Brine shrimp grazing and fecal production increase sedimentation to the deep brine layer (monimolimnion) of Great Salt Lake, Utah

Abstract

Great Salt Lake (Utah) has a monimolimnion with high concentrations of salts, particulate matter, nutrients, and mercury. To test the importance of brine shrimp (Artemia franciscana) grazing on particulate matter flux, we created salinity gradients in 160-cm high columns, reflecting the lake's gradient. Two experiments were performed in replicated columns with or without Artemia. Sediment traps were positioned at the bottoms of the mixolimnion (95 cm), chemolimnion (105 cm), or monimolimnion (140 cm). We hypothesized that because of the high salt densities of the monimolimnia, greater accumulation of sediments would be in the lower chemocline, than in the monimolimnia. The presence of Artemia significantly decreased chlorophyll, total nitrogen, and total phosphorus in the mixolimnion and increased particulate matter collected in sediment traps by 28-90%. As hypothesized, the largest increase of sedimenting material was at the top of chemocline, but only in the absence of Artemia. When present, the largest increase of collected matter was in the bottom traps. Artemia significantly decreased the molar TN:TP ratio of collected material, suggesting nitrogen-deficient fecal material. The experiments demonstrated the importance of Artemia grazing for increasing material flux from the mixolimnion to the bottom, and determining the stoichiometry of accumulated material.

Alleviation of hypoxia by biologically generated mixing in a stratified water column

“…Swimming behavior also appeared unaffected by the variable oxygen concentration. The impervious nature of the brine shrimp to variable oxygen levels has been similarly observed in situ for brine shrimp inhabiting anoxic waters (Maszczyk and Wurtsbaugh 2017).…”

In Memoriam Maria Rosa Miracle. Limnologist

“…Only 8 % of the recovered tracer had fallen into the sediment traps. This low amount was not surprising given that: (1) much of the tracer was likely incorporated into Synechococcus, with very low sedimentation rates (Camacho et al, 2003b;Camacho, 2006) and; (2) macrozooplankton grazing in the DCL was likely very low, with consequent low export of fecal material that can account for significant losses of particulate matter from the water column of lakes and oceans (Pilati & Wurtsbaugh, 2003;Turner, 2015;Maszczyk & Wurtsbaugh, 2017). Additionally, grazing on the abundant Synechococcus was likely done by the abundant rotifer, Anuraeopsis fissa, that graze bacteria and picoplankton efficiently (Ooms-Wilms, 1997;Twiss et al, 2012).…”

Historic low stand of Great Salt Lake, Utah: I

“…1,12). A distinct DBL had disappeared by early to mid-2014 through most of the south arm although it persisted close to the causeway at least until May, 2015 [25].…”