Chapter 10 Marine Ecology

Ecology Ecology: study of the interactions between organisms and their environment Habitat: specific location where an organism lives – distinct characteristics that determine what can live there –Temp, salinity, waves, tides, currents, sunlight

Organization of Communities Abiotic factors: non-living part of the environment –Sunlight, salinity, bottom type, etc Biotic: living organisms Population: group of one species in an area Community: all living things in an area Ecosystem: interaction of abiotic and biotic factors in an area

Population Growth Organisms always produce more offspring than it takes to replace themselves Environment keeps in check –If not, there is an explosion Carrying capacity: largest population size that can be sustained by available resources –Human capacity is estimated to be about 9 billion Limiting resource: a resource that restricts growth if it is in short supply Self-regulating: growth rate depends on own numbers –High pop= low growth

Species Interactions Competition Predator-prey Symbiosis –Parasitism –Commensalism –Mutualism

Competition Competition: organisms compete for a resource that is in short supply –Food, water, females, territory Interspecific competition: competition between species Competitive exclusion: one species eliminates another by outcompeting it Resource partitioning: animals that eat the same thing stay out of each other’s way by living in different places or feeding at different times –Become very specialized Ecological niche: special role in the ecosystem

Predator-Prey Predation: act of one organism eating another –Carnivore: eating another animal –Herbivore: eating plants or algae Natural selection favors the animals that can get away

Symbiosis Species live in close association with another Commensalism: one benefits, the other is unaffected –Barnacles on whales Parasitism: one benefits at the expense of the host –Tapeworms Mutualism: both partners benefit –Cleaning associations –Facultative symbiosis: can get by without the other –Obligate symbiosis: depend on each other

Larval Ecology Larvae are sensitive to changes in temp, salinity, and other factors Can have a critical period where they must obtain the right food to survive –Availability of plankton Larvae tend to stay near adults Abundance may depend on food supply or by competition, predation and other interactions

Marine Lifestyles Categorized by where and how organisms live Benthic organims (benthos): live on or buried in the bottom –Some are sessile Pelagic organisms: live up in the water column, away from the bottom –Plankton: “drifters”; at the mercy of the currents Phytoplankton: autotrophic algae Zooplankton: heterotrophic –Nekton: swim well enough to oppose currents Can be considered benthic; like rays

Zonation (Benthic) Depth and continental shelf Intertidal zone (littoral): shallowest part of the shelf –Exposed to air when tide is out Subtidal zone (sublittoral): live on shelf, below tidal zone –Never exposed to air Away from shelf= deep-sea floor –bathyal, abyssal, hadal (trenches)

Zonation (Pelagic) Neritic zone: lies over shelf Oceanic zone: waters beyond shelf break –Divided again into depth zones based on amount of light –Epipelagic: shallowest; lots of photosynthesis ft –Mesopelagic: no photosynthesis; to 3,300 ft –Bathypelagic: deep-sea –Abyssopelagic: deep-sea to bottom –Hadopelagic: deep-sea trenches

Energy Flow Autotrophs: get energy from sunlight Heterotrophs: get energy from food Energy is passed from one organism to another

Trophic Levels

Primary Productivity Productivity: amount of carbon fixed under a square meter of sea surface in a day or in a year –Phytoplankton and producers on the bottom Gross primary production: total amount of organic carbon manufactured by the primary producers Net primary production: organic matter left over after the producer used some for itself –Measured by carbon 14 left –Depends on environment Standing crop/stock: amount of phytoplankton already in the water

Nutrient Cycles Cycling of material between organisms and environment Carbon Nitrogen Phosphorus

Carbon Cycle Carbon dioxide dissolves easily in water Converted by producers into compounds through photosynthesis Respiration breaks up the compounds to be used by producers again Some is deposited as calcium carbonate which makes up biogenous sediment and reefs

Nitrogen Cycle Atmospheric nitrogen (N 2 ) is not able to be used by producers directly –Needs to be fixed/converted Can enter water through fertilizers or fossil fuel burning –More than natural processes (not good)

Phosphorous Cycle Enters ocean by rivers as phosphate –Weathering of rocks and bird guano –Fertilizers (really bad) Producers incorporate into organic matter Deposited in ocean sediments