1. Communities and Ecosystems
2. Community Structure
3. Ecosystem Structure
4. Energy and Nutrients
5. Productivity
6. Zonation

Community

1. Definition: A community is a group of interacting populations living in the same area
2. All of the various species in a single locale
3. Often named after the dominant species

   A. Ex. Mussel Bed

   B. Ex. Coral Reef

   C. Ex. Sargassum Rafts

Ecosystem

1. Definition: An ecosystem is a group of interacting communities living in the same region and the physical environment in which they live
2. Ex. Tropical Nearshore Ecosystem consisting of a coral reef community, a seagrass community, and a mangrove community
3. A total environment, biotic and abiotic, that is somewhat self-contained and self-sustaining

   A. Requires an input of energy and materials to sustain life

   B. Capable of recycling elements reducing demand for them

Community Structure

1. Definition: The characteristics of a community

Species Composition

1. Definition: The particular species found in a community

Species Diversity

1. Definition: A measure of the types of different species encountered in a habitat
2. Species diversity (H) is computed mathematically and is influenced by two components: species richness (S) and species evenness (J)
3. Species richness (S) is the number of species present in a community
4. Species evenness (J) is how evenly individuals are distributed among the species

Example of Species Diversity

1. Compare Fig. 1 and Fig. 2 below.
2. The two rocky shores, in these hypothetical examples, have the same species richness but the Gulf shore in Fig.1 has a lower species evenness than the Pacific shore in Fig. 2 and thus a lower species diversity.
3. An observer on the Gulf shore would be most likely to encounter Chthamalus fissusand overlook the other four species. Whereas, an observer on the Pacific coast is just as likely to encounter any of the five species.

Fig. 1 Hypothetical Data from Gulf of California Rocky Shore

Species	Numbers per Square Meter
Chthamalus fissus	200
Pilumnus limnosus	10
Acanthina angelica	10
Clibinarius digueti	10
Turbo fluctuosus	10
S=5

Fig. 2 Hypothetical Data from Pacific Coast Rocky Shore

Species	Numbers per Square Meter
Balanus crenatus	25
Pachygrapsus crassipes	25
Acanthina spirata	25
Pagurus samuelis	25
Tegula gallina	25
S=5

Community Dominants

1. Definition: Species which dominate the community
2. Numerical dominant (ex. Chthamalus fissus numerically dominates the Gulf of California Rocky Shore in the Hypothetical Data of Fig. 1 above)
3. Biomass dominant
4. Importance to the existance of other species by altering the habitat in some way

Keystone Species

1. Definition: Species which control the community and if removed would cause fundamental changes in community structure

Ecological Succession

1. Definition: A predictable replacement of one community by another; starting with a short-lived pioneer community and ending with the establishment of a stable, long-lasting climax community.
2. Pioneer Community --> Seral Stages --> Climax Community

Pioneer Community

1. Definition: The first stage in a succession
2. Dominated by short-lived "weedy" species
3. Facilitates the establishment of the next stage

Seral Communities

1. Definition: In between stages in a succession
2. Facilitates the establishment of the next stage leading to a climax community

Climax Community

1. Definition: The last stage in a succession
2. Dominated by long lived, "competitive" species
3. Inhibits the establishment of another community

Primary Succession

1. Definition: A succession that starts from a completely abiotic condition
2. Ex. After a volcanic eruption or the introduction of a new structure into the ocean

Secondary Successsion

1. Definition: A succession that starts from a biotic condition that has been altered and no longer supports a climax community
2. Ex. After the removal of kelp by a storm

Ecosystem Structure

1. Ecosystems are somewhat self-contained and self-sustaining.
2. Requires an input of energy and materials to sustain life
3. Capable of recycling elements reducing demand for them
4. Ecosystems are organized to facilitate the passage of energy and materials which are used by organisms for maintanence and growth

Trophic Structure

1. Definition: The freeding relationships found in an ecosystem.
2. Feeding relationships influence the passage of energy and materials within ecosytems

Producers

1. Photoautotrophs
2. Energy and materials both enter the biotic portion of ecosystems by the action of producers

Consumers

1. Heterotrophs
2. Energy and materials are both transferred between species in ecosystems by the action of consumers

Levels of Consumption

1. 1^{st degree} consumers eat producers
2. All herbivores are 1^{st degree} consumers
3. 2^{nd degree} and higher level consumers eat other consumers
4. All carnivores are 2^{nd degree} and higher level consumers

Levels of Carnivory

1. 1^{st degree} carnivores are 2^{nd degree} consumers and eat 1^{st degree} consumers (eat herbivores)
2. 2^{nd degree} carnivores are 3^{rd degree} consumers and eat 2^{nd degree} consumers (eat 1^{st degree} carnivores)
3. 3^{rd degree} carnivores are 4^{th degree} consumers and eat 3^{rd degree} consumers (eat 2^{nd degree} carnivores)

Top Carnivores

1. Definition: Highest level carnivores
2. Highest level consumers

Omnivores

1. Definition: Eat many types of food
2. It is difficult to classify their level of consumption since they operate at more than one level

Scavengers

1. Definition: Eat dead organisms
2. They can operate at any one of the consumer levels depending on the level of the dead organisms they eat

Food Chain

1. Definition: A linear relationship of predators and prey where each prey species has one predator species and each predator species has one prey species

Food Chain Diagram

1. In a food chain diagram the arrows point from the prey to the predator
2. Example: phytoplankton--->zooplankton--->anchovy--->tuna

Food Web

1. Definition: A complex set of relationships between predators and prey where prey species have 2 or more predator species and predator species have 2 or more prey species.

Food Web Diagram

1. The arrows point from the prey to the predator
2. The producers are placed at the bottom with the herbivores just above them, and the carnivores at the top.

Energy and Ecosystems

1. Energy flows through an ecosystem
2. Open system with a continuous input and an equivalent continuous output

Energy Supply

1. Most ecosystems rely on the unlimited supply of sunlight capturing it by photosynthesis
2. Energy captured during photosynthesis is stored in the chemical bonds of the molecules synthesized during the process

Energy Utilization

1. Most of the captured energy is used by the autotrophs to maintain their lives and is lost as heat
2. About 10% is used for growth and reproduction being transformed into producer biomass

Biomass

1. Definition: Weight of living tissues
2. Wet weight or dry weight

Available Energy

1. The energy in producer biomass is transferred to herbivores and then to carnivores.
2. Energy transfers are by ingestion, digestion, absorption and assimilation.

Energy Losses

1. Energy is lost from an ecosystem in the form of heat and the chemical energy in wastes and dead organisms that are transported out of the ecosystem

Energy Transfer

1. Energy transfers between trophic levels are only 10% efficient with 90% lost as heat
2. Ten percent of the energy is found in the biomass of animals in the next trophic level

Energy Losses

1. Not all prey items are eaten some die and about 10% of their energy goes into decomposer biomass
2. Digestion and absorption is not complete
3. Cellular respiration transforms alot of the energy to make ATP which is used for many processes other than growth and reproduction
4. Examples: movement, transport, vital processes

Eltonian Pyramid

1. Graphical represention of the energy relationships of trophic levels in an ecosystem
2. Represent the decreasing standing crop at succeedingly higher trophic levels

Standing Crop

1. Definition: The amount (of individuals, biomass, or energy) present at any one moment in time

Pyramid Diagrams

1. Trophic levels are arranged with the producers at the base of the pyramid and the consumers in increasingly higher levels up the pyramid
2. The width of the pyramid at any trophic level indicates the size of the standing crop

Pyramid Types

1. Numbers: Represents the number of individuals of each trophic level
2. Biomass: Represents the weight of living tissue of each trophic level in kilograms
3. Energy: Represents the energy content of each trophic level in calories

Pyramid Relationships

1. The energy content and biomass of a single individual increases moving up the pyramid although the total energy and biomass of the trophic level decreases

Materials and Ecosystems

1. Materials such as carbon, nitrogen and phosphorus cycle in an ecosystem
2. Semi-closed system with limited input and output of elements and continuous recycling between the biotic and abiotic portions

Source of Materials

1. The Reservior is the source of materials from outside the ecosystem
2. It is often the water or atmosphere but is sometimes sediments or rock and can be another ecosystem

Recycling of Materials

1. Occurs between the organisms of the system and an abiotic Exchange Pool which is usually in the water or sediments inside the ecosystem

Decomposition

1. Decomposers such as fungi and decomposing bacteris breakdown organic material into inorganic material making it available to the mineralizing bacteria
2. Decomposers release materials from the biotic portion of the ecosystem to the exchange pool or reservior

Regeneration

1. Mineralizing bacteria regenerate inorganic materials by transforming inorganic materials in a way that makes them available to photoautotrophs
2. Allows materials to reenter the living portion of an ecosystem

Production

1. Definition: The process of making food from inorganic compounds
2. Carried out by photosynthetic autotrophs such as phytoplankton, seaweeds and plants
3. Determines how much food is available to consumers

Photosynthesis

1. Definition: A process utilizing light energy to synthesize food from inorganic compounds
2. Sunlight energy captured by chlorophyll is used to synthesize sugar from carbon dioxide gas and water
3. Carbon Dioxide + Water + light ---> Sugar + Oxygen

Gross Primary Production (GP)

1. Definition: Total amount of material produced including that which is used by the producer to meet its own energy requirements (photosynthesis)
2. Not all of this is available to herbivores

Net Primary Production (NP)

1. Definition: The amount of producer material produced that goes into new producer biomass (growth and reproduction)
2. This is the material available to herbivores

Respiration (R)

1. Definition: The amount of material used by the producer during cellular respiration to make ATP
2. ATP provides energy for the chemical and mechanical activities of phytoplankton

Primary Production Equation

1. NP=GP+R
2. NP=Net Primary Production (photosynthesis minus respiration)
3. GP=Gross Primary Production (Photosynthesis)
4. R=Respiration

Photosynthesis or Gross Production (GP)

1. Carbon Dioxide + Water + light ---> Sugar + Oxygen
2. Oxygen is a Product

Respiration (R)

1. A process of oxidizing food molecules to extract their energy content
2. Sugar + Oxygen ---> Carbon Dioxide + Water + Energy (ATP)
3. Oxygen is a Reactant

Measuring Gross Production (GP) by Phytoplankton

1. Gross Production can be measured by measuring changes in dissolved oxygen concentration under controlled conditions
2. Photosynthesis releases oxygen
3. Respiration uses up oxygen

Light Bottles

1. Phytoplankton in a clear bottle will photosynthesize and respire
2. Gain in dissolved oxygen concentration is a measure of Net Production (NP) or photosynthesis minus respiration

Dark Bottles

1. Phytoplankton in a black bottle will respire but cannot photosynthesize
2. Loss in dissolved oxygen concentration is a measure of Respiration (R)

Dark and Light Bottles

1. Gross Production (GP) or photosynthesis can be calculated from pairs of bottles

Benthic Zonation

1. Bottom zones
2. Based on water depth and relationship to continents
3. Intertidal Zone is the benthic area that is alternately exposed to the air and the sea
4. Subtidal Zone is the benthic area that is below the intertidal but on the continental shelf
5. The Deep-Ocean Floor is the benthic area beyond the continental shelf

Pelagic Zonation

1. Water column zones
2. Based on water depth and relationship to continents
3. Neritic Zone is the pelagic layer overlying the continental shelf
4. Oceanic Zone is the pelagic layer overlying the ocean basins

Pelagic Stratification

1. Division of the pelagic environment based on depth and other abiotic factors which vary with depth.
2. These factors include light, temperature, salinity, dissolved oxygen, pressure, and nitrogen and phosphorus concentrations
3. Epipelagic Zone is the pelagic layer that lies above 200 meters
4. Mesopelagic Zone is the pelagic layer that lies between 200 to 1,000 meters
5. Deep-Sea Zone is the pelagic layer that lies below 1,000 meters

Light and Pelagic Zonation

1. The Photic Zone is the well lighted waters down to 100 meters in clear water
2. The Disphotic Zone is the poorly lighted waters from 100-1,000 meters in clear water
3. The Aphotic Zone is the unlighted waters below 1,000 meters in clear water