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Quoting David & Alison Webster <dwebster@glinx.com>:
> Hi Fred & All, Apr 3, 2013
> Very interesting, especially the bit about the alien crab having
> a beneficial effect and the Green Crab destroying Spartina beds. But
> what does ditching have to do with this ? Just exposing more area to
> erosion or something else ?
* no, it's the Green Crab that's increasing as an invasive, and
reducing the population of the native Sesarma reticulatum (according
to wikipedia not found north of Massachusetts) which had expanded as a
result of reduced predation on it when sport fishing reduced Striped
Bass and other piscine predators.
The ditching seems just to have increased the edge of the Spartina
sod, and enhanced the erosion resulting from the Crabs' herbivory.
I wonder if the Sesarma reticulatum are heading north as a result of warming?
fred.
========================================================
> Yt, Dave Webster, Kentville
> ----- Original Message ----- From: "Fred Schueler" <bckcdb@istar.ca>
> To: <NATURENB@LISTSERV.UNB.CA>; <naturens@chebucto.ns.ca>
> Cc: "Naomi Langlois-Anderson" <nlanglois-anderson@nation.on.ca>;
> "Owen Clarkin" <wrecsvp@gmail.com>
> Sent: Wednesday, April 03, 2013 4:56 PM
> Subject: [NatureNS] here's a fellow who's working on the effects of
> ditching on salt marshes
>
>
>> 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/
>> ------------------------------------------------------------
>>
>>
>>
>> -----
>> No virus found in this message.
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>>
>
>
------------------------------------------------------------
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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