1. Somewhere... Below the Sea: Artificial Reefs Explained

What Are They and Why Use Them?
Artificial reefs are human-made underwater structures, deliberately placed to mimic natural reefs and enhance marine habitats that can provide shelter, promote vegetation growth, and create breeding and nursing grounds for various marine organisms. These reefs are also created to aid in coastal defence as they can dissipate hydrodynamic energy (fluid energy associated with flow, velocity and pressure) which in turn reduces the amount of erosion and wash-back caused by waves. These calmer conditions allow aquatic plants, like eelgrass, to colonise, which further helps to mitigate erosion as the plants further mitigate hydrodynamic energy and stabilise sediment to the sea floor.
 

The picture above is an artificial reef that was implemented off Hinatuan Island, the Philippines. This project was created to help boost marine diversity, as fish numbers had dwindled due to the destruction of coral reefs by commercial fishing methods like trawling, cyanide, and dynamite use.


Climate Change Effects of Rising Sea Levels/Flooding
Global warming is rising, mainly due to harmful anthropogenic activities like deforestation and the burning of fossil fuels. The increase in temperature is causing polar ice sheets, and glaciers to melt, and increasing thermal expansion in oceans. As a result, sea levels are rising which poses a significant risk to coastal settlements, especially those in small island nations, like the Maldives and Tuvalu, but also to larger low-lying countries like the Netherlands and Denmark. Flooding can cause death, the displacement of people from their homes, and can spread water-borne diseases like cholera, diarrhoea, or typhoid.


The picture above shows the residents clearing the only main road in Funafuti, Tuvalu, after flooding.
 
Wildlife on islands are also very susceptible to the impacts of rising sea levels. Fresh water sources can become salinized, in which the water becomes too salty and undrinkable. The habitable land area for terrestrial species also shrinks which can lead to a shortage of food and an increase in species competition for resources.

The submergence of these islands and the death of many plants may cause the release of carbon, nitrogen, and phosphorus back into the atmosphere, directly contributing to global warming. With less land available, fewer terrestrial plants can grow to absorb carbon from the atmosphere, further accelerating this negative effect.


My Experience
For my university's 12-week work placement, I travelled to Denmark to further explore artificial reefs and their uses. I have seen them used for coastal defence of beaches, boosting marine biodiversity, and protecting bridge piers from scour (the erosion of sediment from around their foundations by water currents). This blog provides an in-depth look at man-made reefs, with examples from Denmark.





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