Aquatic Invasive Species Research: Tracking Origins, Examining Population Structure and Economic Impact of the Invasive Green Alga Codium fragile in the Northwest Atlantic

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Project Type: 
Research
Project Number: 
AISR-05-094 NSI Grant
Inception Date: 
2007
Completion Date: 
2009

Participants:

Anita Klein UNH - Department of Biological Sciences Principal Investigator
Arthur Mathieson UNH - Jackson Estuarine Lab Co-Principal Investigator
Kelly Giraud Cullen UNH - Department of Natural Resources & the Environment Associate Investigator

Students Involved:

Lucy Pleticha UNH - Department of Biological Sciences
Christopher Benton UNH - Department of Biological Sciences
Renee Eriksen University of New Hampshire
Matthew Mackenzie UNH - Department of Molecular, Cellular & Biomedical Sciences
Abstract: 
Codium fragile is an invasive green seaweed that arrived in Long Island Sound in the late 1950s. It has a large (>1-2 ft.) dichotomous thallus. Growing from a holdfast on rocks or molluscs, the buoyant thallus can lift and carry molluscs away in heavy seas; hence, C. fragile’s common name, “Oyster thief.” Codium fragile may also smother molluscs or urchins. At the Isle of Shoals Codium fragile has overgrown urchin barrens, displacing native kelps that are an important habitat for juvenile fish (cf. Mathieson et al. 2003; Expansion of the Asiatic green alga Codium fragile subsp. tomentosoides in the Gulf of Maine. Rhodora 105:1-53).The purpose of this project was to document the current distribution of the alga in New England and the Canadian Maritimes, use molecular tools to identify the origins of C. fragile populations in the Northwest Atlantic, and model the economic impacts of the invasive alga on mollusc and sea urchin fisheries.  
 
Phycologists recognize multiple subspecies of Codiumfragile from temperate coastal areas around the world. It is hard to distinguish some of these different subspecies based solely on grow morphology; however, they can be delineated by chloroplast gene sequences (Provan et al. 2008, Diversity and Distributions 14:343-354). The taxonomic nomenclature for these subspecies has recently been revised so that what has been known as C. fragile subsp. tomentosoides is now identified as C. fragile subsp. fragile (Maggs and Kelly in Brodie et al. 2007; Green Seaweeds of Britain and Ireland, British Phycological Society, pgs.189-201).
 
Only C. fragile subsp. fragile is considered invasive, but several reports (Garbary and Hubbard 2002, Botanica Marina 45:476-485, and Kusakina et al. 2006, Botanica Marina 49: 1-9) have suggested that C. fragile subsp. atlanticum, has also spread along Prince Edwards Island Canada and parts of Nova Scotia. One goal of this project has been to verify whether or not there has been more than one introduction of C. fragile to the Northwest Atlantic. Chloroplast DNA polymorphisms distinguish the subspecies C. fragile subsp. atlanticum from C. fragile subsp. fragile (Provan et al. 2008, op. cit.).
Objectives: 
The specific objectives of this project were six fold:
 
1. Develop a coordinated field/ecological and genetic evaluation of C. fragile ssp. tomentosoides for Northwest Atlantic populations, documenting their distribution, abundance and population structure.
 
2. Develop molecular markers that will confirm whether another strain or a second introduced subspecies (i.e. subsp. atlanticum) occurs within in the Canadian Maritimes and has contributed to the localized explosion of Codium in the Gulf of Maine.
 
3. Use nuclear and plastid microsatellite markers to compare genetic structures of early and more recently established populations- i.e. establish whether they are differentiated (e.g. closely or distantly related) and whether hybridization has occurred.
 
4. Evaluate the economic impact of Codium fragile in the Gulf of Maine.
 
5. Use the results from 1-4 to make recommendations to prevent further spreading of Codium, which will be disseminated as a report to managers of coastal/estuarine reserves.
 
6. Develop educational materials (website, pamphlets) for coastal resource groups, State Fish and Game staff, etc. that monitor coastal resources, to train them to recognize new populations of Codium.
Methodology: 
We will continue to document the distribution and spread of Codium fragile in the Gulf of Maine. Chloroplast and mitochondrial haplotypes of established and new populations will be compared to potential source populations in the Northeast Atlantic and Northwest Pacific ( the geographic origin of the species) to test the hypothesis that multiple introductions of the invasive alga have contributed to its recent dramatic expansion in the Gulf of Maine (Mathieson et al. 2003). An input/output economic assessment model will be constructed to estimate the alga's impact on the regions' economy. The combined assessment of the status of C. fragile in the Gulf of Maine will be used to address whether it is appropriate to impose more stringent control measures to prevent the spread of the alga to areas which are not yet infested.
Rationale: 

Codium fragile ssp. tomentosoides (here after C.f. ssp. tomentosoides) is one of the most aggressive and invasive macroalgal species in temperate regions worldwide (Trowbridge 1999). It has caused many problems with shellfish, including uplifting and transport due to its buoyancy; hence its common name "oyster thief.” Codium can also negatively alter natural nursery habitats for juvenile fish. Over a nineteen year period this alga has spread dramatically in the Gulf of Maine, with 81 records from the Gulf of Maine and a 26 fold increase in southern Maine and New Hampshire (Mathieson et al. 2003). A combination of new demographic and molecular population genetic studies may provide retrospective information about the geographic origins of newly recorded populations (e.g., at the Isle of Shoals, N.H./Maine; Nubble Light, York, Maine). With more precise information about how Codium spreads, improved containment policies may be possible. Input-output models of the state economies of Maine, New Hampshire and Massachusetts will be made in order to estimate the effect of C. f. ssp. tomentosoides on commercial and recreational shellfishing, and the resulting impact on three states’ economy (Maine, New Hampshire, Massachusetts). The proposed research addresses four goals of Sea Grant's Aquatic Nuisance Species Research and Outreach Program: (1) Basic research on population dynamics and genetics of non-indigenous species; (2) Effects on ecosystems; (3) Socioeconomic impact(s); and (6) Reducing the spread of established populations.

Accomplishments: 

2013

New sightings of invasive seaweed indicate its geographic distribution is spreading
N.H. Sea Grant-funded researchers have been tracking the distribution of the invasive green seaweed Codium fragile throughout New England and the Canadian Maritimes. They have collaborated with the Gulf of Maine Research Institute to verify any sightings of Codium reported by the public on the website www.vitalsignsme.org, a site that encourages K-12 student participation in invasive species sightings. In 2013, six new Codium sightings ranging from Bristol to Falmouth, Maine, were reported to the site and verified by Sea Grant researchers. These observations suggest that Codium is beginning to spread east along the coast of Downeast Maine. This research and collaboration will help resource managers monitor any impacts by Codium on native species and provide insight into climate change effects.

Genetic analyses indicate similarities in invasive seaweed subspecies in Northwest Atlantic
Researchers have been tracking the spread of the invasive green seaweed Codium fragile in the Northwest Atlantic and conducting genetic analyses on specimens they have collected. Previous Sea Grant-funded research indicated that the specimens found in Malpeque Bay in Prince Edward Island, Canada, were a distinct morphotype that differed from the rest of the Codium fragile specimens on the Eastern Seaboard. In 2013, researchers refined their results and determined that this is not a new genotype, but instead is the same subspecies (Codium fragile subspecies fragile) as found from Long Island Sound to Prince Edward Island in Canada. This clarification of research results will help improve geographic distribution tracking efforts for the invasive seaweed.

2012

Evaluation of Invasive Seaweed Indicates Similarities, Differences among Populations for Improved Tracking
The invasive green seaweed Codium fragile has overgrown urchin barrens and displaced native kelps near the Isles of Shoals off the coast of New Hampshire. Sea Grant-funded researchers are documenting the current distribution of C. fragile in New England and the Canadian Maritimes. As part of this effort, researchers collected more than 330 C. fragile plants from the Canadian Maritimes south to Long Island Sound. Representative plants from each population were pressed and deposited in UNH’s Albion Hodgdon Herbarium. Researchers evaluated the swollen terminal portion — the utricle — of the plant’s thallus under a microscope. Utricle attributes were evaluated for each population. In 2012, researchers found that while there was significant variation within and between different C. fragile populations, the samples from the Canadian Maritimes and the Gulf of Maine were more similar to each other and distinct from C. fragile populations in Long Island Sound. These results will help scientists track changes in the distribution and potential impacts of C. fragile on native species and habitats.

Invasive Seaweed Database Encourages Community Engagement, Professional Development
Documenting the current distribution of the invasive green seaweed Codium fragile in New England is important to monitor its potential range expansion or contraction and related impacts on native species. Sea Grant-funded researchers continue to work with the Gulf of Maine Research Institute (GMRI) to maintain the website www.vitalsignsme.org, where the public can report any C. fragile sightings and researchers can verify any reports that come in. During 2012, the sightings database was used by GMRI staff at two teacher professional development institutes and almost 90 C. fragile sightings have been reported to the site. Continued collaboration and community engagement via this website will allow researchers to track any expansion or contraction of C. fragile’s range, the potential for impacts on native species, and similar implications potentially related to climate change.

2011

Researchers Develop Website to Monitor Codium fragile
The invasive green seaweed “Codium fragile” has overgrown urchin barrens and displaced native kelps near the Isles of Shoals off the coast of New Hampshire. In order to document the current distribution of C. fragile in New England and the Canadian Maritimes, Sea Grant-funded researchers developed the website www.codium.unh.edu to engage the public’s help in identifying new populations of the species. The web site features photos and historic and geographic information about the species and its ecologic and economic impacts. The public is encouraged to report any C. fragile sightings to the web site www.vitalsignsme.org, where researchers are collaborating with the Gulf of Maine Research Institute to verify any reports that come in. Continued monitoring of its distribution will help researchers track any expansion or contraction of its range, the potential for impacts on native species and similar implications potentially related to climate change.

Ph.D. Student Identifies New Genotype of “Codium fragile”
The invasive green seaweed “Codium fragile” has overgrown urchin barrens and displaced native kelps near the Isles of Shoals off the coast of New Hampshire. NHSG-funded researchers are documenting the current distribution of “C. fragile” in New England and the Canadian Maritimes. As part of this effort, a UNH Ph.D. student identified a new genotype of “C. fragile” in samples collected in Malpeque Bay, Prince Edward Island. The distribution of the new genotype seems to be restricted to the northern portion of the bay and is correlated with a distinctive morphology of “C. fragile.” Continued monitoring of its distribution will help researchers track any expansion or contraction of its range, the potential for impacts on native species and similar implications potentially related to climate change.

Publications

Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant

Thesis/Dissertation

  • Pleticha, L. (2009). Morphological variation in "Codium fragile" in the northwest Atlantic. Master's Thesis, University of New Hampshire.
  • Benton, C. (2014). Evaluating taxonomic variation, ecology and the transcriptome of Codium fragile in the NW Atlantic. Doctoral dissertation, University of New Hampshire.