Oxybenzone and Coral Reefs

A new study published last week has raised awareness of another direct anthropogenic impact on coral reefs and consequently tropical fish that use the structures for shelter and food. The study by Downs et al. investigates the effects of Benzophenone-3 (Oxybenzone) which is an ingredient found in suncream, on the coral Stylophora pistillate as well as its toxicity with 6 other coral species. The study was set in the U.S. Virgin Islands and Hawaii where notable contamination of corals was found. The important message to take from this study is that the chemical, which is derived essentially from tourist related activities poses a new hazard to coral reef conservation and threatens the resiliance of these corals to climate change as the samples exhibited increased bleaching with exposure to Oxybenzone. Whilst the study is very technical and written for readers with a background in chemistry it shows yet another way we are inadvertently impacting coral reefs. The study also makes me question whether this chemical also has direct impacts on the aquatic species that are exposed to it? it will be interesting to see how literature around this topic develops.

What causes coral bleaching?

Here is a simple yet effective illustration of what coral bleaching is and what its causes are (figure 1).

Figure 1. Coral reef bleaching (source: NOAA)

The current El Niño Southern Oscillation event and what it means.

The theme of this blog has importance as we are currently in the midst of the third global bleaching event, related to one of the strongest ENSO events we have ever seen. Unfortunately, as a result of the ongoing nature of this issue, no academic papers have been published, however there is a wide array of news articles and videos that draw alarm to this current event.

Before I start discussing these aspects, the National Oceanic and Atmospheric Administration has been updating a blog almost every fortnight following this year’s ENSO. It provides good meaningful empirical analysis of the event but does so in an informal and digestible tone making it both extremely interesting and accessible. Furthermore, the blog has different contributors whom post about its wide varying impacts from effects on drought in Australia to the snow we can expect this winter in the UK. (update: looks like the snow didn't turn up after all!)

Looking at their most recent post providing an October update, we can get a good understanding of how the current el Niño has been following the trajectory that the 1997 event had. Looking at Figure 1 we can see that the 2015 El Niño is now reaching its peak in the coming months but that also it has been slightly more moderate than that of the 1997 El Niño. The September 3-month average sea surface temperature was 1.5 above normal, third behind September 1987 (1.6) and 1997 (1.7). Regardless, the impacts of this event are to be catastrophic to coral reef colonies as though 18 years on from the 1997 event, a large amount of these destroyed reefs still haven’t recovered.

Figure 1. NOAA publication of SST's of the tropical Pacific

The NOAA were the first to declare the third bleaching event, their article further shows the potential projected threats of this El Niño event on coral reefs around the world. High SST’s are already causing bleaching in Hawaii but NOAA confirm that the same stressful conditions being seen in the pacific will spread to the Caribbean and Australasia very soon, potentially extending past new year (figure 2).  

“we are losing huge areas of coral across the U.S., as well as internationally. What really has us concerned is this event has been going on for more than a year and our preliminary model projections indicate it’s likely to last well into 2016.” 

Mark Eakin NOAA

Figure 2. NOAA forecasted Coral Reef bleaching

The concerns about the length of time these coral reefs are to undergo stress is related to the fact that short term bleaching isn’t entirely detrimental as corals can respond, unlike prolonged long term bleaching where this isn’t possible as total degradation and erosion ensues. Most importantly however as with the interest of this blog, it will mean fewer habitats for fish and other marine life, including ecologically and economically important species.

Also, for a quick decent summary article on the current global bleaching event please refer to the one published by the New Scientist.

Welcome! An introduction...

In the last quarter of my year abroad in Los Angeles, I enrolled in a class which was broadly named 'Humid Tropics,' it was one of the more simple yet interesting courses I attended whilst there (I have discussed this in my Year Abroad blog). The purpose of this class was to learn about the fascinating terrestrial and oceanic species that are found in the tropics. Whilst it may seem comical, I visited the Los Angeles Aquarium as a form of revision to see some of these elegant tropical species. 

When I was presented with the opportunity to identify a topic related to Global Environmental Change, choosing something related to these reef species wasn't a difficult decision for me.

Whilst my interests in Geography do not lie in ecology, analysing Coral Reef destruction be it through anthropogenically induced impacts or more natural impacts such as coral reef bleaching is a strong interest of mine. 

Corals undeniably provide significant benefits to humans and represent $30 billion a year of goods and services. Whilst supporting fisheries which are vital for sustaining the diets of poorer coastal regions of the world, they also are the focal point of a lot of tourism and medical advances (WWF, 2015). Most importantly however they are home to the most diverse assemblages of tropical fish species that no aquarium could replicate. 

The focus of this blog will be on the non intrinsic ecological value of these coral reef species and how habitat destruction has affected tropical fish species that rely on the health of coral species. Figure 1 shows the distribution of coral reefs, around the equator, in the warmest waters and crucially in areas where El Nino Southern Oscillation events occur.

Figure 1. Global extent of Tropical coral reefs (Source: Coraldigest.org)

When thinking about this post, I wanted to investigate further the impacts of the well known 1998 ENSO event on tropical fish assemblages. I looked into a paper by Garpe et al. (2006) which assessed the 'long term' impacts of the coral bleaching that occurred due to ENSO. The ENSO event is widely regarded as the most severe on record and affected coral reefs worldwide, leaving 90% of coral species in some localities being decimated and rendering significant impacts on the species that relied on coral for habitat.

The paper looks at the effects on destroyed coral of Tutia Reef in Mafia Island Marine Park (MIMP), Tanzania in 1997, 6 months after the ENSO event of 1998 and 6 years later in 2004, attempting to provide an analysis of the long term impacts on this particular reef. Following the 1998 mass bleaching event, all corals in 28/32 plots had died. The paper places strong emphasis on the importance of structural complexity of habitats and how with structural complexity there exists abundant and species rich reef fish communities, affected more intensly over longer timescales. Whilst  Garpe et al. (2006) emphasises the impacts of bleaching on long timescales, others report that fish assemblage is not affected significantly with only 10% change following a 40-50% reduction in Coral cover. I will be looking at this in a further post.

An aspect I would have found interesting would be an investigation similar to that of  Garpe et al. (2006) but on a longer timescale to see if there is another notable response that occurs later. In further posts, I will introduce some species that are in danger of increasing global temperatures and the resulting frequency and severity of future ENSO events.

Importantly however, this blog is being created in the midst of a coral bleaching event that could be more severe than the 1998 event, I will be posting more up-to-date articles that reflect on and assess this current bleaching event.