Appearance
Didymosphenia geminata is a freshwater, single-cell, diatom (a type of algae) which attaches itself to a solid surface such as a rock with a stalk. It is light brown, brownish yellow, or white, looking very much like wet toilet paper. Didymosphenia geminata has the texture of wet wool or cotton, fibrous not slimy or slippery, and is not easy to pull apart.

Reproduction
It can reproduce asexually, resulting in large mats. It is able to spread from a single drop of water containing the diatoms. It usually reproduces most readily in cooler temperatures but has been recently known to tolerant of warmer conditions.

Ecological Threat
Didymosphenia geminata can be found in a Found in rivers, streams, and lakes. Prefers flowing water sources. It blankets streams or lake beds; blocks plants from sunlight and animals that eat plants from reaching them; and greatly reduces dissolved oxygen content in water.

Resources

• Global Invasive Species Database - Invasive Species Specialist Group
• Fact Sheet - Arkansas Department of Environmental Quality

Selected Images

Maps

Invasive Listing Sources

• Kentucky Exotic Pest Plant Council - Watch List
• Maryland Aquatic Nuisance Species Plan
• Maryland Invasive Species Council - Invasive Species of Concern in Maryland
• Mid-Atlantic Field Guide to Aquatic Invasive Species
• New Jersey Invasive Species Strike Team 2017 Invasive Species List
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• Pennsylvania's Field Guide to Aquatic Invasive Species
• West Virginia Invasive Species Strategic Plan and Volunteer Guidelines 2014
• Wisconsin's Invasive species rule – NR 40

References