Marine Communities

Basics Community: Organisms in a specific group of interacting producers, consumers, and recyclers that share a common living space. Population: A group of organisms of the same species that occupy a specific area.

Organisms Within Communities Dependent on the availability of energy Habitat: an organisms “address” within a community. Its physical location. Niche: An organisms “occupation” or “job”. Its relationship to its food and predators. Example: Small fish in a coral reef share the same habitat, but each species has a different niche. Each population has a different “job” based on its shape, size, color, behavior, and feeding habits.

Influence of Physical and Biological Factors Physical Factors include: Temperature Pressure Salinity Biological Factors include: Crowding Predation Grazing Parasitism Lack of sunlight Generation of wastes Competition for oxygen

Limiting Factors A a factor that limits and organisms success in a community. Prevents organism from feeding, growing, reproducing, defending itself, or sensing danger. Stenothermal Species: Affected greatly by temperature Eurythermal Species: Not affected by temperature Stenohaline: Affected greatly by change in salinity Euryhaline: Not affected by changes in salinity What does Stenobaric mean? Eurybaric?

Competition Availability of resources such as a food and light determine the number and composition of populations within a community. In a stable population, two species cannot occupy the same niche for long. One will outcompete the other and force one to extinction or to leave. Sometimes this is very simple: Fore example, in a rocky intertidal community, one species of barnacle lives on the upper portion of rocks and the other lives on the lower portion of rocks.

Growth Rate and Carrying Capacity If there were no competitors for food or space, then growth rate is exponential or J-Shaped curve (i.e. humans, bacteria). But most species have limiting factors which leads to environmental resistance (the sum of all limiting factors). This creates an S-shaped curve where a species grows until it reaches its carrying capacity and then levels out. Carrying Capacity: Population size of a species that a community can support indefinitely under a stable set of environmental conditions.

Distribution of Organisms Population Density: The number of individuals per unit area or volume. Higher in places like coral reefs and forests than in tougher conditions like polar regions or deserts. Random Distribution: Position of one organism in no way influences positions of others in the same community. Very rare. Abyssal Plains. Clumped Distribution: Conditions for growth are optimal in small areas (like cracks in rocks) or if there is nutrient concentration. Most common type. Uniform Distribution: Rarest type. Equal space between each individual (like arrangement of trees in orchards).

Distribution Types RandomUniformClumped

Change in Marine Communities Occur slower in marine communities than on land. However, natural catastrophes and human influence can rapidly change communities. Climax Community: Stable, long established community. Succession: Orderly changes of a community’s species composition from temporary inhabitants to long-term inhabitants.

Examples of Marine Communities Rocky Intertidal Seaweed Sand Beach and Cobble Beach Salt Marshes and Estuaries Coral Reefs Open Ocean Deep-Sea Floor Deep Rock Hydrothermal Vent and Cold Seep