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Federal Register / Vol. 86, No. 1 / Monday, January 4, 2021 / Rules and Regulations increased markedly Psomas 2007, p.
13. The UDWQ continues to monitor Utah Lake for any changes in salinity concentrations.
The effects of increased salinity concentrations on the various life stages of June suckers are unknown. Egg size, hatching success, and mean total length of larvae decreased as salinity levels increased for another lake sucker that occurs in Nevada, the cui-ui Chasmistes cujus; Chatto 1979, p. 7.
However, salinity concentrations were much higher in the cui-ui habitat than any recorded concentrations in Utah Lake.
Natural nutrient loading to the lake is high due to the nutrientand sedimentrich watershed surrounding the lake Fuhriman et al. 1981, p. 12.
Additionally, human development in the drainage increased the naturally high inflow of sediments and nutrients to the lake Fuhriman et al. 1981, p. 12.
Sewage effluent entering the lake accounts for 50, 76, and 80 percent of all nitrogen, total phosphorous, and ortho-phosphate, respectively Psomas 2007, p. 12. Phosphorus inputs to the lake 297.6 tons 270.0 metric tons per year exceed exports 83.5 tons 75.7
metric tons per year during all months of the year. Thus, the lake acts as a phosphorus sink, accumulating approximately 214 tons 194.1 metric tons annually Psomas 2007, p. 15.
These high nutrient loads increase the frequency and extent of large blue-green algal blooms, which greatly affect overall food web dynamics in Utah Lake Crowl et al. 1998b, p. 13. Blue-green algae is inedible to many zooplankton species, which decreases zooplankton abundance and its availability as a food source for the June sucker Landom et al. 2010, p. 19. Reductions in feeding rates translate into long-term effects such as decreased condition, growth rates, and fish survival Sigler et al.
1984, p. 7; Hayes et al. 1992, p. 9.
Furthermore, the increased algal biomass limits available light for submergent vegetation Scheffer 1998, p.
19, thus reducing refugial habitat for early life stages of June sucker. The frequency and size of algal blooms may be increasing based on large-scale algal blooms that occurred in 2016 and 2017
UDWQ 2017, p. 3.
Although there is a significant amount of research indicating that algal blooms can be harmful to many types of fish, we do not have direct evidence regarding the degree or manner in which they impact June suckers in Utah Lake Psomas 2007, p. 14; Crowl 2015, entire. No fish kills were documented during recent bloom events, but poststocking monitoring of June sucker has
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noted that, during algal blooms, fish movement decreased measurably Goldsmith et al. 2017, p. 13.
The average Utah Lake TDS
concentration is about 900 parts per million ppm/milligrams per liter mg/
L, but large variations occur, depending on the water year Hickman and Thurin 2007, p. 9. There is no evidence of direct mortality to June suckers due to higher salinity levels, but it is possible that increased salinity, when combined with increased nutrient input and turbidity, may negatively affect June suckers by reducing zooplankton and refugial habitat abundance as described above. Further study of June sucker responses during high salinity events is needed to better understand this relationship.
Water quality concerns in Utah Lake are being addressed through a largescale study and the formation of a steering committee and science panel to develop recommendations for Utah Lake water quality for the benefit of June sucker UDWQ 2017, entire.
Riverine Water Quality Prior to 1986, the year in which we listed the June sucker, riverine water quality was heavily impacted by water withdrawal, agricultural and municipal effluents, and habitat modification. The water withdrawals reduced the ability of the rivers to effectively transport sediments and other materials from the river channel. Furthermore, withdrawals influenced temperature, dissolved oxygen, and pollutant and nutrient concentrations Stamp et al.
2008, p. 18. Diverted streams with reduced, shallow summertime base flows are very susceptible to solar heating and can experience lethally warm water temperatures above 80
degrees Fahrenheit F or 27 degrees Celsius C, depending on life stage.
High water temperature, especially if combined with stagnant flow velocities, can lead to low dissolved oxygen levels in streams where flows have been reduced Stamp et al. 2008, p. 19.
Artificially high temperatures may also occur in streams where flow regime alterations and channelization have limited the recruitment of woody riparian vegetation, thereby reducing the amount of streamside shading Stamp et al. 2008, p. 19. Subsequently, extensive colonization by filamentous algae can occur in warmer temperatures, creating extreme daily dissolved oxygen fluctuations that are harmful to June sucker Service 1994, p. 12.
Agricultural and municipal effluents enrich production of algae, further impacting daily dissolved oxygen levels.
These effluents can cause fish kills if
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significant runoff from agricultural and municipal properties occurs during low flow periods. Furthermore, heavy algal growth can cause the armoring of spawning gravels and aid in the accumulation of fine sediments that degrade spawning habitat quality Stamp et al. 2008, p. 32.
The Provo River is listed on Utahs 2016 section 303d list for impairments harmful to cold-water aquatic life.
Additionally, water quality is poor in the rivers lower reaches during summer low-flow periods due to low dissolved oxygen levels and elevated temperatures Stamp et al. 2008, p. 34. It is likely that the recent supplementation of flows for June sucker recovery in the Provo River are minimizing the risk of lethal temperatures and dissolved oxygen fluctuations by providing water during critical periods and maintaining base flows throughout the summer while larvae are developing. The planned PRDRP will provide additional water storage and refugial habitat see Recovery, above.
Hobble Creek is not on the Utah section 303d list as an impaired waterbody. However, there are indications that total phosphorus and temperature may be problematic in Hobble Creek during certain times of the year Stamp et al. 2009, pp. 2223.
Average total phosphorous concentration is 0.06 ppm/mg/L, which exceeds the Utah indicator value of 0.05
ppm/mg/L Stamp et al. 2009, p. 24. In addition, creek temperatures exceed 68 F 20 C, which is the State coldwater fishery standard; this temperature increase typically occurs during summer days when air temperatures are high and flow in the channel is low Stamp et al. 2009, p. 26. Similar to the Provo River, the augmentation of stream flows in Hobble Creek has likely minimized the risk of lethal temperatures by providing flows during critical periods.
Effects of Climate Change The predicted increase in global average temperatures is expected to negatively affect water quality in shallow lakes Mooij et al. 2007, p. 2.
Turbid shallow lakes such as Utah Lake are likely to have higher summer chlorophyll-a concentrations with a stronger dominance of blue-green algae and reduced zooplankton abundance from the effects of climate change Mooij et al. 2007, p. 5. This could affect June sucker food resources since zooplankton are the primary food source for the species.
In Utah, an increase in the intensity of naturally occurring future droughts and unprecedented warming are
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