The combined influences of urban runoff, dreissenid mussel invasion, and shoreline hardening have created conditions favorable to overgrowth of the nuisance alga Cladophora in the Great Lakes. Cladophora is an attached green alga native to the Great Lakes, estuarine, and marine waters. Excessive growth of Cladophora has been linked to decreased survival of juvenile salmon in western rivers, fouling of whitefish commercial and tribal fishing nets, harboring the avian and human pathogens, including the botulism pathogen responsible for massive bird die-offs, clogging irrigation systems, and it is considered indicative of poor shoreline water quality. Little is known, however, about how the resident biological communities (e.g., microbes, macroinvertebrates) of the Cladophora ecosystem have altered lakewide food webs. In this research, we seek to identify spatial and temporal patterns in microbial communities and other organisms associated with Cladophora mats present in urban areas of Lake Michigan. Cladophora samples were collected at four urban and semi-urban sites around southern Lake Michigan; samples were scanned microscopically and analyzed using whole genome sequencing analysis. Algal subsamples were agitated, and the resulting elutriate was filtered through a 0.2 um polycarbonate filter, and DNA was extracted from filters using commercial extraction kits. Samples were selected for an initial shotgun metagenomic sequencing run on an Illumina NextSeq500; sequence chemistry enabled maximum read lengths of 150 bp, and both ends of each fragment were sequenced to generate paired-end reads. With this new and advanced technology, we identify a highly diverse community of organisms, including microalgal and bacterial epiphytes that in turn may support higher trophic assemblages (e.g., fish larvae).
Number of untrimmed reads generated per sample ranged from 26,101,374 to 60,891,592. Initial results revealed a diverse community dominated by bacterial species, Proteobacteria in particular. Among eukaryotes, Bacillariophyta dominated, as also seen microscopically as an epiphytic species. The role of Cladophora in harboring nutrients and providing food sources to larval and prey fish is unknown, but preliminary findings indicate that it may be considerable, given the diversity and richness of biological communities harbored. Further research is needed to understand the potentially diverse roles of Cladophora for managing excessive growth while maintaining a level that is critical for preserving a healthy lake ecosystem.