkhurst, B. R.; Linder, G. L.; Peterson, S. A. and W. E. Miller. 1989. Protocols for short term toxicity screening of hazardous waste sites. EPA/600/3-88/029. U.S. Environmental Protection Agency, Corvalis, OR,

Goats, G. C. and C. A. Edwards. 1984. The prediction of field toxicology of chemicals to earthworms by laboratory methods. In Earthworms in Waste and Environmental Management. Edwards, C. A.; Neuhauser, E. F. Eds.; SPB Academic Publishing: The Hague., pp.283-294

Leland, E., D. E. Mullins, and D. F. Berry. 2001. Evaluating environmental hazards of land applying composted diazinon using earthworm bioassays. J. Environ. Sci. Health, B36(6), 821-834.)

Leland J. E., D. E. Mullins, and D. F. Berry. 2003. The fate of 14C-Diazinon in compost-amended soil, and uptake by earthworms. J. Environ. Sci. Health B38 (6):697-712

Roberts, R. L. An Assessment of the Potential Hazards of Pesticides and Other Chemicals to the Earthworm Eisenia foetida. Ph. D. Thesis. University of Kentucky.