Arthropods, bryophytes being developed as condition bioindicators for intermittent streams

SCCWRP and California State University, Monterey Bay, in June launched a study to investigate the feasibility of using terrestrial arthropods and bryophytes (e.g., mosses) to assess the biological condition of intermittent streams that run dry for much of the year.

These two biological indicators will be the first to be developed specifically for intermittent and ephemeral streams at the drier end of the hydrologic spectrum. Although intermittent streams make up about 60% of all streams in Southern California, existing bioindicators for perennial streams are not calibrated to generate accurate condition assessments for the driest of these streams.

Assessment tools for intermittent streams are expected to become increasingly valuable as more of Southern California’s streams run dry in response to climate change, drought, and increased water conservation and reuse.

Researchers hypothesize that terrestrial arthropods – including insects, arachnids, myriapods and crustaceans – will serve as sentinel indicators of how intermittent streams are impacted by agricultural and urban runoff. Bryophytes like mosses and liverworts, meanwhile, have been shown to be highly sensitive to water quality and siltation, in much the same way that organisms like algae are in perennial streams.

SCCWRP and its partners have developed a set of sampling protocols that they’re using this summer to collect and analyze arthropods and bryophytes from across about 30 sites in the San Diego area. The sites represent a range of natural gradients and stress levels.

Researchers anticipate sharing initial data and analyses in spring 2017, which will help guide a multi-year effort to adapt these organisms as bioindicators of stream condition.