Increasing Carbon-to-Phosphorus Ratio (C:P) from Seston as a Prime Indicator for the Initiation of Lake Reoligotrophication

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 hypo...

Full description

Saved in:
Bibliographic Details
Published in:Environmental science & technology 2021-05, Vol.55 (9), p.6459-6466
Main Authors: Müller, Beat, Steinsberger, Thomas, Stöckli, Arno, Wüest, Alfred
Format: Article
Language:English
Subjects:
Biogeochemical Cycling
Biomass
Carbon
China
Deep water
Depletion
Depth indicators
Ecosystem
Environmental changes
Environmental Monitoring
Epilimnion
Eutrophic environments
Eutrophication
Hypolimnion
Indicators
Lakes
Monitoring
Nitrogen - analysis
Organic carbon
Oxygen
Oxygen depletion
Phosphorus
Phosphorus - analysis
Phytoplankton
Plankton
Ratios
Seston
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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)epi ratios from reoligotrophication occurring in four other lakes. Lake Hallwil exhibited three distinct phases. (i) The (C:P)epi ratio remained low when TP concentrations did not limit production. (ii) (C:P)epi increased 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)epi remained high and the biomass eventually declined. This analysis showed that the (C:P)epi ratio indicates the reduction of productivity prior to classic indicators such as deep-water oxygen depletion.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.0c08526