[NatureNS] here's a fellow who's working on the effects of ditching on salt

Date: Wed, 03 Apr 2013 15:56:02 -0400
From: Fred Schueler <bckcdb@istar.ca>
Cc: Naomi Langlois-Anderson <nlanglois-anderson@nation.on.ca>,
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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...


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
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
     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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