Variations in microcrustacean (Crustacea: Cladocera, Copepoda) assemblages from selected groundwater-dependent ecosystems in the greater Luzon and Mindoro Island faunal regions (Philippines): insights to tropical groundwater ecology

In the Philippines, the ecology of microcrustaceans from groundwaters and their dependent ecosystems remain poorly understood, yet knowledge about this group can elucidate patterns in groundwater biodiversity to develop sound conservation policies. In this study, microcrustaceans were studied by collecting samples from 102 groundwater-dependent ecosystems, including 51 artesian wells, 23 caves, 14 springs, and 14 piped groundwater pumps during the dry (Nov 2014 to Apr 2015) and wet (May–Oct 2015) seasons. Results indicate the presence of 21 species from Cladocera and Copepoda, including 2 obligate stygobionts and 19 species consist with surface water and facultative stygobiotic taxa. Significant differences in microcrustacean assemblages were noted among types of groundwater-dependent ecosystems (P < 0.05), wherein wells and caves harbored more abundant assemblages with higher total species richness; however, no significant variations were observed between seasons (P > 0.05). Furthermore, principle component analysis revealed that sampling sites were highly characterized by altitude, specific conductivity, and total water hardness. Microcrustacean assemblages in sampled sites were highly dominated by the influence of temperature, dissolved oxygen, and altitude. Species rarefaction analysis revealed low species richness in sampled sites within the region, supporting the existing notion that temperate groundwater-dependent ecosystems were more diverse, and faunal composition in terms of ecological groups is extremely different in tropical and temperate settings.