Data Structure

Species richness was 536 (total number of species).

 

Beta diversity (the amount of compositional variation in the collection of samples): 10.3

What this means: Beta diversity can be thought of as the number of distinct communities in the collection of samples in a dataset. This analysis was done as a guide for further ordination analyses because a dataset with high beta diversity is more challenging for ordination. Beta diversity >5 is considered high, so there is less confidence in the analyses described below.

Six separate groups were identified in the non-hierarchal k-means cluster analysis based on diatom assemblage composition. Group one, dominated by Navicula germainii and Aulacoseira granulata was comprised of central basin rivers and one Sandusky River sample. Group two dominated by Cyclotella meneghenianaand Nitzschia inconspicua have assemblages with the lowest BDM scores and is comprised of western basin rivers and two samples from the Black River. Group three, dominated by A. minutissimum complex and Navicula gregaria was comprised entirely of samples from the Ashtabula and Conneaut systems. Group four, dominated by Cyclotella cryptica and Cyclostephanos invisitatus, contain assemblages with the highest BDM scores and is comprised of all harbor samples. Group five, dominated by Staurosira sp. 2 JCU and Staurosira sp. 1 JCU is a mix of samples. All but the two Portage River samples in this group are from harbors or within 1 mile of the river mouth. Group six, dominated by Nitzschia dissipata and Rhoicosphenia abbreviata, have assemblages with mixed BDM scores and is comprised entirely of samples from the Sandusky and Maumee systems.

K-means cluster chart displays site (san = Sandusky system; owc = Old Woman Creek system; grn = Grand River system; blk = Black River system; mau = Maumee River system; con = Conneaut River system; ash = Ashtabula River system; arc = Arcola Creek system; imm = Immergrum/Maumee Bay; ced = Little Cedar Point/Maumee Bay) , date, and river mile in parentheses (H = harbor) at left. Group number is indicated at right. BDM scores are shown along the bottom and indicated as dots for each sample.

The k-means cluster divides the samples into groups based on the similarity of the diatom assemblages within each group. Six groups provided the best fit for the k-means cluster with the samples in this study.