DOI: 10.5061/dryad.f4211
title: Data from: Pulsing hydrology determines top-down control of basal resources in a tropical river-floodplain ecosystem

description: Variable hydrology of rivers strongly affects biophysical factors that
 influence primary production and population densities, thereby affecting
 the relative influence of bottom-up and top-down processes in trophic
 networks. Many tropical floodplain rivers have sustained seasonal flood
 pulses driven by precipitation patterns of the Intertropical Convergence
 Zone. These changes in flow alter concentrations of dissolved nutrients,
 aquatic primary productivity, and per-unit-area densities of aquatic
 organisms. Therefore, one would predict that the strength of top-down
 effects of animals on basal resources should shift as the annual flood
 pulse progresses. We conducted a series of field experiments in a
 Neotropical lowland river to test for effects of hydrologic phase, habitat
 (in-channel vs. floodplain aquatic habitat), and benthic feeding fish and
 meiofauna on particulate organic matter, chlorophyll, and benthic
 microalgae. Net ecosystem productivity of this oligotrophic river is
 higher during the low phase of the annual flood cycle, which is also when
 resident fishes are at highest densities and there is a seasonal influx of
 migratory benthic feeding fish. We therefore hypothesized that top-down
 effects of benthic-feeding fish would fluctuate temporally, with strongest
 effects during low water levels. We found that fish controlled the
 abundance of particulate organic matter and algae on solid substrates, but
 not on sand, during falling- and low-water phases within both channel and
 floodplain habitats. Except for diatom assemblages, which responded to
 fish exclusion, the taxonomic structure of algal and meiofauna assemblages
 was not significantly influenced by fish exclusion treatments, but varied
 in relation to habitat type and hydrologic phase. Meiofauna densities were
 highest during the low-water period; experimental exclusion of meiofauna
 during this period had a significant effect on accumulation of particulate
 organic matter in sand. By controlling abundance of important basal
 resources, fishes and meiofauna have large potential to influence other
 components of this tropical ecosystem. Our findings emphasize the
 predictable, gradual, changes in consumer-resource interactions associated
 with the seasonal flood pulse in tropical river systems.
description: 1-Cinaruco AFDM Tiles
 Expsamples and calculations
 for particulate organic matter accumulations on tiles during fish
 exclosure/enclosure experiments2-Cinaruco CHLA Tiles
 Expsamples and calculations
 for chlorophyll a accumulations on tiles during fish exclosure/enclosure
 experiments3-Cinaruco AFDM Sand
 Expsamples and calculations
 for particulate organic matter accumulations in sand during fish
 exclosure/enclosure experiments4-Cinaruco CHLA Sand
 Expsamples and calculations
 for chlorophyll a accumulations in sand during fish exclosure/enclosure
 experiments5-Cinaruco Algal
 Biovolume Tiles Expsamples and calculations
 for alga taxa and their biovolumes accumulations on tiles during fish
 exclosure/enclosure experiments6-Cinaruco Meiofauna
 Density Sand Expsamples and calculations
 for meiofauna taxa and their densities in sand during fish
 exclosure/enclosure experiments