Resurgence of Zostera marina in the Ria de Aveiro lagoon, Portugal

Seagrasses provide important services to coastal ecosystems and mankind. Even though seagrasses have been seriously threatened in Europe from the 1970s, a recent study suggests that they are expanding in extension since the past few decades. Here, we add a new case to this reverse trend of seagrass decline, showing the resurgence of several patches of Zostera marina in the Ria de Aveiro lagoon. In the past, this seagrass disappeared on numerous occasions, especially due to dredging activities and its use for agricultural purposes. The last record of the species in the area was a decade ago, when small patches became extinct after a long period of heavy storms. Now, a decade later, nine patches of Z. marina were identified in the Mira channel, inhabiting a much wider area than that occupied prior to its extinction. Although in periods of low tide some patches were submerged in pools and others were exposed to the air, this fact did not cause differences in the eelgrass biometrics and flowering effort. All the patches formed several sexual spathes, suggesting that the eelgrass could form seed banks in the sediment. However, due to this species vulnerability to environmental changes and human activities, further studies are required to determine long-term reproductive success and survival in the Ria de Aveiro.