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” 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 FL LocationNo. of Species GroupsDominant SpeciesMean Biomass Ft. Pierce (Benz et al. 1979) 633 blue-green 12 green 9 brown 39 red Acanthophora spicifera Chondria tenuissima Dictyota dichotoma Hypnea spp. Spyridia filamentosa Giffordia mitchelliae Gracilaria spp. Rosenvingea intricate g dry wt m -2 Anclote estuary (Hamm and Humm 1976) 655 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 g dry wt m -2 San Carlos Bay/Gulf of Mexico (Milbrandt 2010) 961 blue-green 12 green 20 brown 63 red This presentation 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 Biomass g DW m -2 Dixon 2008 TN = 1,873 MT (1,873 X 10 3 kg) yr-1 Caloosahatchee Biomass g m -2 not uncommon What 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

INSHORE OFFSHORE

INSHOREOFFSHORE Each point represents the mean biomass (n=20) Inshore CES11, near Fishermans Key; offshore is GOM12, 5 miles west of Redfish pass.

Aldridge and Trimmer (2005) Half saturation constants for green macroalgae (NO 3 ) 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)

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.

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 DateSpeciesVolumeWet WeightDateVolumeWet Weight Halymenia floresia19 mL14.91 g11/6/ mL20.81 g Agardhiela subulata16.8 mL14.19 g11/6/1326 mL23.24 g Agardhiela subulata40 mL37.46 g11/6/1362 mL62.73 g Codium taylorii102 mL g11/6/13131 mL g Solieria filiformis1.8 mL1.13 g11/6/132 mL1.29 g Gracilaria tikvahiae12 mL12.79 g11/6/ mL11.95 g Botrycladia occidentalis46 mL46.67 g11/6/1371 mL76.63 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