15 May 2024
 | 15 May 2024
Status: this preprint is open for discussion.

Diatom diversity and distribution in neotropical karst lakes under anthropogenic stress

Margarita Caballero, Gabriela Vazquez, Javier Alcocer, and Lucy Natividad Mora Palomino

Abstract. Lake degradation is an important environmental problem worldwide, particularly in the neotropics where rapid population growth is leading to increasing human impact. However, baseline studies in neotropical lakes are still missing. This study focussed on hydrochemistry, trophic status and in-depth analysis of diatom diversity and ecological distribution in neotropical karst lakes, presenting a high-resolution paleolimnological reconstruction of changing hydrochemical and trophic characteristics in since the late 1950s. We studied sixteen freshwater lakes dominated by bicarbonates, calcium, and magnesium of which four had higher salinity (300–500 mg L-1), sulphate proportions, turbidity and eutrophic conditions. These lakes are considered impacted ecosystem that receive soil-derived sediment, organic matter, urban and agricultural effluents through river inflow. The βw diversity was low (2.6), driven mostly by the hydrochemical and trophic status differences between the four impacted lakes and the rest. Two taxa were characteristic of higher salinity, eutrophic lakes (Aulacoseira granulata var. angustissima and Stephanocyclus meneghinianus) and eight were preferentially present in the low-salinity oligo-mesotrophic lakes. Three of the diatom taxa (Discostella stelligera, A. granulata var. angustissima S. meneghinianus) are cosmopolitan species also present in non-karstic lakes in central Mexico with comparable salinity distributions. Contrastingly, four have restricted neotropical karst distributions (Cyclotella petenensis, Discostella sp, Mastogloia calcarea and Planothidium sp.), in danger of local extirpation as hydrochemical changes and eutrophication increase. C. petenensis described from the Peten Itza record, was present with high abundances in oligo-mesotrophic lakes of low salinity. Paleolimnological analysis allowed to identify that increasing erosion was associated with the first appearance and gradual increase of the diatom taxa characteristic of the impacted lakes since the 1980s, until reaching a critical transition in 2006, demonstrating that currently impacted lakes previously had lower salinity and trophic conditions, comparable with the currently non-impacted lakes.

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Margarita Caballero, Gabriela Vazquez, Javier Alcocer, and Lucy Natividad Mora Palomino

Status: open (until 26 Jun 2024)

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Margarita Caballero, Gabriela Vazquez, Javier Alcocer, and Lucy Natividad Mora Palomino

Data sets

Hidrogeoquimica de Lagos de Mexico. Margarita Caballero

Diatomeas de Lagos de Mexico Margarita Cabllero

Margarita Caballero, Gabriela Vazquez, Javier Alcocer, and Lucy Natividad Mora Palomino


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Short summary
This work evaluates limnological conditions and diatom diversity in 16 tropical lakes in southern Mexico. Impacted lakes showed higher lake productivity and chemical changes (higher salinity and sulphates). Diatom species indicative of human induced degradation were identified and degradation occurring in one of the lakes was documented using paleolimnological methods. This highlighted the risk that species of restricted distribution could be facing extirpation from their natural habitats.