Abundances of individual eelgrass mesograzer species on Artificial Seagrass Units (ASUs)

To examine the relative importance of bottom-up and top-down control of the eelgrass (Zostera marina) mesograzer community, nutrients (2 levels) and predators (3 levels) were manipulated in a full factorial experimental design (n = 10 replicates per treatment combination) for seven weeks (June 17 – July 28, 2011). 60 artificial seagrass units (ASUs) were randomly arranged in three rows, parallel to the shore in the subtidal Z. marina zone, and distributed such that ASUs were separated by 3 m within and between rows. ASUs were made of frayed rope (length = 35 cm) to mimic seagrass or branching algal habitat, and were used to sample mesograzers on a standard surface area. This data file gives the abundances of the eight mesograzers on ASUs for each treatment. Cage.Trt: the predator exclusion cage treatment (full = full cage/predator exclusion; partial = partial cage/predators have access/cage control; none = no cage/predator have access/control). Nut.Trt: the nutrient addition treatment (0 = no nutrients added; 1 = nutrients added (30 g Osmocote slow release fertilizer))

Water column nutrient concentrations in response fertilizer addition

We experimentally tested the effectiveness of slow release fertilizer (Osmocote) for increasing nutrient concentrations at the scale of our replicates and not in adjacent replicates 3 m away. Plot: plot ID. nutrient trtm: nutrient treatment (Y = fertilizer satchel added; N3 is 3m away from fertilizer satchel, N7 = 7m away from satchel to measure ambient nutrient concentrations). dist.to.satchel.m = distance from fertilizer satchel in meters. init.nut.weight is dry mass of fertilizer pellets in g before placing it in the field, fin.nut.weight is final dry mass after three days at the study site. PO4.uM, SiO2.uM, and NOx.uM are nutrient concentrations measured in uM