Lower Ichetucknee Baseline Assessment

Transcription

1 Lower Ichetucknee Baseline Assessment September 2016 Prepared by The Howard T. Odum Florida Springs Institute

2 Lower Ichetucknee Baseline Assessment September 2016 Prepared by The Howard T. Odum Florida Springs Institute

3 Table of Contents Figures...iii Tables... iv Acknowledgements... 1 Section 1.0 Introduction Background... 2 Section 2.0 Methods Introduction Physical Environment Underwater Light Transmission Stream Discharge and Current Velocity Stream Segment Morphometry Secchi Disk Visibility Weather Station Water Quality Biology Plant Community Characterization Adult Aquatic Insects Snails Fish Turtles Human Use Ecosystem Level Monitoring Ecosystem Metabolism Nutrient Assimilation Community Export Section 3.0 Results Physical Environment Underwater Light Transmission Stream Discharge and Current Velocity Stream Segment Morphometry Secchi Disk Visibility Weather Station Water Quality Biology Plant Community Characterization General Faunal Observations Adult Aquatic Insects Snails Fish Turtles Human Use Ecosystem Level Monitoring Ecosystem Metabolism Nutrient Assimilation i

4 3.3.3 Community Export Section 4.0 Discussion Overview Ichetucknee Springs Updated Report Card Section 5.0 References ii

5 Table of Exhibits Figures Lower Ichetucknee Baseline Assessment Figure 1. Lower Ichetucknee River Ecological Baseline Project Location... 3 Figure 2. Lower Ichetucknee River Ecosystem Baseline Assessment Segment Station Locations... 5 Figure 3. Underwater LI COR sensor used to measure PAR... 6 Figure 4. Stream depth and velocity measurement along a cross-section of the Ichetucknee River Figure 5. Image of data sonde housing with holes that allow free movement of water, while the locking cap and cable provide security Figure 6. Trap used to collect adult aquatic insects as they emerge from the water Figure 7. Snail count example (0.32 m 2 frame) Figure 8. Example determination of ecosystem metabolism based on upstreamdownstream dissolved oxygen data (from WSI 2007) Figure 9. Image of plankton net capturing suspended material with flow meter upstream Figure 10. PAR percent transmittance (@ 1m) and diffuse attenuation coefficient estimates by station (July 2015, January 2016) Figure 11. PAR percent transmittance (@ 1m) and diffuse attenuation coefficient estimates by monitoring date Figure 12. Average PAR percent transmittance (@ 1m) for Florida spring runs Figure 13. USGS Ichetucknee Highway 27 near Hildreth, FL Monthly average discharge Figure 14. Annual rainfall record and discharge from USGS at US 27 ( ) Figure 15. Average dissolved oxygen concentrations in Florida springs near the spring vents Figure 16. Ichetucknee Spring and Spring Run - Daily average NOx-N concentrations Figure 17. Average nitrate nitrogen concentration in Florida springs Figure 18. Typical diurnal pattern for dissolved oxygen and ph in the Lower Ichetucknee River Figure 19. Upper Ichetucknee River aquatic vegetation transect summary (source FDEP) Figure 20. Estimated canopy cover on the Lower Ichetucknee River transects (July 2015) Figure 21. Lower Ichetucknee River bird survey Figure 22. Lower Ichetucknee River adult aquatic insect emergence rates compared to other Florida spring runs Figure 23. Lower Ichetucknee River fish density and biomass compared to other Florida springs Figure 24. Lower Ichetucknee River Human Use Summary July Figure 25. Comparison of ecosystem productivity and photosynthetic efficiency in Florida springs (based on historic and recent data from a total of 22 springs) Figure 26. Gross primary productivity efficiency versus discharge in Florida springs (based on historic and recent data from a total of 22 springs) Figure 27. Gross primary productivity efficiency versus NOx-N concentration in Florida springs (based on historic and recent data from a total of 22 springs) Figure 28. Lower Ichetucknee River estimated nutrient mass removals iii

6 Figure 29. Lower Ichetucknee River estimated nutrient mass removals by monitoring period Figure 30. Nutrient mass removals for Florida spring runs Figure 31. Particulate organic material export in Florida spring runs Figure 32. Ichetucknee Springs 2016 report card Tables Table 1. Lower Ichetucknee River flow measurements Table 2. Lower Ichetucknee River Physical Description (July 20 & 27, 2015) Table 3. Horizontal Secchi disk (ft) measurements in the Lower Ichetucknee River Table 4. Weather Summary - University of Florida FAWN Alachua Station Table 5. Lower Ichetucknee River average water quality grab sample results Table 6. Lower Ichetucknee River average water quality data sonde measurements Table 7. Lower Ichetucknee River aquatic vegetation summary overall average for the study segment (July 2015) Table 8. Lower Ichetucknee River aquatic vegetation transect importance value summary by station (July 2015) Table 9. Lower Ichetucknee River aquatic vegetation transect percent cover summary by station (July 2015) Table 10. Lower Ichetucknee River adult aquatic insect emergence rates Table 11. Lower Ichetucknee River viable apple snail egg count - July 12, Table 12. Lower Ichetucknee River snail (Elimia sp.) densities Table 13. Lower Ichetucknee River Snail (Elimia sp.) biomass estimates Table 14. Lower Ichetucknee River Fish Summary July Table 15. Lower Ichetucknee River Fish Summary January Table 16. Lower Ichetucknee River Fish Summary Table 17. Lower Ichetucknee River Turtle Summary July 19, Table 18. Lower Ichetucknee River ecosystem metabolism estimates Table 19. Lower Ichetucknee River particulate export iv

7 Acknowledgements Lower Ichetucknee Baseline Assessment The Howard T. Odum Florida Springs Institute gratefully acknowledges the financial support of the Fish and Wildlife Foundation of Florida, Inc. Ichetucknee Springs Baseline Assessment A Citizen-Science Project Tag Grant PFS for preparation of this report. Data collection in the Lower Ichetucknee River was accomplished with the help of the following project volunteers: Robert Brinkman, Jennifer Donsky, Paul Donsky, Jasmine Hagan, Janna Herndon, Scott Knight, Terri Lee, Jill Lingard, Charles Maxwell, Jeremy Merritt, David Moritz, Emily Ott, Debbie Segal, Brenda Wells, Lyrae Williams, Beth Zavoyski, and Eric Munscher s North American Freshwater Turtle Research Group. As with collection and analysis of all environmental data, techniques and interpretations may change over time. The raw data collected for this study are available from the Florida Springs Institute upon written request. The Director and staff of the Florida Springs Institute take full responsibility for any errors or omissions in this report. 1

8 Section 1.0 Introduction 1.1 Background Florida s 1,000+ artesian springs are undergoing rapid environmental changes due to a variety of stressors, including reduced discharge, increased nitrate-nitrogen levels, excessive recreation, side effects of aquatic plant management, and structural alterations. These changes result in a shifting ecological baseline for each spring. As the state embarks on comprehensive restoration activities at these springs, there is often little historic data available to assess recovery or continuing decline. The Howard T. Odum Florida Springs Institute (FSI) is embarking on a number of projects to document existing baseline ecological conditions in the springs of Florida. Data collected for these baseline assessments, in combination with ecological data from previous studies will be used to provide a continuing record of changes, both positive and negative, in Florida s endangered springs and spring runs. The Ichetucknee Spring run ecosystem from the US 27 bridge to its confluence with the Santa Fe River (Lower Ichetucknee River) is the focus of this baseline report (Figure 1). Ichetucknee Springs is located about 16 km (10 mi) northeast of Branford in Columbia and Suwannee counties. A total of nine named and several smaller unnamed springs form the Ichetucknee River, which together with surrounding lands are managed by the Florida State Park System as the Ichetucknee Springs State Park. 2

9 Figure 1. Lower Ichetucknee River Ecological Baseline Project Location 3

10 Section 2.0 Methods 2.1 Introduction Lower Ichetucknee Baseline Assessment Florida s springs and spring runs are composed of a diverse and interconnected ecosystem of physical, chemical, and biological components. While most biological systems vary considerably due to seasonal changes in sunlight, temperature, and precipitation, this variation is greatly reduced in spring-fed aquatic ecosystems due to their groundwater supply. These natural groundwater discharges demonstrate relatively consistent water temperature, inflow volume, and water chemistry (Odum 1957; Knight 2015). The one major environmental factor that is seasonally variable in springs is the input of solar energy. This seasonal variability must be considered in springs data collection and analysis. Spring ecosystem data collection occurred over two 2-week periods (July 22-29, 2015 and January 13-21, 2016) and included as many environmental variables as practical. The following ecological metrics were measured in the Lower Ichetucknee River Segment that was the location of this ecosystem baseline assessment (Figure 2): Physical Environment Insolation and photosynthetically active radiation (PAR) and underwater light transmission of PAR Stream discharge (water level and flow) and stream velocity Secchi disk visibility Segment morphometry (area and volume) Water quality field parameters (temperature, ph, dissolved oxygen, specific conductance) Water Chemistry Total Kjeldahl nitrogen [TKN], nitrate+nitrite nitrogen [NOx-N], and ammonia nitrogen [NH 4-N]. Total nitrogen [TN] and organic nitrogen [ON] were calculated.) Biology Plant community characterization (species, coverage) Macrofauna observations (species and counts) Adult aquatic insects (species and emergence rates) Human uses Ecosystem Level Ecosystem metabolism metrics (gross primary productivity [GPP], net primary productivity [NPP], community respiration [CR], P/R ratio, ecological efficiency) Nutrient assimilation Community export (fine particulate export) 4

11 Figure 2. Lower Ichetucknee River Ecosystem Baseline Assessment Segment Station Locations 5

12 2.2 Physical Environment Underwater Light Transmission Lower Ichetucknee Baseline Assessment Photosynthetically Active Radiation (PAR) underwater light transmission and attenuation coefficients were measured within the spring segment at each of the 15 stations in the Lower Ichetucknee River (Figure 2) using LI-COR brand sensors: LI-200SA (surface quantum sensor) and LI-192 (underwater quantum sensor). Figure 3 provides a typical light senor installation. A LI-200SA sensor was used to measure PAR energy reaching the water surface, while an underwater LI-COR LI-192 sensor was used to measure PAR energy at multiple water depths. The underwater PAR sensor was attached to a weighted frame and readings were logged at 15 to 30 cm (0.5 to 1 ft) depth intervals from the surface to the bottom of the water column. Measurements at each depth were collected following at least a ten second stabilization period. Light extinction (attenuation) coefficients were calculated from these data using the Lambert- Beer equation (Wetzel 2001): Where: Iz = Io(e-kz) Iz = PAR at depth z Io = PAR at the water surface k = diffuse attenuation coefficient, m -1 z = water depth, m Figure 3. Underwater LI COR sensor used to measure PAR 6

13 2.2.2 Stream Discharge and Current Velocity Lower Ichetucknee Baseline Assessment Stream discharge and velocity were measured at the upstream and downstream ends of the spring segment using a Marsh-McBirney Flo-Mate portable flow meter. At each location, a fiberglass tape was stretched across the stream channel perpendicular to the flow direction, allowing depth and velocity to be measured in approximately 25 evenly-spaced segments (Figure 4). At water depths less than 2.5 ft, velocity was measured at 0.6 of the water column. For water depths greater than 2.5 ft, velocity was measured at 0.2, 0.6, and 0.8 fractional depths of the water column. For each of the resulting cross-section sub-segments, velocity was multiplied by width and depth to calculate sub-segment discharge. The total discharge at each measurement transect was calculated from the cumulative discharge of all cross-section subsegments. Figure 4. Stream depth and velocity measurement along a cross-section of the Ichetucknee River Stream Segment Morphometry Water depths and stream widths were measured along transects at each of the 15 stations in the Lower Ichetucknee River (Figure 2). At each station, a fiberglass tape was stretched across the stream channel, allowing depths to be measured every 4 feet. These data were used to estimate the wetted surface area, mean depth, and water volume of each segment. Nominal hydraulic residence times were calculated in a spreadsheet for the spring segment based on these estimated water volumes and the upstream and downstream flow estimates. 7

14 2.2.4 Secchi Disk Visibility Lower Ichetucknee Baseline Assessment Water clarity was rapidly assessed using Secchi disk visibility, the distance where a white and black disk disappears from sight. In spring systems, this distance is commonly greater than the depth of the water column and Secchi disk visibility was measured horizontally. Secchi distance is measured with a 20-centimeter diameter black and white disk attached to the end of a tape measure and held below the surface of the water. A skin diver then extends the tape while moving away from the disk until it is no longer visible Weather Station Local area weather (rainfall, air temperature, solar radiation, and evapotranspiration) was estimated using the University of Florida Florida Automated Weather Network (FAWN, The FAWN network includes a total of 44 weather stations throughout Florida reporting weather data at 15-minute increments. The closest FAWN station to the Ichetucknee River Study Segment was southwest of the study segment, near Alachua (21 miles) Water Quality During each 2-week sampling period, field variables (water temperature, dissolved oxygen concentration, oxygen percent saturation, ph, conductivity and specific conductance) were measured and logged at 30 minute intervals using YSI 6920 recording data sondes. Oxygen data were collected using optical sensors with automated wipers, which improve calibration and reduce instrument drift during deployment. Data sondes were deployed near the middle of the water column at the upstream and downstream ends of the study segment for periods up to 2-weeks (Figure 5). Data sondes were calibrated prior to deployment and subsequent to their retrieval for each sampling period following the manufacturers protocol. Water chemistry samples were collected at the beginning and end of each study period, at the upstream, midpoint, and downstream stations. Water chemistry samples were collected as subsurface grabs. A rinsed water collection bottle was used to collect water samples from about 30 cm (1 ft) below the water surface and used to fill acid-preserved sample bottles. Following collection, samples were placed in an ice-filled cooler and delivered to the analytical laboratory for analysis within 24 hours. Water depth and field variables (temperature, dissolved oxygen, ph, and specific conductance) were also recorded during all water chemistry sampling events. Water chemistry samples were analyzed for total Kjeldahl nitrogen, nitrate+nitrite nitrogen, and ammonia nitrogen by Advanced Environmental Labs, Gainesville FL, (FDOH certified laboratory # E82620). 8

15 Figure 5. Image of data sonde housing with holes that allow free movement of water, while the locking cap and cable provide security. 2.3 Biology Plant Community Characterization The distribution and percent cover of aquatic plant communities (macroalgae and submerged aquatic vegetation) in the study segment were visually estimated during the baseline sampling events. Aquatic vegetative cover was documented along transects at each of the 15 stations in the Lower Ichetucknee River (Figure 2) using the line-intercept method. A tape measure was stretched along each transect, and all aquatic vegetation intercepting the vertical plane of line was recorded. Line-intercept data were used to estimate percent cover, frequency, relative cover, and relative frequency. Frequency was based on dividing each transect into 8 equal sized 9

16 sub-transects. Values by species were summed and averaged to yield an importance value as follows: Linear Cover Distance for Species A = line intercept distances for Species A (m) Linear cover distance of Species A (m) Percent Cover = x 100 Total transect distance (m) Linear cover distance of Species A (m) Relative Percent Cover = x 100 Total linear cover distance of all species (m) Number of subtransec ts in which Species A occurred Absolute Frequency = Total number of subtransec ts Absolute frequency of Species A Relative Frequency = x 100 absolute frequencie s of all species Relative Importance Value = Vegetative Cover Relative Frequency 2 Observed plants were identified to species or lowest practicable taxonomic classification. No quantitative plant biomass samples are collected Adult Aquatic Insects Aquatic insect species diversity and populations were characterized based on collections of adults as they emerge from the water. Insect emergence was measured through the use of floating pyramidal traps, each with a sampling area of 0.25 m 2 (Figure 6). The trap design is based on traps used for midge and mosquito sampling from wetland and aquatic environments (Walton et al. 1999). Each trap was constructed of wood and has four sides covered with fiberglass window screen. Flotation was provided by foam noodles attached along the bottom wooden supports. The traps work under the premise that insects emerging into the trap generally seek the highest spot and in the process travel through an inverted funnel into a 500 ml jar inverted over the end of the funnel. A total of up to ten traps were deployed at locations along the periphery of the spring run. At each location the substrate was noted. Traps were deployed and the jars containing the emergent insects collected at 24 to 48 hour intervals at the beginning and end of each study period. Insect identifications were made to the lowest practical taxonomic level. The number of insects captured in traps were used to calculate emergence rates and extrapolated across the wetted area of the study segments. 10

17 Figure 6. Trap used to collect adult aquatic insects as they emerge from the water Snails Quantitative snail population surveys were performed to target the snail populations in the spring segment at each of the 15 stations in the Lower Ichetucknee River (Figure 2). A 0.32 m 2 PVC frame was used to delineate each sample location and two replicate counts of visible snails in underwater photographs were made at each station (Figure 7). All snails were identified to the lowest practical taxonomic unit. A small number of snails were collected for measurement and weighing to provide data for biomass estimates. A visual survey for viable (unhatched) apple snail egg clutches was conducted between each of the 15 stations (totaling 14 segments) in the Lower Ichetucknee River (Figure 2). The number of viable egg masses and estimated clutch size (number of eggs per clutch) was documented along each shoreline for each segment Fish Visual surveys of the fish communities were made in the Lower Ichetucknee River along the length of the study segment (Figure 2). Multiple surveys of fish communities were made by three to five people using mask and snorkel gear. The fish observers started each count at an upstream location and worked their way downstream, traveling with the current. The spring 11

18 run segment was partitioned into approximately equal sections from bank-to-bank with one observer counting in each section. Observers noted the fish species or groups of similar species (lowest practical taxonomic level) of all observed fish, and these observations were reported to a data recorder, who followed the observers in a boat. Following each survey, observers estimated the total length (average and range) by fish species. Fish density was calculated for each sub-section by dividing the average number of individuals counted, by the area sampled. Biomass of fish species was estimated using published length-weight relationships (Schneider et al. 2000) and average species total lengths and numbers. Fish assemblage diversity was calculated using the Shannon-Wiener diversity index based on the calculated densities of individual species (Zar 1984). Figure 7. Snail count example (0.32 m 2 frame) 12

19 2.3.5 Turtles Lower Ichetucknee Baseline Assessment Quantitative monitoring of the aquatic turtle community was conducted on the portion of the study segment between LIR-4 and LIR-14 on July 19, 2015 by the North American Freshwater Turtle Research Group (NAFTRG). During each sampling event, turtle censuses were conducted by snorkelers who swam along the study segment, captured all observed turtles by hand or net, and delivered them to volunteers in the accompanying boats for data collection and recording. After capture, data were collected on turtle species and sex (using sexual differences in tail length and forefoot claw length). The aquatic turtle population density was reported as the number of individuals for each species divided by the surface area of the study segment Human Use Detailed observations of human use were made throughout the time that the study spring was visited. These observations were made only during day-light hours and for the visible portions of the spring run and surrounding upland areas. The count area is referred to as the observation area. Primary water contact activities were categorized as: wading (less than waist deep), bathing (greater than waist deep and less than neck deep), swimming, snorkeling, tubing, canoeing/kayaking, power boating, and fishing. Primary out-of-water activities included: sitting, walking, sunbathing, nature study, and picnicking. For each of these activity categories, the counts of all persons within the observation area were made at 15 minute intervals. Individual counts were multiplied by 0.25 hours (15 minutes) to estimate the average person-hours throughout the period of observation. The total human-use during a one-day period, reported in units of person-hours, was estimated as the sum of the 15- minute counts as follows: Where: t 2 t1 no. persons. dt = person-hours T = time (hours) t1 = time (start) t2 = time (finish) Person-hour estimates were in turn divided by the total observation interval in hours to estimate an average number of persons involved with in-water and out-of-water activities for each day of observation. Water and upland areas within the zone of observation were estimated from maps and aerial photographs to normalize data on a per-area basis: Human-Use Density = no. persons/area counted The resulting data were tabulated and reported as the average number of persons and humanuse density (persons per area) basis by activity and location. 13

20 2.4 Ecosystem Level Monitoring Ecosystem Metabolism Lower Ichetucknee Baseline Assessment Ecosystem metabolism was calculated in the spring segment using an Excel spreadsheet adaptation of the upstream/downstream dissolved oxygen (DO) change methods of H.T. Odum (1957a, 1957b). This method estimates and subtracts upstream from downstream DO mass fluxes corrected for atmospheric diffusion to determine the metabolic oxygen rate-ofchange of the aquatic ecosystem. Dissolved oxygen mass inputs typically include spring discharges, atmospheric diffusion into the water column (when DO is less than 100% saturation), accretion from other undocumented stream or spring seep inflows, and the release of DO as a by-product of aquatic plant photosynthesis. Oxygen losses include diffusion from the water column to the atmosphere (under super-saturated conditions), the metabolic respiration of the aquatic microbial, plant, and animal communities, and sediment biological oxygen demand. The downstream DO concentration measured at any time is the net effect of these gains and losses as shown in the following conceptual equation: Where: Δ DO = GPP CR + Din + A Δ DO = DO rate-of-change, g O 2/m 2 /d GPP = gross primary productivity, g O 2/m 2 /d CR = community respiration, g O 2/m 2 /d Din = diffusion into the water under unsaturated conditions, g O 2/m 2 /d A = accrual of DO from other spring boils, g O 2/m 2 /d The DO measurements used to estimate segment ecosystem metabolism were collected at the upstream and downstream end of the Lower Ichetucknee study segment at 30 minute intervals using recording YSI 6920 data sondes with optical DO sensors. Upstream and downstream dissolved oxygen data were each shifted by one-half of the estimated travel time between the upstream and downstream stream segment stations and an oxygen rate-of-change curve was prepared. Areas, volumes, current velocities and diffusion measurements were used to estimate ecosystem metabolism. Water surface area was estimated for the study segment using the survey methods described above and corrected hourly using an estimated stage: area relationship. Average velocities were estimated from the stage: volume relationship and spring discharge measurements. Nominal travel times for the water mass were estimated based on the length of the spring run and the estimated hourly current velocities. This DO rate-of-change curve is corrected for atmospheric diffusion based on measured percent oxygen saturation in the water, and oxygen diffusion rates corrected for water velocity. The corrected oxygen rate-of-change curve for each 24-hour period was used to estimate gross primary productivity (GPP), community respiration (CR), net primary productivity (NPP), production/respiration (P/R) ratio, and ecological efficiency. Figure 8 illustrates these metabolism measurements based on a typical oxygen rate-of-change curve. Descriptions of the ecosystem metabolism parameters follow below: 14

21 Gross primary productivity (GPP) is estimated as the entire area under the oxygen rate-of-change curve, calculated by extending the nighttime corrected oxygen rateof-change through the daylight hours and estimating the entire area under the daytime curve in g O 2/m 2 /d. GPP is a measure of all aquatic plant productivity occurring below the water surface within the stream segment. GPP includes primary productivity of both algae (including photosynthetic bacteria) and submerged vascular plants. Community respiration (CR) is the average of the corrected nighttime oxygen rateof-change values in g O 2/m 2 /d. CR is a measure of the total dark metabolism of the entire submerged ecosystem within each stream segment. CR includes the respiration of all microbes in the sediments and water column, respiration of bacteria, algae, and plants in the water column, and respiration of all aquatic animals, including protozoans, macroinvertebrates, crustaceans, and fish. Respiration of turtles, alligators, frogs, snakes, manatees, and other air-breathing aquatic fauna is not included in this calculation. Net primary productivity (NPP) is equal to the difference between these two estimates (GPP-CR). NPP provides an estimate of the net fixed carbon that remains each day after the respiratory needs of the aquatic ecosystem are met. CR may be higher than GPP in some streams and during some periods of time, indicating that there are unmeasured inputs of fixed carbon or losses of fixed carbon that were previously stored in the ecosystem. The P/R ratio or ecological quotient is equal to GPP/CR. A P/R ratio of one indicates that production and consumption are equally balanced. A ratio greater than one indicates an autotrophic aquatic ecosystem while a value less than one indicates a heterotrophic ecosystem. Photosynthetic efficiency (PE) is equal to the rate of gross primary productivity divided by the incident PAR during a specified time interval. It estimates the overall efficiency of an aquatic ecosystem to utilize the visible fraction of incident solar radiation, the principal forcing function for autotrophic stream ecosystems. PAR reaching the plant level is estimated based on river stage, the plant community characterization data for segment depth, and the light attenuation coefficient estimated for each sampling event. PE is reported as PAR Efficiency by dividing GPP in O 2/m 2 /d by mole/m 2 /d, resulting in units of g O 2/mole. PAR Efficiency is also reported as a percentage using the conversion factors employed by Knight (1980; 1983): 4.22 Kcal/g O 2 and Kcal/mole of photons (McCree 1972). 15

22 DO Rate-of-Change (g/m 2 /hr) Corrected DO Rate-of-Change (g/m 2 /hr) Dissolved Oxygen (mg/l) PAR (umol/m 2 /s) Lower Ichetucknee Baseline Assessment Upstream Downstream Air Plant Level 7 Air = mol/m 2 /d Plant Level = mol/m 2 /d 0 5/15/05 0:00 5/15/05 6:00 5/15/05 12:00 5/15/05 18:00 5/16/05 0:00 0 5/15/05 0:00 5/15/05 6:00 5/15/05 12:00 5/15/05 18:00 5/16/05 0: Corrected Uncorrected GPP = 8.45 g/m 2 /d CR = 8.40 g/m 2 /d /15/05 0:00 5/15/05 6:00 5/15/05 12:00 5/15/05 18:00 5/16/05 0: NPP = GPP- CR = g/m 2 /d PAR Eff. = GPP / PAR = 0.30 g O 2 /mol /15/05 0:00 5/15/05 6:00 5/15/05 12:00 5/15/05 18:00 5/16/05 0:00 Figure 8. Example determination of ecosystem metabolism based on upstreamdownstream dissolved oxygen data (from WSI 2007) Nutrient Assimilation Nutrient assimilation/dissimilation rates for total nitrogen, nitrate, and ammonia were estimated for the spring segment by calculating upstream-downstream changes in nutrient mass. Average nutrient mass inputs and outputs were estimated based on average water chemistry concentrations and flows over the period of study. Positive nutrient mass changes indicate assimilation/dissimilation of nutrients, while negative changes indicate an increase in nutrient mass with travel of the spring flow downstream Community Export Community export of particulate suspended matter was quantified for the study segment using a plankton net suspended in the current at mid-depth (Figure 9). The mesh size of the plankton net was 153 µm. Three replicate plankton net samples were collected at the upstream and downstream end of each segment. Sample material collected in the plankton net was rinsed into a sample bottle and returned to the laboratory for wet, dry, and ash-free (combusted at an oven temperature of 450 C) dry weight analyses. As samples were collected, the velocity of the water at the mouth of the net was measured as was the time of net deployment. These data allow calculation of the volume of water passing through the net. The amount of particulate material collected in the net was expressed on an area (based on upstream wetted surface area) basis. Particulate export results are reported as dry weight (DW) and ash-free dry weight (AFDW) per upstream area per time (g DW/m 2 /d and g AFDW/m 2 /d, respectively). Overall particulate 16

23 export for the study segment was calculated as the difference between the upstream and downstream export rates. Figure 9. Image of plankton net capturing suspended material with flow meter upstream 17

24 Section 3.0 Results 3.1 Physical Environment Underwater Light Transmission Lower Ichetucknee Baseline Assessment The input of solar energy is the one major environmental factor that is seasonally variable in springs. The influx of light is also the most important determinant of overall ecosystem primary productivity in clear-water springs. Light attenuation by dissolved and particulate matter in spring water limits solar energy available to submersed aquatic plants and other primary producers. Figure 10 and Figure 11 provide a summary of the measured Lower Ichetucknee River percent transmittance and diffuse attenuation coefficients by station and by monitoring date. Detailed light measurement data are provided in Appendix A. The percent transmittance between the stations averaged 61.5 percent at 1 m, ranging from 48.3 percent (LIR-1) to 87.2 percent (LIR-12), while the diffuse attenuation coefficient averaged 0.56 m -1 (range 0.14 to 0.97 m -1 ). The higher attenuation at LIR-1 was likely due to an increase in the suspension of particulate matter as a result of higher water velocities immediately downstream of the narrow US 27 bridge. The average percent transmittance for the entire spring run segment varied from 48.1 percent at 1 m (July 25, 2015) to 70.5 percent at 1 m (January 11, 2016) during the two baseline monitoring events. The diffuse attenuation coefficient ranged from 0.37 m -1 to 0.84 m -1 for the same time period. Light transmittance values from the study segment were compared to other spring run systems in Florida and showed similar ranges for average light transmittance values as shown in Figure 12. Light transmittance results from the Ichetucknee River since 2007 are also included in this figure; however, these were measured upstream of Highway 27 closer to the spring vents. Light transmittance values measured near spring vents generally are higher and show less variability than measurements farther downstream in the spring run. Much of this decline is the direct result of increasing particulate matter, resulting from the release of attached algal cells from plants and sediments from autotrophic production with distance downstream. This release of particulate matter in spring runs may also be the combined result of natural causes like primary productivity, current velocity, and human causes from physical disturbance and nutrification Stream Discharge and Current Velocity Spring discharge is second only to solar input as one of the most important forcing functions that regulates overall spring habitat support of plant, fish, and wildlife communities (Odum 1957a; Knight 2015). Stream discharge and velocity were measured at the upstream and downstream ends of the study segment using a portable flow meter. Table 1 provides a summary of discharges measured during the baseline assessment at the upstream and downstream ends of the spring segment, while Appendix B provides detailed discharge measurements. Stream discharges in the Lower Ichetucknee River study segment averaged 274 cfs and 279 cfs during the July 2015 and January 2016 events, respectively. Figure 13 provides a summary of monthly average discharge on the Lower Ichetucknee River since 1917 for USGS at US 27. Stream discharges at USGS averaged 341 cfs (range 164 cfs to 578 cfs) since 1917, displaying a general declining trend since about

25 Diffuse Attenuation Coefficient (m-1) Percent Transmittance 1 m) Lower Ichetucknee Baseline Assessment LIR-1 LIR-2 LIR-3 LIR-4 LIR-5 LIR-6 LIR-7 LIR-8 LIR-9 LIR-10 LIR-11 LIR-12 LIR-13 LIR-14 LIR LIR-1 LIR-2 LIR-3 LIR-4 LIR-5 LIR-6 LIR-7 LIR-8 LIR-9 LIR-10 LIR-11 LIR-12 LIR-13 LIR-14 LIR-15 Figure 10. PAR percent transmittance (@ 1m) and diffuse attenuation coefficient estimates by station (July 2015, January 2016) 19

26 Diffuse Attenuation Coefficient (m-1) Percent Transmittance 1 m) Lower Ichetucknee Baseline Assessment /20/2015 7/25/2015 7/31/2015 9/23/2015 1/11/2016 1/22/ /20/2015 7/25/2015 7/31/2015 9/23/2015 1/11/2016 1/22/2016 Figure 11. PAR percent transmittance (@ 1m) and diffuse attenuation coefficient estimates by monitoring date 20

27 Discharge (cfs) Percent Transmittance (1m) Lower Ichetucknee Baseline Assessment (Average ± 1 Std Dev) Figure 12. Average PAR percent transmittance (@ 1m) for Florida spring runs Monthly Discharge 200 Stats Discharge (cfs) Average 341 Median Maximum 578 Minimum 164 Discharge Std Dev 71.3 Discharge LOESS N 604 POR Feb Apr-2016 Jan-17 Sep-30 May-44 Jan-58 Oct-71 Jun-85 Feb-99 Oct-12 Jul-26 Month Figure 13. USGS Ichetucknee Highway 27 near Hildreth, FL Monthly average discharge 21

28 Table 1. Lower Ichetucknee River flow measurements Date Station Width (ft) Avg. Depth (ft) Discharge (cfs) USGS (cfs) 7/22/2015 LIR LIR /29/2015 LIR LIR /13/2016 LIR /21/2016 LIR LIR Stream Segment Morphometry Table 2 summarizes segment depth, area, and water volume estimated from Lower Ichetucknee River stream cross sectional depth profile data collected along the 15 transects (Figure 2). Detailed depth cross section measurements are presented in Appendix C. The wetted surface area and volume of the spring segment was 16.8 ac and 49.5 ac-ft, respectively. Nominal hydraulic residence time was estimated at 2.2 hours based on this estimated water volume and an average flow of 276 cfs during this period. Table 2. Lower Ichetucknee River Physical Description (July 20 & 27, 2015) Segment Volume 1 Area 1 Width Length 1 Avg Depth Max Depth (ac-ft) (ac) (ft) (ft) (ft) (ft) LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR Total ,473 Avg estimated between the beginning of one segment to the next LIR-6 not surveyed; estimated from aerial photography and neighboring stations USGS Stage (ft NGVD29): 7/20/ ; 7/27/

29 3.1.4 Secchi Disk Visibility Horizontal Secchi disk visibility measurements were collected on multiple dates at the upstream, midpoint, and downstream stations (Table 3). These measurements provide additional information concerning water clarity and the light attenuation properties of the water in the spring run. During the July 2015 monitoring events, Secchi disk visibility generally decreased from upstream to downstream, while the opposite was observed in January Table 3. Horizontal Secchi disk (ft) measurements in the Lower Ichetucknee River Date Upstream Midpoint Downstream 7/20/ /27/ /31/ /23/ /11/ /22/ Average Upstream: LIR-1/2; Midpoint: LIR-7; Downstream: LIR-12/ Weather Station Local area weather was estimated using the Alachua Station from University of Florida Florida Automated Weather Network (FAWN). Table 4 provides a summary of daily weather data collected for the months with baseline monitoring (July 2015 and January 2016). Table 4. Weather Summary - University of Florida FAWN Alachua Station Parameter Stats July 2015 January 2016 Air Temperature (C) Average Min Max Rainfall (in) Total Solar Radiation (W/m 2 ) Average Max Evapotranspiration (in) Total Long-term (97 year) average rainfall in the Ichetucknee Springshed is about 53 in/yr, and more recently is averaging about 52 in/yr (Figure 14). 23

30 Average Discharge (cfs) Annual Rainfall (in) Lower Ichetucknee Baseline Assessment Discharge Discharge LOESS Rainfall Rainfall LOESS Year Figure 14. Annual rainfall record and discharge from USGS at US 27 ( ) Water Quality Table 5 provides a summary of average water quality grab sample results at upstream (LIR-1), midpoint (LIR-7), and downstream (LIR-15) stations during the baseline monitoring events. Detailed water quality data are presented in Appendix D Average TN concentrations increased slightly from 0.70 mg/l at the upstream station to 0.72 mg/l at the downstream station. The predominant form of nitrogen was nitrate with an average low concentration of 0.55 mg/l at the downstream station to an average high concentration of 0.58 mg/l at the upstream station. Dissolved oxygen, ph, and water temperature increased from the upstream to downstream station, while conductivity remained relatively unchanged. Turbidity was low throughout the Lower Ichetucknee River segment with average measured values less than 0.3 NTU. Dissolved oxygen data from the study segment were compared to other Florida springs (near the spring vents) as shown in Figure 15. Figure 16 provides a summary of average daily NOx-N concentrations within the Ichetucknee River reported by the SRWMD, FDEP, and USGS. NOx-N concentrations averaged 0.74 mg/l, 0.77 mg/l, and 0.50 mg/l for the Head Spring, Blue Hole, and spring run at US 27, respectively. These data show an increase in nitrate at the head spring area from less than 0.1 mg/l in 1965 to 0.8 mg/l in Nitrate data from the study segment were compared to other Florida springs as shown in Figure

31 Table 5. Lower Ichetucknee River average water quality grab sample results PARAMETER GROUP PARAMETER UNITS LIR-UP LIR-MID JULY 2015 LIR- DOWN DISSOLVED OXYGEN DO % DO mg/l NITROGEN NH4-N mg/l NOx-N mg/l OrgN mg/l TKN mg/l U TN mg/l PHYSICAL ph SU SpCond umhos/cm Turb NTU 0.3 U TEMPERATURE Wtr Temp C JANUARY 2016 DISSOLVED OXYGEN DO % DO mg/l NITROGEN NH4-N mg/l U NOx-N mg/l OrgN mg/l TKN mg/l TN mg/l PHYSICAL ph SU SpCond umhos/cm Turb NTU 0.3 U 0.3 U 0.3 U TEMPERATURE Wtr Temp C

32 Dissolved Oxygen (mg/l) Lower Ichetucknee Baseline Assessment Figure 15. Average dissolved oxygen concentrations in Florida springs near the spring vents 26

33 NOx-N (mg/l) NOx-N (mg/l) NOx-N (mg/l) Lower Ichetucknee Baseline Assessment Ichetucknee Head Spring /1/1965 6/24/ /15/1975 6/6/ /27/1986 5/19/ /9/1997 5/2/ /22/2008 4/14/ /5/ Blue Hole Spring at Ichetucknee /1/1991 9/27/1993 6/23/1996 3/20/ /14/2001 9/9/2004 6/6/2007 3/2/ /26/2012 8/23/2015 5/19/ Ichetucknee River at US /1/1988 6/23/ /14/1998 6/5/ /26/2009 5/19/2015 Figure 16. Ichetucknee Spring and Spring Run - Daily average NOx-N concentrations 27

34 Spring ID Lower Ichetucknee Baseline Assessment Average NOx-N (mg/l) Ich Head Sp Blue Hole Spring ID Spring ID Spring ID Beecher Spring 1 Wakulla Tubing A/D-Tunnel 45 Blue Hole Spring (Columbia) 89 Newport Spring 2 Starbuck Spring 46 Cedar Head Spring 90 Green Cove Spring 3 Beckton Springs 47 Gadsen Spring 91 Orange Spring 4 Black Spring (Jackson) 48 Citrus Blue Spring 92 Waldo Spring 5 Columbia Spring 49 Weeki Wachee Main Spring 93 Warm Mineral Spring 6 Wakulla Tubing K-Tunnel 50 Double Spring 94 Suwannee Springs 7 Treehouse Spring 51 Jackson Mill Pond Spring 95 Welaka Spring 8 Cypress Spring 52 Wekiwa Springs 96 Nutall Rise 9 Turtle Spring 53 Falmouth Spring 97 Alexander Springs 10 Ellaville Spring 54 Otter Spring 98 Silver Glen Springs 11 Washington Blue Spring (Econfina) 55 Silver Spring Main 99 Steinhatchee River Rise 12 Wakulla Spring 56 Rock Springs 100 St. Marks River Rise (Leon) 13 Mill Pond 57 Rainbow Spring #6 101 Fern Hammock Springs 14 Salt Spring (Hernando) 58 Guaranto Spring 102 Juniper Springs 15 Hornsby Spring 59 Reception Hall Spring 103 Salt Springs (Marion) 16 Bugg Spring 60 Little River Spring 104 Washington Blue Spring (Choctawhatchee) 17 Holmes Blue Spring 61 Blue Grotto Spring 105 Crays Rise 18 Jackson Blue Hole Spring 62 Ginnie Spring 106 Santa Fe River Rise (Alachua) 19 Suwanacoochee Spring 63 Madison Blue Spring 107 Santa Fe Spring (Columbia) 20 Gator Spring (Hernando) 64 Gum Spring Main 108 Holton Creek Rise 21 Copper Spring 65 Sun Springs 109 Fenney Spring 22 Sanlando Springs 66 Devils Eye 110 Devils Ear Spring (Gilchrist) 23 Magnolia Spring 67 Owens Spring 111 Spring Creek Rise #1 24 Deleon Spring (Volusia) 68 Troy Spring 112 Spring Creek Rise #2 25 Mission Spring 69 Buckhorn Spring 113 Gainer Spring #1C 26 Chassahowitzka Spring Main 70 Crystal Springs 114 Morrison Spring 27 Hunter Spring 71 Mearson Spring 115 Big Spring (Big Blue Spring) (Jefferson) 28 Levy Blue Spring 72 Gilchrist Blue Spring 116 Wacissa Springs #2 29 Homosassa #2 73 Manatee Spring 117 Shepherd Spring 30 Branford Spring 74 Rainbow Spring #1 118 Allen Mill Pond Spring 31 Chassahowitzka Spring #1 75 Rainbow Spring #4 119 Brunson Landing Spring 32 Springboard Spring 76 Unknown Poe Spring 33 Wakulla Tubing C-Tunnel 77 Hart Springs 121 Tarpon Hole Spring 34 Ponce De Leon Springs 78 Lithia Springs Major 122 Gainer Spring #3 35 Wakulla Tubing D-Tunnel 79 Running Springs 123 Sulphur Spring (Hillsborough) 36 Homosassa #1 80 Rock Bluff Springs 124 Horn Spring 37 Homosassa #3 81 Telford Spring 125 Gainer Spring #2 38 Alapaha River Rise 82 Lafayette Blue Spring 126 Rhodes Spring #1 39 Siphon Creek Rise 83 Hays Spring (Jackson) 127 Rhodes Spring #2 40 Wakulla Tubing B-Tunnel 84 Jackson Blue Spring 128 Rhodes Spring #4 41 Bubbling Spring 85 Apopka Spring 129 Wakulla Tubing A/K-Tunnel 42 Little Springs (Hernando) 86 Shangri-La Springs 130 Volusia Blue Spring 43 Williford Spring 87 Fanning Springs 131 Natural Bridge Spring 44 Ichetucknee Head Spring (Suwannee) 88 Lafayette Ruth Spring 132 Figure 17. Average nitrate nitrogen concentration in Florida springs 28

35 Table 6 summarizes average field parameter data collected every 30 minutes with the water quality data sondes at the upstream (LIR-1), midpoint (LIR-7), and downstream (LIR-12) stations during the baseline monitoring events. Detailed time series plots are presented in Appendix D. Dissolved oxygen concentrations and ph were observed to vary in a diurnal pattern (Figure 18), showing a rise in concentration during the day due to primary productivity and decreasing concentrations at night as a result of community respiration. Table 6. Lower Ichetucknee River average water quality data sonde measurements PARAMETER GROUP PARAMETER UNITS LIR-UP LIR-MID LIR-DOWN July 20 31, 2015 DISSOLVED OXYGEN DO % DO mg/l PHYSICAL ph SU SpCond umhos/cm Turb NTU TEMPERATURE Wtr Temp C January 11 22, 2016 DISSOLVED OXYGEN DO % DO mg/l PHYSICAL ph SU SpCond umhos/cm Turb NTU <0.3 TEMPERATURE Wtr Temp C

36 DO (mg/l) ph (SU) Lower Ichetucknee Baseline Assessment DO (mg/l) ph (SU) :00 12:00 0:00 12:00 0:00 12:00 0:00 Figure 18. Typical diurnal pattern for dissolved oxygen and ph in the Lower Ichetucknee River Biology Plant Community Characterization The distribution and percent cover of aquatic plant communities (macroalgae and submerged aquatic vegetation) within the spring run at the Lower Ichetucknee River study area is summarized in Table 7 through Table 9. Detailed aquatic plant data are provided in Appendix E. A total of nine plant and algal species or groups were identified at the Lower Ichetucknee River monitoring transects during the July 2015 monitoring event. The most common species occurring were musk grass (Chara sp.), fanwort (Cabomba caroliniana), Tape grass (Vallisneria americana), and algae. Bare sand and rock had an average percent cover of approximately 68 percent, while all aquatic vegetation combined averaged 39 percent. A range of 2 to 5 aquatic vegetation species occurred within each of the 15 vegetation transects. Limited aquatic vegetation data is available for the lower Ichetucknee River, however the upper Ichetucknee River (Ichetucknee River State Park) has been surveyed since 1989 by FDEP (Figure 19). Findings from the FDEP 2015 survey identified strap-leaved sagittaria and tape grass as the most common vascular plant species in the upper Ichetucknee River (Sam Cole/FDEP, personal communication). While the percent coverage of aquatic vegetation increased from 46 percent in 1989 to 63 percent in 2015, the diversity of aquatic vegetation has decreased for the same period. 30

37 Table 7. Lower Ichetucknee River aquatic vegetation summary overall average for the study segment (July 2015) Total Linear Cover Frequency Importance Scientific Name Common Name Distance (m) Percent Relative Absolute Relative Value Chara sp. Muskgrass Cabomba caroliniana Fanwort Vallisneria americana Tape grass Algae Algae Fontinalis antipyretica Common Water Moss Najas guadalupensis Southern naiad Ludwigia repens Red ludwigia Hydrocotyle sp. Penny-wort Bacopa caroliana Bacopa Total

38 Table 8. Lower Ichetucknee River aquatic vegetation transect importance value summary by station (July 2015) Scientific Name Common Name LIR-1 LIR-2 LIR-3 LIR-4 LIR-5 LIR-7 LIR-8 LIR-9 LIR-10 LIR-11 LIR-12 LIR-13 LIR-14 LIR-15 Algae Algae Bacopa caroliana Bacopa 2.52 Cabomba caroliniana Fanwort Chara sp. Muskgrass Fontinalis antipyretica Common Water Moss Hydrocotyle sp. Penny-wort 2.30 Ludwigia repens Red ludwigia Najas guadalupensis Southern naiad Vallisneria americana Tape grass Total Table 9. Lower Ichetucknee River aquatic vegetation transect percent cover summary by station (July 2015) Scientific Name Common Name LIR-1 LIR-2 LIR-3 LIR-4 LIR-5 LIR-7 LIR-8 LIR-9 LIR-10 LIR-11 LIR-12 LIR-13 LIR-14 LIR-15 Algae Algae Bacopa caroliana Bacopa 0.05 Cabomba caroliniana Fanwort Chara sp. Muskgrass Fontinalis antipyretica Common Water Moss Hydrocotyle sp. Penny-wort 0.23 Ludwigia repens Red ludwigia Najas guadalupensis Southern naiad Vallisneria americana Tape grass Total

39 Average SAV Percent Cover / Diversity Lower Ichetucknee Baseline Assessment 80 SAG VAL MYR CHA LUD HYD HYM ZIZ RHY OTH Diversity SAG = Sagittaria kurziana CHA = Chara (prob.)zeylonica HYM = Hymenocallis rotata OTH = Others VAL = Valisineria americana LUD = Ludwigia repens ZIZ = Zizania aquatica MYR = Myriophyllum heterophyllum HYD = Hydrocotyle (prob.) verticillata RHY = Rhynchospora sp. or Carex sp. Year Figure 19. Upper Ichetucknee River aquatic vegetation transect summary (source FDEP) 33

40 Canopy Cover (%) Lower Ichetucknee Baseline Assessment Riparian shading (canopy cover of shoreline trees) was assessed within the spring run segment at each aquatic vegetation transect (Figure 2). Canopy cover ranged from 3 percent (LIR-14) to 75 percent (LIR-9) and averaged 22 percent over the spring run (Figure 20) LIR Station Figure 20. Estimated canopy cover on the Lower Ichetucknee River transects (July 2015) General Faunal Observations Multiple bird surveys were conducted on the Lower Ichetucknee River from US 27 to the confluence with the Santa Fe River. Along the spring run and upland areas, there was a total of 54 species observed (33 species in July 2015; 40 species in January 2016) [Figure 21]. The most commonly occurring species were the Carolina wren (Thryothorus ludovicianus), American crow (Corvus brachyrhynchos), Carolina chickadee (Poecile carolinensis), yellow-rumped warbler (Setophaga coronata), and American goldfinch (Spinus tristis). Detailed bird survey data are provided in Appendix F. 34

41 Number of Species Lower Ichetucknee Baseline Assessment Jul-15 Jan-16 Overall Survey Period Figure 21. Lower Ichetucknee River bird survey Incidental wildlife observations while conducting other monitoring include the following: Manatee observed in the lower section of the spring run (1/21/16) Deceased beaver observed near Midpoint Park (1/17/16) Adult Aquatic Insects Table 10Error! Reference source not found. presents a summary of adult aquatic insect emergence rates from the Lower Ichetucknee River spring run study segment. Insect emergence rates averaged 74 organisms/m 2 /d and 12 organisms/m 2 /d in July 2015 and January 2016, respectively. This equates to approximately 2,901,300 organisms/day over the study segment area on average. The most commonly collected insects were non-biting midges (Diptera), with 92% of the sample belonging to this family. Figure 22Error! Reference source not found. provides a summary of estimated adult aquatic insect emergence rates compared with other Florida spring run systems studied using the same emergent trap technique, including results from Ichetucknee Springs in 2009 (WSI 2010). The Lower Ichetucknee River study segment had a greater estimated emergence rate than eight of the other springs studied. 35

42 Emergence Rate (#/m 2 /d) Lower Ichetucknee Baseline Assessment Table 10. Lower Ichetucknee River adult aquatic insect emergence rates Deployment Date Order Suborder Family 7/20/15 7/27/15 Avg 1/11/16 1/21/16 Avg Diptera Nematocera Ceratopogonidae Chironomidae Dixidae Tipulidae Hemiptera Heteroptera Veliidae Lepidoptera Glossata Pyralidae Odonata Zygoptera Trichoptera Unidentified Total Emergence Rate (#/m²/d) Figure 22. Lower Ichetucknee River adult aquatic insect emergence rates compared to other Florida spring runs 36

43 3.2.4 Snails Lower Ichetucknee Baseline Assessment A visual survey for apple snail egg clutches was conducted during each monitoring event. Table 11 provides a summary of Florida apple snail egg counts conducted in July 2015 by segment (Figure 2). A total of 799 egg clutches was observed, averaging 29 eggs/clutch (23,155 eggs or 4.0 eggs/meter of shoreline). No viable apple snail eggs were observed during the January 2016 monitoring period. Table 11. Lower Ichetucknee River viable apple snail egg count - July 12, 2015 West Side East Side Total Segment # Egg Masses # Eggs Eggs / Mass # Egg Masses # Eggs Eggs / Mass # Egg Masses # Eggs Eggs / Mass , , , , , , , , , , , , , , , , , , Totals , , , Density * * Eggs per meter of shoreline Quantitative snail population surveys were performed to target the snail populations in the spring run using a 0.32 m 2 square frame (Table 12). Elimia were the only snail species observed averaging 485 snails/m 2 in the spring run, with the highest density observed at LIR-6 (1,531 snails/m 2 ) in July Snail biomass in the spring run averaged 146 g wet/m 2 (92.2 g dry/m 2 ). This equates to an estimated total of 32,978,545 snails in the spring run with an estimated wet weight of 9.9 metric tons (estimated snail dry weight 6.3 metric tons). Detailed snail survey data are provided in Appendix G. 37

44 Table 12. Lower Ichetucknee River snail (Elimia sp.) densities Snail Density (#/m 2 ) Station 7/22/2015 1/21/2016 LIR LIR LIR LIR LIR LIR LIR-6 1, LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR LIR Average Table 13. Lower Ichetucknee River Snail (Elimia sp.) biomass estimates Collection Date 7/27/2015 1/21/2016 Average Number of Snails Snail Wet Weight (g) Wet Weight / Snail (g) Snail Dry Weight (g) Dry Weight / Snail (g) Density (snails/m 2 ) Biomass (g wet/m 2 ) Biomass (g dry/m 2 ) Fish Table 14 presents the fish survey from July 2015 and Table 15 presents the fish survey from January Detailed fish data are provided in Appendix H. A total of 19 fish species or groups of similar species were observed with 18 species in July 2015 and 13 in January Individual segments ranged from 5 to 11 species over the period of study. Fish density in the spring run averaged 822 fish/ac with 1,419 fish/ac in July 2015 and 345 fish/ac in January 2016 (Table 16). Minnows (Notropis sp.), sunfish (Lepomis sp.), largemouth bass (Micropterus salmoides), 38

45 and spotted suckers (Minytrema melanops) were observed at the highest densities over the study period. Total estimated fish biomass averaged 27 lbs/ac with 28 lbs/ac in July 2015 and 25 lbs/ac in January A higher Shannon-Wiener diversity index for fish was observed in January 2016 (H = 2.16) compared with July 2015 (H = 1.15). Estimated fish biomass and population densities were compared with other Florida springs (includes spring boils and spring runs) studied using the same visual count technique, including results from the Ichetucknee River in 2009 (WSI 2010). Figure 23 visually displays this comparison of the Lower Ichetucknee River study segment fish population estimates to other Florida spring runs. For the study segment, the estimated fish densities were within the middle range of other studied springs. For fish biomass, the Lower Ichetucknee River study segment had a lower estimated fish biomass compared to all but one of the other springs studied. 39

46 Table 14. Lower Ichetucknee River Fish Summary July /21/15 7/28/15 Average Scientific Name Common Name Count Density (#/ac) Biomass (lbs/ac) Count Density (#/ac) Biomass (lbs/ac) Count Density (#/ac) Biomass (lbs/ac) Acipenser oxyrinchus Sturgeon Erimyzon sucetta Lake Chubsucker Esox sp. Pickeral Etheostoma sp. Darter sp Fundulus seminolis Seminole Killifish Fundulus sp. Killifish sp Ictalurus natalis Catfish Lepisosteus platyrhincus Florida Gar Lepomis sp. Sunfish sp. 2, , , Micropterus notius Suwannee Bass Micropterus salmoides Largemouth Bass 1, , , Minytrema melanops Spotted sucker Notemigonus crysoleucas Golden Shiner Notropis sp. Minnows 19,694 1, ,540 1, ,117 1, Poecilia latipinna Sailfin Molly Pomoxis nigromaculatus Black Crappie Strongylura marina Atlantic Needlefish Trinectes maculatus Hogchocker Total 24,379 1, ,288 1, ,834 1, Shannon Wiener Diversity Index (H') Survey area: 16.8 ac 40

47 Table 15. Lower Ichetucknee River Fish Summary January 2016 Scientific Name Common Name Count Density (#/ac) Biomass (lbs/ac) Erimyzon sucetta Lake Chubsucker Esox sp. Pickeral Etheostoma sp. Darter sp Fundulus seminolis Seminole Killifish Lepomis sp. Sunfish sp. 1, Micropterus notius Suwannee Bass Micropterus salmoides Largemouth Bass Minytrema melanops Spotted sucker Notemigonus crysoleucas Golden Shiner Notropis sp. Minnows 2, Strongylura marina Atlantic Needlefish Trinectes maculatus Hogchocker Mugil sp. Mullet Total 5, Shannon Wiener Diversity Index (H') 2.16 Survey area: 16.8 ac Table 16. Lower Ichetucknee River Fish Summary Density (#/ac) Biomass (lbs/ac) Scientific Name Common Name Jul-15 Jan-16 Average Jul-15 Jan-16 Average Acipenser oxyrinchus Sturgeon Erimyzon sucetta Lake Chubsucker Esox sp. Pickeral Etheostoma sp. Darter sp Fundulus seminolis Seminole Killifish Fundulus sp. Killifish sp Ictalurus natalis Catfish Lepisosteus platyrhincus Florida Gar Lepomis sp. Sunfish sp Micropterus notius Suwannee Bass Micropterus salmoides Largemouth Bass Minytrema melanops Spotted sucker Notemigonus crysoleucas Golden Shiner Notropis sp. Minnows 1, Poecilia latipinna Sailfin Molly Pomoxis nigromaculatus Black Crappie Strongylura marina Atlantic Needlefish Trinectes maculatus Hogchocker Mugil sp. Mullet Total 1,

48 Biomass (lbs/ac) Density (#/ac) Lower Ichetucknee Baseline Assessment 10, , , , Figure 23. Lower Ichetucknee River fish density and biomass compared to other Florida springs Turtles In July 2015, a total of 5 species and 25 individual turtles were captured, with loggerhead musk (Sternotherus minor) being the most common (Table 17). This results in an estimated turtle population density of 2.0 turtles/ac for this section of the spring run. Detailed capture data are 42

49 provided in Appendix I. Turtle population estimates of 13 turtles/ac have been reported on the upper Ichetucknee River within the State Park by Chaplin et al (2010). Table 17. Lower Ichetucknee River Turtle Summary July 19, 2015 Adult Juvenile Unknown Common Name Species F M Unk Unk F M Unk Total Red-eared Slider (Hybrid) Trachemys s. elegans Florida Red-bellied Turtle Pseudemys nelsoni Loggerhead Musk Sternotherus minor River Cooter Pseudemys cocinna Yellow-bellied Slider Trachemys s. scripta Unknown Total Density (#/ac) Survey area: 12.6 ac Human Use Figure 24 provides a summary of total in-water and out-of-water activities in July 2015, while detailed activities are summarized in Appendix J. Very little human use activity was noted during the January 2016 monitoring events. The location and activities of the 5 individuals observed during monitoring activities in January 2016 are tabulated in Appendix J. Based on these results, it is concluded that this area of the Ichetucknee River receives higher levels of human activity during the warmer season (July 2015), particularly during the weekend survey periods. In July 2015, in-water activities averaged 2.2 people/ac during the weekday and 10 people/ac during the weekend survey (Figure 24), with wading, power boating, and tubing being the most common activities. 43

50 Average # People/ac Lower Ichetucknee Baseline Assessment Out-of-Water In-Water Hodor Pointe Hodor Pointe Hodor Pointe 7/22/2015 7/25/2015 Total Wednesday Saturday Figure 24. Lower Ichetucknee River Human Use Summary July Ecosystem Level Monitoring Ecosystem Metabolism Table 18 provides a summary of ecosystem metabolism parameters collected in the study segment with detailed results in Appendix K. Average GPP ranged from 4.72 g O 2/m 2 /d (January 2016) to 8.58 g O 2/m 2 /d (July 2015) over the study period. CR ranged from 4.87 g O 2/m 2 /d (January 2016) to 7.76 g O 2/m 2 /d (July 2015), resulting in an average NPP of g O 2/m 2 /d in January 2016, to 1.00 g O 2/m 2 /d in July For these data the estimated P/R ratio ranged from 1.00 (January 2016) to 1.14 (July 2015), and the photosynthetic efficiency ranged was from 3.76% (or 0.47 g O 2/mol) in January 2016 to 4.09% (or 0.51 g O 2/mol) in July Ecosystem metabolism estimates from the study segment were compared to similar data from other Florida springs that have previously been studied (Figure 25). This comparison indicates that the study segment has similar GPP, NPP, and CR values compared to other spring systems. When normalized for the amount of incident solar radiation, the study segment was found to have a photosynthetic efficiency about average to other Florida springs. Figure 26 and Figure 27 shows the existing data relating photosynthetic efficiency, spring discharge, and NOx-N concentration for the studied Florida spring systems. The study segment follows the same general relationship observed for other springs. In general, spring photosynthetic efficiency increases with increasing spring discharge (Figure 26), while NOx-N concentration may have a subsidy-stress effect on photosynthetic efficiency (Figure 27). 44

51 Table 18. Lower Ichetucknee River ecosystem metabolism estimates PAR Efficiency (%) PAR Efficiency (g O2/mol) Stats GPP (g O2/m 2 /d) NPP (g O2/m 2 /d) CR (g O2/m 2 /d) P/R Ratio PAR (24hr) (mol/m 2 /d) July 21 30, 2015 Avg Max Min January 12 21, 2016 Avg Max Min

52 P P-75 AVG P-50 SITE P P Ichetucknee Segment July 2015 January GPP (g O2/m2/d) -20 NPP (g/o2/m2/d) 0 CR (g O2/m2/d) 0 P/R Ratio 0 PAR (24hr) (mol/m2/d) 0 GPP Efficiency (%) 0 GPP Efficiency (g O2/mol) Figure 25. Comparison of ecosystem productivity and photosynthetic efficiency in Florida springs (based on historic and recent data from a total of 22 springs) 46

53 Average GPP Efficiency (%) Lower Ichetucknee Baseline Assessment y = x R² = LIR (July 15) 4 LIR (Jan 16) Average Discharge (cfs) Figure 26. Gross primary productivity efficiency versus discharge in Florida springs (based on historic and recent data from a total of 22 springs) 47

54 Average GPP Efficiency (%) Lower Ichetucknee Baseline Assessment y = x x R² = LIR Inlet NOx-N (mg/l) Figure 27. Gross primary productivity efficiency versus NOx-N concentration in Florida springs (based on historic and recent data from a total of 22 springs) Nutrient Assimilation Figure 28 provides a summary of the average mass removals in the study segment with details provided in Appendix L. The mass of TN increased by an average of 1.8 lbs/ac/d within the study segment with OrgN increasing by 4.3 lbs/ac/d. The mass of NOx-N was reduced by 2.7 lbs/ac/d while NH 4-N slightly increased within the study segment (-0.1 lbs/ac/d). Figure 29 provides a summary of mass removals by monitoring period. The mass of TN, OrgN, and TKN decreased in the study segment during July 2015 (7.6, 10.3, and 10.3 lbs/ac/d, respectively) and increased in January 2016 (4.0, 1.8, and 2.4 lbs/ac/d, respectively). The mass of NOx-N was reduced during both periods (July 2015: 2.6 lbs/ac/d and January 2016: 2.7 lbs/ac/d) while NH 4-N showed an increase (0.4 lbs/ac/d, July 2015) and decrease (0.2 lbs/ac/d, January 2016) in the study segment. Nutrient mass removal data from the study segment were compared to other Florida spring runs as shown Figure 30. This comparison indicates that the study segment nitrogen mass removal rates are within ranges observed in other Florida springs. 48

55 Mass Removal (lbs/ac/d) Mass Removal (lbs/ac/d) Lower Ichetucknee Baseline Assessment NH4-N NOx-N Org N TKN TN Figure 28. Lower Ichetucknee River estimated nutrient mass removals Jul-15 Jan-16 Jul-15 Jan-16 Jul-15 Jan-16 Jul-15 Jan-16 Jul-15 Jan-16 NH4-N NOx-N Org N TKN TN Figure 29. Lower Ichetucknee River estimated nutrient mass removals by monitoring period 49

56 Mass Removal (lbs/ac/d) Mass Removal (lbs/ac/d) Mass Removal (lbs/ac/d) Mass Removal (lbs/ac/d) Lower Ichetucknee Baseline Assessment NH NOx TKN TN Figure 30. Nutrient mass removals for Florida spring runs 50

57 3.3.3 Community Export Community export data for the study segment are summarized in Table 19 with detailed data provided in Appendix M. Segment particulate organic matter export rates varied widely. Positive values indicate a net production of detrital material (material leaving the study segment), while negative values indicate a net accrual of detrital material (material being deposited in the study segment). For July 2015, organic matter export rates were positive for both events (2.69 g/m 2 /d and 0.76 g/m 2 /d), and the January 2016 events were negative (-0.74 g/m 2 /d and g/m 2 /d). Particulate organic matter export data from the study segment were compared to other Florida spring runs as shown Figure 31. Table 19. Lower Ichetucknee River particulate export Date Station Dry Matter (g/d) Organic Matter (g/d) Dry Matter (g/m 2 /d) Organic Matter (g/m 2 /d) 7/22/2015 Up 45,220 25, Down 338, , Segment 292, , /29/2015 Up 38,072 20, Down 121,534 62, Segment 83,462 41, /13/2016 Up 92,749 48, Down 13,249 8, Segment -79,500-40, /21/2016 Up 133,878 75, Down 9,948 5, Segment -123,930-69, Segment Areas = Up - Head Spring to LIR-4 (185,039 m 2 ); Down - Head Spring to LIR-15 (239,677 m 2 ); LIR-4 to LIR-15 (54,638 m 2 ) 51

58 Organic Matter Export g/m 2 /d) Lower Ichetucknee Baseline Assessment Figure 31. Particulate organic material export in Florida spring runs 52

59 Section 4.0 Discussion 4.1 Overview The Lower Ichetucknee River baseline study segment was about 1.8 miles in length, had a wetted surface area of about 16.8 ac, a water volume of about 53 ac-ft, and an average water depth of 3.2 ft. The 2015/2016 monitoring data reported during this baseline study from the Lower Ichetucknee River indicate that this segment is impaired in several respects, but nonethe-less, retains a relatively healthy ecological structure compared to other spring runs. Average flows in the Ichetucknee River have been declining since the 1970s. The baseline flows averaged 276 cfs compared to a period-of-record average flow of 341 cfs (a 19% decline). Dissolved oxygen concentration in the Lower Ichetucknee River are generally above 5 mg/l, ph varies around 7.8 standard units, temperature is about 20 o C in the winter and 22 o C in the summer, and specific conductance varies around 340 us. Nitrate+nitrite nitrogen concentrations at the springs feeding the Ichetucknee River average about 0.8 mg/l, about 16 times higher than background levels of this nutrient (about 0.05 mg/l) and 2.3 times higher than the Florida numeric springs standard of 0.35 mg/l. However, these nitrogen concentrations are considerably lower than other major springs in the Santa Fe and Suwannee River drainages (e.g., Fanning Springs at about 5 mg/l and Gilchrist Blue Spring at 2.1 mg/l). The Upper Ichetucknee River ecosystem does naturally attenuate the nitrate+nitrite nitrogen concentration to an average of about 0.5 mg/l at the US 27 bridge, which was the upstream boundary of the Lower Ichetucknee River baseline study segment. A small amount of additional nitrate+nitrite assimilation was measured in the study segment (about 45 lbs/d). Based on the results of other Florida spring studies, declining flow and elevated nitrogen are often associated with ecological changes. The Lower Ichetucknee Segment with relatively high spring inflows and lower nitrogen contamination than other springs, has a relatively low natural cover of submerged aquatic plants (about 39% overall) and low cover by filamentous algae (about 2%). Eight species of aquatic vascular plants were relatively common in this study reach, indicating an above average plant diversity. This plant community supports moderate to low levels of aquatic insects, snails, fish, turtles, and mammals. Gross ecosystem primary productivity was moderate (about 7 g/o 2/m 2 /d), resulting in elevated summer particulate algae export and lowered underwater visibility. Photosynthetic efficiency of this plant community is in the moderate range, averaging about 4%, supporting the other evidence of a moderately healthy spring run ecosystem. Human use of the Lower Ichetucknee River is highest on spring weekends and generally much lower during week days and during colder months. 4.2 Ichetucknee Springs Updated Report Card The updated 2016 Ichetucknee Springs report card is presented in Figure 32 with detailed data provided in Appendix N. The 2016 environmental health of Ichetucknee Springs and River is quantitatively rated as slightly below average. 53

60 ICHETUCKNEE SPRINGS AND RIVER ENVIRONMENTAL HEALTH REPORT CARD 2016 GRADE C- F Spring Discharge 306 cfs Discharge (cfs) D C B D F Water Clarity D C 61 % Percent 1 meter B A B F Nitrate 1.00 D 0.79 mg/l C Nitrate-N (mg/l) 0.40 B 0.20 A 0.00 D F 30 D C Fish Biomass (kg/ha) Fish Biomass (kg/ha) B A F F D C B A Submerged Aquatic Vegetation 54 % Percent Cover & Diversity B F D C B A Photosynthetic Efficiency Photosynthetic Efficiency (%) C Figure 32. Ichetucknee Springs 2016 report card 54