Nutrient metabolism (C, N, P, and Si) in the trophogenic zone of a meromictic lake

Abstract

The dynamics of seston and dissolved elements in a meromictic lake with high concentrations of manganese and iron in the monimolimnion were studied through an annual cycle. This publication presents results for assimilation, sedimentation and recovery of nutrients (C, N, P, and Si) in the trophogenic zone. Phosphorus deficiency kept the productivity of the diatom dominated phytoplankton at an oligotrophic level. High concentrations of iron in influent streams and redistribution followed by precipitation of iron during periods of partial turnover removed phosphorus from the water. High concentrations of manganese and sulfate did not have the anticipated fertilizing effect, and recovery of nutrients from the depth of the lake was negligible. Mass balance calculations indicate that liberation of phosphorus from the sediments in the trophogenic zone was most important for the maintenance of primary production. 75 % of carbon, 80 % of nitrogen and 25 % of phosphorus assimilated by the phytoplankton was mineralized in the trophogenic zone. Silica was effectively regenerated from the littoral zone during the decline of diatom blooms. Nitrogen and silica retention was 45% of the external load compared to 66% for phosphorus.

In search of the RNA world on Mars

“…Low pH values on Mars would have most likely been prevalent by the late Noachian (Figure 2) or perhaps locally at natural acid springs (e.g., Varekamp et al, 2009). Results from our experiments at pH 6.7 therefore represent the most accurate interpretation of potentially global conditions on Mars since the pre-Noachian (Bibring et al, 2006 Busigny et al, 2014;Hongve, 1994;Kling et al, 1989…”

“…While concentrations up to 50 mM were tested here, lower metal concentrations ~ 1 mM are more geochemically plausible on Earth though estimates on Mars are not well constrained. Observations from anoxic crater lakes and perennially stratified ferruginous lakes on Earth show that ranges between 0 and 1.5 mM of dissolved Fe 2+ , Mn 2+ , or Mg 2+ are reasonable for a basalt hosted basin (e.g., Bura‐Nakić et al., 2009; Busigny et al., 2014; Hongve, 1994; Kling et al., 1989). However, such low values are often at odds with proposed prebiotic chemistries which require 50 – 250 mM of metals for in situ RNA synthesis (e.g., 250 mM Fe 2+ ‐ Patel et al., 2015) or replication (e.g., 50 – 200 mM Mg 2+ ‐ Szostak, 2012).…”

Nutrient Budgets, Dynamics and Storm Effects in a Eutrophic, Stratified Baltic Lake

“…Knuuttila et al [18] found values between 19 % and 50 % in two shallow eutrophic Finnish lakes with water residence times between 67 and 160 days. Galicka [19] calculated for Sulejow Reservoir (water residence times between 28 and 35 days) values between 24 % and 53 % and Hongve [20] found a P-retention of 66 % in the less polluted meromictic Norwegian lake Nordbytjernet. Lake Belau has a water residence time of more than 270 days and in this context the phosphorus retention of less than 10 % is an unusual small value.…”