Cabrera loses nearly 40% of its marine diversity in a decade

A study based on sampling the seabed and analyzing it using advanced genetic techniques has detected a decline of approximately 40% in species diversity in Spain’s two national parks with marine domains: the Cabrera Archipelago National Park (south of Mallorca) and the Atlantic Islands National Park (Galicia, in the Atlantic Ocean).

The data, collected over nearly a decade, show that even marine protected areas are not immune to the loss of biological richness.

The research, carried out by scientists from the Blanes Center for Advanced Studies (CEAB-CSIC) and the University of Barcelona (UB), has been published in the scientific journal Diversity and Distributions. It is based on repeated sampling of the same seabed habitats, ranging from shallow, well-lit areas dominated by algae and other photosynthetic organisms, to deeper communities with less light and a greater presence of sponges and other invertebrates, as well as even deeper detrital bottoms formed by sediments and calcareous algae. Sampling was repeated at the same sites between 2014 and 2022.

Once the samples were collected, the research team analyzed them in the laboratory using advanced genetic techniques. They extracted the DNA present and amplified marker genes. By comparing the fragments that act as a “genetic fingerprint” with information from major international genetic databases, they were able to identify the species present, including many that would be practically undetectable using traditional methods. This approach made it possible to analyze a huge amount of genetic information and identify thousands of different life forms, with about 5,500 species-equivalent units and nearly 27,000 genetic variants, a resolution that allows even very subtle changes in marine communities over time to be detected.

The data obtained in this research provide clear evidence of a significant loss of biodiversity. Comparing the first years of monitoring (2014–2015) with the most recent ones (2021–2022) shows that species richness has declined by around 40% on average in the two marine national parks studied.

The decline is observed across the different seabed habitats analyzed, although with varying intensity depending on depth, community type, and biogeographical region. In this sense, the communities of the Cabrera Archipelago park in the Mediterranean and those of the Atlantic Islands park in the Atlantic Ocean show their own compositions and dynamics, shaped by the environmental context of each sea, but they share the same trend of biodiversity loss over time.

Xavier Turon, a researcher at CEAB-CSIC and the lead author of the study, explains: “Not only have we observed this very clear and worrying trend of declining species diversity in both parks, but we have also detected changes in population structure and composition.”

The research team emphasizes that although protection significantly reduces local pressures, national parks are not isolated from their surroundings and also respond to the effects of global change driven by human pressures. Precisely because they are less affected by local impacts, these areas become privileged observatories for detecting environmental change at an early stage.

In this context, the study highlights the importance of incorporating advanced genetic techniques, such as metabarcoding and metaphylogeography, into long-term biomonitoring programs. Having robust time series makes it possible not only to assess the state of marine ecosystems, but also to anticipate impacts and more effectively guide conservation and nature-restoration policies and actions.

Metabarcoding is a technique that allows organisms to be identified from DNA fragments present in an environmental sample. Instead of analyzing species one by one, this methodology provides a relatively fast and comprehensive overview of ecosystem diversity.

Traditionally, metabarcoding has been used mainly to describe biodiversity at a specific point in time, like a snapshot. The novelty of this study is that it applies this tool as a long-term biomonitoring instrument, that is, to compare samples collected in the same places over a number of years.

“When we started this research, the use of metabarcoding for temporal monitoring was very uncommon, especially in marine benthic communities,” notes Xavier Turon. “This has resulted in a significant gap in knowledge about the temporal dynamics of biodiversity.”

This approach opens the door to incorporating genetic techniques as a key component of official environmental monitoring programs, providing detailed and objective information on how ecosystems evolve, far beyond what is directly visible.