1 Class in Library Multimedia Room Mon. Tues. Wed. Thurs. Fri. Week of Oct. 20 Wet, muddy outdoor lab – wear closed-toed shoes Week of Oct. 27 Independent project set-up Week of Nov. 3 Forest ecology lab – dress for weather Exam 2 T lab switch? Week of Nov. 10 Independent project analysis

2 Nutrient recycling in aquatic systems - where is it happening?

3 -sediments not in contact with pelagic zone - most sediments are anaerobic - reactions are slower Pelagic zone

4 Figure 8.12

5 Cool (dense) water Warm (low density) water Water below the thermocline may become depleted of oxygen in summertime Why?

6 Fig. 8.16

7 Low oxygen in facilitates recycling of some nutrients (P and Fe) When oxygen is present, P and Fe combine to form insoluble compounds which remain in the sediments When oxygen is absent, P and Fe are soluble and remain in water – can be mixed up into pelagic zone and taken up by algae

8 Fig. 8.17

9 Which nutrient is most limiting to aquatic systems?? What do I mean by most limiting?

10 P - limitation N-limitation LIS Housatonic Where does P-limitation switch to N-limitation? How will changes in nutrient loading affect species composition and frequency of algal blooms? Goal to decrease N input to LIS by 55% in 15 years

11 Example of using properties of nutrient recycling in aquatic systems to reduce algal blooms in freshwater systems

12

13 Thermocline  Fountain  oxygen How could this reduce algal blooms?

14 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

15 Structure of course Environmental variability Organisms Ecosystems Populations Species interactions Communities Applied Ecological Issues

16 Outline Introduction How are populations defined and measured? How do populations grow? How does population size change through time and space?

17 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

18 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?

19 How are populations defined?

20 Figure 13.4

21 Figure 13.3

22 Subpopulation – subsets of the population that are separated and have limited exchange How much movement is there between subpopulations?

23 Figure 13.9

24 migration immigration emigration

25 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

26 How are populations measured? 1.What do we measure? 2.How?

27 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

28 Population structure – the density and spacing of individuals within a habitat and the proportions of individuals within each age or size class

29 Total population size = number of individuals = density x area

30 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

31 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

32 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.

33 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

34 Figure 13.5 There is a simple statistical test to test for distribution Mechanisms?

35 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

36 Outline Introduction How are populations defined and measured? How do populations grow? How does population size change through time and space?

37 Growth = births – deaths + immigration – emigration When calculating growth rate, usually just seeing change in numbers over time

38 Populations grow by multiplication rather than by addition Just like interest in the bank

39 Figure 14.3

40 Exponential growth -new individuals are added (born) to population continuously r = per capita growth rate = contribution of each individual in population

41 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

42 Figure 14.4

43 Exponential vs. Geometric Growth Exponential – continuous reproduction - growth is smooth curve Geometric – discrete breeding seasons - calculate growth at discrete intervals

44 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

45 Geometric growth: N(t) = N(0) t Exponential growth: N(t) = N(0) e rt = e r Ln = r

46 Figure 14.5 Exponential Per capita growth rate = constant Rate of increase= dN/dt, increases with N

47 Figure 14.6