Continuing
with examples of Newfoundland invasive species we are going to switch to a
marine example and talk about the Golden Star Tunicate, also known as Botryllus schlosseri (see below in Figure
1). We are going to talk about its biology, distribution, impacts and
management strategies put forth.
This organism is a filter
feeder, therefore it eats organic matter moving within the water column. They
are physically different from other tunicates due to their star like shape and
they thrive in ocean water with temperatures between 6° C to 12 C°, ideal for the
Newfoundland population (Epelbaum, 2000).
Figure 1: Different
coloured Golden Star Tunicates growing over mussels on the sea floor (DFO,
2011)
As you can see below, the
golden star tunicate is making its way to the Placentia Bay and Fortune Bay
regions of Newfoundland, and has been on the island’s west coast since at least
the mid 1970s due to fishing and exportation of goods by boats.
Figure 2:
Distribution of Golden Star Tunicates within Newfoundland forcusing on the main
population in Placentia Bay (DFO, 2011)
The origin of it the golden star tunicate:
Golden
star tunicates are native to Europe but due to their abilities to exploit new
habitats and with increased boat travel, they have now become one of the most
common tunicates in North America, and without being properly managed, will
likely affect most of coastal Newfoundland and Labrador. They are naturally
maintained within Norway due to the natural distribution of predators, as
listed above. 5
The discovery of it within Newfoundland is:
First
seen in Bonne Bay in 1975 and has spread to many other bays around the coast. More
recently, and more alarming, it has been quickly increasing its presence in the
Fortune Bay and Placentia Bay regions. It has yet to make its way into mussel
farms but with increasing temperatures, it has the potential to greatly hinder
the industry1.
Important things to learn about the golden star
tunicate that make them a problem:
Golden
star tunicates are spreading very quickly and form dense populations, making it
difficult for native species to compete for food. They can grow over many
surfaces, including rocks, ships and non-moving organisms. This can potentially
cause serious damage to aquaculture, ships’ hulls (and other infrastructure)
and an areas biodiversity. If space is limited they will form folds on top of
each other to increase abundance. They can reproduce asexually (without a
mate), by budding from broken pieces or sexually by production of eggs which
hatch as free-swimming larvae. The free-swimming larvae can travel up to 2 days
before settling at the bottom, meaning they have great potential to spread over
the province and cause even greater problems2.
Why it matters:
They filter feed on plankton
and when they are really abundant they remove an important food source for the
area. They have the potential to remove the bottom level of food in the area
and are not themselves fed upon because they have no natural predators. This
creates a struggle for the native species of the area and can rob
Newfoundland’s coastline of its traditional nature and maybe even economic
value. In Newfoundland this hurts a lot of mussel and scallop farming because
they are both filter feeders and this decreases the amount of food available to
the aquaculture4. Tunicates also like to grow over slow moving
organisms; covering plants such as algae, and slow moving animals (mussels,
clams, corals etc…) which may suffocate them or block out available sunlight or
nutrients. Therefore they can endanger some of the province’s natural
populations2.
Newfoundland Management:
Create awareness to fishermen
and get them to clean their nets and other gear before use in to prevent spread
of new colonies. Regularly clean boats, they often attach themselves to the
underside of boats and ships, and can easily be spread across regions. Learn
about reproduction times and numbers, done currently by Memorial University of
Newfoundland and Fisheries and Oceans Canada in Arnold's Cove, NL1.
For
more information on the impacts (environmentally and economically) please
visit: http://publications.gc.ca/collections/collection_2007/dfo-mpo/Fs97-4-2747E.pdf.
Management Abroad:
In
Alaska and along the USA’s eastern seaboard, golden star tunicates have been a
major problem as well. Their management for the issue entails an increase in
monitoring, research, outreach and public action, which is quite similar to our
own. However they have begun exploring the affects of cellulose based
pesticides on golden star tunicates. Also considered is controlling them with
UV light or desiccation, under water hydraulic pressure or removal by hand6.
Conclusion:
The golden star tunicates
surely pose a potential threat to the current state and biodiversity to the
coastal waters. Management efforts are still in the preliminary stages,
considering this species has only been taken seriously as an invader for about
half a decade. That being said, there is ambitious research currently to help
shine some light on how to better deal with them and there has been public
outreach to help reduce its spread. Newfoundland’s initiative is a definitely
behind that of the USA’s, but keep in mind, the problem is much newer here.
References:
1Carver, C. Mallet, A. and Vercaemer, B. 2006.
Biological Synopsis of the Colonial Tunicates. Fisheries and Oceans Canada. Canadian Manuscript
Report of Fisheries and Aquatic Sciences. No. 2742. Retrieved from: http://publications.gc.ca/collections/collection_2007/dfo-mpo/Fs97-4-2747E.pdf
2Callahan, A. G., Deibel, D., Hall, J., Rise, M. and
McKenzie, C. H. (2010). Determination of Cytochrome c Oxidase gene sequences of indigenous and
non-indigenous ascidian tunicates of Newfoundland. Aquatic Invasions.
5 (1): pp. 31-39.
3Epelbaum,
A.2000. Aquatic Invasive Species: Identification Booklet. Golden Star Tunicate
locate on pp 16-19. Retrieved from: http://www.qc.dfompo.gc.ca/publications/envahissantinvasive/carnet_en_final.pdf
4Sephton, D., Vercaemer, B., Nicolas, J. M. and Keay,
J. (2011). Monitoring for invasive tunicates in Nova Scotia, Canada (2006-2009). Aquatic Invasions. 6 (4): pp. 391-403.
5Aquatic species descriptions: Golden Star Tunicate.
Page 4-5. Retrieved from: http://l.b5z.net/i/u/6058300/f/Invasive_species_Fish__Birds__other_Animals.pdf
6Annual Report to the Puget Sound Partnership for the Invasive
Species Tunicate Response. (2008). Tunicate Annual Report. Retrieved from: http://wdfw.wa.gov/publications/00804/wdfw00804.pdf
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