Abstract
This study tests the ecological and physico-chemical effect of sharp density boundaries of meromictic lakes. The investigation was carried out in Nohoch Hol, an anchialine meromictic cenote situated 2.0 km inland from the Caribbean coast of the Yucatan Peninsula, Mexico. In situ physico-chemical parameters were recorded with a water quality datalogger at depth intervals of 0.5 m. In addition, seven water samples for determination of nutrients, bacterioplankton and phytoplankton in the water column were obtained using SCUBA. Bacterioplankton and phytoplankton densities are low, with concentrations consistent with the oligo-to ultraoligotrophic status of Nohoch Hol indicated by the low nutrient concentrations. The phytoplankton was dominated by the chlorophyte Scenedesmus. Maximum concentrations of bacterio-and phytoplankton were found at 10.0 m depth, the top of the chemolimnion. The similarity analysis clustered the samples in three defined groups: (a) the mixolimnion, (b) the mid-and bottom of the chemolimnion and the monimolimnion, and (c) the top of the chemolimnion. The principal component analysis explained over 85% of the total variance in two components (PC). PC1 was related to turbidity and the aggregation of the chlorophytes at the top of the chemolimnion. PC2 was related to dissolved oxygen and the accumulation of filamentous and total bacteria also at the top of the chemolimnion. The top of the chemolimnion acts as a boundary within the water column to the exchange of dissolved and particulate matter between the mixo and the monimolimnion and as an ecological zone with a crucial role in the biogeochemistry of Nohoch Hol.
Original language | English (US) |
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Pages (from-to) | 107-127 |
Number of pages | 21 |
Journal | Hydrobiologia |
Volume | 677 |
Issue number | 1 |
DOIs | |
State | Published - Nov 2011 |
Funding
Acknowledgments Financial support was provided by the Dirección General de Asuntos del Personal Académico de la Universidad Nacional Autónoma de México through the Project PAPIIT-IN203894 ‘‘Ecología y biodiversidad de un sistema anquihalino basado en la producción quimioautotrófica’’. The authors thank: L. Peralta, M. Sánchez, L.A. Oseguera (PILT, FES Iztacala, UNAM), and V. Urbieta for field and laboratory assistance; B. Phillips and the QRSS for invaluable data and comments on Nohoch Hol underwater exploration and survey; and E. Monroy-Rios for drafting Fig. 1c. The comments from reviewers Eugene Perry and William Humphreys were valuable in significantly improving this communication.
Keywords
- Anchialine
- Anoxia
- Bacterioplankton
- Karst
- Nutrients
- Phytoplankton
- Sinkhole
- Tropical lake
ASJC Scopus subject areas
- Aquatic Science