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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#

#

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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!