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Coral: Drastic changes off Mexico

A team of researchers led by the University of Bremen and the National Autonomous University of Mexico has determined the ecological changes in the Mexican Caribbean coral reefs over the past 40 years. The results: Only few reefs are still dominated by coral.

This study shows a drastic coral cover decline between the late 1970s and the beginning of the millennium. By the late 1970s, the Mexican Caribbean mean coral cover was 26%, which progressively decreased until the minimal historic of 12% in 2005, a year that was characterized by immense coral bleaching in the Caribbean. From 2005 until 2016, there was a partial - but extremely slow - recovery in coral cover reaching 16 % in 2016. Despite the observed partial recovery, the rate of macroalgae increase largely exceeded coral cover change. Now, ca. 80 % of all observed reefs are dominated by algae. This stands in sharp contrast to the situation in the late 1970s when all reefs were still dominated by corals.  By replacing coral with algae, important reef functions, such as coastal protection and fishing yield, can become impaired. This has been reported with regard to many reefs in the Caribbean and beyond. 

Contrary to the research team’s expectations, there was a significant macroalgae cover increase also in the central and southern sections of the Mexican Caribbean, which is characterized by a rather low population density. Intense discharge of nutrient-rich freshwater may be one reason for this. It can lead to the fertilization of coastal coral reefs, so that corals always come off worse when in competition with algae and thus, are overgrown. 

Lack of Sustainability as a Reason for Degradation

The tourism industry and coastal expansion without sustainable planning are factors that contribute to the degradation of the Mexican Caribbean reefs. Therefore, the study highlights the need to improve local management of reefs, which is significant for reef preservation. 

The results of this study were published under the title A meta-analysis to assess long-term spatiotemporal changes of benthic coral and macroalgae cover in the Mexican Caribbean: https://rdcu.be/b4ydx

Contact:

Ameris Ixchel Contreras Silva
Phone: +49 (0)176 43875 146
Email: amerisixcontrerasprotect me ?!gmailprotect me ?!.com

Prof. Dr. Christian Wild
Marine Ecology Department
Faculty of Biology and Chemistry
University of Bremen
Phone: +49 (0)421 218-63367
Email: christian.wild@uni-bremen.de

Lorenzo Alvarez Filip 
Biodiversity and Reef Conservation Lab
Reef Systems Unit, ICML, UNAM
Phone: (+52) 998 9372 917
Email: lorenzoaf@gmail.com 
www.barcolab.org

 

[Translate to English:]
Healthy coral reefs in the Mexican Caribbean appear similar to those in the 1970s – here is a stony coral of the species Orbicella annularis with a school of Haemulon flavolineatum fish. Photo: Lorenzo Alvarez-Filip