SEAGRASS INQUIRY

jbeckert at sallie.wellesley.edu jbeckert at sallie.wellesley.edu
Wed Oct 23 08:33:19 EST 1996


Does anyone out there work with seagrasses?  I am in
immediate need of some information...

I understand Zostera marina has two forms, annual and
perennial.   I have read that the annual type is found largely
in areas subject to ice scouring in the winter, and that the
perennial form is generally found in deeper waters less
likely to be disturbed by ice.

If this is so, how does seed output of the perennials compare
to that of the annuals?  Are seeds able to germinate and
seedlings grow amid the dense rhizomes of the perennials?
How genetically diverse is the average patch of perennials?
Are Zostera seeds dormant over winter, germinating in the
spring?

Do the annual types also grow clonally, or does this form of
growth require more than a single season?

I have read conflicting ideas on whether or not the two
forms are genetically different.  Have any recent studies
been made on this?

I have also read that Z. marina seeds do not usually disperse
more than a few meters from the parent plants.  I am
puzzled -- what could be the strategy of such a dispersal
system?    Are enough seeds carried off on detached
reproductive structures to disperse the seeds effectively?
Are there seed predators, and do they take a significant
part of the seed crop?

ALSO -- I would like to know whether any of the tropical
seagrasses exhibit similar annual/perennial differences.  If
so, is this also related to disturbance (e.g., storm damage?)?
Do the tropical species customarily grow in deeper water
than the temperate, perhaps because of greater water
clarity?  Are they also clonal?

What is the situation on seed production and dispersal in
the tropical species?

I would *greatly* appreciate any information anyone might
be able to give me, and/or any suggestions of primary
literature relating to any of these questions.  Please
respond directly to me at JBECKERT at LUCY.WELLESLEY.EDU

Thank you very much!!

Jan Beckert



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