Caballero Margarita, Vázquez Gabriela, Ruiz-Fernández Ana Carolina, Alcocer Javier, Mora-Palomino Lucy Natividad
Laboratorio de Paleolimnología, Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, México.
Instituto de Ecología, A.C., Xalapa, Veracruz, México.
PLoS One. 2025 Jul 24;20(7):e0327201. doi: 10.1371/journal.pone.0327201. eCollection 2025.
Lake degradation is an important environmental problem in the Neotropics, where rapid population growth is leading to increasing human impact. However, baseline studies in these lakes are still scarce. This study focussed on the hydrochemistry, trophic status and analysis of diatom diversity and ecological distribution in Neotropical karst lakes in southern Mexico, presenting a high-resolution paleolimnological reconstruction of changing hydrochemical and trophic characteristics since the late 1950s based on multiproxy analysis of a sequence dated by 210Pb and 14C. Four of the sixteen freshwater lakes had higher salinity (300-500 mg L-1), sulphates, turbidity and eutrophic conditions. These impacted, eutrophic to hypertrophic ecosystems receive soil-derived sediment, organic matter, urban and agricultural effluents through river inflow. Two diatom taxa were characteristic of these impacted lakes (Aulacoseira granulata var. angustissima and Stephanocyclus meneghinianus) while eight were preferentially present in the lower-salinity, oligo-mesotrophic lakes. Some of the lower-salinity taxa have restricted Neotropical karst distributions (Cyclotella petenensis, Discostella sp., Mastogloia calcarea and Planothidium sp.), and are in danger of local extirpation as hydrochemical changes and eutrophication increase. The beta diversity (βw) of the full data set was low (2.6), driven mostly by the hydrochemical and trophic status differences between the four most impacted lakes and the rest. Paleolimnological analysis allowed us to determine that the currently impacted lakes previously had lower salinity and trophic conditions, comparable with the currently non-impacted lakes. In Lake Peñasquito, increasing erosion during the 1970s was associated with the first appearance (1980s) and gradual increase of diatom taxa characteristic of lake degradation, and a critical transition point was observed in the diatom assemblages by ca. 2008.
湖泊退化是新热带地区一个重要的环境问题，该地区人口快速增长导致人类影响不断增加。然而，对这些湖泊的基线研究仍然匮乏。本研究聚焦于墨西哥南部新热带喀斯特湖泊的水化学、营养状态以及硅藻多样性和生态分布分析，基于对一个由210Pb和14C测年的序列进行多指标分析，呈现了自20世纪50年代末以来水化学和营养特征变化的高分辨率古湖沼学重建。16个淡水湖中有4个具有较高的盐度（300 - 500 mg L-1）、硫酸盐、浊度和富营养化状况。这些受到影响的、从富营养到超富营养的生态系统通过河流流入接收来自土壤的沉积物、有机物、城市和农业废水。两种硅藻分类群是这些受影响湖泊的特征（颗粒直链藻窄变种和梅内基尼 Stephanocyclus），而另外8种则优先出现在低盐度、贫 - 中营养湖泊中。一些低盐度分类群在新热带喀斯特地区的分布受限（佩滕小环藻、盘状硅藻属、钙质胸隔藻和平板藻属），并且随着水化学变化和富营养化加剧，面临着局部灭绝的危险。整个数据集的β多样性（βw）较低（2.6），主要由4个受影响最严重的湖泊与其他湖泊之间的水化学和营养状态差异驱动。古湖沼学分析使我们能够确定，目前受影响的湖泊以前盐度和营养条件较低，与目前未受影响的湖泊相当。在佩尼亚斯基托湖，20世纪70年代侵蚀加剧与湖泊退化特征的硅藻分类群首次出现（20世纪80年代）及逐渐增加相关，并且在大约2008年硅藻组合中观察到一个关键转折点。
