Hydrological modification drives century-scale eutrophication and invasion increasing invertebrate assemblage heterogeneity in Lake Fúquene, Colombia

Hydrological alteration, eutrophication and macrophyte invasion generate
novel ecological states and biotic homogenisation in shallow lakes. As
these stressors increasingly co-occur and unfold over decades to
centuries, disentangling their combined effects on invertebrate
assemblages remains however, challenging. To assess their long-term
(decades-centuries) interactions on driving aquatic invertebrates, we
analysed three ²¹⁰Pb-dated sediment cores spanning contrasting dominance
of the invasives Egeria densa (submerged), Pontederia crassipes (floating)
and Azolla filiculoides (floating) in Fúquene, a largely-drained,
eutrophic Andean shallow lake (Colombia). Eighteen invertebrate taxa were
recorded with multivariate analyses explaining 51% of assemblage variation
and identified a pre-1800 mesotrophic phase; a drainage phase (1800–late
1980s) marked by shifts towards eutrophic taxa; and a post-perimeter canal
phase (post-1990) characterised by invasive expansion and distinct
macrophyte-associated invertebrate assemblages. Despite restructuring,
invertebrate assemblages did not homogenise but became more heterogeneous
among cores in Zone 3. Variation partitioning revealed strong coupled
hydro-chemical–macrophyte effects at the assemblage and taxon level
explaining 13–56% of the variation, with invasive growth forms uniquely
accounting for 5–40%. E. densa stands supported aquatic insects, whereas
floating species favoured Oribatidae, bryozoans and semi-terrestrial
chironomids. Invasion–eutrophication-driven homogenisation is therefore
not inevitable but contingent on hydrology, environmental variation and
growth-form diversity.