Dissolved silica dynamics, transfer and retention in a temperate groundwater flow‑through shallow lake of the Pampean Plain, Argentina

BORRELLI, NATALIA L.; ROMANELLI, A; FERNÁNDEZ HONAINE, MARIANA; FARENGA, MARCELO; FABIANI, ANA; ESQUIUS, SOLEDAD; OSTERRIETH, MARGARITA

AQUATIC SCIENCES

BIRKHAUSER VERLAG AG

Lugar: BASEL; Año: 2023 vol. 85

1015-1621

Mainly through BSi processing, shallow lakes regulate DSi retention, transport, and delivery to the ocean. However, theseDSi fluxes in southern lakes are little known. This work evaluated the spatio-temporal variation and the main factors thataffect DSi dynamics and retention in a temperate groundwater flow-through shallow lake in Argentina. Water samples fromstreams, the lake, and groundwater were collected from Los Padres Lake Watershed for DSi determination. DSi retention wascalculated through a mass balance approach. The BSi pool from macrophytes was quantified using biomass, BSi production,and satellite images. The phytoplankton community was described by chlorophyll content, species quantification, and alphadiversity metrics. The contribution of Si-enriched water from groundwater (≈ 50 mg L−1) mainly controlled DSi concentrationsin the inflow stream (≈ 54 mg L−1). Lake DSi concentration was lower than streams and groundwater, and increasedover time (14–34 mg L−1). BSi contribution by macrophytes (≈1.4 Mg Si year−1) has little variation, therefore, the reductionof diatoms due to cyanobacteria increase is the most likely factor controlling DSi dynamics, influencing the role of the lakeas a DSi sink/source. These biogeochemical processes regulated the DSi transfer from the lake to the outflow stream, andthe delivery to the ocean (≈ 630 Mg Si year−1). Given the importance of small lakes in nutrient cycling and retention alongflow paths within a watershed, in-lake Si processes and Si sources to these water bodies are critical to quantifying limneticcontributions to the global Si cycle.