Who supports the deep chlorophyll maximum in acidic lakes? The role of the bacterial community

  1. Soria Píriz, Sara 1
  2. Lara, Miguel 1
  3. Jiménez-Arias, Juan Luis 1
  4. Papaspyrou, Sokratis 1
  5. Úbeda, Bárbara 1
  6. García-Robledo, Emilio 1
  7. Bohórquez, Julio 1
  8. Gálvez, José Ángel 1
  9. Corzo, Alfonso 1
  1. 1 Universidad de Cádiz

    Universidad de Cádiz

    Cádiz, España

    ROR https://ror.org/04mxxkb11

1st Meeting of the Iberian Ecological Society (SIBECOL)

Publisher: Asociación Española de Ecología Terrestre (AEET)

Year of publication: 2019

Pages: 102-102

Type: Conference paper


The interactions between phytoplankton, bacteria and nutrients leading to the formation of deep chlorophyll maximum (DCM) in acid lakes are little understood. Here, we studied the Sancho reservoir (Iberian Pyritic belt, Huelva, Spain), an acid mine drainage impacted water body (pH 3.5 - 4.0), where a strong DCM forms during the stratification period. The observed DCM (always below the 1% irradiance level) showed the maxima photosynthetic capacity and dark respiration rates of the entire column. Total bacterialabundance highly correlated with dissolved inorganic carbon concentration (DIC, r = 0.74). Given that DIC concentrations in acid lakes are low, DCM development and position might depend on the close coupling between DIC regeneration by bacteria degradation in the hypolimnion (71.43 ± 21.83 mmol C m-2 d-1) and photosynthetic production consuming DIC at this depth (1.25 ± 0.7 mmol C m-2 d-1). This hypothesis was successfully tested by means of a 1D reactive transport model which predicted the phototrophic biomass spatial distribution as a function of irradiance and DIC. Model outcomes suggest that the vertical position of DCM depends on both light penetration (R2 > 0.72) and diffusive flux of DIC produced by hypolimnetic heterotrophic bacteria (R2 > 0.95). Rates of DIC regeneration were better explained by including a term of anaerobic respiration accounting for the hypoxia conditions at depth, since oxygen dark respiration was very low. Overall, results support the role of DIC as a key resource for acid lakes DCM, which traditionally has been underestimated in compare to nitrogen or phosphorus.