Macroalgae as an Indicator of Estuarine
Condition
Eric Milbrandt, Ph.D.
Marine Laboratory
Sanibel-Captiva Conservation Foundation (SCCF)
Caloosahatchee Science Workshop 2013
Florida Gulf Coast University
11/20/13
Background
• “Unattached” macroalgae is a common
component of seagrass communities
– Provides food and refuge for seagrass
fauna (Virnstein and Carbonara 1985, Fry
1984)
– Has high levels of productivity (Williams
1977)
– Contributes to the DOC pool through
decomposition (Zieman 1984)
– High levels of nutrition, little refractory
carbon (Hermann 1994)
– Extensive drift algal abundances decrease
the amount of available light in seagrass
(William Cowper 1978, Montfrans 1984)
– Drift algal blooms decrease seagrass
vertical shoot density in the presence of
urchins (Macia 1999)
4/27/10, trawls in San
Carlos Bay
12/6/10,
near
causeway
Occurrences of “Drift Algae”
• Initially attached to substrata
such as seagrass shells rocks or
sponges and breaks loose
• Usually non-calcified fleshy or
filamentous, reproduce
vegetatively (Norton &
Matheison 1983)
12/15/12 Sanibel Lighthouse
• Large accumulations after storms
(Williams Cowper 1978) in Biscayne
Bay (Josselyn 1977)
• “Tumbling” in sparse seagrass in the
IRL (Virnstein 1985), up to 0.5 km/day
(Holmquest 1994)
10/19/13 Knapp’s Point after TS Karen
Previous studies in FL
Location
No. of
Species
Groups
Dominant Species
Mean Biomass
Ft. Pierce (Benz
et al. 1979)
63
3 blue-green
12 green
9 brown
39 red
Acanthophora spicifera
Chondria tenuissima
Dictyota dichotoma
Hypnea spp.
Spyridia filamentosa
Giffordia mitchelliae
Gracilaria spp.
Rosenvingea intricate
1.8-8.7 g dry wt m-2
Anclote estuary
(Hamm and
Humm 1976)
65
5 blue-green
15 green
13 brown
32 red
Laurencia obtusa
L.Poteaui
Digenia simplex
Sargassum spp.
240 g dry wt m-2
Mid-Indian River
Lagoon
(Virnstein and
Carbonara 1985)
-
-
Gracilaria spp.
Spyridia filamentosa
Jania adhaerens
Rosenvingea intricata
Acanthophora spicifera
Laurencia spp.
Cladophora prolifera
Hypnea spp.
Dictyota dichtoma
0.03-164 g dry wt m-2
San Carlos
Bay/Gulf of
Mexico
(Milbrandt 2010)
96
1 blue-green
12 green
20 brown
63 red
This presentation
0.01-224 g dry wt m-2
Drivers
• Eutrophication-Algal biomass linked to N-loading
– Waquoit Bay Massachusetts, Gracilaria tikvahae
(Valiela 1992)
– Bermuda, Caulerpa prolifera (Lapointe 1989)
– French Mediterranian coast, Ulva lactuca (Maze et
al 1993)
– Sanibel Island, Hypnea, Soleria Dawes (2003)
Caloosahatchee versus other estuaries
800
200
Biomass g DW m-2
Valiela (1997)
Dixon 2008 TN = 1,873 MT (1,873 X 103 kg) yr-1 Caloosahatchee
Biomass 100-200 g m-2 not uncommon
What is the tipping point?
Fragmentation
Hypnea fragment survival data
support the proliferation that was
observed in late 2006, early 2007
(Vermeij et al. 2009)
Sanibel;
02/21/07
Common Species
• Significant differences in species composition and abundance at
inshore vs. offshore locations
OFFSHORE
INSHORE
16000
16000
S79 Discharge
S77 Discharge
Flow (cfs) 7 Day Running Average
6000
4000
2000
6000
4000
2000
0
0
May-08 Jul-08 Sep-08 Nov-08 Jan-09 Mar-09 May-09 Jul-09 Sep-09 Nov-09 Jan-10 Mar-10 May-10 Jul-10
May-08 Jul-08 Sep-08 Nov-08 Jan-09 Mar-09 May-09 Jul-09 Sep-09 Nov-09 Jan-10 Mar-10 May-10 Jul-10
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.8
Sargassum spp.
0.020
Champia parvula
0.015
0.010
0.005
0.000
05/08 07/08 09/08 11/08 01/09 03/09 05/09 07/09 09/09 11/09 01/10 03/10 05/10 07/10
-2
Biomass (g DW m )
0.025
0.6
Agardhiella subulata
0.4
0.2
0.0
05/08 07/08 09/08 11/08 01/09 03/09 05/09 07/09 09/09 11/09 01/10 03/10 05/10 07/10
05/08 07/08 09/08 11/08 01/09 03/09 05/09 07/09 09/09 11/09 01/10 03/10 05/10 07/10
-2
Biomass (g DW m )
S79 Discharge
S77 Discharge
14000
-2
Biomass (g DW m )
-2
Biomass (g DW m )
Flow (cfs) 7 Day Running Average
14000
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Botryocladia occidentalis
05/08 07/08 09/08 11/08 01/09 03/09 05/09 07/09 09/09 11/09 01/10 03/10 05/10 07/10
OFFSHORE
350
700
300
600
250
500
Biomass (g DW m-2)
Biomass (g DW m-2)
INSHORE
200
150
100
400
300
200
50
100
0
0
0
1000
2000
3000
S-79 Flow
4000
5000
6000
7000
0
1000
2000
3000
4000
5000
6000
S-79 Flow (30-day average)
2008-2010. Each point represents the mean biomass (n=20) Inshore
CES11, near Fishermans Key; offshore is GOM12, 5 miles west of
Redfish pass.
7000
1.8
40
1.5
1.2
TN (mg/l)
Salinity (PSU)
35
30
NWR01
NWR01
NWR02
NWR03
NWR04
NWR05
NWR06
NWR07
NWR08
NWR09
NWR10
90th Percentile All Florida Estuaries 1.2 mg/l
0.9
NWR02
25
50th Percentile All Florida Estuaries 0.7 mg/l
NWR03
NWR04
0.6
NWR05
NWR06
20
NWR07
0.3
NWR08
NWR09
NWR10
0
15
40
Aldridge and Trimmer (2005) Half saturation
constants for green macroalgae (NO3) 0.3
mg/L N. In: Anderson and Conley (2005)
35
Temperature (oC)
30
25
Ambrose EPA WASP models use 0.1 mg/L N half
saturation for macroalgal external N uptake.
20
15
10
5
NWR01
NWR02
NWR03
NWR04
NWR05
NWR06
NWR07
NWR08
NWR09
NWR10
Sufficient nutrients in the lower
Caloosahatchee Estuary to support year
round macroalagal growth.
Driver-Irradiance
• Higher irradiances inshore from Dec. to May after N-loading.
• Offshore, high irradiances coincident with flows and loading
(SCCF, Ladyfinger Lakes 4/1/13)
Driver-herbivory
• Lack of inshore urchins?
Top Down Control
• Evidence from panhandle that grazer abundance can control
macroalgal proliferations (Heck and Valentine)
• Results from one offshore location with abundant grazers suggests
some top down control at GOM04 (Coen et al. 2010) but low salinities
prevent larval settlement in San Carlos Bay
Driver-Roughness
• Benthic habitat maps
(G. Foster 2010)
Driver-Temperature
• Temperature had a significant affect on photosynthesis and
daily growth, salinity did not (Brown, USF M.S. thesis 2001)
–
Temperatures can be several degrees warmer in shallow sites (SCCF RECON
data), growth rates from the field are needed.
Indicator Considerations
• Biomass and percent cover (Scanlan
2009 framework), N-loading,
residence time vs. growth rates
• Inshore and offshore locations
needed to capture large (extreme)
interannual differences in S79 flows
• Improve CHNEP mapping by
determining accuracy of SAV maps
(patchy/continuous, with/without
macroalgae)
• Improves SAV indicators by providing
additional drivers (space
competition) and ecosystem services
• Improves beach condition indicators
(red tide, bacteria)
• Methods and equipment proven and
tested in the 2010 study
SCCF Current efforts
• Growth and N uptake rates (ammonia, NOX, TN) of local species
• Measure growth rates (or mortality rates) of beach collected
drift algae
• Quantify biomass and percent cover from a 4 shore-side
locations
• Develop a key to common species in SW Florida
• Workshop with FDEP and others to teach the use of the keys to
identify to macroalgae to Genus and improve transect
monitoring
Growth Rates – field incubations
Date
Species
10-23-13
Halymenia floresia
10-23-13 Agardhiela subulata
10-24-13 Agardhiela subulata
10-24-13
Codium taylorii
10-24-13
Solieria filiformis
10-24-13 Gracilaria tikvahiae
10-24-13 Botrycladia occidentalis
Volume
19 mL
16.8 mL
40 mL
102 mL
1.8 mL
12 mL
46 mL
Wet Weight
14.91 g
14.19 g
37.46 g
102.14 g
1.13 g
12.79 g
46.67 g
Date
11/6/13
11/6/13
11/6/13
11/6/13
11/6/13
11/6/13
11/6/13
Volume Wet Weight
17.6 mL
20.81 g
26 mL
23.24 g
62 mL
62.73 g
131 mL
135.35 g
2 mL
1.29 g
12.1 mL
11.95 g
71 mL
76.63 g
Acknowledgements
Drs. Loh, Parsons,
Everham, A.J.
Martignette, Jeff
Siwicke, Brad Klement,
Keleigh Provost, Mark
Thompson, Drs. Greg
Foster, Ray Grizzle
Funding Partners:
James Evans, City of Sanibel
Steve Boutelle, Lee County, WCIND
Rob Loflin, City of Sanibel
Mike Campbell, Lee County