Status and Trends of Salinity, Water Clarity, and ... · • Status of chlorophyll -a, nutrients...
Transcript of Status and Trends of Salinity, Water Clarity, and ... · • Status of chlorophyll -a, nutrients...
Status and Trends of Salinity, Water Clarity, and Nutrients, in
Perdido and Pensacola Bay
James D. Hagy III, Michael C. Murrell1
1U.S. EPA Office of Research and Development, Gulf Breeze, FL
Overview
• Pensacola Bay general status • Long term trends in river flows • Changes in nutrient loading • Status of chlorophyll-a, nutrients and water
clarity. • Relationship between water clarity today and
historical seagrass depth distribution
Pensacola Bay Nutrients Regime
0
5
10
15
20
2550
100
0
5
10
15
20
25
30
35
µM -
DIN
PB summer med
Southeast US NW Florida
OH MH PH OH MH PH
Chlo
roph
yll-a
, µg
l-1
• N and P yield from the upper watershed is “relatively low”: N yield=262 kg km-2 y-1; P yield=22 kg km-2 y-1
• N & P loading is “moderate” due to large watershed: 12 g N m-2 y-1, 1 g P m-2 y-1
• Inorganic N and P concentrations in the Bay are “usually low,” especially in mesohaline (MH) and polyhaline (PH) reaches.
• Phytoplankton usually nutrient limited due to high water clarity; both N limitation and P limitation have been demonstrated.
• Microphytobenthos is important • Summer phytoplankton assemblage
dominated by cyanobacteria … consistent with nutrient limitation.
Freshwater Inflows from Rivers
• Analysis of Flows using USGS EGRET tools in R.
• Perdido River flow decreased 16% in past 30 years
• Escambia River (largest FW source to Pensacola Bay decreased 29% since 1980.
• Drivers are either parallel in both watersheds, or climatic.
Salinity, Temp in Lower Pens Bay
0
5
10
15
20
25
30
35
2/02 9/02 3/03 10/03 4/04 11/04 Salinity Water Temperature
Continuous T, S in Lower Pens Bay
Nitrate Flux – Escambia River
Data assembled by J. Caffrey
Nutrients in Perdido River
y = 5E-06x + 0.3188
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1997 1999 2000 2001 2003 2004 2005 2007 2008 2010
Tota
l Nitr
ogen
(mg/
L)
Perdido River at Barrineu Park
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
09/27/97 02/09/99 06/23/00 11/05/01 03/20/03 08/01/04 12/14/05 04/28/07 09/09/08 01/22/10
Tota
l Pho
spho
rus (
mg/
L)
Total Phosphorus in Perdido River
Data from WQP/STORET
Secchi Depth in Pensacola Bay Se
cchi
Dep
th (m
-1)
Esc R. 0
1
2
3
4
5
6
7
2/02 8/02 2/03 8/03 2/04 8/04
P01 P06 P08
Mid Bay. Lower Bay
Approximate Seagrass Depth of Colonization in lower Bay
0
1
2
3
4
5
6
7
3/14 9/14 4/15 10/15
River Mid Bay Lower Bay
Secchi Depth in Pensacola Bay Se
cchi
Dep
th (m
-1)
Approximate Seagrass Depth of Colonization in lower Bay
Light Attenuation in Pensacola Bay
P01
P02
P03
P04
P05
P06
P07
P08
P09
P10
P11
P12
P13
P14
P15
P16
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Mea
n Kd
(m-1
)
Esc R. Pass Blackw. SRS
2002-4 Data Based on regression of log PAR vs. depth (4pi sensor on CTD)
The same data is available for ~ 2011 to present
Seagrass Depth vs. Secchi Depth
• Ecosystem Metabolism is a useful measure of trophic status; possible indicator of nutrient pollution effects
• Useful approach is to infer rates from DO time series using Open Water Method
• Analysis typically assumes that advection has minimal effect on DO.
Pensacola Bay (1960) y = 1.0x - 0.37
r² = 0.88
0
1
2
3
0 1 2 3
Dept
h of
Col
oniz
atio
n in
196
0 (m
)
Mean Secchi Depth (Recent) (m)
49%
29%
Santa Rosa Sound Seagrass ‘60 vs ‘10
Seagrass Depth Distribution Santa Rosa Sound
• Ecosystem Metabolism is a useful measure of trophic status; possible indicator of nutrient pollution effects
• Useful approach is to infer rates from DO time series using Open Water Method
• Analysis typically assumes that advection has minimal effect on DO.
Depth (m)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Perc
ent C
over
of S
eagr
ass
0
20
40
60
80
100
19602010
Open Water Metabolism
• Ecosystem Metabolism is a useful measure of trophic status; possible indicator of nutrient pollution effects
• Useful approach is to infer rates from DO time series using Open Water Method
• Analysis typically assumes that advection has minimal effect on DO.
Conclusions
• Salinity is variable in Pensacola Bay. Declining river flow be important, but effects not documented at this point.
• Similar trends in freshwater flow present in Perdido River … likely climate driven
• Water clarity in Pensacola Bay is consistent with light expectations for seagrass at historical distribution … but seagrass isn’t there after many years.
• And, seagrass depth of colonization may still be declining in lower Bay and Santa Rosa Sound.
Total Nitrogen vs. Salinity
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 10 20 30
Tota
l Nitr
ogen
(mg/
L)
Mean Salinity
Perdido Bay
Pensacola Bay
Long-Term Mean Total NItrogen vs. Salinity (from FDEP)
Fertilizer use in Pensacola Bay Watershed
05
10152025303540
1940 1950 1960 1970 1980 1990
Gg
NitrogenPhosphorus
Alexander and Smith 1990, USGS OFR 90-130
Compiled by J. Caffrey
Total Nitrogen in Escambia River
• Analysis of TN loading using WRTDS in EGRET tools