The Centre of the Universe... and us

Contrary to popular belief, we humans are not the centre of the universe. In fact, on a planet that is over 4 billion years old, and home to more than 8 million species, to say we are the centre of Earth alone would be a bit of a stretch too. As the timeline in Figure 1 shows, our existence on Earth represents a rather insignificant proportion of its history. However, this does not mean our effect on it will be insignificant. Evidence for the considerable effect that humans are having on the Earth is there for all to see, and as per my blog topic, we will be looking at this influence relative to the oceans. In my 'Waste by the Ocean' post, I spoke about how our waste can come back around to bite us - perhaps a rather egocentric approach. Therefore, I will now look in more detail at how it effects the Earth and everything else on it.



Figure 1: a timeline of Earth's history (Source)

Us humans represent but a small percentage of life on Earth, so it is important to consider how our actions influence what's around us. One way in which our waste can affect marine life involves entanglement in debris. This debris can then lead to death in various ways including drowning, strangulation, and starvation by inhibiting ability to feed. Studies on Australian fur seals at Seal Rock have estimated that in this particular location over 300 seals become entangled in marine debris every year. There are repercussions of this, as other observed seal populations have shown, where almost one third of entangled seals have displayed visible injuries. Furthermore, only 19% of these seals were tangled in collars that were loose enough to be removed. 

Marine mammals are not the only sufferers though, as bird populations can also experience problems related to entanglement. A study in Wales on a Gannet population revealed how the seabirds often use marine debris when making nests. An estimated 18 tonnes of debris has been used for nest building across the colony under investigation. This in turn increases risks associated with entanglement, which can lead to high mortality rates. The effects of this are not thought to have population-level impacts, though this is not believed to be a particularly well understood aspect and warrants further enquiry. This is due to the fact that deaths via entanglement in seabird populations can often be isolated, or even go unnoticed due to the interference of factors such as sinking and predation.

The other major influence on marine life from ocean waste is ingestion, and various studies such as that on fish species by the Spanish Coast have proven this to occur. In this instance, almost 20% of fish under investigation were found to have consumed microplastics. One problem of this consumption relates to possibly harmful chemicals on the plastics. Despite bans on the use of toxic substances such as PCB's (polychlorinated biphenyls) in agriculture, the chemicals themselves still exist in our environment today. These PCB's attach themselves to microplastics; Andrady (2015) proposes this as a likely method by which toxins might be transferred across organisms after ingestion of the plastics. Further evidence suggests that microplastic ingestion is positively correlated with PCB concentration. However, it is important to note that the possible transfer of toxins in this way, and subsequent effect, is a relatively understudied phenomenon. 

There are various ways in which plastics might be mistakenly ingested, one example is exactly that, a mistake, perhaps birds thinking it is their prey. Other ways include microplastics attaching themselves to seaweed, where they are then consumed by herbivores. However, once ingested, the danger of harmful chemicals is not the only threat to wildlife. Taylor et al. (2016) suggest that one danger of ingesting plastics involves the damaging of the stomach lining, which in turn can cause starvation. Other ways in which organisms can starve include blockage of the digestive tract by larger debris. Figure 2 shows the plastic debris found inside a sperm whale, after it died from starvation, thought to be due to gastric blockage. Included in the findings were large items such as flower pots and hose pipes.

Figure 2: plastic debris found inside deceased sperm whale (Source)

If nothing else, one thing this does show is that we live in a world where our mere waste has the ability to impact life. With our rapidly growing technologies and population, we are developing a power over the environment incomparable to that which we have ever previously held. So onto a cheesy quote; "with great power comes great responsibility". I first heard this in Spiderman, but the likes of Winston Churchill have uttered words similar. This is to say that our actions have consequences, which can sometimes be severe. However, as Figure 1 showed, we have only been on Earth for the 'blink of an eye', so to be able to render the planet inhospitable to ourselves, and others, within that time would be much more than just a terrible shame. We are therefore lucky to have the science available now to show us what we do wrong, so that next time we might do it right.

My next post will move away from plastics to look in more detail at the chemical waste going into our oceans, and what effect this is having. Then, following that, I will start looking at the solutions that are in place to address marine pollution. Much of this blog so far has been a bit doom and gloom with regard to the damage we are causing our oceans. However, it is important to acknowledge when positive progress is being made, which it is, and we'll have a look this later down the line.