Ecotoxicology

Question 1

What is ecotoxicology?

Answer 1

Study of environmental contaminants’ effects on biological systems.

Question 2

What are the two ways to measure toxicity?

Answer 2

Lab studies and field studies

Question 3

Advantages of lab studies

Answer 3

Quantify toxic effect on biota

Question 4

Disadvantage of lab studies

Answer 4

Challenging to extrapolate to the real environment

Question 5

advantages of field studies

Answer 5

More realistic

Question 6

disadvantages of field studies

Answer 6

Interaction of multiple
environmental factors make it difficult to quantify
the impact of a particular contaminant
How to measure toxicity?

Question 7

What are the two responses for measuring toxicity

Answer 7

lethal and non lethal

Question 8

What is the lethal concentration or lethal dose?

Answer 8

Concentration required to kill 50% of organisms after specified time
LD or LC

Question 9

What is the lethal time?

Answer 9

Time taken for 50% of the test organisms to die at a specified concentration of toxin

Question 10

Effect concentration EC to Inhibition Concentration

Answer 10

The concentration at which x% of the population will exhibit an effect

Question 11

What can toxin effects be ?

Answer 11

Acute or chronic

Question 12

What is acute toxicity

Answer 12

Short term exposure at relatively high concentrations

Question 13

What is chronic toxicity ?

Answer 13

Long term exposure at relatively low concentrations

Question 14

What is NOEC

Answer 14

No observed effect
concentration: the largest of a small number of discrete tests concentrations for which the mean response is not statistically different from the control response

Question 15

What is LOEC ?

Answer 15

Lowest observed effect concentration: the smallest of a small number of discrete test concentrations for which the mean response is statistically different from the control response

Question 16

What is the case study ?

Answer 16

Arsenic toxicity on green microalgae

Question 17

What are the Arsenic species in seawater?

Answer 17

Arsenite As(III): As(OH)3
o Arsenate As(V): AsO(OH)3
o Monomethyl arsenic MMA:
CH3AsO(OH)2
o Dimethyl arsenic DMA: (CH3)2AsO(OH)

Question 18

What is the effect of PAH on unicellular algae: Tetraselmis chuii

Answer 18

Tested toxicity of three oil waste products to T.
chuii after 96h exposure at both 20oC and 25oC
* Response: growth inhibition

Question 19

What is the concept of synergism cocktails of toxicants ?

Answer 19

Synergism in cocktails of toxicants refers to the amplified effect when multiple toxins are combined, resulting in a greater impact than the sum of their individual effects.

Question 20

Describe the study involving ciliated protozoan Cristigera exposed to Hg, Pb, and Zn.

Answer 20

Toxicant concentrations:
HgCl: 0.005 ppm, causing a 12.1% growth decrease
PbNO3: 0.300 ppm, causing an 11.8% growth decrease
ZnSO4: 0.250 ppm, causing a 14.2% growth decrease
When all three toxicants were combined, the growth decrease may exhibit synergism, resulting in a more significant impact than the sum of their individual effects.

Question 21

What is the concept of antagonism in cocktails of toxicants?

Answer 21

Antagonism in cocktails of toxicants refers to the mitigated effect when multiple toxins are combined, resulting in a lesser impact than the sum of their individual effects.

Question 22

Describe the study involving ciliated protozoan Cristigera exposed to Hg and Pb

Answer 22

Toxicant concentrations:
HgCl: 0.0025 ppm, causing a 9.5% growth decrease
PbNO3: 0.15 ppm, causing an 8.5% growth decrease
When both toxicants were combined, the growth decrease may exhibit antagonism, resulting in a lesser impact than the sum of their individual effects.

Question 23

Does phosphate affect arsenic toxicity?

Answer 23

Phosphate is affecting arsenic toxicity according to this data.
Phosphate is decreasing the toxicity of arsenic based on the trends shown in the graph, where higher phosphate levels (higher Sw + P L^-1 values) correspond to lower biological responses or toxicity effects.

Question 24

Example duration of exposure: spiny lobster

Answer 24

Five experiments where
lobsters are exposed to a
pesticide (dimercon)
* LD50 was found to vary with
duration of the experiment.

Question 25

How to detect toxic effect: Biomarkers

Answer 25

Biologically produced compounds serving as biomarkers include:
Vitellogenin (VTG): indicates the presence of endocrine disruptive substances
Metallothionein formation: produced to counteract metal contaminations
Cortisol formation: an indicator of stress
Multi-function oxidases: produced in response to the presence of organic compounds such as pesticides or hydrocarbons
Biomarkers can be used as indicators of exposure to chemicals present in the environment or organism, serving as indicators of toxicity. Ideally, they are specific to contaminants and can provide early warning of potential pollution.