Field Procedures:

At each station, two replicate cores were used for estimates of above- and below-ground biomass following percent cover observations. A 15 cm inner diameter (ID) core was used to sample the seagrass species present (Thalassia, Halodule, Syringodium, Ruppia or Halophila) present within each quadrat. A PVC (polyvinyl chloride) core was used for the collection of below-ground and above-ground material. Care was taken to keep only the shoots that reside within the diameter of the core. Following placement of the 15 cm core on the seabed, the rubber stopper was removed from the top of the core. Before pressing the core into the sediment, the diver ran their fingers carefully around the bottom of the core. If grass was pulled under the core, it is removed. The diver pressed and twisted the core down into the sediment (10-15 cm depth). The stopper was re-installed in the 15 cm core, and the core was rocked back and forth. The diver worked their hand under the core and removed it from the grass bed, making sure to keep their hand under the bottom of the core in order to prevent loss of sample.. Samples were then placed in pre-labeled Ziploc bags and immediately placed on ice.

Laboratory Procedures:

Cores samples were kept in a refrigerator (4°C) until processing within one week of collection. Cores samples were sieved with filtered seawater through a 500 µm sieve to remove excess sediment. Seagrass tissue was carefully separated from infauna and shell harsh before further processing.

Prior to processing the samples for above- and below-ground biomass, we measured blade morphometrics (width and length) to nearest millimeter of up to six blades for five random shoots. Aboveground tissue, including leaves, sheath material and floral parts, were separated from all below-ground tissues. Leaves were carefully cleaned of all attached biota by scraping with a wet cloth or razor blade prior to analysis. All shoots were counted and scaled to the core area in order to obtain accurate estimates of shoot density. The below-ground and above-ground tissues were then placed in separate aluminum envelopes for drying. Sample labels included information on site, species, date collected, shoots or R/R, and number of shoots. Any dead plant material was discarded prior to drying. The live tissue (shoots, roots, and rhizomes) were dried to a constant weight in a 60°C oven and weighed to the nearest milligram. The drying process usually took 3-5 days. Lastly, the dry weight biomass for above- and below-ground tissues was used to calculate a root:shoot ratio.

shoots.csv