HomeMy WebLinkAboutNantucket WQ Tech Memo 2010 Final Report_201410071025008227 1
Technical Memorandum
FINAL REPORTFINAL REPORTFINAL REPORTFINAL REPORT
Water Quality Monitoring and Assessment of the
Nantucket Island-Wide Estuaries and Salt Ponds
2010
To:
David Fronzuto
Town of Nantucket
Marine Department
37 Washington Street
Nantucket, MA 02554
From:
Brian Howes, David White and Roland Samimy
Coastal Systems Program
School of Marine Science and Technology (SMAST)
University of Massachusetts-Dartmouth
706 South Rodney French Blvd.
New Bedford, MA 02744
2
The Technical Memorandum is organized as follows:
1. Overview
· Background
· Need for a Monitoring Program
2. Summary of Sampling Approach in designated estuaries and salt ponds:
· Nantucket Harbor
· Madaket Harbor
· Long Pond
· Hummock Pond
· Miacomet Pond
· Sesachacha Pond
3. Results of Sampling: Summary of Water Quality Results
· Review of and comparison to historical data
4. Trophic State: Water Quality/Eutrophication Status
5. Recommendations for Future Monitoring
Overview
Background: Coastal salt ponds and estuaries are among the most productive
components of the coastal ocean. These circulation-restricted embayments support
extensive and diverse plant and animal communities providing the foundation for many
important commercial and recreational fisheries. The aesthetic value of these systems,
as well as the freshwater ponds of a town, is also significant to both residents and the
tourist industry alike. Maintaining high levels of water quality and ecological health in
these aquatic systems (fresh and marine) is fundamental to the enjoyment and
utilization of these valuable resources for all coastal communities.
Nutrient over-enrichment is the major ecological threat to water quality in the salt ponds
and embayments within the Town of Nantucket, primarily via ecological degradation
which results when nutrient loading exceeds the assimilative capacity (also called critical
nutrient threshold) of the system for new nutrient inputs. Of the various forms of
pollution that threaten coastal waters (nutrients, pathogens and toxics), nutrient inputs
are the most insidious and difficult to control. This is especially true for nutrients
originating from non-point sources, such as nitrogen and phosphorous transported in the
groundwater from on-site septic treatment systems. On-site septic treatment systems
are the primary mechanism for waste disposal within the Madaket Harbor/Long Pond,
Hummock Pond, Miacomet Pond and Sesachacha Pond watersheds. Nantucket Harbor
is in a somewhat different situation as the watershed to that system is almost entirely
sewered. Nevertheless, the nutrient characteristics and ecological health of that system
must be monitored given the shellfish fishery that depends on the water quality of
Nantucket Harbor. Since nitrogen and phosphorous is a natural part of estuarine and
pond systems, it is important that management allow for the natural capacity of these
systems to absorb watershed nutrient inputs. Through the coupling of monitoring data to
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the Massachusetts Estuaries Project (MEP) watershed loading analysis developed in
collaboration with the Coastal Systems Program (CSP), the most cost-effective
management strategies can be found to protect these valuable aquatic environments.
Need for a Monitoring Program: Conserving and/or restoring the environmental health
of coastal embayments and freshwater ponds is achievable, but only through proper
management of the waters and watersheds to each. Managing environmental health
requires a quantitative understanding of the biological and physical processes which
control nutrient related water quality within a specific basin and the role of watershed
inputs in the nutrient balance of the receiving waters. An essential step in managing
these fresh and saltwater systems is to monitor their water quality. The results of a
long-term monitoring effort are needed to determine the status and trend of ecological
health of each system to assess the need for management action and when coupled
with higher-end ecological data to support the development of site-specific management
plans.
Water quality monitoring of Nantucket's fresh and saltwater systems should focus on
summer-time conditions as the warmer months typically have the lowest water quality
conditions, which are the target of resource management. The Town of Nantucket has
a long history of monitoring of its aquatic systems generally by the Nantucket Marine
Department to support the protection and management of the natural resources of the
Town of Nantucket. This effort has also allowed analysis by the Massachusetts
Estuaries Project, tasked with determining the estuary specific nutrient thresholds for
restoration/protection of all the coastal systems of southeastern Massachusetts inclusive
of Nantucket and Martha’s Vineyard.
Water quality monitoring programs can also maximize the value of their results by
structuring their sampling and analysis program such that results can be cross
compared to water quality monitoring data collected throughout the region. In this
manner, inter-ecosystem comparisons can be made to better assess system
health/impairment and function and formulate appropriate nutrient management
strategies. This allows individual towns to directly benefit from lessons learned
throughout the wider region.
Summary of Sampling Approach
Monitoring Project Team: To address the present nutrient related ecological health
issues of the salt ponds and embayments within the Town of Nantucket and to provide
necessary information with which to develop policies to protect and/or remediate these
systems with regard to nutrient inputs, a long-term municipally coordinated monitoring
effort was established and coordinated through the Nantucket Marine Department in
early 2000 which continued through 2007. The program was interrupted in 2008 and
2009. In 2010 it was determined that the Nantucket Island-wide Water Quality
Monitoring Program should be resumed with support from the Coastal Systems Program
at the University of Massachusetts-Dartmouth, School for Marine Science and
Technology (SMAST). The Coastal Systems Program has also been responsible for the
development and coordination of the majority of the estuarine and pond water quality
monitoring across southeastern Massachusetts, Cape Cod and the Islands as well as
the analysis of all the samples collected and synthesis of the resulting water quality
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data. A such, the CSP is able to leverage this comprehensive water quality database to
further evaluate results obtained from the Nantucket Island-wide monitoring program.
CSP scientists focused primarily on the analysis of samples collected from the effort and
data analysis while the Nantucket Marine Department focused primarily on field
sampling and data collection on physical parameters. Both participated in the
compilation of field and laboratory data to provide an ecological overview of water quality
conditions within each of the systems monitored. The goals of the monitoring program
were to:
(1) determine the present ecological health of each of the main salt ponds and estuaries
within the Town of Nantucket,
(2) gauge (as historical data allows) the decline or recovery of various salt ponds and
embayments over the long-term (also part of TMDL compliance), and
(3) provide the foundation (and context) for detailed quantitative measures for proper
nutrient and resource management, if needed.
This latter point (3) is critical for restoration planning should a system be found to be
impaired or trending toward impairment.
Water Quality Program Description: Sampling took place during the warmer
summer/early fall months (May-October) of 2010, the critical period for environmental
management. Samples were collected from 6 systems (Figures 1, 2, 3, 4 and 5) and 6
streams on dates (“events”) following the schedule presented in Table 1. The Nantucket
Marine Department oversaw the sampling and all samplers who were involved were
given refresher “training” by CSP staff to meet QA requirements.
The physical parameters measured in the estuaries included: total depth, Secchi depth
(light penetration), temperature, pond and estuary state, general weather, wind speed
and direction, and dissolved oxygen levels. Laboratory analyses for estuaries included:
salinity, nitrate + nitrite, ammonium, dissolved organic nitrogen, particulate organic
carbon and nitrogen, chlorophyll a and pheophytin a and orthophosphate. For
freshwater streams parameters included: specific conductivity, nitrate + nitrite,
ammonium, dissolved organic nitrogen, particulate organic carbon and nitrogen,
chlorophyll a and pheophytin a, orthophosphate and total phosphorus. In addition, 14
sets of field duplicates were taken as part of the field sampling protocol for QA analysis.
Data were compiled and reviewed by the laboratory for accuracy and evaluated to
discern any possible artifacts caused by improper sampling technique.
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Table 1. Sampling Schedule for 2010 Nantucket Water Quality Monitoring Program
Month Nan. Har. Madaket Sesach. Miacomet Hummock Long Streams
Jan
Feb
Mar
April
May May 18 May 20 May 26 May 26 May 25 May 19
June June 2, 17 June 3, 15 June 24 June 24 June 29 June 17 June 28
July July 1, 15, 30 July 16, 27 July 26 July 26 July 28 July 29
August Aug. 13 Aug. 12, 30 Aug. 26 Aug. 26 Aug. 27 Aug. 11
September Sept. 1, 14 Sept. 13 Sept. 23 Sept. 23 Sept. 28 Sept. 15
October Oct. 21
November
December
Totals 10 8 5 5 5 5 1
6 Figure 1. Madaket Harbor and Long Pond sampling stations 2010.
7 Figure 2. Nantucket Harbor sampling stations 2010.
8 Figure 3. Sesachacha Pond sampling stations 2010.
9 Figure 4. Hummock Pond sampling stations 2010.
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Figure 5. Miacomet Pond sampling stations 2010.
Station 3
Station 1
Station 2
Station 3
Station 1
Station 2
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Summary of 2010 Water Quality Results for Nantucket Sampling
Water samples collected from May through October in the estuarine systems generally
showed that organic nitrogen (dissolved + particulate) dominated the Total Nitrogen pool
(89%-98%), while bio-available nutrients in the form of nitrite and nitrate (NOx) and ammonium
(NH4) accounted for 2%-11% of Total Nitrogen (Table 2, Figure 6). That organic nitrogen is
such a large part of the Total Nitrogen in these systems would indicate that they are effectively
converting the bioavailable inorganic forms of nitrogen into organic forms (e.g. phytoplankton).
Where tidal flushing is effective, much of this particulate matter along with dissolved nutrients
is washed out of the system resulting in good water clarity as evidenced by the greater secchi
depth readings in Nantucket Harbor and Madaket Harbor (Table 2). Corresponding
Chlorophyll pigment concentrations were lowest in these well flushed systems (Table 2).
Where tidal flushing is more restricted in Long, Hummock, Miacomet and Sesachacha Ponds,
water clarity is relatively poor as shown by generally shallower Secchi Depth recordings and
higher Chlorophyll pigment concentrations (Table 2).
Nitrogen data from the streams sampled in June showed a similar pattern with organic forms
of N (DON and PON) accounting for 84%-97% of the TN and inorganic forms (DIN) 3%-16%
(Table 2).
Average Total Nitrogen values ranged from 1.75 mg/L in Long Pond, 0.944 mg/L in Hummock
Pond, 0.919 mg/L in Miacomet Pond, 0.704 mg/L in Sesachacha Pond, all relatively poorly
flushed. Average TN levels in all 4 ponds are significantly higher than average values in the
“offshore” stations NAN 4 and MH4 which average 0.302 and 0.285 mg/L, respectively (Table
2, Figures 1, 2).
Average TN level in Madaket Harbor (Stations 1-3, not including Station 4, offshore) was 0.462
mg/L, compared to the off-shore Station 4 (0.285 mg/L). Average TN in Nantucket Harbor (all
Stations except Station 4, offshore) averaged 0.369 mg/L, compared to 0.302 mg/L at the off-
shore Station 4 (Table 2). TN concentrations in the 6 streams adjacent to Nantucket Harbor
ranged from 0.565 mg/L in Stream 8 to 2.139 mg/L in Stream 6B (Table 2). In spite of the
high TN concentrations in these 6 streams and the likely high TN loads that these streams
contribute to the Harbor, tidal flushing and dilution with lower concentration Harbor waters
seems to be an effective mechanism to keep TN levels in the main body of the Harbor
relatively low (Table 2, Figure 2). TN concentrations in Polpis Harbor, which is fed by the high
TN levels in Streams 4, 6B and 6C, are somewhat higher than the levels in the main Harbor
but still significantly lower than the levels in the streams themselves (Table 2, Figure 2).
Within Long, Hummock and Miacomet ponds, there is a general gradient of nutrient (N and P)
and chlorophyll concentrations from high levels in the upper, more enclosed and poorly
flushed reaches of the estuaries to lower concentrations closer to the outlets where flushing is
more effective (Figure 6, Table 2). In Sesachacha Pond, there is no noticeable nutrient or
chlorophyll gradient among any of the 4 Stations (Figure 6, Table 2). Madaket Harbor shows a
small nutrient gradient (and a larger chlorophyll gradient) from Station 1 in Hither Creek (which
receives discharge from Madaket Ditch), and is relatively poorly flushed, out to Station 2 in the
Harbor. No significant gradient was observed within the Harbor itself from Station 2 out to the
off-shore Station 4 (Figure 6, Table 2).
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In Nantucket Harbor, there is a very small nutrient gradient from Wauwinet at the Head of the
Harbor and the more enclosed Polpis stations out to the entrance at Stations 8 and 4 (Figure
6, Table 2). There is also a chlorophyll gradient with the highest concentrations at the 2 Polpis
Stations (5 and 6), decreasing in the main Harbor and out to the off-shore Station 4 (Table 2).
In reviewing the 2010 dissolved oxygen data, we are concerned about the results at many of
the sites sampled. Some of the values seem low and at some stations, there is a lack of a
vertical profile. In Nantucket Harbor, for instance, there is no significant difference in dissolved
oxygen values between Station 3 off of Wauwinet and the off-shore Station 4. Because of
these concerns, we feel that there is a need to strengthen the dissolved oxygen data base for
the future. We have made some recommendations which we have noted at the end of the
discussion section.
Comparison of the 2010 data with historical data: At all sites, historical TN levels from
previous years of sampling were compared to 2010 TN concentrations. Historical data
presented here are from the Massachusetts Estuaries Project (MEP) reports for Nantucket
Harbor, Sesachacha Pond and Madaket Harbor/Long Pond. Historical data for Hummock
Pond 2007 and for Miacomet Pond 2005 are from the Annual Reports by the Nantucket
Marine and Coastal Resource Department. Not all sites sampled historically were sampled in
2010 but those that were are compared to the historical data in Tables 3 through 6.
The 2010 Nantucket Harbor TN data generally compare well with historical data from the
same or adjacent sites sampled by both SMAST and the Town from 1988 through 2005
(Figure 7, Table 3). Not all of the historical sites were sampled in 2010 (Table 3). At Station
Town 3, the historical mean for TN was 0.401 + 0.115 mg/L while the 2010 TN value is 0.392
mg/L. At Station 3A the historical mean for TN was 0.336 + 0.112 mg/L. The 2010 TN value
at the comparable Station Town 2 was 0.297 mg/L. In East Polpis Harbor the historical mean
is 0.362 + 0.112 mg/L while the 2010 value is 0.438 mg/L. In West Polpis, the historical mean
is 0.388 + 0.119 mg/L similar to that in East Polpis. The 2010 value for TN is 0.431, similar to
the 2010 value in East Polpis. The historical mean value for TN in the mooring area (Stations
7, 1 and 1A) is 0.326 + 0.106 mg/L. The 2010 TN concentration at Town Station 7
(comparable to 1A) is 0.377 mg/L. Finally the historical TN mean at the off-shore Station (OS
and Town 4) is 0.239 + 0.041 mg/L. The 2010 mean for TN is 0.302 mg/L.
In Sesachacha Pond, only Station 1 was available for comparison (Figure 8). The historical
mean for TN was 1.197 + 0.078 mg/L while in 2010 the value was less at 0.684 mg/L (Table
4).
In Madaket Harbor only MEP M11 and Town 1 were comparable sites. TN values agreed very
well here. The historical mean was 0.620 + 0.215 mg/L at M11 while the 2010 value was 0.626
mg/L (Table 5). The 2010 Stations 2 and 3 were distributed throughout the harbor between
historical stations 3 and 10, and 10 and 2, respectively and 2010 Station 2 was located at the
mouth of Hither Creek (Figure 9). TN values at these stations were comparable to values at
the historical stations (Table 5).
In Long Pond, the historical value of TN at Station 2 was 0.971 + 0.369 mg/L while the 2010
value at comparable Town Station 5 was 1.385 mg/L (Figure 9, Table 5). At historical Station
4, mean TN concentration was 0.894 + 0.278 mg/L; the 2010 value at Town 6 was 2.044
mg/L. Both 2010 values are higher than the historical means but are reasonable in
comparison given the variability in the historical data as evidenced by the standard deviation
(s.d.) of the means (Table 5).
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In Hummock Pond, 3 Stations have both 2007 and 2010 data from Town sampling programs,
Stations 1, 3 and 7 (see Figure 4). At Station 1, the 2007 TN mean value was 0.751 + 0.374
mg/L while the 2010 value was 0.616 mg/L (Table 6). For Station 3 (2007) the TN mean value
was 0.630 + 0.388 mg/L and the 2010 mean was 0.589 mg/L (Table 6). The Station 7 2007
mean for TN was 1.283 + 0.969 mg/L while the 2010 value was 1.786 mg/L (Table 6). The
2010 data compare well with the 2007 data.
Town data for Miacomet Pond was available at all 3 Stations from 2005 and 2010 (see Figure
5). At Station 1, the 2005 mean TN concentration was 0.842 + 0.191 mg/L and the 2010 value
was 0.854 mg/L (Table 6). The Station 2 mean TN value was 0.855 + 0.213 mg/L while the
2010 concentration was 0.811 mg/L (Table 6). Finally at Station 3 the lone 2005 value of TN
was 0.280 mg/L. The 2010 value was 1.093 mg/L (Table 6). It is not clear why the lone TN
value in 2005 was so low compared with the other Stations in the Pond but the 2010 and the
historical data from the other 2 stations agree well.
Trophic State of the Estuaries of Nantucket Island
The Trophic State of an estuary is a quantitative indicator of its trophic health and is based on
concentrations of Nitrogen, Secchi Depth, lowest measured concentrations of Dissolved
Oxygen, and Chlorophyll pigments. Trophic health scales generally range from Oligotrophic
(healthy) to Mesotrophic (showing signs of deterioration of health) to Eutrophic (unhealthy,
deteriorated condition). The Trophic Health Index Score used here is a basic numerical scale
based on criteria for open water embayments and uses the above mentioned measured
parameters to create a habitat quality scale (Howes et al. 1999,
http://www.savebuzzardsbay.org). For Nantucket, a trophic index score was calculated for all
the sampled estuaries using the 2010 data (Table 7). As we stated earlier, because there is
some concern about the dissolved oxygen data from 2010, we also calculated a trophic index
for these same estuaries without the oxygen data (Table 8). The Health Status of each site
was based on the Index Score, which is, in turn, based on the data collected during the
sampling events. The ranges of Index scores that fall within a particular Health Status
determination are given at the bottom of both Tables 7 and 8. Figures 10-14 show the Health
Status of each of the 2010 sampling sites within the estuaries studied. Values calculated with
the dissolved oxygen data are shown as upright triangles and values without the oxygen data
are shown as inverted triangles. The colors of each triangle represent the Health Status of its
site:
Color Health Status
Blue High Quality
Blue/Yellow High-Moderate
Yellow Moderate
Yellow/Red Moderate/Fair
Red Fair/Poor
Trophic Index scores changed (Madaket Harbor and Nantucket Harbor scores increased while
the others decreased) when the dissolved oxygen data was eliminated from the calculation. If
the score change was significant enough, the resulting Health Status also changed.
Madaket Harbor
The water with the poorest “health” status is in Hither Creek at Station 1 (Table 7, 8, Figure
10). With scores of 16.7 (including oxygen data) or 24.9 (without oxygen), Station 1 scored
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the poorest of all the Madaket Harbor sampling sites in 2010. Scores for Stations 2-4 also
increased when the oxygen data were eliminated (Tables 7, 8). Station 2 at the mouth of
Hither Creek scored higher as the poor quality water from Hither Creek was diluted by cleaner
open harbor water but was still classified as Moderate with or without the oxygen data. Station
3 scored High/Moderate when the oxygen data were included but was considered High when
dissolved oxygen results were left out of the calculation (Figure 10, Tables 7, 8). Finally, the
off-shore Station 4 scored High with or with out oxygen data (Figure 10, Tables 7, 8).
Long Pond
Both Long Pond Station Index scores decreased when the oxygen data were eliminated
(Table 7,8). Water quality at both sampling sites in this poorly flushed sub-estuary to Madaket
Harbor was poor. Station 5 scored as Moderate/Fair with the oxygen data but Fair/Poor
without it. Station 6, further upstream, was classified as Fair/Poor with or without the oxygen
data (Figure 10, Table 7, 8).
Nantucket Harbor
Trophic scores at all Stations increased when dissolved oxygen data were eliminated from the
calculation (Table 7, 8). In general water quality is moderate at the Head of the Harbor off
Wauwinet (Station 3), in Polpis East (Station 6) and West (Station 5), and off of the Town
docks (Station 7), all adjacent to shore areas, streams, and/or are located in poorly flushed
areas (Figure 11). When oxygen data are eliminated from the calculation of the trophic index
score, the increase in scores at Stations 3 and 7 upgrade the Trophic Status at both sites from
Moderate to High/Moderate (Table 7, 8, Figure11). Water quality improves away from these
areas out toward mid-Harbor (Stations 1 and 2) or offshore (Stations 8 and 4) where tidal
flushing is significant (Table 7, 8, Figure 11). The health status of these sites remains high
with or without the oxygen data in the calculation.
Sesachacha Pond
At all stations in Sesachacha Pond, which is isolated from the ocean most of the year but
periodically opened for flushing, scores decrease slightly when oxygen data are not included in
the calculation of the trophic index (Table 7, 8). Water quality at Stations 1, 2 and 4 is
moderate with oxygen data included while Station 3 is Moderate/Fair (Table 7, Figure 12).
When oxygen data are eliminated, the health status of Stations 1, 3 and 4 remains the same
while that of Station 2 is down-graded to Moderate/Fair (Table 8, Figure 12).
Hummock Pond
Without dissolved oxygen data, Trophic scores decrease slightly (Figure 7, 8) but not enough
to change the health status at any of the sampling stations (Table 7, 8, Figure 13). The health
of the pond is Fair/Poor in the upper reaches at Stations 5, 7 and 8 (Figure 13), improving
slightly to Moderate/Fair further downstream at Station 3 and then to Moderate at Station 1
nearest the mouth of the estuary (Figure 13). Poor flushing helps to maintain degraded
conditions here throughout the estuary.
Miacomet Pond
As is the case with most of the estuaries in this study, trophic index scores decrease when
oxygen data are not included in the calculation Table 7, 8). With dissolved oxygen in the
calculation, the Health Status of Stations 1 and 2 is Moderate/Fair while the upper-most
Station 3 is Fair/Poor. Without oxygen, the health scores of Stations 1 and 2 decrease
enough to degrade the health status to Fair/Poor; the health score of Station 3 also decreases
but the status remains Fair/Poor. Like other degraded estuaries on Nantucket, poor flushing
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prevents nutrients and particulate matter entering the system via adjacent terrestrial sources
from being washed out by the tides and maintains poor water quality throughout.
Recommendations for Monitoring
As stated earlier, because of our concern about the dissolved oxygen data from the 2010
monitoring program and because dissolved oxygen in the water column, especially bottom
waters which are subject to periodic episodes of hypoxia/anoxia, is such an important
component in structuring aquatic ecosystems, we feel that steps should be taken to strengthen
the oxygen data base in Nantucket’s estuaries.
Two possible approaches that could help to accomplish this end are:
1) Running Winkler Titrations on water samples where meter readings of D.O. are
< 5mg/L. Winkler titration is a more accurate and precise method for quantifying
dissolved oxygen concentrations in samples expected to have low DO levels,
2) Deploying in situ oxygen meters (sondes) on the bottom of specific estuaries at
several strategic locations for the summer months when periodic hypoxic or anoxic
events in bottom waters can occur.
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Table 2. Summary of Water Quality Parameters, 2010 Nantucket Sampling Program. Values are
Station Averages of all sampling events, May-October for estuarine and harbor sites. Stream sites
were sampled once in June (see Table 1).
Station ID
Secchi
Depth
(m)
Secchi
Depth
as
% WC
20% Low
D.O. (mg/L)
20% Low
% Sat
Salinity
ppt
PO4
mg/L
NH4
mg/L
NOX
mg/L
DIN
mg/L
DON
mg/L
PON
mg/L
TON
mg/L
TN
mg/L
Total
Pig
(ug/L)
HUM1 1.4 54.4% 4.81 56.0% 7.3 0.013 0.021 0.002 0.023 0.425 0.168 0.592 0.616 12.30
HUM3 1.3 61.5% 4.99 59.8% 6.4 0.012 0.022 0.003 0.025 0.380 0.184 0.564 0.589 11.04
HUM5 0.9 44.2% 4.65 56.1% 5.3 0.015 0.020 0.003 0.023 0.430 0.313 0.743 0.766 27.03
HUM7 0.9 23.4% 3.89 45.0% 4.0 0.284 0.070 0.069 0.139 0.628 1.020 1.647 1.786 67.66
HUM8 0.7 51.0% 4.80 56.5% 4.4 0.025 0.031 0.008 0.039 0.584 0.360 0.944 0.983 33.02
LONG5 0.6 48.5% 4.77 62.9% 16.0 0.071 0.009 0.002 0.011 0.480 0.894 1.374 1.385 18.08
LONG6 0.6 48.8% 4.76 62.9% 15.9 0.028 0.022 0.003 0.026 0.567 1.452 2.019 2.044 24.21
MH1 1.6 67.1% 3.00 40.1% 26.8 0.024 0.045 0.005 0.050 0.316 0.260 0.576 0.626 14.20
MH2 1.9 93.9% 3.52 47.9% 29.7 0.014 0.024 0.003 0.027 0.264 0.145 0.409 0.436 9.37
MH3 2.3 100.0% 4.39 55.5% 30.8 0.011 0.024 0.002 0.026 0.213 0.084 0.297 0.324 6.14
MH4 3.8 58.3% 4.27 55.6% 31.1 0.015 0.024 0.002 0.026 0.190 0.069 0.259 0.285 4.21
MP1 1.5 86.3% 5.43 54.0% 0.7 0.003 0.030 0.002 0.032 0.557 0.265 0.822 0.854 16.29
MP2 1.9 58.5% 5.70 62.8% 0.6 0.002 0.044 0.002 0.046 0.554 0.210 0.764 0.811 11.50
MP3 1.3 83.1% 4.93 56.6% 0.1 0.031 0.048 0.056 0.104 0.499 0.490 0.990 1.093 51.52
NAN1 4.5 84.8% 3.57 48.2% 31.0 0.016 0.027 0.003 0.030 0.218 0.084 0.302 0.332 4.00
NAN2 3.4 62.8% 3.45 47.4% 31.0 0.018 0.016 0.003 0.019 0.201 0.077 0.278 0.297 5.36
NAN3 2.8 49.2% 3.72 52.4% 30.9 0.022 0.027 0.003 0.030 0.251 0.111 0.362 0.392 7.58
NAN4 3.7 84.5% 3.89 52.2% 29.8 0.015 0.027 0.002 0.029 0.203 0.070 0.273 0.302 4.15
NAN5 2.0 98.0% 3.18 44.3% 30.4 0.017 0.027 0.007 0.034 0.248 0.149 0.397 0.431 11.31
NAN6 2.2 88.7% 3.26 45.7% 30.5 0.016 0.024 0.004 0.028 0.277 0.133 0.410 0.438 10.31
NAN7 2.1 92.5% 3.60 49.8% 30.9 0.016 0.023 0.003 0.026 0.244 0.106 0.351 0.377 7.35
NAN8 2.4 100.8% 3.65 50.0% 31.1 0.018 0.031 0.002 0.033 0.204 0.076 0.280 0.313 3.93
SESA1 1.6 32.9% 4.82 56.4% 11.9 0.051 0.018 0.003 0.021 0.441 0.222 0.663 0.684 8.00
SESA2 1.4 28.6% 4.83 56.4% 11.9 0.045 0.024 0.003 0.027 0.469 0.219 0.688 0.715 7.19
SESA3 1.5 36.6% 4.83 56.2% 11.9 0.049 0.021 0.006 0.028 0.449 0.223 0.672 0.700 7.61
SESA4 1.5 38.7% 4.83 56.4% 11.9 0.046 0.024 0.003 0.027 0.470 0.221 0.691 0.718 6.73
82 WAUWINET ND ND ND ND 18.2 0.071 0.122 0.004 0.126 0.611 0.108 0.719 0.845 40.70
STREAM1 ND ND ND ND 0.3 0.077 0.081 0.021 0.102 1.419 0.258 1.677 1.779 2.64
STREAM4 ND ND ND ND <0.1 0.163 0.039 0.008 0.048 1.092 0.061 1.153 1.200 1.18
STREAM6B ND ND ND ND <0.1 0.006 0.059 0.004 0.064 1.701 0.374 2.076 2.139 16.37
STREAM6C ND ND ND ND <0.1 0.132 0.097 0.003 0.100 0.375 0.156 0.532 0.632 7.41
STREAM8 ND ND ND ND 3.3 0.015 0.045 0.005 0.050 0.398 0.118 0.516 0.565 5.29
Secchi as % of WC is the % of the water column above the secchi depth, values of 100% means that the Secchi was at or below the bottom.
Lowest 20% of D.O. records for a site over the project period.
HUM = Hummock Pond, Long = Long Pond, MH = Madaket Harbor, MP = Miacomet Pond, NAN = Nantucket Harbor, SESA = Sesachacha Pond
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Hummock Pond Total N Gradient
0
0.5
1
1.5
2
2.5
7 8 5 3 1 upstream Station Number downstreamN Conc. (mg/L)TN
DIN
DON
PON
Long Pond Total N Gradient
0
0.5
1
1.5
2
2.5
6 5
upstream Station Number downstreamN Conc. (mg/L)TN
DIN
DON
PON
Sesachacha Pond Total N Gradient
0
0.5
1
1.5
2
2.5
3 2 4 1
Station Number N Conc. (mg/L)TN
DINDON
PON
Nantucket Harbor: Harbor Total N Gradient
0
0.5
1
1.5
2
2.5
3 6 5 2 7 1 8 4
Station Number N Conc. (mg/L)TN
DIN
DON
PON
Polpis Mid Harbor Town Harbor Entrance
Wauwinet
Miacomet Pond Total N Gradient
0
0.5
1
1.5
2
2.5
3 1 2
upstream Station Number downstreamN Conc. (mg/L)TN
DIN
DON
PON
Madaket Harbor Total N Gradient
0
0.5
1
1.5
2
2.5
1 2 3 4
Station Number N Conc. (mg/L)TN
DIN
DON
PON
Madaket Ditch
Off Shore
Figure 6. Comparison of nitrogen species in the Nantucket estuaries
18
Figure 7. Estuarine water quality monitoring station locations in the Nantucket Harbor
estuary system. Station labels correspond to those provided in Table 3 below. Red diamonds
indicate locations of MEP monitoring stations. Blue diamonds show locations of Town sampling
sites.
. Table 3. Comparison of MEP mean values of TN with Town TN data (all values are mg/L)
from Nantucket Harbor. MEP data were collected in the summers of 1988 through 1990
and 1992 though 1994 by the Woods Hole Oceanographic Institution (WHOI), and between
1992 and 2005 by the Town of Nantucket Marine Department. Town data were collected
in the summer of 2010 by the Town of Nantucket Marine Department
Sub-Embayment
monitoring
station
Historical
MEP
Mean TN
(mg/L) s.d.
2010
Town
ID
2010
Mean TN
(mg/L)
Head of the Harbor - Upper 2 0.408 0.188 NA Not Sampled
Head of the Harbor - Mid Town 3 0.401 0.115 3 0.392
Head of the Harbor - Lower 2A 0.339 0.070 NA Not Sampled
Pocomo Head 3 0.335 0.081 NA Not Sampled
Quaise Basin 3A+Town 2 0.336 0.112 2 0.297
East Polpis Harbor 4+Town 6 0.362 0.105 6 0.438
West Polpis Harbor 4A+Town 5 0.388 0.119 5 0.431
Abrams Point 5 0.335 0.060 NA Not Sampled
Monomoy 6 0.297 0.086 NA Not Sampled
Mooring Area 7+Town 1,1A 0.326 0.106 1, 7 0.377
Nantucket Sound OS+Town 4 0.239 0.041 4 0.302
19
Figure 8. 2005 aerial photo showing MEP monitoring station location in Sesachacha Pond
that was used in the water quality analysis.
Sampling Station
Location
Historical
MEP
Mean TN
(mg/L)
s.d.
2010
Mean TN
(mg/L)
Sesachacha Pond 1.197 0.078 0.684
Table 4. Comparison of MEP mean values of TN with Town TN
data (all values are mg/L) from Sesachacha Pond. MEP data
were collected in the summers of 1992 through 2005. Town data
were collected in the summer of 2010 by the Town of Nantucket
Marine Department.
20
Figure 9. Estuarine water quality monitoring station locations in the Madaket Harbor and Long
Pond Systems.
Table 5. Comparison of MEP mean values of TN with Town TN data (all values are mg/L)
from Madaket Harbor and Long Pond. MEP data were collected by SMAST in the summers
of 2002 through 2004. Town data were collected in the summer of 2010 by the Town of
Nantucket Marine Department.
Sub-Embayment Monitoring station
Historical
MEP
Mean TN
(mg/L) s.d.
2010
Mean TN
(mg/L)
Madaket Harbor MEP M1 0.336 0.098
Madaket Harbor Town 4 0.285
Madaket Harbor MEP M2 0.395 0.083
Madaket Harbor Town 2 0.436
Madaket Harbor MEP M3 0.415 0.090
Madaket Harbor Town 3 0.324
Hither Creek MEP M4 0.581 0.193
Hither Creek MEP M5 0.780 0.178
Madaket Harbor MEP M6 0.347 0.067
Madaket Harbor MEP M10 0.422 0.127
Hither Creek MEP M11+Town 1 0.620 0.215 0.626
Long Pond MEP LOPO1 1.058 0.404
Long Pond MEP LOPO2+Town 5 0.971 0.369 1.385
Long Pond MEP LOPO3 0.924 0.234
Long Pond MEP LOPO4+Town 6 0.894 0.278 2.044
North Head Long Pond MEP LOPO5 0.954 0.271
21
2010 2005/2007
TN
(mg/L)
TN
(mg/L) Station
ID Mean Mean S.D.
HUM1 0.616 0.751** 0.374
HUM3 0.589 0.630** 0.388
HUM5 0.766 ND ND
HUM7 1.786 1.283** 0.969
HUM8 0.983 ND ND
MP1 0.854 0.842* 0.191
MP2 0.811 0.855* 0.213
MP3 1.093 0.280* 0
*2005 data only
**2007 data only
Table 6. Comparison of TN concentrations collected in 2005
(Miacomet Pond) and 2007 (Hummock Pond) by Nantucket
Marine Department with Town TN data collected at both sites
the summer of 2010. All values are mg/L.
22
ID
Secchi
SCORE
Low20%
Oxsat
SCORE
DIN
SCORE
TON
SCORE
T-Pig
SCORE
EUTRO
Index Health Status
HUM1 54.0 41.6 100.0 4.3 2.4 40.4 Moderate
HUM3 48.5 49.6 75.2 8.2 0.0 36.3 Moderate-Fair
HUM5 25.9 41.7 77.7 0.0 0.0 29.0 Fair-Poor
HUM7 22.4 14.5 0.4 0.0 0.0 7.4 Fair-Poor
HUM8 12.2 42.6 55.2 0.0 0.0 22.0 Fair-Poor
LONG5 0.6 55.8 100.0 0.0 0.0 31.3 Moderate-Fair
LONG6 4.6 55.8 73.9 0.0 0.0 26.8 Fair-Poor
MH1 59.0 0.3 44.5 5.4 0.0 21.8 Fair-Poor
MH2 72.8 22.3 70.7 50.3 5.4 44.3 Moderate
MH3 83.3 40.5 72.7 92.1 40.5 65.8 High-Moderate
MH4 100.0 40.5 72.4 100.0 71.8 77.0 High
MP1 54.8 37.1 63.7 0.0 0.0 31.1 Moderate-Fair
MP2 70.3 55.6 47.9 0.0 0.0 34.8 Moderate-Fair
MP3 47.1 42.8 12.9 0.0 0.0 20.6 Fair-Poor
NAN1 100.0 23.0 66.7 90.1 76.1 71.2 High
NAN2 100.0 20.9 87.2 100.0 51.8 72.0 High
NAN3 95.5 33.4 66.4 66.3 23.0 56.9 Moderate
NAN4 100.0 32.8 68.0 100.0 73.0 74.8 High
NAN5 74.8 12.5 62.1 54.1 0.0 40.7 Moderate
NAN6 81.7 16.6 69.8 49.9 0.0 43.6 Moderate
NAN7 78.1 27.1 72.3 70.4 25.6 54.7 Moderate
NAN8 86.7 27.5 62.3 100.0 77.6 70.8 High
SESA1 62.1 42.3 82.2 0.0 18.5 41.0 Moderate
SESA2 54.3 42.3 71.4 0.0 27.4 39.1 Moderate
SESA3 55.9 42.0 70.2 0.0 22.7 38.2 Moderate-Fair
SESA4 54.8 42.5 71.3 0.0 32.9 40.3 Moderate
High Quality = >69; High/Moderate = 61-69; Moderate = 39-61; Moderate/Fair = 31-39;
Fair/Poor = <31
Table 7. Trophic Health Index Scores and status for water quality monitoring stations in
Nantucket estuaries based upon open water embayment (not salt marsh) habitat quality
scales (described in Howes et. al., 1999 at www.savebuzzardsbay.org).
23
ID
Secchi
SCORE
DIN
SCORE
TON
SCORE
T-Pig
SCORE
EUTRO
Index Health Status
HUM1 54.0 100.0 4.3 2.4 40.1 Moderate
HUM3 48.5 75.2 8.2 0.0 33.0 Moderate-Fair
HUM5 25.9 77.7 0.0 0.0 25.9 Fair-Poor
HUM7 22.4 0.4 0.0 0.0 5.7 Fair-Poor
HUM8 12.2 55.2 0.0 0.0 16.9 Fair-Poor
LONG5 0.6 100.0 0.0 0.0 25.2 Fair-Poor
LONG6 4.6 73.9 0.0 0.0 19.6 Fair-Poor
MH1 59.0 44.5 5.4 0.0 27.2 Fair-Poor
MH2 72.8 70.7 50.3 5.4 49.8 Moderate
MH3 83.3 72.7 92.1 40.5 72.1 High
MH4 100.0 72.4 100.0 71.8 86.1 High
MP1 54.8 63.7 0.0 0.0 29.6 Fair-Poor
MP2 70.3 47.9 0.0 0.0 29.6 Fair-Poor
MP3 47.1 12.9 0.0 0.0 15.0 Fair-Poor
NAN1 100.0 66.7 90.1 76.1 83.3 High
NAN2 100.0 87.2 100.0 51.8 84.7 High
NAN3 95.5 66.4 66.3 23.0 62.8 High-Moderate
NAN4 100.0 68.0 100.0 73.0 85.3 High
NAN5 74.8 62.1 54.1 0.0 47.8 Moderate
NAN6 81.7 69.8 49.9 0.0 50.4 Moderate
NAN7 78.1 72.3 70.4 25.6 61.6 High-Moderate
NAN8 86.7 62.3 100.0 77.6 81.7 High
SESA1 62.1 82.2 0.0 18.5 40.7 Moderate
SESA2 54.3 71.4 0.0 27.4 38.3 Moderate-Fair
SESA3 55.9 70.2 0.0 22.7 37.2 Moderate-Fair
SESA4 54.8 71.3 0.0 32.9 39.8 Moderate
High Quality = >69; High/Moderate = 61-69; Moderate = 39-61;
Moderate/Fair = 31-39; Fair/Poor = <31
Table 8. Trophic Health Index Scores and status for water quality monitoring stations
in Nantucket estuaries based upon open water embayment (not salt marsh) habitat quality
scales. Index calculated without Dissolved Oxygen data (described in Howes et. al., 1999
at www.savebuzzardsbay.org).
24 Figure 10. Madaket Harbor Eutrophication Index 2010.
25 Figure 11. Nantucket Harbor Eutrophication Index 2010.
26 Figure 12. Sesachacha Pond Eutrophication Index 2010.
27 Figure 13. Hummock Pond Eutrophication Index 2010.
28
Figure 14. Miacomet Pond Eutrophication Index 2010.