Spatial distribution of aestivating aquatic invertebrates in dry playa lakes

Background/Question/Methods

Aquatic invertebrates that inhabit temporary aquatic habitats (e.g., playa lakes, intermittent streams) need to survive periodic drying events.  These invertebrates usually survive terrestrial phases by incorporating different life history strategies.  Highly mobile invertebrates (e.g., insects) can typically colonize temporary habitats from other sources of water.  However, less mobile organisms (e.g., gastropods and crustaceans) typically persist during the terrestrial phase through an aestivation stage.  We examined the spatial distribution of aestivating stages of aquatic invertebrates in dry playa lakes in western Oklahoma.  We collected soil at three different locations, near the center, near the playa edge, and in the surrounding upland, of four dry playa lakes during the summer of 2010.  We inundated the soil in plastic containers in a greenhouse.  After two weeks, the containers were destructively sampled by pouring the water through a 250 µm sieve and preserving the invertebrates.  Invertebrate abundance, richness, and overall community assemblage structure were compared among soil locations.  

Results/Conclusions

The soil taken near the center of the dry playa had greater taxonomic richness and abundance of invertebrates than the upland soil.  An intermediate number of taxa and abundance emerged from the soil taken from near the playa lake edge.  Furthermore, a different invertebrate assemblage emerged from the upland soil than from the center of the dry playa lake.  The overall invertebrate assemblage of the playa edge was intermediate between the upland and center soils.  Indicator species analysis of the aquatic invertebrate taxa identified that ostracods emerged predominantly from soil taken near the center of the playa.  Indicator species analysis of all taxa (aquatic and terrestrial) showed that cladocerans, nematodes, ostracods, clam shrimps, tadpole shrimps, gastropods and calanoid copepods were more likely to emerge from soil from the center while psychodids and gall midges emerged in greater frequencies from the upland soil.