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Codium fragile ssp. tomentosoides
(Dead Man`s Fingers)




Welcome to the Codium fragile ssp. tomentosoides information page. Just click on the topic of interest from the contents menu or scroll down to find out about Codium in Nova Scotia.

Contents:

1. Codium fragile ssp. tomentosoides: What is it?
2. How to Identify Codium
3. Quick Reference ID Key
4. History and Vectors of Spread: The World and Nova Scotia
5. Present Known Distribution in Nova Scotia
- Map of Distribution
6. Ecological Implications for the Coast of Nova Scotia
7. Ecology of Codium
8. Reproduction by Codium
9. References and Further Reading
10. Photo Gallery
11. Acknowledgements



1. Codium fragile ssp. toementosoides: What is it?


Codium fragile ssp. tomentosoides (known locally as "Dead Man`s Fingers" and "Green Sponge") is a green alga (seaweed), believed to have originated in Japan. This seaweed is one of the most invasive in the world (Trowbridge 1998).


2. How to Identify Codium


Codium is easily recognizable in shallow coastal waters (the subtidal zone), and washed up on beaches in Nova Scotia, because there are no other seaweeds in the area with the same characteristics. An adult plant is pale to dark green in colour and has a very bush-like appearance, with many branches arising from a disk shaped pad,known as a holdfast. The holdfast is responsible for keeping the plant securely fastened to rocks on the seabed. The branches themselves are cylindrical in shape, resembling fingers. When submerged, Codium branches feel soft and "fuzzy" to the touch due to the presence of numerous long hairs on the surface of each frond. However when washed up on beaches and during the winter (when the hairs are lost) the branches become coarse. Juvenile, undeveloped (or undifferentiated) stages of Codium will appear as fuzzy, moss-like mats on hard surfaces.

Adult plants can grow up to 90 cm in height and when fully established in the subtidal, can form as bushy meadows. When detached from its subtidal substrate by waves, Codium can wash up on beaches as a whole plant (complete with holdfast) or in small pieces (a result of fragmentation or budding, see Reproduction). The plants will often be mixed with other types of marine plants torn from the seabed such as kelp (Laminaria sp.) and rockweeds (Ascophyllum , Fucus sp.)

Close Up of Codium
Codium meadow

3. Quick Reference ID Key (or 4 characteristics to look for when hunting for your first Codium plant):


- Dark green color
- Cylindrical, finger-like branches
- A soft, fuzzy surface
- Bush-like structure

4. History and Vectors of Spread: the World and Nova Scotia


Codium is believed to be native to Japan (Silva 1955). It was first reported in Holland in 1900 and has since spread throughout Europe. It can now be found along the shores of Britain, Australia, New Zealand, the Mediterranean and North America (Campbell 1999, Carlton and Scanlon 1985, Trowbridge 1995, Trowbridge 1998). Codium was first reported on the North American east coast in 1957 at Long Island, New York (Bouck and Morgan 1957), and can now be found from South Carolina to Nova Scotia. Graves Shoal, Mahone Bay, Lunenburg County was the first reported location of Codium in Nova Scotia (Bird et al 1993). Since 1991 Codium has spread throughout Mahone Bay into adjacent St. Margaret`s Bay and beyond (see Map of Distribution).

Although the exact modes of transport (vectors) for the dispersal of Codium to North America (and subsequently to Nova Scotia) are not known, the most likely means of transoceanic dispersal are by attachment on ships hulls or on the shells of oysters shipped from Europe (Carlton and Scanlon 1985). Coastal spread of the alga is attributed to four human dispersal mechanisms and three natural dispersal mechanisms (Carlton and Scanlon 1985).

Human Dispersal Mecanisms:

1) Attachment to ship hulls
2) Attachment to oyster shells
3) As fouling organisms in drag nets
4) As packing material for fishery products

Natural Dispersal Mechanisms:

1) Swimming cells (see Reproduction )
2) Vegetative propagation (see Reproduction)
3) Whole plant drift via ocean currents

It is likely that a combination of these mechanisms are responsible for the introduction of Codium into Nova Scotia.


5. Present Known Distribution in Nova Scotia


Codium is found primarily in the subtidal zone in Nova Scotian waters. Its present, known distribution along the South shore has been established by SCUBA surveys carried out by Dr. Robert Scheibling and co-workers at Dalhousie University in 2000. It extends from Green Bay to Pennant Bay along the southeastern shore of Nova Scotia. It has also been reported at Cariboo Harbour in the Gulf of St. Lawrence (Garbary et al 1997). Below is a map of the currently known distribution of Codium in Nova Scotia.



Map of Distribution for Codium fragile ssp. tomentosoides in Nova Scotia.

6. Ecological Implications for the Coast of Nova Scotia


The shallow rocky seabed along Nova Scotia`s coast cycles between two types of communities. One dominated by underwater forests of the large kelps and the other, referred to as "barrens", by small algae that form crusts and thin mats over bare rock (Scheibling et al 1999). This cycling is controlled by the number and concentration of sea urchins. As sea urchins increase in number along the edges of a kelp bed they begin to graze on the kelp (their primary food source) so intensely that they destroy the whole forest, leaving barrens in their wake. A return to a kelp-dominated community is set in motion by a decrease in sea urchin density, usually caused by the outbreak of a disease among the urchins (Scheibling et al 1999).

The invasion of Codium into barrens after an urchin die-off is disrupting this cycle. In addition, the die-back of kelp forests resulting from outbreaks of Membranipora membranacea enables Codium to establish itself in an area with minimal competition from kelps. Where kelp is plentiful, Codium is unable to establish itself in abundance. Once Codium is firmly established in an area, kelp is unable to re-colonize, thus altering the structure of the subtidal community.

Field observations have shown that areas covered by Codium have reduced abundance of some species compared to similair areas covered by kelp (Scheibling unpub data). The morphological structure of Codium will likely increase sedimentation. Codium is a "low lying" alga, making it difficult for some large invertebrates and fish to move among the plants and live in the space between the bushy parts of the algae and the seabed (the understory). In a kelp bed, many species can freely move under the canopy of fronds because the stems (stipes) are narrow and widely spaced. They rely on this understory environment for food, habitat and protection from predators. Replacement of kelp by Codium will undoubtedly affect such species.

Changes in the ecology of the subtidal community will likely have an impact on some of the commercially important species of Nova Scotia. Kelp is the primary food source of sea urchins, which are harvested for their roe. While it has been shown that sea urchins will consume Codium when they come into contact with it (Prince and LeBlanc 1992), sea urchins fed Codium do not produce high quality roe (Scheibling and Anthony 2001). Furthermore, it is possible that the low lying structure of Codium meadows will inhibit the movements of seabed foraging species such as lobster. Codium also causes problems for the shellfish and aquaculture industries. The alga can foul beaches and will attach itself to just about any solid surface, causing extra cleaning work for aquaculturalists and reducing the growth of cultured species. In its quest for a stable substrate Codium will often make its home on the shells of oysters, scallops, and clams. This can cause problems because an attached adult plant can hinder the movement and feeding of the shellfish. In cases where the attached plant is relatively large and wave exposure is high, the shellfish can be swept away with the plant (thus another common name for this invader is Oyster Thief").

7. Ecology of Codium


Within its current known distribution in Nova Scotia, Codium is primarily a subtidal species, ranging from the intertidal zone being found to depths of approximately 15 m (data from 2000 SCUBA surveys carried out by Dr. Robert Scheibling and co-workers at Dalhousie University ). In order to establish itself in an area, the swimming cell (a female gamete) (see Reproduction) needs a stable surface substrate to attach itself to. The rocky shores of Nova Scotia provide excellent areas for attachment of Codium; on sandy or muddy bottoms the alga will make use of secondary hard substratum, such as mussels. Codium will settle on just about any kind of hard surface including ships hulls (see Vectors), navigation markers and shellfish (see Impacts). Codium can survive in a broad range of temperatures and salinities, as is evident from its wide-ranging distribution (particularly along the North American coast). Although the alga commonly inhabits sheltered bays throughout most of its range, in Nova Scotia it can be found in coastal areas more exposed to waves and swell.

8. Reproduction in Codium


Within its current known distribution in Nova Scotia, Codium is primarily a subtidal species, ranging from the intertidal zone, to depths of approximately 15 m (data from 2000 SCUBA surveys carried out by Dr. Robert Scheibling and co-workers at Dalhousie University ). In order to establish itself in an area, the swimming cell (a female gamete) needs a stable surface substrate to attach itself to. The rocky shores of Nova Scotia provide excellent areas for attachment of Codium; on sandy or muddy bottoms the alga will make use of secondary hard substratum, such as mussels. Codium will settle on just about any kind of hard surface including ships hulls (see Vectors), navigation markers and shellfish (see Impacts). Codium can survive in a broad range of temperatures and salinities, as is evident from its wide-ranging distribution (particularly along the North American coast). Although the alga commonly inhabits sheltered bays throughout most of its range, in Nova Scotia it can be found in coastal areas more exposed to waves and swell.

9. References and Further Reading


References:

Bird C.J., Dadswell M.J., and Grund D.W. 1993 First record of the potential nuisance alga Codium fragile ssp. tomentosoides (chlorophyta, caulerpales) in Atlantic Canada. Proceedings of the. Nova Scotia Institute of Science. 40: 11-17.

Bouck G.B. and Morgan E. 1957 The occurrence of Codium in Long Island waters. Bulletin of the Torrey Botanical Club. 84: 384-387.

Campbell S.J. 1999 Occurrence of Codium fragile ssp. tomentosoides (chlorphyta: bryopsidales) in marine embayments of Southeastern Australia. Journal of Phycology. 35: 938-940.

Carlton J. and Scanlon J. 1985 Progression and dispersal of an introduced alga: Codium fragile spp. tomentosoides (Chlorophyta) on the Atlantic Coast of North America. Botanica Marina 28: 155-165.

Garbary D.J., Vandermeulen H., and Kim K.Y. 1997 Codium fragile ssp. tomentosoides (chlorophyta) invades the Gulf of St. Lawrence, Atlantic Canada. Botanica Marina. 40:(6) 537-540.

Prince J.S. and LeBlanc W.G. 1992 . Comparitive feeding preference of Strongylocentrotus droebachiensis (echinoidea) for the invasive seaweed Codium fragile ssp. tomentosoides (chlorphyceae) and four other seaweeds. Marine Biology. 113: 159-163.

Scheibling R.E., Hennigar A.W., and Balch T. 1999 Destructive grazing, epiphytism, and disease: the dynamics of sea urchin-kelp interactions in Nova Scotia. Canadian Journal of Fisheries and Aquatic Science. 56:(12) 2300-2314.

Scheibling R.E., Anthony S.X. 2001 Feeding, growth and reproduction of sea urchins (Strongylocentrotus droebachiensis) on single and mixed diets of kelp (Laminaria spp.) and the invasive alga Codium fragile ssp. tomentosoides. Marine Biology. 139: 139-146.

Silva P.C. 1955 The dichotomous species of Codium in Britian. Jornal of the Marine Biology Association. UK. 34: 565-577.

Trowbridge C.D. 1995 Establishment of the green alga Codium fragile ssp. tomentosoides on New Zealand rocky shores: current distribution and invertebrate grazers. Journal of Ecology. 83: 949-965.

Trowbridge C.D.1998 Ecology of the green macroalga Codium fragile (suringar) hariot 1889: invasive and non-invasive subspecies. Oceanography and Marine Biology: An Annual Review. 36: 1-64. A.D. Ansell, R.N. Gibson and Margaret Barnes, Eds. UCL Press.


Further Reading:

10. Photo Gallery


Coming Soon !!

11. Acknowledgements


All photos on this website were provided by and the property of Dr. R.E. Scheibling.




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All Content and Images Copyright Benthic Ecology Lab 2001