Dataset: Thalassia testudinum seagrass weights from biomass cores collected across the Western Atlantic from from March to May 2023 (Tropicalization Seagrass Beds project)

50 small seagrass (all comprised of one species, Thalassia testudinum) plots (0.25m2) were established at 13 shallow sites in the Western Atlantic. Each plot was assigned to one of ten treatments comprising a factorial manipulation of caging, nutrient supply, and canopy clipping: (1) control (2) partial cage (3) full cage (4) added nutrients (5) added nutrients + partial cage (6) added nutrients + full cage (7) full cage + half canopy clip (8) full cage + full canopy clip (9) full cage + added nutrients + half canopy clip (10) full cage + added nutrients + full canopy clip. After the experiment (approx. 1 year) 15cm diameter biomass cores were taken in each plot. To do this, the core was carefully placed over the seagrass and lowered to the sediment surface. The core was then inserted into the sediment (approx 10cm) using a twisting motion to sever belowground rhizomes. The core was then carefully removed and all captured above and belowground vegetative biomass was placed into a mesh bag and gently rinsed underwater. In the lab, the aboveground green leaf material was separated from the belowground material using a razor blade. Leaf material was also scraped clean of any epiphyte loading. Above and belowground material was dried separately in aluminum tares in a 60C oven. Any additional macroalgae found inside the core was also separately dried.