Estuaries 101
A Brief Introduction to Natural and
Human-Induced Processes in Estuaries
Jonathan Pennock
University of New Hampshire
Marine Program, NH Sea Grant & Jackson Estuarine Laboratory
What Are Estuaries and Why
Should 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
Eutrophication
Positive Versus Negative Effects
Oligotrophic
Phytoplankton
Zooplankton
Pelagic Fish
Bottom Oxygen
Benthos
Benthic Fish
Mesotrophic
Eutrophic
Dystrophic
Population Increase
Population (Millions)
10000
8000
World Total
6000
Europe, Russian,
and The Americas
4000
Rest of Asia
and Oceana
China
2000
0
1700
Africa
1750
1800
1850
1900
1950
2000
2050
Year
Adapted from Nixon, 1994
Land Clearing
Land Clearing
& Agriculture
Fertilizer Production
6
Fertilizer (10 tons)
140
120
Mining of Phosphate Rock
100
80
Synthesis of
Nitrogen Fertilzer
60
40
20
0
1880
1900
1920
1940
1960
1980
2000
Year
Adapted from Nixon, 1994
Intensive Agriculture
Point Source Inputs
Headlines from Other Regions
[We are Not Alone in Our Concerns…]
A Case Study In Nutrient Biogeochemistry Research
Mobile Bay, Alabama – Sorting Through Variability
Mobile Bay
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%
#
#
#
#
#
#
#
#
#
#
#
Lower
NO3 (M)
Upper
25
25
25
20
20
20
15
15
15
10
10
10
5
5
5
0
0
J F M A M J J A S O N D
Coastal
0
J F M A M J J A S O N D
Month
J F M A M J J A S O N D
NOAA Estuarine Eutrophication Assessment
Bricker 1999
Environmental Protection Agency
Thank You!