| Popis: |
Examination of surface-associated protozoa in Great Lakes coastal marshes has been minimal, although they play crucial roles in nutrient and energy transfer in similar systems. Spatio-temporal patterns of artificial substrate-associated protist and bacterial abundances are related to physico-chemical conditions at this “freshwater estuary.” Assemblages were sampled monthly (May-October) at upstream, downstream, and at two mid-estuarine sites. A total of 278 protistan taxa were observed, and greatest richness occurred in late June. Richness at the estuary mouth was consistently higher than upstream, possibly due to the influence of Lake Erie assemblages and variability in hydrology-driven habitat characteristics. PCA yielded two components accounting for 90% of total variance in species by sites data. Species abundances at the two mid-estuarine sites were most highly correlated, and taxa seasonally abundant at any one site tended to be abundant at others. Presence/absence data were used to calculate community similarity indices, and a permutation-computed test statistic compared the mean similarity of triplicate substrates in one month (at a given site) to the between-month similarity. Significant differences (α = 0.05) between some months (site by site) were observed, with a unique assemblage noted in October. Following classification into six functional feeding groups, bactivores (mainly heterotrophic microflagellates) and primary producers (mainly cryptomonads and chlamydomonads) dominated assemblages. Organisms in other functional groups comprised only 10–15% of observed taxa. A preponderance of bactivorous taxa is consistent with observations of a dense and metabolically active bacterial community associated with abundant paniculate organic matter in easily -resuspended surficial sediments. |
