Zostera marina meadows in the northwestern Spain: distribution, characteristics and anthropogenic pressures

Abstract

Zostera marina meadows represent an important marine ecosystem in the North temperate region. They are common in the northwestern Spain, but their distribution and biological traits remain poorly studied. Improving the knowledge of eelgrasses and identifying potential impact sources is necessary to implement conservation programs. Distribution, cover, density, size and presence of flowers in plants of Z. marina along the northwestern Spain were studied. Furthermore, we analyzed shifts in their distribution, the major human-mediated pressures (shellfishing activities) and their protection status. The study area was divided in 14 sectors that were sampled between 2014 and 2017. The northwestern Spain hosts the majority (61.5%, covering 5.8 km2, 48 meadows) of the total extension of Z. marina meadows in the Iberian Peninsula. Our study revealed 13 meadows that were not recorded before. Conversely, the disappearance of seven previously reported meadows was detected. Cover and density of Z. marina was 51.2% ± 15.1 (n = 180) and 181.1 shoots m−2 ± 79.6, respectively. Length and width of leaves were 41.9 cm ± 13.2 (n = 1800) and 6.3 mm ± 0.7, respectively. Although 98% of Z. marina meadows (5.7 km2) were located within marine protected areas, 80% of the meadows (4.7 km2) are subjected to anthropogenic pressures related to shellfishing activities. Z. marina meadows from the northwestern Spain are particularly relevant for the conservation of the species at its southern distribution limit and specific conservation and monitoring plans should be implemented to ensure its persistence. We propose 15 meadows to be considered in future conservation plans that were selected among the ones not included at present in protected areas, and considering their vulnerability and the presence of other species with interest for conservation.