Quantification of epiphyte biomass accumulation on artificial seagrass leaves in Culebra, Puerto Rico

This record provides estimates of epiphyte biomass accumulation on artificial seagrass leaves at 13 monitoring stations in Ensenada Honda and Puerto Manglar in the island of Culebra, Puerto Rico.

Currently the island of Culebra is implementing a ridge-to reef-monitoring to assess Land-based sources of pollution (LBSP) mitigation success and identifying adaptive management needs. The goal of this study was to test whether metrics of epiphyte load accumulation on seagrass leaves can be used as a biological response indicator for nutrient impacts on Culebra's nearshore habitats. More specifically identify the presence of spatial patterns and examine potential linkages with nearshore water quality conditions in locations where upland watershed restoration interventions have been implemented vs. locations where no interventions have been conducted.

Artificial seagrass installations were deployed at 13 nearshore fixed monitoring stations downstream from select coastal watershed drainage delivery points, and co-located with water quality, sediment trap, and seagrass monitoring stations. These sites were selected to represent: 1) Repeat locations where nearshore water quality and sedimentation are being monitored. 2) Repeat locations previously sampled in 2014 for water quality and seagrass community status assessment. Epiphyte accumulation was quantified on artificial seagrass following the methods outlined in Virnstein & Curran (1986) with slight modifications At each monitoring station three replicate shoots containing 6 blades each (2 each, approx. length: ~23cm, ~13cm, and ~8cm; approx. width: ~1cm) attached to plastic augers were deployed. Augers were inserted into the substrate and anchored to existing (previously installed) rebar markers. The experiment was run twice and installations remained underwater for 60–90 days: 1) 7 Aug, 2023–7 Nov, 2023; and 2) 11 Dec, 2023–5 Feb, 2024. Recovered artificial leaves were carefully rinsed in fresh water to remove salt, gently scraped with a blade, and scraped material dried at 60 degrees celcius to constant weight. Artificial leaf dimensions were measured to the nearest 0.5 mm and the quadrangular (rectangle / trapezoid) leaf surface area was estimated accordingly. Recovered shoots that were frayed or tattered were discarded and excluded from analyses. Mean epiphyte biomass accumulation was computed in mg/cm2/day