• eDNA a useful tool for early detection o

    From ScienceDaily@1:317/3 to All on Wed Feb 16 21:30:52 2022
    eDNA a useful tool for early detection of invasive green crab

    Date:
    February 16, 2022
    Source:
    University of Washington
    Summary:
    As the green crab invasion in Washington state worsens, a new
    analysis method could help contain future invasions and prevent
    new outbreaks using water testing and genetic analysis.



    FULL STORY ========================================================================== European green crabs feast on shellfish, destroy marsh habitats by
    burrowing in the mud and obliterate valuable seagrass beds. The invasive species also reproduces quickly, making it a nightmare for wildlife
    managers seeking to control its spread in Washington's marine waters.


    ==========================================================================
    Last month, Gov. Jay Inslee issued an emergency order in response to
    more than 70,000 crabs caught on Lummi Nation land as well as dramatic increases in crab populations on Washington's outer coast and other
    locations in Puget Sound in recent years.

    As the green crab invasion in the state worsens, a new analysis method developed by University of Washington and Washington Sea Grant scientists
    could help contain future invasions and prevent new outbreaks using water testing and genetic analysis. The results, published online Feb. 6 in
    the journal Ecological Applications, show that the DNA-based technique
    works as well in detecting the presence of green crabs as setting traps
    to catch the live animals, which is a more laborious process. Results
    suggest these two methods could complement each other as approaches to
    learn where the species' range is expanding.

    The new method relies on genetic material in the environment, known as
    eDNA, that is found in the water after organisms move through. Scientists
    can collect a bottle of water from a location, extract DNA from the
    water and discern which species were present recently in that area.

    "We have limited resources to be able to combat this problem, and it's important to think about how to allocate those resources efficiently
    and effectively," said lead author Abigail Keller, who completed the
    work as a master's student in the UW School of Marine and Environmental Affairs. "Knowing the best situations for using eDNA to detect invasive
    green crabs is important, and that's what our study tried to tackle."
    The research team relied on data collected over three months in 2020
    from green crab traps in 20 locations throughout Puget Sound and the
    outer coast. Trapping at these locations was done by a large number
    of partners participating in statewide efforts to monitor and control
    European green crab, including multiple tribes, Washington Department
    of Fish and Wildlife -- the state lead for green crab management --
    Washington Sea Grant's Crab Team, and other state and federal agencies.



    ==========================================================================
    For this study, the researchers visited each location and collected
    water samples, then ran genetic analyses to detect both the presence
    and quantity of European green crab in each location. In this way they
    could validate the eDNA data with the actual presence and numbers of
    crabs. They found that using eDNA to detect the presence and abundance
    of the species was as sensitive as trapping and counting live crabs.

    This is significant, the researchers said, because eDNA as a detection
    method is new, and it hasn't always been clear how to interpret
    eDNA detections in past scenarios. This study shows how conventional
    monitoring methods -- in this case, trapping and counting crabs -- can
    be combined with eDNA techniques to more effectively find and control
    invasive species outbreaks.

    "Here's a really well-validated example of how to use eDNA in the
    real world.

    To me that's really exciting," said co-author Ryan Kelly, a UW associate professor in the School of Marine and Environmental Affairs. "There
    are lots of invasive species, and many imperiled and endangered species
    that are hard to monitor, so this is one significant way forward on all
    of those fronts." The study also evaluates when eDNA would add value
    in monitoring for invasive crabs, and when conventional trapping and
    counting still make the most sense.

    For example, taking water samples and testing for green crab DNA in remote locations -- or in areas where outbreaks haven't yet been identified --
    could save time and resources instead of deploying traps. Alternatively,
    eDNA probably wouldn't be helpful in locations where large numbers
    of green crabs are already living and where community scientists and
    managers are already trapping and controlling those populations, the researchers explained.

    "From a management perspective, the value of this tool just really comes
    to life in places that are more remote or have a lot of shoreline to
    cover, like Alaska, where green crabs haven't yet been detected," said co-author Emily Grason, a marine ecologist who leads the Washington Sea
    Grant Crab Team. "I see eDNA as another tool in the toolkit, and we can
    imagine scenarios where it can be used alongside trapping, especially
    as an early detection method." Finding these crabs soon after they have occupied a new location is important for controlling the population and protecting native habitats. Managers could get ahead of new invasions
    by testing water from multiple locations, and then follow up with more
    water testing, on-the-ground monitoring and trapping if green crab DNA
    is detected.

    The paper identified green crab DNA in one location where the species
    hasn't yet been captured, near Vashon Island. The research team followed
    up a year later with intensive trapping and retested the water; no green
    crabs or additional green crab DNA were found. The researchers think
    the earlier positive sample likely was picking up green crab larvae,
    which weren't present in that location a year later. Notably, the effort represented an important test case for how eDNA and traditional trapping
    can be implemented together for green crab management.

    "The reason we pursued this project in the beginning is that early
    detection of green crabs is difficult -- it's like finding a needle in
    a haystack," said co- author P. Sean McDonald, a UW associate teaching professor in environmental studies and aquatic and fishery sciences and
    the UW principal investigator for Crab Team research. "So if adding eDNA
    to our toolkit helps us detect those needles, then that's great to have at
    our disposal." Ana Ramo'n-Laca of the Cooperative Institute for Climate,
    Ocean and Ecosystem Studies is an additional co-author. This research
    was funded by Washington Sea Grant.

    ========================================================================== Story Source: Materials provided by University_of_Washington. Original
    written by Michelle Ma. Note: Content may be edited for style and length.


    ========================================================================== Related Multimedia:
    * Video_and_images_of_European_green_crabs ========================================================================== Journal Reference:
    1. Abigail G. Keller, Emily W. Grason, P. Sean McDonald, Ana
    Ramo'n‐Laca, Ryan P. Kelly. Tracking an invasion front
    with environmental DNA. Ecological Applications, 2022; DOI:
    10.1002/eap.2561 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220216140418.htm

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