Invasive species are often defined
as those that are not native to the location they have been found in, possess the ability to spread, and typically adversely affect the local
populace, habitats and bioregions they have occupied. It must be noted that
invasive species are not to be confused with migratory species such as the
smooth hammerhead (Sphyrna zygaena) and other transient megafauna, no
matter how out of place they seem. Furthermore, it can be argued whether
‘invasive’ species present as a result of climate change driven range
extensions are truly invasive, or whether this is natural progression.
Despite the generally accepted definition,
non-indigenous species (NIS) can have a range of both detrimental and
advantageous ecological, environmental, economic and social impacts within our
waters. Nevertheless, it is still important to be able to identify these
species and their methods of transmission, to predict when and where instances
are likely to occur, and to try and devise appropriate mitigation and
management inline with guidance and legislation.
Although all invasive species can be a
cause for concern, marine NIS’ are particularly problematic. This is due to the
sheer size and scope of that big blue expanse, alongside all of the potential
methods of dispersal and evasion associated with the marine environment. Making
it difficult to control and eradicate established invasive species. Often such
species are found purely by chance especially for lesser known, inconspicuous,
or cryptic species which may be difficult to identify (i.e. those physically
adept at hiding and those currently yet to be identified by science due to
being hidden within other taxa etc.). The needle in a haystack analogy very much
applies in this context, except both are underwater and the needle may or may
not be able to swim or looks like hay.
All is not lost however, as established and
potentially invasive species have been documented within Ireland for decades. Many
of these have warranted a number of research papers, projects and initiatives
to be launched in tandem with legislation. All of which aims to aid and inform industry
and public awareness, engagement, monitoring and management.
Before identifying some of these marine
marauders and how they can end up on your local coastline, it is probably best
to outline the impacts they can have and how they generally can be bad news. Katsanevakis (2014
) highlighted some of the impacts
invasive species can have on biodiversity and marine ecosystem services previously
outlined by Liquete (2013). These can broadly be grouped as provisioning,
cultural and social, regulation and maintenance, and ecological impacts, but
are often interlinked. Figure 1 goes into greater depth as to the impacts
associated with invasive species, but generally negative impacts such as
interbreeding, outcompeting or predating upon native species and fish stock,
altering habitats to the detriment of native species, spreading disease, and
the ability to potentially injure humans predominate. For example, whilst
invasive sea squirts (i.e. Ascidiella aspersa
, Corella eumoyta
)
may have potentially beneficial applications in the production of natural
marine products, they have ultimately been shown to compete with farmed mussels
at Killary Fjord for food and space (Palanisamy et al.
, 2018).
Ultimately reducing mussel yields whilst simultaneously resulting in increased
maintenance costs, financially impacting the industry on multiple levels.
Now it is probably safe to say the vast majority of people are not
too interested in or worried about sea squirts unless they impact them
directly, after all there aren’t any films about them instilling the same sort
of fear in people as their toothy neighbours, with or without the addition of
extreme weather. However, there are sadly no confirmed species of invasive
shark or other large predatory fish to satiate you marine masochists out there,
but I can assure you the damage done by Irish NIS’ is no less horrifying… For
example, the round goby ( Neogobius melanostomous
) is a salt tolerant
species which can occupy both the marine and freshwater environment
(euryhaline), eating its way through native and invasive species alike and leaving
a trail of destruction in its wake. Other notable examples include, the rapa
whelk ( Rapana venosa
), American lobster ( Homarus americanus
),
blue crab ( Callinectes sapidus
), Pacific oyster ( Crassostrea gigas
),
acorn barnacle ( Austrominius modestus
), orange ripple bryozoan ( Schizoporella
japonica
), and Japanese wireweed ( Sargassum muticum
), for much the
same reasons as any other invasive species (Allen et al.
, 2006., Kraan,
2008., Gallardo and Aldridge, 2013., Loxton et al.
, 2017. – figure 2).
So how are species from say Australia, Asia
or the Americas getting to Ireland, and what is being done about it? The answer
is simply any way they can. Be this on the surfaces of recreational or
transportation vessels, on migratory species, in ballast water, within food shipments,
and as a result of the exotic pet trade just to name a few confirmed invasive
vectors. Tidbury (2016) used information concerning aquaculture, shipping and
recreational boating to identify areas around Ireland and the rest of the
British Isles most likely to be sites of invasions, testing predictions
utilising established populations of the invasive carpet sea squirt ( Didemnum
vexillum
). It was shown that areas most at risk included those surrounding
Belfast, Cork, Derry, Dublin, Galway and Westport, largely due to aquaculture,
fisheries, shipping and recreational boating being concentrated in those areas
(Figure 3).
Such studies are crucial to the management
of invasive species, as predicting where they are most likely to occur can
focus monitoring and management efforts in order to comply with legislation. Ireland
is subject to International, European, and Irish legislation concerning
invasive species, which includes EU Invasive Alien Species Regulation
(1143/2014) and Irelands National Biodiversity Action Plan. All in all, these
state that potentially harmful invasive species are to be identified, reported,
monitored, controlled, contained and or eradicated when feasible, all whilst
promoting native species. Naturally the exact methods vary between species and
locations, but generally involve early detection and prevention, manual control
(i.e. physical removal), chemical control (i.e. pesticides), competition (i.e.
reintroduce native species once NIS are removed), and biological control (i.e.
introduce natural predators) in succession. However, the stages after manual
control can have significant limitations and detrimental impacts within the
marine environment. For example, introduced predators are potentially invasive
themselves and may also consume indigenous species.
If
wanting to find out more about invasive species in Ireland, ways to get
involved, or projects such as the European funded ‘Mapping Irelands invasive
species project (2020 – 2021)’, please visit invasivespeciesireland.com
,
biodiversityireland.ie
,
nonnativespecies.ie
,
or
msp-platform.eu.
© Ocean Research & Conservation Ireland (ORCireland) and
www.orcireland.ie
, est. 2017. If you like our blogs on the latest news in marine science and would like to support our work, visit www.orcireland.ie
to become a member, to volunteer or to make a donation today. This article has been composed based on credible sources.
References:
Allen, B.M., Power,
A.M., O’Riordan, R.M., Myers, A.A., and McGrath, D., (2006). INCREASES IN THE
ABUNDANCE OF THE INVASIVE BARNACLE ELMINIUS MODESTUS
DARWIN IN IRELAND. Biology and Environment: Proceedings of the
Royal Irish Academy.
106 (2):
155 – 161.
Gallardo, B.,
and Aldridge, D.C. (2013). The ‘dirty
dozen’: socio-economic factors amplify the invasion potential of 12 high-risk
aquatic invasive species in Great Britain and Ireland. Journal of Applied
Ecology.
50:
757 – 766.
Katsanevakis,
S., Wallentinus, I., Zenetos, A., Leppäkoski, E.,
Çinar, M.E., Oztürk, B., Grabowski, M., Golani, D., and Cardoso, A.C. (2014). Impacts
of invasive alien marine species on ecosystem services and biodiversity: a
pan-European review. Aquatic Invasions.
9 (4):
391 – 423.
Kraan, S.
(2008). Sargassum muticum
(Yendo)
Fensholt in Ireland: an invasive species on the move. Journal of Applied
Phycology.
20:
823 – 832.
Liquete, C.,
Piroddi, C., Drakou, E.G., Gurney, L., Katsanevakis, S., Charef, A., and Egoh,
B. (2013). Current status and future prospects for the assessment of marine and
coastal ecosystem services: a systematic review. PLoS ONE
. 8(7):
1
– 15.
Loxton, J.,
Wood, C.A., Bishop, J.D.D., Porter, J.S., Spencer Jones, M., and Nall, C.R. (2017).
Distribution of the invasive bryozoan Schizoporella japonica
in Great
Britain and Ireland and a review of its European distribution. Biological
Invasions.
19:
2225 – 2235.
Palanisamy,
S.K., Thomas, O.P., and McCormack, G.P. (2018). Bio-invasive Ascidians in
Ireland: A Threat for the Shellfish Industry but Also a Source of High Added
Value Products. Bioengineered
. 9 (1):
55 – 60.
Tidbury, H.J.,
Taylor, N.G.H., Copp, G.H., Garnacho, E., and Stebbing, P.D. (2016). Predicting
and mapping the risk of introduction of marine non-indigenous species into
Great Britain and Ireland. Biological Invasions.
18:
3277 – 3292.
