Salt Marsh Mitigation in Connecticut

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Salt Marsh Mitigation in Connecticut
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Typical salt marsh zonation in Connecticut
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Tidal gates on Sybil Creek
Mosquito ditching
Some human impacts on salt marshes in Connecticut
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Phragmites - invasive sp.
Development
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Filling in salt marshes
Other notable impacts undersized culverts
beneath roads/bridges pollution in Long Island
Sound tidal mill ponds (historical impact)
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Tidal Wetlands Act, 1969 - Sec. 22a-28
Preservation of tidal wetlands. Declaration of
policy. It is declared that much of the wetlands
of this state has been lost or despoiled by
unregulated dredging, dumping, filling and like
activities and the remaining wetlands of this
state are all in jeopardy of being lost or
despoiled by these and other activities, that
such loss of despoliation will adversely affect,
if not entirely eliminate, the value of such
wetlands as sources of nutrients to finfish,
crustacea and shellfish of significant economic
value that such loss or despoliation will
destroy such wetlands as habitats for plants and
animals of significant economic value and will
eliminate or substantially reduce marine
commerce, recreation and aesthetic enjoyment and
that such loss or despoliation will, in most
cases, disturb the natural ability of tidal
wetlands to reduce flood damage and adversely
affect the public health and welfare that such
loss or despoliation will substantially reduce
the capacity of such wetlands to absorb silt and
will thus result in the increased silting of
channels and harbor areas to the detriment of
free navigation. Therefore, it is declared to be
the public policy of this state to preserve the
wetlands and to prevent the despoliation and
destruction thereof.
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Salt Marsh restoration in Connecticut - 1980,
DEP Office of Long Island Sound Programs
involved in restoration - uses federal
transportation funding - impacts of road/bridge
construction - 1700 acres restored -
increase coastal water productivity - increase
fish production - enhanced use by herons,
shorebirds, waterfowl - reduced
mosquito-breeding areas - lessened fire hazards
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Some agencies involved in restoration -
Connecticut Department of Environmental
Protection - Iroquois Gas Transmission
System - Ducks Unlimited - The Stewart B.
McKinney National Wildlife Refuge - U.S. Fish
and Wildlife Service - local government -
Audubon Society - The Nature Conservancy
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Restoration might consist of - Phragmites
australis removal (reed tolerant of low
salinities (lt 18 ppt) other invasives (Purple
loosestrife, Typha) - plugging old grid ditches
(former mosquito control), clearing natural
channels - removing old impoundments -
Integrated Marsh Management (creation of new
ponds, channels, salt pannes) - sediment
removal sediment sources - stormwater
discharge - dredged navigational
channels - recreational marinas - culvert and
flood gate modifications
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• RESTORATION RULES OF THUMB 
• re-establishment of regular tidal flushing with
• saltwater (over 18 parts per thousand of salt)?
• replacement of Phragmites by salt marsh plants
• - conversion normally occurs over a 5-10 yr
• period.
• re-establishment of salt marsh plants proceeds
• spontaneously if a nearby salt marsh is present
  to
• supply a seed source.
• - In most cases expensive planting or
• transplanting programs are not necessary.
• restoration of tidal flows to their
  pre-disturbance
• volumes is not always desirable, especially in
  the
• case of subsided wetlands.
• - restoration reduces or eliminates mosquito
  breeding
• in subsided marshes.
• - restoration re-establishes scenic vistas.

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Restoration at Long Beach, Stratford, Ct. Steward
B. McKinney National Wildlife Refuge
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How do you determine success?
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Bioassessments - Biological integrity ability
to support and maintain balanced, integrated,
adaptive community of organisms having a
species composition, diversity, functional
organization comparable to those of natural
habitats within the region - use index of
biological integrity - metrics combination
of - native plant cover - algae -
amphibians - birds - macroinvertebrates
- fish Functional assessments estimate
functions e.g. water storage, nutrient cycling
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Approaches and methods of tidal restoration at 57
Connecticut DEP sponsored or permitted projects
between 1975 and 1999.
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Table 1. Salt marsh tidal restoration sites
included in this study
Study sites
Warren et al. 2002. Salt marsh restoration in
Connecticut 20 years of science and
management. Restoration Ecology 10497-513
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Recovery of salt marsh vegetation after tidal
restoration measured as the loss of Phragmites
cover up to 1995, the latest complete false color
infrared air photo set available.
Dominance by Phragmites decreases
following tidal restoration.
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Figure 2. (A) Mean percent cover and frequency
of occurrence of Spartina alterniflora (Sa) and
Phragmites australis (Pa) along three Mumford
Cove transects sampled in 1992 and 1997, 2 and 7
years after restoration. Cover (Tukey's test pgt
0.05) and frequency (chi-square pgt 0.05)
increased for Sa but not for Pa. (B) Mean
elevations (datum 1992 local mean lower low
water) of points along three Mumford Cove
transects sampled in 1992 and 1997 that
supported (cover 1) Sa and Pa and points that
were essentially free of these species (cover lt
1).
Spartina increases in percent cover and
frequency by 7 years.
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 (A) Total mean percent cover and frequency of
occurrence for all salt marsh angiosperms along
1996 restoration transects versus transect mean
salinity. Both measures increase with salinity
and regressions are significant. (B) Mean
percent cover and frequency of occurrence for
Phragmites australis along 1996 restoration
transects versus transect mean salinity. Both
measures decrease with salinity and regressions
are significant. Frequency drops sharply above
26 curve fitted by hand. (C) Mean end of
season height and stem density of Phragmites
australis at transect soil water wells (n 27).
Height drops with salinity with maximum salinity
ca. 26 curve fitted by hand. Stem density does
not correlate with salinity.
Changes in plants track salinity changes
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Figure 4. Relative abundance of Melampus
bidentatus in recovering versus reference
regions (mean density on restoration
area/associated reference marsh) of four marshes
at Barn Island in relation to the number of
years of recovery. Although these marshes differ
from one another in ways other than years of
recovery, data indicate a long trajectory for
full recovery of Melampus populations
Abundance of a salt marsh snail
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Figure 5. Relative abundance (recovering/reference
) of birds considered salt marsh specialists
(triangles) and salt marsh generalists (circles)
at two recovering Barn Island (BI) marshes
(solid) and at Mumford Cove (MC, open) plotted
against years of restoration at the time counts
were conducted. Although these marshes differ
from one another in ways other than years of
restoration, data indicate that it may take a
decade for restoration sites to support
equivalent populations of marsh specialists.
Also, marsh generalists, whose use declines over
time, rapidly occupy restoration sites.
Marsh generalists decrease, specialists
increase through time
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Mean recovery rates, seasonal soil water well and
peat salinities, and depths to water table for
the three rapidly recovering (Hammock River, Long
Cove, and Great Meadows) and two slowly
recovering (Barn Island and Great Creek) systems.
Slower recovering sites have lower salinities
and deeper depths to water table
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Mean density (no./m2 SE) of six
macroinvertebrates in recovering and reference
regions of three marshes at Barn Island,
Connecticut that have been in the process of
restoration for different periods of time.
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Fishes and crustaceans caught within mosquito
control ditches at Barn Island in the recovering
marsh (IP1) and the adjacent reference marsh (HQ)
below impoundment dike 21 years after
restoration and in recreated creeks of the
restored Mumford Cove marsh 8 years after return
of tidal flooding.
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Abundance of birds (average number of
individuals observed per visit) at the
reference marsh, HQ, and the restoration marshes
, IP1, IP3 sites at Barn Island and the MC
Marsh during surveys conducted in the summers
of 1994, 1995 and 1999.
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• Results
• Restoration of tidal flow initiated decline in
• Phragmites and Typha ? re-establishment of tidal
  salt
• marsh species
• - some sites had rapid recover, others slow
• - important influences
• - salinity hydroperiod (major factor)
• - slow sites had reduced
• hydroperiods due to
• flooding frequency
• constraints
• -gt altered chemistry

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• Some salt marsh macroinvertebrates were
• present in lt 5 years others might require
• several decades for establishment
• Characteristic fish species might return early in
• restoration (8-13 years) many might require
  a
• longer period of time to achieve population
  sizes
• characteristic of reference salt marshes.
• - diets appeared similar between restored and
• reference sites, though quantity
• of food (gut contents) differed.

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• Marsh generalists birds were present 4-5 years
• following restoration (increased abundance
• diversity).
• - 10 years, Marsh specialists were present,
• but less abundant than generalists.
• - Specialists increase through time..

5. Species have different and often independent
recovery rates.
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• Take-home message
• With appropriate substrate, hydrology, propagules
• in vicinity ? functioning salt marshes can
  develop,
• in time
• - reestablishing tidal connections are key.
• - final equilibrium conditions often
• unrealistic goal.
• best to start trajectory,
• recognize it might take
• decades to attain marsh
• with conditions similar
• to reference sites