Seagrass beds are considered ocean rainforests. They are some of the richest marine ecosystems and play an important ecological role in the world of the seas and oceans. Globally, however, seagrass meadows are declining, with a species of seagrass in the genus Zostera, known as eelgrass. Oomycetes, organisms that live in water and on land and feed either as parasites or from the dead remains of other organisms, are responsible for this decline. However, it is still unclear what role they play in the global decline of seagrasses. The impact of oomycetes on seagrass decline has been investigated by scientists from the Faculty of Forestry and Wood Technology.
The main causes of eelgrass decline include human activity and the so-called wasting disease caused by the oomycete Labyrinthulomycete Labyrinthula. “Oomycetes are organisms similar to fungi, but they are not related to fungi as such, they are related to brown algae and diatoms,” explained Anna Hýsková from the Institute of Forest Protection and Hunting. Recent studies have shown that oomycete pathogens from the genera Phytophthora and Halophytophthora are able to infect these seagrasses, causing lesions, disrupting the grasses and reducing the germination of their seeds. Scientists will study the diversity of oomycetes in different habitats, test their aggressiveness and determine if the most aggressive oomycetes are non-native ones.
Scientists collected samples of seagrasses, mangroves or leaves that had fallen into the water from the Mediterranean habitats of Sardinia and the Atlantic maritime forests of Mauritania in northwest Africa. “From the plant samples collected, pure cultures of the oomycetes present are obtained by isolation methods. Once identified, we are then able to determine their marine diversity,” Hýsková described. Subsequently, the scientists will work with Portugal’s Centro de Ciencias do Mar to conduct pathogenicity tests on the most common oomycetes isolated from dead seagrasses. These will clarify whether these are serious seagrass pathogens that could negatively affect the recovery of marine ecosystems such as kelp forests or seagrass meadows. They also plan to sample kelp forests in Atlantic coastal habitats in Portugal and Brazil this year.
“Pathogens of the genus Phytophthora are well known for their destructive power, causing devastating epidemics in terrestrial ecosystems, and in watercourses they are able to live off leaves that fall into watercourses. Halophytophthora species are generally described as saprophytes in mangrove forests, estuaries and marine ecosystems,” the scientist explained. Saprophytes are organisms that feed on decaying organic matter.
The main task of the Mendel University in Brno research team in the international RESTORESEAS project is to reveal the diversity, distribution, origin and pathogenic role of oomycetes in different marine ecosystems and connected freshwater and brackish waters. Brackish water has a salt concentration between freshwater and seawater. The project started last year and will continue until 2025. In the future, the research team plans to investigate the link between the diversity of seagrass oomycete habitats in brackish waters and the diversity of oomycetes in freshwater habitats. It also plans to investigate the diversity of oomycetes in the watercourses of the Czech Republic.
Contact for further information: Ing. Anna Hýsková, +420 605 786 520, xhyskova@mendelu.cz, Department of Forest Conservation and Hunting LDF MENDELU
On the photo: Collection of dead seagrass leaves on the coast