Macroalgae as an Indicator of Estuarine Condition
Eric Milbrandt, Ph.D.
Marine LaboratorySanibel-Captiva Conservation Foundation (SCCF)
Caloosahatchee Science Workshop 2013Florida 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”
• 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
• 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
Previous studies in FLLocation No. of
Species
Groups Dominant Species Mean Biomass
Ft. Pierce (Benz et al.
1979)
63 3 blue-green12 green9 brown39 red
Acanthophora spiciferaChondria tenuissimaDictyota dichotoma
Hypnea spp.Spyridia filamentosaGiffordia mitchelliae
Gracilaria spp.Rosenvingea intricate
1.8-8.7 g dry wt m-2
Anclote estuary
(Hamm and Humm 1976)
65 5 blue-green15 green13 brown
32 red
Laurencia obtusaL.Poteaui
Digenia simplexSargassum spp.
240 g dry wt m-2
Mid-Indian River Lagoon (Virnstein and
Carbonara 1985)
- - Gracilaria spp.Spyridia filamentosa
Jania adhaerensRosenvingea intricata
Acanthophora spiciferaLaurencia spp.
Cladophora proliferaHypnea spp.
Dictyota dichtoma
0.03-164 g dry wt m-2
San Carlos Bay/Gulf of
Mexico (Milbrandt
2010)
96 1 blue-green12 green20 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
200
800
Biomass g DW m-2
Dixon 2008 TN = 1,873 MT (1,873 X 103 kg) yr-1 Caloosahatchee
Biomass 100-200 g m-2 not uncommonWhat is the tipping point?
Valiela (1997)
Fragmentation
Hypnea fragment survival data support the proliferation that was observed in late 2006, early 2007
Sanibel;02/21/07
(Vermeij et al. 2009)
• Significant differences in species composition and abundance at inshore vs. offshore locations
Common Species
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
Flo
w (
cfs
) 7 D
ay
Runnin
g A
vera
ge
0
2000
4000
6000
14000
16000
S79 DischargeS77 Discharge
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
Bio
mas
s (g
DW
m-2
)
0.000
0.005
0.010
0.015
0.020
0.025
Champia parvula
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
Bio
mas
s (g
DW
m-2
)
0.00.20.40.60.81.01.21.41.6
Sargassum spp.
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
Flo
w (
cfs)
7 D
ay R
unnin
g A
ver
age
0
2000
4000
6000
14000
16000
S79 DischargeS77 Discharge
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
Biom
ass (g DW
m-2
)
0.0
0.2
0.4
0.6
0.8
Agardhiella subulata
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
Biom
ass (g DW
m-2
)
0.00.51.01.52.02.53.03.5
Botryocladia occidentalis
INSHORE OFFSHORE
S-79 Flow
0 1000 2000 3000 4000 5000 6000 7000
Bio
ma
ss (g DW
m-2
)
0
50
100
150
200
250
300
350
INSHORE
S-79 Flow (30-day average)
0 1000 2000 3000 4000 5000 6000 7000B
iomass (g D
W m
-2)
0
100
200
300
400
500
600
700
OFFSHORE
2008-2010. Each point represents the mean biomass (n=20) Inshore CES11, near Fishermans Key; offshore is GOM12, 5 miles west of Redfish pass.
15
20
25
30
35
40
Sal
init
y (P
SU
)
NWR01
NWR02
NWR03
NWR04
NWR05
NWR06
NWR07
NWR08
NWR09
NWR10
0
0.3
0.6
0.9
1.2
1.5
1.8
TN
(m
g/l
)
NWR01 NWR02
NWR03 NWR04
NWR05 NWR06
NWR07 NWR08
NWR09 NWR10
90th Percentile All Florida Estuaries 1.2 mg/l
50th Percentile All Florida Estuaries 0.7 mg/l
5
10
15
20
25
30
35
40
Tem
per
atu
re (
oC
)
NWR01 NWR02
NWR03 NWR04
NWR05 NWR06
NWR07 NWR08
NWR09 NWR10
Aldridge and Trimmer (2005) Half saturation constants for green macroalgae (NO3) 0.3 mg/L N. In: Anderson and Conley (2005)
Ambrose EPA WASP models use 0.1 mg/L N half saturation for macroalgal external N uptake.
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)
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-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.
• 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
Indicator Considerations
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 Volume Wet Weight Date Volume Wet Weight10-23-
13 Halymenia floresia 19 mL 14.91 g 11/6/13 17.6 mL 20.81 g10-23-
13 Agardhiela subulata 16.8 mL 14.19 g 11/6/13 26 mL 23.24 g10-24-
13 Agardhiela subulata 40 mL 37.46 g 11/6/13 62 mL 62.73 g10-24-
13 Codium taylorii 102 mL 102.14 g 11/6/13 131 mL 135.35 g10-24-
13 Solieria filiformis 1.8 mL 1.13 g 11/6/13 2 mL 1.29 g10-24-
13 Gracilaria tikvahiae 12 mL 12.79 g 11/6/13 12.1 mL 11.95 g10-24-
13Botrycladia occidentalis 46 mL 46.67 g 11/6/13 71 mL 76.63 g