“The Edge of the Sea Is a Strange and Wonderful Place.”
Rachel Carson

Overview of Coastal Ecology
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Coastal Ecosystems
Ecosystem – a stable, interactive system, comprised of a biotic (living) community
dependent upon the abiotic (non-living) environment
Examples of coastal ecosystems:
Estuaries, salt marshes & mangrove swamps
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Differences in Coasts
Coastal flood plains (width and extent of coverage)
Presence or absence of rock formations (rock pools, cliffs, bluffs, etc.)
Dynamics of estuaries (tidal flux, flooding characteristics, biotic diversity is high in shallow sediments)
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Land Formations in the United States
(Illustration)

Ocean Divisions
Pelagic Division (water column of the ocean)
Benthic Division (ocean bottom and sediments)
Ocean bottom and sediments
Additional zones (three criteria)
Distance from the land
Light availability
Depth
Ocean Divisions and Zones
(Illustration)

Types of Coastal Ecosystems
Estuaries (basins with mixed salinity)
Salt Marshes (shallow water area, grasses e.g., Spartina, soft benthos, snails, birds, clams, etc.)
Mangrove Swamps (flooded woodlands)
Rocky Shores (rock outcroppings, exposed rock pools)
Sandy Beaches (flatlands, lower diversity)
Intertidal Zone (area between low & high tide; extremes of temperature, moisture and salinity)
Coral Reefs (Complex, highly diverse, tropical)
Kelp Forests (Found in deeper water, brown algae)
Pathways & Flows
Linkages between abiotic and biotic components of coastal ecosystems
Nutrients for plants and algae
Nitrates (NO₃)
Phosphates (PO₄)
Sulfates (SO₄)
Trophic interactions (food chains)
Energy Flow
Photosynthesis (plant & algal cells)
6C0₂ + 6H₂0 = C₆H₁₂O₆ + 60₂
Respiration (all living organisms)
C₆H₁₂O₆ + 0₂  = 6C0₂ + 6H₂0
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Food Chains
Producers (autotrophs)
Producers are usually the smallest size organisms within an ecosystem; trees are an exception
Photosynthesis releases oxygen back to the environment
Carbon fixation helps to recycle CO₂ from the atmosphere and seawater
Output of organic compounds (C-H) produced during photosynthesis is called primary productivity
Herbivores (heterotrophs)
Feed on producers
Usually larger than producers, but exist in smaller numbers (trophic pyramid)
Serve as food (prey) for carnivores (predators)
Carnivores (heterotrophs)
Feed on herbivores
Usually larger than herbivores, with populations smaller than those of the herbiores
(trophic pyramid); baleen whales are an exception
1^o carnivores serve as food (prey) for 2^o carnivores (predators)
May be several layers of carnivores within a given ecosystem (e.g., in marshes)
Decomposers (heterotrophs)
Also called detritovores
Feed on detritus (dead organisms or products of living creatures) and waste products
Often very small microorganisms (bacteria, viruses, molds, protozoa, invertebrates)
May serve as food for other consumers in the ecosystem (e.g., larvae eaten by fish)

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Grazing food chain
Based on photosynthesis as a source of energy
Comprised of producers, consumers, and decomposers
Important in the planktonic community (floating organisms), found in the photic zone of marine ecosystems
Detritus food chain
Based on decomposition of detritus as a source of energy
Comprised of detritovores
Especially important in the benthos (bottom sediments)
Food Webs
Most ecosystems are characterized by complex food webs
Trophic dynamics may include predation, parasitism, and other interdependent relationships
Feeding behaviors may be elaborate and adaptive (e.g., attack and avoidance strategies such as armor or camouflage)

Illustration of Food Webs

Trophic Pathways in the Pelagic Environment of Florida Bay

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Biogeochemical Cycles
Chemicals move through biotic communities in recurring cycles
Reservoirs may be sedimentary (earth’s surface), or gaseous (atmospheric)
Pollutants can move through the same pathways (e.g., DDT or mercury following the carbon cycle)
Hydrologic Cycle
Water vapor formation via evaporation is highest in tropical regions
Water vapor moves from equator to the poles, then cools and falls back to earth as precipitation
Sea salt provides precipitation nuclei
Land runoff carries chemicals and sediments into oceans
Hydrological Cycle
(Illustration)

Carbon Cycle
Follows food web dynamics
CO₂ generated through cell respiration is raw material for photosynthesis
Dissolved carbon dioxide forms bicarbonate ions
CO₂ + H₂O ---> H₂CO₃ ---> H⁺ + HCO₃^-
Calcium carbonate occurs in marine shells
Calcium carbonate from shells can accumulate to form limestone
Marine sediments from the past helped to form deposits of fossil fuels (e.g., petroleum, natural gas)
Oxidation of fossil fuels releases heat, CO2
Sulfur dioxide, nitrogen oxides released
Carbon Cycle
(Illustration)

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Nitrogen Cycle
Producers commonly utilize ammonia (NH₃), nitrite (NO₂), or nitrate (NO₃)
Conversion to amino acids (precursors of proteins)
Animals excrete nitrogen as ammonia, urea, or uric acid
Bacterial degradation of animal wastes
Atmospheric reservoir of nitrogen (~79% of air at surface)
Sources of nitrates
Electrical discharges during thunderstorms
Nitrogen fixation by microorganisms such as cyanobacteria in oceans
Runoff from land (agricultural, residential) may contain nitrogen compounds

Nitrogen Cycle
(Illustration)

Phosphorus Cycle
Producers commonly utilize soluble phosphates (PO₄)
Conversion in living organisms to calcium apatite (teeth, bones), adenosine triphosphate,
ATP (used in photosynthesis and cell respiration),
and in nucleic acids (DNA, RNA) for transfer of genetic information.
Sedimentary reservoir of phosphorus (rocks, ocean sediments)
Sources of phosphates
Weathering of rocks
Microbial conversion of dead organisms
Runoff from land (agricultural, residential) may contain phosphorus compounds
Loss of phosphorus in marine systems (sinking from the photic zone into the sediments)
Off the coasts of California and Peru, large quantities of nutrient-laden materials sink
Upwelling currents bring nutrients back to surface
(e.g., 50% of world’s commercial fish catch – 0.1% of ocean’s surface)

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Phosphorus Cycle (For Illustration, see textbooks)

Sea Salt Cycle (For illustration, see textbooks)

Mercury Cycle
Mercury often released into marine ecosystems as an industrial byproduct (waste)
Bacterial methylation (attaching CH³ to the mercury) produces methylmercury in sediments
Bioaccumulation (or biomagnification) of mercury through the food chain
Methylmercury can accumulate in the tissues of pilot whales (long-distance migration patterns)
Pilot whales may be consumed by humans (e.g., Faroe Islands off the Danish coast)
Cause damage to neurological system

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