Water quality and its effects on seagrass distribution
Linda Fitzhugh
Many thanks to:
Dr. Jon Hemming, RMA, BEST/FSABay
Water Quality Monitoring Stations
Map courtesy of the US Fish and Wildlife Service
Views of St. Andrew and West Bay
Water Quality Comparisons
West Bay Bowl
West Bay Arm
St. Andrew Bay
Map courtesy of the National Oceanic and Atmospheric Administration
Seagrass depth distribution and light attenuation
Mean Maximum SAV
Depth (m)
2.5
2.0
1.5
1.0
0.5
0.0
WBBOWL
WBARM
SAB
Mean Light Attenuation
(m-1)
2.5
2.0
1.5
1.0
0.5
0.0
WBBOWL
WBARM
SAB
Mean 13C (%o)
WBBOWL
0.0
-4.0
-8.0
-12.0
-16.0
-20.0
WBARM
SAB
Seagrass width
8.0
Thalassia width (mm)
6.0
4.0
2.0
0.0
WBBOWL
WBARM
SAB
~26% of surface light is needed for seagrass growth
Site
W2
W3
W4
W6
W7
W8
S7
S8
Max Depth (m)
0.99
0.75
0.83
1.25
1.22
1.3
1.96
1.83
k (m‐1)
1.42
1.81
1.59
1.13
1.06
1.04
0.67
0.72
%SI
25
26
27
24
27
26
27
27
Why is water quality so poor in West Bay?
• Chlorophyll a values
• Epiphyte growth
• 15N in epiphytes versus seagrasses Results
Mean Surface Turbidity
(NTU)
10.0
7.5
5.0
2.5
0.0
WBBOWL
WBARM
SAB
Area Name
Mean Chl A (ug/l)
8
6
4
2
0
WBBOWL
WBARM
SAB
Results
Epiphyte Growth (mg/d)
12.0
8.0
4.0
0.0
WBBOWL
WBARM
Vegetation Type
WBBOWL (15N)
WBARM (15N)
epiphyte
seagrass
7.6
3.5
5
2.6
Results
Water Quality Models
Sediment dominated
Total Suspended Solids (TSS)
Bloom dominated
Chlorophyll A (Chl A)
From Biber, Kenworthy, and Gallegos. Delineating Water Quality Criteria for SAV Habitats with a Bio‐Optical Model.