Macrophyte regional patterns, metrics assessment and ecological integrity of isolated ponds at Austral Patagonia (Argentina)

MANZO, L.M.; GRECH, M.G.; EPELE, L.B.; KUTSCHKER, A.M.; MISERENDINO, M.L.

THE SCIENCE OF TOTAL ENVIRONMENT

ELSEVIER

Año: 2020 vol. 727

0048-9697

Anthropogenic and natural changes are threatening pond ecological integrity in Patagonia and tools for bioassessment are required. Macrophytes are good candidates to determine the conservation status of ponds; nevertheless, metric selection procedures should be founded on an adequate knowledge of plant ecological responses. We assessed the main environmental constraints driving variation in macrophyte assemblages, and trophic status at 29 ponds located at the continental and insular Patagonia region. We screened 20 potential macrophyte metrics as indicators ofpond condition that included origin (native, endemic, exotic), lifeforms(annual/biannual, perennial), functional groups (submersed, emergent, floating-leaved, landforms), and community attributes. A set of 106 taxa were recorded, and richness per site (10 species) was unexpectedly high for a cold temperate area, reinforcing the value of isolated ponds as habitat for macrophytes in the Patagonian landscape. Natives dominated most assemblages; exotics were present at 24 ponds, contributing with high cover (>45%) at 15% of them. Macrophyte assemblages were driven by natural factors over anthropogenic ones, with temperature, rainfall, pH, conductivity and nutrients explaining most variation in patterns. However, pond eutrophication symptoms (high phosphorous concentration and chlorophyll a) were associated with extensive cattle grazing (manure and trampling) and urbanization (runoff). Generalized linear models captured natural variables (temperature, alkalinity) as most powerful explaining richness measures. Models also indicated that both richness of emergent and endemics were negatively affected by total phosphorous increases. Land cover factors: grasses/herbaceous, mallín and trees (%) in 100 mbuffer around ponds appeared as additional ecological drivers ofmac- rophyte patterns, particularly ofsubmersed (>50%) and native richness (36%). Natural and anthropogenic gradi- ents were overlapped, making it difficult to generalize our conclusions. Further studies are needed to test the performance ofthemacrophyte metrics selected here, which are a vital tool for the conservation ofthemost austral ponds in South America