• Morro Bay seagrass loss causes change in

    From ScienceDaily@1:317/3 to All on Fri Oct 29 21:30:38 2021
    Morro Bay seagrass loss causes change in fish populations

    Date:
    October 29, 2021
    Source:
    California Polytechnic State University
    Summary:
    The loss of seagrass habitat caused a dramatic shift in
    fish species in Morro Bay. Areas once covered with lush
    seagrass meadows and unique fish species are now home to
    muddy-seafloor-loving flatfish. The research team saw decreasing
    numbers of seagrass-specialist fish species, and an increase in
    flatfishes like the speckled sanddab and staghorn sculpin.

    The loss of eelgrass habitat along the California coast presents
    a problem for species that depend on seagrass.



    FULL STORY ==========================================================================
    The loss of seagrass habitat caused a dramatic shift in fish species
    in Morro Bay. Areas once covered with lush seagrass meadows and unique
    fish species are now home to muddy-seafloor-loving flatfish, according
    to a paper by Cal Poly researchers published in the October 2021 print
    edition of Estuaries and Coasts.


    ========================================================================== Seagrass meadows were previously common throughout the Morro Bay estuary
    but nearly disappeared over the last decade.

    "Seagrass, like the eelgrass in Morro Bay, is important because it
    supports a range of marine life," said Jennifer O'Leary, who led
    the research as a California Sea Grant extension specialist based at
    Cal Poly. O'Leary is now the Western Indian Ocean coordinator for the
    Wildlife Conservation Society. "It's like the trees in a forest -- these underwater plants provide food, structure, and shelter to many of the
    marine animals that live in the bay." Underwater seagrass meadows are
    one of the main habitats in coastal estuaries, and represent one of the
    most biologically productive biomes on our planet. Yet seagrass habitats
    are being lost at an alarming rate, and their decline now rivals those
    reported for tropical rainforests, coral reefs, and mangroves.

    Loss is usually the symptom of a larger problem, and seagrasses are
    therefore considered "coastal canaries." Their decline signals important
    losses to biodiversity and often impacts the communities that depend
    on them.

    Morro Bay, one of 28 estuaries that the U.S. Environmental Protection
    Agency designated as critical to the economic and environmental health
    of the nation, has seen a dramatic loss in its seagrass habitat. Once
    dominated by a common California eelgrass (Zostera marina), seagrass at
    this site has declined by more than 95 percent, from covering 344 acres
    in 2007 to less than 15 acres in 2017.

    Seagrass meadows are a multifaceted habitat that secure sediments with
    their root systems, and provide food, shelter and nurseries for many
    types of fish and invertebrates. When seagrass meadows are lost, they
    are often replaced with a less dynamic, muddy seafloor habitat.



    ========================================================================== O'Leary and colleagues found that seagrass loss did not result in fewer
    fish but rather led to changes in the types of fish that live in the
    bay. The research team saw decreasing numbers of some seagrass-specialist
    fish species, such as the bay pipefish (Syngnathus leptorhynchus). With
    long thin bodies and olive green coloration, bay pipefish are adapted
    to hide among the seagrass blades.

    In contrast, researchers observed an increase in flatfishes like
    the speckled sanddab (Citharichthys stigmaeus) and staghorn sculpin (Leptocottus armatus).

    These fish have flat bodies that are ideal for life along the muddy
    seafloor and are common residents in California bays and estuaries. These species have moved into the former eelgrass habitats and now make up
    the majority of the fish species present in Morro Bay.

    The loss of eelgrass habitat along the California coast presents a larger problem for species that depend on seagrass, like the bay pipefish. If
    seagrass doesn't recover, then the surviving meadows will be further apart
    and have a more fragmented, or patchy, distribution. This distance and patchiness of habitat may impact specialists, like pipefish, by impairing
    their ability to move to a new habitat to find food or mates. This
    community isolation may alter the genetic structure and diversity of
    the overall pipefish population over time.

    "The relatively sudden and near complete collapse of eelgrass in Morro
    Bay has not only changed fish populations, but it has also resulted in substantial changes to estuary physics and geomorphology," said study
    coauthor Ryan Walter, a Cal Poly physics professor who has been studying eelgrass loss through a California Sea Grant-funded research project
    that was launched in 2018.

    Walter, O'Leary and other Cal Poly researchers, in conjunction with
    the Morro Bay National Estuary Program, continue to study the cause and consequences of the eelgrass decline. In another study, the team recently
    found that the loss of eelgrass in Morro Bay led to widespread erosion,
    or loss of sediment, throughout the estuary.

    The new research sheds additional light on changes within Morro Bay that
    may inform how scientists learn about seagrass communities throughout California.

    There has not been an eelgrass decline on the United States Pacific
    Coast of this magnitude, making Morro Bay a novel event that may help
    predict future estuarine change.

    A multifaceted approach to protect and enhance the remaining seagrass
    will be essential, according to the researchers. There is hope for the
    future as the remaining eelgrass is slowly expanding with protection
    and local planting initiatives, including successful transplant efforts
    led by the Morro Bay National Estuary Program. Walter and O'Leary have
    used drone-based surveys to document natural expansion and recovery of
    eelgrass in areas where it was lost.

    The mere 9.4 acres of seagrass left in Morro Bay in 2017 expanded to
    36.7 acres by 2019. The researchers are still analyzing data from 2020
    but are optimistic that the seagrass acreage continues to slowly increase.

    ========================================================================== Story Source: Materials provided by
    California_Polytechnic_State_University. Note: Content may be edited
    for style and length.


    ========================================================================== Journal Reference:
    1. Jennifer K. O'Leary, Maurice C. Goodman, Ryan K. Walter, Karissa
    Willits,
    Daniel J. Pondella, John Stephens. Effects of Estuary-Wide Seagrass
    Loss on Fish Populations. Estuaries and Coasts, 2021; 44 (8):
    2250 DOI: 10.1007/s12237-021-00917-2 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2021/10/211029134032.htm

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