|Laura Gallant - Invasions Ecology Lab
Cornell University, Ithaca, NY
I studied the invasive barnacle species Eliminius modestus . E. modestus is natively found in New Zealand and Southern Australia, but was introduced to Europe in 1945 and is now established throughout Europe from Germany to Gibraltar. With such an obvious ability to spread and establish itself one is left wondering why E. modestus has not appeared on the Western side of the Atlantic. I searched the literature for information on E. modestus life history and environmental tolerances and then used this information to determine where E. modestus would likely invade on the United States East Coast. I then looked at settlement plates from a site close to this area and checked for the presence of E. modestus .
E. modestus has wide temperature and salinity tolerances. Although its native temperature range is 4-21 ° C, it can survive temperatures outside of this range. E. modestus can survive relatively low salinities and competes well in estuarine environments. It is a year round breeder and can release larvae anytime the temperature is above 6 ° C and salinity is above 21 PSU. It matures quickly and can go from settlement to reproductive maturity in 8 weeks. This allows it to compete well with native European barnacles that breed only once per year and take longer to mature.
The temperature in the Chesapeake Bay varies from 1-27 ° C over the year. Although this is a wider range than E. modestus experiences in its native habitat, I found no evidence in the literature that these temperatures would prevent adult or larval survival. The Chesapeake is also near the overlap of the ranges of cold and warm water barnacle species. It is at this range overlap that E. modestus survives best in Europe. I checked 10 plates from 9 different locations of the 2000 Chesapeake spatial fouling survey. I found no evidence of E. modestus . Common barnacle species of the Chesapeake appear to be Balanus eburneus and Balanus improvisus , both are known to prefer estuarine conditions.There may be many as yet undiscovered reasons for E. modestus ' absence from our coast. Although many barnacle species are common on both sides of the Atlantic, there may be native species in America that are absent from Europe that are capable of out-competing E. modestus . There may also be a predator present in America that prevents E. modestus from establishing itself. The literature on temperature and salinity tolerances was often contradictory and included broad ranges perhaps, despite appearances, the temperature of the Western Atlantic coast is simply too extreme for E. modestus survival.
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