Seagrass characterization on the southern Pacific coast of Costa Rica: history, vegetation, and environment

Seagrass conservation and management requires scientific understanding of spatial and temporal variability, information that is currently limited for the Eastern Tropical Pacific (ETP). Here, we analysed seagrass presence based on previous reports, herbarium collections and stakeholder knowledge, combined with field characterization in Golfo Dulce, southern Pacific coast of Costa Rica. Seagrasses were found at multiple locations along a narrow border close to shore and in up to 6 m depth within Golfo Dulce, dating back to 1969. Two seagrass species were found, Halophila baillonii and Halodule beaudettei. Seagrass biomass values for Golfo Dulce (12.0 +/- 8.5 g DW m(-2)) were lower and water nutrient concentrations were higher than previously reported in the gulf. Shoot density (1513 +/- 767 shoots m(-2)) was similar to previous reports. Stable isotope values in seagrass were -11.3 +/- 1.0 parts per thousand delta C-15 and 1.2 +/- 0.9 parts per thousand delta N-15; while those in sediments were -26.1 +/- 1.3 and 2.5 +/- 0.9 parts per thousand. In Golfo Dulce, isotopic values of both seagrass species do not overlap with other known primary producers. Management strategies should aim to minimize known seagrass stressors, protect potential seagrass habitat, and take into account the dynamic life strategies of the two seagrass species found.