Ephemerally inundated salt lakes in arid regions support unique aquatic macroinvertebrate communities that typically persist through prolonged dry periods as resistant resting-stages (e.g. spores, eggs). Salt lakes represent a large proportion of inland lentic habitats on the Australian continent, many occurring in remote arid areas where filling events are infrequent and unpredictable. Currently, biodiversity surveys of dry salt lakes rely on artificial rehydration of sediments to stimulate emergence of resident taxa. However, egg banks contain cryptic assemblages with poorly understood hatching requirements that may fail to emerge under artificial conditions, underestimating biodiversity. Here, we evaluate bulk DNA metabarcoding of resting-stage egg banks to survey aquatic invertebrates within an ephemeral salt lake, investigating whether DNA metabarcoding could offer a complementary approach to assess biodiversity, independent of emergence.
Sediments were collected from six sites at Lake Way, in the Murchison region of Western Australia. For each site, two different DNA extraction protocols were used; directly extracting DNA from sediments, and using the Onbé-Marcus method (sugar flotation) to concentrate eggs onto a paper filter for extraction. Metabarcoding results were compared with taxa recovered from a contemporaneous rehydration trial. DNA metabarcoding detected more taxa, including seven unique taxa, whereas only one taxon was exclusive to rehydration trials. The sugar-flotation method vastly outperformed standard extraction, with target taxa almost exclusively recovered via sugar-flotation. Our findings indicate that bulk metabarcoding egg banks isolated by sugar-flotation is an effective method for documenting aquatic invertebrates in dry salt lakes and represents a valuable addition to the monitoring toolbox for management and conservation of these systems.