Dataset: Zostera seeds

To quantify the average shoot density of Z. marina in each bed as well as the ratio of flowering to vegetative shoots, six 0.063 m2 quadrats were haphazardly placed over vegetated substrate, and all seagrass shoots present within each quadrat were removed by the roots. Z. marina flowering and vegetative shoots were separated and counted in the lab. Sampling occurred in May 2014, when the flowering season was determined to be at its approximate peak based on observations of flowers in the region, and when water temperatures reached the optimal range for flowering, 20-21oC (Moore & Short, 2006).

To sample the distribution and density of seeds at specified positions within each bed, 10-cm diameter sediment cores were taken to a depth of approximately 10 cm, as Z. marina seeds are generally buried no deeper below the sediment surface (Morita et al., 2007). Sediment core samples were collected in July 2014, after the flowering season had ended and sufficient time had passed for all seeds to settle. In continuous beds, two transects ran from the center of the bed to the edge. The first transect direction was selected haphazardly, with the second being approximately perpendicular to the first. In each transect, one core sample was taken at the starting point, located at the approximate center of the bed; a second core sample was collected halfway between the center and the edge of the bed, the location of which differed for each bed based on its size; and a third core sample was taken at the edge of the bed.

In fragmented beds, one core sample was taken within each of two different vegetated patches near the center of the bed; within each of two vegetated patches along the edge of the bed; within each of two bare, unvegetated areas in the interior region of the bed; and in each of two bare areas along the edge of the bed (i.e., 8 cores per bed; Fig. 1C.). In both continuous and fragmented beds, two additional transects were used to sample directly outside of the bed. These transects ran perpendicular to the edge of the bed, and one core sample in each transect was collected at the following distances away from the edge of the bed: 0, 2.5, 5, 7.5, 10, and 15 meters.

Each core was wet-sieved in the field in 400-micron mesh bags to wash away sediment. Remaining coring contents were taken to the lab where they were frozen until processed, which involved individually examining them under a dissecting microscope. Any seeds, whether they were fully intact or the casing of an already germinated or dead seed, were identified and counted. Z. marina and H. wrightii shoots in each core were also counted.