31/10/2014

Sea turtle tumors linked to pollution

I'd like to bring your attention to a paper I stumbled upon recently linking pollution to tumors in sea turtles (Van Houtan et al. 2014) - it's Halloween after all, and this is pretty scary stuff.

It appears that eutrophication - a type of aquatic pollution - has been associated with fibropapillomatosis (FP), a disease that triggers the formation of tumors in sea turtles around the world [Figure 1.].


Figure 1. Green turtle riddled with fibropapillomatosis (Van Houtan et al. 2014)

First, some background info on FP: Previous research on the disease by Lackovich et al. (1999) had revealed the presence of DNA from α-herpesviruses in FP-affected tissue. Because the herpes DNA was not found in the surrounding healthy tissue, researchers suggested the disease to have a viral origin. However, further studies showed  that the viruses were found in every turtle tested, whether healthy or otherwise, indicating that the viruses are dormant and require a certain trigger to promote the formation of FP tumors (Alfaro-Núñez and Gilbert 2014).

The new study is a follow up investigation from a 2010 paper that revealed FP to be more prevalent in areas with high levels of nitrogen runoff (Van Houtan et al. 2010). At the time, the authors hypothesised it could have something to do with how the algae the turtles eat store the excess nitrogen.

The researchers decided to test the amino acid profiles of green turtles, as well as those from a range of native and non-native algae found in both eutrophic and oligotrophic sites off Hawaii. Arginine, an amino acid known to play a role in "cell inflammation and immune dysfunction, and in promoting viral tumors" was specifically tested for in the algae. The results showed that arginine levels were elevated in eutrophic sites in all the algal species, and that the invasive species Hypnea musciformis showed especially high levels of arginine compared to the other species in both eutrophic and oligotrophic sites [Figure 2.] (Van Houtan et al. 2014).

Figure 2. Arginine levels in three non-native species and the native Rhodophyta in eutrophic (Hi) and oligotrophic (Lo) sites; note the high levels of arginine in H. musciformis in both sites compared to other algal species (Van Houtan et al. 2014)


The authors proposed that the excess environmental nitrogen from anthropogenic nutrient pollution is stored preferentially as arginine by the algae, which are then consumed by the turtles. Significantly, the aforementioned trigger required by the α-herpesviruses to rise from their dormant state is in fact arginine.

Moreover, H. musciformis grows more readily than the native species and thus the turtles are more likely to consume it, indicating it could potentially make up a huge propertion of the turtles' diet. It is also energy-poor compared to the native species so the turtles have to eat twice as much of it to get the same amount of energy from it.

So not only are the turtles eating arginine-rich algae, they are also consuming it in huge quantities. All this from nutrient pollution!!

The study highlights two important environmental issues - eutrophication and invasive species - and provides just one example of the effects of one type of marine pollution.


24/10/2014

The Anthropocene

Although this isn't exactly what I was planning to blog about in my second post, I thought it was too important a topic to pass up. The Anthropocene is having a moment. In fact, it is trending on social media [Figure 1]! As an environmental scientist in the making, this is hugely exciting.

Figure 1. Screen shot from my Facebook page (October 2014)

So, what exactly is the Anthropocene?

I touched on it briefly in my first post when I talked about Rockström et al.'s paper, but essentially it is the term used to describe how anthropogenic activities are altering the Earth's natural processes (i.e. biological, geological and chemical processes) so much so that they are now the driving force behind these processes.

Our impact on the planet is unquestionable. Take the go-to indicator for human-induced change: atmospheric CO2 concentration. In May 2013, CO2 levels reached 400 parts per million (ppm). Such levels have not been seen in millions of years (Jones 2013), and have certainly never been experienced by humans before. Although the Earth's climate system has undergone significant changes and seen many fluctuations over time (Zachos et al. 2001), these changes have never been as rapid as those seen in the last 200 years or so (Steffen et al. 2007).
Our impact on the planet is not only limited to climate change, but to ocean acidification, deforestation, changes to the nitrogen cycle due to our relentless use of nitrogen fertilisers, as well as species extinction (as mentioned in my first post).

The term Anthropocene was formally introduced into the literature by atmospheric chemist Paul Crutzen and biologist Eugene Stoermer in 2000 (excellent article - another must-read), although Stoermer had been using it since the 1980s (Revkin 2011). Since, the Anthropocene has been used in thousands of papers and is now widely accepted by the scientific community, with many suggesting that the term be used to delimit a new geological epoch (we are current in the Holocene, which started approximately 10-12,000 years ago).

And this is precisely why the Anthropocene is trending: the International Commission on Stratigraphy (ICS), whose role it is to define Earth's Geological Time Scale, has commissioned
a group of scientists and humanists united under the Anthropocene Working Group (AWG) to come up with "a proposal for the formal ratification of the Anthropocene as an official unit amending the Geological Time Scale". The AWG met for the first time last week in Berlin and have until 2016 to formulate the proposal and present it to the ICS for deliberation.

Exactly when the Anthropocene started is much debated. Some experts (such as Crutzen and Stoermer) maintain that it started with the Industrial Revolution (~150 years ago), while others argue that humans have been manipulating and thus impacting the planet for tens of thousands of years, notably since the advent of agriculture (Ruddiman 2013).

Regardless of when the Anthropocene actually started, it seems we can no longer ignore how big an impact we are having on the planet and its resources nowadays. I'm surprised it has taken this long for the Anthropocene to become mainstream news. But better late than never..!

14/10/2014

Welcome!

Over the course of my degree, I have spent a great deal of time focusing on a diverse range of environmental issues (no surprises there..!). However, when I began brainstorming possible topics for this blog, I realised that two issues in particular dominated my studies: biodiversity loss and climate change. 
And rightfully so! These are the two most significant environmental issues of our time.

Anthropogenic activities, such as deforestation and the burning of fossil fuels are now widely accepted as the driving force behind a number of global environmental changes. In their paper, Rockström et al. (2009) established a set of parameters for a range of earth-system processes. They proposed certain boundaries for each of these systems believed to be the "safe operating space for humanity". Unsurprisingly perhaps, climate change and biodiversity loss are two of the three systems whose boundaries have already been crossed [Figure 1] (on a side note: it is a brilliantly written paper and one of my favourites - a must read! The edited summary can be read here. Also, check out this TED talk by lead author Johan Rockström explaining concepts from the paper).


Figure 1. The Earth-system processes devised by Rockström et al. (2009).
The green area delimits the "safe operating space for humanity"; the boundaries for biodiversity loss and climate change have already been crossed.


The rate at which we are losing species is alarming - so much so that the Earth's sixth mass extinction may in fact be well underway (Barnosky et al. 2011). According to Pimm et al. (2014) "concerns about biodiversity arise because present extinction rates are exceptionally high". The authors state that current extinction rates are estimated at approximately 100 species per million species per year (E/MSY). This is around 1000 times greater than the background extinction rate (i.e. what the extinction rate would be in the absence of human actions) of 0.1 E/MSY.
Other figures are just as worrying: The Living Planet Index, which is published as part of the Living Planet Report revealed that the population sizes of vertebrate species have declined by 52% in the last four decades. Moreover, the Index, which can also be broken down into ecosystems, showed that freshwater species have declined by about three-quarters. Clearly, biodiversity loss is an issue that warrants a great deal of attention.

Climate change is perhaps the biggest environmental issue of modern times. The Intergovernmental Panel on Climate Change (IPCC) stated in their Fifth Assessment Report that "warming of the climate system is unequivocal". Similar to biodiversity loss, it is the accelerated rate at which climate change is occurring that is even more troubling (Steffen et al. 2007).
Putting aside the fact that I actually study this, not a day goes by that I don't read about climate change, whether in the news or on social media. There are a number of campaigns committed to raising awareness on the effects of climate change. Recent examples include the People's Climate March and Greenpeace's Save The Arctic campaign. Even national treasure Emma Thompson has got on board with Greenpeace to campaign against the destruction of the Arctic.

So, with this in mind, I have decided to tackle an environmental issue that is perhaps a little less topical but no less interesting or important (at least to me!): marine pollution.

The reason for this choice is a video I came across a few years ago, which struck me and has stuck with me ever since (see below). I was aware that marine pollution was "a thing" but not to that extent, and I realised that I actually knew very little on the subject.

Over the next few months I will be investigating marine pollution, identifying its sources and exploring its impact on the ocean and its inhabitants, as well as further afield.

So, without further ado, I welcome you to An Ocean of Waste!