Estuaries 101A Brief Introduction to Natural
and Human-Induced Processes in
Estuaries
Jonathan PennockUniversity of New Hampshire
Marine Program, NH Sea Grant & Jackson Estuarine Laboratory
What Are Estuaries and WhyShould We Care About Them?• Semi-enclosed bodies of water where fresh water & salt water mix…
• Estuaries are critical habitats for many ecologically and economically
important coastal species…
• Estuaries are natural biological and geochemical reactors…
• While net flow is almost always from the land to the sea, tidal influences
and often two-layered flow tend to retain materials in estuaries…
• In most, but not all estuaries, freshwater input from the watershed is
the major source of nutrients, contaminants, suspended sediments, etc…
• The sources of these inputs varies, however, with ‘point-sources’ from
specified inputs and ‘non-point sources’ from varied sources such as
precipitation, agriculture, septic tanks and groundwater contributing…
• Different estuaries have differing capacities to cope with human
perturbations based on their physical and geological make-up…
What are the Most Critical Factors Impacting Estuaries?
• Habitat Loss
• Bacterial Contamination
• Chemical Contaminants
• Loss of Keystone Species
• Sediment Inputs
• Nutrient Over-Enrichment
• Micro-algae and Macro-algae Overgrowth
• Hypoxia & Anoxia
NOAA Eutrophication Model
Bricker 1999
EutrophicationPositive Versus Negative Effects
Oligotrophic MesotrophicEutrophic Dystrophic
Phytoplankton
Zooplankton
Pelagic Fish
Bottom Oxygen
Benthos
Benthic Fish
Year
1700 1750 1800 1850 1900 1950 2000 2050
Popu
latio
n (M
illio
ns)
0
2000
4000
6000
8000
10000
World Total
Africa
China
Rest of Asiaand Oceana
Europe, Russian,and The Americas
Population Increase
Adapted from Nixon, 1994
Land Clearing
Land Clearing& Agriculture
Fertilizer Production
Year1880 1900 1920 1940 1960 1980 2000
Ferti
lizer
(10
6 tons
)
0
20
40
60
80
100
120
140
Mining of Phosphate Rock
Synthesis of Nitrogen Fertilzer
Adapted from Nixon, 1994
Intensive Agriculture
Point Source Inputs
Headlines from Other Regions[We are Not Alone in Our Concerns…]
Mobile Bay
A Case Study In Nutrient Biogeochemistry Research
Mobile Bay, Alabama – Sorting Through Variability
#
#
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#
#
##
#
#
#
Dog River Fowl River Weeks Bay
Developed 24.6% 1.7% 0.8%
Forested 39.7% 41.2% 29.8%
Agriculture 20.3% 33.4% 59.9%
Wetland 11.2% 18.5% 5.6%
J JF JM MA A S O N D
Upper
0
5
10
15
20
25Lower
NO
3 (
M)
0
5
10
15
20
25Coastal
Month
0
5
10
15
20
25
J JF JM MA A S O N D J JF JM MA A S O N D
NOAA Estuarine Eutrophication Assessment
Bricker 1999
Environmental Protection Agency
Thank You!