Given that seagrasses
are vascular plants, should they be capable of colonizing sediments
in area of moderate wave and current energy?
Seagrasses can propagate
using rhizomes (but also sexually involve
underwater pollenation).
Both the leaves and
rhizomes can absorb nutrients directly. The aquatic medium has
eliminated the need for a fibrous support system as found in
terrestrial plants and flexibility allow seagrasses to withstand wave
action.
Most seagrass
are rooted below the level of low tide. What effect does water clarity have on
seagrasses, and seagrasses on water clarity?
The stabilizing effects of
seagrasses on bottom sediment promotes the establishment of macroalgae
and infaunal invertebrates. How
would the physical structure of seagrasses affect the exchange of
planktonic larvae and detritus from the water column?
Food
webs and energy flow in seagrass ecosystems
Seagrass
systems are highly
productive (both primary and secondary), yet there are limited
number of consumer species that include seagrasses as a major part of
their diet (sea turtles, manatee, geese, some urchins, some fish, some
amphipods...). The reason is that seagrasses are
fiberous and contain compounds that are difficult to metabolize
(especially phenolic compounds that may act as
an anti-fouling defense).
How
can secondary production (i.e.
consumer production) be high if few species are consuming seagrass
tissue?
Seagrass epiphytesmay
contribute more than one-third to the total above ground
biomass and 30% to
combined seagrass/epiphyte productivity. Epiphytes
appear to provide a more assimilable food source
for animals such as snails that were previously assumed to be
'detritivores'.
So, what would a food web/energy
diagram look like for a seagrass ecosystem?
Ecology of seagrass
ecosystems
Epiphytes are not
only important in channeling energy to higher trophic
levels, but also have negative effects on seagrasses (how?). Experimental exclusion
of epiphyte grazers can
reduce seagrass growth rates.
Strong zonation with depth suggests that competition
among seagrass species may be important, and horizontal distribution
may possibly be mediated by
differential abilities to acquire nutrients. Macroalgae (such as Caulerpa
taxifolia) are associated with seagrass die-back, possibly as
a result of interference competition via the production of toxic
secondary metabolites.
The primary threat
to seagrass ecosystems in loss of water clarity by inorganic
sediment inputs and by nutrient loading (www.icef.eawag.ch/abstracts/short.pdf).
Most seagrass
are rooted below the level of low tide. What effect does water clarity have on
seagrasses, and seagrasses on water clarity?
