The Ecology of the Seagrasses of South Florida - USGS National ...

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et a1. 1361b). The anount of nitrate is 2-7 OXYL'EN usually low or ahsent in sediments ds it is either rapidly rietabol izcti or converted to dinitrogen (M ) via deni trifyilly tjac- Post seagrass meadows have sufficient oxygen in the water coluinn for survival of teria. the associated plants and animals. Often the shallow beds can be heard to hiss Fron Sulfur bacteria are primarily respon- the escaping 0 bubbles in the late aftersible for riaintaining conditions necessary noon. Dense beds in shallow water with for the remineralization of nutrients in restricted circulation can show extrerlcly the sedirnent. By reducing sulfate to sul- reduced 0, levels or even anoxia late at fide, these bacteriamaintain the environ- night on a slack tide. This can be a rFiental conditions (Eh and pH) at a Icvcl greater problerl if there is a heavy load where the ni trogeri mineral iza tion proceeds of suspended organic sedirnent that would at a rdte gredter than its utilieatiarl by also corisulne oxygen. Generally the wind the rvicrobi a1 col-unurri ty . This produces rcqtl i red to
indication of a 1 ini tation on productivity the leaf sqrfaces available for desiccadue to hydrostatic pressure and not merely tion. Turtle grass grows in waters nearly light limitation (Gessner and Harimer as shallow as that of shoal grass. The 1961). shallowest turtle grass flats are covmonly exposed on spring low tides, frequently The maximum depth at which seagrasses with much leaf mortality. Throughout the are found is definitely correlated with range of 1 to 10 m (3 to 33 ft), all of the available light regime, provided that suitable sediments are available. Off the the species may be found, singly or mixed. Turtle grass is the unquestionable dominorthwest coast of Cuba, Buesa (1975) re- nant in nost areas, however, freauently ported maxiisurn depths for tropical sea forming extensive meadows that stretch for rasses as follows: turtle grass, 14 m tens of kilometers. A1 though the absolute 446 ft); manatee grass, 16.5 m (54 ft); depth limit of the species is deeper, I-(alophilia deci iens, 24.3 m (80 ft); and mature ~rleadows of turtle grass are not - ti. enslemanni - 1 4 rn (47 ft). As plant found below 10 to 12 R (33 to 35, ft). At species grow deeper, the qua1 ity and quan- this depth manatee grass replaces turtle tity of light changes. In clear tropical grass and forms meadows down to 15 m (50 water such as that near St. Croix, Cuba, ft). Past the maxinum depth for manatee and portions of southern waters, the 1 ight grass development, shoal grass will often is relatively enriched in blue wavelengths occur, hut it rarely develops extensively. with depth, By comparison, in highly tur- Past the point at which the raajor species bid conditions as in shallow bays in Texas occur, fine carpets of Halophila extend and in Florida Ray, blue 1 ight is scat- deeper than 40 m (130 ft). tered and the enrichment is in the direction of the green wavelenpths. In hoth Numerous studies confirmed the patclear and turbid waters the longer red tern described above, or some portion of wavelengths are ahsorbed in the first few it. The relative abundance of four spencters of the water colunn. cies of seagrasses off northwest Cuba, is graphed in Figure 8 (Ruesa 1374, 1975). Ruesa (1575) studied the effects of - Halophila decipiens was the least abundant specific wavelengths on photosynthesis of with a mean densi t.y of 0.14 g/~2. Halopturtle grass and rnanatee grass in Cuba. hila aelmanni showed a mean density of Ile found that turtle grass responded best to the red portion of the spectrum (620 g/m?=atee grass was nearly 10 times denser than Halophila with an avernanorrletcrs); the blue portion (400 nanome- age density of 3.5 g/m2 down to 16.5 t" (54 ters) was better for manatee grass. ft). Turtle grass was the vost abundant seagrass, accoi~nti ng for nearly 07.52 of the total seaqrass biomass, with an aver- 2.3 ZONATION age of 190 q/17j down to its maximum depth of 14 m (46 ft). This area is unique in Although seagrasses have been re- that there is 1 ittle or no shoal grass corded fran as deep as 42 rn (138 ft), ex- which normal ly is eitber the second or tensive develop~nent of seagrass beds is third most abundant species in a region. confined to depths of LO to 15 m (33 to 49 ft) or less. Principal factors determin- In St. Croix, turtle grass had the lng seagrass distribution are light and shallowest range, occurring down to 12 m pressure at depth, and exposure at the (39 ft) on the west side of Ruck Island shallow end of the gradient. A general (Uiginton and McP"i1len 1970). Shoal grass pattern of seagrass distribution in ct ear and manatee grass showed progressively waters of south Florida and the Caribbean greater depth, occurring to 18 m (53 ft) uas presented by Ferguson et 31. (1980). and 20 n (65 ft), respectively, while Shoal grass usually grows in the shallow- Halo hila decipiens occurred to 42 m (13% est water and tolerates exposure better & species were found in less than other species. The relatively high than 1 m (3.3 ft) of water in St. Croix. flexibility of its leaves allows it to confons to the damp sediment surface dur- Because of the variety of rocky and ing periods of exposure, thus minimizing sedimentary patterns in the lagoons and 18
Page 1 and 2: F WS/O&S-82/25 September 1882 Repri
Page 3 and 4: 1 DISCLAIMER The findings in this r
Page 6 and 7: CONTENTS (continued ) Page CHAPTER
Page 8 and 9: TABLES Number Temperature, salinity
Page 10: CHAPTER 1 INTRODUCTION 1.1 SEAGRASS
Page 15 and 16: Key Went St Pstarobur~ Cedor Key Pa
Page 17 and 18: (4) The ability to complete their s
Page 19 and 20: in disturbed areas, and in areas wh
Page 21 and 22: AVERAGE LEAF WIDTH I DISTANCE BETWE
Page 23 and 24: grass, and shoal grass in various 1
Page 25: Sediment Elevation (c m) Leaf Densi
Page 29 and 30: CHAPTER 3 PRODUCTION ECOLOGY The de
Page 31 and 32: 1 isl;s conpdratiue Piorrlass value
Page 34 and 35: Net production measurements for ~10
Page 36 and 37: of seagrasses was bicarbonate ion,
Page 38: Currently the main 1 imitations of
Page 42 and 43: CHAPTER 4 THE SEAGRASS SYSTEN 4.1 F
Page 44 and 45: Figure 9. B1 owout disturbance and
Page 46 and 47: Keys waters. Where the continental
Page 48: 4.5 STRUCTURAL AND PROCESS SUCCESSI
Page 51: theft- h~ldfas t. Prirqary strbstrd
Page 54 and 55: Figure 15. Tha1 assia blades showin
Page 58 and 59: Fish I] lnver tebrates HEAVY THIN S
Page 61 and 62: Figure 19. Small grouper (Serranida
Page 63 and 64: 81 though crocodiles undoubted1 y f
Page 66 and 67: CHAPTER 6 TROPHIC RELATIONSHIPS IN
Page 68: I\iumcrous fishes ingest sor:e plan
Page 73 and 74: Table 1C. Continued. tlerbi vore Pa
Page 76 and 77:
The herbivory of parrotfish and sea
Page 78 and 79:
1 eaves pl us their epiphytes avera
Page 80 and 81:
the rate of biological breakdown of
Page 82 and 83:
Chemical Changes During Decompositi
Page 84:
CHAPTER 7 INTERFACES WITH OTHER SYS
Page 87 and 88:
Use of adjacent grass and sand flat
Page 89 and 90:
etained in the bed to contribute to
Page 91 and 92:
1972). Sinilar habitat use by juven
Page 93 and 94:
CHAPTER 8 HUMAN IMPACTS AND APPLIED
Page 95 and 96:
Taylor and Sa1 oqan (1968) contrast
Page 97 and 98:
on the &ach (Radeau and Rerquisrt.
Page 99 and 100:
the closed systerq, however. Thorha
Page 101 and 102:
1981. The pit was created over 30 y
Page 103 and 104:
with over 70% of gulf recreational
Page 105 and 106:
~bb~tt, #.P,, 3.C. Ogden, and 1.A.
Page 107 and 108:
higher consumers in a seagrass com-
Page 109 and 110:
shrimps (3ecapoda: Palaelqonidae).
Page 111 and 112:
Ehrl ich, P.R., and A.H. Ehrl ich.
Page 113 and 114:
Caribb. Res, Inst. t8ater Pollaat.
Page 116 and 117:
crustaceans. Rec. Oceanogr. Uks., i
Page 118 and 119:
tlayer, A.G. 1918. Toxic effects du
Page 120 and 121:
Apalachicol a Bay, Florida US4. Gio
Page 122 and 123:
antillarum Phil ippi : Formation of
Page 124 and 125:
Prachaska, F. J., and 9.C. Cato. 19
Page 126 and 127:
Sims, H.W., Jr., and R.M. Ingle. 19
Page 128 and 129:
of know1 edge and research needs. P
Page 131 and 132:
Wood, E.J.F., and J.C. Zieman. 1969
Page 133 and 134:
APPEMDI X KEY TO FISH SUPVEYS IN S0
Page 135 and 136:
L n 'u m (U m 'r .r > FVIL (U > El-
Page 137 and 138:
"l .^ -00 "l Q W O Z& n 0 "l m c 0,
Page 140:
... m h LI L Cn dC 3 Yu O 0 0 ox .-
Page 144 and 145:
List of fishes and their diets from
Page 146:
List of gishes and their diets from
Page 149 and 150:
LO) L O)= a, Oi D L & WOC C .- s g'
Page 152:
--C) h W wcn Old
Page 155 and 156:
C C +m" CX r .-- a * 'PI C7 C T 4 b
Page 160:
-. "-1 --- --- -- - ---- -- - - - .
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