This week our class embarked on a trip to the beautiful Coal Harbour Royal Vancouver Yacht Club. There, we scuttled about and examined the many invertebrate species making up the fouling communities* adorning the sides of the maze-like docks. As can be seen above, we brought highly sophisticated scientific measuring sticks.
*A fouling community simply refers to a community of organisms living on an artificial surface, in this case a dock.
The sticks were a hasty replacement for absent meter sticks and were used to measure experimental transects. A transect is simply an area where we count and record the number of invertebrate species present. While the technique is simple, we can gain a fair amount of information from it.
In a community, one individual can affect all other members of the community. For example, the presence of one species may prevent another from surviving. The opposite could also be true; the presence of one species may be necessary for another to survive. We aimed to see if any such a phenomenon might be happening with the invasive tunicate Botryllus schlosseri (also known as the golden star tunicate).
The picture above shows a colony of B. Schlosseri (orange) that has covered the exterior surface of a mussel. Believe it or not, these are invertebrate animals! In fact, they are more closely related to humans than any other invertebrate phyla! (Phyla, or singular phylum, is a fancy way to refer to a group of animals). During their larval stage, when they are free swimming and unattached, these tunicates look remarkably similar to the tadpoles of frogs.
Golden star tunicates are not native to British Columbia and are considered invasive. This means that the species was introduced to our shores from its native habitat: the North East Atlantic Ocean, the Mediterranean Sea, or the North Sea. It likely arrived attached to the hull or taken up in the ballast water of a ship – these are both common ways that invertebrate species are unintentionally introduced to new environments.
The term invasive also implies that the species has established itself, integrated into the local ecosystem, and spread. Invasive species often have a negative effect on native species, but not always – the interaction can be more complicated. For example, if an invasive species has a negative effect on native species A, and species A has a negative effect on species B, then the invasive species could have an indirect positive effect on species B. Fascinating, right?
To see if anything similar was happening at the Yacht Club, we counted the number of tunicates per one meter transect as well as the number of other species in the same area. Unfortunately, the results are not in yet, but they could be very interesting. Stay tuned! The results could be posted soon!
Trivia of the day: what type of invertebrate is this?
Interesting links if you want to learn more about tunicates: