Sea temperature rise causes ʻPosidonia oceanicaʼ seagrass flowering
Some studies described a declining situation for the future of the Posidonia oceanica species in peninsular coasts due the effects of the sea temperature rise. This new study -the first experimental evidence on an uncommon phenomenon- describes an unknown resource of the Posidonia that would allow it to adapt to environmental changes in a more versatile way and would therefore increase its survival possibilities regarding warmer sea temperatures, caused by the climate change. Other teams that took part in the study are the Spanish Oceanographic Institute (IEO), the Blanes Centre for Advanced Studies (CEAB-CSIC) and the Zoological Station Anton Dohrn in Naples (SZN, Italy).
A marine plant covering the Mediterranean sea beds
Posidonia oceanica is an endemic marine seed plant in the Mediterranean. Its slow growth restricts its ability to adapt to environmental changes, and this plant creates dense seagrass that can be found at depths of forty meters. This marine plant creates a marine habitat with a high primary production and plays an important role for marine species (food, shelter, reproduction, etc.). Posidonia reproduces similarly to terrestrial plants: in a vegetative way (asexually) or producing flowers and fruits (sexually), an uncommon phenomenon that can occur in autumn.
In the study, marine plants from the Catalan coast seabeds were put under thermal stress in the laboratory (similar to the one caused by heatwaves in the marine environment, which are more common in the Mediterranean coast due the climate change). At the end of the experiment, carried out in the Murcia Oceanographic Center laboratories (IEO), an important part of the plants that had been warmed up had flowered, while those under a standard temperature did not develop any inflorescence.
When temperature causes Posidoniaʼs flowering
These innovative results prove that temperature is a primary factor able to alter the reproductive behaviour and cause flowering in this marine plant. It also verifies the relation between the observations of this speciesʼ flowering and the heatwaves, described in previous studies but only in a correlational way.
According to the lecturer Javier Romero (UB-IRBio), “the deeper we get into the study of the behaviour of living beings under global warming, the more we realize about the complexity of their responses”. Regarding the Posidonia, flowering induction due thermal stress involves an increase of genetic diversity, and therefore, a larger resilience. “However -says the expert-, considering the slow rhythm of its growth, colonization and spreading, and the pace of global warming, this turns into a kind of race, with an uncertain result”.
Juan Manuel Ruiz, IEO researcher and first author of the study, states that “We should check whether these phenomena are enough to fight the effects of warm water and other human impacts in the upcoming decades but it allows us having some hope for the survival of the P. oceanica seagrass in the Mediterranean coast, a millennial habitat accounting for the basis of the functioning of the coastal marine ecosystem in the Mediterranean”.
The new study is part of the RECCAM research project (Seagrass Meadows resilience to global warming: an analysis based on responses at ecophysiological, population and ecosystem levels), coordinated by the University of Barcelona, with the participation of IEO and CEAB-CSIC, apart from the collaboration of the Zoological Station Anton Dohrn. RECCAM aims to analyse the response of Mediterranean marine phanerogams regarding the effects of global warming in one of the most threatened ecosystems, and with the highest ecological value in the Mediterranean.