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

Project Flowchart Circulation & Salinity Habitat & Species Delta Marshes Oyster Reefs Blue Crab Gulf 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 Cases (dry and wet year conditions) EC – Existing Conditions EC – Existing Conditions PPO – Power Plant Thermal Release PPO – Power Plant Thermal Release TCD – Texas City Dyke TCD – Texas City Dyke HSC – Houston Ship Channel HSC – Houston Ship Channel FID – Freshwater Inflow Diversion FID – Freshwater Inflow Diversion NC – Naturalized Conditions NC – Naturalized Conditions

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

Trinity Delta Marshes (cont’d) Finfish in delta marshes Finfish in delta marshes - Sheepshead minnow - Gulf killifish - Bay anchovy - Striped mullet - Atlantic croaker

Trinity Delta Marshes (cont’d) Shellfish in delta marshes Shellfish in delta marshes - Grass shrimp - Blue crab - Pink shrimp - Brown shrimp - White shrimp

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

Blue Crab ( Callinectes spidus ) Ecologically and commercially important Ecologically and commercially important Estuarine-dependent Estuarine-dependent R-selected strategists R-selected strategists Secondary consumer Secondary consumer Most abundant in vegetated habitats in Most abundant in vegetated habitats in mesohaline zone mesohaline zone Densities in open waters peak in May-June Densities in open waters peak in May-June

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

Analytical Procedure Locate the PAZ Locate the PAZ -explore the historical database trawl to 2000 trawl to 2000 oyster dredge to 2003 oyster dredge to find out the PAZ - where the peak abundance occurs and what the salinities are what the salinities are -assumption: increase in PAZ value would be beneficial Compare PAZ (wet vs. dry year, and among the different Compare PAZ (wet vs. dry year, and among the different structures/practices) structures/practices) - area extent or - area extent or - location - location

Analytical Procedure (cont’d) How to find the PAZ How 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 salinity - Comparisons of mean CPUE among salinity zones (ANOVA) zones (ANOVA)

Oyster Reefs PAZ: 10 – 20 ppt

Blue Crab PAZ: 5 – 15 ppt

Gulf Menhaden PAZ: 10 – 15 ppt

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 ?

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 Wet Year

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 FWDPPO PPOFWD HSCHSCTCDTCDFWDPPO HSCFWD PPOHSC HSCHSCTCDFWD FWDTCD PPOPPOTCDPPOFWDTCD PPOFWD HSCHSC DryWetDryWet Delta MarshOyster Reef Blue CrabGulf Menhaden Relative Impacts of Structures/Practices on Selected Habitats and Species Decreasing Impact on PAZ

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