The key role of the chemolimnion in meromictic cenotes of the Yucatan Peninsula, Mexico

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 physicochemical 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.

Subaqueous speleothems (Hells Bells) formed by the interplay of pelagic redoxcline biogeochemistry and specific hydraulic conditions in the El Zapote sinkhole, Yucatán Peninsula, Mexico

“…In redoxclines below the photic zone the microbial community is dominated by chemolithoautotrophs, with a considerable amount of chemoautotrophic production and dark CO 2 fixation (e.g., Grote et al, 2008;Jørgensen et al, 1991;Jost et al, 2010;Noguerola et al, 2015). The development of pelagic redoxclines was also reported for deep density stratified cenotes of the YP (e.g., Socki et al, 2002;Stoessell et al, 1993;Torres-Talamente et al, 2011).…”

“…They are common throughout the YP, connecting the subterranean cave system with the surface (Bauer-Gottwein et al, 2011). For more detailed information about the formation and occurrence of cenotes on the YP we refer the readers to Torres-Talamente et al (2011) and Schmitter-Soto et al (2002).…”

Subaqueous speleothems (Hells Bells) formed by the interplay of pelagic redoxcline biogeochemistry and specific hydraulic conditions in the El Zapote sinkhole, Yucatán Peninsula, Mexico

“…The development of pelagic redoxclines was also reported for deep density stratified cenotes of the Yucatán Peninsula (e.g. Socki et al, 2002;Stoessell et al, 1993;Torres-Talamente et al, 2011) .…”

Planktonic Cyanobacteria of the tropical karstic lake Lagartos from the Yucatan Peninsula, Mexico

“…The clear water in this karstic water body can be attributed to dense macro-algae growth: C. glomerata and Chara sp., which serve like nutrients sink and as a factor to reduce sediment resuspension (Moss 1990, Scheffer 1998, despite to be a water body frequently mixed because of the dominant winds from the region. On the other hand, the nutrient concentrations were from one to two orders of magnitude higher than other water bodies of the State of Quintana Roo (Alcocer et al 1999, Schmitter-Soto et al 2002, Torres-Talamante et al 2011, and a remarkably high DIN:SRP ratio (mean value 94) suggests a permanent P-limitation in Lagartos according to Danielidis et al (1996). Although limitation by phosphorus is usual in eutrophic water bodies, the seasonal patterns in Lagartos were more similar to secondary phosphorus limitation like in eutrophic lakes with excessive nitrogen input (Reynolds 1984).…”

“…High nutrient input can cause eutrophication and a remarkable diminution in the water quality with the concomitant loss of phytoplankton biodiversity, much of it unknown until now. Recent studies particularly focused on taxonomic composition of phytoplankton communities of sinkholes and anchialine caves, have highlighted the importance of inland water bodies to harboring a large freshwater micro-algae diversity (López-Adrian & Herrera-Silveira 1994, Sánchez et al 2002, Schmitter-Soto et al 2002, Torres-Talamante et al 2011. However, there are not any references on planktonic or benthonic micro-algae communities structure and seasonal succession in coastal lakes from the Mexican Caribbean Sea shoreline.…”