CALIBRATING LIVE-DEAD MISMATCH IN EPIPHYTIC FORAMINIFERAL ASSEMBLAGES

Live-dead mismatch, the disparity between diversity indices of living assemblages (LAs) relative to modern death assemblages (DAs), has been successfully used to evaluate anthropogenic change in coastal marine ecosystems. The utility of using the live-dead mismatch of epiphytic foraminiferal assemblages to detect change in seagrass habitats is, however, limited by the following factors: (1) traditional methods of processing epiphytic forams destroys fragile tests; (2) many species of epiphytic forams possess agglutinated (non-biomineralized) tests that are rarely, if ever, preserved in modern death assemblages; and, (3) reproductive events (multiple fission and/or gametogenesis) can result in the partial or complete destruction of the parental test.

Traditional methods of processing epiphytic forams involve scraping tests off seagrass blades and sieving the surviving debris. The scraping process destroys fragile encrusting species like Cornuspiramia antillarum and Rhizonubecula adherens which possess lightly calcified, branching tests. C. antillarum, in particular, has been shown to dominate epiphytic communities in waters with increased nutrient levels. The sieving process winnows the epiphytic population, preferentially removing reproductive propagules and juveniles. Several common epiphytic species, such as Iridia diaphana, Hemidiscella palabunda, and Sagenina frondescens, possess agglutinated tests with organic cements that disintegrate shortly after death. Reproduction by multiple fission can result in the complete destruction of the parental test in Planorbulina acervalis and Planogypsina squamiformis, and in the partial destruction of the parental test in Sorites dominicensis and Archaias angulatus. Tretomphalus, and related taxa, produce gas-filled balloon chambers during gametogenesis, detach from their phytal substrate, and passively drift away.

If live-dead mismatch between epiphytic foram LAs and DAs is to be used to evaluate changes in seagrass habitats, then researchers need to use methods that minimize the bias introduced by sample processing. Examining fresh blades under the microscope yields more accurate information about live assemblages of epiphytic forams, their population structure, and their diversity, abundance and distribution.