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Every 8.4 days on average, a non-indigenous species is detected in aquatic ecosystems, new study finds

Date: 5 October 2020

A new study by the Working Group on Ballast and Other Ship Vectors (WGBOSV) of the International Council for the Exploration of the Sea (ICES), the Intergovernmental Oceanographic Commission (IOC) and the International Maritime Organization (IMO) and the ICES Working Group on Introduction and Transfers of Marine Organisms (WGITMO) indicates that introductions of aquatic non-indigenous species (ANS) have occurred at an alarming rate for the past 50 years.

Since 1965, 1,442 unique species have been detected outside of their native habitats across 49 global aquatic ecosystems – approximately one new detection every 8.4 days.

This synthesis highlights the magnitude of recent ANS detections, but the real numbers may well above those recorded by scientists. Many ANS go unreported due to limited search effort and diminishing taxonomic expertise.

Zebra mussels
Zebra mussels (Dreissena polymorpha), an invasive species of freshwater mussel, on the propeller and shaft of a sailing yacht on Lake Erie. © Shutterstock/Jeff Caughey

The 1,442 unique species recorded in the study is more than ten-fold lower than the number of non-indigenous species observed in terrestrial ecosystems. This can be partly explained by the fact that  land biodiversity is vastly higher than the combined diversity of  marine and freshwater ecosystems, and thus more non-indigenous species would be proportionally expected in terrestrial systems. However, the truth remains that the documentation of the diversity of invasions in marine, estuarine and freshwater habitats has significantly lagged behind similar research on land.

“We suspect that we may be at the tip of an invasion iceberg in understanding the scale of introductions in coastal environments”

The introduction of species across biogeographic barriers by human activities is recognized as one of the major drivers of biodiversity change. Global warming has enabled non-indigenous species to expand into regions where previously they were not able to survive and reproduce, thus making it even more urgent for conservation policy and management to take urgent action to prevent new introductions and further spread of these species.

Studies such as this one, based on national and regional inventories of non-indigenous species, are only reliable if local experts can maintain and continually update lists of new records. It will be fundamental to continue and to expand research and survey efforts across aquatic ecosystems (marine, estuarine and large freshwater ecosystems), including by implementing standardized methods across regions and taxa to better inform both regional and global policy development and management activities.


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About the authors

The ICES-IOC-IMO Working Group on Ballast and Other Ship Vectors (WGBOSV) and the ICES Working Group on Introduction and Transfers of Marine Organisms (WGITMO) enjoy a very close working relationship. For nearly 20 years, the groups have met jointly during one of the three days of their respective annual meetings to discuss new research findings, share ideas, and develop future collaborations.  These two international working groups are composed of scientists – with extensive knowledge of ship-mediated biological invasions – who strive to advance the scientific understanding needed to guide management and policy decisions. Currently, they collaborate on two shared Terms of Reference: the introduction and transfer of biofouling organisms through ship vectors, as well as climate change impacts on the establishment and spread of ship-mediated nonindigenous species, particularly as they relate to the Arctic.

Related content: IOC work on invasive species

In the future, it is expected that molecular methods will support the rapid and standardized detection of threats from invasive species. The analysis of DNA in the environment can be used to identify the species present at each location through sequence analysis and comparisons to reference databases, without the need for extensive morphological identification. The IOC is active in developing the use of new molecular methods to monitor invasive species in the pacific with the PacMAN (Pacific Islands Marine Bioinvasions Alert Network) project. Through this 3-year project an invasive species monitoring plan will be established in Fiji, that will enable the rapid surveying of local marine biodiversity in risk areas for the purpose of identifying threats from invasive organisms. This project will provide environmental managers with a decision support tool, as well as a standardized data management system, that could be easily adapted to other regions. Though care is needed in the development of molecular based methods due to errors in sequence identification, these methods could ultimately provide a new way to follow the spread of invasive species at the global level.