Coastal_WP - ASP

lovinggudgeonMécanique

22 févr. 2014 (il y a 3 années et 3 mois)

61 vue(s)


C
OASTAL ZONE IMPACTS
ON GLOBAL BIOGEOCHEM
ISTRY
:


T
OPIC
#

1:

H
OW DO DIFFERENT COAS
TAL ZONES IMPACT THE

CARBON CYCLE
?


C
ONTRIBUTED BY
:

I.

F
ALOONA
,

T.

L
UEKER
,

S.

N
ANDI
,

R.

S
HIPE
,

D.

V
ARELA
,

L.V
ER


General Information




Identification of importance of coastal

zones by two main carbon cycle documents:



North American Carbon Plan (NACP) and the Ocean Carbon & Climate




Change (OCCC).



Ship
-
based studies in the East China Sea [Tsunogai et al., 1999] and off the West
Coast of Europe [Frankignoulle et al., 2001
] have suggested that the coastal ocean
plays a significant role in the global carbon cycle (Frankignoulle et al. estimate the
European coastal sink to be almost half as large as that proposed for the open North
Atlantic).



1.
Nitrogen cycle




Riverin
e inputs are on par with wet deposition & in
-
situ fixation


Benthic denitrification in CZ is dominant removal of bioavailable N


There is a tight coupling between the cycles of C and N (and Si) during massive



blooms and export events.


2.
Other nutr
ient cycles




S


DIC


P


Fe: Synoptic scale transport to and fertilization of open ocean


Si: Under eutrophic conditions, the coastal phytoplankton community



is dominated by diatoms. These unicellular protists require Si for



growth (C:Si ~ 106:1
6)


3.
Physical forcing/hydrological cycle




Coastal upwelling, synoptic semi permanent H pressure, Ekman pumping


Boundary currents (great distinction between Eastern/Western) &





corresponding eddy transport processes


Influence of large
-
scale cli
mate oscillations such as ENSO, NAO, etc.


Increase in stratification of coastal waters thought to affect nutrient abundance



and supply to mixed layer (in Gulf of Alaska study)


4.
Important regions




Upwelling regions (N. California Coast, and simil
ar regions in S. Pacific,




S. Atlantic): responsible for ~50% of world’s fish catch


Deepwater delivers large pCO2 (source) as well as nutrients which





instigate large biological blooms (sinks)


Main riverine discharge regions (mostly NH: Amazon, O
rinoco, Congo,




Yangtse, etc.)


Transition region between pelagic and coastal environments (e.g., utilization of



NO3 by small autotrophic flagellates vs. diatoms)



5.
Methods for constraining


Coastal zone color scanner (for NPP)


Coastal CO2 flux
monitoring network


In
-
situ monitoring experiments such as the NEPTUNE and VENUS projects on



the coastal NE Pacific


Low altitude airborne spectral methods


optimization of satellites





(MODIS, SeaWiFS) for high turbidity of CZs


Atmospheric monitor
ing of other trace gases (O2, N2O, CO) at coastal time



series stations


Long
-
term monitoring of C sequestration needs to work towards constraining



lateral advection


6.
Uncertainty / big questions


Upwelling CO2 rich deepwater vs. biological drawdow
n


who wins?


Pronounced heterogeneity of biological response to distribution of





chemical properties (nutrients)


need for better food web characterization



How do the controls on productivity/sequestration coupling (see (7)) vary




geographical
ly, seasonally, and climatically?


Sensitivity to large scale climate oscillations


Strive for sufficient understanding of these processes to allow for





intentional climate manipulation


7.
Sedimentation / carbon sequestration rate




14
-
30% of ocean
ic NPP (~103 Pg C y
-
1) concentrated in CZs


Estimates as large as 50% of total bio pump is “continental shelf pump”


To what extent do nutrient supply and offshore eddy transport control the C



sedimentation rates? More generally, what are the physical,

chemical, and


biological controls on the productivity/sequestration coupling?



8.
Upwelling areas and air
-
sea fluxes



Possibility of differing air
-
sea exchange parameters due to: presence of




surfactants, shelf induced turbulent transport, lim
ited fetch, etc.


[Also see (3) & (4) above]

C
OASTAL ZONE IMPACTS
ON GLOBAL BIOGEOCHEM
ISTRY
:


T
OPIC
#

2:

H
OW DO COASTAL ZONES
IMPACT ATMOSPHERIC C
HEMISTRY
,

INCLUDING
AEROSOLS
?


C
ONTRIBUTED BY
:

C
HRISTINE
W
IEDINMYER
,

A
DELE
C
HUCK
,

I
AN
F
ALOONA
,

T
IM
L
UEKER
,

M
ONICA
M
ADRONICH
,

K
ATHARINE
M
OORE
,

C
INDY
N
EVISON
,

M
ARK
P
OTOSNAK
,

R
OB
R
HEW
,

C
RAIG
S
TROUD
,

J
OHN
W
HITE



General Information



Figure 1: A general schematic of the atmosphere
-
coastal interactions of chemical trace
gases.




Coastal

ecosystems are characterized by higher primary productivity than open ocean
systems.




Ocean
-
atmosphere interactions within coastal zones reflect a transition from a relatively
contaminated continental land mass to a less contaminated marine air mass


TRACE

GASES

AEROSOLS




N
2
O, CH
4



Halocarbo
ns e.g.
CH
3
I,
CHBr
3



Sulphur
compound
s e.g.
DMS,
H
2
S, COS




Increased
productivi
ty



Varied
ecosyste
ms



Breaking
waves



DOM



Anoxic
zones



Eutrophi
cation



Harmful
algal
blooms



Sea
-
salt



Hal
oge
n
cycl
ing



Nit
ro
ge
n
inp
uts



Hy
dr
oc
ar
bo
ns



N
,
P
,
S
i



T
r
a
c
e
m
e
t
a
l
s

#2. How do coastal zones impact
on atmospheric chemistry?



CCN



Ozone
depleti
on



Green
house
gases

A. Chuck



Coa
stal seas are dominant marine sources of some trace gases globally e.g. nitrous oxide,
carbonyl sulphide, methane and important production sites for almost all trace gases.





1.

Hydrocarbons

a.

Macroalgae (seaweeds) have been shown to produce a variety of hal
ogenated
compounds, isoprene, and other NMHCs.



Hydrocarbons & Aerosols



The “Sea Surface Microlayer” (SSM) is often aerosolized or may coat/be associated
with your regular sea
-
salt aerosol.




Some of the organic compounds in the aerosol are bacteria or
bacteria products.
Functionalities include lipids, carbohydrates, but this is very poorly characterized.


2.

Sulfur Compounds

a.

Coastal phytoplankton species such as Phaeocystis are important producers of DMS,
although DMS production rates in coastal waters
are not particularly high compared to
open ocean areas.


b.

Coastal salt marshes have very high sulfur content in their soils, which has two major
effects in terms of trace gas exchange:

a.

First, they provide the substrate for the production of sulfur
-
containi
ng trace
gases, such as H2S, COS, MeSH, and DMS.

b.

Second, high sulfate levels inhibit methanogenesis, meaning that coastal marshes
produce very little methane relative to freshwater wetlands


c.

H
2
S and other reduced
-
S and organo
-
S species may be present in t
he gas
-
phase?



Sulfur Compounds and Aerosols

d.

DMS oxidation produces SO
2
, which ultimately can produce particles. (Probably very
important for new particle production).


e.

DMS flux measurements in ocean regions, and the DMS
-
CCN
-
cloud studies. (Studies
hav
e been performed to link DMS emissions to CCN production and cloud properties).
References?



3.

CO


a.

CO is generated in the ocean by photochemical degradation of CDOM (colored
dissolved organic matter) and its main loss is microbial consumption. Onl
y about
15% of this cycling is vented to the atmosphere, where it is believed to represent a
mere 2% of the global atmospheric CO budget [Zafiriou et al., 2003].



b.

Very few measurements of marine CO fluxes exist in coastal regions outside
of s
ome high latitude port cities.

CO production from wetlands alone may

be
as large as 300
-
400 Tg C/yr [Valentine and Zepp, 1993] which suggest considerable
potential for elevated CO emissions in estuaries and coastal waters.



4.

Nitrogen compoun
ds


a.

There is substantial evidence for organo
-
N being important (gas
-

and aerosol
-
phases) in
coastal regions, but these compounds are very poorly characterized.


b.

Nitrates may play important roles in estuaries/coastal regions as run
-
off from fertilizers.

Nitrates in aerosol may be important in perturbed coastal regions.


c.

Coastal upwelling regions are important sources of nitrous oxide (N2O). This is true for
two primary reasons. First, coastal regions have high rates of microbial N2O production
as a conse
quence of their high productivity. Second, upwelling provides an effective
pathway for ventilating N2O, which is produced primarily in subsurface waters, to the
atmosphere. Anthropogenic nitrogen inputs to coastal areas can lead to large
enhancements in co
astal N2O emissions. Although N2O is chemically inert in the
troposphere, it is a radiatively active greenhouse gas and also provides the primary
stratospheric source of NOx, an important regulator of ozone.



5.

Halogenated Compounds


a.

Very high emission rate
s of methyl halides have been observed in coastal terrestrial
ecosystems.


b.

Coastal salt marshes emit methyl halides at high rates, depending on plant species and
environmental parameters.




c.

Tropical coastal lands also emit methyl halides, also apparently

from vegetation.




d.

These coastal ecosystems are regions of high primary productivity and high halide
availability.




e.

Macroalgae are known sources of volatile organo
-
bromine and organo
-
iodine
compounds.


f.

Bromoform is the most abundant form of biogenic
reactive organic bromine and the
highest concentrations of bromoform are invariably found in coastal waters.


g.

Possibly 70% of world’s bromoform produced by macroalgae (Carpenter and Liss 2000).


h.

Macroalgae area also sources of a variety of iodinated comp
ounds e.g. CH2I2, methyl
iodide. Current understanding is that this source is not globally significant but impact on
local atmospheric composition and chemistry could be greater. E.g. “particle bursts”
have been observed in some coastal areas. There i
s evidence to show that condensable
iodine vapours (CIVs) formed from photolysis of CH2I2 produced by macroalgae is a
viable mechanism for explaining this.


i.

Figure 1 (L. Carpenter) shows the (almost textbook!) relationship between tidal height,
solar ra
diation and IO production. The relationship between CCN concentration and tidal
height has also been shown in the field during the PARFORCE project.


j.

Halogen cycling in coastal environments can be substantial and important in terms of
ozone and other ox
idant cycling


k.

Some observational evidence that Cl
-
radical chemistry in polluted air over the coastal
ocean can lead to net O3 production (Texas studies
-

Tanaka et al., 2003)









Figure 3: Iodine
chemistry in coastal regions.



Halogenated compounds and aerosols

o

Organic
-
Iodide compounds (methylated iodines) have been associated with new particle
production in tidal areas. (O’Dowd et al., 1999, 1998).


o

Interaction with NOx will release HCl from aer
osol and this has the potential to end up as
radical
-
Cl, which will play a role as an oxidant in coastal regions.


o

Br may also be released as a radical (not in as large of quantities as Cl, of course).


6.

Feedbacks


a.

Ocean
-
derived CCN impacting productivi
ty, soluble iron amounts being impacted by
sulfur or organic acid emissions from oceans.





Iodine
Chemistry in
the MBL

I
O

I

h
v

CH
2
I
2

CH
2
IB
r

CH
3
I,
I
2

O
3

h
v

Inor
gani
c


Iodine

eg
OIO
,
HOI

IONO
2
,
INO
2
,

HI, IX

Aeros
ol


Transpo
rt

to

Contine
nts

Ozone
Depletion

New Particle
Production;

Climate
Impact


J. Plane

7.

Methods for constraining


a.

Need better and continuous observations for several years at one (or multiple) location
locations.


b.

Need to get estimates of surface ar
ea, productivity, species abundance.


c.

Better/more flux measurements?



8.

Uncertainty/big questions

a.

What are the physical and biological constraints on trace gas exchange in the salt marsh?




b.

What is the effect of short
-
lived halogenated compounds on atmosp
heric
chemistry/aerosol formation?


c.

What are the impacts of increased nutrients on coastal ecosystem dynamics and the
emission of climatically active trace gases?


d.

What are the mechanisms producing the ultra
-
fine particle bursts?


e.

Harmful algal blooms


trace gas production from these species unknown


f.

What is the size distribution of aerosol produced by wave
-
breaking? (important for CCN
production and for reaction sites/composition).


g.

As with many things, the organic composition of the aerosol produced
(and what they
evolve into) are not well
-
known.


h.

In addition to the gas emissions from the microorganisms, what role is played by their
physical bodies/fragments?


i.

Kelp forests are large producers of methyl iodide, but how much of it reaches the
atmosphe
re?


C
OASTAL ZONE IMPACTS
ON GLOBAL BIOGEOCHEM
ISTRY
:


T
OPIC
#

3:

W
HAT ASPECTS OF COAST
AL ECOSYSTEMS ARE SI
GNIFICANT GLOBALLY
?


C
ONTRIBUTED BY
:

G.
-
K.

P
LATTNER
,

J.

K
LEYPAS
,

C.

N
EVISON
,

R.

R
HEW
,

A.

S
UBRAMANIAM


1.

How much do coastal zones matter for globa
l atmospheric carbon dioxide?


a. Overview


Whether on a global scale continental margins are currently a net sink or source of atmospheric
CO
2

is still cause for debate. Conventional wisdom suggests that continental margins are a net
source of CO
2

to the

atmosphere, mainly driven by the large riverine inputs of terrestrial carbon
and subsequent local remineralization. However, recent estimates based on regional studies point
to a net CO
2

air
-
to
-
sea flux in the continental ocean margins at present times, w
ith globally
averaged sink values ranging from 0.2 Pg C yr^
-
1 to as much as 1 Pg C yr^
-
1. In a recent
synthesis paper, Chen (2004) estimates that the coastal margins constitute a net CO
2

sink of 0.36
Pg C yr^
-
1 to the atmosphere based on mass balance calcu
lations, as well as direct pCO
2

measurements. This flux is a composite over many estuaries, coastal waters, and intensive
upwelling areas, typically supersaturated with respect to CO
2

and most open shelf areas, which
are probably undersaturated. According
to this synthesis the net CO
2

uptake in the coastal zones
is primarily driven by cross
-
shelf transport from nutrient
-
rich subsurface waters offshore.


Overall, this coastal CO
2

flux is a significant sink component in the global carbon cycle, given
that the

global ocean is believed to absorb nearly 2 Pg C yr^
-
1 of CO
2

at present.


b. CaCO
3



Calcium carbonate plays a significant role in the global carbon cycle, in that it acts as a
biogeochemical carbon buffer between atmosphere, ocean, and the geosphere. M
arine calcium
carbonate production, through the chemical reaction Ca
2+
+ 2HCO
3
-



2CaCO
3

+ 2H
+
, shifts the
carbon system equilibrium in seawater toward more acidic conditions, which results in a release
of CO
2

to the atmosphere (for every mole of CaCO
3

pre
cipitated, approximately 0.6 moles of
CO
2

are released). Dissolution of CaCO
3

works in reverse to take up CO
2
. CaCO
3

production
in the open ocean is considerably greater than on the continental shelves, but most of this
production dissolves before it re
aches the ocean sediments. A much greater proportion of
CaCO
3

production on continental shelves is preserved within the shallow shelf sediments.
Changes in shallow shelf CaCO
3

production almost certainly contributed to the glacial
-
interglacial changes i
n atmospheric CO
2

(Archer et al. 2000, Ridgwell et al. 2003) but by how
much is uncertain. Flooding of continental shelves during post
-
glacial sea level rise greatly
increased available area for CaCO
3

production, and much of that production was locked awa
y in
shelf sediments. This potential link between fluctuations in atmospheric CO
2

concentration and
shallow shelf CaCO
3

preservation is termed the "coral reef hypothesis" because coral reefs are
thought to be the main player in these CaCO
3

changes (Berger

1982, Opdyke and Walker 1992,
Kleypas 1997). Today, the estimated release of CO
2

to the atmosphere by shallow water CaCO
3

production is immeasurable against the background of CO
2

released by fossil fuel combustion.
However, it is likely that increases i
n atmospheric CO
2
, and associated changes in seawater
chemistry are driving net CaCO
3

production down, both due to a reduction in biological CaCO
3

production (considerable evidence shows that many organisms slow down calcification rates as
more CO
2

is driv
en into seawater), and an increase in geochemical CaCO
3

dissolution (although
this will not be effective in reducing atmospheric CO
2
; see Andersson et al. 2003). There are
other competing variables, such as changes in temperature, light penetration, or nu
trient inputs,
that can also affect CaCO
3

production and preservation.


c. Past and future role of coastal zones? Role of anthropogenic perturbation?


d. Carbon transport through the system?



2.

How large is the impact on atmospheric chemistry and aero
sols at different spatial scales?


a. Global significance of coastal areas to N
2
O emissions:


Coastal areas are believed to be a large source of the atmospheric greenhouse gas nitrous oxide
(N
2
O). Recent studies have estimated that N
2
O emissions from coast
al areas may account for 5
-
45% of the global oceanic N
2
O source, which in turn contributes ~30% of the total (natural +
anthropogenic) N
2
O source. Studies that consider anthropogenic N inputs tend to estimate the
highest coastal N
2
O emissions. One recent s
tudy from the heavily polluted southwestern Indian
continental shelf alone estimated N
2
O emissions equivalent to 10% of the global oceanic total.


b. Global significance of coastal areas to CH4 & DMS:


Recent estimates indicate that the the coastal oceans

are a net source of CH4 (0.1x10^12 mol
CH4 yr^
-
1), and DMS (0.07x10^12 mol DMS yr^
-
1) to the atmosphere (Chen, 2004). For CH4
shelf sediments are believed to be the principal source, whereas DMS originates mainly from
biological production in the water co
lumn. While both these net fluxes are small compared to
e.g. the large CO
2

fluxes, they are important on a global scale given the effect of CH4 and DMS
on the radiative balance of the earth.


c. Other constituents?



3.

Coastal
salt marsh and mangrove sw
amps




4.

River discharge


a. Role of rivers in general


Rivers are the major conduits for the transport of water, salt, organic matter, and mineral matter
from land to the ocean. A significant fraction of the anthropogenic CO
2

on land is ultimately
tr
ansported to the ocean by rivers. Terrestrially derived macronutrient input to the ocean (N, P,
Si) is also largely controlled by river system processes and these have been impacted by human
activity. Major rivers play a disproportionately important role

in this process with the world's 10
largest rivers transporting 40% of all the freshwater and particulate materials entering the ocean.
The Amazon River alone contributes about 20% of the freshwater input into the oceans and
hence while these processes h
ave a global impact, they are not "simply scalable" for
representation in global models. Up to 80% of global carbon burial occurs in river dominated
ocean margins.


b. Export of carbon in rivers to coastal areas


Export of dissolved inorganic and organic

carbon in rivers leads to emission of ~ 0.5 Gtons of
CO
2
-
C from receiving coastal waters. These emissions represent a natural cycle of CO
2

fixation
on land and subsequent return to the atmosphere via the ocean. The emissions are globally
significant with
respect to current efforts to quantify oceanic uptake of anthropogenic CO
2

(currently estimated at ~2 Gtons CO
2
-
C/yr) and should be accounted for when using the net
oceanic CO
2

flux estimated from surface delta
-
pCO
2

climatologies to estimate anthropogenic
CO
2

uptake.



C
OASTAL ZONE IMPACTS
ON GLOBAL BIOGEOCHEM
ISTRY
:


T
OPIC
#

4:

C
AN COASTAL ECOSYSTEM
S BE REPRESENTED IN
GLOBAL MODELS
?


C
ONTRIBUTED BY
:

C.

N
EVISON
,

K.

L
INDSAY
,

G.

M
C
K
INLEY
,

G.
-
K.

P
LATTNER
,

R.

S
EIFERT


1.
Prognostic Numerical Models




a. Cur
rent representation of coastal regions in global ocean models



Current global ocean biogeochemical models do not explicitly resolve coastal processes. Global
impacts of specific coastal processes are neglected. In coastal zones, the same biogeochemical
parameterizations as used for open
-
ocean are applied. Resolution of global models is typically 1º
to 4º, with some models achieving up to 1/3º in the tropics, and thus coastal topography is poorly
resolved. Global ocean modelers do not consider results fr
om coastal zones to be useful and do
not evaluate these results.


Biogeochemical processes in global models are parameterized to best fit open ocean
observations. Remineralization of the particle flux is instantaneous in the bottom layer, such that
no sed
iment burial occurs either in the open ocean or in the coastal zones. There is no explicit
sediment model. Dilution of tracers by freshwater input from rivers is included, but inputs of
nitrogen, DIC, or other tracers from land are not considered. In MOM4


Phytoplantkton (J.
Dunne), an explicit iron source from the bottom sediments, proportional to the particle flux
reaching this layer, is included at all grid points. A recent modification to this model is to also
include a Fe source from locations with a
vertical land / ocean boundary. Future directions under
current consideration with MOM4 are to include land nitrogen inputs via coupling with the
GFDL land model.



b. Nested regional models of coastal upwelling


One possible way to better resolve coa
stal oceans in global ocean biogeochemical models is to
use embedded gridding, allowing the model resolution to be increased in specified regions of
interest. An example of such a model is the Regional Ocean Modeling System (ROMS),
developed and used at UC
LA, which is currently applied e.g. to the U.S. West Coast with a
focus on the California upwelling system and to the whole Pacific. Simulations with ROMS can
be performed in multi
-
level setups, ranging from eddy
-
permitting to eddy
-
resolving resolutions.
A standard setup for the U.S. West Coast for example is to run the whole domain on a 15 km
grid (level 0), the central California upwelling region on a 5 km grid (level 1), and, for local
studies, the Monterey Bay area on a 1.5 km grid (level 2). This allo
ws the model to encompass
both the energetic eddy

variability and coastal topography within domains covering a wide range of distinct physical
environments and ecological or biogeographical regimes, while still being fairly computationally
efficient. Howev
er, spanning a wide range of ecological regimes requires rather complex
representations of ecosystems in order to realistically reproduce observations from different
domains. A "simple" NPZD
-
model has been used successfully for the diatom
-
dominated central

California upwelling region, but is insufficient further offshore towards the subtropical, nano
-

to
picoplankton
-
dominated oligotrophic gyre. Therefore, a more complex biogeochemical model is
used for the Pacific model.


c. Regional models of other (non
-
u
pwelling) coastal areas, e.g., U.S. east coast salt marsh



2.
Diagnostic Models



Since current global prognostic models do not explicitly resolve coastal processes, and
since configuring regional prognostic models to all coastal areas may be impractica
l, it may be
useful in some cases to develop simpler diagnostic models to address coastal research issues.
For example, Nevison et al., [2004] recently developed a global model of the coastal upwelling
emissions of nitrous oxide, a greenhouse gas produced

in subsurface waters in association with
O
2

consumption by microbial respiration. The model was based on satellite winds, their
orientation to the coastline, and a dissolved oxygen climatology. The model was useful in
identifying

regions of regions of hi
gh subsurface N
2
O production that overlapped with strong
and/or frequent coastal upwelling events that ventilated the N
2
O to the atmosphere. We did not
apply the model to non
-
upwelling coastal regions, although other global models of coastal N
2
O
emissions
, based on estimates of river N export, have not distinguished between upwelling and
other coastal ecosytems. For species such as CO, hydrocarbons and sulfur compounds, which
are produced in surface waters, the distinction between different types of coast
al systems may
not be as important; it may be possible to develop simple global models of the emissions of
these species based, e.g., on satellite chlorophyll data and solar insolation.


3.
Representation needs


a. How many different types of coastal zon
es need representation (temperature / topography /
phytoplankton types)?


b. What processes do we need to capture / understand how well?


c. Can these processes be parameterized / resolved in models?






C
OASTAL ZONE IMPACTS
ON GLOBAL BIOGEOCHEM
ISTRY
:


T
OPIC
#

5:

H
OW DO HUMANS IMPACT
COASTAL ZONE BIOGEOC
HEMISTRY AND WHAT AR
E THE
ECONOMIC IMPACTS OF
THESE CHANGES
?


C
ONTRIBUTED BY
:

M.

P
OTOSNAK
,

R.

R
HEW
,

R.

S
IEFERT
,

J.

W
HITE


1.
What are the main ways that humans impact coastal biogeochemistry?

a. Rising

sea level due to global temperature increase, which threatens coastal ecosystems.

b.

Sediment loading of rivers.

c.

Nutrient loading of rivers (dead zones).

d.

Changing the hydrological regimes of rivers flowing into coastal zones. Examples
include the Colorado Ri
ver (no flow to ocean) and the Everglades (drastic modification
of the sheet flow).

e.

Introduction of invasive species (may be more relevant for ecology rather than
biogeochemistry, though). On the fringe, I read an article in EOS in 1998 (vol 79, #35)
abou
t an exotic species of rodent called nutria that is eating away the Blackwater
National Wildlife Refuge off the Chesapeake Bay.

f.

Over fishing (again, more of an ecosystem impact).

g.

From the Pew Report
4
:

i.

Nonpoint source pollution: oil leaks, nitrogen,

ii.

Points

source pollution: feedlots, cruise ships

iii.

Invasive species

iv.

Aquaculture: particularly salmon farms

v.

Climate change: air temp, coral re

2.

What are the economic impacts of these changes? (e.g. fisheries?)


3.

How has the areal extent of terrestrial coastal ecosyste
ms changed?

a.

"Saltmarshes and Mangrove swamps are of tremendous importance to the U.S. Fish
and Shellfish industries. Despite their incredible economic importance, until recently
coastal wetlands were perceived primarily as potential development sites. The
earliest
estimate of total coastal zone wetlands comes from the 1922 Yearbook of
Agriculture. At that time the U.S. possessed an estimated 7,363,000 acres of tidal
marshes. A similar survey conducted in 1954 estimated that 5,290,000 acres of tidal
marshes
were left (Teal and Teal, 1968)
-

a staggering loss of fully 25% in just 32
years. Today, approximately half of all coastal wetlands in the lower 48 states have
been destroyed. According to the National Marine Fisheries Service (1983), annual
fishery losse
s due to estuarine marsh habitat loss are estimated at $208 million."
2

b.

Coastal wetlands include salt marsh/mangrove, fresh marsh, tidal flats, and swamp.
For the purposes of the following discussion, coastal wetlands refer to salt marshes
and mangroves on
ly. Terrestrial coastal ecosystems (salt marshes and mangroves)
contain among the most productive plant communities in the world and serve
numerous ecological and economic functions, such as fish nurseries, water
purification, and bird habitat. However, t
hese ecosystems are also among the most
pressured, as mangrove swamps have been destroyed for use as shrimp farms, and
salt marshes have been destroyed for urban development.

c.

In a 1986 (NOAA) Inventory by Alexander, Broutman, and Field, the amount of
coast
al salt marshes in the U.S. was 4,446,300 acres, but this estimate was based on
inventories that ranged from the 1950s to the 1980s.


4.

Land use change and movement of terrigenous material


References:

1
http://yosemite.epa.gov/oar/globalwarming.nsf/content/ImpactsCoastalZones.html

2
http://agen521.www.ecn.purdue.edu/AGEN5
21/epadir/wetlands/estuarine_uscz.html

3
http://oceancommission.gov/documents/prelimreport/welcome.html

4
http://www.
pewoceans.org/oceans/index.asp