Marine Invasive Species and Their Impact on Global Biodiversity

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Marine alien invasive species are organisms introduced into a location that they have not been before, shifting the ecosystem and potentially disrupting the biodiversity and ecological niches of organisms already in the region. Some alien species can even have an impact on human health if they carry diseases. (Kernan, M 2015) Invasive species are recognised to be a major threat to biodiversity in the marine environment; however despite this very few global assessments of the impact and spread of these organisms have been produced. Therefore it may be difficult to provide a comprehensive view on the global scale impacts in this review.

What initial analyses do show is that 16% of marine ecosystems show no signs of marine invasions, (Molnar, Jennifer L. et al, 2008) although this figure could be even lower at present times. Of the 84% of regions the most common cause for the introduction of marine species is international shipping with the next major means being aquaculture. Those involved with the marine ecosystems are increasingly aware that the introduction of new alien species is a danger to marine biodiversity.

Whether these introductions are intentional or accidental many are due to human interference and many industries do not realise the impact they have on these systems. (Bax, N Williamson et al 2003) In this essay various academic journals and writings will be reviewed to assess the understanding and impacts of invasive species on marine biodiversity. The environmental impacts, socio-economic implications of the worst invasive species will be discussed as well as the reasons why and how many of these species are moved around the world. International and regional policies.

Alien Species Vectors

As stated in the introduction invasive species are introduced into an ecosystem, mostly by accident, from such things as a ship’s ballast. It is important to discuss how these alien species managed to become part of a marine region before looking at their impacts on the biodiversity of the region. It is thought that a large number of invasive species were introduced during the European voyages of discovery around the 1700s, a wooden ship in this age could have carried over 100 marine organisms on or boring into its hull. (Bax, N Williamson et al 2003) These organisms would either be left on the hull at its final destination or drop off as the ship stops introducing them into different environments. However marine invasions are still happening presently, at an increased rate due to the ever increasing amount of shipping (South, P et al, 2017). The use of anti-fouling paints (Such as the currently phasing out TBT) and higher velocities of newer ships may have had an effect on reducing hull fouling, however it does still happen, particularly with smaller boats (Bax, N Williamson et al 2003).

From tourist cruisers to fishing ships the introduction of new species to all parts of the globe is increasingly frequent, 10, 000 different species are moved to new regions in ballast tanks alone at any single moment. Over 50% of the known invasive marine species in Britain are due to shipping (Bax, N Williamson et al 2003). One of the more pressing concerns of recent years is the tourism trade, particularly in areas such as the Caribbean and Galapagos islands. These are areas of very specific and delicate ecosystems which are under much higher stress due to the increasing natural tourism trade. So as to combat the risks posed by invasive species, Ecuador’s Government in 1999 heavily restricted movement of goods and produce to the islands. Later, in 2007 and again in 2012, a management plan to reduce the amount of invasive alien species was created which resulted in the formation of a biosecurity team to prevent any additional introduction of invasive species as well as reduce the threats to biodiversity and the ecosystem from those already in the region. (Toral-Granda, M et al 2017

The green alga, Caulerpa taxifolia has been known to have the highest ecological impact due to it out competing many native species and dramatically reducing the overall biodiversity of regions it is has been introduced. (Molnar, J et al 2008) AquacultureIt is incredibly hard to remove an invasive species from marine environments once they have been established which is why aquaculture and proper biocontainment is so important (Molnar, J et al 2008). The world is becoming increasingly more reliant on aquaculture due to the increased demands for seafood, these fish stocks need to be kept away from indigenous populations so as to minimize interaction and potential negative ecological impacts (Noble, S et al 2017).

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Due to the increased demand for fish many farm raised fish are artificially propagated, meaning they possess desired traits to reach adult size faster and better resistance to disease. They may even have been genetically modified to increase their production efficiency. (Noble, S et al 2017). However it is important that these ‘improved’ organisms are carefully assessed and kept away from the natural ecosystem, as they may cause negative effects due to their increased resistances and growth rates (Jute, A et al 2017). Sandra Noble et al are researching a biocontainment strategy that involves inducing a dependency on a vitamin vital for a fish’s survival (such as thiamine). In an aquaculture laboratory fish with a thiaminase enzyme would receive a supplement containing thiamine, allowing those within the facility to survive. Any that escaped would lack thiamine and therefore die out. (Noble, S et al 2017) There are some invasive species such as the sea slug, Godiva quadricolor, which even when introduced to a new system accidentally have not had such a large impact as the lionfish. This is because they only feed on one taxon, being other sea slugs. Therefore the ecological impact is lower and is not such a threat to the biodiversity. (Molnar, J et al 2008) It is important for researchers to assess each individual species’ impact upon biodiversity.

Management of Invasive Species

Controlling and reducing populations of invasive species is a serious task and is needed to be done to effectively manage natural resources. Stakeholders, locals and researchers may have differing opinions about alien species and their value. (Bailey, S. , & Munawar, M. 2015) There are some alien species that may actually benefit the community or provide monetary value so are embraced by locals or shareholders. (Novoa, A. et al 2018) but are damaging on an ecological level and so are contentious and cause conflict. Some may call for lethal methods such as culling but others may find this cruel and unreasonable, therefore it is difficult to properly organise and find appropriate actions to manage the threat of invasive species successfully. To further complicate matters there is a no definite ownership of marine areas, this combined with the scale of the oceans and the lack of funding for marine conservation means the task is incredibly large.

Therefore the public may need to participate in order to effectively manage some marine environments. (Malpica-Cruz, L et al 2016)The lionfish is an invasive marine species that has been introduced in the Bahamas, which is a region of vulnerable reef ecology. Therefore fishermen and invasive organisms are construed as threats. In the Bahamas the lionfish has been incorporated into the fishing industry as a commercial edible fish in order to lessen the impact it may have had on the region as an invasive species. Furthermore it actually may help the biodiversity as the fisheries of the Bahamas are no longer over-fishing indigenous fish populations as much. (Moore, A. 2012) This use of public participation is one such example to create a sustainable ecosystem and reduce the threats of invasive species.

Lionfish derbies are another way in which citizens are able to help, participants in these tournaments attempt to catch the most or largest lionfish. (Malpica-Cruz, L et al 2016) If these derbies have any ecological benefits is currently debatable, more positively however they are increasing awareness of marine conservation and are engaging the public in activities that may provide data for research. If it is possible to understand why the tournaments are working so well it may lead to more events like these around the globe. (Malpica-Cruz, L et al 2016) A species that is incredibly damaging in both ecological and economic terms is the polychaete worm Sabella spallanzanii. Hypo-saline baths were used as a control method for the worm which are ecologically safe and cost-effective way to maintain vessels and marine structures.


The problem of alien species in marine environments is steadily growing and the environmental risks on marine biodiversity as well as humans on a socio-economic level is not being recognised at a level that is appropriate for the threat that they pose. Findings from various researchers and articles confirm that globally, shipping is the greatest vector for marine invasions followed by aquaculture. And although the main vector in shipping and ballast water is slowly becoming more widely recognised and addressed (with anti-fouling paints and such) there are many more vectors that are not being addressed appropriately.

Marine alien species can change the ecosystem and threaten the biodiversity. They are able to impact and affect many marine conservation efforts, usually negatively, and due to how widespread they can be invasions can also be irreversible. Marine invasive species are now a global problem, which requires local and regional as well as global solutions, which would need to address the significant environmental issues.

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