Ecosystem

Concept of Ecosystem

An ecosystem is an integrated unit consisting of

interactions between microorganisms, plants, animals

whose survival depends on the maintenance and

regulation of their biotic and abiotic structure and function.

Ecosystem – large variations in size, structure,

composition,etc.

All ecosystems have certain basic structural and functional

features which are common

Ecosystem

Structural Features

Biotic structures

(a) Producers – photoautotrophs : mainly green plants

- generate energy and food from water, carbondioxide in air and importantly

sunlight

- Chemoautotrophs : some microorganisms and deep sea organisms

- generate energy from inorganic reduction rxns

- Chemo/phototrophs : Some microorganisms which use solar energy as well as chemical energy

EcosystemStructural Features

Biotic structures

(b) Consumers (heterotrophs) – Organisms which get their organic food by feeding on other organisms

Herbivores (primary consumers)

Carnivores (secondary and tertiary consumers)

Omnivores (feed both on plants and animals)

Detritivores (saprotrophs)

Decomposers (microbial systems)

In all ecosystems, the biotic structure prevails but the dominance of any component depends on the ecosystems

Ex, forest ecosystems – producers

deep ocean ecosystems – detrivores and decomposers

Ecosystem

Structural Features

Abiotic structures

(a) Physical factors – sunlight, temperature, rainfall, wind,

latitude/longitude, soil, water,

(b) Chemical factors – major and minor essential nutrients like

carbon, nitrogen, phosphorous, potassium, hydrogen, oxygen,

sulphur

Ecosystem

Functional Features

(a) Food chain, food web and trophic structure

(b) Energy flow

(c) Biogeochemical cycles

(d) Primary and secondary production

(e) Ecosystem development and regulation

Ecosystem

Functional Features

(a) Food chain, food web and trophic structure

The flow of energy is mediated through a series of feeding

relationship in a definite sequence of pattern – Food chain

Collection of matrices of feed chains – Food web

The definite arrangement of producers and consumers in

ecosystem and their interaction of energy transfer along with

population size - Trophic structure

Ecosystem

Functional Features

(a) Food chain -a sequence of eating and being eaten

Ex. Desert ecosystem

Each organism in the ecosystem is assigned a feeding level or trophic level depending on its nutritional status

Level 1

Level 2

Level 3

Level 4

Ecosystem

(a) Food chain - all organisms, living or dead, are potential food

for some other organism

The detritus food chain also exist which constitutes detrivores

and decomposers

The surface food chain derives its energy basically from plant

energy while the detritus food chain primarily obtains energy

from plant biomass, secondarily from microbial biomass and

tertiarily from carnivores.

EcosystemFunctional Features

(a) Food webs – shows pattern of energy or nutrient flow through out the community

More realistic representation of nutrient flow than foodchain, but cannot represent the relative importance of each foodchain in the food web.

Surface food chaindetritous food chain

Ecosystem

(a) Food web – network of food chains where different types of

organisms are connected at different trophic levels, so that

there are a number of options of eating and being eaten at

each trophic level.

In a linear food chain, if one species becomes extinct or one

species suffers then the species in subsequent trophic levels

get affected

Ecosystem

Significance of food chains and food webs

• Energy flow and nutrient cycling takes place through them

• Help in maintaining ecological balance

• Biomagnification

Ecological pyramids

Ecological pyramids

Ecological pyramids are graphical representations of the number

of individuals in different nutritional levels. For example, the plant-

insect-bird-hawk food chain can be represented as an ecological

pyramid

Plants absorb energy from the sun, the insects eat the plants, the

birds eat the insects, and the hawks eat the birds. Hence, the

energy of the sun has been transferred from the sun to the tissues

of the hawk. Since the number of individuals in each level usually

decreases, the resulting diagram looks like a pyramid.

•Pyramid of numbers

•Pyramid of Biomass

•Pyramid of energy

• Pyramid of numbers

• Represents the number of individual organisms at each trophic level

• The pyramid may be upright or inverted based on the ecosystem

• Pond, grassland, forest – upright

• Parasitic ecosystem - inverted

producers

parasitesherbivores

Hyper-parasites

treesbirds

Lice and bugs

microbes

• Pyramid of Biomass

• A pyramid of biomass shows the total biomass, or total amount of living material, at each trophic level. Every trophic level loses most of its energy to the environment as heat, which becomes unavailable to the next trophic level. Therefore, biomass decreases with each trophic level.

However in some aquatic ecosystems, the pyramid may be inverted. For eg., phytoplankton grow and reproduce so rapidly that they can support a large population of zooplankton even though at any one time, the biomass of phytoplankton is smaller than that of the zooplankton

• Pyramid of Energy

• pyramid of energy shows the flow of energy from one trophic

level to the next. It has a large base (primary producers) and

progressively smaller areas for each subsequent trophic level,

much like a pyramid of biomass. Loss of energy (heat) and

biomass reduction from one trophic level to another vary widely,

and may approach 90%.

• Energy Flow in an Ecosystem• Flow of energy in an ecosystem takes place through the food chain

and it is this energy flow which keeps the ecosystem functional

• The important feature of this flow is that it is Unidirectional or one

way flow

Input energy

Unused energy

Energy storage

Output energy

Living Biomass

respiration

Assimilated energy

Universal energy flow model

GPP Output energy

Heat loss

Single channel energy flow model

sunlight

Inputenergy NPP

respiration respiration respiration

Unused energy Unused energy

Energy NAEnergy NA

producers herbivoresCarnivores

Model depicts the gradual decline in energy level due to loss of energy at each successive trophic level in a grazing food chain

Primary productivity is the rate at which radiant energy is converted

into organic substances by photosynthesis by primary producers.

• Plants must use organic molecules to fuel their own cellular

respiration, about 55%

• 55% of gross primary productivity is available to heterotrophs; this

is net primary productivity

Secondary productivity – the energy stored at consumer level for

use by the next trophic level is defined as secondary production.

The secondary production is the amount of organic matter stored

by the herbivores or carnivores (in excess of respiratory and un-

assimilated energy loss).

In nature the surface (grazing) food chain and detritus food chain

operate in the same ecosystem

The volume of primary production passed to detritus food chain varies

with ecosystem. Ex. In forest ecosystem – huge quantity of

biomass produced cannot be all consumed by herbivores and

most of it passes into detritus food chain; In marine ecosystem –

there is very little primary production passed to detritus food chain

Energy flow models involving both food chains – Double channel or

Y-shaped energy food chain

• Trophic cascade: effect of one trophic level flow up or down to

more than one adjacent trophic level. Ex: a predator (lion) not only

affects its prey population (impala) but, by its eating of the prey,

also the prey’s prey (grass)

• Top-Down effects: predators control lower trophic level

populations Ex: Despite the presence of herbivores, not all plant

life is consumed. Predators keep herbivore population to a level

that the herbivores cannot extinct the plants

• Bottom-up effects: resources of lower trophic levels control upper

trophic level populations Ex: low nutrient concentrations constrain

plant production, which will constrain herbivore production, which

will in turn constrain carnivore production

Energy flow in an ecosystem is a consequence of two

fundamental laws of thermodynamics

First law of thermodynamics - energy can neither be created

nor destroyed; it can only be changed from one form of energy to

another

Second law of thermodynamics - when energy is transformed

from one form to another, there is always some loss of energy

from the system, usually as low grade heat

BIOGEOCHEMICAL (nutrient) CYCLING

Biogeochemical (nutrient) cycling is movement of materials -

• from environment to organisms and back in the characteristic paths

• between living and non living components of the biosphere

• A nutrient cycle includes a multitude of pools with material flux between them

• Energy flow brings about the flux

• A nutrient cycle can be considered to include two compartments.

- A reservoir pool – large and non biological compartments. Biogeochemicals are not fully in circulation. A part of them remains out of use in the reservoir pool.

- Liable or cycling or exchange pool – active pool with rapid flux rates.

- Biogeochemicals are used again and again in this cycling pool.

There are two types of nutrient cycles (based on reservoir pool):

• Gaseous cycles : atmosphere or hydrosphere is the reservoir

- Characterized by greater buffering capacity and resistance

against change. Four most abundant elements in the living

systems - hydrogen, carbon, oxygen and nitrogen have

gaseous cycles.

- Are quick and take little time to complete. Perfect system since

elements remain in circulation more or less uniformly.

• Sedimentary cycles: Lithosphere is reservoir – cybernetically

less controlled – mobility of materials in the reservoir is

relatively less and cycles are slow.

- Less perfect because the elements get locked in reservoir and

go out of circulation for long periods.

- Elements such as P, S, K and Ca have sedimentary cycles.

- Human beings can influence the nutrient cycling (a mighty

geological agent) can make material movement faster and

material cycles imperfect.

- Human influence is maximum felt on the smallest pool of the

biogeochemical cycles.

CARBON CYCLE:

• Principle building block of all kinds of molecules which make up living organisms. Most significant element for existence and survival of life on earth.

• Carbon is present in air (as CO2), in water (as dissolved CO2, H2CO3, HCO3 and CO3), in rocks (as CO3), in fossil fuels (as petroleum and coal), in all life forms (as proteins, fats and carbohydrates)

• 83% of C is present as inorganic minerals in the rocks of earth and rate at which it is released is extremely slow.

• Most predominant movement of C in the carbon cycle is through the biotic processes of photosynthesis and respiration.

• Average concentration of CO2 in atmosphere is 320 ppm. The oceanic reservoir is 50 times larger. About 3 x 1010 metric tonnes of C is converted to 12x 1010 metric tonnes of sugar annually.

• Solar Energy

6 CO2 + 12 H2O C6H12O6 + 6O2

NITROGEN CYCLE

Nitrogen is the component of proteins, nucleic acids and ATP which are essential structural and functional components of living systems.

• Nitrogen cycle is a gaseous cycle – includes Nitrogen fixation, Nitrification, Nitrogen assimilation, ammonification and denitrification in cycling nitrogen in nature from Environment to organisms and from organisms back to environment.

Nitrogen Fixation : Elemental Nitrogen of atmosphere is converted into Nitrogenous compound - It takes place by two methods.

(1) Physico-Chemical Nitrogen Fixation:

– Nitrogen from the atmosphere is fixed in the form of oxides as a result of lightning and volcanic eruptions. 10% Nitrogen is fixed

in this way.

(2) Biological Nitrogen Fixation: - By free living bacteria like Azotobacter, Clostridium, Blue green algae like Nostoc,

Anabaena,Cylindrospermum.

By symbiotic bacteria like Rhizobium found in the root nodules of leguminous plants.

N2 + 3H2 2NH3

Nitrification : Conversion of ammonia into nitrates is called nitrification. Ammonia is first converted into nitrites by bacteria Nitrosomonas & Nitrite is further converted into nitrates by Nitrobacter.

Nitrosomonas

2NH3 + O2 2 HNO2 + 2H2O + Energy

Nitrobacter

HNO2 + ½O2 HNO3 + Energy

Nitrogen Assimilation: Reduction of nitrates into ammonia in the plant body.

- Incorporation of Ammonia into amino acids which in turn from proteins. Animals take proteins from the plants which supply amino acids necessary for the metabolism of animals.

Ammonification: Conversion of urea and uric acid excreted by animals and proteins from dead plants and animals into ammonia by ammonifying or putrefying bacteria like Clostridium, Proteus, Pseudomonas, Bacillus etc.

Denitrification : Reduction of Nitrate ions in the soil into nitrogen gas by denitrifying bacteria such as Pseudomonas, Thiobacillus denitrificans. This nitrogen gas is once again released into the atmosphere.

• Occurs in water logged soils where anaerobic conditions exists.

NO3 NO2 N2O N2

PHOSPHOROUS CYCLE

Phosphorous cycle is a sedimentary cycle with major reserves of phosphorous in the sediments

The reservoir of phosphorous lies in the rocks, fossils, etc.

NUTRIENT CYCLES IN TROPICAL & TEMPERATE REGIONS

Tropical Temperate

Vegetation AboveGround

Vegetation Above Ground

Carbon 7.5% -- 50% --

Nitrogen 58% 44% 9% 6%

• Temperate systems have greater proportion of nutrient in the soil or sediments while tropical systems have in the biomass.

• Nutrient cycles tends to be physical in temperate regions while it is biological in tropical regions.

• Tropical soils are nutrient poor and nutrients mostly cycle within the organic structure of the system. Rich species diversity and symbiotic associations between autotrophs and heterotrophs including the following prevents loss of nutrients from the biotic pool.

- Root mat root for recovering nutrients from the surface litter

- Mycorrhizae acting as nutrient traps

- Algae & lichens on plant fixing nitrogen and scavenging nitrogen from rain water.

- Disturbance to the system/biotic community destroys the mechanisms for cycling of nutrient within the biotic pool and results in their loss to abiotic pool.

- Nutrients are ultimately lost from the abiotic pool due to prevailing high temperature and rainfall.

- High temp. results in rapid mineralization of nutrients.

- High rain fall leads to leaching and runoff loss of nutrients

ATTRIBUTES RELATED TO NUTRIENT CYCLING IN ECOSYSTEM:

• Cycling index : Mineral cycles are open initially but become increasingly closed.

• Nutrient exchange rapid initially becomes slow at later stage.

• Turnover time and storage of essential elements increases during succession and reach a steady state.

• Nutrient retention & conservation poor initially but increases and becomes pronounced later.

ECOSYSTEM STABILITY

• Stability is the ability to resist change when perturbed –

two types

- Resistance Stability – ability to withstand external

disturbance without getting perturbed.

- Resilience Stability – ability of the perturbed ecosystem by

external disturbances to return to original state once the

disturbance is removed.

Benign environment supports development of systems with

resistance stability while variable environmental conditions

favour development of resilience stability.

Servo mechanisms and homeostatic mechanism of control:

• Servo Mechanism - control system is external to the system being controlled.

• Homeostatic mechanism - control system is internal to the system being controlled, two types - centralized and distributed/diffused control.

• Control mechanisms can be either feed back and feed forward types.

• Feed backs may be positive or negative.

• Ecosystems are known for redundancy – believed to have both servo and homeostatic mechanisms (diffused type) of control.

-ve feedback -ve feedback

Sys

tem

fun

ctio

n

Homeostatic plateau

(-) (+)(0)Stress conditions

+ ve feedback

Death or collapse

+ ve feedback

Death or collapse

DYNAMICS OF ECOSYSTEM & SUCCESSION

Dynamics deal with changes in community structure & ecosystem functioning :

• As the system ages with time due to internal factors

• As a consequences of external factors of perturbations

Ecosystem dynamics due to internal factors is known as succession.

• Succession is an orderly sequence of communities of plants and animals which occurs over a period of time at the same place.

• Successional changes are directional and predictable and lead the ecosystem through a series of seral communities towards a climax community.

• During succession the physical environment gets modified by the communities which becomes less suitable to the existing community. As such a better suited community replaces it.

• Thus changes take place continuously in the community structure, organization, the environment at a given place in a course of time. The rate of successional changes is rapid initially and gradually

slows down.

SUCCESSION : BASIC INFORMATION

• Self organization is ecosystems’ property

• Replacement of simple systems by complex systems with specialization

• Succession refers to changes within a single system with transient species and population

• Observed successional trends are due to interactions at the species level

• Early successional stages (colonization phase) can be stochastic while the later stages are more organizational and directional.

DRIVING FORCE FOR SUCCESSION

• Community modifying the physical environment – existing species change conditions of existence and prepare for invasion by new species.

• Interactions of competition and co-existence among component population – species resist invasions but competition, predation, disturbances etc. allow species replacement.

TYPES OF SUCCESSION:

1. Primary succession & secondary succession

2. Autotrophic & Heterotrophic succession

Autotrophic succession occurs in a medium rich in organic substances and starts with P<R situation

Heterotrophic succession begins in a medium rich in organic matter and starts with P>R situation.

Succession tends to balance GPP with respiration (P=R)

Autogenic and Allogenic succession:

• If successional changes are determined by internal co-actions, it is autogenic (self generated) succession.

• If outside forces effect or control the change, it is the allogenic succession.

ATTRIBUTES OF SUCCESSION:

• A multitude of attributes can be used to describe changes associated with the succession.

• Degree and rate of change and time required to reach steady state.

- May vary from attribute to attribute

- May be influenced by climate

ATTRIBUTES RELATED TO ENERGY FLOW THROUGH ECOSYSTEM (ENERGETICS)

• Attributes used are

- GPP(P)

- Respiration (R)

- NCP

- Standing Biomass (B)

- P/R , B/R

SUCCESSION AND DISTURBANCES

External (allogenic) factors such as imported materials and energy, geological forces, storms, human disturbances can alter arrest or reverse successional trends.

• Ecosystem can adapt to the recurrent disturbances (perturbations dependent ecosystems) and develop quick recovery capabilities.

• Succession results in increased organizational complexity and increased efficiency of energy flow and nutrient cycling functions.

• Stressful environment supports relatively lower level of organization – an adaptation against perturbations providing resilience

• Older stages of succession have greater resistance to mild short term stresses while younger stages are more resilient to catastrophic

stresses.

Understanding successional pattern and recovery potential of the ecosystem is needed to predict & manage recovery after disturbance.

• Biomass & organic detritus increases

• Gross production (P) of an ecosystem tends to increase in primary succession and reaches a steady state during secondary succession

• Net community production (NCP) increases and after reaching a peak values gradually drops and becomes 0.

• Respiration (R) tends to increase (but lags in time behind production) & ultimately equals the production rate.

• P/R ratio moves towards unity P>R or P<R = P=R

• B/P ratio increases & reaches a steady state.

PROCESSES OF SUCCESSION:

1. NUDATION – Development of a bare area without any life form.

2. INVASION – Successful establishment of one or more species on

a bare area through dispersal or migration followed by ecesis

(establishment)

As growth and reproduction start, these Pioneer species increase

in number and form groups or aggregations

3. COMPETITION AND COACTION – As number of individuals

grows there is competition, both inter-specific and intra-specific,

for space, water and nutrition

They influence each other in an number of ways known as

Coaction

PROCESSES OF SUCCESSION:

4. REACTION – The living organisms grow, use water and nutrients

from substratum, and in turn influence the environment which is

modified through Reaction

The modification result in environment becoming unsuitable for

existing species and favour newer species (Seral Communities),

which replace them.

5. STABILIZATION – The succession ultimately culminates in a

more or less stable community called Climax which is in

equilibrium with the environment

The climax community is characterized by maximum biomass and

symbiotic linkages between organisms, maintained quite

efficiently per unit of available energy

ATTRIBUTES RELATED TO SPECIES & COMMUNITY STRUCTURE

• Each species has its maxima at some point in the time gradient and rarely a species thrives throughout the succession.

• Existing species of the system changes the physical and/or chemical environment and facilitates invasion of new species.

• Positive and negative interactions among the existing species make replacement of existing species with new species easier.

• Species composition changes rapidly at first than more gradually.

• Diversity – richness component increases

• Diversity – evenness component increases

• Life cycle increases in length & complexity

• During succession average size of organisms of a system increases

• Small size has the advantage of high metabolic rates, in nutrient - rich early successional stages.

• Larger size and complicated life history is considered as an adaptation for exploiting seasonal and periodic release of nutrients and other resources.

• Mutualistic symbiosis increases

Aquatic Ecosystems

• Freshwater

– Ponds & Lakes

– Streams & Rivers

– Wetlands

• Marine

– Oceans

– Coral Reefs

– Estuaries

Freshwater• Ponds & Lakes• Streams & Rivers• Wetlands

Freshwater

• Freshwater is defined as having a low salt concentration—

usually less than 1%

• Plants and animals in freshwater regions are adjusted to the low

salt content and would not be able to survive in areas of high salt

concentration (i.e, ocean)

• Fresh water ecology : It studies mainly the relationship between

organisms and the freshwater environment.

• Limnology:Study of all aspects(physical, chemical, geological and

biological) of freshwater

• They are of two types:

• Standing –water or lentic such as

• Pond, lake , swamps etc.

• Running water or lotic: river,stream, spring etc.

• Importance:

• Convenient and cheapest source of water for domestic and industrial

needs

• Participate in the hydrological cycle

• Cheapest waste disposal system

Ponds and Lakes

range in size from just a few square meters to thousands of square kilometersponds may be seasonal, lasting just a couple of months (such as sessile pools)lakes may exist for hundreds of years or more may have limited species diversity since they are often isolated from one another and from other water sources like rivers and oceans

Ecological classification of organisms

• On the basis of particular region or subhabitat where they grow.• 1 (a) Autotrophs (producers)• (b) Phagotrophs(macroconsumers)• (c) saprotrophs (decomposers or microconsumers)• 2 According to life forms• BENTHOS:

– Bottom dwellers– Ex. Microbes, worms, clams, some crustaceans

• PERIPHYTON:– Attach or cling to other structures– Ex. Aquatic plants, zebra mussels, Stentor

• PLANKTON:– Microorganisms that float (phyto- or zoo-)

• NEKTON:– Large swimming organisms (ex. Fish)

• NEUSTON:– Live at the surface– Ex. Water striders, snails, other aquatic insects & larvae

• Classification on the basis of region

• Littoral region:shallow water region with light penetration to the bottom typically occupied by rooted plants

• Limentic Zone: the open water zone to the depth of effective light penetration. This level will be at the depth at which light intensity is about 1% of the full light intensity.Community in this zone consists of plankton, nekton and neuston

• Profundal zone: the bottom and the deepest area which is beyond the depth of effective light penetration

http://www.lifesci.utexas.edu/faculty/sjasper/images/so54_15.gif

Littoral Zone

warmest since it is shallow and can absorb more of the Sun’s heat

sustains a fairly diverse community, which can include several

species of algae (like diatoms), rooted and floating aquatic plants,

grazing snails, clams, insects, crustaceans, fishes, and amphibians

the egg and larvae stages of some insects are found in this zone

vegetation and animals living in the littoral zone are food for other

creatures such as turtles, snakes, and ducks

Limnetic Zonenear-surface open water surrounded by the littoral zone well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplanktonplankton are small organisms that play a crucial role in the food chain – most life would not be possible without them variety of freshwater fish also occupy this zone

Profundal ZonePlankton have short life spans—when they die, they fall into the deep-water part of the lake/pondmuch colder and denser than the other twolittle light penetrates all the way through the limnetic zone into the profundal zoneanimals are decomposers

Ponds and Lakes

Temperaturevaries seasonally. Summer

from 4° C near the bottom to 22° C at the top

Winterfrom 4° C while the top is 0° C (ice)

between the two layers is a narrow zone called the thermocline where the temperature of the water changes rapidly with depth

Ponds and Lakes

during the spring and fall seasons is a mixing of the top and bottom layers resulting in a uniform water temperature of around 4° Cmixing also circulates oxygen throughout the lakemany lakes and ponds do not freeze during the winter resulting in the top layer being a little warmer

Ponds and Lakes

ice can develop on the top of lakes during winter

blocks out sunlight and can prevent photosynthesis

oxygen levels drop and some plants and animals may die

called "winterkill."

Epilimnion 22-25 degrees

Thermocline 10-20 degrees

Hypolimnion 4-5 degrees

Thermocline: Zone of rapid

temperature change

Thermal Stratification in Lakes

Streams & Rivers

• bodies of flowing water moving in one direction• found everywhere—they get their start at

headwaters, which may be springs, snowmelt or even lakes

• travel all the way to their mouths, usually another water channel or the ocean

Watershed

• describes an area of land that contains a common set of streams and rivers

• drains into a single larger body of water, such as a larger river, a lake or an ocean

Streams & Rivers

• characteristics change during the journey from the source to the mouth

• temperature is cooler at the source than it is at the mouth

• water is also clearer, has higher oxygen levels, and freshwater fish such as trout and heterotrophs can be found there

Streams & Rivers

• Towards the middle part of the stream/river, the width increases, as does species diversity—numerous aquatic green plants and algae can be found

Streams & Rivers• toward the mouth the water becomes murky from all

the sediments that it has picked up upstream• decreasing the amount of light that can penetrate

through the water• less light

– less diversity of flora– lower oxygen levels– fish that require less oxygen, such as catfish and carp, can be

found

Wetlands• Wetlands are areas of standing water that support aquatic plants

– Marshes, swamps, and bogs are all considered wetlands

• highest species diversity of all aquatic ecosystems

• many species of amphibians, reptiles, birds (such as ducks and waders), and furbearers can be found in the wetlands

• not considered under freshwater ecosystems as there are some, such as salt marshes, that have high salt concentrations—these support different species of animals, such as shrimp, shellfish, and various grasses

Wetlands River Otter

Damselfly Dragonfly Mayfly

Crayfish Snails Leech Bluegill Bass

Catfish Sculpin Minnow Snakes

Frog Turtle

Great Blue Heron Canadian Goose

Aquatic Ecosystems

• Marine–Oceans

–Coral Reefs

–Estuaries

Marine• cover about three-fourths of the Earth’s surface

and include oceans, coral reefs, and estuaries• algae supply much of the world’s oxygen

supply and take in a huge amount of atmospheric carbon dioxide

• evaporation of the seawater provides rainwater for the land

Oceans• largest of all the ecosystems• dominate the Earth’s surface• separate zones

– Intertidal– Pelagic– Abyssal– Benthic

• great diversity of species• richest diversity of species even though it contains fewer

species than there are on land

Oceans

Intertidal Zone

• where the ocean meets the land– sometimes submerged and at other times

exposed

– waves and tides come in and out

• communities are constantly changing

Intertidal Zone• rocky coasts

– stratified vertically• Where only highest tides reach• a few species of algae and mollusks

– submerged during high tide• more diverse array of algae and small animals, such as herbivorous

snails, crabs, sea stars, and small fishes

– bottom of the intertidal zone• only exposed during the lowest tides, many invertebrates, fishes, and

seaweed can be found

Intertidal Zone• sandier shores

– not as stratified – waves keep mud and sand constantly moving

• very few algae and plants can establish themselves—the fauna include worms, clams, predatory crustaceans, crabs, and shorebirds.

Wave Regions

• much stronger than wind

• decide what grows where

• shores classified by amount of wave action

– Exposed shores – receive full brunt of the ocean for most or at least some of the time

– Semi-exposed shores – sheltered by barrier islands but still have to cope with waves

– Sheltered shores – shelter of peninsulas and inshore islands

– Enclosed shores

• river mouths and estuaries

• completely sheltered by either a protective rocks or a sand bar

Pelagic – Open Ocean• waters further from the land, basically the open

ocean

• generally cold though it is hard to give a general temperature range since, just like ponds and lakes, there is thermal stratification with a constant mixing of warm and cold ocean currents

Epipelagic – Open Ocean• extends down to around 200m

– lowest depth that light can penetrate

• flora in the epipelagic zone include surface seaweeds

• fauna include many species of fish and some mammals, such as whales and dolphins

• many feed on the abundant plankton

Mesopelagic Zone

• "twilight zone" of the ocean – photic zone above– darkness below

• food becomes scarce – some animals – migrate up to the surface at night to feed– rely on food that falls down from above– eat each other

• sometimes the only things to eat may be bigger than the hunter

– developed long sharp teeth,– expandable jaws and stomachs

http://oceanlink.island.net/oinfo/deepsea/meso.html

Bathypelagic Zone

• extends down from 1000 to 4000m • only light is from bioluminescent organisms• only food is what trickles down from above, or from eating

other animals• water pressure at this depth is considerable (~100 – 400

atmospheres)• most animals are either black or red in color• very little blue/green light penetrates this deep – red is not

reflected and looks black

Narcomedusa

Vampire Squid

Snake Dragon

Angler Fish

Amphi - crustacean

Ctenophore – voracious predator

Deepstaria very slow swimmers, no tentacles, close flexible bells (up to a meter across) around their prey

Big Red grows to over a meter across

Abyssopelagic Zone - the Abyss

• 4000m to the sea floor• only zone deeper than this is the hadal zone

– areas found in deep sea trenches and canyons

• home to pretty inhospitable living conditions– near- freezing temperatures – crushing pressures