Presentation on the invasie Didymosphenia geminata.

1. The Missouri Department of Conservation and
Didymosphenia geminata
aka – Didymo or “rock snot”
Presenter: Mark Van Patten
Fisheries Management Biologist
Missouri Department of Conservation

2. Didymosphenia geminata
aka – Didymo or “rock snot”
• Didymo (rock snot) is an
invasive microscopic alga that
grows in long stalks which are
resistant to decay.
• It forms thick mats that have
negative impacts on streams
and can make fishing
impossible.
• Didymo is expanding its range
and tolerance throughout the
world.
• Currently, Didymo exists in 19
22 states and occurs as close
as northern Arkansas.

3. Didymo in Arkansas
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.

4. Didymosphenia geminata
• 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

5. Below are both a cell and stalk of Didymo found in the gut content of
Gammarus (Scud) which was living in the stalk portion of Didymo at
the time of collection. Also present are cells of epiphytic diatoms
that were attached to the Didymo stalks.
A Gammarus found in a
colony of living Didymo

6. 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)

7. Gomphonema 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.

9. Where is it currently found?

10. Conditions most favorable to Didymo colonization
• 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 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)

11. What are its negative effects?
• 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 (6 inches) 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)

12. More negative effects
• Another study on the negative effects of Didymo was
undertaken by Erica Shelby of the Arkansas Department
of 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.

13. Effect on trout
Trout have been
adversely affected
by the presence of
Didymo.
John Bell - Fisheries Biologist AG&F 2007
The relative weight of brown trout below
Bull Shoals dam in November 2006 was
the lowest that has ever been recorded. It is believed that blooms of didymo in
Relative weight for both brown and upper Bull Shoals tailwater have had the
rainbow trout have been falling in Bull predicted detrimental effect on trout forage
Shoals tailwater since 2004, which and trout foraging. Didymo carpets the
coincides with the appearance of the bottom of the river and makes it impossible
invasive algae, didymo. This decrease in for native macro invertebrates to colonize or
relative weight has been documented in survive. Further, trout cannot forage
other trout waters around the world efficiently in didymo and get no nutritional
where didymo has occurred. value from ingesting it.

14. What is being done to control Didymo
in the streams that are infected?
• 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).
• Addition of phosphorus (8)
• Copper: In New Zealand, a copper compound Gemex@ is
being used to control the growth of Didymo. Final field
trial results show the potential of reducing growth of
Didymo in applications in New Zealand (13). Some juvenile
trout mortality occurred. Further testing is needed.

15. What else is being done!!
• DNA testing (19)
• Scouring (5)
• Cleaning Equipment after fishing
• Public awareness: 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 the spread of Didymo from
one stream to another is felt sole waders.

16. In Missouri we need to:
• Survey likely locations of Didymo
• Spread the word of the potential impact of a
Didymo “bloom” on the fisheries
• Utilize posters and other forms of
information regarding the hazards of not
cleaning fishing equipment

17. Hand outs
Stickers
Buttons
Pocket Fliers

18. Help Stop Didymo
Check and Clean or Dry
• Check -Remove all
visible clumps of algae
and plant material from
fishing gear, waders,
water shoes and sandals,
canoes and kayaks and
anything else that has
been in the water.

19. Help Stop Didymo
Check and Clean or Dry
• Clean your gear in a 2
percent household bleach
solution (1/3 cup per gallon of
water), 5 percent saltwater
solution (1 cup per gallon of
water) or dishwashing
detergent. Scrub boats and
other “hard” items thoroughly.
• Completely soak equipment,
personal flotation devices and
other “soft” material for at least
20 minutes.
• Use the Boot wash stations in
the four state trout parks

20. Help Stop Didymo
Check and Clean or Dry
• Dry -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
• Please remember to Check
at least 48 hours. and Clean or Dry your
• Do your part–don’t fishing gear and waders
spread Didymo. when moving between
waters.

21. 3 CSR 10-6.415 Restricted Zones
PURPOSE: This amendment prohibits the use of porous-soled waders or
footwear incorporating or having attached a sole of felted, matted or woven
fibrous material when fishing in the following managed trout waters.
(A) Barren Fork Creek - Shannon (L) North Fork of White River - Ozark
County County
(B) Blue Springs Creek - Crawford (M) Roubidoux Creek - Pulaski County
County (N) Spring Creek - Phelps County
(C) Crane Creek - Stone and Lawrence
(O) Capps Creek - Barry and Newton
counties
counties
(D) Current River - Dent, Texas and
Shannon counties (P) Niangua River - Dallas and Laclede
(E) Dry Fork Creek - Crawford and counties
Phelps counties (Q) Roaring River - Barry County
(F) Eleven Point River - Oregon County (R) Maramec Spring Park - Phelps County
(G) Hickory Creek - Newton County (S) Montauk State Park - Dent County
(H) Lake Taneycomo - Taney County (T) Roaring River State Park - Barry
Little Piney Creek - Phelps County County
(J) Meramec River - Crawford and (U) Bennett Spring State Park - Dallas and
Phelps counties Laclede counties
(K) Mill Creek - Phelps County
(V) Stone Mill Spring Branch - Pulaski
County

22. QR Code

23. Questions?
Didymo it’s Snot a Joke!

24. References
1. Whitton B, Ellwood N, Kawecka B. Biology of the freshwater diatom Didymosphenia: a
review. Hydrobiologia [serial online]. September 2009;630(1)
2. http://epa.gov/Region8/water/didymosphenia/White%20Paper%20Jan%202007.pdf
Spaulding, S and L. Elwell (2007)
3. 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.
4. 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)
5. 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)
6. http://ecosystem-preservation.suite101.com/article.cfm/didymo_freshwater_diatom
7. http://wildlife.utah.gov/pdf/AIS_plans_2010/AIS_12bDidymo-Dan-final.pdf
8. http://www.ncd-afs.org/Pages/59/RSTC%20State%20Rpt%202007.pdf
9. http://www.niwa.co.nz/news-and-publications/publications/all/abb/2006-19/copper
10. 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.
11. 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.

25. References (continued)
12. www.amaab.org/images/1510_Lester_Effects_of_the_Nuisance_Diatom_Didymosphenia_Gemi ata.pdf
13. www.niwa.co.nz/news-and-publications/publications/all/abb/2007-25/didymo
14. www.hoaff.org/newsletters/NL2007-04.htm
15. www.asee-nc.org/Conferences/Spring08Meeting/Srping08Proceedings/pdf/set2/71.pdf
16. www.flyfishnewengland.com/didymos-study.htm
17.www.mucinex.com/
18. www.articles.baltimoresun.com/2009-12-17/sports/0912170014_1_didymo-trout-waters-fishing-gear
19. www.waikato.ac.nz/news/archive.shtml?article=627
21. www.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.pdf
25. http://www.unclejacks.co.nz/4.htm
26. Shelby, E. L. 2006. An Assessment and Analysis of BenthicMacroinvertebrate Commumities
Assocoated with the Appearance of Didymosphenia geminata in the Whitw River Below Bull
Shoals Dam. ADEQ Final Draft. 42 pages.