Reef Projects

What types of breakwater reef exist in the Caribbean? In addition to Darwin's trilogy of Fringing, Barrier and Atoll reefs, we know next to nothing about their morphological variation or distribution. Until recently, surveying reef types was logistically difficult, requiring large amounts of time and money. But since the release of Google Earth in 2005, we can now see–and measure–virtually all reefs in the Caribbean from the comfort of our Labs.

In this project we are mapping every visible reef in the Caribbean in an attempt to identify the main morphological types and their distribution. The mission: to elucidate the physical and ecological controls on reef development. Why is this important? Well just knowing what's out there is key to solving all sorts of basic scientific questions about reefs, such as why do they develop in one place and not another? and are there distinct stages of reef development in time and space?

Answers to these basic questions may have useful applications in areas such as coastal protection, reef restoration and/or conservation. Many Caribbean reefs for example are in bad shape, so maybe our work can help identify which reef types are most vulnerable and pin-point where conditions are optimal.

Lead Investigator: Paul Blanchon

Project Team: Rodrigo Garza, Alexis Medina, Eduardo Islas, Simon Richards

Funding: We are looking for grants to continue with this work.

Geologists and Ecologists view reefs as being composed of coral frameworks, where corals grow on-top of each other, gradually rising above the sea floor to form large breakwaters. Yet we also know that hurricanes commonly destroy reefs and have done so for thousands of years. So the question is, what process dominates to produce these structures–growth or destruction?

To answer this question we are comparing the anatomy of reefs that are repeatedly struck by hurricanes with those that are protected from them. So far we have found that hurricane-prones reefs are dominated by layers of coral debris rather than framework. Also, these reefs are located a set distance behind slope breaks that trip large waves as they cross the shelf, causing them to break over the reef-front and destroy corals. These waves then deposit the broken coral a fixed distance behind the slope break forming a breakwater. And when the hurricane is over, this rubble ridge is recolonised by corals and algae and the cycle begins again.

Next we need to test this model by predicting what we should see in reefs in more protected locations, such as Majahual which is protected by the Chinchorro Bank.

Lead Investigator: Paul Blanchon

Project Team: Eduardo Islas, Alexis Medina, Simon Richards, Juan-Pablo Bernal

Funding: CONACyT 18879 (2019-2022)

We all know about the main types of coral reef—Fringing reefs, Barrier Reefs and Atolls. But there are times when things don't fit into the boxes we've made for them and a rethink is required. In our case, we've discovered a whole new class of reef that has no box whatsoever. We're calling this new class 'Dispersed Reefs' because instead of forming linear breakwaters, these reefs are dispersed over much wider areas, and consist of hundreds of patch-reefs or reef-ridges arranged in different configurations.

Interestingly, these reef dispersions can protect the shore in a similar way to traditional linear reefs. But instead of causing all waves to break in one place, they diffract waves causing interference which quickly dampens their energy, producing a sheltered rear lagoon. In many areas, this more diffuse coastal protection allows shorelines to advance out into the lagoon creating new land.

As with any new discovery, we have to figure out what to study and how to organise this reef class into distinct sub types. Dispersed reefs that form in sheltered bays and lagoons might be different from those that occur on open shelves. Once we know what they all look like, their differences from linear reefs can be defined, and perhaps then we can figure out why they form instead. When this is all nailed down and we've figured out how nature works, perhaps the answers can then be applied to some practical problems.

Lead Investigator: Paul Blanchon

Project Team: Alexis Medina, Eduardo Islas, Rodrigo Garza

Funding: We are looking for grants to continue with this work.

In the good-old-days, story has it that Caribbean reef crests were dominated by dense thickets of a robust-branching coral called Acropora palmata. This coral was adapted to live in the rough-and-tumble of the breaker zone and, over thousands of years, was almost entirely responsible for building the reef structure. But then we showed up and it's been downhill since. Nowadays, dense thickets of Acropora are hard to find, and reef crests are covered only by their dead stumps and broken skeletons, as you can see above.

The problem is we have no idea if, back in the day, all reefs were completely covered by Acropora or not. The Ecologists studying them at the time obviously avoided the dead and dilapidated, and instead chose more picturesque 'pin-up' reefs with dense vibrant thickets–who wouldn't? But we really don't know how normal these 'pin-up' reefs were at the time. So the question we need to answer is what's the natural state of Acropora reefs—always covered, or sometimes not, and for how long?

In this study we will perform an 'autopsy' on a dead reef to find out exactly when was the last time it was in a 'pin-up' state covered by dense thickets. This postmortem analysis will look for the stumps left by the last Acropora thickets and date when they last grew using U-series radioisotopes. From these dates we can figure out if thickets covered the entire reef all the time, covered it episodically, or only covered it in different places at different times. This will provide better insight into the natural state of Acropora reefs, and thus help gauge the full extent of human impact.

Lead Investigator: Alexis Medina

Project Team: Paul Blanchon, Juan-Pablo Bernal, Lorenzo Álvarez Filip

Funding: PAPIIT IN214819 (2019-2022)