Lake Piburg: 50 Years of Biogeochemical Monitoring

Dataset associated with the publication Fifty-Year Trends Reveal Reversal from Recovery to Re-eutrophication and Reinforced Anoxia in a Managed Mountain Lake (Weniger & Sommaruga, 2025, Ecosystems; DOI: 10.1007/s10021-025-01003-5).

Data Description:

Samples were collected from the Long-Term Socio-Ecological Research (LTSER) site, Lake Piburg, Austria (47° 11′ 42″ N, 10° 53′ 20″ E). This subalpine lake is surrounded by a forest, has an area of 13.4 ha, a maximum depth of 24.6 m, and is situated at 913 m above sea level. In 1970, an ‘Olszewski pipe’ for selective hypolimnetic withdrawal was installed at the lake’s deepest area, as part of restoration efforts. The 8.9 cm diameter pipe passively siphons nutrient-rich, oxygen-depleted water from a depth of approximately 23-24 m, discharging it outside the lake’s catchment. The lake’s mountainous location provided an elevational difference of 11 m between the pipe’s inlet and outlet (total length: 639 m), enabling gravity-driven flow without the need for external energy.

Since 1972, monthly measurements of key limnological parameters have been recorded at eight depths (0 m, 3 m, 6 m, 9 m, 12 m, 15 m, 18 m, 21 m, and 24 m), with only a few inconsistencies in sampling, primarily due to inaccessibility caused by a thin ice cover. Water temperature has always been measured using a calibrated thermometer (0.1 °C resolution) placed inside a 5-L vertical water sampler. Oxygen concentrations were measured by the Winkler titration method. Chlorophyll-a, used as a proxy for algal biomass, was quantified via spectrophotometry following alkaline acetone extraction. Total phosphorus was determined by spectrophotometry after acid digestion, using the molybdenum blue reaction. Sulfate and nitrate were analyzed by spectrophotometry and later, by ion chromatography, while ammonium concentrations were measured using spectrophotometry. If an instrument or method changed during the study period, internal laboratory comparisons were statistically evaluated and since the 1980s, quality control measures have included regular participation in ring tests (CNR-IRSA Institute, Italy; and NIVA, Norway) and verification of ion sum balances.

Column Description:

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PIB - Bathymetry.xlsx
Depth = depth in m (numeric)
Area = area of layer in m^2 (numeric)
Layer = Information about depth interval thickness in m
Volume = Volume at each depth in m^3 (numeric)

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PIB - Olszeswki Tube - Volume Output.xlsx
year - year (character)
month - month (character)
output_l/s - water discharge by the tube in l/s (numeric)
temp_c - temperature of the water output by the tube in degrees celsius (numeric)

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PIB - Olszeswki Tube - Physico-Chemical Data.xlsx
date - date (character)
year - year (character)
month -  (numeric)
day - (numeric)
temp - temperature in degrees Celsius (numeric)
conductivity - Conductivity measured in situ in µS/cm (numeric)
conductivity_lab - Conductivity measured in water samples taken to the laboratory in µS/cm (numeric)
pH - pH measurement 
alk - alkalinity in µeq/l (numeric)
Cl - Chloride concentration in mg/L
no3 - nitrate concentration in mg/L
so4 - sulphate concentration in mg/L
NA - Sodium concentration in mg/L
K - Potassium concentration in mg/L
Mg - Magnesium concentration in mg/L
Ca - Calcium concentration in mg/L
nh4_n_phot - ammonium concentration in µg/l
TP - total phosphorus concentration in µg/l
DP - dissolved phosphorus concentration in µg/l
DOC - dissolved organic carbon concentration in µg/L
DN - dissolved phosphorus concentration in µg/l

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PIB - Lake Data.xlsx
date - posixt object (UTC)
year - year (character)
month -  (numeric)
day - (numeric)
depth - depth in m (numeric)
temp - temperature in degrees Celsius (numeric)
secchi_depth - Secchi Depth in m (numeric)
pH - (numeric)
alk - alkalinity in µeq/l (numeric)
TP - total phosphorus concentration in µg/l
DP - dissolved phosphorus concentration in µg/l
DOC - dissolved organic carbon concentration in µg/L
DN - dissolved phosphorus concentration in µg/l
chla - chlorophyll-a concentration in µg/l
oxygen - oxygen concentrations in mg/L
Cl - Chloride concentration in mg/L
N_NO3 - nitrate concentration in mg/L
SO4 - sulphate concentration in mg/L
NA - Sodium concentration in mg/L
K - Potassium concentration in mg/L
Mg - Magnesium concentration in mg/L
Ca -Calcium concentration in mg/L
nh4_n_phot - ammonium concentration in µg/l
cond_lab - Conductivity measured in water samples taken to the laboratory in µS/cm (numeric)

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PIB - Stratification Duration
year - year (character)
n_days - duration of summer stratification in days (numeric)

Methods of calculation described in the paper.

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PIB - TP in Lake Inflow.xlsx
date - posixt object (UTC)
year - year (character)
month -  (numeric)
day - (numeric)
tp_µg/L - total phosphorus concentration in µg/l