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http://www.bertnesslab.com/html/people/Tyler.html - "Historically,
salt marshes were thought to be controlled almost exclusively by
bottom-up forces like temperature, salinity and nutrient availability.
Over the past several decades, however, human impacts, like top
predator depletion and eutrophication have shifted salt marshes to
systems with strong top-down consumer control across the western
Atlantic from the Canadian subarctic to South America. We have
experimentally examined this shift in the control of salt marsh
ecosystems in North and South America. Most recently we have focused a
great deal of our attention on the consumer-driven die-off of marshes
on Cape Cod and Long Island Sound that we have established is the
consequence of intensive recreational fishing targeting top predators,
depleting predator stocks near heavy recreational fishing areas,
releasing the herbivorous crab, Sesarma reticulatum, from consumer
control and triggering regional die-off of marshes associated with
heavy recreational fishing.
"This work challenges both the notion that marshes are under strong
bottom-up control and that recreational fishing is an ecologically
benign activity. We are continuing this work by following the spread
of Sesarma-driven die-off into Long Island Sound, critically examining
if the southern spread of Sesarma-driven die-off is also being
triggered by recreational fishing pressure. We are also examining
mechanisms of marsh resilience and recovery in marshes abandoned by
Sesarma since the cordgrass food supply has been entirely depleted,
and we are beginning to explore consequences of predator depletion in
other soft sediment habitats where their impact may be just as great,
but less conspicuous."
I don't know how relevant this might be to NS & NB marshes, but it's
something to think about, especially a new paper which suggests that a
trophic cascade from alien Green Crabs feeding on the herbivorous
crab, Sesarma reticulatum, may promote recovery of marshes...
http://www.conservationmagazine.org/2013/04/welcome-visitors/
Invasive species are usually the bad guys in conservation. But an
invasive crab is helping to restore salt marshes on Cape Cod by
forcing out more destructive crabs, a new Ecology study suggests.
Along the New England coast, fishing has left many marshes bereft of
predatory animals. As a result, marsh crabs that would otherwise have
been eaten by the predators have multiplied. The marsh crabs have
gobbled Spartina cordgrass along creek banks, making the land erode
more easily. (DOI link at end of article isn't functional, paper is
not open access)
thanks to -
Pamela Zevit, R.P. Bio
Adamah Consultants
Coquitlam BC Canada
604-939-0523
adamah@telus.net
Re-connecting People & Nature
Science World - Science in the Classroom Ambassador
------------------------------------------------------------
Frederick W. Schueler & Aleta Karstad
Bishops Mills Natural History Centre - http://pinicola.ca/bmnhc.htm
Mudpuppy Night in Oxford Mills - http://pinicola.ca/mudpup1.htm
Daily Paintings - http://karstaddailypaintings.blogspot.com/
South Nation Basin Art & Science Book
http://pinicola.ca/books/SNR_book.htm
RR#2 Bishops Mills, Ontario, Canada K0G 1T0
on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
(613)258-3107 <bckcdb at istar.ca> http://pinicola.ca/
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