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What supports the deep chlorophyll maximum in acidic lakes? The role of the bacterial CO 2 production in the hypolimnion
Author(s) -
SoriaPíriz Sara,
Lara Miguel,
JiménezArias Juan Luis,
Papaspyrou Sokratis,
Úbeda Bárbara,
GarcíaRobledo Emilio,
Bohórquez Julio,
Gálvez José Ángel,
Revsbech Niels Peter,
Corzo Alfonso
Publication year - 2020
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11391
Subject(s) - hypolimnion , water column , phytoplankton , dissolved organic carbon , chlorophyll a , heterotroph , environmental chemistry , photosynthesis , chlorophyll , irradiance , plankton , environmental science , thermocline , organic matter , deep chlorophyll maximum , bacterioplankton , primary production , stratification (seeds) , nutrient , chemistry , botany , photic zone , eutrophication , ecology , biology , bacteria , ecosystem , seed dormancy , genetics , physics , germination , quantum mechanics , dormancy
The interactions between phytoplankton, bacteria and resources, irradiance, and nutrients, leading to the formation of deep chlorophyll maxima (DCMs), are little understood in acid lakes. In “El Sancho” reservoir (Iberian Pyritic belt, Huelva, Spain), an acid mine drainage impacted waterbody (pH 3.5–4.0), a strong DCM forms in the metalimnion during the stratification period. The DCM was located always below the 1% irradiance level, where the decreasing irradiance profile overlapped with a dissolved inorganic carbon concentration (CO 2 ) gradient decreasing upward from the hypolimnion. The DCM was dominated by the chlorophyte Carteria sp. and showed the highest volumetric photosynthetic and dark respiration rates. The DCM, however, only contributed around 20% of water column integrated gross primary production, while it accounted for 54–66% of water column chlorophyll. The total bacterial abundance correlated significantly with the CO 2 concentration ( r = 0.74). To test the hypothesis of a possible dependence of the formation of the DCM in acid lakes on the production of CO 2 by heterotrophic bacteria, a one‐dimensional reactive transport model (DCM‐CO 2 ) was developed and tested. The DCM‐CO 2 model simulated the vertical distribution of chlorophyll ( R 2 > 0.63) and the vertical profile of CO 2 rather accurately ( R 2 > 0.79), the position of DCM depending on both light penetration and an upward flux of CO 2 produced by hypolimnetic heterotrophic bacteria. Overall, the results support the hypothesis of microbial degradation of organic matter being a source of CO 2 for acid lake primary producers at the DCM.