Sources for Bottom Water Phosphates and Suspended Sediments in Southern Cayuga Lake, New York

Transcription

1 Sources for Bottom Water Phosphates and Suspended Sediments in Southern Cayuga Lake, New York Prabighya Basnet Hobart & William Smith Colleges Geneva, NY

2 Outline of Today s Presentation Introduce Problem Under Investigation Experimental Design Field & Laboratory Analyses Results CTD Data Laboratory Data Implications Recommendations

3 Cayuga Lake Phosphates & Suspended Sediments 5-7 Mean Phosphate Surface 6 Surface 7 Surface 5 Bottom 6 Bottom 7 Bottom Honeoye Canandaigua Keuka Seneca Cayuga Owasco Average Phosphate (SRP, ug/l, P) Skaneateles

4 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

5 7 CTD Profiles Site D Fluorescence Subsurface Algae Turbidity Surface & Nepheloid

6 Probable Sources of Sediment (and attached Phosphates?) to the Nepheloid Layer Fluvial Suspended Sediments & Phosphates from Runoff Events, esp. in Spring Resuspension by Waves Suspended Sediments & Phosphates from Southern Shelf Settling Dead Algae Especially in Summer Bacteria Release SRP Spring Runoff Events Photos by Bill Hecht

7 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 & Finger Lakes Survey Sites B, D, E & G extend mid-lake southward from Site Sampling each site once every weeks May through October

8 Methods CTD Profile - SeaBird CTD SBE-5 SeaLogger Profiles of Conductivity, Temperature, ph, Dissolved Oxygen, Turbidity, and Fluorescence Water Samples Surface Water Mid Depth (m 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.

9 Runoff Event? No Rain Highest After Wind Events CTD Turbidity Profiles Episode Increases - Minimal Accumulation Site 1 Minimal Contribution from Algae May & Early June Profiles Wind & Runoff Events Deepest Sites Impact by Wind & Runoff? Sources

10 Phosphates: TP (uniform) and SRP (high in bottom) Mean Phosphate Honeoye Canandaigua Keuka Seneca Cayuga Owasco Skaneateles Otisco Total Phosphate - 8 1S 1M 1B S M B B/S B/M B/B D/S D/M D/B E/S E/M E/B G/S G/M G/B Sites Dissolved Phosphate - 8 TP (P, ug/l) 1S 1M 1B S M B B/S B/M B/B D/S D/M D/B E/S E/M E/B G/S G/M G/B SRP (P, ug/l) Average Phosphate (SRP, ug/l, P) Mean Total Phosphates 5 No Data 6 Surface 7 Surface 8 Surface 5 No Data 6 Bottom 7 Bottom 8 Bottom 5 Surface 6 Surface 7 Surface 8 Surface 5 Bottom 6 Bottom 7 Bottom 8 Bottom Honeoye Canandaigua Keuka Seneca Cayuga Owasco Skaneateles Otisco Large Hypolimnetic SRP Reservoir Sites Recycling of Algal Matter? Phosphate (TP, ug/l, P)

11 Chlorophyll-a (high surface) & Total Suspended Sediments (high bottom) 5-8 Mean Chlorophyll-a 5-8 Mean Total Suspended Solids Surface 6 Surface 7 Surface 8 Surface 5 Bottom 6 Bottom 7 Bottom 8 Bottom Surface 6 Surface 7 Surface 8 Surface 5 Bottom 6 Bottom 7 Bottom 8 Bottom Average Chlorophyll-a (ug/l Average TSS (mg/l) Honeoye Canandaigua Keuka Seneca Cayuga Owasco Skaneateles Otisco Honeoye Canandaigua Keuka Seneca Cayuga Owasco Skaneateles Otisco Chlorophyll-a - 8 Total Suspended Solids S 1M 1B S M B B/S B/M B/B D/S D/M D/B E/S E/M E/B G/S G/M G/B Sites Chlorophyll-a (ug/l) G/S 1S 1B S B B/S B/B D/S D/B E/S E/B TSS(mg/L) G/B Site Recycling of Algal Matter?

12 5-8 Mean Secchi Disk Depth Aveage Secchi Depth (m) Honeoye Keuka Canandaigua Seneca Cayuga Owasco Otisco Skaneateles Secchi Disk Depths CTD Fluorescence Data Depth (m) 1 3 Secchi Disc Depth B D E G Algal biomass below epilimnion 5 6 North to South Decrease in Water Clarity

13 Phosphate vs. Suspended Solids Linked? TP (ug/l) TP vs TSS R =.5 TSS (mg/l) SRP (ug/l) SRP vs TSS R =.1 TSS (mg/l) Phosphate Recycled Algal Matter? New Phosphate << Recycled Phosphate

14 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.

15 Recommendations Must Decrease Long Term Phosphate Sources Phosphate Sources from Other Work Spring Runoff from Agricultural & Urban Areas (5%) Wastewater Treatment Facility Inputs (~5%) Lake Source Cooling (3%) Septic Systems (??)

16 Thanks - Questions? 8 Crew