OXYGEN ISOTOPE DYNAMICS OF LAKE WATER AND DISSOLVED PHOSPHATE IN SALINE LAKES OF THE CARIBOO PLATEAU OF BRITISH COLUMBIA, CANADA

Alkaline and saline lakes can contain uniquely elevated concentrations of phosphorus relative to other natural waters. As such, they have been proposed as a solution to the “phosphate problem” in origins of life studies. Yet, phosphorus sourcing and subsequent biological and abiotic processing are poorly understood in these lakes. Here, we use stable oxygen isotope analyses (δ¹⁸O) of dissolved phosphate and corresponding lake waters to evaluate these processes. We specifically study the alkaline Last Chance and Goodenough lakes and the magnesium sulfate-bearing Basque lakes of the Cariboo Plateau of British Columbia. Over a two-year period, these lakes were sampled during peak fullness (early summer) and during peak evaporation (late autumn), with the objective of collecting a comprehensive temporal and spatial dataset. We modified an established phosphate purification process to isolate the dissolved phosphate from the lake waters, and then measured both phosphate and lake water oxygen isotope ratios via continuous-flow isotope-ratio mass spectrometry. Our results show that oxygen isotopes can effectively trace the movement of phosphorus through the unique biological and geological pathways of these systems. In turn, our results provide valuable insight into the cycling of phosphorus within alkaline lakes and their potential applicability to origins of life scenarios on both Earth and Mars.