Miniature organisms will dominate the oceans of the future

Researchers from the Marine Community Ecology and Conservation group (ECOMAR) Researchers from the University of Laguna led a study recently published in the scientific journal Proceedings of the Royal Society B with the title “High Taxonomic Diversity And Miniaturization In Benthic Communities Under Persistent Natural CO₂ Disturbances.” In collaboration with researchers from the University of Barcelona and the University of Liverpool, they have discovered that ocean acidification (OA) occurring in the oceans due to excess CO2 will lead to a miniaturization of marine benthic communities. This phenomenon is due to the predominance of small algae and invertebrate species, which will dominate the oceans of the future.

During this investigation, a revolutionary tool for science has been used called Metabarcoding, This technique combines massive sequencing with DNA barcoding. It allows for the detection of the true diversity of algae and marine invertebrates through the mitochondrial COI gene, without relying on the bias of the human eye. The application of this DNA-based method facilitates highly reliable, standardized, and replicable measurements for assessing the true biodiversity of an ecosystem, thus achieving a more realistic understanding of future changes.

The field part of this scientific study was carried out in the Omacc | Marine Climate Change Observatory – Punta de Fuencaliente (ull.es) on the island of La Palma. In this enclave of the Canary Islands there is an acidified system, a natural CO₂ gradient₂, This creates areas very similar to the future scenarios predicted by experts from the Intergovernmental Panel on Climate Change (IPCC) and generated by excess atmospheric CO2. “Therefore, it’s as if we have the opportunity today to observe the different scenarios that await us due to ocean acidification,“ explains José Carlos Hernández, a marine biologist at the University of La Laguna. There are only two other volcanic areas in the world with similar characteristics: the island of Ischia in the Mediterranean Sea and Papua New Guinea in the Pacific Ocean, making them areas of great scientific interest.

The researchers also discovered high levels of taxonomic diversity in the acidified zones. This is mainly due to the presence of small, cryptic species that were previously undetected using traditional visual sampling techniques, such as tufted red algae and polychaetes.

Some of these species even possess calcified skeletons or shells, like small mollusks and echinoderms, indicating that they may be adapting to the future conditions predicted by the IPCC. Even so, although there is an increase in taxonomic diversity, there is a decrease in functional diversity, because acidification is causing the disappearance of species important to the ecosystem, such as crustose coralline algae or sponges that provide support and shelter to many species and are very characteristic of our benthic ecosystems.

In conclusion, the researchers highlight that subtropical benthic ecosystems will maintain high levels of biodiversity in an AO scenario, although they will tend towards miniaturization due to the predominance of small species of carpeting algae and epiphytes, and associated small invertebrates. This will lead to a homogenization of the community, with serious consequences by causing significant losses of ecosystem services.

Publication: González-Delgado S, Wangensteen OS, Sangil C, Hernández CA, Alfonso B, Soto AZ, Pérez-Portela R, Mariani S, Hernández JC. 2023 High taxonomic diversity and miniaturization in benthic communities under persistent natural CO disturbances. Proc. R Soc B 290: 20222417. https://doi.org/10.1098/rspb.2022.2417