Post on 18-Jan-2016
Effects of Nutrient Nonpoint Source Pollution on Seagrasses
in Redfish Bay
Kelly Darnell
GISWR Fall 2009
Eutrophication• Increase in nutrient concentration• Coastal eutrophication increasing
– Anthropogenic impacts: nutrient nonpoint source (NPS) pollution
• Negative effects on coastal organisms, systems– Decreased light irradiance, hypoxia, anoxia, decreased
water quality, stress species
www.marietta.edu
Seagrasses
• Submerged marine plants• Ecosystem services
– Sediment stabilization, particle settlement, food, habitat, nursery proper ecosystem functioning
• High light requirements make seagrasses sensitive to decreased water quality
• Declining worldwide, TX– Anthropogenic impacts
www.dep.state.fl.us
www.unep-wcmc.org
Seagrass Monitoring in Texas
• Dunton et al. (2005)– Monitoring program for seagrass health indicators
in Redfish Bay– Abiotic: water column nutrients, chlorophyll a,
total suspended solids (TSS), sediment nutrients– Biotic: seagrass cover, biomass, morphology
• Suggest input of nutrient NPS pollution– Water column nutrients
Objectives
• Obtain a visual representation of suggested nutrient NPS pollution in Redfish Bay– Better understanding of NPS pollution inputs– Cascading effects on seagrasses
• Water column, sediment and seagrass nutrients, seagrass morphology – Dunton et al. (2005)
Monitoring Sites: Redfish Bay, TX
• 30 sites• 2002-2005
– Summer data
Site 1
Site 30
Phosphate (PO4): 2002-2005
• No clear trends
Nitrate (NO3): 2002-2005
• No clear trends
• Water column nutrients spatially and temporally variable
• Suggested nutrient NPS input in 2002
Phosphate and Nitrate:
Water Column and Sediment Quality: 2002
1 6 11 16 21 260
5
10
15
20
25
30
f(x) = − 0.406155011278117 x + 14.0241711805539R² = 0.353337877988408
Total Suspended Solids by Site
Site
Tota
l Sus
pend
ed S
olid
Con
cent
ratio
n
1 6 11 16 21 260
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
f(x) = − 0.0231794586577679 x + 1.12311494252874R² = 0.220541742418652
Average Porewater Ammonium by Site
Site
Aver
age
Pore
wat
er N
H4 (u
M)
• TSS and average porewater NH4 higher in Northern part of Bay– TSS possibly
detrimental to seagrasses
– NH4 stimulate seagrass growth
Seagrass Parameters:
2002
• Dominant seagrass• Turtlegrass leaf
length and aboveground biomass slightly lower in Northern part of Bay– Seagrass may be
stressed
1 6 11 16 21 2605
101520253035404550
f(x) = 0.328351540088667 x + 24.9238567413289R² = 0.221138839726108
Average Turtlegrass Leaf Length
Site
Leaf
Leng
th (c
m)
1 6 11 16 21 260
50
100
150
200
250
300
350
f(x) = 2.60579688103101 x + 133.345673781427R² = 0.0516306401020048
Average Turtlegrass Aboveground Biomass
Site
Abov
egro
und
Biom
ass (
g DW
m−2
)
Conclusions So Far
• Results support existence of nutrient NPS pollution in Redfish Bay
• Results suggest seagrass may be negatively affected by indicated NPS pollution
Future Plans
• Compare nutrient inputs to local precipitation– Obtain an indication of runoff
• Visually represent:– Water column nutrient concentrations by site– Seagrass leaf nutrients by site and year– Seagrass above- and below-ground biomass
by site and year
Questions?
Sources
• Dunton KH, Kopecky AL, Maidment D (2005) Monitoring design criteria and biological indicators for seagrass conservation in Texas coastal waters. Final Report for Regional Environmental Monitoring and Assessment Program, EPA
• Texas World Imagery Basemap obtained from ESRI (resources.esri.com)