vallisneria americana restoration research in the

VALLISNERIA AMERICANA RESTORATION RESEARCH IN THE CALOOSAHATCHEE RIVER, LEE COUNTY, FLORIDA

FINAL REPORT

NOVEMBER 27, 2007

Submitted to:

CATHERINE CORBETT CHARLOTTE HARBOR NATIONAL ESTUARY PROGRAM

1926 Victoria Avenue Fort Myers, FL 33901

Submitted by:

CENTER FOR COASTAL ECOLOGY

MOTE MARINE LABORATORY 1600 KEN THOMPSON PARKWAY

SARASOTA, FLORIDA 34236

MOTE MARINE LABORATORY TECHNICAL REPORT NO. 1230

MOTE MARINE LABORATORY........................................................................................................... i

The Charlotte Harbor National Estuary Program is a partnership of citizens, elected officials, resource managers and commercial and recreational resource users working to improve the water quality and ecological integrity of the greater Charlotte Harbor watershed. A cooperative decision-making process is used within the program to address diverse resource management concerns in the 4,400 square mile study area. Many of these partners also financially support the program, which, in turn, affords the program opportunities to fund projects such as this. The entities that have financially supported the program include the following: U.S. Environmental Protection Agency Southwest Florida Water Management District South Florida Water Management District Florida Department of Environmental Protection Florida Coastal Zone Management Program Peace River/Manasota Regional Water Supply Authority Polk, Sarasota, Manatee, Lee, Charlotte, DeSoto and Hardee counties Cities of Sanibel, Cape Coral, Fort Myers, Punta Gorda, North Port, Venice, and Fort Myers Beach and the Southwest Florida Regional Planning Council.

MOTE MARINE LABORATORY.......................................................................................................... ii

TABLE OF CONTENTS

Table Of Contents ............................................................................................................ii

Introduction ..................................................................................................................... 1

Objectives ....................................................................................................................... 2

Methods .......................................................................................................................... 2

Outcomes And Adjustments To The Project ................................................................... 2

Discussion....................................................................................................................... 4

Acknowledgements ......................................................................................................... 5

References...................................................................................................................... 5

Figure 1. Vallisneria Study Sites From Burns et al. (2007). Initial Transplant

Experiments Were Conducted At VN3 And VN5 ........................................... 8

Figure 2. Mean Salinity Values For Vallisneria Stations In The Upper Peace River,

From Burns et al. (2007). Transplant Studies Were Initially Conducted At

VN3 And VN5 But Later Concentrated At VN3 .............................................. 9

Figure 3. Presence Of Vallisneria And Ruppia In The Upper Caloosahatchee River

From November 2004- July 2007, From Burns et al. (2007)........................ 10

MOTE MARINE LABORATORY ..................................1

INTRODUCTION Seagrasses serve as good indicators in determining the health and condition of estuaries and nearshore ecosystems (Johannson, 1991), as they are subject to a variety of stressors that are responsible for extensive losses of submerged aquatic vegetation (SAV). Among these stressors are urbanization with its accompanying sewage and industrial discharges, dredge and fill, anthropogenic eutrophication and alterations in upland and adjacent watersheds (Kemp, 2000). Balancing the supply of fresh water for increased urbanization and agricultural needs with requirements for estuarine health is a major issue for water managers (Doering et al., 2002). Altering the natural seasonal fresh water river flow into estuaries through river regulation, can interfere with biological productivity through disruption of seasonal patterns to which organisms have become adapted. This disruption usually results in decreased productivity by both primary and secondary producers that have become adapted to historic estuarine circulation regimes of freshwater runoff and tidal mixing to enhance feeding and survival of various life stages (Mann and Lazier, 1991). The Caloosahatchee Estuary, located on the southwest coast of Florida is subject to changes in fresh water flow from Lake Okeechobee based on managed water releases at the Franklin Lock and Dam, installed in the mid-1960s on the lower Caloosahatchee River. These fresh water releases alter the historic timing of natural fresh water flows as well as surpass the amount of freshwater to which local SAV beds were historically adapted. In conjunction with agricultural and urban runoff into the watershed, freshwater releases are considered to be the main environmental stressors within the estuary responsible for seagrass loss and degraded water quality (Wilzbach et al., 2000). Since aquatic vegetation is an excellent indicator of estuarine health, the effects of excessive fresh water input into the Caloosahatchee River can be tracked by monitoring the dominant SAV habitats and their associated communities. Vallisneria americana, commonly known as tape grass but also called water celery, eel grass, American eel grass, and American wild celery, is considered a freshwater species, but is a dominant SAV species occurring in distinct beds extensively dispersed throughout the shallow waters of the upper sections of nearshore aquatic habitats of the Caloosahatchee Estuary making it an important constituent of the oligohaline estuarine SAV community (Bortone et al., 1998; Kraemer et al., 1999; Bortone et al., 2000). Floral as well as faunal survival in the upper portions of estuaries is based on the ability to tolerate a broad range of salinities that occur within the estuary. Fluctuations in salinity are brought about by alternate periods of higher salinity during the dry season or drought periods and increased freshwater input during the wet season, which may be augmented by excessive freshwater runoff events due to hurricanes and discharges from Lake Okeechobee and the surrounding watershed (Zieman and Zieman, 1989). This adaptation to extreme salinity fluctuation makes studying and monitoring tape grass and its associated communities an excellent means of investigating the effects freshwater releases have on the health of the estuary (Bortone and Turpin, 2000).


OBJECTIVES This research and restoration proposal was originally designed to evaluate the efficacy of transplanting Vallisneria americana into the tidal Caloosahatchee River. The strategy was to use mature stocks maintained in culture at Mote Marine Laboratory to establish a viable population of Vallisneria in the river. The project was intended to address CHNEP priority problem of Fish and Wildlife Habitat Loss by enhancing SAV habitat near shorelines, and promoting programs to enhance fishery resources. METHODS A complete description of methodological details for the original project is found in the May 19, 2005 scope of services accompanying the project contract. Main design features and method elements are summarized below. The establishment of a viable Vallisneria population in the river was to be attempted by transplanting captive-grown plants cultured for Caloosahatchee River stock. The stock was developed from seedlings collected from the river in 2002 by B.D. Robbins and planted in one of Mote’s research ponds. In subsequent years the captive plant population grew by sexual and asexual reproduction and flowered over an extended period (March through December), providing ample supplies of vegetative and seed resources for experimentation. (These stocks continue to flourish at Mote in 2007.) Mature seeds were grown out in trays and harvested when seedling height reached 10 cm. In addition, small rosettes (~10 cm blade length) were harvested from the culture pond to supplement seedling stocks. Two restoration sites were established on shallow subtidal mudflats on the north side of the tidal river, downstream of Beautiful Island (Figure 1). At each site a 6x5 array of 1 m2 planting blocks was assigned a treatment in a randomized block design. Rosettes were grouped and planted in each block and tagged with color-coded cable ties. Plantings were to be monitored monthly for rosette density, blade length, and herbivory. OUTCOMES AND ADJUSTMENTS TO THE PROJECT Seeds were harvested and grown out, and additional vegetative material was propagated during the end of 2005 and spring of 2006. After high river salinities fell in the summer of 2006 (Figure 2) plantings of all experimental materials were made in August 2006. The first return visit to the river discovered that the VN5 installations were damaged or missing, possibly due to accidental vessel traffic, or vandalism. VN 5 was aborted because its precise location was lost. At VN3 the experiment was aborted following an inability to retain rosettes because of their small belowground purchase. With the remaining installation a second experiment was begun as a continuation of the


first using only juvenile (intermediate) and adult (large) plants. Fifty of each size were transplanted at two VN3 sites, in groups of ten. Transplants were arranged 1 m apart along two transects of 5 m length. Unfortunately, this experiment had to be aborted by the first return trip when it was discovered that a grazing event by an unknown herbivore had removed nearly all transplants from each site (intermediate plants had greater survival than large ones). Using knowledge gained in the earlier experiments, a third experiment was begun using intermediate sized rosettes transplanted within cages. The experiment’s objective was to determine whether multiple rosette plantings survived better than single plantings. The experiment was protected from large herbivores with four cages using fowl wire attached to PVC frames. All cages were located in naturally occurring short Vallisneria mapped prior to the intermediate transplant experiment. One cage served as a control and replicates (n=5) of the treatments were planted in the other cages. Treatments were single plantings of rosettes, rosettes tied and planted in groups of five, and five rosettes naturally attached by rhizomes. By the end of September 2006 transplanted rosettes were responding positively to caging with growth rates greater than 25 mm per day, probably as a result of herbivore exclusion. Unfortunately, salinity rose rapidly beginning in October (Figure 2), causing a concomitant decline in the presence of Vallisneria throughout the upper river study area (Figure 3). Experiment 3 plantings also failed at this time. Because the duration of low-flow, high-salinity conditions could not be predicted, a decision was made to continue monitoring the cages and other VN3 sites where Vallisneria had naturally recruited. This decision was based on the possibility that natural or planted belowground material might recover if adverse conditions ameliorated. Monthly visits to VN3 failed to detect any regrowth of natural or planted Vallisneria and this finding is attributed to high salinity that persisted through July 2007. As the effort was being terminated two final tasks were undertaken to salvage some useful information. First, belowground biomass was sought by root-raking the substratum in each cage and surrounding VN3 areas where Vallisneria had existed prior to the drought. None was found. Second, five crab traps were baited with fresh captive-grown Vallisneria rhizomes, blades, and fruits and the traps were soaked for two days, in hopes of possibly identifying candidate herbivores. This final effort was unsuccessful.


DISCUSSION Unexpected, sudden levels of considerable herbivory encountered in Experiment 2 were a naturally caused setback to the project that informed Experiment 3. The caging experiment promised to compare and contrast treatment effects, illuminate growth and condition of natural stock, and possibly clarify the role of herbivory in Vallisneria success, but ten successive months of high salinity denied that promise. The response of Vallisneria to salinity is relatively well known, including studies specific to the Caloosahatchee River (Bortone and Turpin, 2000; Burns et al., 2007; Doering et al. 1999 and 2001; Kraemer et al., 1999; Robbins 2004). Wild celery represents a critical component of the tidal river ecosystem, and is a benchmark for river restoration, but in the foreseeable future the species will continue to experience setbacks due to river regulation and natural climatic variability. Herbivory of Vallisneria is less well known and the particulars of herbivory and its effects on wild celery in the Caloosahatchee River remain uncertain. Vallisneria may experience little to no herbivory (Davis et al., 2000), spatially localized turtle herbivory in Lake Okeechobee (Harwell and Havens, 2003), or widespread low to intermediate levels of herbivory by manatees (Lefebvre and Powell, 1990; Lefebvre et al., 2000). Manatee grazing on Vallisneria (in Kings Bay) may also be extreme (Hauxwell et al., 2004). Herbivory of SAV by manatees and other estuarine species is a growing concern in efforts to restore SAV in Tampa Bay via plantings (Fonseca et al., 1996; Johannson, 1991; Lewis et al., 2006). Winter aggregations of manatees in the tidal freshwater reaches of the Caloosahatchee River occur in most winters (Reynolds, 2007) and manatees may be responsible for Vallisneria losses in the Caloosahatchee River, but other SAV and Vallisneria herbivores are known including cownose rays (Orth, 1975) and waterfowl (Carter et al., 1986; Sponberg and Lodge, 2005). Turtle herbivory was significant at one site in Lake Okeechobee (Harwell and Havens, 2003) and grass carp or possibly mullet have been opined to be important Vallisneria herbivores in the Caloosahatchee River (Bortone and Ceilly, unpublished). The “clipped” nature of browsed Vallisneria in the Caloosahatchee River suggests a widespread, low level of herbivory (B. Robbins, pers. comm.). Because herbivory represents a major impediment to wild celery restoration, a major trophic pathway for the tidal river ecosystem, or both, it will be useful to document the responsible herbivorous species or species-group. It may be that the herbivore’s presence or feeding activity is modulated by salinity effects resulting from managed flows. Such modulation may be direct or mediated by predator effects but in either case, knowing the certain identity of Vallisneria grazers specific to the tidal Caloosahatchee River would offer new and possibly useful insight for river management.


ACKNOWLEDGEMENTS This research was supported by the Charlotte Harbor National Estuary Program through a grant to Mote Marine Laboratory (MML) with Dr. Bradley Robbins, formerly MML’s Landscape Ecology Program Manager, acting as Principal Investigator. Anamarie Boyes, Carol Weaver, Bernadette Hohmann, Lucas Jennings, Sara Peatrowsky, Pete Simmons, Michelle Gittler, and numerous MML interns conducted field studies. REFERENCES Bortone, S.A. and R.K.Turpin. 2000. Tape grass life history metrics associated with environmental variables in a controlled estuary. Pp. 65-79, In: S.A. Bortone (ed.), Seagrasses: Monitoring, Ecology, Physiology, and Management. CRC Press, Boca Raton. Burns, K., J. Gannon, C. Weaver, E. Estevez, A. Boyes and M. Gittler. 2007. SAV faunal relationships with regard to salinity and seasonality in the Caloosahatchee River, Florida. Final report to South Florida Water Management District. Mote Marine Laboratory Technical Report No. 1199. Carter, V.N., B. Rybicki and M. Turtora. 1996. Effect of increasing photon irradiance on the growth of Vallisneria americana in the tidal Potomac River. Aquatic Botany 54: 337-345. Davis, W.P., M.R. Davis and D.A. Flemer. 2000. Observations on the regrowth of subaquatic vegetation following transplantation: a potential method to assess environmental health of coastal habitats. Pp. 231-238, In: S.A. Bortone (ed.), Seagrasses: Monitoring, Ecology, Physiology, and Management. CRC Press, Boca Raton. Doering, P.H., R.H. Chamberlain, and D.E. Haunert. 2002. Using submerged aquatic vegetation to establish minimum and maximum freshwater flows into the Caloosahatchee estuary, Florida. Fla. Sci. 62(2): 89-105. Doering, P.H., R.H. Chamberlain and J.M. McMunigal. 2001. Effects of simulated saltwater intrusions on the growth and survival of wild celery Vallisneria americana from the Caloosahatchee estuary, (South Florida). Estuaries 24(6A): 894-903. Doering, P.H., R.H. Chamberlain, K.M. Donohue and A.D. Steinman. 1999. Effect of salinity on the growth of Vallisneria americana from the Caloosahatchee estuary, Florida. Fla. Sci. 62(2): 89-94. Estevez, E.D. 2000. Matching salinity metrics to estuarine seagrasses for freshwater inflow management. Pp. 295-307, In: S.A. Bortone (ed.), Seagrasses: Monitoring, Ecology, Physiology, and Management. CRC Press, Boca Raton.


Fonseca, M., J. Kenworthy, and F. Courtney. 1996. Development of planted seagrass beds in Tampa Bay, USA. I. Plant components. Mar. Ecol. Progress Series 132: 127-139. Harwell, M.C. and K.E. Havens. 2003. Experimental studies on the recovery potential of submerged aquatic vegetation after flooding and desiccation in a large subtropical lake. Aquatic Botany 77: 135-151. Hauxwell, J., T.K. Fraser and C.W. Osenberg. 2004. Grazing by manatees excludes both new and established wild celery transplants: implications for restoration in Kings Bay, FL. J. Aquat. Plant Manage. 42: 49-53. Johannson, J. O. R.1991. Long-term trends of nitrogen loading, water quality and biological indicators in Hillsborough Bay, Florida. Pp. 157-176. In: S.F. Treat and P.A. Clark (eds.). Proceedings, Tampa Bay Area Scientific Information Symposium 2, Tampa, FL. Kraemer, G.P., R.H. Chamberlain, P.H. Doering, H.D. Steinman, and M.D. Hanisak. 1999. Physiological response of transplants of the freshwater angiosperm Vallisneria americana along a salinity gradient in the Caloosahatchee Estuary (SW Florida). Estuaries 22:138-148. Kemp, W.M. 2000. Seagrass Ecology and Management: An Introduction. Pp. 1-6, In: S.A. Bortone (ed.), Seagrasses: Monitoring, Ecology, Physiology, and Management. CRC Press, Boca Raton. Lefebvre, L.W., J. P. Reid, W.J. Kenworthy and J.A. Powell. 2000. Characterizing manatee habitat use and seagrass grazing in Florida and Puerto Rico: implications for conservation and management. Pacific Conservation Biology 5(4): 289-298. Lefebvre, L.W. and J.A. Powell. 1990. Manatee grazing impacts on seagrasses in Hobe Sound and Jupiter Sound in southeast Florida during the winter of 1998-89. NTIS No. PB90-271883. 36 p. Lewis III, R.R., M.J. Marshall, S.A. Bloom, A. Hodgson and L.L. Flynn. 2006. Evaluation of the success of seagrass mitigation at Port Manatee. Pp. 19-40 in Seagrass Restoration: Success, Failure, and the Cost of Both. S.F. Treat and R.R. Lewis, III, eds. Mann, K.H. and J.R.N. Lazier. 1991. Dynamics of Marine Ecosystems Biological-Physical Interactions in the Oceans. Blackwell Scientific Publications, Inc., Cambridge, MA. Pp 466. Orth, R.J. 1975. Destruction of eelgrass Zostera marina by the cownose ray Rhinoptera bonasus in the Chesapeake Bay. Chesapeake Science 16(3): 205-208.


Provancha, J.A. and C.R. Hall. 1991. Observations of association between seagrass beds and manatees in East Central Florida. Fla. Sci. 54: 87-98. Reynolds III, J.E. 2007. Distribution and abundance of Florida manatee Trichechus manatus latirostrus around selected power plants following winter cold fronts: 2006-2007. Robbins, B.D. 2004. Habitat use of Vallisneria americana beds in the Caloosahatchee River: Final Report. Mote Marine Laboratory Technical Report No. 993. Sponberg, A.F. and D.M Lodge. 2005. Seasonal belowground herbivory and a density refuge from waterfowl herbivory for Vallisneria americana. Ecology 86(8): 2127-2134. Wilzbach, M.A., K.W. Cummins, L.M. Rojas, P.J. Rudershausen, and J. Locascio. 2000. Establishing baseline seagrass parameters in a small estuarine bay. Chapter 9 in S.A. Bortone (ed.), Seagrasses: Monitoring, Ecology, Physiology, and Management. CRC Press, Boca Raton.


Figure 1. Vallisneria study sites from Burns et al. (2007). Initial transplant experiments were conducted at VN3 and VN5.


Figure 2. Mean salinity values for Vallisneria stations in the upper Peace River, from Burns et al. (2007). Transplant studies were initially conducted at VN3 and VN5 but later concentrated at VN3.

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MOTE MARINE LABORATORY ................................10

Figure 3. Presence of Vallisneria and Ruppia in the upper Caloosahatchee River from November 2004- July 2007, from Burns et al. (2007).

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vallisneria americana restoration research in the

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