Entanglement

So far, my blog has mentioned the impacts that humans are having on a number of Antarctic species such as krill and Gentoo and Adélie penguins. Today's post will look at yet another animal whose habitat is in Antarctica, the fur seal. Croxall et al. (1990) conducted research investigating how fur seals are becoming entangled by various man-made products that are roaming the oceans near Antarctica. Figure 1 shows what I mean by entanglement. It is when the fur seal gets caught up in man-made materials that are non-biodegradable, such as polypropylene or nylon string and fishing nets. Fur seals become entangled by putting their heading into the loops of material in the ocean while swimming. 

Figure 1. Entangled Antarctic fur seal

Antarctic fur seals are commonly found in the South Georgia and the South Sandwich Islands (see figure 2) and this is where Croxall et al. focus their study. The authors reported observations of fur seals that had man-made objects around the seals’ necks (referred to as neck collars) for 142 days at Bird Island (as shown in figure 2) from 1988 to 1989.

Figure 2: South Georgia and the South Sandwich Islands. Adapted from Cool Antarctica (2001) and Wikitravel (2011)

This study helped identify the extent of entanglement in South Georgia. Here is a summary of the main findings of the research:

• At least 0.1% of the total Bird Island population had a neck collar during the study period, of which 59% was due to packaging bands made from polypropylene straps, 16% was due to nylon strings and 13% was due to fishing nets.
• Males accounted for 71% of entanglements and young accounted for 88% of entanglements.
• 135 males and 55 females were observed to be entangled.
• 19% of the collars were loose enough to remove.

The table below, table 1, also shows the results.

Table 1. Observed Antarctic fur seals with entanglements at Bird Island and the type of collar. Source: Croxall et al. (1990)

There are some inadequacies in this research however. The authors claim that '15 were most probably of animals seen more than once or whose collars were subsequently removed’ (p. 223) so they did not count these in the results. Hence the total number of fur seal included in their results (i.e. the minimum number observed) is 208, not 223 (see table 1). I find this problematic because how can the authors be certain that a fur seal was observed more than once? The authors don’t mention that they were tagged or tracked in any way and due to the homogenous characteristics if fur seals, perhaps there is measurement error in the observations.  

Also, there are complications in measuring the exact proportion of the total population that is affected because the whole population is not observed. Many young don’t appear ashore and they could have neck collars. A further consideration is what about the fur seals that are entangled in the sea and don’t make it back to the island? Antarctic fur seals can go weeks in the oceans (National Geographic, 2014) so these seals are not observed. Hence, this sample is too small to infer the full extent of the total fur seal population affected by man-made debris.

Despite this, this research has shown that humans are involved in the entanglement of fur seals. Man-made debris is floating around in the waters surrounding Antarctica, causing danger to the Antarctic fur seal (see figure 1). Despite no permanent residents in Antarctica and despite its isolation from the rest of the world, man-made plastics, strings and ropes are still present in this environment. 

Where is it coming from?

The debris, i.e. nylon ropes, packaging plastic bands and rubber rings, comes mostly from fishing activities (Ivar do Sul et al. 2011). Other studies have found entangled seals in Signy Island, which is part of South Orkney Islands (Dunn and Waluda, 2008), and Marion Island, which is in the Southern Ocean (Hofmeyr et al. 2002). Both these studies concluded that entanglement is linked with fishing activities. The fishing industry is motivated by profit making which stems from the western capitalist society. The use of these materials is an efficient way to maximise catch and minimise costs, but fishing companies are less concerned about the effects of disposing ropes and nets into the sea.

Effects

Finally, what are the effects of entanglement? Although it might seem obvious, there are indirect impacts that surprised me. Below is a summary of the impacts of entanglement on fur seals (Hofmeyr et al., 2002 unless stated otherwise):

• Individual suffering
• Restriction of movement
• Drowning
• Strangulation
• Infection (even if the plastic collar is removed, the open wound can cause infection)
• Inability to protect itself from predators
• Starvation due to reduced ability to catch prey
• Female fur seals spend longer at sea than seals that are not entangled. This means they leave their pups unprotected for longer, making them more likely to die (Croxall et al. 1990)

Sum up

The idea that Antarctica would be excluded from human impact forever is deluded. Despite its isolation from the rest of the world, it seems that human impact is reaching a truly global scale. Antarctic oceans are being polluted by plastics and other man-made debris which is affecting Antarctic fur seals. What I want to demonstrate from this post is that man-made debris is inescapable wherever you go and Antarctic wildlife is bearing the brunt.

My next topic is scientific research. Are sites of scientific research doing more harm than good? One of the major concerns about research centres in Antarctica is waste disposal, so this topic follows on well from this post. The scores for negative human impacts verses positive/ natural impacts on Antarctica are 5-3.

Thanks for reading!

How Krill Variability Affects Penguins

This post will focus on how krill variability in the West Antarctic Peninsula (WAP) and Scotia Sea affects populations of Adélie and chinstrap penguins via the food chain.

Whaling

As mentioned in my previous post, krill fishing has become one of the main drivers reducing krill population and increasing competition for krill. But this is not the only impact that humans have had on krill population. Indirectly, through the introduction of whaling and sealing restrictions, competition for krill is increasing, causing stress among krill population. In turn, this is causing a decline in the populations of Adélie and chinstrap penguins.

For example, the International Whaling Commission banned the whaling of blue whales in 1966 (National Oceanic and Atmospheric Administration Fisheries, 2014) which is increasing the population of baleen whales (blue whales are a type of baleen whale) and therefore increasing demand for krill. This reduces available krill to penguins, particularly because blue whales’ diets consist mostly of krill (ibid). More competition for krill means that krill populations may decline even further than they have. Trivelpiece et al. (2011)'s research project in the South Shetland Islands in the West Antarctic Peninsula (see figure 1) discovered that Adélie and chinstrap penguin populations have declined more than 50% in the last 30 years, which is approximately during the same time that whaling bans were introduced in the Antarctic. 

Figure 1. Map showing the South Shetland Islands and the West Antarctic Peninsula. Source: Lenfest Ocean Program, (2011)

This suggests that humans have indirectly affected penguin populations via the food chain and the impact on krill population. Whaling bans therefore have a positive impact on whale populations, but a potentially negative impact on penguin populations. The fact that this happens demonstrates the interconnectedness of Antarctic wildlife and the importance of krill in the food chain. It also highlights the complexity of food chains. Food chain processes are natural and once humans alter these mechanisms, many species, not just one, are affected. Even if humans have good intentions (e.g. to protect whales), there can be negative indirect effects as well. 

Trivelpiece et al. (2011) further mention that the effect of a reduction in krill availability for penguins is predicted to increase as krill fishing increases. Humans, therefore, have a variety of impacts on whale, penguin and krill populations and these impacts are all holistic. The impact that humans have had on Antarctica is both positive (on whales) and negative (for penguins and krill). Because of this, I will classify the total impact as neutral, so for the first time in my blog, the impacts cancel out and the scores remain unchanged! Just to remind you, they stand at negative impacts 4, positive/ natural impacts, 2.

Next week I will explore an argument against anthropogenic causes, focussing on how natural climate variability can cause changes in krill population. Thanks for reading!

License to Krill I

Krill are small crustaceans that resemble shrimp and feed of diatoms. They are very abundant in Antarctica, in fact their total global combined weight ranges from 500 to 700 million tonnes (Voytek,1990)! Krill are small creatures as demonstrated by figure 1, which shows their size relative to a paper clip. Despite how small they are, they are essential for life in Antarctica. According to the National Geographic (2014), 'without krill, most of the life forms in the Antarctic would disappear'.

Figure 1. Size of krill relative to a paperclip. Source: The National Geographic (2014)

Why are krill so important?

Krill play an important role in the Antarctic food chain. Krill are at the bottom of the food chain which means that they are important food sources for whales, penguins, seals, fish, copepods and sea birds (Tomaselli, 2012). These animals make up the majority of those found in Antarctica. Because so many animals rely on krill, a change in krill availability may result in starvations among some of these Antarctic animals.

Figure 2 shows which animals feed on krill. Krill are consumed by Emperor penguins, Adélie penguins, crabeater seals, leopard seals, and baleen whales. It’s important to note that the figure does not show all of the animals feeding on krill, only a selection.

Figure 2: Antarctic food chain. Source: Voytek (1990)

Krill population

Given the importance of Antarctic krill in maintaining populations of marine and terrestrial animals, it is desirable to keep krill populations steady. But this not the case. In fact, humans are reducing the levels of krill in Antarctica, both directly and indirectly.

First I’ll explain the direct impacts on krill population. Krill populations are declining due to fishing. The Soviet Union began fishing Antarctic krill in the early 1960s (Aronson et al. 2011). In the 1970s and 1980s, many other countries followed (ibid). Krill are sought after because they are used as fish bait, fish feed in aquaculture and for aquarium trade (ibid). Furthermore, krill can be transformed into krill oil, which is a source of omega-3 and can have beneficial health impacts for us. Krill oil can help protect us against and lower the risk of suffering from health conditions such as rheumatoid arthritis, heart disease, stroke, depression and osteoporosis (University of Maryland Medical Center, 2013; accessed 28 November 2014).

These health benefits incentivise pharmaceutical companies to fish Antarctic krill because there is a market for krill oil products. Below is a video published on YouTube by the pharmaceutical company, BioCeuticals, which catches krill to turn into krill oil. I've posted this video because it gives you a flavour of the use of krill to humans.

What is interesting to note about this video is the way the company justifies its activities. Phrases like “krill is found in great abundance all around the Antarctic continent” and "the estimated biomass of Antarctic krill is twice the biomass of the worldwide human population"  indicates that krill are plentiful anyway so fishing would not create any disastrous ecological impacts. Also, the fact that the company interviewed a WWF Director demonstrates that they care about krill levels in Antarctica and want to engage in fishing in a sustainable manner.

Despite what this company claims about sustainable fishing, Antarctic krill populations have been declining. Figure 3a shows this steady decline. Even though there have been fluctuations since the 1970s, the general trend is a decrease in krill. Figure 3b shows where the krill populations have been declining and to what extent. In figure 3b, the red area indicates where the largest declines have occurred, which has been in the North. This region also happens to be the most accessible for ships because it is close to Argentina, making visits likely. As the video above showed, large ships travel to Antarctica to catch krill and turn them into oil almost immediately (while on the ship).

Figure 3. Krill population decline. 
a) Krill density in Antarctica from 1976 to 2000
b) Krill density across Antarctica
Source: Atkinson et al.(2004)

Indirectly, humans are having an impact on krill populations via climate change. Climate change is causing an increase in sea surface temperatures which is affecting the spawning and nursery areas of krill (Atkinson et al. 2004). According to Hill et al. (2013), sea surface temperatures have been increasing by 0.2^oC every ten years, but this is predicted to increase to warming of between 0.27^oC and 1.08 ^oC by the end of this century. Warmer sea temperatures are causing reduced sea ice extent which is problematic for krill because sea ice forms a large part of krill’s habitat. Atkinson et al. (2004) explains that sea ice also shields krill from predators and fosters sea algae, which are a key food source for krill. Additionally, climate change is exacerbating the destruction of their habitat because winter sea ice duration is reducing due to warmer temperatures and warmer oceans, thus humans are indirectly having a negative impact on krill.

So in this post, hopefully my readers have understood the importance of krill for Antarctic animals that feed on krill and have realised what negative impacts we are having on them, both directly and indirectly. The new scores are negative impacts 4, natural/positive impacts 2. Next week, I will discuss another indirect effect that humans have had on krill population.