Abstract

BackgroundFairy shrimps (Anostraca), tadpole shrimps (Notostraca), clam shrimps (Spinicaudata), algae (primarily filamentous blue-green algae [cyanobacteria]), and suspended organic particulates are dominant food web components of the seasonally inundated pans and playas of the western Mojave Desert in California. We examined the extent to which these branchiopods controlled algal abundance and species composition in clay pans between Rosamond and Rogers Dry Lakes. We surveyed branchiopods during the wet season to estimate abundances and then conducted a laboratory microcosm experiment, in which dried sediment containing cysts and the overlying algal crust were inundated and cultured. Microcosm trials were run with and without shrimps; each type of trial was run for two lengths of time: 30 and 60 days. We estimated the effect of shrimps on algae by measuring chlorophyll content and the relative abundance of algal species.ResultsWe found two species of fairy shrimps (Branchinecta mackini and B. gigas), one tadpole shrimp (Lepidurus lemmoni), and a clam shrimp (Cyzicus setosa) in our wet-season field survey. We collected Branchinecta lindahli in a pilot study, but not subsequently. The dominant taxa were C. setosa and B. mackini, but abundances and species composition varied greatly among playas. The same species found in field surveys also occurred in the microcosm experiment. There were no significant differences as a function of experimental treatments for either chlorophyll content or algal species composition (Microcoleus vaginatus dominated all treatments).ConclusionsThe results suggest that there was no direct effect of shrimps on algae. Although the pans harbored an apparently high abundance of branchiopods, these animals had little role in regulating primary producers in this environment.

Highlights

  • IntroductionFairy shrimps (Anostraca), tadpole shrimps (Notostraca), clam shrimps (Spinicaudata), algae (primarily filamentous blue-green algae [cyanobacteria]), and suspended organic particulates are dominant food web components of the seasonally inundated pans and playas of the western Mojave Desert in California

  • Fairy shrimps (Anostraca), tadpole shrimps (Notostraca), clam shrimps (Spinicaudata), algae, and suspended organic particulates are dominant food web components of the seasonally inundated pans and playas of the western Mojave Desert in California

  • Brostoff et al [3] estimated the photosynthesis of the constituent algae in biotic crusts on moist surfaces of the pans at 4 μmol C/m2/sec, a rate that is the same order of magnitude as nearby upland vegetation

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Summary

Introduction

Fairy shrimps (Anostraca), tadpole shrimps (Notostraca), clam shrimps (Spinicaudata), algae (primarily filamentous blue-green algae [cyanobacteria]), and suspended organic particulates are dominant food web components of the seasonally inundated pans and playas of the western Mojave Desert in California. Brostoff et al [3] estimated the photosynthesis of the constituent algae in biotic crusts on moist surfaces of the pans at 4 μmol C/m2/sec, a rate that is the same order of magnitude as nearby upland vegetation (no such data are available for algae during the inundated phase) The fate of such productivity is unclear, fairy and clam shrimps ingest and digest planktonic and benthic algae, along with detritus and suspended organics, via non-selective filter feeding or scraping [8,9,10,11,12,13], and algal material can be the primary food resource of these shrimps [13,14,15,16]. These ephemeral desert waters support insect (Hemiptera: Notonectidae; pers. obs.) and avian predators [17]

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