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Class in LibraryMultimedia Room

Mon. Tues. Wed. Thurs. Fri.Week ofOct. 20

Wet, muddy outdoor lab – wear closed-toed shoes

Week ofOct. 27

Independent project set-up

Week ofNov. 3

Forest ecology lab – dress for weather

Exam 2T lab switch?

Week ofNov. 10

Independent project analysis

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Nutrient recycling in aquatic systems

- where is it happening?

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-sediments not in contact with pelagic zone

- most sediments are anaerobic - reactions are slower

Pelagic zone

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Figure 8.12

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Cool (dense) water

Warm (low density) water

Water below the thermocline may becomedepleted of oxygen in summertime

Why?

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Fig. 8.16

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Low oxygen in facilitates recycling ofsome nutrients (P and Fe)

When oxygen is present, P and Fe combine toform insoluble compounds which remain in the sediments

When oxygen is absent, P and Fe are solubleand remain in water – can be mixed upinto pelagic zone and taken up by algae

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Fig. 8.17

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Which nutrient is most limiting to aquaticsystems??

What do I mean by most limiting?

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P - limitation

N-limitation

LIS

Housatonic

Where does P-limitation switchto N-limitation?

How will changes in nutrient loading affect species composition and frequency of algal blooms?

Goal to decreaseN input to LIS by55% in 15 years

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Example of using properties of nutrientrecycling in aquatic systems to reducealgal blooms in freshwater systems

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Thermocline

Fountain

oxygen

How could this reduce algal blooms?

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Nutrient recycling

- Terrestrial systems- soil

- weathering of rock- decomposition of organic matter

- Aquatic systems- sediments and deep water

- reactions slow (anaerobic)- decomposition not near uptake

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Structure of course

Environmental variability

Organisms

Ecosystems

Populations

Species interactions

Communities

Applied Ecological Issues

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Outline

Introduction

How are populations defined and measured?

How do populations grow?

How does population size change through time and space?

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Population - group of organisms of the same

species that live in a particular area

Population ecology - focus is on changes in the

number of individuals over time

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Questions asked by population ecologists

What limits population growth?

What causes variability in population size?

How do population in different geographic areas interact?

How does the number of adults in a population change relative to the number of juveniles?

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How are populations defined?

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Figure 13.4

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Figure 13.3

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Subpopulation – subsets of the

population that are separated and

have limited exchange

How much movement is there between

subpopulations?

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Figure 13.9

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migrationimmigrationemigration

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Humans like to manage population size of other organisms

Examples????

In order to manage population size, have to be able to measure it and have to be able to understand what makes population change in size

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How are populations measured?

1. What do we measure?

2. How?

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What do we measure?

Total population size = number of individuals

How they are arranged in space

How many are in each age or size class

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Population structure – the density and

spacing of individuals within a habitat

and the proportions of individuals

within each age or size class

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Total population size = number of individuals

= density x area

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Mark – recapture methods

1. Catch some individuals and mark them

2. Put them back and let them mix

3. Recapture some individuals and count how many are marked

4. Ratio of marked to unmarked gives an estimate of population size

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N = total number of individuals

M = number of marked individuals

n = number of recaptured individuals

x = the number of recaptured individuals who were marked

N = nM/x

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Mark – recapture methods

Assumptions

1. Population size is the same on the days you marked and recaptured.

2. All individuals have equal probability of being captured.

3. Marked individuals were well mixed before recapture.

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What do we measure?

Total population size = number of indivduals

How they are arranged in space

How many are in each age or size class

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Figure 13.5

There is a simple statistical test to test for distribution

Mechanisms?

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What do we measure?

Total population size = number of indivduals

How they are arranged in space

How many are in each age or size class

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Outline

Introduction

How are populations defined and measured?

How do populations grow?

How does population size change through time and space?

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Growth = births – deaths + immigration – emigration

When calculating growth rate, usually just seeing change in numbers over time

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Populations grow by multiplication ratherthan by addition

Just like interest in the bank

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Figure 14.3

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Exponential growth

-new individuals are added (born) to population continuously

r = per capita growth rate = contribution of each individual in population

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dN/dt = rN

Rate at which individuals are added = growth

rate on a per individual basis x population size

= derivative of exponential equation

= slope of line

Exponential growth

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Figure 14.4

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Exponential vs. Geometric Growth

Exponential – continuous reproduction- growth is smooth curve

Geometric – discrete breeding seasons- calculate growth at discrete

intervals

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Geometric growth

Growth rate = = population size at one time point/ size

at previous time point

N (t+1) = N(t)

N(t) = N(0) t

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Geometric growth: N(t) = N(0) t

Exponential growth: N(t) = N(0) ert

= er

Ln = r

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Figure 14.5

Exponential

Per capita growth rate = constantRate of increase= dN/dt, increases with N

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Figure 14.6