Maryland Anglers Asked to Use Wader Sterlization Stations To Prevent Spread Of Invasive Didymo
By Maryland Department of Natural Resources
Published: June 7, 2008
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Six new cleaning stations installed along Gunpowder Falls A photo of a fishman at the wader wash station.Baltimore County — Since discovering Didymo for the first time in Maryland last month, the Maryland Department of Natural Resources (DNR) has set up six wader sterilization stations throughout the tailwaters of Gunpowder Falls, to prevent further spread of this and other aquatic invasives.

Didymo is an algal diatom that forms long stalks which combine to form heavy, thick mats that can smother a stream bottom. Didymo mats, also called “rock snot,” look slimy, but feel like wet cotton or wool, and can be white, yellow or brown. The stalks can persist for two or more months after the diatoms die, causing habitat damage for an extended period of time.

“Didymo and other aquatic invasive species seriously jeopardize the health of our rivers, streams and Bay,” said Don Cosden, an assistant director with the DNR Fisheries Service. “Not only do these exotic species disrupt the local ecosystem, they are capable of permanently displacing or eradicating native species, including trout and other freshwater fisheries. We need anglers and other recreational users of this area to take 60 seconds to sterilize gear, and protect the waters they enjoy.”

Although there is no human health risk associated with the species, DNR is developing an aggressive plan of attack to deal with this invader, including asking anglers and other outdoor enthusiasts to use extra precautions when moving from one stream or lake to another. Movement of a single cell can contaminate a new waterway, and once Didymo is established, it can cover and suffocate a stream bottom.

“Proper angler protocol is the main line of defense in preventing the introduction and spread of aquatic invasives,” said Jonathan McKnight, chair of DNR’s Invasive Species Team. “We are strongly urging anglers to properly sterilize their waders and all gear that comes in contact with the water prior to using the gear in a new location.”

DNR strongly urges citizens to sterilize boots, paddles, boats and anything else that comes into contact with stream water; anglers may want to consider having two sets of equipment in order to move safely from one spot to another. DNR also advises against using felt bottom boots and waders – the worst culprits in the spread of aquatic invaders – replacing them with non-porous materials. If felt waders are used, they should be completely immersed in salt solution before being used in another location.

Proper sterilization procedures include:

    * Before leaving a stream, scrub away all dirt and debris.
    * At home or at a wader sterilization station, disinfect equipment by scrubbing or soaking in at least a 5 percent salt solution (2 cups salt/2.5 gallons water) for 60 seconds and then letting dry completely or scrub with dish detergent and rinse well.
    * If disinfection is not possible, let equipment dry completely for at least 48 hours before next use.

Currently, wader sterilization stations are set up at six popular crossings along Gunpowder Falls: Masemore Road, Bunker Hill Road, York Road, Blue Mount Road and both north and south lots at the Falls Road crossing. In the coming weeks, stations will also be set up along the Casselman, Youghiogheny and Savage Rivers.

Originally found in Scotland and extreme northern Europe and Asia, Didymo has been transported worldwide. Recently, the species has been found in the northeast and mid-Atlantic regions of the United States. In many cases, anglers have unknowingly transported the diatom on their fishing gear.

DNR urges anyone who observes Didymo on rivers other than the Gunpowder Falls to contact Don Cosden at 410-260-8287 as soon as possible.

For more information on Didymo and other invasive species, visit http://www.dnr.state.md.us/invasives/.

 

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What is Didymo?
Didymosphenia geminate (aka “Didymo” or “rock snot”) is a freshwater diatom, a single-celled, benthic algal species that is native to the far northern regions of the Northern Hemisphere—including North America, Europe and Asia---where it is typically found in colder, low nutrient, and high clarity streams.  In areas where Didymo has become a nuisance species, its thick blooms can achieve thicknesses of 10 inches or more and smother the rocky substrates of low turbidity, often pristine streams, rivers, and sometimes lakes with nearly impenetrable mats and 2-3 feet long strands that resemble wet wool or cotton.  Didymo mats/strands of cells and extra-cellular stalks that appear to be resistant to biodegradation can be yellow, brown, or even gray to whitish in coloration, and is often mistaken for fiberglass or toilet tissue.   Didymo attaches securely to rocks and other coarse substrate materials, but is less likely to proliferate in fine gravel, sandy or mud substrates, although it can attach to plants.  Unlike other algae, Didymo has no characteristic odor. While it may look slimy, its silica cell walls make it feel gritty or fibrous when squeezed.   Examination of single cells with a 400x magnification compound microscope is required to confirm the identification of Didymo.  The shape of a Didymo cell resembles an old-fashioned coke bottle.  Cell length can range from 80-140 um, cell width from 25-42 um.


Why is Didymo of Concern to MD/DNR?
Didymo is probably not native to Maryland and has recently become a nuisance species in several places in North America, including the United States, and also in New Zealand where it is clearly invasive.  Didymo has all the characteristics of a successful invasive species, including a broad temperature tolerance range (32-80 F), an ability to colonize both slow/shallow and fast/deep waters, and it can bloom in low nutrient waters.  Observations on Didymo in Vancouver, British Columbia, Canada, suggest that it grows slower when nutrient levels increase.  Within the last 10 years, Didymo has expanded its range and reached nuisance densities for reasons not well understood.  To date, all invasive nuisance blooms have occurred in larger streams and rivers, often in the cold tail-waters of impoundments.  However, Didymo has also been found in lakes, ponds, and non-regulated rivers---although it will generally not achieve nuisance blooms in lentic waters.  When Didymo blooms proliferate, they can visibly cover 20 to 100% of the bottom and essentially most aquatic life. 

Like most microscopic organisms, complete eradication of a Didymo infestation in an open, free-flowing system is virtually impossible.  Researchers in New Zealand are testing various biocides for potential control of Didymo in their streams and rivers.  Chelated copper shows the most promise, but tolerance limits for fish to this biocide still need to be established.  For the present, the best management options are containment in already infested areas and then finding ways to mitigate any adverse ecological effects.  While the potential threats of Didymo blooms on the food web structure and hydraulics of lotic aquatic ecosystems are high, hard evidence on actual impacts is lacking.  Anecdotal reports suggest that Didymo infestations have negative effects on many species in benthic macroinvertebrate communities.  Controlled studies are needed to confirm these observations.  Although there is no direct evidence that a 2002 Didymo infestation in Rapid Creek, South Dakota, caused a decline in brown trout, angler reports say the fishery has not been the same since Didymo blooms were observed.  In New Zealand, where several rivers have been infested since 2001, some heavily, short-term impacts on invertebrates and fish have not been as severe as expected.  Longer-term effects are still unknown.  At the very least, large mats and long strands of Didymo covering most of the substrate can hamper angling and diminish the aesthetic quality of infested water bodies.

The pattern of Didymo infestations and spread is closely correlated with patterns of human water recreation activities, especially angling.  Since Didymo cells can remain viable in moist places for several days, they are easily and inadvertently transferred from place to place on footwear, fishing tackle, kayaks, canoes, boats, inner tubes, boat trailers, and other equipment to new waterways.  And, since Didymo reproduces mostly by asexual cell division, a single viable cell can infect a new area.

What’s the Status of Didymo in Maryland?
As of this writing, Didymo has been confirmed only in Gunpowder Falls between Prettyboy and Loch Raven reservoirs, Baltimore County.  An alert angler fishing just below Prettyboy Reservoir in January 2008 first person noticed something strange in the river and suspected it was Didymo.  MD/DNR staff collected samples in late April 2008 and confirmed Didymo presence.  MD/DNR will be conducting a complete assessment of the Gunpowder Falls to document the current distribution of Didymo, measure the extent of bottom coverage at various locations along the river, and track its spread.  Didymo has been confirmed in the Gunpowder between Falls Road, the first road crossing below Prettyboy Reservoir, and at least as far downstream as Glencoe Road.  On May 1, 2008, Ron Klauda (MD/DNR) estimated that 20-25% of the river bottom just upstream from the Falls Road bridge was covered by Didymo.  Charlie Gougeon and Susan Rivers (MD/DNR) have observed decreases in bottom coverage by Didymo in the Gunpowder at Falls Road after intense rain events and increases in river discharge. 

What is MD/DNR Doing in Response to the Didymo Infestation in the Gunpowder?
MD/DNR has responded aggressively to this threat.  A press release was issued on May 6, 2002 (attached) to alert the public to the confirmation of Didymo in the Gunpowder.  This press release urged anglers and other recreational users of the Gunpowder and surrounding waters to clean anything that comes into contact with the river water.  A CHECK, CLEAN, and DRY procedure is being promoted by MD/DNR.  Anglers and other water users are being asked to check their footwear and other gear for mud, plant material, and debris and then scrub and disinfect (clean) these items with a 5% salt solution (1 pound of salt in a 5 gallon bucket) for at least one full minute before and after they access the Gunpowder and other Maryland freshwater areas.  An alternative disinfection procedure that will kill Didymo cells and can be done at home is to scrub and soak footwear and gear in a hot solution of dish washing detergent, soak items for 30 minutes, and then let the clean equipment dry completely between uses (for at least 48 hours). 

Because porous and absorbent materials like the felt soles on boots are nearly impossible to completely disinfect, MD/DNR is urging anglers and others to abandon their felt-soled waders for rubber soles.  Neoprene stocking foot waders inside non-absorbent wading boots are acceptable replacements for felt-soled waders.  They can be effectively disinfected with solutions of household bleach, salt or dish washing detergent.  MD/DNR’s water monitoring crews will no longer be using felt-soled boots, and the agency recommends that all stream monitoring personnel (and anglers) in MD to adopt this same policy.  MD/DNR’s water monitoring crews are disinfecting footwear and sampling gear between sites.  The Maryland Biological Stream Survey crews are disinfecting between sites with a 10% household bleach solution (see attached protocol).

On May 22, 2008, MD/DNR staff built and set-up six “Wader Wash” stations along the Gunpowder downstream from Prettyboy Reservoir at angler access points at Falls, Masemore, Bunker Hill, York and Bluemount roads.  Each station
provides anglers with an opportunity to take 60 seconds to protect the river by disinfecting their footwear in a 5% salt solution each time they enter and leave the river.  MD/DNR Fisheries Service and State Park staff, along with interested angler clubs and others, will maintain and service these six “Wader Wash” stations. Anglers who fish in stretches of the Gunpowder without access to a “Wader Wash” station are being encouraged to make up their own 5% salt solutions and disinfect their footwear, or scrub them with hot water and dish detergent at home. 

MD/DNR will be setting-up seven additional “Wader Wash” stations at key access points on other high quality streams in the State, including the Casselman, Lower and Upper Savage, Youghiogheny, and North Branch Potomac rivers.  MD/DNR is also contacting angler associations in these areas and inviting them to help maintain these disinfection stations and also build/deploy additional stations at these and other streams.   

In June 2008, MD/DNR will be starting two Didymo monitoring projects in the Gunpowder and in other high quality streams.  The Gunpowder project will include monthly transect sampling at selected road crossings to document presence/absence of Didymo, bottom area coverage, and seasonal changes in distribution and abundance.  In a second project, MD/DNR will be exploring the ability of a new genetic marker method to rapidly and inexpensively detect the presence of Didymo cells in various streams around the State before colonies develop that are visible to the naked eye.  MD/DNR will be seeking participation from local government agencies and others in these monitoring projects.   MD/DNR is also asking all water monitoring groups to be on the look out for Didymo blooms in freshwater areas.  If anyone spots what they think is Didymo, they should contact Ron Klauda (410-260-8615, rklauda@dnr.state.md.us) or Don Cosden (410-260-8287,  dcosden@dnr.state.md.us).


Where Can I Get More Information About Didymo?
Visit MD/DNR’s website 

Other informative websites on Didymo include:
    http://www.fish.pa.us/water/habitat/ans/dudymo/faq_didymo.htm
    www.epa.gov/region8/water/monitoring/didymosphenia.html
    www.fedflyfishers.org/conDidymo.php
    http://www.biosecurity.govt.nz/
    http://www.des.state.nh.us/wmb/exoticspecies/didymo/index.html

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Disinfection Protocol for Footwear and Sampling Equipment  As a Precaution for Minimizing Ecological Risk

Problem:  An increasing potential exists for transferring non-native and invasive organisms (including those that cause serious diseases to native stream-dwelling fauna) from one water body to another in the course of government agency monitoring programs.  Whirling disease (a protist, Myxobolus cerebralis), didymo or rock snot (a benthic algae, Didymosphenia geminata), and amphibian chytrid fungus (Batrachochytrium dendrobatidis) are examples of such organisms.  In addition, avian influenza can be transferred among poultry farms simply by walking in litter that came from infected birds and then walking into another area where poultry are being raised.  It is important to properly clean and disinfect all footwear and sampling equipment that may have contacted disease-containing poultry litter or stream/pond water infected with whirling disease, didymo, amphibian fungus, or other water-borne diseases, parasites, or invasives.  These risks require that all MBSS field crews take precautions to minimize, to the greatest extent possible, the transfer of any disease/parasite/invasive organisms from one place to another. 

MBSS Response:  Since June 2007, MBSS field crews are required to disinfect all footwear and field equipment that come in contact with stream or wetland (e.g., vernal pool) water following sampling at each stream or pool site and before traveling to the next sampling site.  The disinfection protocols shall also be applied to all footwear and equipment that come in contact with poultry litter.

Disinfection Protocol:  The disinfection protocol consists of soaking or rinsing all footwear and equipment that has come in contact with stream/pool water or poultry litter in a 10% household bleach solution (2 quarts in a 5 gallon bucket) for at least one full minute.  Waders and equipment with smooth surfaces can be scrubbed with a brush soaked in the 10% bleach solution.  After soaking and scrubbing, waders and equipment should be rinsed with clean water to remove the bleach solution.  Avoid contact with the bleach solution as it can be irritating.  Thoroughly rinsing all footwear and sampling equipment with clean water will minimize the risk of skin and eye irritation.  DISINFECT AWAY FROM THE STREAM/POOL (AT LEAST 50 YARDS) IN AN AREA THAT WILL NOT BE CONTAMINATED WITH ANY SPILLED BLEACH SOLUTION.

Note: Beginning in 2008, only rubber-soled footwear will be worn by MBSS field crews.  Felt soles cannot by effectively disinfected and could therefore act as vectors for the dispersal of didymo and  other disease organisms and parasites.  
 

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