Free-living nematode distribution, abundance, diversity, and biological traits at Lake Bacalar were evaluated to assess the environmental quality of the water body. Using an Ekman grab, triplicate sediment samples were collected at 15 sampling sites. Nematodes were identified at family and genus levels, while abundance and diversity indices were calculated. Additionally, functional traits were calculated, and a PCA analysis was applied. The nematode fauna was represented by 6 orders, 18 families and 29 genera. Chromadorida had the highest number of taxa (9 genera), followed by Monhysterida (7 genera) and Enoplida (7 genera). Genera richness was higher at coarse sediments, with Simpson index values ranging 3.96−4.60, which were consistent with the Shannon index (H′ > 3 bits. ind⁻¹). The maturity index varied from 2.5 to 3.1, with a higher percentage of cp-3–5 nematodes (> 55%). Multivariate analysis showed three nematode groups, one associated with chlorophyll a, pH, salinity, and silicates, the second group with dissolved oxygen, and organic matter, and a third group related with nutrient content in water. Biological traits showed a dominance of deposit feeders (37%) and epistrate feeders (35%). Nematode body shape was represented by slender (39%), medium plump (31%), while conical tails were dominant (68%) and the body length varied from < 500 to 3000 µm, with dominance of lengths > 500−750 (46%) and > 750−1250 (38%), organisms typical of oligotrophic lakes. Nematode assemblages, water chemical characteristics, mainly nutrient concentrations, and biological traits confirm the oligotrophic conditions at Lake Bacalar.

评估了巴卡拉湖的自由生活线虫分布、丰度、多样性和生物特征，以评估水体的环境质量。使用 Ekman 抓斗，在 15 个采样点采集了三次沉积物样品。在科和属水平上鉴定了线虫，同时计算了丰度和多样性指数。此外，还计算了功能性状，并应用了 PCA 分析。线虫动物群由6目18科29属代表。Chromadorida 的分类群数量最多（9 属），其次是 Monhysterida（7 属）和 Enoplida（7 属）。粗沉积物属丰富度较高，辛普森指数值范围为 3.96-4.60，与香农指数（H' > 3 bits. ind ^-1）。成熟度指数从 2.5 到 3.1 不等，cp-3-5 线虫的百分比更高（> 55%）。多变量分析显示三个线虫组，一个与叶绿素a相关、pH、盐度和硅酸盐，第二组与溶解氧和有机物有关，第三组与水中的养分含量有关。生物学性状显示沉积饲养者（37％）和上皮饲养者（35％）占主导地位。线虫体型以细长 (39%)、中等丰满 (31%) 为代表，而锥形尾占优势 (68%)，体长从 < 500 到 3000 µm 不等，长度占优势 > 500-750 (46 %) 和 > 750−1250 (38%)，典型的贫营养湖泊生物。线虫组合、水化学特征、主要营养浓度和生物学特征证实了巴卡拉湖的贫营养条件。