Brazilian reef fish are resilient to climate change and coral decline

A study published in the journal Scientific Reports suggests that the fish communities that inhabit the reefs off the Brazilian coast are resilient to environmental changes resulting from climate change, including the decline of corals.

The research was carried out within the scope of the Brazilian Reefs in the Anthropocene project (ReefSYN), of the Center for Biodiversity and Ecosystem Services (SinBiose/CNPq), and was supported by FAPESP.

“Due to high sedimentation and the influence of freshwater from rivers, Brazilian reefs have a low coral cover and low structural complexity compared to other regions, such as the Caribbean. For this reason, they are called ‘marginal’ reefs. The study showed that the fish communities in these places are resistant to climate changes that negatively influence coral communities”, explains Juan Quimbayo, co-author of the study and postdoctoral fellow at the Center for Marine Biology at the University of São Paulo (CEBIMar-USP).

The results contrast with what occurs in the Indo-Pacific and Caribbean oceans, where coral decline often leads to the general collapse of the entire reef ecosystem. It is therefore possible that fish on Brazilian reefs will be able to better adapt to a future with fewer corals, which are extremely sensitive to climate change.

Even though they are not very abundant, the corals of the Brazilian coast favor the occurrence of fish and help to increase the diversity of these animals in the reefs.

“Coral colonies offer many resources for fish, such as shelter and food. Therefore, around 40% of the fish species analyzed, out of a total of 113 species, are more likely to occur in places with greater abundance of corals” , says André Luza, first author of the study and postdoctoral researcher at the Federal University of Santa Maria (UFSM).

To arrive at the results, the researchers made computational models from the observation of reef fish in 36 points distributed along the 8 thousand kilometers of Brazilian coastline. Data collection consisted of installing cameras covering two square meters at various collection sites, resulting in approximately 4,000 hours of footage.

“There were countless cameras to record the activity of the fish on the reefs. As a result, it was possible to associate the activity of the fish with organisms fixed to the bottom of the sea, on a very fine scale”, says Mariana Bender, a professor at the Federal University of Santa Maria and coordinator of ReefSYN, who also signs the study.

According to the authors, Brazilian reef fish are likely to maintain much of the ecological functions they perform, despite climate-induced coral declines and the consequent loss of coral-associated species.

The researchers point out, however, that the analyzes were only done on a computer and the corals were not removed experimentally to identify other systemic effects. It is not known, for example, what cascading impacts may occur with the withdrawal of species from the ecosystem or whether overfishing has already affected the ecological functions of reef fish.

Even so, the results contribute to the planning of conservation strategies for Brazilian reefs focused on climate refuges, that is, on prioritizing environments capable of adapting to climate change.

Reefs are structures formed by skeletons of invertebrates on the rocks of the shallowest portions of the oceans. These ecosystems occupy only 0.000063% of the Earth’s surface, but they are home to at least a quarter of all marine fauna and flora.

Due to fishing, pollution and climate change, these species are in decline globally. It is estimated that 14% of the world’s corals disappeared between 2009 and 2018, which represents about 11,700 square kilometers.

The article Low functional vulnerability of fish assemblages to coral loss in Southwestern Atlantic marginal reefs can be read here.

* With information from the Synthesis Center on Biodiversity and Ecosystem Services (SinBiose).