Recolonization of macroinvertebrates in a recovering urban lake (Onondaga Lake, Syracuse, NY): Analysis within communities of distinct aquatic macrophytes

Many of the biological communities in Onondaga Lake have recovered from more than a century of industrial and municipal pollution, which adversely affected the physical and chemical environment. To evaluate the recovery (2008-2012) of important littoral communities I: 1) evaluated changes in aquatic macrophyte communities; 2) investigated associated epiphytic macroinvertebrates within four plant communities in Onondaga Lake (predominantly monocultures of Stuckenia pectinata, Potamogeton foliosus, or Chara sp. and a heterogeneous community); 3) evaluated epiphytic macroinvertebrate communities in adjacent systems to identify source populations for recolonization; and 4) evaluated colonization by benthic macroinvertebrates on experimental substrates.;In the past decade aquatic macrophyte richness and distribution have increased substantially. With more than 17 species and 80% coverage documented in between 2008 and 2012. The associated epiphytic macroinvertebrates were similar in the Chara sp. and in the heterogeneous community, and were dominated by Amphipoda and Gastropoda. The most distinct epiphytic macroinvertebrate community in 2010 and 2011 was associated with S. pectinata; it was dominated by Chironomidae and Oligochaeta. In Onondaga Lake, the number of insects documented increased from 2010 to 2011, mostly at sites adjacent to the outlet/Seneca River. When the epiphytic macroinvertebrate community within Onondaga Lake was compared to connected systems I found that Onondaga Lake had a distinct community of gastropods and supported significantly fewer taxa of Ephemeroptera, Trichoptera, and Odonata, and pollution-intolerant insects. Despite the increased richness of aquatic macrophytes and epiphytic macroinvertebrates, the benthic macroinvertebrate community remained perturbed and had not changed in more than 20 years. Initial colonization (3 months after installation) of experimental substrates was dominated by Chironomidae, and colonization was mostly complete by the second sampling event (9 months). No taxa from adjacent systems colonized the substrate by the final sampling event (3 years 9 months). The results of these studies indicated the epiphytic community is recovering, but benthic macroinvertebrate colonization is limited. Dredging of contaminated sediment and habitat remediation, which began in 2012, will address much of the pollution and possibly facilitate the recovery of less pollution tolerant benthic and epiphytic macroinvertebrates.