A multi-spatial analysis and the balanced requirements of freshwater mussels (Bivalvia: 4 Unionidae) and urban inhabitants in the Cuyahoga River watershed

18 Water quality in the Cuyahoga River, a national heritage river of the United States, has improved

112 Land use, soil, and elevation datasets were clipped to fit the HUC 12 watershed boundaries for 113 the Cuyahoga River watershed. Mussel data collected in summer 2021 were uploaded to ArcGIS 114 as a shapefile and each site was projected as a point with size reflecting the number of live 115 mussels found (Fig. 2). 116 The hydrology toolset was used to analyze watershed features. Small imperfections in the 117 elevation DEM were corrected using the Fill tool, after which Flow Direction created a raster of 118 water path from each cell to its steepest downslope neighbor. Flow Accumulation characterized 119 the addition of water from land proceeding from headwaters to the river mouth, determined by 120 adding the weight for all cells that flow into each downslope cell. An optional weight factor of 1 121 was chosen and pour points were snapped closest to each survey site.  Within the Upper Cuyahoga River (Table 1), freshwater mussels declined significantly 158 over time (log 10 live mussels = 28.6 -0.014 years, P = 0.025). The 122 live mussels and 128 159 shells in 2021 were fewer than observed in 1990 and 2012, even with surveys broadened to 160 include a stretch of river downstream (Fig. 1a), confirming and extending concerns apparent in

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In Tinkers Creek, 158 live mussels and 609 shells were found in 2021, which was not 170 many more than for the Upper Cuyahoga River, but this stream is slightly smaller and previously 171 possessed fewer in initial surveys two decades earlier (Table 1) This manuscript is a preprint and has not been peer reviewed. The copyright holder has made the manuscript available under a Creative Commons Attribution 4.0 International (CC BY) license and consented to have it forwarded to EarthArXiv for public posting. license EarthArXiv 178 179 Watersheds and Land Use 180 Multiple parks and green spaces border the Upper Cuyahoga River, making much of the 181 surrounding land use largely of forest and cropland (Fig. 3). Yet, across sites, land use showed 182 no significant relationship with mussel abundance either at a large (sub-watershed) or small 183 (buffer) scale (Suppl. Fig. 1), perhaps because most sites in 2021 had few to no mussels even 184 where the proportion of development nearby was low. The area of the West Branch Cuyahoga 185 River from which numerous mussels were found (Fig 2) had a relatively high proportion of 186 developed land (0.11-0.37). Although forested lands (0.29-0.61) predominantly surround the 187 East Branch Cuyahoga River and the upper main stem, which is labeled as the Cuyahoga River 188 proper after these two streams converge, half of all these sites lacked records of mussels in the 189 recent surveys.

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A higher proportion of land around Tinkers Creek was assessed as developed (Fig. 3), 191 with forest characterizing the upper reaches. However, many sites from these developed 192 (residential) areas supported mussels, which produced an unexpected positive, although weak, 193 relationship between mussel abundance and proportion developed lands (r= 0.298; p<0.05), and 194 concurrently, a negative relationship to forest (r = -0.294; P < 0.05) at both the large (sub-195 watershed) and small (100 m-buffer) scales. While no mussels were found in surveys below the 196 escarpment (Fig 2), none were previously known from this region.

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Concurrently with land use, mussel abundance corresponded with variation in soil 198 drainage type. Few live mussels in either stream occurred in areas identified to have poorly 199 drained (type B/D) soils (Fig. 4), which are indicative of wetland habitats. Soils described as 200 excessively drained (types A & B) also had low mussel numbers compared to moderately well 257 But high in the Tinkers Creek watershed, regional parks embarked on significant improvements 258 to flow [39], which eliminated anoxic wetland-type conditions observed in the early survey, and 259 mussels now occur higher in the watershed than before. Creek often had a sand substrate and a mixed 281 flow, a typical riffle, run, pool presentation; and they had more mussels. Wooded riparian banks 282 likely helped but were not required.

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That mixed habitat provides a stark contrast to anoxic conditions downstream in the 284 Upper Cuyahoga River where sediments drained poorly, and one could periodically smell the 285 sulfur when the sediment was disturbed. The outcome is that the Upper Cuyahoga River, lacking 286 flood events, has shown no sudden catastrophic loss that could be attributed to a specific cause, 287 but instead, a slow, insidious decline in mussel abundance. Tinkers Creek and the West Branch 288 Cuyahoga River, with their natural hydraulic flow, sustained an assemblage of mussels that has 289 shifted to traditional riverine species, especially after the implementation of land improvement 290 measures that extended beyond water quality.

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This manuscript is a preprint and has not been peer reviewed. The copyright holder has made the manuscript available under a Creative Commons Attribution 4.0 International (CC BY) license and consented to have it forwarded to EarthArXiv for public posting. This manuscript is a preprint and has not been peer reviewed. The copyright holder has made the manuscript available under a Creative Commons Attribution 4.0 International (CC BY) license and consented to have it forwarded to EarthArXiv for public posting. license EarthArXiv