Fish Species Richness in Lowland Streams with a Geothermal Input Phenomenon, Sarapiquí de Heredia, Costa Rica

Jimena Golcher Benavides,Maurizzio Protti Quesada

doi:10.5402/2011/695492

Abstract

Lowland streams of the Caribbean Costa Rican slope are naturally enriched by minerals and solutes such as phosphorus, a phenomenon known as geothermal input. The resulting stream phosphorus gradient affects the food web by altering primary production, leading to complex biotic and abiotic interactions. The objective of this study was to describe fish species richness patterns in relation to a naturally occurring phosphorus gradient in three lowland streams. We hypothesized that phosphorus input in La Selva Biological Station streams is correlated with species richness. 354 individuals were identified at 4 sites: Surá, El Salto, Sábalo and Jaguar, using a cast net, a total of 150 throws were made, distributed in 10 samplings, at each site. An estimation of species richness along with alpha and beta diversity indices were calculated in order to describe fish community structure. Species richness was estimated to be higher at Jaguar but presents a lower phosphorus enrichment. Jaguar and Sábalo, differed the most while Salto and Surá were the most similar as indicated by species turnover among streams. There is a non significant relationship between phosphorus levels and diversity; however, this interesting trend encourages further studies on species richness patterns and natural nutrient enrichment of streams.

Highlights

Geothermal input is a hydrological phenomenon that has occurred in the Caribbean slope of Costa Rica for about 1.2 million years, in which volcanic activity in the valley causes natural contamination in the lowlands [1, 2]
Phosphorus, nitrate, and ammonia concentrations in stream waters have been monitored by a long-term project at La Selva Biological Station since 1988
This laboratory has shown that soluble reactive phosphorus (SRP) in streams can attain concentrations of about 400 μg/L

Summary

Introduction

Geothermal input is a hydrological phenomenon that has occurred in the Caribbean slope of Costa Rica for about 1.2 million years, in which volcanic activity in the valley causes natural contamination in the lowlands [1, 2]. Phosphorus, nitrate, and ammonia concentrations in stream waters have been monitored by a long-term project at La Selva Biological Station since 1988. This laboratory has shown that soluble reactive phosphorus (SRP) in streams can attain concentrations of about 400 μg/L. Particular attention has been given to the effects of geothermal input on primary producers, decomposers, and macroinvertebrates such as shrimps. Because of their role as primary consumers, macrovertebrates are important indicators of changes in the structure of the overall food web

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