Newswise — Human actions have caused significant harm to ecosystems and biodiversity worldwide, but there is a glimmer of hope for the future through ecosystem restoration. Researchers investigating the rejuvenation of underwater seaweed forests, crucial for nourishing and sheltering various species, have discovered that a decade of restoration endeavors has enabled a damaged forest to recover to a level of abundance and vitality similar to undisturbed forests.
Dr. Emma Cebrian, the lead author of the study published in Frontiers in Marine Science and affiliated with the Centre d'Estudis Avançats de Blanes, emphasized the significance of macroalgal forests, which are present on more than a third of the world's coastlines and serve as the foundation for entire ecosystems. The study focused on the restoration efforts carried out in the Bay of Maó, Menorca, in 2011, where a species of macroalgae was reintroduced to its former thriving habitat. The researchers observed that after a decade, the associated algal species returned to the area, accompanied by the reestablishment of ecosystem functions they provide.
Under the sea
In their study, Dr. Cebrian and her team employed a trait-based methodology to examine the functional restoration of seaweed forests. They aimed to establish a connection between the restoration efforts and the forest's ability to function similarly to its pre-damaged state. Specifically, the researchers focused on Gongolaria barbata, a critical "canopy-forming" species that plays a crucial role in sustaining seaweed forests. By investigating five different locations of this species, the team aimed to gain insights into how the restoration of such key species can contribute to the revitalization of the entire ecosystem.
Cristina Galobart, the study's first author, who is also affiliated with the Centre d'Estudis Avançats de Blanes, highlighted the significance of canopy-forming macroalgae among all seaweeds. She likened their role to that of trees in a terrestrial forest, as they provide essential structure to the ecosystem. By altering factors such as light and water flow, these macroalgae have a profound influence on the local environment. This, in turn, leads to the creation of ecological niches that can be exploited by other species, allowing them to thrive and benefit from these modifications.
In the assessment of restoration projects, particularly in marine ecosystems where such initiatives are less established, there is a tendency to focus on short timescales. However, projects involving slowly maturing species require longer durations for comprehensive evaluation. While we have gained understanding regarding the restoration of vegetation structure and species diversity, lingering questions remain regarding how an ecosystem regains its functional capabilities over time.
In order to assess the functioning of the ecosystem, it is crucial to examine quantifiable traits in the target species that reflect the overall health of the ecosystem. The research team opted to investigate a comprehensive set of 14 traits, including characteristics such as specimen size and the growth rate of species with longer lifespans or slower growth patterns. The presence of species that require more time to mature or grow larger can serve as an indicator of a healthier ecosystem, as it suggests that the environment is better equipped to support their needs.
The research team examined several distinct locations to gather data for their study. These included an actively restored locality, where restoration activities had been taking place for a decade, a nearby locality where the restored macroalgae had expanded beyond the initial restoration area, a neighboring locality that had not undergone restoration, and two reference localities that had remained undisturbed. Samples were collected from each location for further identification and analysis. Subsequently, the samples were dried and weighed to quantify the abundance of each species present.
The team's findings revealed that the restored locality exhibited a greater diversity of species compared to the untouched locality and the area where restoration efforts had spread beyond the initial boundaries. Interestingly, the restored locality showcased a similar species composition to the reference samples, indicating a successful restoration outcome. Furthermore, the restored locality exhibited a higher level of functional richness compared to one of the reference forests, even though it did not consist of the exact species that the scientists had initially anticipated.
The study highlighted that restored ecosystems may comprise different species compared to their original counterparts while still fulfilling similar ecological niches and supporting local biodiversity. The restored locality displayed enhanced structural complexity and encompassed species with longer lifespans, indicating a crucial sign of long-term recovery. This aspect is significant as it increases the potential for the seaweed forest to provide shelter and support to other organisms. Moreover, the increased diversity in the restored locality holds promising implications for the future. A more diverse seaweed forest has the potential to better respond to environmental challenges, ensuring its resilience and sustainability.
“We demonstrated that a single restoration action, plus the removal of the cause of degradation, can lead to the recovery of not only a single species but also the associated ecosystem functions,” said Cebrian. “Adding information from other restoration initiatives will help to completely understand how functionality is recovered in different habitats, species, or environmental conditions.”