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

Flow of energy w/in ecosystem How energy passes through the ecosystem –one way flow (Fig ) 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 CO 2 to usable organics –Gross primary production –Net primary production Leftover after respiration gC/m 2 /day gC/m 2 /year Can also measure O 2 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 Describe the human impact of burning fossil fuels & increasing the amount of CO 2 in the atmosphere What does this do to global temperatures? How does this impact our oceans? How does this impact the marine trophic levels?