ECR feature: Taís F. R. Guimarães on the sea-level impact on coastal lagoon fish communities

Taís F. R. Guimarães is a postdoc at the Universidade Federal de Viçosa (UFV) in Brazil. She is an ecologist interested in elucidating spatio-temporal processes affecting the community of freshwater fishes. Here, Taís shares her recent work on the effect of sea level on the beta diversity of coastal lagoon fish communities in South America.

Taís presenting the preliminary results of this study at the 2nd Meeting of the Brazilian Association of Ecological Science and Conservation (RABECO) and the 6th edition of the Theoretical Ecology Symposia (SET) organized by the University of Campinas in September of 2018 in Brazil.

Personal links. Research Gate

Institute. Universidade Federal de Viçosa (UFV) – Brazil

Academic life stage. Postdoc

Major research themes. Landscape ecology, community ecology

Current study system. I am currently a postdoc at the Rio Doce Aquatic Biodiversity Monitoring Program. In this project, we evaluate the effect and implications of an iron ore tailings dam breach on the fish community from the Doce River basin, southeastern Brazil. What makes this study interesting is that entire fish populations died immediately after the disaster, and we are responsible for monitoring and evaluating how the restocking process is happening along this river basin.

Recent JBI paper. Guimarães, T. de F. R., Petry, A. C., Hartz, S. M., & Becker, F. G. (2021). Influence of past and current factors on the beta diversity of coastal lagoon fish communities in South America. Journal of Biogeography, 48(3), 639–649

Sampling the ichthyofauna in the Itapeva lagoon, Rio Grande do Sul, southern Brazil.

Motivation behind this paper. Although the study was part of my doctoral thesis, I’ve been studying coastal lagoon fish communities since my undergrad. My motivation for the development of this study came from a need to understand how the colonization process by the fish community happened during the formation of the lagoons along the Atlantic coast of South America. Several studies point to the importance of the sea-level fluctuations since the Last Glacial Maximum (LGM) impacting populations and communities of freshwater fishes in coastal streams. From reading these works, I asked myself if these historical sea-level changes could affect the ichthyofauna of geologically more recent environments, such as lagoons that are considered geologically younger than the streams. These coastal lagoons are situated in a portion of the continental shelf that was covered by the sea during the last marine transgression. After a reduction in the sea level to its current level, this area was exposed, allowing the establishment of freshwater environments around 5k years ago. Thus, in this study, I aimed to identify if there is a historical sign from the LGM on the fish diversity in coastal lagoons.

Key methodologies. In this study, we combined methodologies that have been applied in other studies to infer the impact of historical and contemporary factors on the beta diversity of coastal lagoon fish communities. For example, we used a bathymetric shapefile to project the coastline during the LGM event. Based on sea-level fluctuation estimates over time, we measured the amount of time these current drainages are isolated. We also used a night light image as a proxy of physical and biotic anthropogenic influence on coastal lagoons. Combining these data with species occurrence in 129 lagoons along the Atlantic coast, we were able to disentangle the effect of current and past factors in shaping the ichthyofauna diversity.

The Preta lagoon (left of the photo) and its proximity to the sea (right of the photo) at Parque Nacional da Restinga de Jurubatiba, Rio de Janeiro, southeastern Brazil.

Unexpected challenges. The first challenge was to compile and organize the ichthyofauna data. It was challenging to bring together data from different papers and contact researchers. The Geographic Information System (GIS) portion of choosing and manipulating the images to extract the required variables also needed dedication and study. Another major challenge was the data analysis, and I’m grateful to the manuscript reviewers who provided essential contributions to increase the power of the statistical analysis. Anyway, the whole development of this research was a learning process and a lot of dialogue between the co-authors. The final result was gratifying.

Major results. In this study, we provided evidence that the signal of past biogeographical events, such as connectivity between currently isolated drainages due to sea-level retreat, might be present in freshwater environments, even in communities that were supposedly formed at more recent geological times. A broader implication of these results is that high regional beta-diversity can be rapidly generated, even in regions and ecosystems of relatively recent origin, such as coastal plains and freshwater coastal lagoons. These lagoons were formed about five thousand years ago, being recolonized by freshwater fishes’ species that persisted in landscape refuges during past sea level increases.

Emboabinha lagoon, Rio Grande do Sul, southern Brazil.

Next steps for this research. The biogeographic and paleobiogeographic history of coastal lagoons is complex, and past conditions are challenging to measure. Thus, the next step in this research is to test different quantitative metrics of past habitats, such as obtaining paleosalinity from water bodies, estimate the area and spatial configuration of the lagoons during the LGM. These metrics can capture distinct characteristics of the past landscape, adding new insights for understanding current diversity patterns. However, perhaps it is more urgent to pay attention to the processes that are currently taking place. In recent years, the presence and expansion of exotic fish species have increased in lagoons and rivers. For this reason, another next step should be to identify the routes of dispersion for these invasive alien species to mitigate or prevent changes in the community.

If you could study any organism on Earth, what would it be? I would continue to study fishes. I like fishes because they are “mysterious” in the sense of being unseen organisms because they are underwater and out of sight. Also, they are often neglected in conservation strategies, especially in Brazil.

Negra lagoon, Rio Grande do Sul, southern Brazil

Anything else to add? The manuscript had contributions from many friends who heard my ideas and helped me to develop them. I believe that these non-formal conversations contributed a lot and provided new insights during the elaboration process. The reviewers’ comments and criticisms were also very important for the final result of the study.

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