United States
Environmental Protection
Agency
Chesapeake Bay
Program
Annapolis MD 21403
Research and Development
EPA-600/S3-82-083 Dec. 1982
Project Summary
Historical Review of
Water Quality and
Climatic Data from
Chesapeake Bay with
Emphasis on Effect of
Enrichment
Donald Heinle, Christopher D'Elia, JayTaft, John S. Wilson, Martha
Cole-Jones, Alice B. Caplins, and L. Eugene Cronin
Review of the available data on wa-
ter quality in Chesapeake Bay has re-
vealed changes over recent decades
caused by enrichment with nutrients.
In the upper and middle Bay, and sev-
eral tributaries, concentrations of al-
gae present during the summer months
have increased since the mid-1960s.
There have been decreases in the clar-
ity of the water associated with in-
creased algal stocks. Nutrient concen-
trations have also increased, phos-
phorus more notably so than nitrogen.
In some of the tributaries, such as the
Patuxent for which we have the most
historically complete data, increased
algal production has led to reduced
concentrations of oxygen below the
halocline in the middle part of the estu-
ary. The variations in concentrations
of oxygen are now more extreme in
surface waters than in the early 1960s
in the Patuxent. Oxygen concentra-
tions in the open Bay have not
changed greatly, with the possible ex-
ception of extreme conditions, as dur-
ing periods of extensive ice cover.
There have been historical variations
in the abundance of commercial fishe-
ry stocks that may be closely related to
climatic variations. From 1969 to
1980, however, stocks of many ana-
dromous species and marine spawn-
ers representing higher trophic levels
have declined to new long-time lows.
The principal exceptions are menha-
den (marine-spawning planktivorous
fish) and bluefish (marine-spawning
top predators). That same time inter-
val has, however, been a period of
above average rainfall and corre-
sponding reduced salinities in the Bay,
making conclusions concerning ef-
fects of enrichment difficult to achieve.
This Project Summary was devel-
oped by EPA's Chesapeake Bay Pro-
gram. Annapolis. MD, 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
Enrichment of Chesapeake Bay wa-
ters by nutrients from sewage treatment
plants and agricultural and urban runoff
emerged as a major water quality issue
during the 1950s. Population growth
and the related changes in land use, the
increasing reliance on secondary treat-
ment of municipal wastes, and the
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centralization of sewage treatment
services in the region's growing urban
centers all contributed to increased
nutrient loadings in some segments of
the Chesapeake Bay, particularly the
upper Potomac River and Baltimore
Harbor. By 1960 blue-green algae were
creating nuisance conditions in the
upper Potomac, and problem quantities
were common in northern sections of
the Bay ten years later.
The relationship between nutrient
loadings from various sources and algae
production have been reviewed by a
number of Bay-area scientists, but
trends and the extent of water quality
changes have not been thoroughly
documented. This report, sponsored by
the Environmental Protection Agency's
Chesapeake Bay Program (Grant No.
R806189010), includes a historical
review of Chesapeake Bay water quality
and climatic data and documents
nutrient-related changes that have
occurred. The emphasis is on the effects
of enrichment by the major nutrients in
sewage, nitrogen and phosphorus.
Climatic cycles are examined as well as
the effects of one unusual climatic
event, Tropical Storm Agnes.
Procedure
Temperature and rainfall data appli-
cable to the Chesapeake Bay region
were compiled and examined for long-
term trends and possible relationships
to the 20 year solar cycle. Fluctuations
in annual mean water temperature
were analyzed to determine the general
trends and the frequency of extremely
cold winters. Rainfall and freshwater
flow data for the Bay proper and major
tributaries were examined to determine
cyclic trends and nutrient input factors.
The frequency and intensity of major
storm events were also examined and
compared to detailed data describing
the effects of Tropical Storm Agnes. All
precipitation data were used in the
analysis of short-term variations in
freshwater flow. Long-term flow trends
were determined by analysis of fixed
point salinity data.
The scientists developed estimated
nutrient input values for municipal
wastewater treatment facilities cur-
rently on-line and rated as capable of
providing secondary treatment. The
loading figures for each major tributary
in the Chesapeake Bay Basin (shown
below) are based on the assumption
that every one million gallons of
secondary effluent contains 73.8 pounds
of phosphorus and 182.6 pounds of
nitrogen. The estimated total point
source loadings, based on permitted
flow, for the entire basin are included in
Table 1.
Flow data and an inventory of known
point sources were used to produce the
baseline estimates for flow in the drain-
age basin and the percentage of flow
that is treated sewage effluent. (See
Table 2.)
Trend analysis was based on a review
of demographic statistics, land use
changes, and water quality data, the lat-
ter gathered by a number of organiza-
tions involved in sampling of Chesa-
peake Bay waters as far back as 1940.
All data, unless clearly erroneous or
suspect were used. The investigators
attempted to document all analytical
techniques, identify data sources and
senior scientists, and discuss the validi-
ty and comparability of various analyti-
cal techniques.
Results/Conclusions
Many of the Chesapeake Bay water
quality changes, particularly in the
tributaries, occurred prior to implemen-
tation of pollutant discharge permit and
monitoring programs called for by the
1972 Federal Water Pollution Control
Act. Trends for historic problem areas
are difficult to identify, but data clearly
indicate nutrient loadings are increasing
in historically enriched areas and
throughout the Bay. Phosphorus load-
ings are increasing at a more rapid rate
than nitrogen, possibly because of the
use of phosphorus compounds in
detergents.
Carbon loadings are also continuing
to increase despite efforts to upgrade
solids removal capabilities at municipal
wastewater treatment facilities. Remov-
al capabilities were improved between
1960 and 1969 through construction of
secondary treatment modes at public
wastewater treatment systems. Total
carbon loadings have, however, con-
sistently increased throughout the
1970s. Improved removal capabilities at
sewage treatment systems have been
outpaced by increases in regional
population and increases in the percent-
age of population serviced by centralized
treatment.
The population increases and related
land use changes have not been
uniform throughout the region. The
lower Susquehanna River Basin, for
example, experienced a 10 percent
growth rate between 1960 and 1970.
The population in the Patuxent River
Basin nearly doubled during this same
period. Effluent discharged to the
Patuxent rose at a more rapid rate than
the population, increasing from 2.6
million gallons a day (mgd) in 1963 to
26.6 mgd by 1973.
Table 1. Point Source Loadings for the Chesapeake Bay Basin
Nitrogen
Phosphorus
River
Susquehanna
Patuxent
Potomac
Rappahannock
York
James
Chesapeake Bay
(including
tributaries)
Kg day'1
28,841
2,203
38,864
795
323
16,151
108,916
1069 yr"1
70,527
804
14,185
290
118
5,895
39,754
Kg day'1
12,061
890
14,495
321
131
6,528
44,020
106g yr-1
4,402
325
5,290
117
48
2,383
16,067
Table 2. Baseline Estimates for Flow and Its Percentage of Sewage Effluent in the
Chesapeake Bay Drainage Basin
River
Susquehanna
Patuxent
Potomac
James
Chesapeake Bay
27 -yr average
flow (cfs)
38,800
1.085'
13,900
10,100
75,200
Point sources
of sewage (cfs)
557
41.15
670
302
2.034
Percent of freshwater
that is sewage
1.4
3.8
4.8
3.0
2.7
1 Patuxent flows were taken from the Johns Hopkins University (1966) rather than the
U.S. Geological Survey Data.
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Changes in Chesapeake Bay water
quality attributable to land use and
demographic changes are not uniformly
distributed throughout the Bay. Upper
Bay phosphorus concentrations, variable
and seasonal in the past, have increased
and are now relatively uniform all year.
Nitrogen concentrations have also
increased, but some of the increased
loadings appear to be passing through
the nutrient pool or are lost through
denitrification. Nitrogen appears to be
the limiting nutrient in the upper Bay,
but low light intensity in this turbid
region could be restricting algae produc-
tion. Overall, algae production has
increased.
The effects of nutrient enrichment in
the middle Bay are modest but early
signs of change are present. Current
phosphorus and chlorophyll a concentra-
tions are slightly higher than historic
measurements and primary algae
stocks show signs of increased produc-
tion. Dinoflagellate blooms are now
common and some data suggest that
the deep water dissolved oxygen mini-
mum is changing. The effects of the
altered dissolved oxygen regime on
remineralization from sediments are
significant and may be driven by
particulate organic matter deposition
rates.
The lower Bay is relatively unaffected
by nutrient inputs although phosphorus
concentrations have increased slightly.
The negligible increase in nutrient
levels may be attributable to dilution,
which is significant in this region due to
the massive exchange of water at the
mouth of the Bay. Another possible
explanation is that nutrients are being
trapped and utilized in upper sections of
the Bay. If light restricts algae production
in these upper regions, the nutrients
might begin to progress further down
the Bay and stimulate algae production
there. Increases in algae productivity
are now being observed below the
Potomac River.
Concentrations of both major nu-
trients and chlorophyll a have increased
in all parts of the Patuxent River and
demonstrate a distinct downstream
progression. Ambient concentrations in
the upper, turbid portion are relatively
high all year. Although chlorophyll a has
increased somewhat, light may be
limiting primary production. Low dis-
solved oxygen concentrations in the
upper Patuxent appear related to high
concentrations of particulate carbon,
not chlorophyll. Both nutrient and
chlorophyll concentrations have in-
creased in the lower river segments.
Dissolved oxygen levels in the surface
waters are increasingly variable and
extended periods of near anoxia in
bottom waters are now being observed.
Patuxent plankton demonstrate a high
dependence on recycled nitrogen during
summer months, which suggests that
restricting total annual input may limit
primary production. The changes now
being observed in the river will probably
progress further as loading rates
increase with population growth in the
basin.
Changes in the upper Potomac cannot
be documented because dissolved
oxygen and algae problems were
present before systematic sampling
programs were put in place. Algae
production is increasing in the lower
reaches, however, and major changes
might occur next nearthe upper limits of
salt intrusion.
The Rappahannock and York Rivers
have both experienced increases in
phosphorus and chlorophyll a concentra-
tions. Trends for nitrogen cannot be
determined. Minimum dissolved oxygen
concentrations in the lower York bottom
waters have decreased, but secondary
effects have not been thoroughly
studied. Periodic anoxia in the lower
York has resulted in cyclic changes in
rates of remineralization from sedi-
ments.
Conditions in the upper James are
similar to those in the Potomac. Historic
conditions and changes are not well
documented so trends could not be
determined. Concentrations of both
major nutrients have increased in the
lower James, but there has not been a
concurrent increase in chlorophyll a.
Low dissolved oxygen levels in bottom
waters have been observed recently,
but trends cannot be established.
Recommendations
Natural dissolved oxygen regimes
have been altered by nutrient inputs to
some segments of the Chesapeake Bay.
Enrichment problems are occurring in
some areas of the Bay but are not
apparent throughout most of the estuary.
Prudent, conservative management can
prevent continued degradation.
Sensible efforts to reduce nutrient
inputs should continue. Projected
population projections for the watershed
and present evidence suggest there
could be continued changes on the
ecology of the Bay unless strategies for
reducing nutrient inputs, such as land
application of municipal sewage, are
sought and pursued.
Donald Heinle. Christopher D'Elia, Jay Taft, JohnS. Wilson, Martha Cole-Jones,
Alice B. Caplins, and L Eugene Cronin are with the University of Maryland,
Solomons, MD 20688.
Thomas Pheiffer was the EPA Project Officer (for information, see contact
below).
The complete report, entitled "Historical Review of Water Quality and Climatic
Data from Chesapeake Bay with Emphasis on Effect of Enrichment," (Order
No. PB 82-265 471; Cost: $19.SO, subject to change) will be available only
from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
For information contact David Flomer at:
Chesapeake Bay Program
2083 West Street, Suite 5G
Annapolis, MD 21403
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