Physical, Chemical, and Biological Responses to Inflow Events in the

San Antonio Bay System

Stephen E. Davis, III

co-PIs: Dan Roelke (TAMU) and Doug Slack (TAMU)

Graduate students: Bryan Allison, Tim Assal, Rachel Butzler, George Gable, David Hoeinghaus, Hsiu-Ping Li, Carrie Miller, Jose-Vicente Montoya

Why study inflows to estuaries?

George Ward (UT)

Why study inflows to estuaries?

INFLOWS

inundation

salinity

FLORA

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Conceptual framework for estuarine research…and TexEMP modelling (TWDB and TPWD)

How much inflow does a given estuary need? When? For how long? How often?

materials

Why study inflows to estuaries?

From 2002 State Water Plan

Why study multiple scales in estuaries?

Spatial Scales of Consideration

• Sites of interaction between Watershed-level processes and oceanographic processes

– Regional climate

– Tides

– Watershed development

• Estuarine zonation

– Tide/elevation

• sub-tidal to high inter-tidal

– Freshwater inflow/flushing

• oliogohaline to polyhaline

http://tx.usgs.gov/basins.html

Why study multiple scales in estuaries?

Temporal Scales of Consideration

• Inter-annual variability

– ENSO forcing

– Disturbance regime

– Watershed development

• Intra-annual variability

– Hydrodynamics

• Anthropogenic effects

• Diurnal and spring/neap

• Wind forcing, storm effects

– Freshwater inflow/flushing

• Seasonal climate

How to characterize?

• Number of pulses

• Magnitude of pulses

• Duration of pulses

• Period between pulses

Marsh Studies1. Water quality2. Hydrodynamics3. Vegetation & soils 4. Marsh inundation5. Food Web patterns

Guadalupe Estuary

Lower Guadalupe River1. Discharge and

stage (USGS gauge)

2. Nutrient and TSS Loadings

Open Water/Bays1. Dataflow mapping2. Water quality/

nutrients3. Lower food web

dynamics

Seadrift gauge(TCOON)

GBRA #1 gauge(TCOON)

Whooping cranes at ANWR

Photo by Kristin LaFever

ANWR Creek and Marsh sampling sites

Spatio-temporal varaibility in creek salinity

OCT/NOV 2003 JUL 2004FEB 2004

salin

ity (

‰)

JUN/JUL 2003

Boat Ramp

Pump Canal

Sundown Bay2-week salinity snapshots at three sites

ANWR tidal creek salinity June 2003–May 2005

“average” year

wet year

Boat Ramp

Pump Canal

Sundown Bay

Seasonal Salinity at Pump Canal June 2003–May 2005

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Guadalupe River discharge @ Victoria (cfs)

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Salinity

Discharge Boat Ramp salinity

Do Guadalupe River inflows affect ANWR creek salinity?

Do Guadalupe River inflows affect ANWR creek salinity?

YES, but other factors are also at work.

including: upland runoff, direct precipitation, groundwater exchange, wind forcing, tides, barge traffic, etc.

Dataflow in Action

Measures: LAT/LONG, Temperature, Conductivity/Salinity, Transmittance, Chlorophyll a, CDOM, Depth, and PAR

At approximately 8 second intervals from a vessel running at 20 kts.

pumpbox

ram

de-bubbler

GPS/depth

datalogger

temp/cond

Tracking responses to Guadalupe River inflow events using Dataflow

Quantifying hydrologic connectivity across the marsh

tidal creek

ponds

Inferring connectivity using paired water level recorders

Predicting creek hydrodynamics AND marsh inundation

Understanding anthropogenic impacts

Seasonal dynamics of wolfberryN

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93% 98% Whooping cranes

2003 2004

BR Marsh Vegetation

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Borrichia

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WolfberryWhite Aster

Carax

Salicornia

C3 succulents

Spartina

Distictlis

C4 grasses

BR Channel

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Hardhead

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BR Connected Pond

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BR Isolated Pond

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Blue Crab

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Ladyfish

Sailfin Molly

Plankton incubation chamber array

flow-through phytoplankton reaction chambers

peristaltic pump

media reservoir

temperature control bath

light box with 3 chambers

Zooplankton (bio-volume) and Phytoplankton (fluorescence) response to continuous vs. pulsed mode of

delivery under different hydrologic flushing rates

Fluorescence (Integrated)

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Flushing (d-1)

Integrated Fluorescence

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Zooplankton (Integrated)

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Flushing (d-1)

Integrated Zooplankton

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Mean annual flushing

What have we learned thus far?

1. Large pulses affect water levels/connectivity, BUT other

factors are more important during median flows.• Connectivity affects food web patterns

2. River inflows drive bay-wide water quality, BUT other

factors may be equally important in ANWR tidal creeks.• Entire lagoonal estuary can be fresh

3. Marsh vegetation is sensitive to intra-annual variations

in inundation and salinity.• Greenhouse studies

4. Water column mostly net autotrophic

5. Phytoplankton and zooplankton show positive response

to pulsed inflows.

Funding for TX estuarine inflow research

On-line Access To Data (http://wfsc.tamu.edu/davislab)

On-line Access To Data (http://wfsc.tamu.edu/davislab)

On-line Access To Data (http://wfsc.tamu.edu/davislab)

On-line Access To Data (http://wfsc.tamu.edu/davislab)