United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97330
Research and Development
EPA-600/S3-81-023 May 1981
Project Summary
Production in Coastal
Salt Marshes of
Southern California
H. Peter Eilers
This study was designed to answer
four questions about macrophyte pro-
duction in coastal salt marshes of
southern California: 1) What levels of
production are achieved by plant
species and plant communities? 2) To
what extent does production vary
within and between marshes, espe-
cially those with and without regular
tidal inundation? 3) What physical
factors control or best explain varia-
tions in production? and 4) How does
production in southern California salt
marshes compare with that at other
latitudes on the Pacific Coast and at
similar latitudes on the Atlantic Coast?
Data were obtained by harvesting
macrophytes and monitoring environ-
mental factors (substrate salinity, pH,
nitrogen, redox, water content, and
tide level) at four locations—Sweet-
water River Estuary, Los Penasquitos
Lagoon, Upper Newport Bay, and
Bolsa Bay—over an annual cycle
beginning fall 1977.
Net aerial production estimates
computed by summing production in
individual species and adjusting for
interval death and shedding and disap-
pearance of dead material averaged
3196,3787,2150, and 2494 g m~ V1
for study sites, respectively. Production
levels were highest on creek levees
and transition to upland and lowest in
back levee depressions, fore levee
slopes, and pans—suggesting that
habitat, especially drainage and salin-
ity, exerts greater control over macro-
phyte production in the marsh than
does tide level alone. High levels of
production in Salicornia virginica and
Frankenia grand/flora at Los Penas-
quitos Lagoon suggest that production
in some plant species may be increased
by reduced tidal contact.
Production estimates from this
study, together with those of the same
author and others, support an increase
in salt marsh production with decreas-
ing latitude along the Pacific Coast,
and production levels in southern
California appear to be equal to or
greater than those of salt marshes at
the same latitude on the Atlantic
Coast.
This Project Summary was developed
by EPA's Environmental Research
Laboratory, Corvallis, OR, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
A growing literature suggests that
coastal salt marshes are among the
most productive of natural systems. Salt
marshes occupy a fortunate position
between the limits of tidal inundation.
Nutrients entrained by terrestrial runoff
are transported along with nutrients
from coastal waters to marsh soils by
tidal flux. While primary production in
the marshes is high, marked variations
in yield occur. Explanations for inter-
marsh variations in production have
involved factors related to tides; such as
frequency and duration of tidal inunda-
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tion, tidal range, waterlogging, drainage
density, and soil salinity. The level of soil
nutrients, especially nitrogen, has been
shown to influence yields.
Knowledge of salt marsh production
in North America rests almost totally on
investigations conducted along the
Atlantic and Gulf Coasts. The productivity
of Pacific marshes, especially those
along the California Coast, has yet to be
fully demonstrated.
Method
This investigation was initiated to
estimate production levels in southern
California salt marshes, to relate varia-
tions in macrophyte production within
and between marshes to physical vari-
ables, and to compare production esti-
mates with those of marshes on other
coasts. Four study areas were selected
to represent the variety and latitudinal
extent of coastal salt marshes in southern
California (Figure 1). Sweetwater River
Estuary, located in southern San Diego
Bay, contains 83 ha of salt marsh with
high floristic diversity. The marsh is
perennially open to tidal fluctuation. Los
Penasquitos Lagoon is seasonally closed
to tidal contact, supports a depauperate
flora dominated by Salicornia virginica,
contains 95 ha of salt marsh, and is
located on the northern city limits of San
Diego. Upper Newport Bay, 110 km
north of Los Penasquitos Lagoon, is
continually open to the Pacific Ocean.
The salt marsh there is floristically
diverse, low in stature, and covers 58
ha. Bolsa Bay, in north Oregon County,
is highly disturbed by dredging and
diking, floristically poor, and has been
artifically closed to tidal fluctuation
since 1899.
Transects containing sample macro-
plots were located in each study marsh
parallel to the elevation gradient. Vege-
tation was harvested from within a 2.0x
2.5 m frame at intervals of six to eight
weeks from October 1977 to September
1978. Samples were sorted to species
and dried to constant weight. Litter bags
were placed in each marsh to estimate
decomposition rate of dead material.
Net production was estimated by a
modification of the Smalley method
which incorporated decomposition rates.
At the time of each vegetation harvest a
set of substrate measurements was
taken from each macroplot, including
salinity of interstitial and gravity water,
pH, redox, ammonia, water content and
temperature. Macroplot tidal elevation
was surveyed and each macroplot was
classified according to habitat type.
Results
Net production ranged from 164
g rrf V"1 at a low site in Bolsa Bay to
6369 g nrf 2yr ' for a mid-elevation site
Pacific Ocean
Pacific Ocean
Figure 1. Study areas clockwise from upper left are Sweetwater River Estuary, Los Penasquitos Lagoon, Bolsa Bay, and Uppe
Newport Bay. Arrows denote locatoin of sampling transects.
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Marsh
Sweetwater River Estuary
Los Penasquitos Lagoon
Upper Newport Bay
Bolsa Bay
Mean
3196
3787
2150
2494
S.D.
1330
1528
795
1731
n
31
21
25
5
at Los Penasquitos Lagoon. The overall Table 1. Mean Annual Net Production Estimates (grri~zyr~^) and Standard Deviations
mean was 2986 g m~2yr~1, and Los
Penasquitos Lagoon was clearly the
most productive marsh (Table 1). The
most productive plant species overall
were Frankenia grandiflora. Salicornia
virginica and Spartina foliosa (means
1046, 1483, and 716 g m~2yr~1, respec-
tively). Production tended to increase
with elevation at all sites except Upper
Newport Bay (Figure 2). Variation in
production between habitats was
significant and two habitat types. Levee
Crest and Upland Transition, accounted
for the greatest macroplot production
(Figure 3). This suggested that good
drainage and associated aerobic soils,
moderate salinities, and moderate to
low soil ammonia provided conditions
associated with optimal plant growth.
Regression analysis reinforced this
observation.
Comparison of production levels in
the four marshes studied with those
published for other sites along the
Pacific Coast is difficult because methods
of estimation vary. However, there
appears to be a tendency for production
increase with decreasing latitude. Such
a gradient of productivity has been dis-
covered by investigations on the Atlantic
Coast, and it appears that yields in
southern California salt marshes are
similar to those of low latitude Atlantic
Coastal sites.
Conclusions
Several conclusions may be drawn
from this study: 1) Macrophyte produc-
tion varies within and between southern
California salt marshes, 2) macrophyte
production in some species may be
increased by reduced tidal contact, 3)
habitat, especially drainage and salinity,
exerts greater control over macrophyte
production in the marsh than does tide
level alone, 4) production estimates
support an increase in salt marsh pro-
duction with decreasing latitude, and 5)
levels of macrophyte production in
southern California salt marshes are
comparable to those at the same latitude
on the Atlantic Coast.
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Figure 2. Macroplot net production (g m yr~ ) and elevation (m). Abbreviations for study areas after Figure 1.
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o
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The EPA author H. Peter Eilers is with the Environmental Research Laboratory,
Corvallis, OR 97330.
Harold V. Kibby is the EPA Project Officer (see below).
The complete report, entitled "Production in Coastal Salt Marshes of Southern
California," (Order No. PB 81-171 845; Cost: $9.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Corvallis, OR 97330
* U.S. GOVERNMENT PRINTING OFFICE 1981 -757-012/7109
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