Ecosystems

Chapter 54

Overview

Food Chains and Food Webs

Productivity

Ecological Pyramids

Biomagnification

Nutrient Cycles

Global Warming

Ecosystems -The Community along with:

Nutrient Cycling Energy Flow

Energy Transfer in Ecosystems Food / Energy Pyramid

Primary Consumers eat producers, incorporating the energy into the next level.

Only 10 % of energy consumed moves to next level

Animals loose 90% of the energy at each level Why are Big Fierce Animals so Rare??

Consumers are Heterotrophs

Limited by Thermodynamcis

Simple Food Chains

Trophic Levels

Both Marine and Terrestrial

Productivity

What is it?

Season effects

varies by ecosystem

Productivity –Amount of food in an ecosystem

Primary productivity is growth of producers (Biomass) the baseline for the entire ecosystem.

Gross productivity is the total amount of food produced or ingested at that trophic level.

Net productivity is amount available to next trophic level, after respiration

Measured by dry weight or calories

Productivity rates:

Kelp beds have highest productivity

Tropical rainforest highest per sq. meter on land, but only covers 3.3 % of globe

Open ocean, one of the lowest, but because it covers 65.0 % it equals rainforest

Marsh lands nearly equal tropical rainforest productivity

 Summary of satellite data on global primary productivity from 1997 to August

2000

NORTH AMERICA ATLANTIC OCEAN

AFRICA

SPAINWinter

Spring

Ocean Currents

Wind from the north starts surface ocean water moving

Earth's rotational force deflects moving water westward

c. Deep, cold watermoves up to replacewater moving west

Upwelling

Fig. 55-7

Atlantic Ocean

Moriches Bay

ShinnecockBayLong Island

Great South Bay

A

BC D

EF G

EXPERIMENT

Ammoniumenriched

Phosphateenriched

Unenrichedcontrol

RESULTS

A B C D E F G

30

24

18

12

6

0

Collection site

Ph

yto

pla

nkt

on

den

sity

(mill

ion

s o

f ce

lls p

er m

L)

Table 55-1

Food Webs

Energy transfer follows trophic levels

Many animals eat at several trophic levels

Omnivores: like most of us At salad bar you’re a herbivore Eating a burger makes you a carnivore

marsh hawk

crow

upland sandpiper

garter snake

frog

spiderweasel badger coyote

ground squirrelpocket gopherprairie vole

sparrow

earthworms, insects

First Trophic Level

Second Trophic Level

Higher Trophic Levels

Sampling of connections in a Tall grass prairie food web

grasses, composites

Energy Transfer in Ecosystems Food / Energy Pyramid

Only 10 % of energy consumed moves to next level

Why are Big Fierce Animals so Rare??

Consumers are Heterotrophs

Limited by Thermodynamics

Laws of Thermodynamics

Energy = ability to do work

1st Law = Total amount of energy is a constant

2nd Law = Some energy is lost in every transfer, not 100% efficient Most energy lost as heat Autotrophs about 1% efficient (light–sugar) Heterotrophs about 10% efficient

Energy Pyramid

Pyramid of Numbers

Nutrients Cycle

Elements change form, but are not lost No more carbon now than when the dinosaurs

lived !!

May be trapped in bio-inactive forms Ice, fossil fuels

Held together in chemical bonds Breaking bonds – releases energy Uses energy to form bonds

Cycles:

Nutrient cycles to learn:

Water

Carbon

Nitrogen

Carbon Cycle

Large reservoirs in rocks (99%), fossil fuels

Associated with Greenhouse Effect Build up of CO2 , CH4 etc. in atmosphere Raise sea levels – flooding islands, coasts More severe weather ??

Food chain moves through Carbon cycle

Nitrogen Cycle

Largest pool is in atmosphere (80%) a generally bio-inactive form

Nitrogen fixing bacteria capture it from air Many native plants have nitrogen fixing root nodules After water the most growth-limiting nutrient

Nitrogen important for Autotrophs to make protein

Protein breakdown releases it back to environment in urine

Nitrogen Cycle

Always need to replenish agriculture fields with fertilizer.

Denitrifying bacteria release it back to atmosphere

Tightly cycled in Ecosystems

Needed to make amino acids

Nitrogen Metabolism In amino acids, nucleotides

Nitrogen fixing bacteria (N2 ->NH3) In soil, and some plant root nodules

Nitrifying bacteria convert NH3 -> NO2 In soil, or biotower in treatment plant

Denitrifying bacteria N02 -(Nitrite) or N03 (Nitrate) to atmospheric N2

In soil, counter-act fertilizers

Forests and Nitrogen Cycle

Most of nitrogen tied up in a tree’s BiomassSoils tend to be nutrient poorOften highest in later stages of successionBurning trees releases nutrients Soil fertility only lasts a few seasons Nitrogen is leached out with rains Classic problem with Slash and Burn

Fig. 31.8

Hubbard Brook

Loss of Nitrate from a forest after clear cutting

1620

1850

1850 (pocket only)

1990

Extent of deforestation in the United States Remaining virgin forest

Bioaccumulation &Biomagnification

Bioaccumulation Build-up of substance within body

Lead in humans Calcium from milk to already strong bones

Biomagnification build up of of substance along food chain

DDT and birds Rachel Carlson’s Silent Spring

Build up of DDT alongFood Chain

Bioaccumulation

Biomagnification

Fig. 34.1

Peregrine falcon

DDT Residues (ppm wet weight of whole live organism)

Ring-billed gull fledgling (Larus delawarensis)Herring gull (Larus argentatus)Osprey (Pandion haliaetus)Green heron (Butorides virescens)Atlantic needlefish (Strongylira marina)Summer flounder (Paralychthys dentatus)Sheepshead minnow (Cyprinodon variegatus)Hard clam (Mercenaria mercenaria)Marsh grass shoots (Spartina patens)Flying insects (mostly flies)Mud snail (Nassarius obsoletus)Shrimps (composite of several samples)Green alga (Cladophora gracilis)Plankton (mostly zooplankton)Water

75.5 18.5 13.8 3.57 2.07 1.28 0.940.420.33 0.30 0.26 0.16 0.083 0.040 0.00005

Data for a Long Island, NY estuary in 1967

Greenhouse Effect

Gasses trap heat in atmosphere Carbon dioxide, methane, CFC’s

Anthropogenic use of these gasses is increasing

Earth’s temperature appears to be warming Hard to measure a world temperature

Sun’s rays penetrate atmosphere. Enters as light not as heat. Hitting the earth, light changes to heat.

Surface radiates heat. Greenhouse gases absorb some heat and radiate it back toward Earth.

Increased greenhouse gases trap more heat near Earth’s surface.

Greenhouse Effect

Correlation in changes in atmospheric CO2 with ice ages and interglacials

Fig. 55-21

CO2

CO

2 c

on

ce

ntr

ati

on

(p

pm

) Temperature

1960300

Av

era

ge

glo

ba

l te

mp

era

ture

(ºC

)

1965 1970 1975 1980Year

1985 1990 1995 2000 200513.6

13.7

13.8

13.9

14.0

14.1

14.2

14.3

14.4

14.5

14.6

14.7

14.8

14.9

310

320

330

340

350

360

370

380

390

Satellite image of an iceberg roughly the same size as Connecticut

Antarctica 2000

National Snow and Ice Data Center

Fig. 34.6

Fig. 55-24

O2

Sunlight

Cl2O2

Chlorine

Chlorine atom

O3

O2

ClO

ClO

Fig. 55-24

O2

Sunlight

Cl2O2

Chlorine

Chlorine atom

O3

O2

ClO

ClO

“Tragedy of the Commons”