1. Overview of Epipelagic Food Webs
2. Trophic Structure
3. Microbial Loop
4. Phytoplankton Blooms
5. Upwelling and Productivity
6. Zooplankton Blooms

Epipelagic Food Webs

1. Photosynthesis based food webs
2. Phytoplankton and zooplankton
3. About 75 percent of food produced in the epipelagic zone is consumed there
4. Nekton of surface marine mammals, sea turtles, fishes, and squid
5. Sardines, anchovies, and herrings are important planktivores

Epipelagic Producers

1. Producers = Phytoplankton

Epipelagic Consumers

1. Primary (1st ^degree) Consumers = Herbivorous Zooplankton and Small Fish
2. Secondary (2nd ^degree) Consumers = Carnivorous Zooplankton and Small Fish
3. Tertiary (3rd ^degree) Consumers = Large Carnivorous Zooplankton, Squid and Fish
4. Quartenary (4^{th degree}) and Higher Level Consumers = Large Fish and Squid

Pinnipeds

1. Eat zooplankton, fish, squid and penguins

Whales

1. Toothed Whales eat fish, squid, penguins and other marine mammals
2. Baleen Whales eat zooplankton and fish

Seabirds

1. Fish are important in the diet but are not the only food
2. Fifteen percent of species feed principally on zooplankton
3. Sixty six percent of species feed on zooplankton occasionally
4. Six percent of species feed exclusively on squid
5. Twenty eight percent of species feed on squid occasionally

Dissolved Organic Matter (DOM)

1. Organic matter in solution (molecular size)
2. DOM leaks out of phytoplankton cells
3. DOM is excreted by zooplankton as waste

Major Energy Pathway

1. DOM renters the food web when it is used by bacteria
2. Bacteria are eaten by protozoa
3. Protozoa are eaten by zooplankton

Marine Snow

1. Detritus colonized by bacteria form flakes of organic material
2. Many zooplankton and small fishes eat marine snow

Blooms

1. Dramatic increases in population size
2. Population size is measured as density or concentration in numbers of phytoplankters per liter of seawater
3. Determined by rates of reproduction and by death rates

Requirements for Growth and Reproduction

1. Excess biochemical building blocks are used for the production of new cellular materials enabling cell growth and reproduction
2. Carbon dioxide, water, and sunlight are needed to make sugars by photosynthesis
3. Nitrogen, Phosphorus and other inorganic nutrients are needed to convert sugars into lipids, proteins, and nucleic acids

Abiotic Effects

1. Phytoplankton population growth is effected by:

   A. Light intensity

   B. Temperature

   C. Nitrogen and Phosphorus concentrations

Seasonal Fluctuations

1. Light, temperature and nutrients change in a seasonal pattern in temperate and polar waters
2. Phytoplankton population sizes also fluctuate seasonally

Temperate Spring Bloom

1. Surface waters experience increases in temperature and light intensity
2. Nitrogen and Phosphorus concentrations are high
3. Phytoplankton populations increase rapidly to a maximum size

Summer Low

1. Although temperature and light intensity are high Nitrogen and Phosphorus concentrations diminish due to depletion by phytoplankton
2. Mixing of deep and surface waters is at a minimum so there is little replacement of Nitrogen and Phosphorus from below

Summer Stratification

1. Surface waters warmed by the sun have a lower density than cold deep waters
2. There is little mixing at the boundary between these water masses

Fall Turnover

1. Surface waters cool as temperatures drop and its density becomes more like that of the cold deep waters
2. Renewed mixing brings Nitrogenand Phosphorus to the surface

Fall Bloom

1. Surface waters are still warm from the summer and light intensities are still high
2. Nitrogen and Phosphorus concentrations are increasing
3. Phytoplankton populations increase

Fall Bloom is Minor

1. Temperatures and light intensities are declining
2. The Fall population does not reach the same size as the Spring

Winter Low

1. Surface waters are cold and mixing brings more Nitrogen and Phosphorus to the surface
2. Phytoplankton populations decline despite an abundance of nutrients
3. Temperature and light intensity are low

Responses of Species

1. The population of each species blooms at a particular time in response to its particular temperature, light and nutrient needs
2. There is a gradual replacement of one population by another

Arctic Blooms

1. There is a single summer bloom
2. Temperature and light intensity reach levels that support a
3. bloom during the summer only

Tropical Phytoplankton

1. Tropical water conditions are always like the summer of temperate waters with phytoplankton populations low
2. There are no blooms without the replenishment of Nitrogen and Phosphorus

Upwelling

1. Upward movement of cold, nutrient rich water from below to the surface
2. Upwelling is the result of Coriolus forces acting upon ocean currents
3. Ex. West coast of the Americas

Upwelling and Phytoplankton

1. Tropical areas with upwelling have conditions which produce a state of constant bloom
2. Temperate areas with summer upwelling have prolonged bloom conditions

El Nino (El Pintor)

1. Cessation of upwelling caused by changes in current producing forces

Zooplankton Blooms

1. Zooplankton populations fluctuate in size
2. Maximum population sizes are reached following peaks in the phytoplankton populations

Temperate Spring Bloom

1. There is a single early summer bloom
2. Following the spring phytoplankton bloom

Arctic Blooms

1. There is a single late summer bloom
2. Following the early summer phytoplankton bloom

Tropical Zooplankton

1. Zooplankton populations are low year round because phytoplankton populations are low year round
2. There are no blooms without the replenishment of Nitrogen and Phosphorus

Upwelling and Zooplankton

1. Tropical areas with upwelling have conditions which produce a state of constant zooplankton and phytoplankton bloom
2. Temperate areas with summer upwelling have prolonged zooplankton bloom conditions

Upwelling and Fisheries

1. The majority of the fish consumed by humans are caught in upwelling areas where there is plenty of fish food produced by plankton blooms