Biometric measurements (shoot density, leaf width, leaves per shoot and leaf area) carried out in the Zostera noltei meadows along the Mira channel of the Ria de Aveiro lagoon throughout 2020.

Biometric measurements of four colonizing Zostera marina patches in the Mira channel of the Ria de Aveiro from December 2019 to August 2020 Description Biometric measurements of four colonizing Zostera marina patches (shoot density, seagrass coverage, leaf width, number of leaves per shoot and leaf surface area) were taken in the Mira channel of the Ria de Aveiro from December 2019 to August 2020. The seagrass coverage was measured in each patch by recording species presence using a metal frame of 50 × 50 cm divided into 25 sub-quadrats of 10 × 10 cm (n= 4). Shoot density was calcu lated by counting the number of vertical rhizomes of each patch into 4 sub-quadrants per each quadrant of 50 × 50 cm (n=4). Then, shoot density per square meter was calculated. Four shoots per quadrant were selected to measure leaf length, leaf width and the number of leaves per shoot and to calculate leaves per shoot and leaf surface area. Seagrass measurements were always done during low tide periods.

Wrack accumulations are a source of nutrients on sandy beaches and host invertebrate species, increasing local biodiversity. The distribution of these important accumulations varies in space and time depending on the environmental conditions of the area and the biological factors of the species that compose it. Consequently, this spatio-temporal variability in the wrack accumulations remains poorly understood in some regions. This database compiles the monthly variability in dry weight biomass of six seaweed taxa(Saccorhiza polyschides, Fucus spp., Ascophyllum nodosum, Cystoseira spp., Ulva spp. and Sargassum muticum) which forming the wrack of four sandy beaches in the northern Portugal (Âncora, Cabedelo, Paramos and São Pedro de Maceda)through a year.