Processes Influencing Water Quality in the Pine Knoll

UNC Chapel Hill Institute of Marine Sciences 2012 Capstone Research Project ENST 698 A"rac&on to Water —  ½ of world’s population lives within 100 km of ocean (World Health Organization, 2005) •  Coastal Counties −  17% U.S. total land area −  53% U.S. population −  + 23% from 1980-­‐2003 NOAA Population Trends as of Nov. 17, 2011
Demand for Waterfront Property —  Increases property value —  Large residential interest —  Boating access —  Recreational use —  Dredge and fill development —  Development leads to water quality degradation “The Grand Canal” Venice, Italy
Canals of Venice California, USA
Local Canal System: Pine Knoll Shores Town Growth —  + 135.9% population Pine Knoll Shores 1958
between 1980 and 2000 —  Changes in land use —  Increased development —  Decreased maritime forest cover Pine Knoll Shores 2012 —  Potential for increased runoff and anthropogenic inputs 1958 photograph courtesy of Tony Rodriguez, PhD
PKS Canal System Design —  Shape design maximized amount of waterfront properties —  Water flow not likely considered —  Made to harbor boats —  Easy access to Bogue Sound marina cul-­‐de-­‐sac marina Previous Studies in PKS —  1981: NC Shellfish Sanitation Division —  Shell fishing closed due to elevated coliform levels —  1984: Ritts and Larson —  Town hired DUML after closing of shell fishing Previous Studies —  1993: Schwartz et al. found 25 species of fishes and numerous species of invertebrates —  Canal system acts as a nursery for fishes —  1994: Kirby-­‐Smith et al. resampled fecal coliform levels found in 1981 —  Fecal coliforms serve as a proxy for pathogenic bacteria and viruses —  Areas determined to be impacted by fecal contamination Research Objec&ves —  Conduct an assessment of the water quality and movement of the PKS canal —  To observe the spatial and temporal variation of physical characteristics of the canal that impact chemical and biological aspects of water quality Analyze PKS canal system Recognition of study topics Groundwater Hydrodynamics Intrusion Flushing time Movement Shear Bacteria Nutrients NOx, NH4, PO4 TSS Vibrio sp. Combined effects and synthesis General recommenda&ons Fecal indicators Sample Sites Sample Site 1 Sample Site 2 Sample Site 3 Sample Site 4 Sample Site 5 Sample Site 6 Online Survey —  Brief survey sent to all residents —  Questions pertained to occupancy, fertilizer/
pesticide use, pet ownership, and boat use —  Approved by the Institutional Review Board at UNC to ensure anonymity of responses —  Responses analyzed using Survey Monkey Residency Number of people in Type of residents Short term
Residents
Seasonal
Residents
household 3 4 5 Permanent
Residents
2 1 Analyze PKS canal system Recognition of study topics Groundwater Hydrodynamics Intrusion Flushing time Movement Shear Nutrients NOx, NH4, PO4 Bacteria TSS Vibrio sp. Combined effects and synthesis General recommenda&ons Fecal indicators Groundwater —  Background —  Bulkheads prevent natural horizontal flow —  Freshwater lens —  Significance —  Freshening of canal —  Nutrient loading —  Influx of contaminants Groundwater —  Seepage meters —  Groundwater wells —  Radon transects Wells —  3 locations along the canal —  Use of pressure gauges to calculate water height —  Continuous data for 34 days Site 6: West Entrance (Oct 3) 0.3 0.2 Canal Water Eleva&on 0.1 0 -­‐0.1 -­‐0.2 Well Water Eleva&on 0:02 0:52 1:42 2:32 3:22 4:12 5:02 5:52 6:42 7:32 8:22 9:12 10:02 10:52 11:42 12:32 13:22 14:12 15:02 15:52 16:42 17:32 18:22 19:12 20:02 20:52 21:42 22:32 23:22 Water Eleva*on (m NAVD88) 0.4 Time (h:m) Longitude
Decays per minute/Liter
Latitude
PPT PPT Analyze PKS canal system Recognition of study topics Groundwater Hydrodynamics Intrusion Flushing time Movement Shear Nutrients NOx, NH4, PO4 Bacteria TSS Vibrio sp. Combined effects and synthesis General recommenda&ons Fecal indicators Importance of Hydrodynamics —  Properties of water are spatially variable —  Biological and chemical processes affected by circulation and transport —  Accumulation or dilution of persistent pollutants/
contaminants —  Dependent on: —  Flushing time: time for all water to be replaced in the system —  Age: amount of time since a water parcel has entered the system —  Bottom shear stress: measure of frictional force between the water and sediment DriWer Releases —  Released on sampling days and timed to catch tidal switch —  Passed over current profiler for comparison Height above bottom (m) Height above bottom (m) Rela&ve Movement Back of Canal Along Channel Velocity Cul de Sac Along Channel Velocity Time (day of year) Flushing Time —  Tidal prism method without return flow factor Canal Average Volume (V) Tidal Prism Volume (P)
(m3)
(m3)
177,278.4
118,151.3
Tidal Period (T)
(hrs)
Flushing Time (Tf )
(hrs)
12.5
18.8
Bathymetry —  V = average volume of the canal —  T = tidal period —  b = measure of return flow —  P = volume of the tidal prism Water Parcel Age Age of Water (days)
Age of Water
1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 12-Sep
3-Oct
8-Oct
11 2 3
3 4
4 5
Site
5 6
6 2
Shear Stress —  Measure of frictional force between water and sediment —  Greatest number of resuspension events occurring at back of the canal Time (day of year)
Combined Results —  Maximum distance traveled by a water parcel is longer than the canal system —  Implies fairly regular flushing for main canal —  Significantly different for cul-­‐de-­‐
sac Analyze PKS canal system Recognition of study topics Groundwater Hydrodynamics Intrusion Flushing time Movement Shear Nutrients NOx, NH4, PO4 Bacteria TSS Vibrio sp. Combined effects and synthesis General recommenda&ons Fecal indicators Water Quality —  Total suspended solids —  Nutrient concentrations —  Phytoplankton abundance —  Enterococcus sp. —  E. coli/ Fecal coliforms —  Total Vibrio —  Vibrio vulnificus —  Vibrio parahaemolyticus Field Methods —  Single grab samples were collected from the surface and bottom of each sample site —  Bottom samples were collected with a Van Doren 0.25 m from the sediment interface —  Aliquots from each sample were taken and used in the TSS, chl a, NOx, NH4+, PO4-­‐3, Fecal indicator bacteria, Enterococcus, E.coli, and Vibrio sp. analyses —  Temperature, turbidity, and conductivity (salinity) were also measured What we examined: —  Total suspended solids (TSS) – a measurement of the amount of particulate matter in the water —  Affects clarity and light penetration —  Chlorophyll a (chl a) – a primary pigment involved in photosynthesis —  Proxy for phytoplankton abundance —  Ammonium (NH4+) – the most bioavailable form of nitrogen, an essential nutrient —  Nitrogen oxides (NOx) – nitrates (NO3-­‐) and nitrites (NO2-­‐) —  Phosphate (PO4-­‐3) – an essential nutrient Methods —  TSS – samples were vacuum-­‐filtered onto a glass fiber filter, dried at 103°C to 105°C, and weighed on a mass balance —  Chlorophyll a (Chl a) – samples were filtered onto a glass fiber filter, extracted with acetone, and read on a Turner Trilogy Fluorometer —  Ammonium (NH4), nitrogen oxides (NOx), and phosphate (PO4) – nutrient concentrations determined using a Lachat Quick-­‐chem 8000 auto-­‐analyzer Total Suspended Solids (TSS) —  TSS levels in the canal, cul-­‐de-­‐sac, and control site exceed the limit of 20 mg/L for High Quality Waters —  Sources —  Soil erosion —  Particulates in runoff —  Suspended phytoplankton and zooplankton —  Resuspension of bottom sediment Chlorophyll a and Phytoplankton —  State standard concentration (40 μg/L) for estuaries not exceeded —  Chl a significantly higher in the cul-­‐de-­‐
sac, likely due to increased flushing time Phytoplankton in Bogue Sound —  Green bars indicate our observed temperatures —  ~5 μg/L chl a typical for Bogue Sound —  Control data from our study is similar to historical data collected for Bogue Sound Nutrients —  Ammonium levels very high in canal and cul-­‐
de-­‐sac —  NH4, NOx, PO4 significantly higher in canal and cul-­‐de-­‐sac Nutrient T
rends —  Back stretch of the canal —  High NH4 —  NOx and PO4 levels increase slightly —  Cul-­‐de-­‐sac —  Higher levels of nutrients, likely because of decreased flushing —  Control —  Lower nutrient levels – high rate of flushing, decrease in concentration of inputs, inputs quickly used
Analyze PKS canal system Recognition of study topics Groundwater Hydrodynamics Intrusion Flushing time Movement Shear Bacteria Nutrients NOx, NH4, PO4 TSS Vibrio sp. Combined effects and synthesis General recommenda&ons Fecal indicators Bacterial Enumera&on Methods —  IDEXX, a defined substrate technology, used to enumerate E.coli and Enterococcus in MPN/100 mL —  MPN = dilution based calculation of most probable number of bacteria reported as MPN/100 ml —  Culture methods used to determine CFU/100 mL for total Vibrio sp. , Vibrio vulnificus, and Vibrio parahaemolyticus Fecal Indicator Bacteria —  Indicators of fecal contamination used globally —  Approved by WHO and US EPA —  Indicate the presence of viral pathogens of concern (e.g. norovirus and enterovirus) —  Enterococcus (marine waters) —  E. coli (freshwater) —  Fecal coliform concentrations used to manage shellfish (oyster) harvesting waters —  FC = EC (roughly interchangeable) —  ~93% of FC in North Carolina are E.coli (Kirby-­‐Smith and Noble, unpublished data) Fecal Indicator Bacteria —  Oct. 22 -­‐ full tidal cycle —  Generally decreasing trend in E. coli over time —  Enterococcus on Oct. 8 significantly higher —  Resuspension E. Coli Abundance —  Recreational standard = 320 — 
— 
— 
— 
MPN/100mL —  Standard set at illness rate of <1% FC standard for shellfish harvesting waters = 14 MPN/
100mL Not due to rain events Concentrations generally higher across back west stretch E. coli mostly intolerant of salinity —  Source is either higher than mortality —  Possible reservoir (persistence) in system •  Not attributed to rain •  Control also high •  Sound-­‐wide event •  Resuspension of bottom sediments Impact of Wind Magnitude Fecal Indicator Bacteria The Genus Vibrio —  Native bacterial members of estuaries worldwide —  Nearly 100 described species, only a few pathogenic —  Most important seafood-­‐borne pathogens in the USA —  Pathogenic species include Vibrio vulnificus and Vibrio parahaemolyticus —  Virulent forms of pathogenic species can cause wound infections and blood poisoning —  Measured using culture based methods —  Vibrio sp. prefer warmer waters, generally 20-­‐30⁰C Total Vibrio sp. •  No significant difference between surface and bottom or among canal, cul-­‐
de-­‐sac, and control Salinity vs. Total Vibrio •  Pathogenic Vibrio sp. prefer salinities less than 24 ppt •  Pathogenic species of Vibrio relatively low concentrations •  For reference, Neuse River Estuary waters contain 100,000 cells/100 mL for V. vulnificus •  PKS has 400 cells/100 mL Water Quality Conclusions —  Nutrient concentrations significantly higher in canal than in control —  TSS exceeded standard for High Quality Waters —  Chl a did not exceed standard —  Cul-­‐de-­‐sac was significantly higher than canal and control —  E. coli higher in canal than in control —  Enterococcus likely in sediments —  Pathogenic Vibrio sp. are found in low concentrations and are likely not a concern Analyze PKS canal system Recognition of study topics Groundwater Hydrodynamics Intrusion Flushing time Movement Shear Bacteria Nutrients NOx, NH4, PO4 TSS Vibrio sp. Combined effects and synthesis General recommenda&ons Fecal indicators Flushing Time Impacts Biological Factors in the Canal —  Relatively fast flushing time (16-­‐18 hours) —  Quickly flushes out nutrient load —  May explain lack of correlation between nutrients and chl a 6% Fertilizer Use Yes 33% No 61% No Response Resuspension Impacts Biological Factors in t
he C
anal —  Water velocity and shear stress à resuspension —  Bacteria concentrations higher for bottom samples —  TSS high in canal and control across all dates and sites —  Strong wind and wave events à resuspension —  Enterococcus resuspended during wind event on Oct. 8 —  Canal dredging à increased resuspension à lower water quality Groundwater Impacts Biological Factors in the Canal —  Lower salinity across the back stretch due to dilution from groundwater inputs —  Change in salinity influences biological processes —  Higher E. coli across all bottom samples —  Likely a combination of groundwater infiltration and sediment reservoirs Cul-­‐de-­‐sac: A closed system Increased Light Availability Decreased Light Limitation Increased Chl a Age of Water (days) 6 Age of Water 5 4 12-­‐Sep 3 3-­‐Oct 2 8-­‐Oct 1 0 1 2 3 4 5 6 1 3 4 5 6 2 Site Groundwater accumulation Lower Salinity High Radon Levels Phytoplankton nutrient uptake Increased Chl a Main canal: An open system PKS Canal Higher nutrients Bogue Sound Phytoplankton TSS Enterococcus Vibrio Lower nutrients —  Chlorophyll a in canal below 40 µg/L standard —  Nutrient inputs being flushed out 1984
à
2012
— 
Potential for eutrophication is increasing with time 0.7 - 5.6 µg/L
à
1.7 - 25.8 µg/L
Ritts and Larson, 1984 Water Quality Assessment —  Enterococcus is a proxy for human health risk —  Chl a is a proxy for ecosystem health risk Chl-a and Enterococcus Relationship
80
Low ENT, High Chl a
High ENT, High Chl a
Low ENT, Low Chl a
High ENT, Low Chl a
Chl-a (µg/L)
60
40
20
0
0
1
2
3
Log Enterococcus MPN/100mL
4
Analyze PKS canal system Recognition of study topics Groundwater Hydrodynamics Intrusion Flushing time Movement Shear Nutrients NOx, NH4, PO4 Bacteria TSS Vibrio sp. Combined effects and synthesis General recommenda&ons Fecal indicators Recommenda&ons —  Further quantitative assessment of the impact of groundwater and contaminants (FIB) that may be contributed to canal system —  Limit nutrient inputs —  Reduce fertilizer applications, particularly ammonium-­‐based fertilizers —  Maintain a more natural landscape with native plants —  Check septic systems and leach fields regularly —  Look into potential sources of groundwater contamination —  Swim in the sound instead of the canal to avoid health risk —  Continue picking up pet waste —  Continue abiding by shellfish harvesting regulations Future Studies in PKS —  Bioassays for light limitation of phytoplankton —  Measure bacterial abundance in sediment —  Analyze grain size and sediment type —  Replicate water quality assessment in summer —  Higher temperatures, greater occupancy and canal usage —  Replicate assessment after storm events —  Capture runoff contamination —  Characterize connection between stormwater and groundwater Constructed Waterways —  The need for complete flushing of the system with tidal variations —  Limit cul-­‐de-­‐sacs —  Partially closed systems —  Allow for complete replacement of water —  Understand influence of groundwater and implications “In 1977, the canal was a place to swim, fish were abundant, shrimp was plentiful, oysters were edible.” – PKS resident Acknowledgements Johanna Rosman Stephen Fegley Rachel Noble Niels Lindquist Jaye Cable Jill Arriole Jihyuk Kim Benjamin Peierls Nathan Hall Lois Kelly Jeremy Braddy The Piehler Lab The Noble Lab The Paerl Lab The Rodriguez Lab Scott Sherrill PIKSO home owners association Chris Freeman and Dave Bernstein Bill Kirby-­‐Smith Joe Purifoy Stacy Davis Jim Hench Eamon Kromka The IMS faculty/staff The residents of Pine Knoll Shores Canal