Biological Effects of Selected Structures and Practices in Galveston Bay System

David Buzan, Liz Singhurst, Grace Chen and Wen Lee

Project Flowchart

Structures Practices TWDB Circulation & Salinity TPWD Habitat & Species Delta Marshes Oyster Reefs Change in PAZ ?

Blue Crab Gulf Menhaden

And We know that: Not all man-made changes are beneficial to the system

The Six Study Cases

(dry and wet year conditions) • • • • • • EC – Existing Conditions PPO – Power Plant Thermal Release TCD – Texas City Dyke HSC – Houston Ship Channel FID – Freshwater Inflow Diversion NC – Naturalized Conditions

Trinity Delta Marshes

• • • • In upper bay – the oligohaline zone Cover ~ 54 Km 2 Mixed emergent vegetation - dominated by -Scirpus spp. (bulrush) -Others (arrowheads, alligator weeds…) Submerged vegetation present - dominated by -Ruppia maritima -Najas spp. -Vallisneria americana

Trinity Delta Marshes (cont’d)

• Finfish in delta marshes - Sheepshead minnow - Gulf killifish - Bay anchovy - Striped mullet - Atlantic croaker

Trinity Delta Marshes (cont’d)

• Shellfish in delta marshes - Grass shrimp - Blue crab - Pink shrimp - Brown shrimp - White shrimp

Mid-Bay Oyster Reefs

• • • • • 14000 acres in the bay Distribution and importance Salinity ( 12 -19 ppt) Temperature (12 to 30 C) Dominated by -American oyster -Bay anchovy -Mud crabs -Amphipods -Capitellids

Blue Crab (

Callinectes spidus

)

• • • • • • Ecologically and commercially important Estuarine-dependent R-selected strategists Secondary consumer Most abundant in vegetated habitats in mesohaline zone Densities in open waters peak in May-June

Gulf Menhaden

(Brevoortia Patronus) • • • • Life history/strategy similar to blue crab Primary consumer Abundant in open waters with salinities of 10 to 15 ppt Densities low in summer and high in early winter

Analytical Procedure

•

Locate the PAZ

-explore the historical database trawl - 1982 to 2000 oyster dredge - 1988 to 2003 -find out the PAZ - where the peak abundance occurs and what the salinities are -assumption: increase in PAZ value would be beneficial •

Compare PAZ

- area extent or - location (wet vs. dry year, and among the different structures/practices)

Analytical Procedure (cont’d)

• How to find the PAZ - CF trawl data - Seasons to be included - Spatial distribution in relation to salinity gradient in the bay (GIS) - Comparisons of mean CPUE among salinity zones (ANOVA)

White Shrimp: Relative abundace for selected seasons in Sabine Lake, Galveston, Aransas and Laguna Madre systems 3500 3000 2500 Sabine Galveston Aransas U. Laguna L. Laguna 2000 1500 1000 500 0

Jan Feb Mar Apr May Jun Jul

Month

Aug Sep Oct Nov Dec

Oyster Reefs PAZ: 10 – 20 ppt

Blue Crab PAZ: 5 – 15 ppt

Gulf Menhaden PAZ: 10 – 15 ppt

1.0

0.5

2.0

1.5

A - Trinity River Delta (0 - 5 ppt) EC PPO TCD HSC FWD NC 40 30 20 10 0.0

Wet Year 70 60 B - Middle Bay - Oyster Reef (10 - 20 ppt) 50 0 Wet Year Dry Year EC PPO TCD HSC FWD NC 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 Km 2

dry year

= 0.7 km 2 - Wet - HSC has the most impact - Marsh production

Mid-Bay Oyster Reefs

- Climatic impact – no PAZ averages 50% - Dry – TCD generates higher PAZ - Changes in current vector ?

From Dry to Wet (1996 to 1992) 1. Mid-bay Isohaline From 20 to 10 ppt 2. Upper Bay Less saline (15-20 to 5-10 ppt)

Mesohaline (10 – 15 ppt) Dry Year HSC TCD 2.7 14.3

Wet Year 26.0 30.8

40 20 80 A - Blue Crab (5 - 15 ppt) 60 EC PPO TCD HFC FWD NC 0 Wet Year Dry Year 35 30 B - Gulf Menhaden (10 - 15 ppt) 25 20 15 10 5 0 Wet Year EC PPO TCD HSC FWD NC Dry Year 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

Relative Impacts of Structures/Practices on Selected Habitats and Species Dry Delta Marsh Wet HSC TCD FWD PPO HSC FWD TCD PPO Blue Crab TCD FWD PPO HSC TCD PPO FWD HSC Oyster Reef Dry Wet TCD FWD PPO HSC PPO TCD FWD HSC Gulf Menhaden TCD FWD HSC PPO TCD PPO FWD HSC

Summary

• Climate has the most impacts on salinity distribution in the bay • Biological effects of structures/practices vary depending on species’ PAZ If PAZ in upper Bay – HSC - If PAZ in middle 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