Effects of macroconsumers on benthic communities: Rapid increases in dry-season accrual of calcium in a tropical karst stream.

Elaine Cristina Corrêa,Fabio De Oliveira Roque,Franco Leandro De Souza,Alan Paul Covich,Jonas De Sousa Correa,Ryan Michael Utz,Miguel Cañedo-Argüelles Iglesias

doi:10.1371/journal.pone.0209102

Abstract

Species loss from upper trophic levels can result in some major changes in community structure and ecosystem functions. Here, we experimentally excluded macroconsumers (e.g., fish and shrimp) in a Brazilian karst tropical stream during the dry season to investigate if their loss affected the accrual of calcium, dry mass (DM) and ash-free dry mass (AFDM) of sediment, benthic invertebrates, and chlorophyll-a. We found that the exclusion of macroconsumers decreased accrual of calcium. The absence of fish and shrimp may have promoted increased grazing by mayflies and snails in the electrified treatment as expressed by the depressed calcium accrual and shift in periphyton community composition. However, the exclusion of macroconsumers had no effect on DM and AFDM, chlorophyll-a, or total abundance of invertebrates. Our findings shed new light on the impact of macroconsumer loss and consequences for calcium accrual in karstic streams.

Highlights

Human activities can disproportionally affect macroconsumers in the upper trophic levels of food webs
We found a significant difference in patterns of calcium accrual between treatments, with an increase in the controls compared with the electrified treatments (Fig 2 and Table 1)
Our findings suggest that excluding macroconsumers did not directly affect the abundance of benthic invertebrates, chlorophyll-a concentration or dry mass, and ash-free dry mass (AFDM)

Summary

Introduction

Human activities can disproportionally affect macroconsumers in the upper trophic levels of food webs (i.e., top predators). Loss of macroconsumers can result in rapid changes in community structure and ecosystem function [1,2,3]. Macroconsumers (such as many species of fish and decapod crustaceans) can directly influence the accumulation, and transport of organic and inorganic sediments by disturbing substrates (bioturbation) and feeding at multiple spatiotemporal scales [4,5,6,7,8,9,10]. The presence of macroconsumers can reduce the rate of sediment accumulation on bottom substrates and can simultaneously limit the abundance and diversity of benthic algae and/or invertebrates that depend on specific substrates [5,11,12,13].

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Conclusion