PROCEEDINGS TAMPA BAY AREA SClENTlFIC INFORMATION SYMPOaUM May 1982 Editors: Sara-Ann F, Treat Joseph L. Simon Roy R. Lewis 111 Robert L, Whitrnan, Jr. Sea Grant Project No. IR/82-2 Grant No, NASUAA-D-00038 Report Number 65 Florida Sea Grant College July 1985 Copyright O 1985 by Bellwether Press ISBN 0-8087-35787 Reproduced directiy from the author's manuscript. AII rights reserved. No part of this book may be reproduced in any form whatsoever, by pho tograplr or rnimeognph or by any other means, by broadcast or transmission, by translation into any kind of language, nor by recording electronicalIy or otherwise, without permissio~lin writing from the publisher, except by a reviewer, who may quote brief passages in critical articles and reviews. Printed in the United States of America. SEAGRASS MEADOWS OF TAMPA BAY - A REVIEW Roy R. Lewis III Mangrove Systems, Inc. Post Office Box 15759 Tampa, Fi 33684 M. 3, Durako M. D. MoffIer Florida Department of Natural Resources Marine Research Laboratory 100 8th Avenue S.E. St. Petersburg, FL 33701 R, C. Phillips Department of Biology Seattle Pacific University Seattle, WA 981 19 ABSTRACT Seagtass meadows presently cover approximately 5,750 ha of the bottom of Tampa Bay, in 81% reduction from the historical coverage of approximately 30,970 ha, Five of the seven species of seagrass occurring in Florida are found in the estuary, typically in less than 2 rn of water. These are: Thalassia testudinum Banks ex Konig (turtle grassh S rin odium filiforme Kutzing (manatee grassh Halodule wrightii Ascherson+ shoal - grass);~uppia maritirna L, (widgeon= and Halophila engelmannii Ascherson, The dominant species are turtle grass and shoal grass. The meadows are subdivided into five types: 1) mid-bay shoal perennial; 2) healthy fringe perennial; 3) stressed fringe perennial; 41 ephemeral; and 5) colonizing perennial. The general characteristics of these meadow types are discussed, In addition, the habitat values, physiological ecology, reproductive biology and on-going research work are summarized. Seagrasses in Tampa Bay reproduce primarily vegetatively. Sexual reproduction occurs in T. testudinurn and R. maritima. Thalassia seed production is low, however, and confined tothe southern part of the Bay. Seed quantities may be insufficient for significant colonization and restoration projects, INTRODUCTION 1,100 metric tons of seagrasses by Seagrass beds have long been dredging and filling in Boca Ciega Bay recognized as a food source and habitat resulted in the immediate loss of 1,800 for benthic invertebrates and fish metric tons of infauna, and the annual (Phillips 19603 Randall 1965; Wmd et al. loss of approximately 73 metric tons of 1969). Hutton --et al, (1956) were among fisheries products and 1,100 metric tons the first researchers to recognize the of infauna (Taylor and Saioman 1968). importance of seagrass beds as fish and The loss of this habitat represented an wildlife habitats in Tampa Bay. They annual monetary ioss of $1.4 million. also recognized that development Godcharles (1971)found that the use of a activities along the shore and associated commercial hydraulic clam dredge in effects on these areas conflicted with Seagras beds uprooted all vegetation and conservation, fishing and recreational that no recofonization had occurred after interests. Indeed, the destruction of more than a year. He recommended that the use of these harvesters be prohibited productivity of seagrasses is believed to in grassy areas because of the be channeled through detritai pathways importance of such areas as nursery (Fig. 1 in Ogden 1980). grounds for the majority of Florida's Several studies dealing with Florida sport and comrnercizl species. In this seagrass beds and their associated animal regard, Lewis and Phillips (1980) found communiiies have included species lists that the loss of seagrass habitat in and population densities. (Voss and Voss Tampa Bay coincided with a reduction in 1955; Tabb and Manning 1961; Dragovich commerciaI landings of spotted seatrout. and Kelly 1964; Santos and Simon 1974; Seagrass habitat value is best Brook 1975; Stoner 1980; Livingston summarized by the scheme of Wood -et 1982). These studies show that diversity -ai. (1969): and abundance of fish and invertebrates are usually higher in grass beds than in I. Seagrasses have high growth and unvegetated habirats. Stoner (1980) production rates; found that abundances of epifauna, 2. The leaves support large numbers of suspension feeders and carnivorous epiphytic organisms with biomass polychaetes were correlated with approaching that of the seagrasses seagrass biomass. The increase in themselves; abundance of epifauna was related to 3. Although few organisms feed directfy increased surface zrea of leaf blades. on them, seagrasses produce large Taylor --et al, (1973) reported rhat for quantities of detritus which serves as each square meter of bed area, Thalassia a major food source for many species; leaf blades ave a total surfzce area of 4. Seagrasses bind sediments and up to 18 m '1. This large surface area prevent erosion, in turn providing a provides a correspondingly large amount quiescent environment in which a of substrate for epiphytes. great variety of organisms can grow; Mobile invertebrate epif auna, 5. Seagrasses provide organic matter including several species of echinoids, which encourages sulfate reduction asteroids and gastropods, feed upon the and an active sulfur cycie; and, seagrasses and epiphytes (Ogden 1980). 6. Seagrasses act as nutrient sinks and Other invertebrates such as some crabs, sources. shrimp and gastropods are carnivorous, feeding on smafIer herbivores and In addition, Ketchum (cited in Phillips detritus feeders. Some fish species 1978) has estimated that 80-90% of the within seagrass beds may folIow commercial and sport fish species depend developmental sequences that encompass on estuaries during all or part of their various rrophic levels from herbivory to fife cycle, and estuaries typically support carnivory (Livingston 1982). Many large seagrass beds. commercially important fish are present Dense populations of bacteria and in grass beds as juveniles obtaining both fungi are associated with seagrass beds food and shelter (Ogden 1980). The (Burkholder --et al. 1959; KIug 1980). major vertebrate consumers of sea- These microorganisms form a major grasses are sea turtles and manatees source of nutrition for detritus feeders (Zieman 1981). These animals "mow" or including various poiychaetes, crusta- "root" when feeding and can have ceans, mollusks and fish {Brook 1975; substantial localized impacts on grass O'Gower and W acasey 1967). Seagrass- beds (Packard 1931; Zieman 1981). derived detrita1 material is important in Waterfowl also feed on seagrasses which food webs within beds, and also in can constitute a major food source for detritai food webs based on material some species (McRoy 1966). exported from the system (Zieman 198 1). Direct herbivory forms the basis OCCURRENCE AND DISTRIBUTION for the third type of food web based on Eiseman (1980) notes the seagrasses. However, most of the occurrence of seven species of seagrasses in Florida: Phillips (1980) and Moffler and Durako (unpubiished data). Thus five of the 1. Thalassia testudinum Banks ex Konig seven Florida species of seagrasses have ' -ass) been reported to occur in Tampa Bay. filiforme Kutzing PhiIlips (1962, p. 81, sampling at 98 stations between Pinellas Point and 3. MaIodule wrightii Ascherson (shoal Terra Ceia Bay during 1959-60 (Fig. 11, grass) noted that "all attached plants were maritima Linnaeus (widgeon limited to waters inshore of the one fathom curve". Also, ".,. Diplanthera 5. Halo~hilaen~eirnannii Ascherson (Halodule) is dominant in the southern 6. Halophila decipiens Ostenfeid portions of the bay while Ruppia is 7. Halophila johnsonii Eiseman dominant in the most northerly-~rtions". Lewis and PhiIlips (1980) reported The last species is newly described the results of 226 samples collected (Eiseman and McMillan 1980) and seasonally at 18 inshore stations during historically has probably been confused 1980-8 1, and found 42.5% of rhe samples with H. deci iens- (Eiseman 1980). contained Thalassia testudinurn, 46.7% ~hi954)mentioned the HaIodule -wiii 19.0% Svrin~odium occurrence of five of these species in filiforme, 15.5% Ruppia rnaritima, and Tampa Bay: ThaJassia testudinurn, none contained Halophila engeImannii S yringodium filif orme, Halodule wrightii, (Table I). Table 2 lists the seagrass Halo~hija eneelrnannii. and .IIRUDD~~ associations found during the same -rnaritima. Phillips (1962) conducted the sampling program. Single species were first comprehensive field sampling for found in 83.3% of the samples. Four seagrasses in Tampa Bay during 1959-60 species associations occurred in the and- reported the - occurrence %f all of remainder of the sampIes, with H. these species except H, en~elmannii. wrightii/E. maritima being the most Taylor and Saloman (1969) summarized common (8.89/o),f o~lowed by -T. data for 773 benthic sampIes taken filiforrne (5.3%j, T. during 1961-65 along 18 transects within wrightii (2.2%) and Tampa Bay and noted the occurrence of wrightii/S.- filif orme seagrasses in 227 (34%) of the samples. No R. maritima was reported, probably Based on the currentiy available due to difficulty in distinguishing it from aerial photography of Tampa Bay (198 11, -H. wrightii without close examination. Figure 2 was prepared. It shows 5,750 ha -H. engelmannii was reported at only 2 (14,203 acres) of seagrass meadows in stations, both in Boca Ciega Bay. Taylor Tampa Bay, Similar working maps were (1973) also reported its occurrence prepared using vertical bla=k and white behind Egmont Key. More recentjy, it aerial photography of Tampa Bay , has been observed around Cockroach Bay (secured from the National Archives, in Middle Tampa Bay by Lewis and Washington, DC) that had been taken by Table 1. Percent species occurrence, Tampa Bay (Lewis and Phillips 1980), Percent of samples in which species was collected, n = 226. SPECIES PERCENT Thalassia testudinurn Halodule wrightii---- Syringodium filiforme RUDD~~maritima -Halophila engelmannii Figure I.