Nutrients and Pollution in Neponset
Estuary (but not really)
Kenly
Outline
Introduction
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Nutrients/gas
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Bacteria
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PCBs
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Metal
What do we know?
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Nutrients/gas
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Bacteria
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PCBs
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Metal
What do we need to find out?
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Nutrients/gas
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Bacteria
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PCBs
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Metal
Why are Nutrients Important?
• Nutrients like N and P limit primary
production in aquatic systems. In estuaries, N
is usually the limiting nutrient (Herbert, 1999).
• Adding more of this limiting nutrient increases
primary production, so understanding the
amount of nutrient-loading that’s taking place
in Neponset is key to understanding the
health of the system.
Why is adding N so bad?
• Throws off balance between production,
recycling, and fixation.
• Blooms, followed by anoxia (eutrophication,
Vitousek et al, 1997).
• Bye bye, eelgrass.
Why do we care about nutrients in
Neponset?
• Affects water quality. Amount of nutrient loading
taking place has big impacts on dissolved oxygen
concentrations and primary production.
• Primary production in turn has effects on trophic
structure in the rest of the estuary.
Phytoplankton diversity drops, eelgrass and
scallops disappear, and so on (Cosper et al, 1987).
• “decrease in species diversity [of eelgrass] along
the eutrophication gradient and over time “
- Cardoso et al, 2003
Look what happened in Waquoit!
Bacteria!
• Bacteria from leaky septic or sewer systems can leach
into estuaries. These pathogens lead to an increase in
waterborne gastroenteritis and therefore have hazardous
effects on human health (EPA 2008).
• bacteria can be harmful to the environment because
waste expelled into an estuary is broken down by
microbes, which then deplete the oxygen in the system
just like the decomposition of dead phytoplankton that
was discussed earlier (EPA 2008).
Pollution…it ain’t no joke
• Polychlorinated biphenyls come from disposal of
waste from machining, painting, electronics, etc
(Brealt, 2011).
• Known to disrupt many systems in the body including
immune and endocine (EPA.gov).
Heavy metals…they’re pretty cool : O
• Mercury deposition has increased worldwide (Fry and Chumchal,
2012), and this can lead to a buildup of Hg in sediments.
• Depending on microbial community composition, this mercury can
be methylated by sulfate reducing bacteria to methylmercury (Auer
et al. 2009). This form is much more toxic (Hammerschmidt and
Fitzgerald, 2004).
• Cadmium and lead are also hazardous to human health. Cadmium
emissions from batteries can leach into estuaries and can cause
kidney damage if ingested (Jarup, 2003). Lead is related mainly to
road transport (it used to be in gasoline) and is widespread over
many types of ecosystems (Jarrup, 2003). These three metals are
the most toxic and can all be harmful on human health when eaten
(Jarup, 2003).
• Mercury and cadmium are particularly toxic to eelgrass.
Outline
Introduction
•
Nutrients/gas
•
Bacteria
•
PCBs
•
Metal
What do we know?
•
Nutrients/gas
•
Bacteria
•
PCBs
•
Metal
What do we need to find out?
•
Nutrients/gas
•
Bacteria
•
PCBs
•
Metal
So what’s the status?
• No idea. The vast, vast majority of the focus is
on the river…there is only one sampling site in
the estuary itself and I couldn’t even find the
data for that. So…what do we know about
nutrients and pollution in the river?
Nutrients
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There are many sources of excess nutrients in the Neponset watershed. Fertilizer,
animal waste, runoff from impervious surfaces, direct input of grass clippings from
lawns and golf courses, leaky sewers, bad septic systems, and dams all contribute
excess nutrients to the system (Neponset.org).
ammonia concentrations are below the chronic water quality criteria for ammonia.
Concentrations ranged from 0-0.295 mg/L, which is normal.
The MWRA found that nitrate and nitrite (reported combined) in the river mouth
ranges from 1-12 uM mostly, with some spikes reaching up to 30uM.
Concentrations in the river itself were much higher, ranging from 20-60 uM in
some sites
39% of sampling sites exceeding accepted nitrogen concentrations (Neponset.org).
Phosphorus levels never exceeded 2uM, according to the MWRA website, which is
fine in terms of the estuary because P is not the limiting nutrient there.
Neponset isn’t dammed; there is good flushing and lots of marsh to filter pollution.
Might not be so terrible (MWRA website).
DO
• Near Foxboro/Canton the lowest DO is 6.6mg/L,
and at Mother Brook only 15 of 397 samples
taken had DO concentrations lower than 5mg/L
(Boston Harbor Watershed, 1999).
• The section with the lowest DO was closest to the
estuary, in the Milton to Dorchester Bay region.
It went as low as 0.5mg/L at some sampling sites,
but it was highly variable, with some sites
showing percent saturations of over 124%
(Boston Harbor Watershed, 1999).
Bacteria
• Reductions in bacteria loads from 72-99% are called for
to even meet total maximum daily loads.
• These stations that don’t meet water quality standards
have 200 or more organisms per 100ml sample, or
more than 10% of samples from a station have counts
exceeding 400 organisms/100ml.
• the areas of the estuary that are more developed have
higher bacteria levels. This is usually due to leaking or
illicit sewer connections. These issues become worse
in wet weather as storm runoff flushes materials from
pipe drainage systems.
Metals and PCBs
• Some segments of the Neponset River show
contamination of heavy metals from
wastewater discharge from companies that
dump waste into the river (Boston Water
Quality Report, 1999).
• Hg, Cd, Ni, Cu, Cr, and Pd are all elevated .
• Concentrations of PCBs have been found to be
as high as 26,000 mg/kg of sediment and
0.05-12 ug/L in groundwater (Brealt, 2011).
Outline
Introduction
Water quality
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Nutrients/gas
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Bacteria
Toxins
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PCBs
•
Metal
What do we know?
Water quality
•
Nutrients/gas
•
Bacteria
Toxins
•
PCBs
•
Metal
What do we need to find out?
Water quality
•
Nutrients/gas
•
Bacteria
Toxins
•
PCBs
•
Metal
Future directions
• The Neponset Estuary is very neglected compared to
its river. There is only one sampling site in the estuary,
so water quality data is virtually non-existent. Nitrogen
is most likely the limiting nutrient in this system, so we
need to know how much nitrogen and subsequent
primary production is in the estuary.
• This will allow us to determine whether nitrate
concentrations in the watershed are contributing to
eutrophication in the estuary itself. Knowing DO levels
will be helpful too, because it will tell us if
eutrophication-induced hypoxia or anoxia is occurring.
Future directions continued
• Stations could be set up around the estuary
perimeter as well as across the estuary itself
along several gradients and depths to ensure
that all variations are captured. There are
plenty of boaters in Neponset. If we can get
volunteers to measure water quality along the
river, we can probably get some for the
estuary as well.
References
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Breault, R.F., 2011, Concentrations, loads, and sources of polychlorinated biphenyls, Neponset River
and Neponset River Estuary, eastern Massachusetts: U.S. Geological Survey Scientific Investigations
Report 2011–5004, 143 p
Cosper, E.M. et al. 1987. Recurrent and persistent brown tide blooms perturb coastal marine
ecosystem. Estuaries and Coasts 10: 284-290.
Herbert, R.A. 1999. Nitrogen cycling in coastal marine ecosystems. FEMS Microbiology Reviews 23:
563-590.
Huang, W, and R. Chen. 2009. Sources and transformations of CDOM in the Neponset River
watershed. Journal of Geophysical Research 114.
Perry, S.L. 2009. More Than One River: Local, Place-Based Knowledge and the Political Ecology of
Restoration and Remediation Along the Lower Neponset River, Massachusetts. UMass Amherst
Dissertations and Theses.
Vitousek, P.M. et al. 1997. Human alteration of the global nitrogen cycle: sources and
consequences. Ecological Applications 7: 737-750.
Total maximum daily loads of bacteria for Neponset river basin. Mass. Dept. of Environmental
Protection. http://www.mass.gov/dep/water/resources/neponset.pdf
Neponset river subwatershed river and estuary segment assessments. Boston Harbor Watershed
1999 Water Quality Assessment Report