Brachionus quadratus Rousselet, 1889, Brachionus reticulatus Kertész, 1894, Brachionus quadratus rotundus Rousselet, 1907, Brachionus quadratus tridentatus Zernov, 1901

Potential pathway of introduction: Shipping (Ballast sediment)

Brachionus ledygii has been identified as having high probability of introduction to the Great Lakes via residual ballast sediment, where its resting stage is able to survive high salinities during ballast water exchange (Bailey et al. 2004, 2005a, 2005b; Johengen et al. 2005). In a survey of the ballast water of 35 different vessels entering the Great Lakes, this species was found hatched from diapausing eggs in residual ballast sediment in four of the ships. Additionally, it was isolated from the sediment of those ships with a mean density of 3 individuals/40 g sediment (Bailey et al. 2005a; Johengen et al. 2005). It is likely that these resting stages are deposited by reproducing females taken in with ballast water rather than being brought in with disturbed sediments. Diapausing eggs present in sediment can pose an invasion risk if they are discharged during ballast operations or if they hatch during a voyage and the young rotifers are subsequently introduced during vessel deballasting (Gray and MacIsaac 2010). Of the 76 distinct taxa with a resting stage identified in this survey, Brachionus spp. were the most common and abundant of the Great Lakes non-natives (Bailey et al. 2005a). Brachionus spp. are a predominant component of the planktonic community in the lower Rhine River, a region where ballast is commonly taken for ships entering the Great Lakes (van Dijk and van Zanten 2005). However, this primarily freshwater species is less abundant in other ballast loading regions such as the Baltic Sea and coastal areas with high salinity (Viitasalo et al. 1995).

In more recent studies conducted since the 2006 (Canadian bound vessels) and 2008 (U.S. bound vessels) expansion of mandatory ballast flushing regulations to vessels with unpumpable ballast tank residuals, however, B. leydigii has been identified as having a significantly lower probability of introduction (Government of Canada 2006; Briski et al. 2010; Gray and MacIsaac 2010). Brachionus leydigii was not observed in ballast sediment collected in 2007 and 2008 from 19 ballast tanks of 17 randomly selected Great Lakes bound ships originating from European, South American, and Atlantic ports (i.e. after the new regulations were in place) (Briski et al. 2010). Furthermore, in situ hatching studies suggest that fewer than 1% of diapausing invertebrate eggs will hatch and become available for introduction. The likelihood of this species entering the Great Lakes is therefore reduced as compared to species that may become resuspended in ballast water (Johengen et al. 2005). Additionally, Santagata et al. (2008) report a 100% mortality rate for rotifers exposed to full strength seawater for one hour in both empty-refill and flow-through treatments.

Brachionus leydigii has a moderate probability for establishment if introduced to the Great Lakes (Confidence level: Moderate).

This species produces a resting stage consisting of a three-layered diapausing egg that is protected from external stressors, such as desiccation and temperature extremes, until conditions become favorable and a viable individual hatches (Wurdak et al. 1978; Sládecek 1983; Clement and Wurdak 1991). This reproductive strategy leads B. ledygii to having high Great Lakes invasion potential, as diapausing eggs can be resistant to short term salinity exposure, are not easily flushed from ballast tanks, and have the potential for in situ hatching during a transoceanic voyage (Bailey et al. 2004, 2005a, 2005b, 2006; Gray et al. 2005; Gray and MacIsaac 2010). However, viability of similarly resistant diapausing copepods and cladoceran eggs is low under conditions of low oxygen or anoxia (Uye 1980; Uye et al. 1984; Carvalho and Wolf 1989).

Branchionus leydigii is distributed globally and present in a variety of physical and environmental conditions. Bailey et al. (2005a) and Johengen et al. (2005) reported this species as having a habitat match to the Great Lakes, able to hatch in a 0 ppt salinity medium. Additionally, because B. leydigii thrives in primarily eutrophic conditions, the central and western basins of Lake Erie may provide suitable habitat due to their high eutrophication potential (Summers 2001). Johengen et al. (2005) report observing one B. leydigii individual in an upper-wing ballast tank of a surveyed vessel, leading the authors to suggest that this may have been the result of a previous transoceanic ballast introduction to Hamilton Harbor, as residual sediments generally do not accumulate in upper-wing tanks. Because only a single individual was recorded, the status of establishment cannot be determined, but this finding may indicate that B. leydigii has been introduced previously to this location (Johengen et al. 2005).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Beneficial

There is little or no evidence to support that Brachionus leydigii has the potential for significant socio-economic impacts if introduced to the Great Lakes.

As a group, introduced rotifers are not known to generate significant socio-economic impacts (O'Connor et al. 2008), and there are currently no reports of this species leading to negative impact in introduced areas.

There is little or no evidence to support that Brachionus leydigii has the potential for significant beneficial effects if introduced to the Great Lakes.

Rotifers have been widely used as a bioindicator species in pollution monitoring, and due to their sensitivity to pollutants and ease of culture, they have become important tools in ecotoxicological testing (Wallace 2002). However, there is no evidence supporting that B. leydigii will offer any advantage as an ecological indicator as compared to rotifers already present in the Great Lakes.

There are no known regulations for this species.*

*Ballast water regulations applicable to this species are currently in place to prevent the introduction of nonindigenous species to the Great Lakes via shipping. See Title 33: Code of Federal Regulations, Part 151, Subparts C and D (33 CFR 151 C) for the most recent federal ballast water regulations applying to the Great Lakes and Hudson River.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Biological
There are no known biological control methods for this species.

Physical
There are no known biological control methods for this species

Chemical
There are no chemical control methods for this species.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.