State Water Resources Research Institute Program


Project Id: 2010MD206B
Title: Effects of Phragmites invasion on mosquito production in stormwater wetlands
Project Type: Research
Start Date: 3/01/2010
End Date: 2/28/2011
Congressional District: MD-005
Focus Categories: Invasive Species, Wetlands, Ecology
Keywords: mosquito, predation, competition, Phragmites, stormwater wetlands,
Principal Investigators: Leisnham, Paul (University of Maryland); Baldwin, Andrew
Federal Funds: $ 24,178
Non-Federal Matching Funds: $ 62,621
Abstract: Overall Goal: The goal of our research is to investigate the impacts of the invasive plant Phragmites australis on the production of the mosquito Culex pipiens in stormwater wetlands.

Problem: Stormwater wetlands can provide cost-effective water quality treatment and other benefits, but their shallow water and emergent vegetation can sometimes present habitats for mosquitoes that pose considerable public health threats. The non-native genotype of Phragmites is a widespread invader of wetlands throughout much of the US. Phragmites forms dense monocultures that displace native plant communities, reduce plant diversity, and likely alter the characteristics mosquito habitats. Although effects of Phragmites on native plant communities are well documented, no studies have examined the impacts of Phragmites on mosquito production. Preliminary results indicate that Phragmites has different nutrient removal rates compared to native plants which may alter the microbial food resources available to mosquitoes. Phragmites may also alter access of predators to mosquitoes by changing the physical structure of habitats and moderate a range of biotic (e.g., litter detritus) and abiotic (e.g., water temperature and insolation) factors that directly or indirectly (e.g., via food resources) affect mosquito production. This will be the first research of the impacts of Phragmites invasion on mosquitoes and thus it addresses a question of importance to water resource management and human health.

Objectives: The specific objectives of this project are to:

  1. Conduct a laboratory experiment on the effects of temperature, shade, and detritus type on the production of Cx. Pipiens.
  2. Conduct a greenhouse experiment on the effects of plant species (Phragmites australis, Typha latifolia, and Juncus effuses) on the production of Cx. Pipiens through changes to nutrient removal rates, microbial production, and predation from the invertebrate Notonectid undulate (backswimmer), and
  3. Conduct a field survey of mosquito communities in stormwater wetlands in Maryland with varying invasion of Phragmites.

Methods: In a laboratory experiment, microcosm cups with varying densities of larval Cx. Pipiens will be provisioned with detritus from either Phragmites or one of two native plants (Typha latifolia and Juncus effuses), and be subjected to high or low light treatment, and high or low temperature. Survivorship, mean development time, and mean body size of Cx. Pipiens from each cup will be used to calculate a composite index of population production based on per capita rate of population increase. In a separate greenhouse experiment, container mesocosms planted with either Phragmites, Typha latifolia, or Juncus effuses will have larval Cx. Pipiens added. Half of the mesocosms will be subjected to a predation treatment by adding Notonectid undulate. Each mesocosm will receive daily nutrient additions to mimic stormwater influent and have their population production of Cx. Pipiens calculated. The effects of temperature, shade, detritus type, mosquito density, nutrient removal rates, and predation on the production of Cx. Pipiens will be tested using linear models. In a field study, wetlands of varying invasion (percentage) of Phragmites will be surveyed for mosquitoes and water chemistry measures taken. Relationships between mosquito densities, water quality measures, and plant composition (including percentage Phragmites and species richness) among wetlands will be analyzed using regression analyses.

Outcomes: Our research will be important to wetland managers, mosquito-control professionals, scientists, and the general public, and important outputs will include the first published articles and presentations on the effects of Phragmites invasion on mosquito production and a set of recommendations to help manage Phragmites and mosquitoes in stormwater wetlands.

Progress/Completion Report, 2010, PDF

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