The time-series dataset includes flowering data (presence/absence of flowers) of Posidonia oceanica meadows across 58 sites in Greece, covering the period from 2007 to 2021. For each site and and year within the study period, the following variables are also provided: Maximum sea surface temperature during summer, cumulative intensity of summer marine heatwaves, maximum intensity of summer marine heatwaves and heatwave category (Moderate - Extreme).

Data time-series of ~20 years (1997-2018)of seagrass Posidonia oceanica annual production covering sixty sites across the Greek Seas. For the same time period, annual sea surface temperature and sea surface temperature of August data are also given.

The dataset includes time-series data on the annual production of the seagrass Posidonia oceanica from 2007 to 2021, covering nine sites across the Greek Seas. During the same period, satellite- derive records of annual sea surface temperature, sea surface temperature of summer (average for July to September)and maximum sea surface temperature are also provided.

In the framework of Action 2.1 "Data from aquatic (marine and terrestrial) ecosystems related to climate change", the Photo-Catalytic Processes and Environmental Chemistry group of the Institute of Nanoscience and Nanotechnology of the National Centre for Scientific Research "Demokritos", focused on the study of the history of harmful algal blooms in aquatic ecosystems of Greece. One of the effects of climate change is the more frequent occurrence of harmful algal blooms in surface waters, which are mainly favored by the global warming, the eutrophicatio...