The presence and abundance of aquatic vegetation of streams in arid regions is relatively unknown, particularly in Arizona. Aquatic vegetation, or macrophytes, provide habitat, food sources, and nutrients to aquatic organisms. In order to better describe the role of macrophytes in such environments, we determined the relative presence of aquatic vegetation across four Arizona streams. We randomly designated 1,200 prepositioned aerial quadrats at 36 access points across the Blue river, the Verde river, Tonto Creek, and Eagle Creek, in the central Arizona area. The percentage of the area covered by aquatic vegetation was estimated in each quadrat. Each quadrat was then defined either as a riffle, run, or pool to determine the influence of macrohabitat on aquatic vegetation presence. Basic comparisons of the abundance of aquatic vegetation were made between the four streams by calculating the proportion of quadrats that had the presence of aquatic vegetation and the global average of those values. Of those proportions of quadrats with aquatic vegetation, respective to each stream, the proportions of quadrats within each macrohabitat description were calculated. Cluster and autocorrelation analyses in ArcGIS were executed by using a Moran’s I test on the aquatic vegetation cover values and the macrohabitat classifications.
Results/Conclusions
Proportion values for the Blue river (0.093) and Eagle creek (0.142) are below the global average (0.184), while the values for the Verde river (0.258) and Tonto creek (0.243) are well above that mark. This implies that the Blue and the Eagle have similar aquatic vegetation abundances, as well as the Verde and Tonto. Proportion values relative to macrohabitat have a similar pattern of low values for the Blue (0.071) and the Eagle (0.029) in pool macrohabitats, and higher values for the Verde (0.436) and Tonto (0.432). Values specific to riffle and run microhabitats posed no clear relationships. These patterns reflect how local streams may have similar aquatic vegetation abundances based on their location in the same watershed. Preliminary results for the spatial analysis show that there is some significant clustering of aquatic vegetation within the streams of interest. These results allow for the recognition that aquatic vegetation in streams of arid environments follow stream structure.