Marine Ecology

• Species – a group of similar organisms whose members interbreed and produce viable offspring.

• Population – members of the same species that live together in the same area at the same time.

• Community – all the populations of different species that live and interact together within an area at the same time.

• Ecosystem – a community together with its physical (abiotic) environment.

How Populations Work in a Community

• Population growth– More individuals– Birth rates > death rates– Decrease in resources

• Food, nutrients, space• Until the available

resources can no longer support more growth

– Lag phase• Period of relatively slow

growth

– Post-lag phase…• Linear, Exponential, or

logistic growth

• Renewable resources: replenished by natural processes at a rate comparable or faster than its rate of consumption.

– solar radiation, oxygen, tides, food, water, and winds

• Non renewable:– used at a rate greater than the

environment's capacity to replenish them

• Linear growth– Constant numerical

increase; constant slope– Doubling occurs relatively

slowly

• Exponential growth– Growing numerical

increase; “J” curve– Doubling occurs rapidly– Occurs with no limits to

growth– e.g fig. 10.2b

(dinoflagellates…much like these bacteria)

Exponential growth until?

• Environmental resistance– Limiting factors

• Supply restricts the growth of a population (e.g. food)

• Logistic growth– Converts a “J” curve to an

“S” curve (fig. 10.4)– Sets carrying capacity

• Population size sustained by available resources

…as resources decrease, competition increases

Organisms interact within a community

• competition, predation, symbiosis

• Competition– organisms compete for

same resources• Intraspecific (within same

species)

• Interspecific (between species)

– Superior competitor wins• Outcompeting to the point

of eliminating the other = competitive exclusion

Sharing to avoid exclusion

• Resource partitioning– Specializing in part of

the resources• slightly different food• different spaces• different times

– Dividing the resources– Lends to smaller

populations of a single species

• Giving up some of the resources is limiting

Symbiosis (living together)

• Mutualism– Both organisms benefit

• “Cleaner” shrimp & fish (facultative)

• Zooxanthellae & Cnidaria (obligate)

• Commensalism– One organism benefits w/o

affecting the other• E.g. whale barnacles

(shelter & food)

• Parasitism– One organism benefits at

the expense of the other• E.g. intestinal worms(Nematodes in fin whale gut)• Ectoparasitic isopods

Marine communities• Lifestyles

– Benthic (bottoms)– Pelagic (open-water)

• Plankton: drifting in the currents

– Phytoplankton» autotrophic

– Zooplankton» Heterotrophic

– Nekton: free swimming

• Environment/structure– Transitional: land & sea– Depth– Topography Fig. 10.12

Flow of energy w/in ecosystem• How energy passes through the

ecosystem– one way flow (Fig. 10.13)

• Producers– autotrophs (self nourishment) that

use simple inorganic molecules to make complex organic molecules (photosynthesize)

• Consumers– heterotrophs (different

nourishment) that eat producers to gain energy, cannot gain energy just from simple inorganics

• Decomposers– heterotrophs that break down

dead material to make energy• At each level some heat is given

off or lost– energy that is unavailable to the

next level

Most food webs are complex… this

Antarctic example is considered simple:

Trophic levels

• Steps of energy transfer

• Each level relies on the level(s) below

Energy efficiency

• 10% E (ave) passes to next level– Only a small amount

goes toward actual growth

• Sustains fewer organisms

• 10 times more biomass is required to sustain the level above

Fig 10.16

Primary productivity

• Amount of carbon converted (fixed) from CO2 to usable organics– Gross primary production– Net primary production

• Leftover after respiration

gC/m2/day

gC/m2/year

• Can also measure O2 production via photosynthesis

• Productivity depends on:– Light– Location– Depth– Abundance of

organics– Etc…

Carbon cycle

• CO2 is highly soluble– 50 times >

atmosphere

• Converted by photosynthesis

• Broken down by respiration– Consumers,

decomposers, & producers

Homework (due 4/30/08)

• Review pgs. 231-240

• Describe the human impact of burning fossil fuels & increasing the amount of CO2 in the atmosphere

• What does this do to global temperatures?

• How does this impact our oceans?

• How does this impact the marine trophic levels?