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. Location of station sites-in Tampa Bay, Boca Ciega Bay, and at Tarpon Springs (from Phillips 1960a).- Figure 2. Extent of seagrass meadows in Tampa Bay - 1982.

214

Figure 3. Estimated extent of seagrass meadows in Tampa Bay - 1879.

216 SEAGRASS MEADOW TYPES

. .I.

--.. --+_

RIH

RIH T/S T OR _-_-

I-- +-- -- RIH --- -.-7

Figure 4. Seagrass meadow types. MBSIP) - mid-bay shoal perennial; HF(P) - healthy fringe perenniai; SF(P) - stressed fringe perennial; (El - ephemeral; C(P) - colonizing perennial. SEAGRASS ZONATION

DIPLANTHERA 1

0 M -1 7 E A -2 s + RUPPlA

--3 PIPLANTHERA - HALODULE \ SYRlNGODlUM

B

? SPARSE ABUNDANT TH AL ASS1A +---*------, I--*

? SPARSE ABUNOANT -- SYRtNQODIUM

ASUUDANT DlPtANTHERA I -

RUPPIA ABUNDANT

0 6 10 16 20 26 30 36 40 SALINITY 9hr

MHHW - MEAN HIGHER HIGH WATER MHLW . MEAN HIGHER LOW WATER - MLHW . MEAH LOWER HIGH WATER MLLW - MEAN LOWER LOW WATER

Figure 5. Seagrass zonation (McNulty --et a!. 1972). A - the zonation of seagrasses in shallow water in Boca Ciega Bay just north of the Bayway to St. Petersburg Beach and in Tampa Bay just south of Bayboro Harbor, St. Petersburg. B - salinity preferences and tolerances of seagrasses (modified from PhiIiips 1960a- and Moore 1963). I II

PIPLANTHERA (RUPPIA IN LATE WINTER AND SPRING)

X THALASSIA AND SYFIIHGODIUM

Figure 6. Schematic drawing of Beach Drive station showing intertidal zones and maximum depth decIivity with location of grasses (from Phillips 1960b).- Diplan rhera = Halodule. Table 3. Chloro hyll a amounts for stations in various parts of Tampa Bay, 1969-1971 (mdmS 1 (from Turner and Hopkins 1974).

SUBDIVISION FALL WINTER SPRING SUMMER MEAN

Old Tampa Bay 16.5 3.6 5.4 26.6 13.0 Hillsborough Bay 31.6 56.5 22.0 41.7 40.0 Middle Tampa Bay 21.8 19.3 2.8 21.1 16.3 Lower Tampa Bay 4.8 5.6 11.4 16.1 9.5 Tampa Bay entrance 3.8 3.1 1.6 6.1 3.7 Boca Ciega Bay 12.5 6.7 7.4 16. Q 10.8 Terra Ceia Bay 19.7 2.5 13.7 16.7 13.2

Department of Natural Resources, seagrass species were seen in these personal cornmunicarion). A typical areas, Mangrove Systems, Inc. (1978) cross-section through a healthy fringe also noted the cyclic appearance and perennial seagrass meadow is disappearance of a monospecific Ruppia diagrammed in Figure 7. meadow near the Big Bend power plant in Stressed Fringe Perenniai. These Hiflsborough Bay during 1976-78. These meadows are similar to healthy fringe meadows probabIy represent the final perenniai meadows except that total stage of seagrass meadow degradation in cover is reduced within the basin behind Tampa Bay and would be foIiowed by the the offshore bar, Destabilization of the complete absence of meadows as offshore sand bar apparently leads to its presently seen in most of Hillsborough inshore migration and eventual Bay. disappearance (Fig. 4). This type of Colonizing Perennial. This meadow meadows generaily occurs in areas closer type is commonly found in a narrow band to Hillsborough Bay with its typical in the euphotic zone of man-made fills tenfold increase in average chlorophyll a such as Courtney Campbe11 Causeway, values (Table 3) and over areas closer to Howard Frankland Bridge Caseway, and the mouth of Tampa Bay. AIthough the Picnic Island fill, It is believed ro there are no experimental data represent a meadow type dominated by documenting competition between those species that can produce abundant phytoplankton and seagrasses in Tampa propagules that disperse and colonize Bay, such competirion has been theorized appropriate shallow substrates, As noted to occur in the shallows of other beiow, only Ruppia shows large scale estuaries where nutrient enrichment has sexual reproduction and seed production been followed by increases in microalgae in Tampa Bay. Seed producrion of the (phytoplankton) and macroalgae and other four species is rzre to non-existent decreases in seagrass meadows and therefore, these seagrasses colonize (Cambridge 1975, 1979; Davis and by dispersal of shoots/rhizomes produced Brinson 1980; Harlin and Thorne-Miiier asexuaily through fragmentation, Due to - 1981). the exposed nature of the man-made fills Ephemeral. These meadows are and their generally coarser sediments, composed almost entirely of Ruppia with Ruppia is not as common as in the occasiona1 sprigs of Haioduie. They are inshore portions of the fringe meadows. not present year round and their Both ~aloduieand ~~rin~odiurnproduce locations often vary from year to year. large amounts of detached rhizomes, Phillips (1962) noted the unusual particularly during storms, and it is appearance of Ruppia patches in theorized that these float into Hillsborough Bay along Bayshore unvegetated areas, attach Through new Boulevard and at the mouth of Delaney root formation, and estabiish new Creek in the winter of 1961, No other meadows. Thalassia produces relatively r SEAGRASS ZONATION - TAMPA BAY

MHHW MLHW MKW MLLW A. ALW MHHW . MEAN HMHER HlGH WATER / H.uU!&

MtHW MEAN LOWER HIGH WATER R. RUPPIA

MHLW MEAH HIGHER LOW WATER

MLLW, MEAN LOWER LOW WATER

Figure 7, Zonation in a healthy fringe perennial seagrass meadow, Tampa Bay. fewer detached shoo tirhizomes and, due dominant species in Boca Ciega Say to their increased buoyancy, these are (Hutton --er- al, 1956; ~orneroy1960; less likely to sink into an area TayIor and Saloman 1968) and in the appropriate for meadow estabiishment. seagrass beds surrounding Mullet Key. In Even if sinking and attachment do occur, both of these areas salinity rypicaily dower root and rhizome growth rates exceeds 30 ppt. Halophila kngbiimannii would make establishment of a new occurs subtidally mixed with ThaIassia meadow by asexual means less likely. and S rin odium. This may explain why Halodule and -GOb) found that Haladuie Syringodiurn are the dominant species in exhibited three growth f orrns in Tampa this meadow type. Bay which were related to the tidal zone where they occurred. In areas exposed PHYSIOLOGICAL ECOLOGY at both neap and spring low tides piants Tidal Zonation. Physiologicaf and were dwarfed. Subtidal areas morphological differences between characteristically had more robust seaghass species result in characteristic plants. Leaf length and width, rhizome zonation patterns relative ro tidal thickness, and internode length were all exposure (Fig. 8). Halodule wrightii is affected by the degree of tidal the most abundant species between neap exposure. Leaf apex features and high and neap low tide lines (Phillips internal cellular anatomy, features which 19603 1962). This seems to be related had been used to distinguish two species to the ability of Haloduie to tolerate of Haicdule . wrighrii and i-3- higher water temperatures and longer air beaudetii),ere found to vary sccording exposures than other species in the bay to the tidal zone in which The plants (Hurnrn 1956). Halodule also can be the were found, dominant species subtidally in lower Seagrass growth in the bay hzs salinity areas where Thalassia and been reported to be Iimited to bottom Syringodiurn are not found, such as the areas less than 2 merers (6 feet) deep more turbid parts of upper Old Tampa (Phillips 1962). High turbidity, and Bay. Thus zonation of Halodule is not consequently low light penetration, restricted entire1y by physical factors; seems to be responsible for the relatively rather it may be out-competed by shaIlow depth restriction, whereas Thaiassia and %ringodium in less turbid; desiccation and wave action limit the high salinity areas. Ruppia rnaritirna is shoreward edge of seagrass beds. commonly mixed with Halodule in salinity: Tidal Zonation of Ru~piz intertidal areas where the salinity is law in Tampa Bay may actuaify be a (Phillips 1960a, 1962; Earle 1972). secondary effect due to this species' ~alodule is usually most abundant preference for brackish water (Phillips between the neap low and spring Iow tide 1962). Of all seagrasses, Ruppia lines in higher salinities (Phillips 1960a).- tolerates the broadest range of s~lin~ty, All four of these species occur occurring in freshwater and in areas with subridally in Tampa Bay. Syringodium salinities in excess of 35 ppt laIthough it filif orme becomes dominant at the soring does seem that somewhat reduced I V low tide 'line, and frequently grows saiinity is required for it to set seed). interspersed with Thalassia in deeper Thorne (1954) and Humm (1973) water (Murnm 1956; Phillips 1960a, 1962; considered Ruppia primarily a freshwater Woodburn 196 lb). Although ~haEssiais species that can invade brackish waters the dominant srbtidal species in the Gulf aid the latter author did not consider ir of Mexico (Hurnrn 19'56; Earle 19721, ro be a true seagrass. This apparent Phillips (1962) noted thar it occurs in preference for lower salinites seems to relatively sparse amounts in Tampa be responsible for its dominance north of Bay. This is probably because salinities the Caurtney Campbell Causeway in Old in the bay are Iower than optimum for Tampa Bay (Phillips 1962). this speciks. However, Thalassia is the SHORE

, .. SHTLH......

WANTHEM - MOST ABUNOAHT 8UPP1A - SPARSE NLTL RUPPIA - MOST ABUNDANT DIPLAHTHER4 - SPARSE

THALASSIA - SPARSE SLTL THAtASSlA - MOST ASUNDANf QYRIMQOpruy - ABUNDANT ONLY WHEN THALASSIA IS SPARSE DIPLAHTyEPA - SPARSE BUPPl4 - SPARSE

SLTL * SLACK LOW TIDE LINE NHTL. NEAP HIGH TtDE LINE

snrL. SPRING nian TIDE LIME NLTL. NEAP LOW TIDE LIME

Figure 8. Schematic drawing of seagrass zonation in shallow water. Valid only in areas with salinity over 25.0 ppt. From Phillips 1960a.- Diplanthera = H alodule, Thalassia by contrast, is relatively McMiiian (1978) reported that sreno=(Moore 1963) and seems to be narrow-leaf ed variants of Thalassia, restricted to areas with salinity over 25 Halodule and Syringodium were ppt (Phillips 19602). Salinity also has characteristic of shallow bays with been observed to modify the morphology fluctuating temperatures, while broad- and growth of this species. Phillips leafed v,ariants occurred in water of (17602) reported shorter, narrower leaves relatively constant temperature. at low salinities and wider, Ionger leaves Chilling tolerances of these three species at saiinities near those of normal sea were also shown to correlate with their water, McMillan (1978) reported sirnTlar geographic distribution; Tampa Bay trends in leaf width of ~haiassiacultured populations ,exhibit lower chili tolerances at 20, 25.and 30 ppt. than northern Gulf :plants, but higher Halodule and Syringodium exhibit tolerances than Biscayne Bay or Florida maximum growth in moderately brackish Keys populations (McMillan 1978). warer (~hii-li~s19603 1962). Halodule is Water temperature is important in found throughout- Tampa Bay while modifying floral expression in Thalassia Syringodium is rarely - found- where Phillips 19603 Uoffier 2. 1981; salinities are below 20 ppt, reflecting the Philli~s. --et al. 1981). Reproductive buds broader salinity tolerance of the former are present as early as ~dtoberin Tampa (Taylor 1973). Halophila engelmannii has Bay populations of fler and Durako been reported to require relatively high unpub.) but visible buds are not evident salinities (Taylor 19731, which may until water temperatures start to partially account for its low abundance increase in spring (~ay- June). in rhe bay. Vegetative growth, floweri~gand Temperature. The distribution of fruiting of Ruppia coincide with the rise marine plants is Jargeiy controlled by of water temperature from winter to temperature {Earle 1972). Optimal spring and end when high summer water temperatures for a11 5 seagrass species in tern peratures begin (Phillips 1960a). Tampa Bay range between 20-30'~ Fruits seem to remain , dormant unTi1 (PhilIips 19603 Woodburn 1961b). winter and germinate when water Temperatures above or below this range temperatures again begin to rise. can resuit in leaf damage or dieback Substrate, Seagrass-substrzte (Phillips 19603 McMillan 1979). relationships represent a corn piex The rate of leaf growth in cyclical phenomenon. Substrate Thalassia seems to be controlled by characteristics are important factors in . warer temperature, while ultimate leaf determining which species of seagrass length is related to water depth (Phi3iips will be present (Phillips 19603 Patriquin 196~~Taylor --et al. 1972; Durako and 1972; Van Breedveld 1975). The presence Mof fler 1982). When water temperatures of a seagrass bed subsequently influences approach summer maxima in Tampa Bay, sediment dynamics (Scoffin 1970; Orth ThaIassia leaves become soft and flaccid, 1977; Fonseca 198 l), granulometry then break off due to protoplasmic (Grady 198 1) and chemistry (Patriquin breakdown and accelerated bacterial 1972; Kenworthy 198 1). Sediment, activity (Phiilips 19609- Durako and derritus trapping by leaves, and the Moffler unpub.) Leaf kllls also occur stabilization of this material by the during winrkr when short shoots become dense rhizome-root mars are paramount desiccated during the extrerneIy low in considering seagrass-substrate tides associated with the passage of coId relationships (Phillips 19603 Humm fronts. Recovery is slow because the 1975). The mechanisms of sedimentation plants are reiatively dormant at this are related to current flow dynamics in time. Unfortunately, leaf growth seagrass beds and result in a measurements relative to water characteristic bedf orrn raised above the ternperarure are not available for the original sediment ieve1 (Scoffin 1970; other species. Fonseca 198 1). Tborne (1954) reported that muddy sand (Phillips 1960a) to Iirnestone seagrasses in the Gulf of Mexico are bottoms and even the prop roots of limited to soft marl, mud or sand mangroves (Earle 1972). substrates. Dense ~halassia beds in The predominance of fine Tampa Bay occur on muddy sand sediments in seagrass beds indicates that substrates with silt and clay fractions once this material reaches the rhizome- dominating the mud Phillips 1960a).- The root mat it is usualjy not easily substrate also contains calcium resuspended, Transects across seagrass carbonate in varying amounts; this may beds have shown that sediment sorting be important in determining phosphate and mean particle size decrease and and sulfate availability (Patriquin percent organic matter increases as one 1972). .The depth of rhizomes and roots proceeds from bare sand ro the interior in the sediments seems to depend on the of the bed (Fig. 8; Orth 1977). Water depth of the redox potential depth also decreases from fringe to mid- disconrinui ty (R PD 1 layer, as ~halassia bed regions (Zieman 1972; Durako and requires reducing conditions for normal Moffler 1982). Intertidal seagrass deveiopment. This requirement is sediments have almost twice the organic related to the nutrient reauirernents of and carbonate carbon content of Thalassia (Patriquin 1972): Anaerobic unvegetated- sand flats (Grady 198 1). nitrogen fixation in the sediments seems Growth. It is somewhat to be the source of nitrogen for this paradoxical that rhizome branching and species' growth This activity has been growth are recognized as being largely shown -to be much greater in Thalassia responsible for the building of seagrass rhizosphere sediments than in non- meadows (Tomlinson 19741, yet most of rhizosphere sediments in Tampa Bay the .information on seagrass growth deals (Babiarz 1976). Fixed nitrogen is taken with leaf blade growth. This is due to up in a reduced form as ammonium the ease with which leaf growth can be {Patriquin 1972) while sulfur seems to be monitored and the importance of leaves taken up as the reduced sulfide (Fry and as a substrare and food for many Parker 1982). organisms. Until recently it was not Haioduie occurs on the same possible to directly measure growth rates substrate types as Thalassia, as well as for below-ground structures in a on extremely coarse muddy sands nondestructive manner. In this regard, (Phillips 19603 Grady 198 1). However, Fuss and Kelly 11969) measured Thalassia Halodule is more prevalent on oxidized root growth by sysrernatically sacrificing substrates. Substrate type does not seem transplants over a 12-month period and to directly influence the distribution of comparing root lengths to native piant S yringodium (Phillips 1960a).- The depth samples in Boca Ciega Bay. Durako and of the RPD layer also seems Moffler (198 1) developed a laboratory inconsequential as Syringodium roots culture technique in which both leaf occur in both oxidized and reduced blade and root growth of individual substrates (Patriquin and Knowles Thalassia seedIings could be directly 1972). This ability to grow in both types measured. Their results revealed of substrates reflects the intermediate morphogeographic variations in growth successional nature . - of Svrin~odium.I patterns for seedlings from Tampa Bay, which is thought to follow Halodule and Biscayne Bay, and the Florida Keys. precede ThaIassia in the temporal Tampa Bay seedlings exhibited rhe development of a seagrass bed, lowest leaf blade and root growth rates Ruppia is found on predomina~ely (Tables 4 and 51, and generaIly had the mud and silt substrates containing finer narrowest leaf blades of the rhree textured sand than substrates associated populations under a variety of with the other three species IPhiJlips conditions. McMillan (1978) aiso found 1960a). Halophila has been observed to the same pattern for leaf blade widths growon substrates ranging from soft and suggested that the ecoplastic limits Table 4. Root and leaf bJade growth of Thaiassia testudinum seedlings in agarlseawater cultures after three months. 1.0. = Instant Ocean; N.A. = nutrient agar; NH-13 =: nurrien: enriched seawarer; M.A. = marine agar. Values represent the mean of four replicates.

Total Root Length (cm) Leaf Area (crn2) Tampa Biscayne Florida Tampa Biscayne Florida Treatment Bay Bay Keys Bay gay Keys ---60 ml tubes

Mean 2.18 6.14 5.37 4.18 4.35 6.04 Root I{/ 2.50 3.8 1 2.47 Seedling Length/root 0.87 1-61 2.21 ---80 rnl tubes I,O./N .A. 3,27 12.10 14.98

Table 5, Leaf growth rares of Thalassia testudinum seedlings in laboratory cultures. Numbers in parentheses indicate a growth index where: growth index = (mean leaf area/seedling)/(m ean leaf @/seedling),

Growth Interval Shoot Growth Rates (crn2/rno) (months) Tampa Bay Biscayne Bay Florida Keys Treatment

Tube Cultures

60 ml rubes 3 80 ml tubes 3 -Pot Cultures Instant Ocean 5 von Stosch's 5 Peat Pellets 3 of populations are geneticalIy controlled. shoots were included (~ornero~1960). Several authors have measured leaf Biomass values reported for leaves lengths of ThaIassia to monitor its of Thalassia from ~a;~o?Springs are growth in Tampa Bay (Phillips 19603 high-(601-819 g dwt/rn than most Taylor --et a1. 1973; Durako and Moffler previous studies because samples were unpub.) These measurements have taken in dense grass beds rather Than at revealed a bimodal seasonal growth random (Table 6; Dawes --et al. 1979). By pattern (Fig. 9). Leaf lengths increase contrast, values in Tampa Bay are much from winter minimums to a peak in early lower, ranging from 0.41-52.7 g dwtlm2 summer. There is a summer dieback {Heffernan and G'bson, pers. comm.) to related to, high water temperatures, 25-180 g dwr/rni (Lewis and Phillips decreasing salinity, and flowering. This f 9801, reflecting suboptimal conditions is followed by an increase to a typically for this species within the bay. The lower peak in early fail, Leaf lengths latter study also reported root biomass increase at a rate of 5 cmlmonth during values of 600-900 g dwt/rn2 (Table 6). the period of maximum growth and can Below-ground biomass exceeds reach lengths exceeding 30 cm. Taylw shoot biomass in Hafodule and --et al. (1973) showed that ThaIassia can S rin odium within the Bay as well withstand periodic leaf cutting and &&TI- Lewis and Phillips (1980) harvesting without apparent damage. reported root and rhizome biomass The authors qualified their findings, ranges from 60-140 g dwf/rn2 for stating that they did not study the long Halodule and from 160-400 g dwtlm 2 for term effects of harvesting, and S yringodiurn. The comparatively lower suggested that this might be detrimental shoot biomass values were 38-50 to both the plants and the associated dwt/rn2 and 50-170 g dwt/rn 5 communities, respectively. These vaIues are much Leaf growth of Thalassia near the higher than those reported by Hefferna Anclote River is lower than that in and Gibson (pers. coyrn.), 4-27 g dwt/m 9 F - -. . Tampa Bay, with an average growth rate and 5-11 V dwt/m for Halodule and of 1.3 cm/leaf/rnonth and a maximum Syringodium respectively. Ruppia rare of 2-5 cm/leaf/month (Ford et a1. biomass is almost equally divided 1974). Syringodiurn had higher Ieaf between above- and below-ground growth rates, averaging 6.7 struct es, being approximately 48 g cm/ieaflrnonth, and a maximum rate of dwt/my far each component during the 17.4 cm/leaf/month during the fall, spring (Lewis and Phillips 1980). Shoot Hatodule leaf growth was the highest and biomass then decreases to almost zero in ranged from 12.9 to 19.5 cm/ieaf/month. the winter while root biomass de-creases Biomass and Productivity. Humm to a low level of 12-20 g dwt/mL in the (1964)suggested that Thalassia is faU and levels off. The higher biomass probably the most important piant vafues generally reported for Thalassia species in the shallow marine waters of compared to the other species are a the Guif of Mexico. In Terms of biomass, resuit of the larger size 'of all three Burkholder --et al. (1959) estimated the major plant parts (Dawes and Lawrence standing crop of Thalassia i Puerto Ri o 19801, to be 2,809 g dryweightlm? (g dwt/rn 51, The productivity of seagrass of which 23% was leaf biomass. Phillips systems is regarded as high for marine (i960a) determined standing crop vaIues communities (Earle 1972). Pomeroy of ~Glassiablades in Boca Ciega Bay (1960) reported rhar at depths of less (~a-hwhich ranged from 98 to 325 g than 2 meters, which constituted 7596 of dwt/rnZ. However, Bauersfeid & Boca Ciega Bay, Thalassia and (1969) reported much higher leaf values Syringodiurn leaves were as important as (636 g dwt/m2) for this area. These phytoplankton and benthic microflora in values wouid more than double if roots, term of primary production, fixing 500 g rhizomes and below-ground portions of C/m 3lyr. Indeed, values for annual (CM) A TAYLOR ET AL. 1071 I 0 OURAKO d MOFFLER 1982

SUMMER WINTER DIE-BACK DIE-BACK I 1 I

o-' . JFMAMJJASOND AEAPAUUUECOE NBRAYNLGPT~c> MONTH

Figure 9. Monthiy leaf length of Thaiassia festudinum in Tampa Bay. Table 6. Biomass values for seagrasses in rhe Tampa Bay area.

Biomass (g dwt/rn2) SPECIES ABOVE-GROUND BELOW-GROUND REFERENCE

Thaiassia testudinum

Boca Ciega Bay 32.4 Pomeroy 1960 Bird Key 325 Phillips 196Ca Cat's Point 98 Phillips 19 60: Boca Ciega Bay 636 BauersfeId 1769 320-1,198 Taylor and Saloman 1968 Tarpon Springs Dawes --et af. 1979. Tampa Bay Heffernan and Gibson 1982 Tampa Bay 25-180 Lewis and Phillips 1980

Syringodium filiforme

Tampa Bay - H eff ernan and Gibson 1982 Tampa Bay 160-400 Lewis and Phillips f 980

Halodule wrightii

Tampa Bay - H ef f ernan and ' Gibson 1982 Tampa Bay 60- 140 Lewis and PhiiIips 1980

Ruppia maritima

Tampa Bay 18-48 Lewis and Phillips 198 0 production of Thalassia range from 200- Durako and Moffler unpub.) These 4,650 g c/mL (Odurn 1957; Phillips studies have revealed the presence of 1974). The higher values exceed the annual cycles in the levels of proximate producrivity of al agricultural crops constituents. These seasonal variations (Odum 1959) on a rnZ basis and are also in the levels and the changes in greater than phytopiankton production in aIlocation of the constituents within rhe upwelling areas off Peru, which are plants are important energetic considered some of the most productive considerations because many anirn a1 in the world (Ryther 969). Recent work communities depend either directjy on in Tampa Bay using 14C techniques has the plants or on detritus derived from

estimated nroduction rates. of.. Thaiassia.. . .. them (Fenchel 1970; Buesa 1974; syringodiu; and Halodule during the fali Greenway 1974). to be an order of magnitude higher than The chemicai composition of previously reported: 95, 72.6 and 81.2 mg Thalassia has been studied in more detail Clg dwtlh respectively (~effernanand than the other locally occurring species Gibson, pets. cornm.), Areal production (~ables7 and 8). Walsh and Grow (19721, rates were calculated to be 0.05, 0.12 and Dawes and Lawrence (1980) reported and 0.05 g ~/rn~/da~for Thalassia, that protein levels generally are highest S yringodiurn and Halodule using the during the spring and late summer, whil~ radiocarbon techniques. P toduction carbohydrate, ash and dry weight Ieveis values based leaf-growth range from peak in the falI. Durako and Moffler 2-15 mn clrnL/hfor Thalassia. from 2-37 (unpub.) found slightly different seasonal mg C/m'2' /h for- 5 rin odium' and from patterns; protein and carbohydrate levels 0.9-1.4 mg ~/m 2? for Halodule near the were low in spring and highest during fall Anciote River (Ford et al. 1974: Ford and and winter, Ash levels were lowest Humm 1975). during the fa11 and late winter, and The variation in productivity levels highest in mid-winter 'and summer. Dry determined using oxygen, "C and leaf weight levels of shoots and rhizomes growth techniques demonstrates the decreased during the spring, a period of dif ficulry involved in accurately high growth, and increased 60 high leveis measuring this parameter in seagrasses. in late summer and early fall. Dry Storage and recyciing of O2 and COZ in weight of roots decreased from a peak in the internal lacunar spaces of these the spring to fall, then increased during macrophytes can cause considerable the winter. The importance of spatiai errors when measuring production rates influences on seasonal patterns of via O2 and 14c techniques (Hartman and chemical constituents was also Brown 1967). Stapling techniques for demonstrated in this study. Distinctions measuring leaf growth can be traumatic between fringe and mid-bed samples to the ieaf and may affect basal growth were significant and of sufficient (~ordand Humm 1973). Therefore, the magnitude to alter apparent seasona: values obtained should be viewed as cycles. These spatial differences may estimates of dative rates rather than as represent successional gradients in which absolute values. Also, most seagrass coIonizarion occurs on the fringe and pr ductivity rates are expressed as per maturity is approached in the interior of rn2 without consideratian of total area the bed. and production to a system, Protein levels in Thalassia are Chemical Corn position. Because of highest in leaves, shoots and roots, their high productivity and organic reflecting biosynthetic activities. matter production, the chemical Carbohydrate levels are greatest in cornpositiun of the seagrasses has been rhizomes, which function as storage analyzed by numerous investigators organs (Tables 7 and 8). In this regard, (Burkholder --et ai. 1959; ~auersfeid-et--al, leaf cropping results in decreased 1969; Walsh and Grow 1972; Dawes --et ai. carbohydrate IeveIs as the reserves are 1979; Dawes and Lawrence 1979, 1980; utilized in blade regeneration (Dawes -et Table 7. A comparison of proxirr~ateconstituent values of Thalassia testudinurn in the Tampa Bay area.

Dry weight Ash Protein Carbohydrate Lipid ---(96 fresh wt) --(% dwt) --(% dwt) --(% dwt) --(% dwt) Reference Leaves - 24.8 13.0 35.6 0.5 Burkl~older--et al. 1959 8- 19 46-50 9-12 38.0 0.7 Bauersfeld --et al. 1969 15-20 30-40 3- 12 3-12 - Dawes --et at. 1979 15-22 33-43 5-15 5-10 - Dawes and Lawrence 1379 15-20 29-44 8-22 6-9 0.9-4 Dawes and Lawrence 1980

Short Shoots 12-12.9 47-56 3- 10 8-12 - Dawes and Lawrence 1979 9- 12 24-42 2-5 9-16 - Durako and Moffler 1982

Rhizomes 6 50 9.6 - - Bauersfeld et al. 1969 N -2 W - F 14-2 1 21-37 5-1 2 21-51 Dawes and Lawrence 1979 14- i 8 24-36 7-16 12-36 0.2-1.6 Dawes and Lawrence 1980 15-17 19-27 1-3 19-32 - Durako and Moffler 1382 Roots 11-15 26-36 2- 5 9- 16 - nurako and Moffjer 1982 Table 8. Chemical composition of Syringodium filiforme, Halodule wrightii, and Ruppia maritima in Florida.

Dry weight Ash Protein Carbohydrate Lipid ---(% fresh wt) --(% dwt) --(% dwt) --(% dwt) --(% dwt) Reference 5. filiforme leaves: 17-21 28-33 8- 13 16-22 1.7-6.2 Dawes and Lawrence 1980

short shoots: 13-18 27-4 1 10-14 13-27 0.9-3.6

H. wrightii KJ - c*, leaves: F3 16-27 25-32 14-19 13-19 1.0-3.2 Dawes and Lawrence 1980

short shoots: 13-19 25- 36 5-9 16-31 0.8-3.5

rhizomes: 20- 30 14-22 7-9 40-54 0.1- 1.6

-R. maritirna leaves: - 16-24 - Walsh and Crow 1972 rhizomes: 13-25 19-25 - -al. 1979; Dawes and Lawrence 1979). the Tampa Bay system. We (Moffler and Protein levels are higher and ash Ieveis Durako) have collected several male lower in the regenerated blades due to specimens of Halodule in June at Sister the presence of new growth and the Key off Bunces' Pass, However. Phillips absence of epiphytes (Dawes and --et -4. (1974) and McMillan (19761 found Lawrence 1979). abundant reproductive HaloduIe in Texas Caloric (i.e. energy) vaIues are during the summer. Intensive collection similar for all four species, averaging efforts are needed in order to determine approximately 3.5 kcallg dwt for leaves the reproductive dynamics of HafoduIe in and 3.7 kcai/g dwt for rhizomes [Walsh Tam pa Bay. and Grow 1972; Dawes and Lawrence With regard to the orher species, 1980). These values are comparable to McMillan (198 I) suggested that those of other seagrasses (McRoy 1970; Syringodium filif orme floral initiation Birch 1975; Harrison and Mann occurs during late fall or early spring in 1975). No seasonal patterns have been Gulf of Mexico and Caribbean reported for energy levels, indicating populations, with fruits occurring from that a1 though proximate composition January through June. Although varies seasonally, the energy contents of reproductive material was rare, we the plants remain unchanged. {~offler, Durako and Lewis) have collected female s~ecimens of REPRODUCTIVE ECOLOGY Syringodiilrn during May at Lassing Park Seagrasses- exhibit two modes of and Egmont Key. McMilIan (1981) propagation, vegetative and sexual. specula?ed that the rare flower in^ of Thalassia testudinum, Syringodium Gulf and Caribbean S yringodium rn$ be filiforme. Haloduie wriehtii and related in part to nutrient condirions. I - Halophila spp. are hydrophilous, He observkd highest fecundity in producing flowers under the water popujations in coarse sediments at St. surface with submarine poilination. Croix, U.S. Virgin Islands, and Texas, and Ruppia maritima produces flowers which lowest flowering in areas with high silt anthese at the water surface and has accum ularions. hydroanemo phiious pollination. Although reproducrive Halophila The majority of the past work on has not been found in the isolated Florida seagrass reproductive biology has populations of Tampa Bay, Mchiillan principally concerned descriptive flora1 (1976) has documented extensive morphology and anatomy (Phillips 19603 flowering in Redfish Bay, Texas. He Orpur and Borai 1964; Tomfinson 1969; indicated that a coincidence of day Tomlinson and Posluszny 19781, length, salinity and temperature were reproductive physiology (~armeisteinet criticai for reproduction. -al. 1968; McMillan 1980; Phillips --et aT Phillips (1960a) reported the 19811, and seed occurrence and seed occurrence of abundaFt fIowering Ruppia reserves (Lewis and Phillips 1981; in Tampa Bay. Flowering 2nd fruiting McMillan 1981). Except for brief typically occur in May and disappear in commentaries in Phillips' 1960 June in these populations. Although publication on seagrass ecology and Phillips did not observe Ruppia seedling distriburion, research on seagrass germination and development, he reproductive ecology has only recently speculated that because flowers and been published for Florida populations fruits are so abundant, colonization of (Grey *and Moffler 1978;' ~oiflkr--et al. new areas and expansion of existing beds 1981; Phillips --et al. 1981). are quite likely. We (Moffier and Studies on the reproductive biology Durako) have observed apparent of Tampa Bay seagrasses have primarily expansion of the Ruppia population at been confined to Thalassia testudinum. Lassing Park, but do not have PhiIlips (1960a)- did not find reproductive quantitative data for documentation, Halodule, Syringodium or Halophifa in The growth habit of Ruppia with its profusely branched rhizomes, and its reproductive buds in January. This was ability to rise off the bottom toward the the first report of flower buds of surface {reaching better light conditions ThaIassia occurring in mid-winter. These and allowing sexual reproduction), are early buds continued to develop and conducive to survivaI in Tampa Bay. anthesis occurred during May and June, Since Ruppia is the major component of the typical-. time for the species. an ephemeral rn eadow, areal expansion Phillips --et al. (1981) conducted a of this species in Tampa Bay may occur phenoIogical investigation of Thalassia if seagrass meadow degradation from selected sites in %he western continues. tropical A tiantic, including Tampa Bay, The majority of the literature from February 1976 to April 1979. Based concerning seagrass reproductive biology on field and laboratory studies, they in Tampa Bay concerns the dioecious indicated nearly synchronous flowering ~halassi-atestudinurn. Phillips (19605) of Thalassia at different latitudes which was the first to pubfish such was related to an indigenous temperature inform ation. He found flowering regime and natural photoperiod. They Thalassia on several occasions during his suggested that flowering was primarily survey of Tampa Bay seagrasses and related to temperature progressions reported that ten percent of the plants following winter minima. These collected in Boca Ciega Bay on May 22, temperature responses nay be 1958 were flowering. In a large grass genotypically different, thereby flat off Lassing Park, he observed only a accounting for a nearly synchronous very restricted patch of flowering anthesis at different latitudes. plants. He further pointed out that when Work is continuing on Thalassia Thalassia was in flower, only one sex was restudinurn reproductive ecology in observed .and no mixing of sexes Tampa Bay (FDNR, Marine Research occurred, which might explain the lack Laboratory, St. Petersburg). of. fruits and seeds in this population. Investigations to date have indicated the Phillips (1960d was aIso the first to following: report the occurrence of Thalassia seedlings at our latitude at Anclote Key, - Unpublished data colIected by Moffler In 1976, Grey and Moffler (1978) and Durako indicates that floral conducted the first quantitative study of initiation in Tampa Bay popuiations of flowering Thalassia populations in Tampa Thalassia may occur in late summer or Bay and surrounding waters. Nine sites earIy fall. Inflorescence growth is were surveyed in the Tampa Bay area slow over winter and increases (Fig. 10); six of these were in the bay logarithmically during March and April proper. Flowering occurred at ail sites with anthesis occurring during May and with females predominating over maIes June. However, throughout this time at a ratio of 3: 1. In addition, they found period early developmental stages of flowering density to vary independently inflorescences occur which may of short shoot density, Patchiness in the indicate generic diversity for floral spatial distribution of reproductive short induction, and that T. testudinurn may shoots was also noted, be a day neutral plant. In January 1979, Durako collected Thalassia testudinum short shoots with - The distriburion of sexuaIly immature fruits at Lassing Park (Moffler reproductive Thalassia shoots within --ex al. 198 I). The presence of fruits at popuiations is rypicali y patchy or this time of year represented a possible clustered. The Lassing Park phenological inversion for this species, population, however, has one of the since fruits of this size are normally highest percentages of reproductive found in June. In addition to the early short shoot density reported for this fruits, Moffler --et ai, (198 1) also reported species (average 23.0556, range O- the presence of early immature 92.31%). One of the Lassing Park Figure 10. Reproductive Thalassia sites in Tampa Bay. Thalassia meadows studied {circular seagrass population maintenance and bed) was comprised of ail female distribution is critical. These studies shoots, while surrounding Thalassia should include reproductive phenoiogy beds contained both rnaies and and the role of seed reserves. In addition f ernales. Y er, a puzzling phenomenon to furthering our knowledge of the at the Lassing Park site is the lack of reproductive dynamics of Thalassia, fruit and seed production, When information on the reproductive biology looking at percentages of male and and ecology of the other seagrass species female short shoots in anthesis over is enthusiasticalIy encouraged. time we find females in anthesis first, followed by male anthesis, Percentage MANAGEMENT PROBLEMS of females and males in anthesis peaks Documentation of' Functional at the same time and females are in Role. The functional role of seagrass anthesis past the time of male meadows in the Tampa Bay ecosystem is anthesis; therefore, there should be essentially unknown. From 12 box cores ample opportunity for polIination and taken at four stations (three with fertilization to occur. The seagrass seagrass) in Boca Ciega Bay in August meadows at tassing Park are shallow 1964 (Taylor and Saloman 19681, infaunal and during low tides water biomass (excluding Iarge molluscs and temperature becomes high ( 35'~). crus aceans) was estimated to be 137 These conditions may inactivate the (dry weight) for we!l-vege ated pollination process or possibly lead to bottoms in corn parisan to 12 g/rnZ far fruit abortion due to pathogens; a high the three replicates taken in an percentage of decaying inflorescences unvegetated area, Sieve size for these has been observed. It is unclear, samples was 0,701 mm. Santos and however, whether decay is a cause or Simon (1974) sampled quarterly for one effect phenomenon. On the other year in a seagrass meadow and adjacent hand, Egmont Key populations sand areas and found the greatest density complete their reproductive cycle and of polychactes (mean = 33,485/m2)at the produce viable seed. This popuiation is Thajassia stations, second highest at the at a site with good flushing and more inshore sand stations (mean = 17,220/m 2 stable temperatures and salinity, with and third highest at t e Haloduie stations perhaps less opportunity for disease. (mean = 13,313 g/m P1. The two sets of offshore sand zone stations had yuch Tbalassia testudinum seed lower den ities (means of 4,934 g/m and production in Tampa Bay is apparentiy 3,231 g/m 31. It is quite probable that the confined to areas south and west of high densities at the inshore sand station Pineilas Point, Fruits have been were due to rhe seagrass and algal wrack collected in the beach wrack along the decomposing aiong the shore and Skyway causeway, Mullet Key and providing a rich detriral food source not Egmont Key. Large numbers of fruits available at the two offshore sand have never been found during the last 5 stations. years of collecting in these areas; Routine fish sampling in Tampa typically less than 100 fruit (200-300 Bay (Springer and Woociburn 1960; seed) are collected in any one year. Seed Springer 1961) has resulted in the production in Tampa Bay is apparently identification of 27 1 species. Springer quite low compared to that in Biscayne and Woodburn (1960, p. 97) noted that: Bay and the Keys (Lewis and Phillips 1981). It appears that quantities are The characteristic ecological features insufficient for restoration efforts. of rhe shallow bay habitats we studied Further research is needed on are the presence of heavy botrom seagrass reproductive biology and vegetation (seagrass and algae) and ecology in Tampa Bay, Information on moderately high and stable salinities the role of sexual reproduction in ... The fish fauna decreases also in numbers and species with the change accumulations, stingray or manatee from summer to winter. The decrease feeding damage, erosion due ro increased is probably associated as cIosely with boat wakes, and reduction in downwelling the decrease in flora as temperature, light reaching seagrass ieaves due to for even in summer the areas bver the phytoplankton, algal blooms, and sandy bottoms contain few fish. The turbidity. Figure 11 shows the relative majority of the fish present are either chlorophyll a concentrations for the young or small; the adults of most major subunits of Tampa Bay measured species eluded capture with the monthly between 1972 and 1981. It is equipment used. apparent that there is an order of magnitude difference between those Individual species accounts in the areas at the mouth of Tampa Bay (2-3 same reference indicate the importance md1) and Hillsborough Bay (20-30 of seagrass habitat to certain species. mgll). Hiilsborough Bay has historicalIy l?egarding the sheepshead, A rchosargus received large amounts of treated and robatoce halus (~albaum),"we found untreated sewage and urban runoff, and f* f* about 50 mrn) primarily presently supports no perennial seagrass in l3ipknth;ra (~alodule)beds1; {p, 64); meadows. Only scattered ephemeral the speckled trout, C ynoscion nebulosus beds of Ruppia are found there. The (Cuvier), "spends most of its life over the lower portions of Tampa Bay, with lower grass flats ... juvenile stomach contents average chlorophyll a leve!s, presently do were comprised mainly of crustaceans: support relativeiy healthy seagrass m ysids, copepods, and especially meadows. In addition, massive blooms of caridean shrimpt1 (p. 52); and the pinfish marine macroalgae were documented in (Lagodon rhomboides L.), "one of the the mid-1960s (FWPCA 1969) in most ubiquitous and pientiful species in HiIIsbarough Bay and continue to the Tampa Bay area ..." (p. 651, they reappear (Lewis et al., in press), These noted was very abundant in seagrass were attributed to high nutrient meadows. This species is noted as an (nitrogen, phosphorus) levels due to important item in the diet of larger minimal sewage treatment in the 1950s predatory fishes such as snook. - and 1960s, but more advanced sewage Unfortunately, beyond these few treatment begun in 1978 has not studies there have been essentially no apparently reduced the incidence of algal quantitative faunal collections in blooms. Competition among several seagrass meadows in Tampa Bay. Work groups of primary producers (rnicroalgae, in other parts of Florida (Carr and macroalgae, and seagrasses) has been Adams 1973; Stoner 1979; Zimmerman et documented to result in decjines in -al. 1979; Gore --et al, 1981; Greening ax seagrasses in favor of microaigae in the Livinston 1982; Ziernan 1982) has shown form of phytoplankton or epiphytic algae the value of seagrass meadows and their on seagrass blades (Sand-3ensen 1977; associated invertebrate and fish Cambridge 1979). communities; such data is vitaj to more However, most of the work on fully understand the functional role of eutrophication and the resulting changes seagrasses in Tampa Bay. in aquatic plant communities has been Current Status. As indicated done on freshwater systems t~avisand previously, Iarge declines in seagrasses Brinson 1980; Spence 1982) and thus have occurred in Tampa Bay. Vital much remains to be learned about these questions presently unanswered are the probiems in marine ecosystems. Guist reasons for these Iosses (beyond actual and Humm (1976, p. 270) reported that burial or excavation), and whether they the macroaigae Ulva lactuca L., from ate continuing. Tampa Bay, grew progressiveiy faster in Concerning the first question, a increasing concentrations of sewage number of hypotheses have been effluent and noted that as the water generated. These include biocide temperature rises, "Ulva growth slows CHLOROPHYLL A

i'"-l'-' .,....l....l....I.'.,,.,., f 73 74 76 78 7 7 78 7 0 00 8 I 82 83 Y R LEGEND: - t-10 .-----LTB --MTB ----OTB

Figure 11. Chlorophyil a concetltrations in major portions of Tarnpa Bay. HB - Hillsborough bay; LTB - Lower Tampa Bay; MTD - ~iddle~arn~aRay; OTU - Old Tampa Bay. and loose masses ... are widely has been achieved using the three distributed by tidd currents ... these dominant species in Tampa Bay: T. masses remain over seagrass beds Iong testudinum H. wrightii, 5. fiiif orme enough to kill seagrass beneath them .,. (~hiilipsand~ewis,in Small sheets of Ulva up to 10 ft in diameter scaie experimentai work on seagrass wilI develop in early spring." transplantation has been conducted by a In light of the lack of research on number of researchers in Tampa Bay other factors, progressive eutrophication since 1968 but no large scale attempts to and reduction in downweiling Jight restore significant areas of seagrass in reaching seagrass meadows due to Tampa Bay have been attempted. The absorption by more abundant micro- and reasons for this are twofold. First, no macroalgae appears to be the most program or agency has any responsibility viable hypothesis concerning declines in for "restoring1' lost habirat in Tampa Bay seagrasses in Tam pa Bay. Research on and thus no funds are available presently the other hypotheses should be for such work, Secondly, because of the conducted, but only after the questions previously discussed problems of water of the role of nutrients and algae in quality degradation, it is not possible to Tampa Bay and the contribution of algal presently identify, with any confidence, by-products and resuspended sediments areas of barren bay bottom that might to "turbidity" are answered, now support seagrass meadows. Concerning the second question, 0bviousl y, if downweiling light has been regular monitoring (at feast every two reduced to the point that seagrasses years) of the areal extent of seagrass disappeareu and light levels remain low, meadows in Tampa Bay shoufd be then it would be a waste of time to try conducted to determine if their decline and replant seagrasses in those areas. is continuing. Thompson (1981) noted the On the other hand, due to the low continuing disappearance of meadows of fevel of successftll sexual reproduction of ~~rin~odi;rninmupper middle Tampa Bay seagrasses in Tampa Bay, few seeds are in 1979-80, This is not an encouraging- - produced to recolonize barren bay sign, particuiarly since a monitoring bottoms if downwelling light levels have program conducted by the U.S. Army improved. For this reason, it is Corps of Engineers (Jacksonvi~le recommended that restoration plantings District] designed to detect such losses using the latest technological advances failed to document their disappearance. in this field be employed to instal test Potentiai -for Restoration, plantings along a gradient from Techniques for the replanting of seagrass relatively clean water at the mouth of meadows damaged or eliminated by the bay to more polluted areas in or near man's activities have been investigated Hillsborough Bay. Such a gradient of for 35 years (Phillips 1982). Twelve installations, properly monitored, could species of seagrass around the world relatively quickly indicate the potential ' have been tested for their suitability in for restoring seagrass meadows in Tampa restoration projects, Some success Bay through active planting efforts.

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