| Autor: |
Müller, Beat, Steinsberger, Thomas, Stöckli, Arno, Wüest, Alfred |
| Zdroj: |
Environmental Science & Technology; 20210101, Issue: Preprints |
| Abstrakt: |
Decline in total phosphorus (TP) during lake reoligotrophication does not apparently immediately influence carbon assimilation or deep-water oxygen levels. Traditional monitoring and interpretation do not typically consider the amount of organic carbon exported from the productive zone into the hypolimnion as a measure of net ecosystem production. This research investigated the carbon-to-phosphorus ratios of suspended particles in the epilimnion, (C:P)epi, as indicators of changing productivity. We report sestonic C:P ratios, phytoplankton biomass, and hypolimnetic oxygen depletion rates in Lake Hallwil, a lake whose recovery from eutrophic conditions has been documented in 35 years of historic water-monitoring data. This study also interpreted long-term (C:P)epiratios from reoligotrophication occurring in four other lakes. Lake Hallwil exhibited three distinct phases. (i) The (C:P)epiratio remained low when TP concentrations did not limit production. (ii) (C:P)epiincreased steadily when phytoplankton began optimizing the declining P and biomass remained stable. (iii) Below a critical TP threshold of ∼15 to ∼20 mg P m–3, (C:P)epiremained high and the biomass eventually declined. This analysis showed that the (C:P)epiratio indicates the reduction of productivity prior to classic indicators such as deep-water oxygen depletion. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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