Characterizing diatom assemblages in ponded wetlands

Arne D. Hultquist
2012
Using biological assemblages for evaluating ecosystem integrity is dependent upon robust sampling techniques that adequately characterize the species composition. This thesis evaluated the performance of a wetland surface-sediment diatom collection methodology. The methodology did not result in collection of 95% of species present due to the richness of rare species in the ponded wetlands. However, because rare species added little to relative abundance, the method provided a community
more » ... community characterization that separated the communities based upon ponds within complexes and ponds between complexes. The mantel test indicated species distribution was dependent upon pond and complex (p<.001) with a model matrix of dissimilarity based upon 0, within pond, ½, within complex, and 1, between complex. The Multi-response Permutation Procedure supported the method's ability to separate complexes based upon communities (p=.012). The significant p-value is attributed to the very large affect size (A=.45) which adds further credence to the method's efficacy. Nonmetric Multidimensional Scaling ordination was used to graphically interpret the separation of ponds. The ordination shows sizeable separation between complexes, considerable separation between most ponds within a complex, and relatively little separation between replicates. Culling rare species further improved the ordination with 91% of the variance explained by 2 axes with a stress of 7.35 and a probability of obtaining that stress by a chance of p=.004. The sampling methodology also provided an assemblage that correlated with biotic and abiotic environmental variables. The Mantel test indicated correlation with water chemistry variables (r=0.564, p=0.028) after controlling for vegetation variables. Vegetation variables also correlated with the diatom community (r=0.700, p=0.001) after controlling for chemical variables. Correlation increases for groups of environmental variables emphasizes the abilities of the Mantel test and BIOENV over ordination techniques in ponded wetlands when the factors influencing the community composition are working as a consortium. However, the ordination is still useful because it indicated the diatom community corresponds with our knowledge of shallow lake ecology where biotic and abiotic factors work as a consortium. The sampling methodology could provide another tool for environmental assessment and enhance our ability to deduce wetland status and promote desired wetland biota. iv
doi:10.26053/0h-5rnk-fmg0 fatcat:vaclppzhmrbvvd4zvibxes4jfy