Water quality of Lake Sanabria according to phytoplankton. A comparison with historical data

Abstract

Water quality of Lake Sanabria according to phytoplankton. A comparison with historical dataLake Sanabria is a Spanish lake that holds the largest volume of water in the country. It is a terminal moraine, monomictic, acidic lake that is typically oligotrophic to oligo-mesotrophic. The current situation of the lake was assessed using phytoplankton data from the growing seasons of 2013. In addition, data from the 1980s were used to evaluate any variation from former conditions. The planktonic communities were analyzed using biomass measurements (Chlorophyll-a and biovolume) and several composition metrics (IGA, PTSI, PTI and IGA2). Considering the applicable Spanish legislation for ecological quality assessment, the ecological status in 2013 was High. According to both the biomass and composition metrics, no change in the trophic status was apparent, although there was some evidence of a shift in species contribution to biomass from the 1980s samples to the current ones. The shift from cyanobacterial taxa to diatoms was one of the changes observed, but this does not necessarily imply a change in the trophic status.

Taxonomic composition, community structure and molecular novelty of microeukaryotes in a temperate oligomesotrophic lake as revealed by metabarcoding

“…Since 2012, the Duero International Biological station has raised concerns that Sanabria Lake is undergoing a eutrophication process due to contamination from a deficient sewage depuration system (Guillen, 2015). However, studies based on pigment measurements and microscopy observation of the phytoplankton community do not support the eutrophication scenario and confirm the current oligotrophic state of the lake (Pahissa, Fernández-Enríquez, and De Hoyos 2015;Llorente and Seoane 2020).…”

“…The mixing period extends from late November to early March, when a thermocline normally appears (Vega et al 1992). No anoxic conditions have been observed in any layer of the water column during the thermal stratification (Vega et al 1992;de Hoyos 1996;Pahissa, Fernández-Enríquez, and De Hoyos 2015). Sanabria Lake is considered as oligotrophic to oligomesotrophic in view of its low levels of chlorophyll a, nutrient concentration, phytoplanktonic biovolume values and production rates (Planas 1991;Vega et al 1992;de Hoyos 1996;Pahissa, Fernández-Enríquez, and De Hoyos 2015;Llorente and Seoane 2020;De Hoyos and Comín 1999).…”

“…In comparison to lakes of other trophic states, oligomesotrophic lakes harbour the richest and most diverse lentic organismal communities (Lefranc et al 2005). Sanabria Lake is the biggest natural glacial lake in the Iberian Peninsula (Vega et al 2005) and has already been the subject of many traditional limnological studies (Taboada 1913;Margalef 1955;Aldasoro et al, 1992;Vega et al, 1992;De Hoyos, 1996;De Hoyos et al, 1998;De Hoyos and Comín, 1999;Negro, De Hoyos, and Aldasoro 2003;Luque 2002;Jambrina-Enríquez et al 2014;Pahissa, Fernández-Enríquez, and De Hoyos 2015; Llorente and Seoane 2020) Negro et al, 2000;Luque & Julià, 2002;Rico et al, 2007;Jambrina-Enríquez et al, 2014;Pahissa et al, 2015;Llorente and Seoane 2020). However, no molecular data are currently available for this freshwater system.…”

“…De Hoyos 2015; Llorente and Seoane . CC-BY-NC-ND 4.0 International license made available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.…”

Taxonomic composition, community structure and molecular novelty of microeukaryotes in a temperate oligomesotrophic lake as revealed by metabarcoding

“…The mixing period extends from late November to early March, when a thermocline normally appears 56 . No anoxic conditions have been observed in any layer of the water column during the thermal stratification 54 , 56 , 58 . Sanabria Lake is considered as oligotrophic to oligomesotrophic in view of its low levels of chlorophyll a , nutrient concentration, phytoplanktonic biovolume values and production rates 50 , 54 – 56 , 58 .…”