Patagonian deglaciation: aquatic macroinvertebrate biodiversity in proglacial and paraglacial ponds

Glacier retreat is rapidly transforming cryospheric landscapes with new pond networks establishing in deglaciated landscapes. However, our understanding of the aquatic biodiversity within these rapidly evolving landscapes has been limited, especially in southern Patagonia despite having the largest temperate icefields globally. We examined the aquatic macroinvertebrate diversity in paraglacial forest and proglacial ponds at the snout of the Exploradores Glacier (Southern Patagonia, Chile) and assessed the environmental factors influencing taxonomic richness and community composition. Alpha and estimated gamma diversity were significantly higher in periglacial forest ponds compared to proglacial ponds. Clear differences in macroinvertebrate community composition were recorded between paraglacial and proglacial ponds. Taxonomic turnover explained most of the variation in community composition with Trichoptera and Diptera taxa constituting a greater proportion of taxonomic richness in proglacial ponds, while Coleoptera and Hemiptera taxa represented a higher proportion of taxa in paraglacial forest than proglacial ponds. When taxa-environment relationships were examined, a significant negative association was recorded between dissolved oxygen and taxonomic richness. Sodium concentrations were also found to be negatively associated with LCBD. This study provides vital evidence that ponds formed naturally due to deglaciation can support a wide diversity of aquatic macroinvertebrates, and as glacial retreat continues and landscapes transition from glacial to paraglacial, pond habitats represent increasingly important freshwater habitats at the landscape scale. Future research is critical to advance understanding of proglacial and paraglacial pond networks to provide the underpinning information needed to raise awareness to support the conservation of these unique habitats.