Thermal stress is associated with fragmentation of Mediterranean Posidonia oceanica meadows

• DOI: 10.1002/gcb4.70031

Posidonia oceanica meadows, which underpin Mediterranean coastal ecosystems, are undergoing accelerated decline, partly driven by thermal stress. While previous quantitative studies have identified temperature thresholds beyond which seagrass mortality increases sharply, we show the cumulative and sublethal impacts of prolonged warming under fluctuating subthreshold conditions. To capture these effects, we introduce Stress Degree Days (SDD), a physiologically grounded index derived from an experimentally validated mortality rate function. Using sea surface temperature (SST) data, we quantified the cumulative thermal exposure across the Mediterranean Basin from 2000 to 2020. Leveraging high-resolution satellite imagery and deep learning-based habitat mapping, we linked SDD-derived thermal exposure to meadow fragmentation, which is a proxy for seagrass health. Our results show that high thermal stress (>50%) is concentrated along the southern and eastern Mediterranean, where meadows exhibit more than 40% cover loss and elevated fragmentation, even though maximum SSTs remained below lethal limits LT50=28.9 °C). This finding highlights the critical role of chronic sublethal thermal stress in driving structural degradation. Future projections under the RCP8.5, 'business as usual,' and the more moderate RCP4.5 climatic scenarios indicate basin-wide regression, with expected cover losses of approximately 80% and 40%, respectively, by 2100, and near-total habitat suitability collapse in the southern regions. Consequently, fragmentation indices are projected to double or triple, further disrupting clonal connectivity, sediment retention, and oxygen export. In summary, by integrating physiological mechanisms, large-scale remote sensing, and climate modeling, the SDD framework identifies thermal hotspots, reveals emergent vulnerability patterns, and offers a predictive tool to guide conservation strategies in warming oceans.

Available as a bioRxiv preprint: https://doi.org/10.64898/2026.02.23.707362

• Artículo completo

Related research projects

CHANGE-ME

Complex Ecological Systems and tHeir Resilience to GlobAl ChaNGE: Marine Coastal Ecosystems and Plant Epidemics

I.P.: Damià Gomila, Manuel Matías

Description

MdM-IFISC-2

Maria de Maeztu 2023-2026

I.P.: Ernesto Estrada, Ingo Fischer, Emilio Hernández-García, Rosa Lopez, Claudio Mirasso, Jose Javier Ramasco, Raúl Toral, Roberta Zambrini

After 15 years of its existence, IFISC can point to a proven track record of impactful research. The previous 2018-2022 MdM award has significantly enhanced the institute's capabilities, as demonstrated by an …

SEDIMENT

SEagrass DIversity in the MEditerranean basin in a global change scenario: a machine learNing approach from saTellite images

I.P.: Manuel Matías, Tomás Sintes

The main challenge of this project is to correlate the changes in the sea surface temperature (SST) in the Mediterranean basin with the spatial distribution and size of different seagrass species. We …

CYCLE

Complex DYnamics of CoastaL Ecosystems: Resilience to Climate Change. Modelling and Simulations.

I.P.: Damià Gomila, Tomás Sintes

Complex Dynamics of Coastal Ecosystems: Resilience to Climate Change (CYCLE) is a coordinated multidisciplinary research project that brings together the efforts of experts in the fields of marine ecology and the physics …

Noticias relacionadas

Invisible cumulative thermal stress is fragmenting Posidonia oceanica meadows across the Mediterranean

2 de julio de 2026

A new study, co-led by researchers from IFISC (CSIC-UIB) and CEAB-CSIC, demonstrates that prolonged warming degrades seagrass meadows even when temperatures remain below lethal limits.The research leverages artificial intelligence and high-resolution satellite imagery to link chronic thermal exposure to cover …

L'estrès tèrmic acumulat fragmenta les praderies de Posidonia oceanica en tot el Mediterrani

2 de julio de 2026

Un nou estudi realitzat per investigadors de l’IFISC (CSIC-UIB) i el CEAB-CSIC demostra que l'escalfament prolongat degrada les praderies de plantes marines fins i tot quan les temperatures es mantenen per sota dels límits letals.La recerca aprofita la intel·ligència artificial …

El estrés térmico acumulado está fragmentando las praderas de Posidonia oceanica en todo el Mediterráneo

2 de julio de 2026

Un nuevo estudio realizado por investigadores del IFISC (CSIC-UIB) y el CEAB-CSIC demuestra que el calentamiento prolongado degrada las praderas de plantas marinas incluso cuando las temperaturas se mantienen por debajo de los límites letales.La investigación aprovecha la inteligencia artificial …