ROCK SNOT
Russ Rhodes
Department of Biology
Missouri State University
Springfield, Missouri
I would like to acknowledge Mr.
Robert Britzke from Eureka Springs,
Arkansas for pointing out the
presence of Didymosphenia geminata
in the tail race area of Beaver.
Numerous collections were made
from a variety of sites in March 2003
followed by March- May 2006. Many
of the images in this talk were made
at those sites and from the collected
material.



Animal?
Plant?
Mineral?
The brown color is due to fucoxanthin, a
pigment contained in each cell, (although
each cell also contains chlorophyll) and the
white or translucent color is due to the stalks.






What is Didymo?
Where is it currently found?
What are its positive effects?
What are its negative effects?
What can be done to control Didymo?
Open discussion


Didymo is a colonial diatom.
Major characters are
◦ Silicon wall with precise ornamentation
◦ Oil and carbohydrate for storage product



Each cell exudes extracellular polymeric substance,
EPS,the material of stalks and resistant to degradation.
There are phosphatases at the base of each cell where new
stalk material is extruded. Phosphatases remove PO4 from
organic phosphate molecules.
When cells divide, the stalks are formed anew but
connected to the old stalk. Thus the stalk material
continues to build up.






Colonial diatom
Cells divide
Attachment as gelatinous
stalks
Massive plant
Cells (200-300 microns)
A cell cleaned in sulphuric
acid and showing the
ornamentaion critical for
identification
Below are both a cell and stalk of Didymo found in the gut
content of Gammarus which was living in the stalk portion of
Didymo at the time of collection.
Didymo is not known to produce any toxins and the oxygen
content within the stalk matrix has been found to be
supersaturated.
A Gammarus found in a
colony of Didymo
Microscopic colony of Didymo scraped from a rock in the
Beaver tailrace, March 2006
The ability of Didymo to remain attached to the substrate by the basal
portion of the stalks probably contributes to its continued presence and
redevelopment after a flood type event and/or seasonal changes. (1)
Gomphonenma with stalks and division
similar to Didymo. The major difference is
that the stalk material of Gomphonema is
slippery and that of Didymo is cottony.
World wide, from Canada to
China to New Zealand to
England. In many states from
Maine to the TVA region to New
Mexico to Arkansas to the NW
New location in Maryland (18):
“Someone who fishes the Gunpowder is
likely to fish the Savage or Big Hunting
Creek," Cosden said. "That's been the
pattern. The better trout streams is where
it's showing up."
A site downstream from the tailrace
region of Beaver as well as other
locations in the tailrace region. Russ
Rhodes and Bob Britzke are
collecting at this site, March 2006.






High N/P ratio, low phosphorus (< 2 ug/L) in the
water.
Bright sunlight
Low TSS (total suspended solids)
pH (7-9)
Generally cold waters, but found in waters from 4
to 27 C (2)
Stable water flow: “mean flow regime is associated
with bloom development, based on a significant
negative relationship detected between D.
geminata biomass and mean discharge” (3)

High biomasses found in the tailrace areas and streams below
impoundments
◦ “Important predictor variables of D. geminata abundance included dam
presence, water clarity and total phosphorus concentration. When data from dam
sites were analyzed, a multiple regression model using mean discharge and pH
as independent predictors explained 73% of the variation in D. geminata cell
density. Analysis of 3 years of data from one study river (Red Deer River)
revealed consistently higher D. geminata cell densities at the dam site compared
to the upstream reference.” (4)


Even after flooding the tailrace area within a week biomass of Didymo
returned to pre-flood amounts (5)
Presence in an Alaskan lake (Lake Naknek) from sediment record
(1218-2003) (11) indicating that this organism is not new to North
America

The stalks provide additional
substrate for epiphytic diatoms
such as Eunotia seen here.

The cells are a source of food for
invertebrates such as scud, as seen
in a previous slide.

During the day the cells provide an
additional source of oxygen to the
water through photosynthesis.







The damage caused by Didymo is largely from the stalks produced by each cell
of the diatom colony which form large mats on streambeds, decreasing clarity
and oxygen availability (especially at night). In some areas mats 20cm thick
have been reported. (6)
When Didymo is absent or in low numbers, diversity of invertebrates is
increased .(6)
Significant changes in the kinds of invertebrates were found in an excellent
study by EcoAnalysts Inc. (12) in examining the effects of Didymo in the
Kootenai River, Montana/Idaho
◦ EPT’s declined (Ephemeroptera (mayflies), Plecoptera (stoneflies), and
Trichoptera (caddisflies)),
◦ “mats were a haven for midges and worms” (12)
Another study on the negative effects of Didymo was undertaken by Erica
Shelby of the Akansas Departent od Environmental Quality (26). She found
decreases in the biodiversity of invertebrates associated with populations of
Didymo.
“In New Zealand D. geminata has been correlated to increases of invertebrates
that are indicators of poor stream health”. (7)
Canals used for irrigation and aquifers in California are scraped of Didymo.
It also clogs grates in the water supply canal. (2)
The stalks create a very unsightly looking benthos on the stream and on the
shore where they dry resembling toilet paper.





Models: One approach is to develop models that may predict the distribution
of Didymo based on a sorting of habitats by air temperature, base water flow,
precipitation seasonality, and other parameters. The former two seem to be
able to account for much of the variance (10)
Phosphorus: “In an attempt to “manage around” an infestation of
Didymosphenia geminata South Dakota GFP is starting a nutrient-enrichment
project this spring that involves artificially increasing total phosphorus in a 3kilometer section of Rapid Creek immediately below Pactola Dam. The goals
of this project are to stimulate productivity, both primary and aquatic insect,
and to ultimately increase brown trout growth and survival.” (8) Didymo may
be able tolerate low or limiting P since it can produce phosphatases as
mentioned earlier.
Another study on phosphorus uptake in a low concentration by Didymo
implicates the enhancement of P uptake by the presence of iron (15)
Copper: In New Zealand, a copper compound Gemex@ is being used to
control the growth of Didymo. Final field trial results show positive effects of
reducing growth of Didymo in applications in New Zealand. (13)
Mucinex: Another new approach has been tried in 2009. It involves the
application of mucinex, an off the counter mucous loosener. (15) (16)





DNA testing: One of the latest techniques to assess the presence, low density, and then
aggressive public awareness (to follow) and other techniques is a DNA screen (19)
Regulating stream flow: “The findings suggest that controlled flow releases from reservoirs
during the summer could be used to limit the impact of this nuisance species in streams in the
Colorado Front Range. Flows below Barker Reservoir near Nederland that are above 200
cubic feet per second — similar to those experienced last year once the reservoir started to
spill in late June — appear to be sufficient to control the didymo…” (20)
Scouring: “Our results suggest that bed movement may be a dominant scouring mechanism
that acts to control the growth and distribution of D. geminata. (5)
Cleaning after fishing: There have been a number of resources published that focus on clean
up.
◦ One of the most thorough is: http://www.westdenvertu.org/snails.htm#cleaning (21)
◦ A well recommended chemical cleanup is best described as follows: “I recommend Uncle
Jacks Didymo Cleaner to ensure a 100% clean kill of all didymo cells.” (22) It is a
formulation of benzalkonium chloride (24)
◦ Uncle Jacks Didymo Cleaner: This is the reference to the cleaner and source of purchase
(23). It was tested by NIWA (National Institute of Water and Atmospheric Research, New
Zealand.
Public awareness: While not an algicide, nutrient enhancement, nor flow control, many states
have developed awareness programs through website, posters, and talks such as this to create
a public awareness tuned to the prevention of spreading Didymo from one habitat to another.
One of the main “culprits” in this spread is the felt sole of waders. Examples of posters are
as follows:
http://www.anr.state.vt.us/dec//waterq/lakes/docs/
ans/lp_dididguide.pdf
http://www.fish.state.pa.us/water/habitat/ans
/didymo/faq_didymo.htm
Disinfect your boat, trailer, boots & other
gear before
entering a new body of water
Remember -- you can’t see individual
didymo cells so thoroughly disinfect all of your
equipment
Photo - Tim Daley, PA DEP
CHECK -- Before you leave a river, stream, or
lake, check items and leave debris at site. If you
find any later, treat and put in trash. Do not wash
down drains.
CLEAN -- There are several ways to kill didymo.
Choose the most practical treatment for your
situation which will not adversely affect your gear.
http://www.wildlife.state.nh.us/Fishi
ng/Fishing_PDFs/DidymoPoster_07
.pdf
Missouri Department of
Conservation
Stop Rock Snot
The invasive alga “didymo” has been found in Arkansas in portions of
the White River System and the North Fork of the White River.
Before entering this water:
CHECK AND CLEAN
OR
DRY
Remove all visible clumps of algae and
plant material from fishing gear, waders,
equipment, water shoes and sandals,
canoes and kayaks, and anything else
that has been in the water.
Clean your gear in a 2% household
bleach solution (1/3 cup per gallon
water), 5% saltwater solution (1 cup per
gallon water) or dishwashing detergent.
Scrub boats and other “hard” items
thoroughly; Completely soak
equipment, felt-sole waders, personal
flotation devices and other “soft” items
for at least 20 minutes!!!!
OR
Allow any item that has been in contact
with the water to completely dry; the
item should be exposed to sunlight and
left to dry for at least 48 hours.
Please Do Your Part - Don’t Spread Didymo!
For More Information
Contact:
(417) 334-4859
Clean your gear in a 2% bleach solution
or 5% saltwater solution or dishwashing
detergent containing benzalkonium
chloride: Scrub boats and other “hard”
items thoroughly; Completely soak


Images
http://images.google.com/images?hl=en&source=hp&q=didymo&um=1&i
e=UTF8&ei=AbhHS4KtOoi4M5fU2I8J&sa=X&oi=image_result_group&ct=title
&resnum=4&ved=0CCcQsAQwAw
Videos
◦ http://www.biosecurity.govt.nz/video/didymoeffects-waterways Rather dramatic
◦ http://www.invasivespeciesinfo.gov/aquatics/didymo.shtml
◦ http://www.dgif.virginia.gov/fishing/didymo.asp great for stream
coverage measurements
◦ http://www.wchstv.com/newsroom/wvwildlife/2009/ww090520.shtml


In a study of trout in Rapid
Creek, South Dakota, the brown
trout were stuck with 1 yr or less
age fish, with no second year and
“very few adults since Didymo
was first reported in 2002. This
stream was one of the top two
brown trout fisheries in the state
in 1990s….This impact appears to
be due to Didymo altering the
aquatic insect community and
thus impacting the food source
for the trout.” (8)
The relative weight of brown
trout below Bull Shoals dam in
November 2006 was the lowest
that has ever been recorded.
Relative weight for both brown
and rainbow trout have been
falling in Bull Shoals tailwater
since 2004, which coincides with
the appearance of Didymo. This
decrease in relative weight has
been documented in other trout
waters around the world where
Didymo has occurred”. (14)
We need to be:
1. Surveying likely locations of Didymo
2. Utilizing posters and other
information regarding the hazards of
not cleaning fishing equipment
3. Spreading the word of the potential
impact of a Didymo “bloom” on the
fisheries
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Whitton B, Ellwood N, Kawecka B. Biology of the freshwater diatom Didymosphenia: a
review. Hydrobiologia [serial online]. September 2009;630(1)
http://epa.gov/Region8/water/didymosphenia/White%20Paper%20Jan%202007.pdf
Spaulding, S and L. Elwell (2007)
Kirkwood, A. E., S. Troina, L. J. Jackson, and E. McCcauley. 2007. Didymosphenia geminata
in two Alberta headwater rivers: an emerging invasive species that challenges conventional
views on algal bloom development. Canadian J. Fisheries and Aquatic Sciences 64:1703-1709.
Floeder S, Kilroy C. Didymosphenia geminata (Protista, Bacillariophyceae) invasion, resistance
of native periphyton communities, and implications for dispersal and management.
Biodiversity and Conservation [serial online]. December 2009;18(14)
Miller M, McKnight D, Cullis J, Greene A, Vietti K, Liptzin D. Factors controlling streambed
coverage of Didymosphenia geminata in two regulated streams in the Colorado Front Range.
Hydrobiologia [serial online]. September 2009;630(1)
http://ecosystem-preservation.suite101.com/article.cfm/didymo_freshwater_diatom
http://wildlife.utah.gov/pdf/AIS_plans_2010/AIS_12bDidymo-Dan-final.pdf
http://www.ncd-afs.org/Pages/59/RSTC%20State%20Rpt%202007.pdf
http://www.niwa.co.nz/news-and-publications/publications/all/abb/2006-19/copper
Sunil Kumar, Sarah A Spaulding, Thomas J Stohlgren, Karl A Hermann, Travis S Schmidt,
Loren L Bahls (2009) Potential habitat distribution for the freshwater diatom Didymosphenia
geminata in the continental US. Frontiers in Ecology and the Environment: Vol. 7, No. 8, pp.
415-420.
Pitte, D. P, K. A. Lane, A. K. Hermann, S. A. Spaulding, B. P. Finney. 2009. Historical
abundance and morphology of Didymosphenia species in Naknek Lake, Alaska. Acta Bot Croat
68:183-197.
References (continued)
12. http://www.amaab.org/images/1510_Lester_Effects_of_the_Nuisance_Diatom_
13.http://www.niwa.co.nz/news-and-publications/publications/all/abb/2007-25/didymo
14. http://www.hoaff.org/newsletters/NL2007-04.htm
15. http://www.asee-nc.org/Conferences/Spring08Meeting/Srping08Proceedings/pdf/set2/71.pdf
16. http://www.flyfishnewengland.com/didymos-study.htm
17. http://www.mucinex.com/
18. http://articles.baltimoresun.com/2009-12-17/sports/0912170014_1_didymo-trout-waters-fishinggear
19. http://www.waikato.ac.nz/news/archive.shtml?article=627
20. http://coyotegulch.wordpress.com/2009/05/11/large-instream-flows-help-control-didymo
21. http://www.westdenvertu.org/snails.htm#cleaning
22. http://www.chrisdore.com/whattobring.htm
23. http://www.unclejacks.co.nz/1.htm
24. http://www.fs.fed.us/r4/resources/aquatic/literature/matthews_quat_disinfectants_
didymo.df
25. http://www.unclejacks.co.nz/4.htm
26. Shelby, E. L. 2006. An Assessment and Analysis of BenthicMacroinvertebrate
Commumities Associated with the Appearance of Didymosphenia geminata in the Whitw
River Below Bull Shoals Dam. ADEQ Final Draft. 42 pages.

Several of the photos were courtesy of Scott Branyan and Bob Britzke