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

are present hecause of its abi l i ty to to1 -
erate aerobic, unstablc sedirqents and to
rapldfy extend its rhizorse systen under
these conditions. This is especially cvident
in back-reef areas, Patriquin (19753
attributes the persistence OF nana tcc
grass in areas around Barbados to recurrent
erosion in areas where the hottom was
never stable for a sufficiently long tine
to allow turtle grass to colonize. Manatee
grass can have half of its biomass as
leaves (Table 4). Thus, while manatee
grass is col onizing aerobic disturbed sedinrents,
vihlch would he areas of low nutricr'lt
supply and regeneration, the arqount of
its root surface available f ~ nutrient r
0pt.a ke woul d he reclucetl , and correspatldingly
ltldfp uptakc would become a major
source of nutrients, If this is the case,
thc higher agitdtfon of the wdter column
would be of benefit l-ty reducl'ng the gradients
at the leaf surfacc.
4.4 THE CENTQAL POSITION OF THE SEA-
GRASSES TO TMt SEAGRASS ECOSYSTEM
orgaili sirrs t~i th their widely di fferincr
requirements and interactions functioned
as a hi9hly intricate v~eh structure that
made each individual or each link less
necessary to the maintenance of the total
system. There was mttch natural redundance
bull t into the system. For certain segr~ents
of the co~qrjunity this may be true.
The problem is that at cl irnax there is one
species for vrhich there is no redundaricy :
the seagrass. I0 some cases, if the seagrass
disappears, the entire associated
co~muni ty disappears along with it; there
is no other orgavlisri that can sustain arid
support the systen.
This is shown in a sr~all way when
mi nor di s turbanees occur as was described
v ~ th i the hlowouts. As the yass beds in
these areas are eroded away, the entire
seaqrass systcrn disappears, including the
top 1 or 2 $4 of sediinent. These features
are siilall and readily repaired, hut give
an indication uf whdt cotild happen if
there was widespread danage to the scagrasses.
Seagrasses are vital to the coastal The largest cnntribut.ion to the diccosyste~i
because they fann the &sf'; of a versity of the systt?~: is cornr~only nade by
three-dirilertsionali , structural ly complex the conpl ex cominrnni ties that are epiphytic
halri tat, In inodern ecology there has heen on tho scaqrass leave?. defol iation
a shfft Frorn the autwecolo~~ica'l, approach of the seagrasses occurs, most of this
of studylng irrdividual specics ir~dcpcnd- cctnl~runity disappears, either by being care?t~tly,
to the corl~iuni ty or ecosystci:~ ap- ried out as drifting leaves or becoming
groach where the focus is the l argsr i rite- part of the 1 i tter 1 ayer and ul tirnit tel y
yvcrted cnti ty. Uith that real ization, one the surface sediments. Rith the leaves
caul$ wonder, "Why spend s8 riuch effort on gone, the current baffling effect is lost
a Few ~peciefi of' rnarine plants, evctlr if and the! sedirnent surface hegins to erode.
tiley are the most abundant, in a system A1;:al nats that nay fom have minimal
that hds thousands of other species?'The stabilizing abi 1 ity; however, the dead
rrrinsan is that these pldnts are critical rhizonws and [%its will continue to bond
ta crast other species nf the system, both the sedirnerlts, it1 some cases for several
plant and animal. There are Feu other years (Patriqtdin 1375; Scoffin 1970).
systerqs which dre so doiqinated and controlled
by a single species as in the case
In south Florida the disappearance of
of a cl inax turtle grass or Tostera mca- seagrasses would yield a far different
dow. H.T, Odurrl (1974) class~?~~-~urtle seascape. ?!uch of the region would be
grass beds as '"natural tropical ecosystens shifting mud and mud banks, while in [?any
with high diversity.'Vaken as a total areas the sediments would be eroded to
r;ystc~*r, tropical seayrass beds are regions bedrock. Based on the communities found
of very hTgR aiversity, brit this cdn be fri such ariras tod?ry, primary prodttctiet:
c:?isleaditrg. Conparisans betueen tropical and detri tal product ion would be dramatiand
ternperate systems were made at a time cally decreased to the point that the
when hl'gh diversity was equated with high support base for the abundant co~nr~ercial
biological stability. The prevail iny can- fisheries and sport fisheries would shrink
cept was that the multitude of different if not disappear.
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