AWA: Academic Writing at Auckland

Antarctica is a pristine environment that has been geographically and climatically isolated for millions of years (Smith et al., 2012). The Antarctic Convergence – which circles continental and maritime Antarctica – is a region about 45 km long where the surface temperature drops 2-3á´¼C moving south, creating a barrier that isolates Antarctic biota (Molina-Montenegro et al., 2012). This barrier has allowed unique organisms in Antarctica to form almost completely independent of other locations around the globe, resulting in carefully balanced relationships between the Antarctic biota (Smith et al., 2012). The delicacy of these relationships means invasive species – introduced species that have the potential to adversely affect the habitats and ecosystems of a region (Smith et al., 2012) – could have grave impacts in Antarctica (Chwedorzewska et al., 2013). The establishment of invasive species by human activity is a severe threat to Antarctic biodiversity, and a warming climate is increasing the feasibility of foreign biota surviving in the region (Cowan et al., 2011; Tsujimoto & Imura, 2012). Invasive species are already displacing endemic biota in the sub-Antarctic, while maritime and continental Antarctica are starting to experience similar challenges (Volonterio et al., 2013). This suggests geographic and climatic isolation are no longer such strong barriers to invasion (Fox, 2012). Understanding the mechanisms by which invasive species are introduced to Antarctica, and the effect such species could have on Antarctic ecosystems, is essential in order to protect the extraordinary biota of Antarctica.

Recent human activity has significantly increased the risk of invasive species being introduced to Antarctica (Volonterio et al., 2013). These activities are predominantly fishing, tourism and research (Volonterio et al., 2013). Intentional introductions for research can be easier to manage, whereas unintentional introductions on cargo, footwear, food and scientific equipment are more difficult to monitor and control (Volonterio et al., 2013). Water containing invasive species or propagules get trapped in ship bilges organisms, micro-organisms survive easily on food supplies, and dirty footwear readily transports a variety of life forms – showing there are many ways that human activity facilities introduction of invasive species (Volonterio et al., 2013). The accidental introduction of the harmful crop annual bluegrass (Poa annua) to the Antarctic Peninsula is a prime example: all annual bluegrass found was located near research stations or in correlation with transport routes – as shown in Figure 1 – supporting the hypothesis that human activity is a major contributor towards the introduction and persistence of invasive species (Molina-Montenegro et al., 2012). As this relationship between human activities and invasive species is mirrored throughout Antarctica (Molina-Montenegro et al., 2012) there needs to be strict enforcement of the rules in place to minimise human-assisted arrival. Despite the increased risk of introduction, many invasive species that are introduced are unable to survive Antarctica’s cold climate (Chwedorzewska et al., 2013), yet this creates concern if the temperature barrier is removed.

Figure 1: Occurrence of annual bluegrass on and near the Antarctic Peninsula prior to 2007 (circles) and from 2007 onwards (stars) in relation to 4 main maritime transport routes, with percentages showing the frequency of travel for each route (Molina-Montenegro et al., 2012).

Unfortunately, a warming global climate is concurrently increasing the likelihood of invasive species surviving in Antarctica (Chwedorzewska et al., 2013). The warming climate not only changes the temperature on the Antarctic continent, but also changes the temperature in the Southern Ocean – warmer water has moved towards the continent, altering the ecological balance in the water surrounding Antarctica (Fox, 2012). Lifting the climatic barrier from the continent and surrounding water means species that are able to cope with warmer temperatures can now survive in Antarctica (Fox, 2012). The king crab Neolithodes yaldwyni is one example of a species that has taken advantage of the temperature barrier removal (Fox, 2012). The invasive crab has been found decimating benthic communities in Palmer’s deep, near the Antarctic Peninsula (Fox, 2012). It is therefore evident that the warming climate is having a significant impact on the ability for invasive species to establish in Antarctica. Coupled with human activity, the removal of the temperature barrier – and the subsequent arrival of invasive species – poses a huge threat to Antarctica’s biota (Chwedorzewska et al., 2013).

Invasive species could have a wide array of impacts on Antarctic ecosystems. Until recently, Antarctica had been isolated for about 40 million years (Smith et al., 2012). In order to cope with the cold climate, Antarctic organisms evolved a slower pace of life (Fox, 2012). The limited number of species in Antarctica meant the ecosystems which developed were relatively simple, making Antarctic ecosystems significantly more vulnerable to invasive species (Chwedorzewska et al., 2013). The specificity of the biota due to its prolonged isolation from the rest of the world means that Antarctic ecosystems have a limited ability to cope with invasive pressures (Chwedorzewska et al., 2013). Evidence of this struggle is seen in the aforementioned impact of king crabs on benthic brittle stars (Ophionotus victoriae) and clams (Laternula elliptica) (Fox, 2012). The native brittle stars and clams never had to cope with predators capable of crushing hard shells, and as a result only have soft shells (Fox, 2012). Sadly, this has allowed the hard shell-crushing king crabs to easily destroy brittle star and clam populations (Fox, 2012). Similar struggles to cope with invasive species are evident around Antarctica, showing the severe threat invasive species pose to endemic biota (Chwedorzewska et al., 2013). Antarctic clams and brittle stars play an important role in the ecosystem, as they feed on decaying plankton to make this energy available to others in the benthic community (Chwedorzewska et al., 2013). The presence of king crabs is coupled with a complete absence of brittle stars, an overall reduction in faunal diversity and distorted ecosystem function (Smith et al., 2012), stressing that removing vital energy links can have disastrous effects on ecosystems. Still, predators are not the only invasive threats to Antarctic ecosystems. Invasive microorganisms pose a huge threat to indigenous bird life by spreading infectious diseases (Cowan et al., 2011); other seemingly harmless invasive species increase competition for vital resources (Chwedorzewska et al., 2013); and even the movements and behaviours of invaders can alter the biochemistry of the region. The importance of these threats can be illustrated by noting that the king crabs further changed benthic biodiversity by disrupting the sediments while walking and foraging (Smith et al., 2012), or that the rate of photosynthesis for native plants declines when near invasive annual bluegrass (Molina-Montenegro et al., 2012). Parallels can be drawn between these examples and the other Antarctic species and ecosystems; even a small change in a single species could have severe impacts on Antarctic ecosystems and food webs due to the simplicity of the relationships between organisms and their reliance on particular species as energy resources (Chwedorzewska et al., 2013). Removing one crucial link could essentially collapse entire Antarctic ecosystems (Smith et al., 2012). However, even more concerning is the wider implications of altering Antarctic ecosystems. The Southern Ocean plays a vital role in removing CO₂ from the atmosphere (Smith et al., 2012). Disrupting the fragile balance of an Antarctic ecosystem may change the ecology of the Southern Ocean, altering the rate of CO₂ removal (Smith et al., 2012). As CO₂ contributes to global warming, destroying such Antarctic ecosystems could increase global temperatures, threatening life the world over (Smith et al., 2012). As other equally disastrous results could arise from changes in Antarctic ecosystems, it is of utmost importance for immediate action to be taken to minimise the impact that invasive species in Antarctica could have on the world.

As the only remaining continent that has been largely unchanged by humans, the Antarctic environment needs protection from invasive species due to the devastation these species may cause to endemic flora and fauna. Invasive species pose a huge threat to Antarctic ecosystems, with equally concerning global implications, and much is yet to be discovered about Antarctic communities and their large-scale importance (Ruzicka et al., 2013). Regrettably, this makes it difficult to predict the implications invasive species could have worldwide, meaning the effects of invasive species in Antarctica may only be noticed once the changes are irreversible (le Roux et al., 2013). Thus strict regulations, persistent monitoring for new species and eradication programmes are essential to preserving Antarctic biota. The largest remaining barrier protecting the continent from invasive species is time; hence action must be taken now.