Written by Gustavo Shintate
Edited by Bobbie
INTRODUCTION
The Brazilian “jeitinho” is an expression that I like to define as: “to act promptly with a creative, open-hearted manner against adversity”. In 2018, Carla Elliff wrote about the “jeitinho” way coral reefs grow in Brazil – how they adapted to adverse conditions. In this article, I will write about how the Queimada Grande Reef, a subtropical Brazilian coral reef, finds its way to keep reef accretion happening, despite its senescent coralline structure dating back from 2300 years before present.
“JEITINHO WAY”: RESILIENCE AND FRAILTY OF BRAZILIAN REEFS
Carla’s article shows how critical reef-building coral species are for Brazilian marine biodiversity and how they can form exclusive features in turbid, marginal conditions, such as the “chapeirão” structures (mushroom-shaped pinnacles) formed at the Abrolhos Bank. We have only 20 reef-building species in our waters, too little compared to the Indo-Pacific Ocean. Some of the species that occurred here are endemic, only occurring in Brazilian waters. On the one hand, it is significant that we have “exclusive” species. If we think about it, it also means that once they are gone, they are gone from the whole world, making the conservation of the environments built by those corals a big concern for Conservation.
QUEIMADA GRANDE REEF AS A SENESCENT REEF
Despite being known for its tropical forests and beaches, Brazil’s territory comprises a subtropical climate. The discovery of a subtropical turbid reef was unexpected (Pereira-Filho et al., 2019 or Reefbites article here), as it is located nearly 1000 km further from the previously southern limit of coral occurrence – the tropical Abrolhos Reef Complex. In 2021 we published an article (Pereira-Filho et al., 2021) about that time when “the Southernmost Atlantic Coral Reef” took a 3000-yr-nap (and then another 2000-yr one), and we learned how the coralline structure is currently on a dormant, senescent state despite the rich diversity of fish present in the area and also non-coral dominance on the reef’s surface nowadays. A remaining unanswered question is whether the QGR framework is now “growing” or eroding after all this time. Understanding this is crucial if we want to take adequate measures to protect these biogenic structures and support biodiversity and ecosystem services.
WHAT DID THEY FIND?
If corals do not contribute to the reef structure and assuming the reef has remained relatively stable, where does carbonate production come from? Who is “cementing” this biogenic living building together even after 2300 years of coral reef napping? Is the reef in danger? Apparently, the answer lies again in the Brazilian “jeitinho”.
Part of the answer was reported in the recently published article by Randi et al., (2021), first-authored by my personal friend and lab partner for many years, Caroline Randi, MSc. The “paper” (as we casually call peer-reviewed scientific journal articles) was published in Marine Environmental Research. It can be found here (link) or available for request on Research Gate or even on this Twitter thread I made.
In figure 2, we can see one of the accretion units (CAUs), a methodology used to calculate calcification and an artifact to understand which organisms are colonising the reef. The results showed that turf, crustose coralline algae (CCA) and tunicates were the most critical for colonisation of the CAUs. Dominant species were all non-coral organisms: tunicates, CCA, bryozoans, polychaetes, bivalves and cirripeds. Considering the various forms calcium carbonate crystals can be formed, the more stable aragonite (produced by tunicates and bryozoans), and the less resilient, magnesium-rich calcite (produced by red algae), are both found in the study, with implications regarding ocean acidification in the area.
The study also pointed out that the colonisation of CCA on adjacent dead coral fragments, forming rhodolith beds, was also crucial for carbonate fixation, as they produce carbonate in the form of Mg-calcite. Total annual production in the reef is estimated at 40,5 t yr-1, considering its area of 320 000 m^2, but, when looking at the rhodolith bed, covering an area of 960 000 m^2, rhodolith-produced carbonate is estimated to be 823.7 t yr-1.
Finally, the article discusses the emerging evidence that most of Southwest Atlantic marginal reefs have reached a state of senescence and found another way of growing or preserving their bio-constructed structures: getting help from a range of non-coral organisms. CCA and bryozoans are nowadays the main calcifiers for the Queimada Grande Reef, which presents little to no vertical accretion since the last 2300 years, and are also dominant in the Abrolhos Reef Complex (Bastos et al.,2018), where vertical growth has been observed promoted by the same category of organisms.
CONCLUSION
Here, we learned about adaptive strategies on Brazilian reefs, especially the Queimada Grande Reef. Despite its dormant state of corals, carbonate accretion by coralline algae and bryozoans is enough to limit net erosion, preserving the underlying reef structure up to this day and demonstrating that it still contributes to the CaCO3 ocean budget. Also, the dead coral skeleton fragments adjacent to the reef, colonised by crustose coralline red algae, formed a rhodolith bed, showing again an example of how Brazilian biodiversity finds unique ways of adapting to adversity. As the southernmost reef in the Atlantic Ocean, situated in a subtropical region, this reef is a unique opportunity to better understand the relationship between marginal reefs and adaptive strategies.
PS: Special thanks to Me. Caroline Randi, for making sure the text was according to the findings of her first-authored article and approving this final version.
REFERENCES
Bastos, et al. “Bryozoans are major modern builders of South Atlantic oddly shaped reefs.” Scientific Reports 8.1 (2018): 1-11.
Elliff. Brazilian coral reefs and their “jeitinho”. Reefbites (2018).
Elliff. A new coral reef has been discovered and you will not believe where it’s located! Reefbites (2019).
Elliff. That time the Queimada Grande reef took a 3000-year nap (and then another 2000-year one!). Reefbites (2021).
Pereira-Filho et al., “The southernmost Atlantic coral reef is off the subtropical island of Queimada Grande (24 S), Brazil.” Bulletin of Marine Science 95.2 (2019): 277-287.
Pereira-Filho et al. “Growing at the limit: Reef growth sensitivity to climate and oceanographic changes in the South Western Atlantic.” Global and Planetary Change 201 (2021): 103479.
Randi, et al. “Calcium carbonate production in the southernmost subtropical Atlantic coral reef.” Marine Environmental Research 172 (2021): 105490.
Shintate. Paper alert thread based on Randi et al., 2021. Twitter (2021).
Reefbites 