Researchers report earlier shrimp hatches, complex brine‑fly presence and model divergence in 2024

Connor Simon, a biologist with the Great Salt Lake program, summarized shrimp and brine‑fly monitoring for 2024, describing seasonal shifts in hatching timing, life‑stage amplitudes and new efforts to quantify brine‑fly larvae in the water column.

Simon said surface salinity during 2024 was “much fresher” than recent long‑term averages and that spring temperatures were higher than average, which “meant hatching could occur earlier.” He reported earlier-than‑usual nauplius (hatchling) peaks and larger amplitude peaks for adults and juveniles compared with many prior years. Connor summarized that cyst density rose above the 5‑year average into the fall, then dropped as temperatures fell.

The group discussed a model that predicts fall cyst density from spring counts. Simon explained the model produced a broad prediction range in 2024 because only a single spring month of data was available; with outliers removed the model predicted a much higher fall cyst density than was observed. “With more data, it obviously would have been a little bit better,” Simon said, noting logistical constraints (weather, sampling frequency and wind) may cause underestimation of cysts in some samples.

Simon also showed new, preliminary water‑column counts of brine‑fly (Ephydra) larvae. He cautioned the data are early and variable but said water‑column larvae were detectable across seasons and occasionally reached hundreds per liter in extreme samples. A question from other researchers focused on instar (larval stage) composition; Simon noted measuring instars adds substantial counting time but agreed stage data would help interpret whether larvae in the water column reflect recent hatching, drift from benthos, or buoyancy issues at high salinity.

Gary Belovsky (University of Notre Dame) reviewed published shrimp analyses and a set of new decomposition experiments designed to link pelagic and benthic nutrient cycling. He said the shrimp data paper was published online the prior Monday and that experimental work has quantified decomposition rates (and nitrogen release) for phytoplankton, shrimp bodies, shrimp feces and feathers across temperature and salinity treatments. He reported similar experiments for brine‑fly larval, pupal and adult bodies and is finishing larval frass decomposition results.

Belovsky described the model output linking pelagic and benthic (microbialite) nitrogen cycling. He and collaborators measured how quickly biological materials sink and decompose, and used those rates to estimate nitrogen fluxes between the water column and microbialites. In some model runs the microbialite/benthic compartment amplified nitrogen available to pelagic primary producers by roughly 23% to 39%, depending on assumptions and material flows; Belovsky cautioned these are preliminary “ballpark” figures and that microbial-community composition and sediment compartments may change rates over time.

Discussion participants raised three recurrent concerns: (1) whether water‑column brine‑fly larvae represent early instars or later instars displaced from benthos; (2) the influence of salinity and buoyancy on larvae distribution; and (3) possible missing nitrogen cycling compartments in sediments below microbialites. Participants suggested coordinated lab work to quantify instars, to run controlled salinity/ buoyancy tests and to add targeted sediment sampling and metagenomic surveys to resolve microbial nitrogen‑cycling pathways.

Why it matters: Artemia (brine shrimp) and ephydrid flies form the primary food base for many shorebirds and waterbirds at Great Salt Lake; shifts in timing, abundance or life‑stage composition can change food availability for migrating and staging birds and affect model predictions used by managers.

Sources and attributions: Direct quotes and data points in this article are attributed to Connor Simon (biologist, Great Salt Lake program) and Gary Belovsky (University of Notre Dame), taken from the meeting transcript.