Hi Art.
While I have given my copy to my aspiring oceanographer son and can't
give you a perfect reference, I'll refer you to a discrete chapter in
Joel Hedgepeth [ed.], 1957(?). Treatise on Marine Ecology and
Paleoecology. Vol.1, Ecology. Memoirs of the Geological Society of
America. >1,000p.
The questions and discussions on conch-l suggest that you and others
are fairly unfamiliar with this well-studied, and
taxonomically-well-defined ecosystem.
This chapter (I've forgotten the author's name) is one of the
classical descriptions of the pelagic Sargassum ecosystem. Here,
Sargassum ("Gulf weed") plays a role as a dominant plant genus (two
main species in the Atlantic; S. natans, S. fluitans) supporting a
predictable assemblage of invertebrates and fishes. Sargassum is a
floating brown macroalga (phaeophycophyta) and has nothing whatever to
do with the microscopic dinoflagellates that can bloom in coastal
waters, killing fishes.
Sargassum is rather analagous to seagrass beds and mangrove forests
that support their own associated fauna and flora. Among the dominant
animals in the Sargassum community are shrimps, a portinid crab,
amphipods, attached bryozoans and hydroids, juvenile sea turtles,
snails, and fishes. In some ways the brown alga serves as a "benthic"
substrate in an otherwise pelagic environment.
The Sargassum Sea is a fuzzily-delimited region in the anticyclonic
gyre in the North Atlantic, the western boundary of which coincides
with the Florida Current and the Gulf Stream. The main
characteristics of the "Sea" is its relative self containment and
isolation, low planktonic productivity and incredibly clear,
cobalt-blue water (among the clearest in the world -- you can see a
dime thrown overboard forever, it seems.) Salinity and temperature are
pretty normal for the pelagic environment and they're definitely
non-problems and not limiting factors in themselves. The floating
Sargassun serves as a sort of oasis of life in a biological desert.
For this reason, there are a number of questions regarding the flow of
energy, nutrients, carbon, and nitrogen into, passed through, and
exported out of the system. We do know that the Sargassum that dies
and finally sinks into the deep sea can provide a significant source
of energy to places like the Hatteras Abyssal Plain in about 5,000m of
water.
During storms, and through the action of certain spin-off eddies, lots
of Sargassum can be entrained into shallow continental shelf habitats
and then found stranded on the beach. There are few better ways of
teaching kids neat biology than letting them sort through fresh
seaweed for living critters.
Also try looking up "Sargassum" on the net.
Robert M. Avent
Oceanographer
Minerals Management Service
New Orleans, LA
504-736-2899
ps
Oh -- and there's absolutely nothing to the "Bermuda Triangle" that
can't be attributed to natural phenomena and local conditions. There
are no really unusual magnetic anomalies, ancient cities, sea monsters
or little green alien dudes. Sorry, shellers.
Bob
______________________________ Reply Separator _________________________________
Subject: More on Sargasso Sea -Reply
Author: MR ART WEIL <[log in to unmask]> at ~smtp
Date: 5/21/98 9:52 PM
Paul;-
That's a very fine answer about Sargassum and Red Tide. Is the red
algae poisonous to mollusks that injest it? Again, is the sargassum
home to small shrimp and crabs? Does the sargassum itself act as a
buffer to waves and movement or does it just exist in this quiet zone?
Are there other such zones in other oceans similar to this?
Art
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