Biological Effects of Selected Structures and Practices in Galveston Bay System

1
Biological Effects of Selected Structures and
Practices in Galveston Bay System

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

2
Project Flowchart
Delta Marshes Oyster Reefs
TWDB
TPWD
Circulation Salinity
Habitat Species
Structures
Change in PAZ ?
Practices
Blue Crab Gulf Menhaden
3
(No Transcript)
4
And We know that
Not all man-made changes are
beneficial to the system
5
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

6
(No Transcript)
7
Trinity Delta Marshes

• In upper bay the oligohaline zone
• Cover 54 Km2
• Mixed emergent vegetation - dominated by
• -Scirpus spp. (bulrush)
• -Others (arrowheads, alligator weeds)
• Submerged vegetation present - dominated by
• -Ruppia maritima
• -Najas spp.
• -Vallisneria americana

8
Trinity Delta Marshes (contd)

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

9
Trinity Delta Marshes (contd)

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

10
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

11
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

12
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

13
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 (wet vs. dry year, and among the
  different
• structures/practices)
• - area extent or
• - location

14
Analytical Procedure (contd)

• 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)

15
(No Transcript)
16
Oyster Reefs PAZ 10 20 ppt
17
Blue Crab PAZ 5 15 ppt
18
Gulf Menhaden PAZ 10 15 ppt
19
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
no PAZ averages 50 - Dry TCD
generates higher PAZ - Changes in current
vector ?
20
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)
21
Mesohaline (10 15 ppt)
Dry Year
HSC TCD
2.7 14.3
Wet Year
26.0 30.8
22
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
23
Relative Impacts of Structures/Practices on
Selected Habitats and Species
Delta Marsh
Oyster Reef
Dry
Wet
Dry
Wet
HSC HSC
TCD FWD
FWD TCD
PPO PPO
TCD PPO
FWD TCD
PPO FWD
HSC HSC
Decreasing Impact on PAZ
Blue Crab
Gulf Menhaden
TCD TCD
FWD PPO
PPO FWD
HSC HSC
TCD TCD
FWD PPO
HSC FWD
PPO HSC
24
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

25
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