Species Profile

Eastern Waterfan

Scientific Name: Peltigera hydrothyria
Taxonomy Group: Lichens
Range: Quebec, New Brunswick, Nova Scotia
Last COSEWIC Assessment: November 2013
Last COSEWIC Designation: Threatened
SARA Status: No schedule, No Status

Individuals of this species may be protected under Schedule 1 under another name; for more information see Schedule 1, the A-Z Species List, or if applicable, the Related Species table below.

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Quick Links: | Description | Habitat | Biology | Threats | Protection | National Recovery Program | Documents

Image of Eastern Waterfan


The Eastern Waterfan, Peltigera hydrothyria, is a leafy lichen having veins on the under surface that are distributed in a fan-shaped manner. The lichen is fixed to rocks by spongy tufts of fibres. The red-brown fruit bodies are borne on the margin of the lichen. The sacs within the fruit bodies shoot out elliptical spores. There are no specialized vegetative propagules. The photosynthetic partner in this lichen is a cyanobacterium. This species is one of only a few leafy lichens that can grow at and below water level. (Updated 2017/07/27)


Distribution and Population

The Eastern Waterfan is endemic to eastern North America. In the USA, this lichen occurs at approximately 30 sites scattered throughout Connecticut, Georgia, Maine, Massachusetts, New Hampshire, North Carolina, Pennsylvania, Rhode Island, Tennessee, Vermont and Virginia. In Canada, the Eastern Waterfan is currently known only from three provinces: Québec, New Brunswick and Nova Scotia. There are thirteen sites comprising ten occurrences and seven locations. A site is where the lichen is actually found, and sites less than 1km apart comprise a single occurrence. A location is a geographically or ecologically distinct area in which a single threatening event can rapidly affect all the individuals present at an occurrence. There is one occurrence of the Eastern Waterfan in Québec, three in New Brunswick and six in Nova Scotia. The Canadian population of the Eastern Waterfan represents approximately one-quarter of the known world total. There are no historical occurrences from Ontario, Prince Edward Island or Newfoundland and Labrador. (Updated 2017/07/27)



In eastern North America, the Eastern Waterfan grows attached to rocks at or below water level in clear, cool, partially shaded streams. Small waterfalls, exposed boulders and sinuous stream configurations create quiet or protected backwaters where the lichen grows outside the main current. In summer, this lichen is often partially or completely exposed during low water flow periods. The elevation of streams in which the Eastern Waterfan is found varies from 10m to 720m a.s.l. Stream quality, including a suitable pH, water temperature, and absence of silt, appears to be very important. Partial shade may be needed to help keep humidity high and temperatures low during summer months. Stream water temperature appears to be very important. Studies on the related Western Waterfan show that if the temperature reaches 18oC, photosynthetic rates decline and thallus weight loss occurs after only 30 days. Nitrate levels at or above 5mM lead to a similar decline. (Updated 2017/07/27)



The Eastern Waterfan produces no specialized vegetative propagules but it is likely that small pieces of lichen break off and become attached downstream to provide a means for dispersal. The only other way the lichen can reproduce is via the discharge of fungal spores from the apothecia but success depends upon the presence of a suitable cyanobacterium for resynthesis of the lichen. The fruit bodies of the lichen eject their spores into the air. Upon landing on a rock surface in or on the banks of a stream, these germinate and grow towards nearby cyanobacteria. If the latter are compatible, they become enveloped by the fungal strands and eventually grow into a visible lichen. The generation time for lichens varies from ten years in rapidly colonizing lichens to more than 17 years for old-growth forest species. The Eastern Waterfan is a member of a group of lichens known as cyanolichens in which cyanobacteria provide carbohydrates through photosynthesis to the fungal partner as well as nitrogen since they are able to fix atmospheric nitrogen. The cyanobacterium in the Eastern Waterfan is reported to be Capsosira lowei. (Updated 2017/07/27)



Activities that alter the watercourses, water quality and protective vegetation surrounding habitats all have the potential to affect Eastern Waterfan locations. Cool water appears to be crucial to the Eastern Waterfan’s ability to thrive. Removal of trees growing near stream banks exposes the Eastern Waterfan to increased sun, raised air temperatures, reduced humidity and increased erosion and runoff. Increased wind and light exposure in harvested areas can reduce water levels on and around rocks where the Eastern Waterfan occurs so that during months with low water levels, the lichen may be exposed and become dry beyond its tolerance limits. Forestry activities in Colchester County, Nova Scotia, may currently affect five of the seven locations of this lichen and over 30% of the total enumerated mature individuals in Canada. The need to supply 500,000 tons of wood annually for the new 60-megawatt biomass electricity co-generating station in Nova Scotia will mean greater forestry activity and habitat disturbance. Currently, forest harvesters in Nova Scotia are only required to leave a 20m buffer on each side of streams; it is 30m in New Brunswick. The further expansion of wind farms in Nova Scotia, forestry activity, or mineral exploration also requires access roads through undisturbed woodlands. These may encroach on existing Eastern Waterfan habitats and be a source of siltation, which has the potential to affect several of the Eastern Waterfan sites. The extraction of natural gas through hydrofracturing is also known to alter groundwater patterns and water quality. Two areas in Nova Scotia where the Eastern Waterfan occurs are being considered for this activity. The Eastern Waterfan grows only in semi-shaded streams with little to no siltation. Repeated siltation events caused by runoff from roadbeds or motorized vehicle tracks can coat the lobe surfaces of the lichen, affect photosynthesis and cover potential sites for establishment on rock surfaces. Air pollution can affect lichens. Acid rain, currently less serious in the Maritimes than in former decades, may eventually result in the buffering capacity of the watersheds or substrata being exceeded. This may lead to the water becoming more acidic and this could prevent cyanolichens like the Eastern Waterfan from thriving. Climate change in the medium term is a serious threat to most of the Eastern Waterfan locations. Recent models suggest that the amount of summer precipitation in Nova Scotia is not expected to change much, but there will be more droughts due to increased evaporation as a result of higher summer temperatures. Droughts reduce water flow and stream depth, which can lead to desiccation and death of the Eastern Waterfan. In winter the climate models suggest there will be more precipitation of which a higher proportion will fall as rain. The increased water flow is likely to enhance scouring and remove the Eastern Waterfan from rocks on the margins and bottoms of streams. (Updated 2017/07/27)



Federal Protection

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.



PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

5 record(s) found.

COSEWIC Status Reports

  • COSEWIC Assessment and Status Report on the Eastern Waterfan Peltigera hydrothyria in Canada (2014)

    The Eastern Waterfan, Peltigera hydrothyria, is a leafy lichen having veins on the under surface that are distributed in a fan-shaped manner. The lichen is fixed to rocks by spongy tufts of fibres. The red-brown fruit bodies are borne on the margin of the lichen. The sacs within the fruit bodies shoot out elliptical spores. There are no specialized vegetative propagules. The photosynthetic partner in this lichen is a cyanobacterium. This species is one of only a few leafy lichens that can grow at and below water level.

Response Statements

  • Response Statement - Eastern Waterfan (2015)

    This rare lichen is endemic to Eastern North America. In Canada, it is known only from New Brunswick, Nova Scotia and Québec. It grows at or below water level in cool, clear, partially-shaded streams. It is threatened in the short term by disturbance from activities which cause stream siltation, alteration of microclimate and declines in water quality. In the longer term, changes in weather patterns that alter water levels and flow in its preferred habitat are another threat.


  • Order Acknowledging Receipt of the Assessments Done Pursuant to Subsection 23(1) of the Act (2017)

    His Excellency the Governor General in Council, on the recommendation of the Minister of the Environment, acknowledges receipt, on the making of this Order, of the assessments done pursuant to subsection 23(1) of the Species at Risk Act by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) with respect to the species set out in the annexed schedule.

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2013-2014 (2014)

    Under Canada’s Species at Risk Act (SARA), the foremost function of COSEWIC is to "assess the status of each wildlife species considered by COSEWIC to be at risk and, as part of the assessment, identify existing and potential threats to the species". COSEWIC held two Wildlife Species Assessment Meetings in this reporting year (October, 2013 to September, 2014) from November 24 to November 29, 2013 and from April 27 to May 2, 2014. During the current reporting period, COSEWIC assessed the status or reviewed the classification of 56 wildlife species. The wildlife species assessment results for the 2012-2013 reporting period include the following: Extinct: 0 Extirpated: 0 Endangered: 23 Threatened: 12 Special Concern: 20 Data Deficient: 0 Not at Risk: 1 Total: 56 Of the 56 wildlife species examined, COSEWIC reviewed the classification of 40 that had been previously assessed. The review of classification for 25 of those wildlife species resulted in a confirmation of the same status as the previous assessment.

Consultation Documents

  • Consultation on Amending the List of Species under the Species at Risk Act : Terrestrial Species - January 2015 (2015)

    The Government of Canada is committed to preventing the disappearance of wildlife species at risk from our lands. As part of its strategy for realizing that commitment, on June 5, 2003, the Government of Canada proclaimed the Species at Risk Act (SARA). Attached to the Act is Schedule 1, the list of the species provided for under SARA, also called the List of Wildlife Species at Risk. Extirpated, Endangered and Threatened species on Schedule 1 benefit from the protection of prohibitions and recovery planning requirements under SARA. Special Concern species benefit from its management planning requirements. Schedule 1 has grown from the original 233 to 521 wildlife species at risk. Please submit your comments byApril 15, 2015, for terrestrial species undergoing normal consultationsand byOctober 15, 2015, for terrestrial species undergoing extended consultations.For a description of the consultation paths these species will undergo, please see:Species at Risk Public Registry website