This indicator summarizes the cumulative number of aquatic alien species in the Great Lakes and the rate at which introductions have occurred.
Figure 1. Cumulative number of established aquatic alien species in the Great Lakes by decade (note: protists includes algae, diatoms and protozoans; invertebrates includes annelids, bryozoans, coelenterates, crustaceans, insects, mollusks and platyhelminthes).
Figure 2. Number of established aquatic alien species discovered in the Great Lakes per decade.
- The number of aquatic alien species in the Great Lakes basin has steadily increased since the first species was documented in the 1840s. As of 2017 183 alien species were established.
- The rate of newly established species increased up to decade ending in 1999. Between 1839 and 1950, 6.9 new species were established per decade. Between 1950 and 1999, the rate increased to 17 newly established alien species per decade. This increased rate of introduction coincides with the opening of the St. Lawrence Seaway in 1959. It may also reflect increased detection efforts.
- Only one alien species, a planktonic crustacean (Thermocyclops crassus) has been discovered as established in the Great Lakes since 2010. The fact that only one new alien species has been established since 2010 may reflect a decrease in the invasion rate due to increased prevention efforts as well as the fact that accounting for the current decade is incomplete. No new fish species and a reduced number of invertebrate species have been detected since 2000.
Invasive species are one of the main threats to biodiversity at the global level and are a growing environmental and economic threat to Ontario (MEA 2005; OMNR 2012). Invasive species often act together with threats such as habitat loss and climate change to accelerate the loss of Ontario’s biodiversity. Ontario’s aquatic ecosystems have been particularly impacted by invasive species. Well-known examples of aquatic invasive alien species in Ontario include Round Goby, Zebra Mussel, and the European sub-species of Common Reed (Phragmites). The Great Lakes have a long and well-documented history of aquatic alien species invasions (Mills et al. 1993, Ricciardi 2006). The Great Lakes are also the entry point for many alien species that subsequently invade Ontario’s inland lakes and streams.
This indicator summarizes the cumulative number of established aquatic alien species in the Great Lakes and the rate at which establishments have occurred. Not all of these species are considered invasive – invasive species are those harmful alien species whose introduction or spread threatens the environment, the economy or society, including human health (OMNR 2012). Risk assessments to determine which species are invasive have not been completed for all alien species in the Great Lakes, so this indicator uses the number of alien species as an index of risks related to invasive species.
A companion indicator that provides an index of alien species in Ontario’s inland lakes has also been developed. Comparable, comprehensive information on the distribution of terrestrial alien species and their introduction dates is not currently available, but is being assembled for the possible development of a terrestrial indicator.
The current list of alien species in the Great Lakes was downloaded from the Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS – NOAA 2017). Species included are not native to any part of the Great Lakes basin, but are established in the Great Lakes and connecting waters. The database includes information on the origin of species and the year that they were first collected. Species were grouped into five taxonomic categories (bacteria/viruses, protists, plants, invertebrates and fishes) and the cumulative number and number of invasions per decade were graphed (Figures 1, 2).
There are some important caveats with respect to the information used for this indicator: some species established in U.S. waters of the Great Lakes and not yet found in Ontario waters are included; species native to one part of the Great Lakes basin that have been introduced to a new part of the basin are not included; and potential alien species whose origins are not clearly known are not included. Additional alien species are likely present and have not yet been found or established. Concern regarding ecological impacts of alien species over the last two decades has resulted in increased surveillance effort during this period. There has also been no overall assessment to determine which species have been harmful. Some species, such as Rainbow Trout and Pacific salmon are stocked and managed to provide continued economic and societal benefits. However, this database is the best available information and is a good indicator of the risk to Ontario’s biodiversity posed by alien species in the Great Lakes Ecozone.
Invasive plants are an immediate and growing threat to Ontario’s biodiversity, economy and society. They spread aggressively, choking out native vegetation, threatening our natural areas, and the species that depend on them. They can also degrade agricultural lands, and impact forest regeneration, costing Ontarians millions of dollars annually in control costs and lost productivity. Invasive Phragmites or European Common Reed (Phragmites australis subsp. australis) has been described as Canada…Read More
Last Updated: October 13, 2017