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Ecotoxicology > Lecture 2 - RH > Flashcards

Lecture 2 - RH Flashcards

1
Q

Fundamental to ecotoxicology is the relationship between dose and _______

A

Response

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2
Q

What is the dose regarding ecotoxicology?

A

The amount of toxicant to which an organism is exposed

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3
Q

What is the response regarding ecotoxicology?

A

The observed effect or endpoint that is measured

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4
Q

How is the dose-response curve generated?

A

A series of concentrations are tested ranging from no deaths to 100% deaths and as a result the LC50/LD50 is calculated

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5
Q

What is NOEC?

A

No Observed Effect Concentration

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6
Q

What is LOEC?

A

Lowest Observed Effect Concentration

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7
Q

What are the types of toxicants?

A

Essential

Non-essential

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8
Q

What is the difference between essential and non-essential toxicants?

A

Essential toxicants are toxicants that are essential for survival in trace amonts but toxic in large amounts.

Non-essential substances are not required for growth and survival and as concentration increases adverse events occur.

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9
Q

What are the types of responses to toxicants?

A

Death (lethality tests)

Growth inhibition

changes in metabolism

Cellular stress (induction/inhibition)

Changes in respiration

Developmental toxicity

Reproductive effects (embryo production and viability, and germination in plants)

Immunotoxicity

Genotoxicity (carcinogenicity, mutagenicity)

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10
Q

What are the problems with current endpoints looked for in ecotoxicology?

A

The endpoints may not be statistically significant. To be accurate we need appropriate:

Sample size and replication

Number of endpoints observed

Number of dosages or concentrations

Ability to measure endpoints

little variability of endpoints

statistical methodology

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11
Q

What is the effect of dose of toxicant on response? How does time affect this?

A

Very low = no effects

Very high = deaths

Time does nothing to doses that are very low and kills most individuals at higher doses

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12
Q

What are the types of toxicity tests?

A

Acute toxicity tests

Chronic toxicity tests

Lifecycle/Partial Lifecycle toxicity tests

Sublethal toxicity tests

microcosm and mesocosm tests

Field studies

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13
Q

What is acute toxicity testing?

A

The tested concentration/dose is severe enough to cause a rapid response (within 24 hours to 4 days)

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14
Q

What is chronic toxicity testing?

A

Tested concentration/dose causes a response after a longer period of exposure (usually greater than 1/10th of the lifespan of an organism. eg. 21 days for some fish species

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15
Q

What is lifecycle/partial toxicity testing?

A

Entire lifecycle (embryo-adult) or critical life stages are studied

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16
Q

What is sublethal toxicity testing?

A

Tested concentrations below level which directly causes death

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17
Q

What are microcosm and mesocosm tests?

A

Tests that simulate the conditions of the field

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18
Q

What does the toxic effect depend on?

A

Dose/concentration

Length of exposure

Lifestage

Previous exposure and toxicological interactions

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19
Q

What is used as a positive control in typical toxicology testing?

A

A reference toxicant

20
Q

What are the typical endpoints of acute toxicity tests on fish and invertebrates?

A

Mortality

Immobilisation

Loss of equilibrium

21
Q

What are the typical endpoints of acute toxicity tests in algae and vascular plants?

A

Growth inhibition

Mortality

22
Q

What is the difference between LC50, LD50, and LT50?

A

Lethal Concentration

Lethal Dose

Lethal time of exposure

*Respectively

23
Q

What does a higher LC50 value indicate?

A

Higher tolerance of an organism to tested toxicant

24
Q

What are the typical endpoints of chronic toxicity testing?

A

Reproduction (gamete production, egg viability, hatching success, germination)

Growth and Mortality

25
Q

What is the EC50 of an organism?

A

Effective concentration causing adverse effects in 50% of tested organisms for endpoints other than mortality.

26
Q

Why are some toxicant tests conducted on early life stages?

A

Early life stages are very sensitive and the effects can carry over to later stages

New evidence suggests effects of toxicants on the epigenome

27
Q

Are sublethal toxicity tests conducted in the short term or in the long term?

A

May be either

28
Q

What are the end points of sublethal toxicity tests?

A

Biochemical/physiological - induction of enzymes and proteins, up/down regulation of genes, hematology, respiration

Histological - tissue necrsis, tumour formation, pathology

Behavioural - locomotion, swimming ability, avoidance, predator-prey interactions, courtship

29
Q

Why are most chemicals less toxic in field than in tests?

A

Reduced persistence and bioavailability

30
Q

What are the chemicals that become more toxic in the field called?

A

Photoenhanced toxicity

31
Q

What is the difference between microcosm and mesocosm?

A

Classified based on size

32
Q

What are the advantages of using simulated mesocosms?

A

Systems are tested in a functioning ecosystem in the correct proportions

Can be maintained for a set time

Conditions can be monitored before and after adding toxicant

Components of system can be isolated

Environmental condiitions which is better than simulating in lab

Interactions between species can be investigated

33
Q

What are the limitations of simulated mesocosms?

A

Difficult to establish a realistic community

Very expensive to construct and maintain

Replication systems change differently with time and diverge

Scaling factors must be carefully considered

Difficult to interpret results and characterize endpoints

34
Q

What are the benefits of conducting field studies?

A

Natural environment is complex, dynamic, and changeable (unlike controlled lab environment)

More realistic evaluation of concentration-response relationship: Interactive effects of physico-chemical facors with toxicants

Can measure indirect effects - predator/prey interactions, biotic and abiotic interactions

35
Q

How are sites selected for field studies?

A

Cost, accessibility

Presence of the desired test species

36
Q

What endpoints are measured in field studies?

A

Can these effects be detected in field studies? (i.e reproducability of lab experiments)

Laboratory validation using acute and chronic tests

37
Q

What are the types of test organisms in aquatic systems?

A

Microorganisms

Primary producers (phytoplankton, micro-algae, and aquatic plants)

Invertebrates (molluscs + crustaceans)

Fishes

Amphibians

Sediments

38
Q

What are the types of test organisms in terrestrial environments?

A

Microorganisms

Primary producers

Invertebrates

Reptiles

Birds

Mammals

39
Q

What are the criteria for selecting organisms for field studies?

A

Organisms with a range of sensitivities should be tested

Tested species should be widely available and abundant

Test species should be native/ representative of tested environment

Tested species should be recreationally, commercially, or ecologically important

Tested species should be adaptable to lab conditions

Bacnground information on physiology and ecology of tested species should be known

40
Q

What are the important elements of experimental design regarding ecotoxicology?

A

Replication

Randomisation

Realisticness

Follow the testing guidelines

41
Q

What are the test guidelines used for?

A

Test guidelines provided detailed instuctions on experimental design.

*The test guidelines include:
Principles of the test
Test validity
Description of methods
Choice of species, holding vessels
Preparation of test chemicals
Required observations
Data analysis and interpretation
42
Q

What kind of increase in concentration of toxicants do organisms respond to?

A

Organisms respond to a proportional increase in toxicant rather than an absolute increase

43
Q

What is the PROBIT value?

A

1 unit of standard deviation

44
Q

How is the response linearised?

A

X axis uses a log scale

Y axis uses a PROBIT scale

45
Q

what kind of data can’t be analysed by PROBIT analysis?

A

continuous data

46
Q

What are the methods of data analysis used in ecotoxicology?

A

Exploratory plot analysis:
Histograms, box plots, dot plots, scatterplots, homogeneity of variance, normality, independence, Data transformation (log, arcsine, square root, PROBIT)

Hypothesis testing: Analysis of variance (ANOVA), parametric/non-parametric data analysis, type 1/type 2 error

Correlation and regression analysis

Multivariate analysis

47
Q

Part 2 to be watched

A

Part 2 to be wached

Ecotoxicology (22 decks)

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