Indian River Lagoon
Species Inventory

Seagrass Beds

Often likened to the rich, grassy meadows of bucolic landscapes, seagrass beds are common features of coastal shallows and estuaries from the tropics to the Arctic Circle. Of the 72 species identified worldwide, seven are found in Florida—all of which grow in the Indian River Lagoon.

Photo credit: J. St. John, Wikimedia Commons

One of these, Johnson’s seagrass (Halophila johnsonii) is found nowhere in the world except in the Indian River Lagoon and was the first threatened seagrass to be listed under the Endangered Species Act.

Though often mistaken for seaweeds, seagrasses are evolved from terrestrial plants, and are the only class of flowering plant that is completely aquatic. Though they have leaves, roots, flowers and seeds, seagrasses lack strong supportive stems and trunks, an adaptation of terrestrial plants to overcome the force of gravity. Their natural buoyancy and flexibility allow them bend easily along with waves and currents.

Credit: P. Corapi

The Value of Seagrasses

A single acre of seagrass can produce over 10 tons of leaves per year. By comparison, an acre of most grass forage crops like alfalfa and switchgrasses produce from 3 to 8 tons of vegetation per year. This high level of productivity has inspired comparisons of seagrass communities as the marine equivalent of tropical rainforests. In Florida, turtle grass (Thalassia testudinum) can grow .07 to .19 inches (2 to 5 millimeters) per day; manatee grass (Syringodium filiforme) can put on .33 inches (8.5 mm) of growth in a day; and shoal grass (Halodule wrightii) can produce one new leaf every nine days during spring.

This vast biomass provides food, habitat, and nursery areas for myriad adult and juvenile vertebrates and invertebrates. A single acre of seagrass may support as many as 40,000 individual fish and 50 million small invertebrates. The dense foliage shelters numerous species of juvenile fish, smaller finfish, and benthic invertebrates such as crustaceans, bivalves, echinoderms. These leaves also provide abundant attachment sites for small macroalgae and epiphytic organisms such as sponges, bryozoans and foraminifera (forams), which account for up to 30 percent of the total above-ground biomass in some systems. Finally, seagrasses’ dense networks of underground rhizomes also serve as protection, hindering predators’ attempts to dig up the abundant invertebrate prey living in the sediments where seagrasses grow.

Credit: N. Price
Credit: L. Sweat
Credit: J. Dineen

Outside of their importance to biodiversity, seagrasses also offer several other valuable ecological benefits. Their sensitivity to changes in water quality makes them important indicator species that reflect the overall health of coastal ecosystems. And seagrass meadows also help dampen the effects of strong currents, providing protection to fish and invertebrates while also preventing the scouring of bottom areas.

Economically, Florida's 2.2 million acres of seagrass support both commercial and recreational fisheries that provide a wealth of benefits to the state's economy. Florida's Department of Environmental Protection (DEP) reported that in 2000, Florida's seagrass communities supported commercial harvests of fish and shellfish valued at over $124 billion. Including the nutrient cycling worth of seagrasses as well as recreational fisheries, DEP has estimated that each acre of seagrass in Florida has an economic value of approximately $20,255 per year, which translates into a statewide economic benefit of $44.6 billion annually.

Seagrass coverage throughout the Indian River Lagoon has been on the decline since mapping surveys began. In 1943, the IRL held over 71,000 acres (29,000 hectares); as of 2019, that figure had declined to just over 32,000 acres (13,000 hectares.)

Threats to Seagrass Communities

Seagrasses are subject to a number of naturally occurring stresses including storms, excessive grazing by herbivores and disease. Human-made threats include point and non-point sources of pollution, reduced water clarity, excessive nutrients in runoff, sedimentation and propeller scarring.

The effect of these stresses on seagrasses is dependent on both the nature and severity of the impact. Generally, if only leaves and above-ground vegetation are affected, seagrasses can recover from damage within a few weeks. However, when roots and rhizomes are damaged, a plant’s ability to produce new growth is severely impacted; plants may never be able to recover.

S. filiforme rhizome creeping into an area denuded by propeller scarring. Credit: Florida Fish and Wildlife Research Institute
Storms, Grazing and Disease

Several natural processes can negatively affect seagrasses. Wind-driven waves from heavy storms can break or uproot seagrasses. Additionally, a number of small and large marine animals disturb seagrasses while foraging, including sea urchins and the endangered West Indian Manatee (Trichechus manatus). Other species, such as crabs, fishes, skates, and rays disturb rhizomes and roots, and can tear apart seagrass leaves as they forage for concealed or buried prey.

Credit: C. Beard (Flickr)
Credit: L. Hall
Credit: R. Spratt

A wasting disease, thought to be caused by a marine slime mold, caused extensive damage to Zostera eelgrass beds in temperate coastal areas during the 1930s, causing a die-off of up to 90 percent of all eelgrass in North America. Introduced seaweed species can also compete with and displace native seagrasses.

Human Impacts

By far, human activities have the greatest impact on Indian River Lagoon seagrasses.

Reduced water clarity. Like land plants, seagrasses rely on sunlight, and water clarity determines how much light reaches their foliage. However, stormwater runoff from urban and agricultural areas carries household chemicals, oils, automotive chemicals, pesticides, animal wastes, and other debris, which are suspended as tiny particles in the water column. This clouding, or turbidity, reduces sunlight that reaches the seagrasses. In extreme cases, excessive sediments in runoff can even physically smother seagrasses.

Nutrient loading. As on land, nitrogen and phosphorous are important nutrients in freshwater, brackish and marine environments, allowing for the growth of microalgae and phytoplankton that serve as food for a great many organisms. But in overabundance, as when heavy volumes of stormwater carry excess fertilizers and animal wastes from land, nutrient loading causes massive blooms of algae that block sunlight into the deeper reaches of the lagoon.

Seasonal freshwater discharges from nearby Lake Okeechobee to manage lake levels also negatively impact lagoon water quality. In addition to reducing salinity levels, the freshwater releases also contain high levels of nutrients.

Dredging to maintain boating channels churns up sediments in the water column. While most impacts are short-term, if dredging is of a large enough scale and affects hydrodynamic properties of the area, such as the depth profile, water current direction, or current velocity, seagrasses may be severely threatened by sustained reductions of water clarity.

Prop scarring is caused by accidental or intentional boat groundings in shallow areas. When boaters enter water that is shallower than the draft of their vessel, propeller blades dig into seagrass beds as they pass over. This cuts not only seagrass blades but also frequently slashes underground rhizomes and roots. The resulting catastrophic furrow fragments the larger habitat, especially in areas where seagrass coverage is already sparse. Fragmented patches are susceptible to effects of erosion, and are vulnerable to increased damage as boaters continue to scar the meadow.

Propeller scarring in seagrass beds in Florida Bay. Credit: National Park Service, Florida DEP

Management and Restoration

As of 2015, the Indian River Lagoon had approximately 59,000 acres of seagrass coverage, down from 80,000 in 2007, a decline of approximately 26 percent. Since the 1940s, some areas of the lagoon have completely lost their seagrass meadows. Some studies estimate the lagoon has lost 95 percent of its seagrasses since 1981.

As a general rule, seagrass coverage remains steady or increases in areas with relatively pristine environmental conditions. In the area encompassing the NASA protected zones, Merritt Island Wildlife Refuge, and Canaveral National Seashore, seagrass coverage has remained unchanged over the last 50 years; in the central Indian River Lagoon, near Sebastian Inlet, seagrass coverage has increased markedly from historic levels, though much of this increase is due to the opening of the inlet at its present location.

By contrast, seagrass coverage in areas heavily impacted by overdevelopment of shoreline areas and wetlands tend to experience significant declines. In the 50-mile stretch of the IRL between the NASA Causeway and Grant, Florida, seagrass coverage has decreased by over 70 percent in the last 50 years.

Credit: Brevard Zoo

Managing water quality for seagrass health has improved overall water quality within the lagoon, increased overall amount and quality of available habitat, and is expected to increase biodiversity within seagrass meadows. St. Johns River Water Management District (SJRWMD) and South Florida Water Management District (SFWMD) are two of the organizations charged with managing water quality within the Indian River Lagoon. These organizations have actively pursued the goal of managing the lagoon in order to preserve and restore seagrass coverage to historic levels.

Management efforts include large-scale projects to remove muck from the lagoon bottom, construction of stormwater parks to intercept thousands of pounds of nutrients before they can enter the lagoon, and a 30-year monitoring program to document seasonal fluctuations in seagrass populations.

Seagrass restoration efforts are also widespread throughout the lagoon. Often, these projects also include clam planting and oyster reef rebuilding. In addition to nursery-grown material, some replanting efforts utilize seagrass fragments, dislodged by storms or boating activities, as starting material.

Further Reading

  • Almasi, M. N., C. M. Hoskin, J. K. Reed and J. Milo. 1987. Effects of natural and artificial Thalassia on rates of sedimentation. J. Sedimentary Petrology 57 (5): 901-906.
  • Applied Biology, Inc. and Ray L. Lyerly & Associates. 1980. Biological and environmental studies at the Florida Power & Light Company Cape Canaveral Plant and the Orlando Utilities Commission Indian River Plant, Volume II, Part I: Biological studies. Applied Biology, Inc., Atlanta, GA and Ray L. Lyerly & Assoc., Dunedin, FL. 272 pp.
  • Aspden, William Clarkson. 1980. Aspects of photosynthetic carbon metabolism in seagrasses. Master's Thesis, Fla. Inst. of Tech., Melbourne, FL. 75 pp.
  • Barile, Diane D. 1986. The Indian River Lagoon - seventy years of cumulative impacts. In: Proceedings Of The Conference: Managing Cumulative Effects In Florida Wetlands, Oct 17-19, 1985, New College of Univ. S. Fla., Sarasota, FL, E.D. Esteves, J. Miller, J. Morris and R. Hamman, eds., E.S.P. Publ. #38, Omnipress, Madison, WI, pp. 193-218.
  • Barile, Diane D., Christine A. Panico, Mary Beth Corrigan and Michael Dombrowski. 1987. Estuarine management - the Indian River Lagoon. In: Coastal Zone '87: Proceedings Of The Fifth Symposium On Coastal And Ocean Management, Volume 3, Orville T. Magoon, et al, eds., WW Div/ASCE, Seattle, WA/ May 26-29, 1987, Amer. Soc. of Civil Engineers, New York, NY. Pp. 237-250.
  • Brevard County, Florida. Office of Natural Resources Management. 1986. Seagrass maps of the Indian and Banana Rivers. Brevard County Office Natural Resources Management, Merritt Island, FL. 20 pp., maps, charts.
  • Brevard County, Florida. Water Resources Department. 1981. Review and update of the wasteload allocations for the Indian and Banana Rivers in Brevard County, Florida. Unpubl. Rep., Brevard County Water Resources Dep., Merritt Island, FL.
  • Carroll, Joseph D., Jr. 1983. Letter to District Engineer, U. S. Army Corps of Engineers, Jacksonville, Florida. Re: Seagrass mapping of central Indian River Lagoon region, Sebastian area. Letter Correspondence, U.S. Fish & Wildlife Serv., Vero Beach, FL. 7 pp., maps.
  • Clark, K. B. 1975. Benthic community structure and function. In: an ecological study of the lagoons surrounding the John F. Kennedy Space Center, Brevard County Florida, April 1972 to September 1975. Volume 1, experimental results and conclusions, NGR 10-015-008, Fla. Inst. of Tech., Melbourne, FL.
  • Darovec, J. E. Jr., J. M. Carlton, T. R. Pulver, M. D. Moffler, G. B. Smith, W. K. Whitfield, Jr., C. A. Willis, K. A. Steidinger and E. A. Joyce, Jr. 1975. Techniques for coastal restoration and fishery enhancement in Florida. Fla. Marine Res. Publ. No. 15, Fla. Dep. of Natural Resources, Marine Res. Laboratory, St. Petersburg, FL. 27 pp.
  • Dawes, Clinton J. 1987. The dynamic seagrasses of the Gulf of Mexico and Florida coasts. Fla. Marine Research Publ. No. 42, Proc. of Symp. on Subtropical Seagrasses of the S.E. U. S., Aug 12 1985, Michael J. Durako, Ronald C. Phillips & Roy R. Lewis, III, eds., Fla. Dep. Natural Resources, Bur. Marine Research, St. Petersburg, FL.
  • Down, C. and R. Withrow. 1978. Vegetation and other parameters in the Brevard County bar-built estuaries. NASA-CR-158242, REPT-06-73, Brevard County Health Dep., Titusville, FL. 90 pp.
  • Down, Cherie. 1978. Vegetation and other parameters in the Brevard County bar-built estuaries. Rep. No. 06-73, Brevard County Health Dep., Environ. Eng. Dep., Brevard County, FL. 85 pp.
  • Down, C. 1983. Use of Aerial Imagery in Determining Submerged Features in Three East-Coast Florida Lagoons. Florida Sci. 46(3/4), 355-362.
  • Durako, Michael J. 1988. The seagrass bed a community under assault. Fla. Naturalist, Fall 1988, pp. 6-8.
  • Durako, Michael J., Ronald C. Phillips and Roy R. Lewis III, eds. 1987. Proceedings of the symposium on subtropical-tropical seagrasses of the southeastern United States. Fla. Marine Res. Publ. No. 42, Fla. Dep. of Natural Resources, Bur. Marine Res., St. Petersburg, FL. 209 pp.
  • Eiseman, N. J. 1980. An illustrated guide to the seagrasses of the Indian River region of Florida. Tech. Rep. No. 31, Harbor Branch Found., Inc., Fort Pierce, FL.
  • Eiseman, N. J. and Calvin McMillan. 1980. A new species of seagrass, Halophila johnsonii, from the Atlantic coast of Florida. Aquatic Botany 9: 15-19.
  • Eiseman, N. J. and M. C. Benz. 1975. Studies of the benthic plants of the Indian River region. In: Indian River Coastal Zone Study, Second Annual Report, 1974-1975, Volume I, David K. Young, ed., Harbor Branch Consortium, Fort Pierce, FL, pp. 89-103.
  • Eiseman, N. J., M. C. Benz, and D. E. Serbousek. 1976. Studies of the benthic plants of the Indian River region. In: Indian River Coastal Zone Study, Third Annual Report, 1975-1976, Volume I, David K. Young, ed., Harbor Branch Consortium, Fort Pierce, FL. Pp. 72-86.
  • Eiseman, N. J., M. C. Benz, and D. E. Serbousek. 1976. Studies on the benthic plants of the Indian River region. In: Indian River Coastal Zone Study, Third Annual Report, 1975-1976, Volume 1, David K. Young, ed., Harbor Branch Consortium, Ft. Pierce, FL. Pp. 71-86.
  • Eiseman, N. J., Martha Meagher, Reubin Richards and Gregg Stanton. 1974. Chapter 8. Studies on the benthic and shoreline plants of the Indian River region. In: Indian River Study, First Annual Report, 1973- 1974, Volume II, David R. Young, ed., Harbor Branch Consortium, Fort Pierce, FL. Pp. 256-289.
  • Eiseman, N.J. 1980. An Illustrated Guide to the Sea Grasses of the Indian River Region of Florida. Harbor Branch Foundation, Inc. Technical Report No. 31. 24 pages.
  • Fenchel, T. 1970. Studies on the decomposition of organic matter derived from turtle grass, Thalassia testudinum. Limnol. Oceanogr. 15: 14-20
  • Fletcher, S.W. and W.W. Fletcher. 1995. Factors Affecting Changes in Seagrass Distribution and Diversity Patterns in the Indian River Lagoon Complex Between 1940 and 1992. Bulletin of Marine Science 57(1), 49-58.
  • Florida (State of). Department of Natural Resources. 1985. Banana River Aquatic Preserve management plan. Fla. Dep. of Natural Resources, Bur. of Environ. Land Management, Division of Recreation and Parks, Tallahassee, FL. 129 pp.
  • Fonseca, M.S., W.J. Kenworthy, and G.W. Thayer. 1998. Guidelines for the conservation and restoration of seagrasses in the United States and adjacent waters. NOAA Coastal Ocean Program Decision Analysis Series No. 12. NOAA Coastal Ocean Office. Silver Spring, MD.
  • French, Thomas D. and John R. Montgomery. 1983. Temporal dynamics of copper chemistry in the shoal grass, Halodule wrightii Aschers. Fla. Sci. 46 (3/4): 135-145.
  • French, Thomas Daniel. 1980. Temporal dynamics of copper chemistry in the shoal grass, Halodule wrightii Aschers. Master's Thesis, Fla. Inst. of Tech., Melbourne, FL. 58 pp.
  • Fry, B. and P.L Parker. 1979. Animal diet in Texas seagrass meadows: evidence for the importance of benthic plants. Est. Coast. Mar. Sci. 8: 499-509
  • Fuss, C.M. Jr, and J.A. Kelly, Jr. 1969. Survival and Growth of Sea Grasses Transplanted Under Artificial Conditions. Bulletin of Marine Science 19(2), 351-365.
  • Fry, Brian and Robert W. Virnstein. 1988. Leaf production and export of the seagrass Syringodium filiforme Kutz. in Indian River Lagoon, Florida. Aquatic Botany 30:261-266.
  • Fry, Brian. 1983. Leaf growth in the seagrass Syringodium filiforme Kutz. Aquatic Botany 16 (4): 361-368.
  • Gilbert, Steve and Kerry B. Clark. 1981. Seasonal variation in standing crop of the seagrass Syringodium filiforme and associated macrophytes in the northern Indian River, Florida. Estuaries 4 (3): 223-225.
  • Gilmore, R. G. 1987. Tropical-subtropical seagrasses of the southeastern United States: Fishes and fish communities. Fla. Marine Research Publ. 42: 117-137.
  • Gilmore, R. Grant, George R. Kulczycki, Philip A. Hastings and Wayne C. Magley. 1976. Studies of fishes of the Indian River Lagoon and vicinity. In: Indian River Coastal Zone Study, Third Annual Report, 1975-1976, Volume 1, David K. Young, ed., Harbor Branch Consortium, Fort Pierce, FL. Pp. 133-147.
  • Gilmore, R. Grant, John K. Holt, Robert S. Jones, George R. Kulczycki, Louis G. MacDowell III and Wayne C. Magley. 1978. Portable tripod drop net for estuarine fish studies. Fishery Bulletin 76 (1):285-289.
  • Gore, Robert H., Edward E. Gallaher, Liberta E. Scotto and Kim A. Wilson. 1981. Studies on decapod Crustacea from the Indian River region of Florida. XI. Community composition, structure, biomass and species-areal relationships of seagrass and drift algae-associated macrocrustaceans. Estuarine, Coastal and Shelf Sci. 12 (4): 485-508.
  • Gore, Robert H., Linda J. Becker, Nina Blum and Liberta E. Scotto. 1976. Studies of decapod Crustacea in the Indian River region of Florida. In: Indian River Coastal Zone Study, Third Annual Report, 1975-1976, Volume 1, David K. Young, ed., Harbor Branch Consortium, Fort Pierce, FL. Pp. 148-161.
  • Haddad, Kenneth D. 1985. Habitats of the Indian River. In: The Indian River Lagoon: Proceedings Of The Indian River Resources Symposium, Diane D. Barile, ed., Marine Resources Council of E. Central Fla., Fla. Inst. of Tech., Melbourne, FL. Pp. 23-26.
  • Hall, M.O., and N.J. Eiseman. 1981. The Seagrass Epiphytes of the Indian River, Florida I. Species List with Descriptions and Seasonal Occurrences. Botanica Marina 24, 139-146.
  • Hall, M.O. and S.S. Bell. 1988. Response of small motile epifauna to a complexity of epiphytic algae on seagrass blades. J. Marine Research 46 (3): 613-630.
  • Hanlon, Roger and Gilbert Voss. 1975. Guide to the sea grasses of Florida, the Gulf of Mexico and the Caribbean region. Sea Grant Field Guide Ser. No. 4, Univ. of Miami Sea Grant, Univ. of Miami, Miami, FL. 30 pp.
  • Harbor Cities Watershed Action Committee. 1991. Seagrass restoration in the Harbor Cities Watershed. Final rep., Harbor Cities Watershed Action Committee, Conrad White, ed., Melbourne, FL. 7 pp.
  • Harrison, P.G. 1989. Detrital processing in seagrass systems: A review of factors affecting decay rates, remineralization, and detritivory. Aquat. Bot. 35: 263-288
  • Heffernan, J. J., R. A. Gibson, S. F. Treat, J. L. Simon, R. R. Lewis III, R. L. Whitman, eds. 1985. Seagrass productivity in Tampa Bay: A comparison with other subtropical communities. Proc. Tampa Bay Area Sci. Info. Symp. p. 247.
  • Heffernan, John J. and Robert A. Gibson. 1983. A comparison of primary production rates in Indian River, Florida seagrass systems. Fla. Sci. 46 (3/4): 295-306.
  • Heijs, F.M.L. 1984. Annual biomass and production of epiphytes in three monospecific seagrass communities of Thalassia hemprichii (Ehrenb.) Aschers. Aquat. Bot. 20: 195-218
  • Howard, R. K. 1983. Short term turnover of epifauna in small patches of seagrass beds within the Indian River, Florida. Rep. presented at Benthic Ecology Meeting, Fla. Inst. of Tech., Melbourne, FL.
  • Howard, R. K. 1987. Diel variation in the abundance of epifauna associated with seagrasses of the Indian River Florida. Marine Biol. 96 (1): 137-142.
  • Howard, Robert K. 1985. Measurements of short-term turnover of epifauna within seagrass beds using an in situ staining method. Marine Ecology-Progress Ser. 22: 163-168.
  • Howard, Robert K. and Frederick T. Short. 1986. Seagrass growth and survivorship under the influence of epiphyte grazers. Aquatic Botany 24: 287-302.
  • Humm, Harold J. 1964. Epiphytes of the seagrass Thalassia testudinum, in Florida. Bulletin Marine Sci. Gulf and Caribbean 14 (2): 306-341.
  • Jensen, Paul R. and Robert A. Gibson. 1986. Primary production in three subtropical seagrass communities: A comparison of four autotrophic components. Fla. Sci. 49 (3): 129-141.
  • Kenworthy, W. J., M. S. Fonseca, D. E. McIvor and G. W. Thayer. 1989. The submarine light regime and ecological status of seagrasses in Hobe Sound, Florida. Annual Rep. National Marine Fisheries Serv., NOAA, S.E. Fisheries Cent., Beaufort Laboratory, Beaufort, NC.
  • Kulczycki, George R., Robert W. Virnstein and Walter G. Nelson. 1981. The relationship between fish abundance and algal biomass in a seagrass-drift algae community. Estuarine, Coastal and Shelf Sci. 12 (3): 341-347.
  • Lewis, R.R. III. 1987. The Restoration and Creation of Seagrass Meadows in the Southeast United States. Florida Marine Research Publications 42, 153-173.
  • Livingston, R.J. 1987. Historic Trends of Human Impacts on Seagrass Meadows in Florida. Florida Marine Research Publications 42, 139-151.
  • Marine Resources Council of East Florida. 1987. Marine Resources Council, third annual meeting, land and water planning. Symposium abstr., Marine Resources Council, Fla. Inst. Tech., Melbourne, FL. 17 pp.
  • Martin County Conservation Alliance. 1992. The environmental health of the estuarine waters of Martin County. Martin County Conserv. Alliance, Stuart, FL. 53 pp.
  • McMillan, C. 1982. Reproductive Physiology of Tropical Seagrasses. Aquatic Botany 14, 245-258.
  • McMillan, C. and F.N. Moseley. 1967. Salinity Tolerances of Five Marine Spermatophytes of Redfish Bay, Texas. Ecology 48(3), 503-506.
  • McRoy, C.P. and S. Williams-Cowper. 1978. Seagrasses of the United States: an ecological review in relation to human activities. US Fish and Wildlife Service FWS/OBS.
  • Mendonca, M.T. 1983. Movements and feeding ecology of immature green turtles Chelonia mydas in a Florida lagoon. Copeia 4: 1013-1023.
  • Moffler, M.D. and M.J. Durako. 1987. Reproductive Biology of the Tropical-Subtropical Seagrasses of the Southeastern United States. Florida Marine Research Publications 42, 77-88.
  • Moore, Donald R. 1963. Distribution of the sea grass, Thalassia, in the United States. Bulletin Marine Sci. Gulf and Caribbean 13(2): 329-342.
  • Morgan, M.D. and C.L. Kitting. 1984. Productivity and utilization of the seagrass Halodule wrightii and its attached epiphytes. Limnol. Oceanogr. 29: 1099-1176
  • Nelson, Walter G. 1980. A comparative study of amphipods in seagrasses from Florida to Nova Scotia. Bulletin Marine Sci. 30 (1): 80-89.
  • Nelson, Walter G. 1981. Experimental studies of decapod and fish predation on seagrass macrobenthos. Marine Ecology-Progress Ser. 5 (2): 141-149.
  • Odum, E.P. and A.A. de la Cruz. 1963. Detritus as a major component of ecosystems. Bull. Am. Inst. Biol. Sci. 13: 39-40
  • Packard, J. M. 1984. Impact of manatees Trichecus manatus on seagrass communities in eastern Florida. Acta Zoological Fennica No. 172, pp. 21-22.
  • Penhale, P.A. 1977. Macrophyte-epiphyte biomass and productivity in an eelgrass (Zostera marina) L. community. J. Exp. Mar. Biol. Ecol. 26: 211-224
  • Phillips, R. C. 1960. Observations on the ecology and distribution of the Florida seagrasses. Prof. Paper Ser. No. 2, Fla. State Board of Conserv., Marine Laboratory, St. Petersburg, FL. 72 pp.
  • Phillips, R.C. 1967. On species of the seagrass, Halodule, in Florida. Bulletin of Marine Sci. 17 (3): 672-676.
  • Phillips, R.C. 1976. Preliminary Observations on Transplanting and A Phenological Index of Seagrasses. Aquatic Botany 2, 93-101.
  • Phillips R.C. and E.G. Menez. 1988. Seagrasses. Smithsonian Institution Press. Washington, D.C.
  • Post, Buckley, Schuh and Jernigan, Inc. 1982. Environmental and cost-benefit analyses of discharge alternatives for Harris Corporation facilities in Palm Bay, Florida. Unpubl. Rep., Post, Buckley, Schuh and Jernigan, Inc., Orlando, FL. 122 pp. Maps, figures, refs.
  • Rice, John D., Robert P. Trocine and Gary N. Wells. 1983. Factors influencing seagrass ecology in the Indian River Lagoon. Fla. Sci. 46 (3/4): 276-286.
  • Salituri, Jeff Robert. 1975. A study of thermal effects on the growth of manatee grass, Cymodoceum manatorum. Master's Thesis, Fla. Inst. of Tech., Melbourne, FL. 67 pp.
  • Sargent, F.J., T.J. Leary, D.W. Crewz, and C.R. Kruer. 1995. Scarring of Florida's seagrasses: assessment and management options. Florida Marine Research Institute Technical report TR-1. St. Petersburg, Florida.
  • Short, F. T. and C. Zimmermann. 1983. The daylight cycle of a seagrass environment. Unpubl. Rep., presented at Benthic Ecology Meeting, Fla. Inst. Tech., Melbourne, FL.
  • Short, Frederick T. 1985. A method for the culture of tropical seagrasses. Aquatic Botany 22 (2): 187-193.
  • Snodgrass, Joel W. 1990. Comparison of fishes occurring in monospecific stands of algae and seagrass. Master's Thesis, Univ. of Central Fla., Orlando, FL. 51 pp.
  • Stephens, F. Carol and Robert A. Gibson. 1976. Studies of epiphytic diatoms in the Indian River, Florida. In: Indian River Coastal Zone Study, Third Annual Report, 1975-1976, Volume 1, David K. Young, ed., Harbor Branch Consortium, Ft. Pierce, FL. Pp. 61-70.
  • Stoner, A. W. 1980. Perception and choice of substratum by epifaunal amphipods associated with seagrasses. Marine Ecology-Progress Ser. 3: 105-111.
  • Stoner, Allan W. 1982. The influence of benthic macrophytes on the foraging behavior of pinfish, Lagodon rhomboides (Linnaeus). J. of Experimental Marine Biol. and Ecology 58: 271-284.
  • Stoner, Allan W. 1983. Distribution of fishes in sea grass meadows: Role of macrophyte biomass and species composition. Fishery Bulletin 81 (4): 837-846.
  • Stoner, Allan W. 1983. Distributional ecology of amphipods and tanaidaceans associated with three sea grass species. J. Crustacean Biol. 3 (4): 505-518.
  • Thompson, M. John. 1976. Photomapping and species composition of the seagrass beds in Florida's Indian River estuary. Tech. Rep. No. 10, Harbor Branch Found., Inc., Fort Pierce, FL. 34 pp, maps.
  • Thompson, M. John. 1978. Species composition and distribution of seagrass beds in the Indian River lagoon, Florida. Fla. Sci. 41 (2): 90-96.
  • Thorhaug, A. 1990. Restoration of mangroves and seagrasses: economic benefits for fisheries and mariculture. In: Environmental restoration: science and strategies for restoring the Earth. Island Press. Washington, D.C. Volume 265.
  • Tomasko, D.A. and B.E. Lapointe. 1991. Productivity and biomass of Thalassia testudinum as related to water column nutrient availability and epiphyte levels: field observations and experimental studies. Mar. Ecol. Prog. Ser. 75: 9-16
  • van Breedveld, J. F. 1975. Transplanting of seagrass with emphasis on the importance of substrate. Fla. Marine Res. Publ. No. 17, Fla. Dep. of Natural Resources, Marine Res. Laboratory, St. Petersburg, FL. 26 pp.
  • Virnstein, R.W., P.S. Mikkelsen, K.D. Cairns, and M.A. Capone. 1983. Seagrass Beds Versus Sand Bottoms: The Trophic Importance of their Associated Benthic Invertebrates. Florida Sci. 46(3/4), 363-381.
  • Virnstein, Robert W. and Patricia A. Carbonara. 1985. Seasonal abundance and distribution of drift algae and seagrasses in the mid-Indian River lagoon, Florida. Aquatic Botany 23 (1): 67-82.
  • Virnstein, R.W. and K.D. Cairns. 1986. Seagrass Maps of the Indian River Lagoon. Final Report to DER, September 1986. Seagrass Ecosystems Analysts, 805 E. 46th Place, Vero Beach, Florida. 27 Pages.
  • Virnstein, R.W. 1987. Seagrass-associated Invertebrate Communities of the Southeastern U.S.A.: A Review. Florida Marine Research Publications 42, 89-116.
  • Virnstein, R.W. 1995a. Seagrass Landscape Diversity in the Indian River Lagoon, Florida: The Importance of Geographic Scale and Pattern. Bulletin of Marine Science 57(1): 67-74.
  • Virnstein, R.W. 1995b. Anomalous Diversity of Some Seagrass-Associated Fauna in the Indian River Lagoon, Florida. Bulletin of Marine Science 57(1): 75-78.
  • Virnstein, R.W. and C. Curran. 1983. Epifauna of artificial seagrass: Colonization patterns in time and space. Unpubl. Rep. presented at Benthic Ecology Meeting, Fla. Inst. Tech., Melbourne, FL.
  • Virnstein, R.W., K.D. Cairns, M.A. Capone and P.S. Mikkelsen. 1985. Harbortown Marina seagrass study - a report to Old Park Investments, Inc. Unpubl. Tech. Rep. No. 55, Harbor Branch Found., Inc., Fort Pierce, FL. 5 pp., 8 tables.
  • Virnstein, Robert W. 1978. Why there are so many animals in seagrass beds, and does abundance imply importance? Fla. Sci. 41 (Suppl. 1): 24. (abstract)
  • Virnstein, Robert W. 1982. Leaf growth rate of the seagrass Halodule wrightii photographically measured in situ. Aquatic Botany 12 (3): 209-218.
  • Virnstein, Robert W. 1990. Seagrasses as a barometer of ecosystem health. Abstract, Eighth Annual Coastal Management Seminar, Dec 1990, Univ. Fla., Inst. Food & Agricultural Sci., Cooperative Extension Serv., Ft. Pierce, FL.
  • Virnstein, Robert W. and Mary Carla Curran. 1986. Colonization of artificial seagrass versus time and distance from source. Marine Ecology-Progress Ser. 29: 279-288.
  • Virnstein, Robert W. and Robert K. Howard. 1987. Motile epifauna of marine macrophytes in the Indian River Lagoon, Florida. I. Comparisons among three species of seagrasses from adjacent beds. Bulletin of Marine Sci. 41 (1): 1-12.
  • Virnstein, Robert W. and Robert K. Howard. 1987. Motile epifauna of marine macrophytes in the Indian River lagoon, Florida. II. Comparisons between drift algae and three species of seagrasses. Bulletin Marine Sci. 41 (1): 13-26.
  • Virnstein, Robert W., John R. Montgomery and Wendy A. Lowery. 1987. Effects of nutrients on seagrass. In: CM167 Final Report, Impoundment Management, Indian River County Mosquito Control Dist., Vero Beach, FL, Sep 30 1987, pp. 56-71.
  • White, C.B. 1986. Seagrass Maps of the Indian & Banana Rivers. Brevard County Office of Natural Resources Management, Merritt Island, Florida.
  • Young, D.K. and M.W. Young. 1977. Community structure of the macrobenthos associated with seagrass of the Indian River estuary, Florida. In: Ecology of Marine Benthos, B.C. Coull, ed., Univ. of S. Carolina Press, Columbia, SC. Pp. 359-381.
  • Young, D.K., K.D. Cairns, MA. Middleton, J. E. Miller and M.W. Young. 1976. Studies of seagrass-associated macrobenthos of the Indian River. In: Indian River Coastal Zone Study, Third Annual Report, 1975-1976, Volume 1, David K. Young, ed., Harbor Branch Consortium, Fort Pierce, FL. Pp. 93-108.
  • Young, David K., Martin A. Buzas and Martha W. Young. 1976. Species densities of macrobenthos associated with seagrass: A field experimental study of predation. J. Marine Res. 34 (4): 577-592.
  • Young, David K., ed. 1976. Indian River coastal zone study. Third annual report. 1975-1976. A report on research progress October 1975-October 1976. Harbor Branch Consortium, Fort Pierce, FL. 187 pp.
  • Zieman, J.C. 1982. The Ecology of the Seagrasses of South Florida: A Community Profile. U.S. Fish and Wildlife Services, Office of Biological Services, Washington, D.C. FWS/OBS-82/25. 158 Pages.
  • Zieman, J.C., R. Orth, R. Phillips, G. Thayer, and A. Thorhaug. 1984. The effects of oil on seagrass ecosystems. In: Recovery and Resoration of Marine Ecosystems, edited by J. Cairns and A. Buikema. Butterworth Publications, Stoneham, MA. Pps. 37 - 64. Seagrasses of the Southeastern United States 1960-1985. Florida Marine Research Publications 42, pp. 53-76.
  • Zimmerman, R.J., R.A. Gibson and J.B. Harrington. 1976. The food and feeding of seagrass-associated Gammaridean amphipods in the Indian River. In: Indian River Coastal Zone Study, Third Annual Report, 1975-1976, Volume 1, David K. Young, ed., Harbor Branch Consortium, Fort Pierce, FL. Pp. 87-92.
  • Zimmermann, Carl F. and John R. Montgomery. 1984. Effects of a decomposing drift algal mat on sediment pore water nutrient concentrations in a Florida seagrass bed. Marine Ecology Progress Ser. 19 (3): 299-302.
  • Zimmermann, Carl F., John R. Montgomery and Paul R. Carlson. 1985. Variability of dissolved reactive phosphate flux rates in nearshore estuarine sediments: Effects of groundwater flow. Estuaries 8 (2B): 228-236.
  • Zimmermann, Carl F., Thomas D. French and John R. Montgomery. 1981. Transplanting and survival of the seagrass Halodule wrightii under controlled conditions. N.E. Gulf Sci. 4 (2): 131-136.