Marine EcologySummer 2013

2nd Session

Course Information

Instructor: Dr. Lesley BaggettOffice: House 4Office Hours: Tuesdays 11:30 to 12:30, or by appointmentPhone: 861-8525 (House 4); 251-458-5679 (cell)Email: lbaggett@disl.org

Course Information

• Participation in lab and field experiments and field trips is required

• Grading will be on Plus/Minus System• Grading:– Exams (Mid-Term and Final) 70%– Lab Notebook 25%– Lab Participation 5%

So Why Study Marine Ecology?

• Currently, approximately 39% of the world’s population lives near coast

• Avg. Density = 80 ind./km2 (but in countries such as Bangladesh and Egypt more like 1000 ind./km2 )

So Why Study Marine Ecology?

• World’s oceans provide:– Food, medicines– Renewable energy (tidal and wind)– Non-renewable energy (oil and gas)– Transportation routes (goods and people)– Mined commodities (e.g. minerals and diamonds)– Repositories for waste products– Recreation

Threats to Marine Systems

• Overfishing• Sea level rise• Pollution (nutrient, toxins, thermal)• Erosion• Development• Invasive species

Modern Research Methods

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NASA

Hypothesis Testing• Hypothesis = a statement that can be tested• Ho = Null hypothesis. States that there is no

effect/relationship• Ha = Alternative hypothesis. States that there is an

effect/relationship• Examples:– Ho = There is no difference in the growth of organisms in

nutrient-poor and nutrient-rich environments.– Ha = Organisms growing in nutrient-rich environments will

experience greater growth than those in nutrient-poor environments.

Scientific Method

The Scientific Method for Ecologists

• Patterns in nature are all around us.• Processes are factors that contribute to the

observed patterns.• Based on natural history, intuition and prior

study, hypotheses are proposed and tested regarding the processes that produced the patterns until (ideally) only one hypothesis remains.

Types of Evidence

• Non-Experimental Research– Data dredging– Meta-analysis

• Experimental Research– Mensurative experiments– Manipulative experiments• Pulse experiments• Press experiments

Sampling a Population

• Biological population = the sum of all organisms of a single species that inhabit a particular area– Very rare to be able to sample the entire population (i.e.

100% of the individuals)– Instead, must sample a subset of the population to infer

how a variable affects a certain aspect of a population• Statistical population = the entire set of

measurements collected from a habitat, a community, a biological population, or a part of the biological population

Sampling a Population

• Physical sample – a portion, or subset, of material objects (ex. 1 liter of seawater, all vegetation located within a quadrat, a sample of 100 fish from the biological population)

• Statistical sample – the actually-measured portion of the statistical population. Is a portion of the larger dataset (the statistical population)– The data obtained from measurements of the physical

sample (e.g., the temperature or P content of the water, the biomass of the vegetation, the fork lengths of the fish)

Sampling a Population• Often focus on one species or a subset of species found

within an area• Know exactly what your device/methods are sampling

(e.g. organisms living on the substrate, within the substrate, in the water column, etc.)

• No single sampling device can adequately sample an entire habitat, community, or biological population

• A sample seldom contains all life stages of a organism• Must always clearly define the ecological entity of

interest and select an appropriate sampling technique

Selecting Samples

• Attempt to collect a representative sample of the defined population, community, or habitat

• Usually obtain random samples to ensure that legitimate conclusions can be drawn about the population (with a known chance of error)– Implies that each entity of interest has an equal

opportunity of being collected in a sample– Collections made in one sample do not influence

collections made in another sample

Selecting Samples

• Biased sampling occurs when some members of the population are more likely to be sampled than others, or if the recording of some measurements affects the recording of other measurements

• Can haphazardly select locations of sample collection (ex. Close your eyes and throw a quadrat into a seagrass bed)

• Can randomly select study sites or locations of sample collection within a site using random number generator or a random numbers table

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17

18 19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36 37

38 39 40 41 42 43 44 45 46

Randomly Generated Numbers: 12, 6, 28, 46, 1, 31, 34, 10, 43, 25

Random Sampling

Sample Replication• Can’t draw conclusions based on single sample• Repeated measurements can vary greatly from one

another, so a single value has a high probability of being far removed from the mean

• Must perform a series of replicated samples (replicates) from which the mean of the statistical population of interest can be estimated as well as the error involved

• Number of replicates/sample size: No really set number. – Often depends on logistics of sampling and funding– Can use power analyses and other procedures to determine if

you had enough replication

Variability in Sample ValuesSample values:

51

106

1549

Mean = 7.14Std. Dev. = 4.6

• Standard Deviation = an approximation of the average difference (deviation) of the values from the mean (low value = values are close to the mean; high value = values are spread over a large range)– The smaller the value, the better the sample

mean is as a population estimate– Unaffected by sample size

• Standard Error = a measure of the standard deviation of sample means from the true population mean (how close to the population mean your sample mean is likely to be)– Used to calculate confidence intervals for your

mean (see Appendix I in lab manual)– Should decrease with larger sample sizes, as your

estimate of the population mean improves

Controls

• Allow investigator to get an idea of the normal conditions without manipulation

• Must compare results of manipulative treatments to controls

Marine Biology and Ecology

• Functional biology = how an organism carries out basic functions, such as reproduction, and aspects of metabolism

• Ecology = the interaction of organisms with their environments and how these interactions determine the abundance and distribution of the organisms

• Biodiversity = the number of species in an area, and what controls that number

Marine Biology and Ecology

• Functional biology = how an organism carries out basic functions, such as reproduction, and aspects of metabolism

• Ecology = the interaction of organisms with their environments and how these interactions determine the abundance and distribution of the organisms

• Biodiversity = the number of species in an area, and what controls that number

Marine Biology and Ecology

• Functional biology = how an organism carries out basic functions, such as reproduction, and aspects of metabolism

• Ecology = the interaction of organisms with their environments and how these interactions determine the abundance and distribution of the organisms

• Biodiversity = the number of species in an area, and what controls that number

Major Marine Habitats

Life Habits of Marine Organisms

Terrestrial vs. Marine Environments – Physical and Chemical Differences

• Seawater is much more dense than air (as such, organisms can float in it readily

• Seawater strongly absorbs light

• Effects of gravity – sea creatures do not have to invest as much in skeletons/bodily support b/c they gain buoyancy from water

• O2 can be limiting in the marine environment

Terrestrial vs. Marine Environments – Biological Differences

Terrestrial MarineA. Dominated by large, long-lived plants A. Dominated by short-lived microscopic

plants (few exceptions, e.g., kelp and algae)

B. Dominant herbivores are relatively large (range from insects to elephants)

B. Dominant herbivores are mostly microscopic (e.g., copopods)

C. Plants are mostly indigestible C. Plant is consumed in its entirety

D. Fauna is short-lived compared to plants (community named for dominant plant)

D. Fauna is long-lived compared to plants (community named for dominant animal)

E. Large animals often herbivores E. Large animals often carnivores

F. Production generally higher, transfer of energy from 1st to 2nd trophic level is less efficient

G. Production lower, transfer of energy from 1st to 2nd trophic level is more efficient