Biological Effects of Selected Structures and Practices in Galveston Bay System David Buzan, Liz Singhurst, Grace Chen and Wen Lee.

Biological Effects of Selected Biological Effects of Selected Structures and Practices in Structures and Practices in

Galveston Bay SystemGalveston Bay System

David Buzan, Liz Singhurst, Grace David Buzan, Liz Singhurst, Grace Chen and Wen LeeChen and Wen Lee

Project FlowchartProject Flowchart

Circulation&

Salinity

Habitat&

Species

Delta MarshesOyster Reefs

Blue CrabGulf Menhaden

Change in PAZ ?Structures

Practices

TWDB

TPWD

And We know that:

Not all man-made changes are beneficial to the system

The Six Study CasesThe Six Study Cases(dry and wet year conditions)(dry and wet year conditions)

• EC – Existing ConditionsEC – Existing Conditions

• PPO – Power Plant Thermal ReleasePPO – Power Plant Thermal Release

• TCD – Texas City DykeTCD – Texas City Dyke

• HSC – Houston Ship ChannelHSC – Houston Ship Channel

• FID – Freshwater Inflow DiversionFID – Freshwater Inflow Diversion

• NC – Naturalized ConditionsNC – Naturalized Conditions

Trinity Delta Trinity Delta MarshesMarshes

• In upper bay – the oligohaline zoneIn upper bay – the oligohaline zone• Cover ~ 54 KmCover ~ 54 Km22

• Mixed emergent vegetation - dominated by Mixed emergent vegetation - dominated by --ScirpusScirpus spp. (bulrush) spp. (bulrush)

-Others (arrowheads, alligator weeds…)-Others (arrowheads, alligator weeds…)• Submerged vegetation present - dominated bySubmerged vegetation present - dominated by

-Ruppia maritima-Ruppia maritima--NajasNajas spp. spp. --VallisneriaVallisneria americanaamericana

Trinity Delta Marshes Trinity Delta Marshes (cont’d)(cont’d)• Finfish in delta marshesFinfish in delta marshes

- Sheepshead minnow- Sheepshead minnow

- Gulf killifish- Gulf killifish

- Bay anchovy- Bay anchovy

- Striped mullet- Striped mullet

- Atlantic croaker- Atlantic croaker

Trinity Delta Marshes Trinity Delta Marshes (cont’d)(cont’d)

• Shellfish in delta Shellfish in delta marshesmarshes

- Grass shrimp- Grass shrimp

- Blue crab- Blue crab

- Pink shrimp- Pink shrimp

- Brown shrimp- Brown shrimp

- White shrimp- White shrimp

Mid-Bay Oyster ReefsMid-Bay Oyster Reefs

• 14000 acres in the bay14000 acres in the bay

• Distribution and importanceDistribution and importance

• Salinity ( 12 -19 ppt)Salinity ( 12 -19 ppt)

• Temperature (12 to 30 C)Temperature (12 to 30 C)

• Dominated byDominated by

-American oyster-American oyster

-Bay anchovy-Bay anchovy

-Mud crabs-Mud crabs

-Amphipods-Amphipods

-Capitellids-Capitellids

Blue Crab (Blue Crab (CallinectesCallinectes spidusspidus))• Ecologically and commercially importantEcologically and commercially important

• Estuarine-dependentEstuarine-dependent

• R-selected strategistsR-selected strategists

• Secondary consumerSecondary consumer

• Most abundant in vegetated habitats inMost abundant in vegetated habitats in

mesohaline zonemesohaline zone

• Densities in open waters peak in May-Densities in open waters peak in May-JuneJune

Gulf Menhaden Gulf Menhaden ((BrevoortiaBrevoortia PatronusPatronus))

• Life history/strategy similar to blue crabLife history/strategy similar to blue crab• Primary consumerPrimary consumer• Abundant in open waters with salinitiesAbundant in open waters with salinities of 10 to 15 pptof 10 to 15 ppt• Densities low in summer and high inDensities low in summer and high in early winterearly winter

Analytical ProcedureAnalytical Procedure • Locate the PAZLocate the PAZ

--exploreexplore the historical database the historical database trawl - 1982 to 2000trawl - 1982 to 2000

oyster dredge - 1988 to 2003oyster dredge - 1988 to 2003--find outfind out the PAZ - where the peak abundance occurs and the PAZ - where the peak abundance occurs and what the salinities arewhat the salinities are--assumptionassumption: increase in PAZ value would be beneficial: increase in PAZ value would be beneficial

• Compare PAZCompare PAZ (wet vs. dry year, and among the different (wet vs. dry year, and among the different structures/practices)structures/practices)

- area extent or- area extent or - location- location

Analytical Procedure (cont’d)Analytical Procedure (cont’d)

• How to find the PAZHow to find the PAZ

- CF trawl data- CF trawl data

- Seasons to be included- Seasons to be included

- Spatial distribution in relation to - Spatial distribution in relation to

salinity gradient in the bay (GIS)salinity gradient in the bay (GIS)

- Comparisons of mean CPUE among - Comparisons of mean CPUE among salinity salinity

zones (ANOVA)zones (ANOVA)

Month

Mea

n C

PU

E (

no.

/ha)

0

500

1000

1500

2000

2500

3000

3500

Sabine GalvestonAransasU. LagunaL. Laguna

White Shrimp: Relative abundace for selected seasons in Sabine Lake, Galveston, Aransas and Laguna Madre systems

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Oyster Reefs PAZ: 10 – 20 ppt

Blue Crab PAZ: 5 – 15 ppt

Gulf Menhaden PAZ: 10 – 15 ppt

% B

ay A

rea

0.0

0.5

1.0

1.5

2.0

EC

PPO

TCD

HSC

FWD

NC

Wet Year Dry Year

(0 - 5 ppt)A - Trinity River Delta

% B

ay A

rea

0

10

20

30

40

50

60

70

EC

PPO

TCD

HSC

FWD

NC

B - Middle Bay - Oyster Reef(10 - 20 ppt)

Wet Year Dry Year

Figure 4. Intertidal marsh and oyster reef - changes in PAZ related to climatic conditions and structures/practices in Glveston Bay.

Delta Marshes

- Assume PAZ of 0 to 5 ppt

- Climatic impact – yes

wet year = 23 Km2

dry year = 0.7 km2

- Wet - HSC has the most impact

- Marsh production

Mid-Bay Oyster Reefs

- Climatic impact – noPAZ averages 50%

- Dry – TCD generates higher PAZ

- Changes in current vector ?

1. Mid-bay Isohaline From 20 to 10 ppt

From Dry to Wet

2. Upper Bay Less saline

(15-20 to 5-10 ppt)

(1996 to 1992)

Mesohaline (10 – 15 ppt)

HSC TCD

Dry Year

2.7 14.3

Wet Year

26.0 30.8

Wet Year Dry Year

% B

ay A

rea

0

20

40

60

80

EC

PPO

TCD

HFC

FWD

NC

Wet Year Dry Year

A - Blue Crab(5 - 15 ppt)

% B

ay A

rea

0

5

10

15

20

25

30

35

EC

PPO

TCD

HSC

FWD

NC

B - Gulf Menhaden(10 - 15 ppt)

Figure 7. Blue crab and Gulf menhaden - changes in PAZ related to climatic conditions and structures/practices in Galveston Bay.

Blue Crab (5-15 ppt) - Climate – yes

dry year = PAZ of 2 %

wet year = PAZ of 67 %

- Wet year

TCD seems to impact more vs. others

Gulf Menhaden (10-15 ppt)

- Climate – yes

dry year = PAZ of 6 %

wet year = PAZ of 29 %

- Dry year

TCD again shows more impact

TCDTCD TCDTCD

FWDFWD PPOPPO

PPOPPO FWDFWD

HSCHSC HSCHSC

TCDTCD TCDTCD

FWDFWD PPOPPO

HSCHSC FWDFWD

PPOPPO HSCHSC

HSCHSC HSCHSC

TCDTCD FWDFWD

FWDFWD TCDTCD

PPOPPO PPOPPO

TCDTCD PPOPPO

FWDFWD TCDTCD

PPOPPO FWDFWD

HSCHSC HSCHSC

Dry Wet Dry Wet

Delta Marsh

Oyster Reef

Blue Crab Gulf Menhaden

Relative Impacts of Structures/Practices on Selected Habitats and Species

Decr

easi

ng Im

pact

on P

AZ

SummarySummary• Climate has the most impacts on salinityClimate has the most impacts on salinity distribution in the baydistribution in the bay

• Biological effects of structures/practices Biological effects of structures/practices varyvary

depending on species’ PAZ depending on species’ PAZ

- - If PAZ in upper Bay – HSCIf PAZ in upper Bay – HSC - If PAZ in middle Bay – TCD - If PAZ in middle Bay – TCD - If PAZ in West Bay – TCD- If PAZ in West Bay – TCD

***Man-made changes are not all Bad***

- if we know what change can do

and

-if we know how we can manage it

or

-If we know how to accommodate to it