Ecology of soil ciliates in a subtropical moist forest in Puerto Rico

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Authors

Acosta-Mercado, Dimaris

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University of Guelph

Abstract

Biodiversity and community dynamics of soil ciliates were studied in the Cambalache Subtropical Moist Forest (CSMF), Puerto Rico. The Edaphic Quantitative Protargol Staining (EQPS) method was designed to quantitatively assess ciliate species richness and abundance. Using EQPS, the effect of plant species, soil pH, ash content, and inorganic nitrogen on soil ciliate species richness and total ciliate abundance were studied under field conditions. Plants had a significant effect but the flush of total inorganic nitrogen was a better predictor variable.;Two experiments tested the effect of slurries derived from species-rich Canella soils on ciliate communities in the species-poor Tectona soils, and vice-versa. Reciprocal soil slurries had no detectable effect on overall ciliate species richness and abundance; however, bacterial slurries containing autochtonous bacteria did have a significant effect on the species richness of the soil endemic colpodean ciliates. Thus, bacterial divesity or abundace may have a strong influence on the diversity and possibly abundance of rhizosphere ciliates.;An eight-month study was undertaken to study fluctuations species in ciliate diversity, abundance, soil inorganic nitrogen, and microbial biomass C among three plant species. Overall composition of ciliate species showed high variation from month to month and no soil ciliate species assemblages were found. Temporal fluctuations in soil ciliate species richness and abundance were similar among the three plant species. The flush of total inorganic nitrogen was again the best predictor variable, but the effect of microbial biomass C was also significant.;The low abundance of soil ciliates in the CSMF (i.e., 0.5--103 individuals g-1 dry wt soil) suggested that their contribution to the ecosystem could be minor. However, mean soil ciliate biomass (41, 854 +/- 37, 055 pg C g-1 dry wt soil) and production (1.1 kJ m-2yr-1 or 21.7 m -3 yr-1) were comparable to estimates for aquatic ecosystems. Assuming a ciliate growth efficiency of 40%, ciliate nutritional demand on the microbial biomass was estimated to be 0.002%, suggesting that their contribution to secondary production may not be as important as has been reported for temperate soil ecosystems.

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Keywords

Puerto Rico, Ecology, Soil ciliates, Cambalache Subtropical Moist Forest, Edaphic Quantitative Protargol Staining

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