1. An Invitation to Marine Science, 7th
Oceanography
An Invitation to Marine Science, 7th
Tom Garrison
Chapter 16
Marine Communities

2. Chapter 16 Study Plan Marine Organisms Live in Communities
Communities Consist of Interacting Producers, Consumers, and Decomposers
Marine Communities Change as Time Passes
Examples of Marine Communities
Organisms in Communities Can Live in Symbiosis

3. Chapter 16 Main Concepts
A community is comprised of the many populations of organisms that interact at a particular location. A population is a group of organisms of the same species occupying a specific area.
A habitat is an organism’s “address” within its community, its physical location. Each habitat has a degree of environmental uniformity. An organism’s niche is its “occupation” within that habitat, its relationship to food and enemies, an expression of what the organism is doing.
Physical and biological factors in the environment determine the location and composition of a community.
A stable, long-established community is known as a climax community. This self-perpetuating aggregation of species tends not to change unless disrupted by severe external forces.
More than half of the animal species known to science are not free-living. Most are actively involved in close symbiotic relationships with at least one other life-form in their community.

4. Communities Consist of Interacting Producers, Consumers, and Decomposers
What are some terms used to describe organisms and their environments?
Habitat - an organism’s physical location in its community
Niche - an organism’s role in the community
Biodiversity - the variety of species in a given area

5. Physical and Biological Environmental Factors Affect Communities
A proper balance of physical and biological factors is important for the success of each organism and the community.
Different organisms have different tolerances for specific factors.
Steno- is a prefix meaning “narrow”. It can be used to describe organisms that have narrow tolerances for specific factors
Eury- is a prefix meaning “wide”. It can be used to describe organisms that have wide tolerances for specific factors

6. Physical and Biological Environmental Factors Affect Communities
Range of tolerance to a physical factor – in this case, temperature – for a population of organisms.

7. Growth Rate and Carrying Capacity Are Limited by Environmental Resistance
The J-shaped curve of population growth of a species is converted to an S-shaped curve when the population encounters environmental resistance.
The physical or biological conditions responsible for the cessation of growth are called limiting factors.

8. Population Density and Distribution Depend on Community Conditions
(above) Random, clumped, and uniform population distribution patterns. The clumped pattern is most common in nature; uniform is the rarest.
A random distribution implies that the position of one organism in a bottom community in no way influences the position of other organisms in the same community.
Clumped distribution occurs when conditions for growth are optimal in small areas because of physical protection (in cracks in an intertidal rock), nutrient concentration (near a dead body lying on the bottom), initial dispersal (near the position of a parent), or social interaction.
Uniform distribution with equal space between individuals, such as the arrangement of trees we see in orchards, is the rarest natural pattern of all.

9. Marine Communities Change As Time Passes
Marine communities change through time. Changes can occur slowly due to climate cycles or seafloor spreading, or quickly due to factors such as volcanic eruption.
A climax community is a stable, long established community.
If a climax community is disrupted, it may be restored through the process of succession.

10. The Ocean Supports Many Distinctive Marine Communities
What are some examples of marine communities?
Rocky intertidal communities
Seaweed communities
Sand beach and cobble beach communities
Salt marsh and estuary communities
Coral reef communities
Open ocean communities
Deep sea floor communities
Hydrothermal vent and cold seep communities

11. Rocky Intertidal Communities Are Densely Populated despite Environmental Rigors
Although the rocky shore looks like a very difficult place for organisms to make a living, the rocky intertidal zone - the band between the highest high-tide and lowest low-tide marks on a rocky shore - is one of Earth’s most densely populated areas.
A Pacific coast tide pool and intertidal shore. (left) A diagrammatic view. (right) Key

12. Rocky Intertidal Communities Are Densely Populated despite Environmental Rigors
The relationship between amount of exposure and vertical zonation in a rocky intertidal community. (a) A graph showing intertidal height versus hours of exposure. The 0.0 point on the graph, the tidal datum, is the height of mean lower low water. (b) Vertical zonation, showing four distinct zones. The uppermost zone (I) is darkened by lichens and cyanobacteria; the middle zone (II) is dominated by a dark band of the red alga Endocladia; the low zone (III) contains mussels and gooseneck barnacles; and the bottom zone (IV) is home to sea stars (Pisaster) and anemones (Anthopleura). The bands in the photograph correspond approximately to the heights shown in the graph.

13. Coral Reefs Are the Most Densely Populated and Diverse Communities
The coral reef habitat.
(a) A diagrammatic view.
(b) Key

14. Hydrothermal Vents and Cold Seeps Support Diverse Communities
The path of water associated with a hydrothermal vent. Seawater enters the fractured seabed near an active spreading center and percolates downward, where it comes into contact with rocks heated by a nearby magma chamber. The warmed water expands and rises in a convection current. As it rises, the hot water dissolves minerals from the surrounding fresh basalt. When the water shoots from a weak spot in the seabed, some of these minerals condense to form a “chimney” up to 20 meters (66 feet) high and 1 meter (3.3 feet) in diameter. As the vented water cools, metal sulfides precipitate out and form a sedimentary layer down-current from the vent. Bacteria in the sediment, in the surrounding water, and within specialized organisms make use of the hydrogen sulfide (H2S) in the water to bind carbon into glucose by chemosynthesis. This chemosynthesis forms the base of the food chains of vent organisms.

15. Precipitation FeS, FeS2, CuFeS2
Bottom current
Precipitation
FeO(OH) MnO2
Chimney
Precipitation
CaSO4 FeS
Sedimentation
Seawater seepage
H2S in water
Basalt
Basalt
Precipitation
FeS, FeS2, CuFeS2
350ºC
(660ºF)
350ºC
(660ºF)
Stepped Art
Fig , p. 453

16. Organisms in Communities Can Exist in Symbiosis
Symbiosis is the close interaction of the lives of two species.
What are some types of symbiotic interactions?
Mutualism – both organisms benefit in these relationships. An example is sea anemones and anemone fish.
Commensalism – one organism benefits, the other is not helped or harmed.
Parasitism – one of the organism benefits, but the other is harmed.

17. Chapter 16 in Perspective
In this chapter you learned that organisms are distributed throughout the marine environment in specific communities: groups of interacting producers, consumers, and decomposers that share a common living space. The types and variety of organisms found in a particular community depend on the physical and biological characteristics of that living space.
Any community is a dynamic place, growing and shrinking and changing its composition as residents respond to environmental fluctuations. The growth and distribution of organisms within communities depend on the often subtle interplay of physical and biological factors. The relative numbers of species and individuals in a community depend in part on whether its environment is relatively easy and free of stressors, or relatively hard and full of potential limiting factors. A few prominent marine communities were compared and contrasted in this chapter, and some representative adaptations of their residents are discussed. The main principle: Why do organisms live where they do?
In the next chapter you will learn about the range of marine resources, from physical resources such as oil, natural gas, building materials, and chemicals; marine energy; and biological resources such as seafood, kelp, and pharmaceuticals to non-extractive resources like transportation and recreation. World economies are now dependent on oceanic resources, but we find that we cannot exploit those resources without damaging their source.