Epiphytal foraminifera on Penicillus capitulae and exposed Thalassia rhizomes were monitored monthly from September 1994 to March 1996 in Long Haul Bay, Nevis, NE Caribbean Sea. Monitoring was disrupted by Hurricanes Luis and Marilyn in September 1995, six years after the previous hurricane. The change in the foraminiferal community was analyzed in terms of guilds, seasonality, foraminiferal numbers, and diversity.
Before Louis and Marilyn, the mean foraminiferal number on Penicillus capitulae was three times higher than on exposed Thalassia rhizomes and basal leaf bosses. After the hurricanes, the mean foraminiferal numbers on both plants increased and the mean foraminiferal number was six times greater on Penicillus capitulae than on Thalassia rhizomes. This was attributed to a reduction in predation or an increase in nutrient flux. Mean diversity, measured using the information function H, was greater on Thalassia rhizomes than on Penicillus capitulae, but did not differ on either plant before and after the hurricanes, nor did SHEBI detect an abundance biozone boundary coincident with the hurricanes. The hypothesis that hurricanes keep nearshore epiphytal foraminifera in a permanently pioneering sere is rejected.
The plants support three foraminiferal guilds: Guild I, a higher-energy guild intolerant of nutrient enrichment; Guild II, a guild of rapidly reproducing opportunists on short-lived substrates; and Guild III, a lower-energy guild tolerant of nutrient enrichment. The mean percentage abundances of the guilds were the same before and after the hurricanes. Thalassia rhizomes have a lifespan of three years, while Penicillus capitulae live for ~30 days. Time-series analysis found the monthly values of H and the percentage abundances of the three guilds on Thalassia rhizomes to fluctuate seasonally, H being low between November and May 1995 (the regional dry season). In contrast, H fluctuated from month to month on Penicillus capitulae. The lower diversity of the epiphytal foraminifera on Penicillus capitulae is a consequence of the plant’s short life span. The hurricanes’ impact on foraminiferal number but not on diversity accords with the diversity-stability hypothesis that predicts community resilience increases with species richness.
The hurricanes rejuvenated epiphytal foraminiferal numbers, probably due to nutrient influx from rotting marine vegetation or decreased predator populations. Thus, beach clean-up in the aftermath of storms may have deleterious effects on nearshore foraminiferal populations by removing nutrients. It is recommended that the longer-lived plant, in this case Thalassia, be the source of epiphytal foraminifera used in monitoring nearshore environments.