Sources for Bottom Water Phosphates and Suspended Sediments in Southern Cayuga Lake, New York Prabighya Basnet Hobart & William Smith Colleges Geneva, NY
Outline of Today’s Presentation • Introduce Problem Under Investigation • Experimental Design • Field & Laboratory Analyses • Results – CTD Data – Laboratory Data • Implications • Recommendations
Cayuga Lake Phosphates & Suspended Sediments 2005 - 2007 Mean Phosphate Average Phosphate (SRP, ug/L, P) 12 10 2005 Surface 2006 Surface 8 2007 Surface 6 2005 Bottom 4 2006 Bottom 2007 Bottom 2 0 a e a a a o s u y k g e c c o g u l e u s e e i e n y a a t n K a a e w d o C e S n O H n a a n k a S C
The Concern • Upwelling of Bottom Water – Hypolimnion Phosporus – Upwelled to Surface – Fertilizes Algal Growth – Degrades Water Quality – Especially Southern End • Upwelling Mechanisms – Cornell’s Lake Source Cooling – Internal Seiche Activity – Waves & Surface Currents • Induce Localized Upwelling
Fluorescence 2007 CTD Profiles Subsurface Algae Turbidity Site D Surface & Nepheloid
Probable Sources of Sediment (and attached Phosphates?) to the Nepheloid Layer •Fluvial – Suspended Sediments & Phosphates from Runoff Events, esp. in Spring •Resuspension by Waves Spring Runoff Events – Suspended Sediments & Phosphates from Southern Shelf •Settling Dead Algae – Especially in Summer – Bacteria Release SRP Photos by Bill Hecht
Study Design: Fieldwork Eight Sites • Two Sites, A & C, just offshore of Taughannock and Salmon Creeks • Six sites along a mid-lake transect – Sites 1 & 2 Finger Lakes Survey – Sites B, D, E & G extend mid-lake southward from Site 2 • Sampling each site once every 2 weeks • May through October
Methods CTD Profile - SeaBird CTD SBE-25 SeaLogger Profiles of Conductivity, Temperature, pH, Dissolved Oxygen, Turbidity, and Fluorescence Water Samples Surface Water Mid Depth (40m above the lake floor) Bottom Water (within a few m of the lake floor) Onsite Analyses Vertical and Horizontal Plankton Tow Secchi Disk Depth Conductivity, Temperature & pH Dissolved Oxygen & Alkalinity Titrations Laboratory Analyses Total Phosphate (TP) Soluble Reactive Phosphate (SRP) Nitrate Chlorophyll-a Total Suspended Sediments (TSS) Major Ion Concentrations.
CTD Turbidity Runoff Event? No Rain Profiles Highest After Wind Events Episode Increases - Minimal Accumulation Site 1 Minimal Contribution from Algae May & Early June Profiles Wind & Runoff Events Deepest Sites Impact by Wind & Runoff? Sources
Phosphates: TP (uniform) and SRP (high in bottom) 2006 - 2008 Mean Total Phosphates 2005 - 2008 Mean Phosphate Average Phosphate (SRP, ug/L, P) 25 12 Phosphate (TP, ug/L, P) 2005 No Data 2005 Surface 10 20 2006 Surface 2006 Surface 8 2007 Surface 2007 Surface 15 2008 Surface 2008 Surface 6 2005 No Data 2005 Bottom 10 2006 Bottom 2006 Bottom 4 2007 Bottom 2007 Bottom 5 2 2008 Bottom 2008 Bottom 0 0 e a a a e a a a a o s o a o s o u u y k c g e y k g e c c c c c o g u g e u s l s o u e u s l s e e e i e a e i e n y i n y a i a t t a t t n K a a O n K a a O d e w e w d o S C e o S C e n O n O H n H n a a a a n n k k a a S S C C Total Phosphate - 2008 Dissolved Phosphate - 2008 Large Hypolimnetic SRP Reservoir 20 16 14 SRP (P, ug/L) 15 12 TP (P, ug/L) 10 10 8 6 5 4 2 0 0 1M 2M B/M D/S D/M D/B E/S E/M E/B G/S G/M G/B 1M 2M B/M D/S D/M D/B E/S E/M E/B G/S G/M G/B 1S 1B 2S 2B B/S B/B 1S 1B 2S 2B B/S B/B Sites Sites Recycling of Algal Matter?
Chlorophyll-a (high surface) & Total Suspended Sediments (high bottom) 2005 - 2008 Mean Chlorophyll-a 2005 - 2008 Mean Total Suspended Solids Average Chlorophyll-a (ug/L 5 4 Average TSS (mg/L) 2005 Surface 2005 Surface 4 2006 Surface 3 2006 Surface 2007 Surface 2007 Surface 3 2008 Surface 2008 Surface 2 2005 Bottom 2005 Bottom 2 2006 Bottom 2006 Bottom 2007 Bottom 1 2007 Bottom 1 2008 Bottom 2008 Bottom 0 0 e a a a a s o o a e a a a s o u o y k c g e c c y u k c g c e c o g u e u s l s e o g u l e u s s e i e e n y a i a t t e i e n y a i a n K a a O t t e w d n K e a w a O d o C e S e n O o S C n O H n H n a a a a n n k k a a S S C C Chlorophyll-a - 2008 Total Suspended Solids - 2008 7 8 Chlorophyll-a (ug/L) 7 6 6 5 TSS(mg/L) 5 4 4 3 3 2 2 1 1 0 0 D/S D/M D/B E/S E/M E/B G/S G/M G/B 1S 1M 1B 2S 2M 2B B/S B/M B/B 1S 1B 2S 2B B/S B/B D/S D/B E/S E/B G/S G/B Sites Site Recycling of Algal Matter?
2005 - 2008 Mean Secchi Disk Depth a Secchi Disk s u e g l i e a e o t y d a a a c o n g a c e o s e a e u k n c a Depths n n u n y s a w o a e e a i k t O O H C K S C S 0 Aveage Secchi Depth (m) 1 2 CTD 3 2005 4 2006 Fluorescence 5 2007 6 2008 7 Data 8 9 10 Secchi Disc Depth - 2008 Algal 1 2 B D E G 0 biomass 1 below 2 Depth (m) 3 epilimnion 4 5 6 North to South Decrease in Water Clarity
Phosphate vs. Suspended Solids Linked? SRP vs TSS TP vs TSS 25 16 14 20 12 SRP (ug/L) TP (ug/L) 10 15 8 10 6 4 5 2 0 0 0 2 4 6 8 10 0 2 4 6 8 10 R 2 = 0.01 R 2 = 0.05 TSS (mg/L) TSS (mg/L) Phosphate Recycled Algal Matter? New Phosphate << Recycled Phosphate
Implications • Suspended Sediments at Lake Floor are probably related to resuspension events by wind, runoff events, and less importantly settling algae. • Phosphates not linked to Suspended Sediments – Other Sources of Phosphate to Lake? – Missed Early Spring Runoff Contributions? – Primarily Recycled Phosphorus by Bacteria? – High Phosphate in Hypolimnion an Ongoing Problem • Suggests that the inhabitants of the area must reduce their phosphate input in the lake.
Recommendations • Must Decrease Long Term Phosphate Sources • Phosphate Sources from Other Work – Spring Runoff from Agricultural & Urban Areas (50%) – Wastewater Treatment Facility Inputs (~45%) – Lake Source Cooling (3%) – Septic Systems (??)
2008 Crew 2008 Crew Thanks - Questions?
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