Benthic Surveys in Culebra, Puerto Rico: comprehensive assessment of seagrass community structure and demography from transect surveys conducted in 2014 and 2022

This record provides seagrass habitat metrics collected in 2014 and 2022 at 13 monitoring stations in Ensenada Honda and Puerto Manglar in the island of Culebra, Puerto Rico, as part of Culebra's Ridge-to-Reef Monitoring and Evaluation Framework to assess the effectiveness of the NOAA strategies and actions in priority watersheds to reduce land-based sources of pollution (LBSP) impacts to the nearshore marine ecosystems of the island. Metrics include benthic cover of: total seagrasses, seagrasses by species, macroalgae, coralline algae, scleractinian corals, sponges, and sand/sediments, short shoot densities, and epiphyte relative abundance.

At each monitoring station, three replicate 30 meter transects were set up, oriented perpendicular to shoreline and extending offshore. A 0.25 m2 PVC sampling quadrat (50 cm x 50 cm) divided into 25 grid units (10 cm x 10 cm each) was used to estimate attributes of the seagrass community within each of 30 quadrats sampled contiguously (one at each meter mark) along each 30 m transect. Transect #2 was extended to the edge of the bed and seagrass community attributes were recorded within four quadrats placed equidistant from the 30 meter mark to the edge of the bed. Within each 0.25 m2 quadrat. seagrass community attributes were recorded implementing visually estimated Braun Blanquet (1932) index scores. Seagrass habitat metrics recorded included:
1- Total seagrass cover by species (i.e., Thalassia testudinum, Syringodium filiforme, Halodule wrightii, and Halophila stipulacea). Halophila was recorded as an individual seagrass species, but not considered in the total seagrass cover score.
2) Total cover of macroalgae, calcareous algae, sponge, corals, and sediment and/or rubble.
3) Epiphytic load index.
4) Short shoot densities (# shoots/100 cm2); collected within a single randomized 100 cm2 (10 cm x 10 cm) grid box within each quadrat along the 30 m transect.