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

I\iumcrous fishes ingest sor:e plant
material, while relatively fev~ of these
species are strict herbivores ; exceptions
are the Scarids and Acanthurids already
l~lentioned. flost plant and detri tal rnaterial
is probably taken incidentally while
feedin9 on other organisrqs. Ortkopristis -
chrysoptera and Lagodon rko~rlboides are two
very amant grass bed fishes in south
Fl or i da and apparently during sone feeding
stages are oliini vores, ingesting subs tantial
arnounts of epiphytes, detritus and
seagrass (Carr and Adam 1373; Adams
1?76a, 1976b; Kinch 1979). Other o~iinivores
include some filefishes, porgies, blennies,
and gobies.
Gastropods are fed upon by a variety
of fishes including wrasses, porcupine
fishes, eagle rays, and the perr~ii t Trach-
- ~iotus ---- folcatus. Randall (1367) 1 istedx
species of fishes that feed on gastropods,
25 ingesting 10% or nore hy volume. !lost
sl~ecies crush the shell while ingesting,
but s few swallow the gastropod whole.
The white grunt (Hacoulon pluveri ) appears
to snap off the extended head of Ceri thiurri
ignoring the shell. Thc southern
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stingray (Dasyatus arnericana) has been
observed turninq over the queen conch
(Strombus --- jigas) and wrenching off the
conch's extended foot with its .iaws as
the conctl tries to right itself -(~andal
1964). The spiny lobster (Panul irus
argus) is an active predator on seagrass
1:1oll USCS.
epifauna, the ir~gact of blue crab predation
may be greatest on epibenttric
fauna.
The majority of fishes within the
grass bed feeds on small, ~~obile epifauna
including copepods, cuwaceans, anphi pods,
isopods, and shrimp. Fishes feeding in
this manner include all the seasonally
resident fishes of the south Fl widd crass
beds, such as the Sci aenids, Pomadasyids,
Lutjanids, and Gerrids, as well as oany of
the permanent residents, 1 i ke Syngnathids,
and Clinids. As such, they are deriving
!nuch of their nutrition indirectly from
seagrass epiphytes and the detri ta1 com-
~iiunity present in the grass bed rather
than the grasses themselves. Many of these
fishes, as adults, will feed on other
fishes ; however, as juvenile reside~ts in
the grass beds, their srqall size limits
the^:^ to eating epifauna.
Important piscivores are present in
south Florida qrass flats. These include
the lenon shark
6.2 DIRECT HERBIVORY
The southern stingray and the spotted Caribbean grass beds may be unique
eagle ray (Aetobatis -- narinari) art. two of for the numbers and variety of direct cona
relatively few number of fishes that surners of blade tissue (Ogden 1980) as
feed on infauna withjn the grass bed. relatively feld species ingest greefl sea-
These fishes excavate the sediments. grass in significant quantities (Table
Other similar feeders are wrasses, goat- 10). Prominent herbivores include urchins,
fishes, and mojarras. Adult yellowtail conch, fishes, as well as the green tursnapper
(Oryhurus chrysurus) have been ob- tle, Chcl onia mydas, and Caribbean manatee
served foraging in bac-f seagrass sed- (Tric-anatus). -- The elucidation of
iments (Zieman, personal observation). the role of direct herbivory as a pathway
That the infauna is not heavily preyed of energy flow in seagrasses has been
upon is typical of seagrass beds (Kikuchi
1974, 1980). Apparently the protection
slow in developing. Until recently, it
was assumed that few organisms consumed
fro~tl predation afforded the i nfauna of
grass beds is great enough that few fishes
seagrasses directly, and that herbivory
had substantially decreased with the
specialize on infauna wheri feeding (Orth decline of the ~o~ulations of the green
1977b). The blue crab (Callinectes sea turtle. Direct grazing of seaqrasses
sapidus) has been observed toyhift its in south Florida is prohaSly of greatest
feeding froin Zostera infauna to epibiota importance in the grass beds of the Florand
thus, because of the protective rhizone
layer and the accessibility of the
ida Keys and outer margin of Florida Bay
which are relatively Close to coral reefs.
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