Coastal Microbial Mats in Karstic Areas: Uncovering Hidden Diversity

Jim Crocker
6th June, 2025

Coastal Microbial Mats in Karstic Areas: Uncovering Hidden Diversity

Distinct microbial mat morphologies were characterized across coastal karstic habitats in the Yucatan Peninsula (A), identifying lift-off mats in Sisal (B), pustular and flat mats in Progreso (C, D), and flat mats in Ría Lagartos (E).

Image adapted from: Cadena et al. / CC BY (Source)

Key Findings

  • In coastal karst habitats of the Yucatán Peninsula, Mexico, researchers found that local factors like salinity, temperature, and redox potential shape the structure of microbial mats
  • Different mat types—flat, pustular, and lift‐off—host distinct microbial communities that drive nutrient cycles and help support nearby mangrove ecosystem health
Recent research from Universidad Autónoma del Estado de Morelos[1] has expanded our understanding of microbial mats from karstic habitats in the Yucatan Peninsula, Mexico. Microbial mats are layered communities of microorganisms that play important roles in nutrient cycling and ecosystem stability. In coastal environments, these mats contribute to the cycling of carbon, nitrogen, and sulfur, influence mineral precipitation, and interact with nearby ecosystems such as mangrove forests. Understanding the conditions that shape these communities is important for managing and preserving coastal ecosystems. In this study, researchers explored three distinct types of microbial mats—lift-off, flat, and pustular—from sites in Sisal, Progreso, and Ría Lagartos. These sites differed in salinity: lift-off mats were found in the lower-salinity waters (about 2.2%) of Sisal, while flat and pustular mats developed in the hypersaline conditions (6–9%) in Progreso and Ría Lagartos. The choice of these varied locales allowed the team to investigate how environmental factors such as salinity, redox potential, and temperature influence microbial community composition. The investigation began with physicochemical analyses using techniques such as X-ray diffraction (XRD) to identify minerals within the mats. The XRD analysis revealed that despite the differences among the mat types, certain minerals (aragonite, calcite, and halite) were common across all samples. Such minerals are important because they are linked to the way microbial communities drive and respond to mineral precipitation—a process also highlighted in earlier studies of similar microbial communities[2][3]. To examine the microbial populations, the researchers applied high-throughput sequencing of the 16S rRNA gene, a common method for identifying bacteria and archaea. This approach provided a detailed look at the diversity within the mats. Statistical analyses showed that salinity, redox potential, and temperature were significant in explaining the differences observed in microbial community structures. For example, flat mats from Progreso and pustular mats displayed similar microbial profiles, with groups like Bacteroidia and Anaerolineae appearing as abundant members. In contrast, flat mats from Ría Lagartos were dominated by Halobacteria, Cyanobacteria, and Bacteroidota, while lift-off mats from Sisal were characterized by a notable presence of Bacteroidia, Gammaproteobacteria, and Cyanobacteria. These differences are important because they indicate that even slight variations in environmental conditions can lead to substantial changes in the microbial ecosystem. In previous work on microbial mats in Shark Bay, Australia, researchers found that distinct mat types (with either nonlithifying or lithifying characteristics) hosted diverse microbial communities[2][4]. The Mexican coastal mats demonstrate similar trends, but with unique community structures and mineral compositions that reflect the local karstic and salinity conditions. In addition, earlier studies have emphasized the critical role of cyanobacteria in the production of extracellular polymeric substances (EPS) that contribute to mat structure and mineralization processes[3]. The new research shows that similar microbial groups are present in the Yucatan mats. The presence of EPS-related active microbial groups in these mats may have parallels with the processes observed in other coastal microbial communities, suggesting that biochemical interactions tied to EPS production are potentially universal in similar environments. Another previous study set in Shark Bay focused on the archaeal component of microbial mats, revealing that archaeal diversity can vary significantly with mat depth and environmental conditions[4]. Although the main focus of the current study was on overall prokaryotic diversity, the detection of groups known to participate in essential biogeochemical cycles (including those involving both bacteria and archaea) strengthens the idea that environmental factors have a strong influence on the distribution of microorganisms within these complex habitats. The findings of this study are relevant not only for advancing scientific knowledge but also for informing the management of coastal ecosystems. Given that some of the microbial mat structures were located close to mangrove forest ecosystems—some of which are undergoing restoration—the insights gained may help guide conservation efforts in the region. By understanding how local environmental parameters shape microbial communities, resource managers can better predict how changes such as salinity shifts or temperature alterations might affect overall ecosystem health. This work from Universidad Autónoma del Estado de Morelos ties together patterns seen in earlier research[2][3][4] with novel observations from a new geographic context. It significantly contributes to our broader understanding of how microbial mats are structured by both biological and physicochemical factors in coastal, karstic ecosystems.

EnvironmentEcologyMarine Biology

References

Main Study

1) Microbial diversity of coastal microbial mats formations in karstic habitats from the Yucatan Peninsula, Mexico

Published 3rd June, 2025

https://doi.org/10.1371/journal.pone.0325200

Related Studies

2) Bacterial, archaeal and eukaryotic diversity of smooth and pustular microbial mat communities in the hypersaline lagoon of Shark Bay.

https://doi.org/10.1111/j.1472-4669.2008.00187.x

3) Metagenomic, (bio)chemical, and microscopic analyses reveal the potential for the cycling of sulfated EPS in Shark Bay pustular mats.

https://doi.org/10.1038/s43705-022-00128-1

4) Dynamics of archaea at fine spatial scales in Shark Bay mat microbiomes.

https://doi.org/10.1038/srep46160


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