When history meets ecology: Connecting European exploration and biodiversity in the northwest Atlantic

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Hediste diversicolor (top; E. Kristensen, marinespecies.org) and Corophium volutator (bottom; M. Storey, bioimages.org.uk)
Hediste diversicolor (top; E. Kristensen, marinespecies.org) and Corophium volutator (bottom; M. Storey, bioimages.org.uk)
Although it doesn’t happen often, the intersection of academic fields (such as history and science) can lead to exciting and important discoveries. For example, historical records of human migration and modes of transportation can provide insight into the broad-scale distribution of various organisms, ultimately telling us how and when certain animals arrived where they are today. In fact, the above-mentioned example has recently provided insight into where some species of marine organisms in the northwest Atlantic Ocean originated from, along with when and how they likely got there.
Using genetic techniques, Tony Einfeldt, a Ph.D. student in Dr. Jason Addison’s lab at the University of New Brunswick in Fredericton, NB, Canada, and his colleagues  have discovered that benthic marine worms and amphipods, which reside within mudflats of the northwest Atlantic coast, likely arrived there in the ship ballast of early European explorers. Einfeldt et al. compared the genetic structure of various populations of ragworms (Hediste diversicolor) and amphipods (Corophium volutator) residing within the Bay of Fundy and the Gulf of Maine to those along the Atlantic coast of Europe. Similarities in the genetic identity between North American and European populations are highly suggestive that the northwest Atlantic populations originated from the European coast. As Einfeldt states, “We can tell where they came from because the genetic identity of both species in the Bay of Fundy matches that of those in Europe.” Furthermore, with such precise technology and methodology, Einfeldt et al. were able to isolate two separate introductions of these species from Europe, with Bay of Fundy populations likely originating from the Bay of Biscay in France and Gulf of Maine populations coming from more northerly European nations (Norway, Denmark, Germany, etc.).
But how did they get there? To answer this question, Einfeldt et al. attempted to match the movement of these benthic invertebrates with human movement throughout history. Of course, one mode of the intercontinental dispersal of marine organisms is through the ballast water of ships, as ships empty and refill their ballast when they dock, allowing species from one coast to enter the ship through refilling and be introduced to another coast through emptying. But the species studied by Einfeldt et al. are not among those found in modern ballast water, likely because they are infaunal organisms, meaning that they reside within bottom sediment of marine intertidal areas (i.e., mudflats). However, historically, not all ballast was in the form of water. Early European explorers, including those to first cross the Atlantic, most often used rocks for ballast, along with (you guessed it) mud! In fact, the earliest known European ships to have used mud and rocks for ballast are those of Samuel de Champlain and Henry Hudson in the 1600’s, although dry ballast was used up until the 1800’s, making the point of introduction quite difficult to identify.
Some marine species in the northwest Atlantic, such as H. diversicolor and C. volutator, may have arrived here through the ballast of early European explorers. Source: Wikipedia
Some marine species in the northwest Atlantic, such as H. diversicolor and C. volutator, may have arrived here through the ballast of early European explorers. Source: Wikipedia
Although the time window of introduction is quite wide (~200 years), the results of Einfeldt et al. provide strong evidence that the presence of H. diversicolor and C. volutator along the Atlantic coast of North America is a result of European exploration and migration to North America. What’s more is that these two species are important drivers of their respective ecosystems, particularly in the Bay of Fundy. Many species of fish feed on these benthic invertebrates, while migrating shorebirds often depend on the abundance of these species in Bay of Fundy mudflats for food during annual migrations. Ultimately, if these species were never introduced to the northwest Atlantic coast, the diversity of animals that reside there, either permanently or temporarily, may be very different than it is today.

Acknowledgements

I’d like to thank Tony Einfeldt of UNB Fredericton for taking the time to chat and provide input into this post. I also want to thank Shane Fowler, CBC correspondent, for sparking my interest in publishing this post and for his dedication to the promotion of science in New Brunswick.
For those interested, the peer-reviewed publication in Invertebrate Biology can be found here.
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