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How Will Climate Change Affect Water
Quality and Biogeochemical Processes in
the Delaware Estuary?
David Velinsky
Patrick Center for Environmental Research
The Academy of Natural Sciences
May 6, 2008
Climate Change in the Delaware Estuary:
Impacts and Adaptation
Estuarine Processes and Climate Change
What are the main driving forces?
Temperature
Sea Level
Courtesy of Hans Paerl and Ashley Smyth
Climate Change Affects Physical Factors that
Impact Water Quality:
• Sea Level Rise
- Salt intrusion further up bay
- Increase in vertical stratification
- Loss of tidal marshes
• Changes in Precipitation and Freshwater Inflow
- Nutrient and sediment loading (amount, timing and variability)
- Water residence time
• Water and Air Temperature Changes
- Timing of phytoplankton blooms
- Algal community alterations (harmful algal blooms?)
- Contaminant exchanges
- Biogeochemical reaction kinetics
Salt Intrusion
Salinity, at any given point, is a balance between freshwater inflow, tidal/wind
mixing, shape and bathymetry, and sea level.
- With a sea level rise of 0.7 to 2 m, the salt line could move up-bay by 3 to
30 mile, which would impact drinking water intakes, industrial intakes,
groundwater recharge and mixing dynamics in the estuary.
Taken from Hull and Titus, 1986
However….
7000
• Delaware River discharge is highly 250 cm rise
6000
regulated via various reservoirs;
Chloride (mg/L)
70 m rise
5000 Base Run
management in the future will be a key
4000
issue in salt movement up bay,
3000
2000
• deepening of river bottom would allow 1000
salt water to move up bay, and 0
60 70 80 90 100 110 120 130
• some scenarios call for less rainfall in NE US. River Mile (going upstream)
A “Prefect Storm” would be a rise in sea level, a deeper channel, drought conditions,
and lower storage in the reservoirs >> salt front would move farther upstream.
Loading of Chemicals: Nutrient and Contaminants
Three of the seven largest floods on
Average Annual Discharge (CMS)
record have occurred since 2004.
- Precipitation Changes (amount, intensity, and
variability)
- Land Use Changes are a factor
J. Sharp, UDEL (2007; MAC)
There would be impacts to non-point source loads of nutrients, sediments
and contaminants to the estuary.
Biogeochemical Cycling
Delaware Estuary, while receiving large loads of N and P, is not substantially
impacted by eutrophication (e.g., algal blooms, low dissolved oxygen).
Will climate change impacts make a difference?
O x y g e n (µ g -a t O /L )
8.0
500
1967 1997
6.5
400
300
4.5
DO (mg/L)
3.0
200
1.5
100
0.00
40 60 80 100 120 140 160 180 200 220
Distance (km)
Courtesy of J. Sharp, UDEL
Dissolved oxygen concentration in surface waters on transect
down Delaware Estuary in summer (1967 and 1997). Major
upgrade of sewage treatment plants decreased BOD.
Points of Interest:
• Loadings
• Primary Production
• Remineralization
• Oxygen Consumption
• Stratification
http://www.chemgapedia.de/vsengine/media/vsc/en/ch/16/uc/images/estuarinenit.jpg
Magnitude and Timing
Contaminant Inputs and Processes in Coastal Waters
Rain Deposition to Urban
Water and Land Runoff
Contaminants: Potential Impacts
Relative to Climate Change
• Freshwater Inflows and Timing:
- Increase or decrease of contaminants loads into the bay
• Air and Water Temperature, Salinity
- Increase in the exchange between water and air
- Changes in the partitioning between dissolved-colloidal-particulate forms
• Algal Productivity:
- Changes in trophic transfer and bioaccumulation
Chemical Inputs and Processes in Coastal Waters
Atmospheric
Organic compounds, like Air-Water Exchange Deposition
PCBs, are volatile and can Tributary
Inputs
move between the air and Air-Water
Air
water. The more chlorine Exchange
groups the higher the Water
Advection
Dispersion
molecular weight, and
Dissolved Particulate
lower volatility. PCBs PCBs
Porewater Settling-
Transport Resuspension
Research by Lisa
Rodenburg (Rutgers Univ.) Sediment
has shown that exchange
is directed from the water
to the air in Delaware
estuary.
(Env. Sci. Tech, 2007)
Movement of Volatile Organic Compounds
(PCBs, PBDEs etc) Between Water and Air
Will the actual or predicted change in temperature and salinity make a difference?
• Various CC Models predict 1 to 5oC increase
• PCB 52 (2,2',5,5'- tetrachlorobiphenyl) %Increase in PCB52 in air
25
3’ 2’ 3 2 (Cl)x
4’ 4
Percent Increase in 20
5’ 6’ 5 6 PCB52 in Air
• Starting temperature at 25oC 15
• Henry’s Law transfer
10
5
0
0 1 2 3 4 5 6
o
Degrees above 25 C
The effect of increasing water temperatures on PCB 52
could increase the concentration in air by 20%.
Ecosystem “Services” of Tidal Marshes
• Primary nursery area for offshore winter-spawned fishes
• Finfish and shellfish habitat
• Recreation
• Aesthetic (property values - $$$$)
• Nutrient processing
Estuarine / Marsh
Tidal Freshwater Coastal Ecosystem
Salt Marsh
Marsh
River
Estuary
Ocean
Courtesy of N. Weston (Villanova Univ.)
Marshes Must Accrete to in Tidal Marshes
Carbon and Mass Balance Keep Pace With
Watershed Rising Sea-Levels
Inputs (N,P & Seds) CO2
CO2 & CH4
Primary Production Export
Marsh Accretion MSL
Burial
Sediment Organic Microbial Respiration
Matter (CNP) CO2 & CH4
> Marsh Accretion: Plant growth/dieback, watershed and tidal water sediment inputs
Courtesy of N. Weston (Villanova Univ.)
Estuarine / Marsh Coastal Ecosystem
Changing
Precipitation
River Salinity Intrusion
Rising
Sea Level
Ocean
Courtesy of N. Weston (Villanova Univ.)
Freshwater Marsh Undergoing Salinity Intrusion:
Potential Impacts C and P Cycles
Plant Response
CO2 CO2 & CH4
Primary Production
MSL
Loss of Marsh?
Microbial Respiration
Sediment Organic PO43-
Matter Methanogens CO2 & CH4
Retention of P Sulfate Reducers
P Desorption Microbial Response
Courtesy of N. Weston (Villanova Univ.)
Future Concerns
Some form of Climate Change will occur in the next 20 to 50 years
Impacts:
- Salinity Intrusion: reduced freshwater availability
- Nutrient and Contaminant Loadings: changes due to precipitation
- Water Quality: changes due to loadings, water stratification and
impacts to dissolved oxygen
- Tidal Marshes: loss of marshes will hurt filtering capacity for
nutrients
Future Directions
• Monitor key ecosystem variables (e.g., DEWOOS)
• Improve communication and management of water flows
among user groups
• Reduce nutrient, contaminant and sediment loads to estuary
• Land management to provide for marsh migration (natural
adaptation)
• Plan for an adaptive management strategy
The End
Sharp (2007; MAC)
R2 = 0.0552; slope = 0.12 cm/yr; P = 0.0158
From: Interlandi and Crockett, 2003 (NCDC; NOAA)
http://climatechange.rutgers.edu/images/delaware_river_floods.jpg
Consequences of Coastal Shoreline Development
and Marsh Removal
Delaware
Estuary
• Increased CO2 will lower pH in FW and increase chemical weathering. It
will also decrease pH in seawater, but maybe less, but effects CaCO3
saturation (There is a big literature on ocean acidification; I'm
working on a project with Whitman Miller on this here).
• CO2 increase may impact phytoplankton growth, both from lower pH and
from more available CO2. CO2 tends to act as a limiting nutrient for
plants. Higher CO2 certainly affects marsh grasses (and C4 plants
different than C3, look up anything by Bert Drake.
• In terms of weather, it means different things in different places
(changes in rain and average temp both plus and minus).
• Sea level rise will push salt water over freshwater marshes, and drown
shallow land. Things that happen now, but they may speed up. Change in
position of sed max in estuaries, and sedimentation pattern, estuarine
circulation
Climate Change affects Physical Factors that Impact
Water Quality:
• Sea Level Rise
- Salt intrusion further up bay (also – water management & dredging)
- Increase in vertical stratification
- Loss of tidal marsh filtering capacity
• Changes in Precipitation Pattern and Freshwater Inflow
- Water residence time
- Nutrient and sediment loading
• Water and Air Temperature Changes
-Timing of phytoplankton blooms
- Algal species alterations (- harmful algal blooms?)
- Alterations of contaminant exchanges
Impacts to Water Quality and Biogeochemical Processes :
Contaminants
• Changes in freshwater inflow
-
- Vertical stratification and mixing patterns
- Marsh-Bay exchange: salt and tidal freshwater systems
• Changes in Precipitation Pattern and Freshwater Inflow
- Water residence time
- Nutrient and sediment delivery
• Water and Air Temperature Changes
-Timing of phytoplankton blooms
- Algal species alterations
How Does Salinity Intrusion Affect Tidal Freshwater Marshes?
Watershed
Inputs
CO2 CO2 & CH4
Export
Primary Production
MSL
Sediment Microbial Respiration
Organic CO2 & CH4
Matter
