By: Ayla Sage
Edited by: Sofia Perez
As we know, coral reefs are in a drastic state globally. More and more corals are becoming bleached and facing mortality worldwide because of stress from climate change and other human behaviors. Although mitigation of global carbon emissions would be the best fit solution to this problem, it is unlikely that this solution will be reached according to Greenhouse Gas Emission Models. Luckily, biological and ecological interventions are being worked on to enhance the thermal tolerance of some coral species by 1°C, but sadly this may not be enough . Many emission prediction scenarios still show upcoming temperatures that exceed the thermal tolerance of most coral species. In this paper I’ll touch base on some of the proposed biological and ecological interventions and give a more in-depth explanation on one or two proposed environmental interventions that not as many people may know about.
Biological and Ecological Interventions
Some may question the ethicality of intervening with natural systems, but the truth of the matter is that if we don’t do anything, it’s possible that we may permanently lose our coral reefs. This means no more dynamic, colorful, and underwater views for our future generations to witness. Overall, there are four categories for intervention practices that we can use to give our reefs a fighting chance: genetic & reproductive, physiological, coral population & community, and environmental. Additionally, there are different magnitudes of risk associated with the different levels of ‘intervention’ in each category, so it is imperative to complete a thorough assessment before initiating any at a given location.
The figure above shows examples of different interventions that fall into each category. All categories, besides environmental, primarily deal with the handling and care of the physical corals themselves. Although these activities are separated into their respective “bins”, they are all interconnected. There is not one single intervention that is going to work for one reef, much less all reefs. So, it is important to adopt a fast-fail approach. This mindset entails rapidly trying interventive approaches, and if they do not work, moving on to the next to see what does. While these natural intervention measures may seem promising, we cannot forget the root cause of all our problems- carbon emissions!!
As we just discussed, most of these interventions involve the direct handling of corals. However, there are some that work to better stabilize the surrounding environments of these reefs. I personally find these approaches (a.k.a. environmental interventions) to be extremely creative and innovative! They also do not seem to be as covered as other categories in the media, which is why I’d like to go into some detail about one here.
The method of shading is one of my personal favorites and what I find the most interesting due to its various approaches and creativity. Shading interventions are set to reduce the exposure of coral reefs to solar radiation , mitigating light incidence and/or lowering water temperatures. As in most cases, we can learn from history. It’s possible that this idea of shading came from the 1998 summer bleaching event. During this time, Pacific living corals avoided bleaching by being covered by naturally forming clouds .
In the context of intervention, shading can either be of the atmosphere or water column and surface . You may be wondering how one can simply ‘make’ these white cotton-candy-looking things we call clouds. Well, atmospheric shading is completed by introducing reflective particles in the upper atmosphere which induces low-altitude cloud formation . Cloud formation can also be induced by spreading fine-misted seawater particles near the marine surface . These clouds work to reflect light back into the atmosphere rather than into the water.
Marine shading, on the other hand, can be completed in different ways. The first approach involves increasing the turbidity of the water. Suspending particulate matter filters light in the water column and reduces the amount of light that hits the seafloor. You can imagine this as trying to shine a flashlight through a glass of crystal-clear water vs. murky water you scooped up from a lake. Then there’s shading layers. These layers include both fixed physical shades (i.e., surface shade cloths) and temporary surface films . One project being conducted on the Great Barrier Reef is trialing a polymer film that consists primarily of calcium carbonate and is biodegradable and innocuous . Next comes microbubble ocean whitening – what a fun name. One man who goes by the last name of Seitz proposed the use of very fine bubbles to brighten the surface of the water and reflect light away from the ocean floor. So far, this method has been running smoothly and at a relatively low cost! Our last shading method is called wave-lensing reduction. Lensing is the focusing and defocusing of incident light that hits the ocean’s surface and is controlled by the moving of waves . Although lensing produces pretty light patterns on the seafloor, it causes highly transient light flickering. The flickering can be diminished with seawater sprinklers. Seawater sprinkler spray water onto the ocean surface and change it’s texture, which changes how the light shines through. However, Veal et al. (2010) concluded from shallow-water experiments that surrounding corals are not negatively impacted by wave lensing at bleaching temperatures; therefore, this potential intervention is not entirely feasible.
There’s no denying that coral reefs are in a perilous situation. Mass bleaching events are predicted to occur more regularly and eventually on an annual basis. This allows corals little to no time to recover. Without interventions, there’s no way they will be able to withstand these detrimental events. Luckily, some of these intervention approaches have proved to be successful and will hopefully buy us some time as we work to address the root cause. Here’s to science, research, and innovation!
 National Academies of Sciences, Engineering, and Medicine 2019. A Research Review of Interventions to Increase the Persistence and Resilience of Coral Reefs. Washington, DC: The National Academies Press. https://doi.org/10.17226/25279.
 Mumby, P. J., J. R. M. Chisholm, A. J. Edwards, S. Andrefouet, and J. Jaubert. 2001. Cloudy weather may have saved Society Island reef corals during the 1998 ENSO event. Marine Ecology Progress Series 222:209-216. DOI: 10.3354/meps222209.
 Latham, J., K. Bower, T. Choularton, H. Coe, P. Connolly, G. Cooper, T. Craft, J. Foster, A. Gadian, L. Galbraith, H. Iacovides, D. Johnston, B. Launder, B. Leslie, J. Meyer, A. Neukermans, B. Ormond, B. Parkes, P. Rasch, J. Rush, S. Salter, T. Stevenson, H. Wang, Q. Wang, and R. Wood. 2012. Marine cloud brightening. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370(1974):4217- 4262. DOI: 10.1098/rsta.2012.0086.
 Rau, G. H., E. L. McLeod, and O. Hoegh-Guldberg. 2012. The need for new ocean conser- vation strategies in a high-carbon dioxide world. Nature Climate Change 2:720. DOI: 10.1038/nclimate1555.
 Seitz, R. 2011. Bright water: Hydrosols, water conservation and climate change. Climatic Change 105(3):365-381. DOI: 10.1007/s10584-010-9965-8.