Assigmnets
Lecture 1
1. What do you think is the biggest threat to the marine environment?
Global warming is causing sea levels to rise, threatening coastal population centers. Many
pesticides and nutrients used in agriculture end up in the coastal waters, resulting in oxygen
depletion that kills marine plants and shellfish. Factories and industrial plants discharge
sewage and other runoff into the oceans.
Pollution, overfisihin, ecosystem degradation
• Marine diversity is decreasing
– Nutrient loading, overfishing
• Habitats are being destroyed and disturbed
– Reclamation of land, infrastructure constructions
• Contamination
– Chemicals, plastic, metals
• Invasive species
– Outcompete natural species, infection of normal fauna
• Global change impacts
– Heating, change in acidity, change in water circulation
Lecture 3- eutrophication
1. Explain why marine life is more abundant in coastal waters as compared with the
open ocean listing all factors (biological, chemical, geologic, and physical) that affect
species diversity, biomass, and the distribution of life in the ocean. Article-lecture 3
Because land is nearby, there are large discharges of nutrient rich land runoff into
coastal waters. Further, periodic upwellings from the deep ocean can provide cool and
nutrient rich currents along the edge of the continental shelf. As a result, coastal
marine life is the most abundant in the world. Coastal areas receive more sunlight and
are usually warmer than open ocean or deep water habitats.
Here sunlight reaches the sea floor, so plants can grow. These provide food for
animals, protection from predators and a safe place for animals to breed and raise
young.
Satellites can measure the color of the surface ocean in order to track the
concentration of the green pigment chlorophyll that is used to harvest light in
photosynthesis . Higher chlorophyll concentrations and in general higher productivity
are observed on the equator, along the coasts (especially eastern margins), and in the
high latitude ocean. A major driver of these patterns is the upwelling and/or mixing of
high nutrient subsurface water into the euphotic zone, as is evident from surface
nutrient measurements.
https://www.nature.com/scitable/knowledge/library/the-biological-productivity-ofthe-ocean-70631104/
2. Explain the relationship among the compensation depth, the euphotic zone, and the
depth to which solar radiation penetrates the ocean and describe how these
relationships change in coastal waters as opposed to waters of the epipelagic open
ocean.
Euphotic zone
Euphotic zone. Is the uppermost or “well-lit” layer of the ocean in which there is sufficient
light energy available to support net photosynthetic growth. The euphotic zone extends to a
depth where light intensity falls from 0.1% to 1% of that at the surface and in the open sea
generally varies from <50 m to ∼200 m.
The upper surface of the ocean which is of 200 meters (656 feet) is called the euphotic, also
known as the "sunlight," zone.
The euphotic zone is the layer closer to the surface that receives enough light for
photosynthesis to occur. Beneath lies the disphotic zone, which is illuminated but so poorly
that rates of respiration exceed those of photosynthesis.
euphotic zone The upper, illuminated zone of aquatic ecosystems: it is above the
compensation level and therefore the zone of effective photosynthesis. In marine ecosystems
it is much thinner than the deeper aphotic zone, typically reaching 30 m in coastal waters but
extending to 100–200 m in open ocean waters.
Compensation depth
The compensation depth is depth at which the light intensity is just sufficient to balance
between the amount of oxygen produced and consumed by algae (typically a depth where
only 0.1-1% of solar radiation penetrates). The compensation depth varies with latitude,
water clarity, and nutrient availability.
Specifically, the CCD is deeper in the Atlantic (~5,000 m) than in the Pacific and Indian
(~3,500–4,500 m) due to a lower saturation state in the subsurface Pacific and Indian as a
result of higher total CO2 concentrations from organic matter remineralization
The calcite compensation depth (CCD) is the depth in the oceans where the rate of calcium
carbonate material forming and sinking is equal with the rate the material is dissolving.
Below the CCD no calcium carbonate is preserved—generally there is no CaCO3 beneath
about 15,000 feet
Carbonate compensation depth (CCD) is the depth in the oceans below which the rate of
supply of calcite (calcium carbonate) lags behind the rate of solvation, such that no calcite is
preserved. Shells of animals therefore dissolve and carbonate particles may not accumulate in
the sediments on the sea floor below this depth. Aragonite compensation depth (hence ACD)
describes the same behaviour in reference to aragonitic carbonates. Aragonite is more soluble
than calcite, so the aragonite compensation depth is generally shallower than the calcite
compensation depth.
Light penetration
Water is very effective at absorbing incoming light, so the amount of light penetrating the
ocean declines rapidly (is attenuated) with depth (Figure 6.5.2). At 1 m depth, only 45% of
the solar energy that falls on the ocean surface remains. At 10 m depth only 16% of the light
is still present, and only 1% of the original light is left at 100 m. No light penetrates beyond
1000 m.
3. Try to find data that show how the the export of nitrogen and phosphrous to the
coastal waters in EU have changed during the last 20 years
Data can be found at this homepage https://www.eea.europa.eu
Nitrogen is most likely to come from transportation, industry, agriculture and fertilizer
application, while increased phosphorus is more commonly the result of sewage waste,
amplified soil erosion and runoff from urban watersheds
Lecture 4- hypoxia anoxia
1. What controls organic C content in sediments?
Iron minerals and phosphates are vital factors affecting the amounts and occurrence of
total organic carbon (TOC) in sediments.
Overlying productivity, mineral surface area, sedimentation rate
2. When organic matter is mineralized in marine sediments, there is a natural sequence
of compounds used to oxidize organic matter. Describe the sequence of redox pairs
and draw a hypothetical vertical profile of sediment column with the appropriate
species found in pore waters?
3. What causes bottom turnover in marine sediments and what environmental effects
does a bottom turnover cause?
4. Under which conditions is low oxygen concentration expected to develop in the water
columns of a coastal marine environment?
Excess nutrients delivered to a waterbody can lead to both overgrowth of algae and
eutrophication. As dead algae decompose, oxygen is consumed in the process, resulting in
low levels of oxygen in the water. In some cases, large areas of water may become hypoxic
5. What controls the oxygen concentration in the water columns of marine environments
6. Why is most of the low oxygen environments located in the coastal zone?
Nutrient run-off from agriculture and from both treated and untreated sewage effluent are
major contributors to oxygen depletion in coastal waters, driving the over-enrichment of
waters with nutrients. Solutions to reduce nutrient runoff can be tailored to local needs and
economies.
The hot temperature near the equator reduces the dissolved oxygen from the ocean water and
as we move at higher latitudes, the temperature decreases, and thus the dissolved oxygen
increases in the ocean.
Lecture 5
Questions for oil pollution
1. Is there any difference between oils spill caused by tankers and the release of oil
from natural oil seeps with respect to impact on the marine environment?
Natural seeps release oil slowly over time, allowing ecosystems to adapt, whereas oil
spills from human activities like commercial oil transport can quickly release oil in
quantities that overwhelm an ecosystem. Nonetheless, all oil seeps impact the marine
environment.
Tankers-huge impact, oil on surface, coastal animals suffer
2. Why do birds have a very poor survival rate after being cleaned for oil?
They try to clean it from them so they eat it, you have to be very fast to make
sure they
have a high chance of survival
Oil can stick to birds' feathers, making them lose their water-proofing and
potentially leading to hypothermia.
3. Do you think that is a good idea to use resources for cleaning the birds that have
been in contact with the oil spill?
With the amount of time and effort, it might not be worth it
4. What is the fate of an oil spill in the marine environment?
Heavy oil will stay in the water column
Light will evaporate.
Spillage of crude oil might be better.
Eventually going to be broken down
Might end up in our food
Some of it will be dissolved
After being broken down it’s a good source of carbon
When oil is spilled at sea it normally spreads out and moves on the sea surface with wind
and current while undergoing a number of chemical and physical changes. These
processes are collectively termed weathering and determine the fate of the oil.
Some of these processes, like natural dispersion of the oil into the water, lead to the
removal of the oil from the sea surface, and facilitate its natural breakdown in the marine
environment. Others, particularly the formation of water-in-oil emulsions, cause the oil to
become more persistent, and remain at sea or on the shoreline for prolonged periods of
time.
The speed and relative importance of the processes depend on factors such as the quantity
spilled, the oil’s initial physical and chemical characteristics, weather and sea conditions
and whether the oil remains at sea or is washed ashore.
Ultimately, the marine environment usually eliminates spilled oil through the long-term
process of biodegradation.
5. The effect of an oil spill in the marine environment may last from a few years to
several decades, what is the possible reason for this large difference in the time
span recovery after an oil spill?
The time an ecosystem takes to recover from an oil spill depends on its size. The effects
of a small spill can take 15 years to completely disappear, while for a larger spill this may
take a lot longer.
Weather conditions-very windy might spread the oil more, high tidal amplitude, peat can
spread up biodegradation,
6. The addition of fertilizer can be a very effective method to mitigate oil spill in the
marine environment, why?
to enhance the growth of bacteria naturally present in the environment. These
bacteria naturally degrade certain of the toxic hydrocarbons in oil.
Albert D. Venosa and colleagues note that bacteria, evaporation, sunlight, and other items in
Mother’s Nature’s clean-up kit work together to break down the oil and make it disappear.
Scientists have known for years that adding nitrogen and phosphorus fertilizer to oilcontaminated soil can speed the growth of bacteria that decompose, or biodegrade, oil. But it
has been uncertain whether oil that has lingered in the environment for almost 20 years still is
biodegradable, leaving questions on whether further clean-up efforts might be worthwhile
Lecture 6
1. Why is plastic in the marine environment dangerous for marine life?
The most visible impacts of plastic debris are the ingestion, suffocation and entanglement of
hundreds of marine species. Marine wildlife such as seabirds, whales, fish and turtles mistake
plastic waste for prey; most then die of starvation as their stomachs become filled with
plastic.
lastic can affect marine species in a variety of ways, from entanglement and injury to
ingestion and toxic contamination
2. What size class of plastic presents the biggest treat to marine life
In most of the studies, microplastics have been detected in benthic environments and
sediments. Benthic environment is one of the significant feeding ecosystems for a
range of marine biota. Recent studies have shown that marine benthic biota ingest
microplastics which is present in the sea in the form of microbeads and microfibers.
Due to the size of microplastics, their bioaccumulation potential is very high. They
are ingested by an array of marine habitants like corals, planktons, fish, seabirds and
marine mammals and are transferred along the food chain.
3. What can be done to prevent plastic and solids for polluting the marine environement
Plastic Pollution Solutions: 7 Things You Can Do Today
Reduce Your Use of Single-Use Plastics. ...
Support Legislation to Curb Plastic Production and Waste. ...
Recycle Properly. ...
Participate In (or Organize) a Beach or River Cleanup. ...
Avoid Products Containing Microbeads. ...
Spread the Word.
4. Why is plastic pollution in the marine environment a much more serious problem than
other type of solids in the marine environment.
plastic pollution can kill marine mammals directly through entanglement in
objects such as fishing gear
Plastic sticks around in the environment for ages, threatening wildlife and spreading
toxins. Plastic also contributes to global warming. Almost all plastics are made from
chemicals that come from the production of planet-warming fuels (gas, oil and even
coal).
5. Currently there is a world wide initiative to remove plastic from the open oceans
using ships to clean the water column. Do you think that all plastic will be removed
from the marine environment? If not, which fraction (type) of plastic do you think that
it will be very difficult (impossible) to remove from the marine environment?
Filtration is the conventional way to remove microplastics from water, but this is
laborious and expensive
6. What are the primary effects of artificial reefs in the marine environments?
Artificial reefs provide shelter, food and other necessary elements for biodiversity and
a productive ocean
Or, if artificial reefs are not carefully planned or constructed, they can actually
damage natural habitats. In addition, monitoring observations indicate that many
artificial structures are quickly becoming habitat and possibly a spawning source for
invasive species such as the orange-cup coral
7. What effect may the material used for making artificial reefs have on the
environment?
The materials used in artificial reefs can cause harmful damage to the eco system especially
when tires are used. Some businesses use artificial reefs as a reason to just dump their stuff in
the ocean.
Some of the pros of artificial reefs are local economic benefits, increase of sea diversity, and
regenerating habitat. Some of the cons of artificial reefs are poaching, toxic material, and that
the ocean can become a landfill
Lecture 7 dredging
Questions for dredging
1. Explain why is the concentration of carbon, nitrogen and phosphorus not important
for the evaluation of the environmental impact of dredging operations in the marine
environment?
Likewise, while sediment nutrient concentrations may be decreased through
dredging and removal, runoff and erosion events over time tend to quickly
replenish nutrient concentrations in replaced sediments.
2. Some equipment used for dredging produce large spills during the dredging
operations. Which environmental concerns needs to be addressed before permission to
use this type of equipment can be given?
Increased pollution: Dredging churns up old industrial pollutants like PCBs
and heavy metals that have settled to the river bottom, adding to the river's
contamination levels
3. What part of the dredging operation, extraction of the sediment or dumping of the
sediment has the greatest environmental impact?
4. Why is confined storage of the extracted sediment more feasible than storage in
landfills?
The main, basic objective for a CDF is to retain dredge material solids and allow the discharge of
clean process water from the confined area.
5. As shown in the flow diagram for dredging operations follow-up measurements are
required at the dump site in a time period after the dumping have finished. What
measurements would you suggest that should be made in order to evaluate the
environmental impact of the sediment dumping?
One of the main concerns over dumping and dredging is the
release of contaminants to the water column (such as heavy
metals and TBT), which is associated with temporary
increases in turbidity. This can lead to increased
availability of contaminants to the food chain. Contaminants
in dredged material are monitored and assessed against
action levels to help reduce pollution at dumpsites
Potential environmental impacts resulting from dredged material disposal may be
physical, chemical, or biological in nature
For how long time do you think that it is necessary to monitor at the dump site to
determine the effect on the environment?
30 years
The required post-closure care period is 30 years from site closure, but this can be
shortened or extended by the director of an approved state program. That can help
ensure protection of human health and the environmen
Lecture 8-marine microbial pollution
1. Opportunitis and frank pathogenes
Frank pathogen: Disease in both healthy and immunocompromised
Opportunistic pathogen: Disease only in immunocompromised
2.Indigenous microorganisms have been originally in place and are not artificially transferred
or injected. Various studies have reported isolation of different microorganisms, however in
some cases there is suspicion that the microbes may have an external source like injection of
seawater.
Non ind : not produced, growing, living, or occurring naturally in a particular region or
environment : not indigenous.
3. The higher the exposure does the bigger chances of infection
4. MP Marine pathogen dispersal can be 100 times faster than terrestrial dispersal
Potential explanations



More rapid ≈one dimensional transport in marine systems (along coastlines)
–terrestrial transport in air more two dimensional
Fewer dispersal barriers in marine systems + strong oceanic currents
Better ocean survival than in jet streams (air)
5.
Temperature Natural
Sunlight
Organic matter
7.
a. P=1-(1+98/1.61*10^6)*^-0.1705 or times 100?
8. In simple terms, when bacteria or another type of microbe is directly exposed to certain
types of UV light, the DNA (its fundamental building block) of the cell is damaged,
preventing it from replicating. If a cell cannot reproduce, then the cell cannot cause infection,
which is how UV light kills bacteria.
Lecture 9
a. Typically, both bacteria and viruses strongly associate with particulate matter present in
freshwater, estuarine and marine environments. This association tends to be stronger in finer
textured sediments and is strongly influenced by the type and quantity of clay minerals and
organic matter present. Binding to particle surfaces promotes the persistence of bacteria in the
environment by offering physical and chemical protection from biotic and abiotic stresses.
Fecal-derived bacteria in marine environments tend to bind to particle surfaces (sediment,
sand, plastics) where they form biofilms that enhance their survival. In estuarine
environments, for example, the concentration of fecal bacteria is generally one or more orders
of magnitude higher in surface sediments (per 100 g dry weight) than in the water column
(100 ml). The survival of fecal bacteria in the oceans is thus positively linked to
concentrations of pollutants and other suspended matter in the water column
b.
c. These contaminants can have detrimental effects on aquatic ecosystems, impacting the
health of organisms, altering habitats, and potentially posing risks to human health through
the consumption of contaminated seafood, or through direct contact with polluted sediments.
6.
Several physical and chemical factors also influence disinfectant procedures: temperature,
pH, relative humidity, and water hardness. For example, the activity of most disinfectants
increases as the temperature increases, but some exceptions exist.
Efficiency of disinfection is defined using the Ct value which is defined as the product of
disinfectant concentration (milligram per liter) and the contact time (min). Temperature and
pH both influence the Ct value
Lecture 10
Question 1. The octanol/water partition coefficient (Kow) affects the fate of organic
pollutants in marine waters. What is the correct answer regarding the relationship between
Kow and water solubility of a chemical?
1.
2.
3.
4.
Water solubility is independent of Kow
Water solubility decreases with increasing Kow
Water solubility is equal to Kow
Water solubility increases with increasing Kow
Question 2. Toxic compounds in marine waters often co-occur in mixtures with other
compounds. The combined effect of 2 toxicants present at the same time in marine waters is
said to by “additive” if:
A. The combined effect of the 2 toxicants is equal to the sum of each toxicant effect
B. The combined effect of the 2 toxicants is greater than the sum of each toxicant effect
C. The combined effect of the 2 toxicants is equal to the effect of one of the toxicants
D. The combined effect of the 2 toxicants is smaller than the sum of each toxicant effect
Question 3
Some marine pollutants are referred to as “persistent” pollutants.
A. What are the characteristics of “persistent” marine pollutants”?
Persistent organic xenobiotics≈ mainly man-made synthetic compounds that do not occur
naturally in the environment. • Pesistent organics: often low polarity, often not very soluble
in water.
POPs pose a particular hazard because of four characteristics: they are toxic; they are
persistent, resisting normal processes that break down contaminants; they accumulate in the
body fat of people, marine mammals, and other animals and are passed from mother to fetus;
and they can travel great distances on wind and water currents.
B. Provide example of typical “persistent” marine pollutants. Pfas, plastic, pfos
C. Describe major types of abiotic and biotic degradation mechanisms for organic
xenobiotics in coastal marine waters.
These xenobiotic compounds have been degraded by physical and chemical methods such as
coagulation, filtration, adsorption, chemical precipitation, electrolysis, and ozonation
Question 4
Describe physical, chemical and biological factors or properties that can:
a. Increase adverse biological effects of man-made organic pollutants (xenobiotics) in marine
waters
b. Reduce (attenuate) adverse biological effects of man-made organic pollutants (xenobiotics)
in marine waters
Your answer can include both biological mechanisms and physical-chemical processes that
increase/reduce the availability and impact of potentially harmful chemicals.
Question 5
Many persistent organic xenobiotics can be found in marine waters and the compounds are
often distributed among different phases (compartments).
1. What are the major phases (compartments) for persistent organic xenobiotics in
the marine environment?
2. What is trophic transfer of persistent organic xenobiotics in marine waters?
Question 6
Many man-made organic pollutants (xenobiotics) can accumulate in marine organisms.
1. What is the difference between bioconcentration and biomagnification?
2. Which factors will facilitate biomagnification of man-made organic pollutants
(xenobiotics) in marine organisms?
Biomagnification: Concentration/accumulation of xenobiotics in a food chain
Result of Bioconcentration + Bioaccumulation at different trophic levels
Question 7
Some marine pollutants can interfere with the endocrine system in marine organisms and are
therefore considered “endocrine disrupting compounds” (EDCs). The EDCs can among other
things affect hormone production and/or function.
1. Provide examples of natural and man-made compounds with endocrine disrupting
effects in marine organisms.
2. What are the potential long-term effects of endocrine disruptors to marine life?
Lecture 11
Question 1
How are metals NOT exchanged between the atmosphere and the ocean?
A. Gas exchange B. Wet deposition C. Cold deposition D. Dry deposition
Questions 2
1. What is the difference between essential and non-essential metals? some metals are
essential for the biochemistry of living organismsà“Essential metals”
-Zn in 150 different enzymes
-Fe in the respiratory pigment haemoglobin in vertebrates -Cu in the respiratory pigment
haemocyanin in invertebrates -Co in vitamin B12
+ many more
Essential metal ions function as protein cofactors in a wide variety of biological processes,
are non-toxic when present in trace amounts in an organism, but can be toxic if
concentrations exceed a threshold [1]. Non-essential metals have no biological function and
are toxic to the organism in even trace amounts
1. Describe potential effect of an essential and a non-essential metal at different water
concentrations.
Enriched in the upper ocean due to atmospheric deposition
Question 3
Some metals are essential and some are non-essential for biological activity. Which of the
following metals is NOT considered an essential metal for marine organisms?
OBS: More than one mark may be added.
1.
2.
3.
4.
5.
6.
Zinc (Zn) yes
Lead (Pb) no
Copper (Cu) yes
Iron (Fe) yes
Cadmium (Cd) no
Manganese yes
Among those metals that are currently considered to be essential for normal biological
functioning are four main group elements, sodium (Na), potassium (K), magnesium
(Mg), and calcium (Ca), and six d-block transition metal elements, manganese (Mn),
iron (Fe), cobalt (Co), copper (Cu), zinc (Zn) and molybdenum (Mo)
Question 4
Mercury (Hg) is an example of a marine pollutant that has historically been introduced into
coastal marine environments in elevated concentrations.
1. Describe the fate of mercury in coastal marine waters and explain why it can become
toxic to marine life.
Investigations showed Hg had been transformed to methyl mercury
(CH3Hg+)àaccumulated in marine food chainàbiomagnification of an organometal §
Seafood consumed by local fishermen were heavily contaminated with Hg and
CH3Hg+àpoisoning
2. Provide example of marine organisms that are sometimes enriched in mercury. tuna
3. How can mercury in coastal marine waters affect human health?
The toxic effects of mercury on human health have long been known. Exposure to all
forms of mercury, including metallic, organic and inorganic mercury, can cause health
disorders. Of particular concern is the toxicity of mercury for the developing
organism, as the neurodevelopmental effects of exposure to (methyl)mercury in utero
and in early life have been well documented (1). It is therefore crucial to create a
critical mass of experts developing and implementing effective measures aimed at
preventing the adverse effects of mercury
Question 5
The effects of pollutants on marine life is affected by a range of physical and chemical factors
in marine waters.
1. Provide examples of other stress factors in marine waters that can affect the adverse effects
of marine pollutants on marine biota.
Hg (mercury) increases with size and age of fish
rising temperatures, nutrient enrichment, ocean acidification, habitat destruction and its
accompanying loss of biodiversity, and extreme weather events and their potential impacts on
human health.
1. Which of the factors mentioned in question ”A” will likely be affected by future
climate change?
Rising water temperatures, acidification, and low oxygen levels can combine with
natural ocean cycles to create extreme marine events. Marine heat waves, dead zones,
and coral bleaching are just a few examples of these events, which are projected to
become more common and severe.
Question 6
What is “Scope for growth” in marine animals and how can it be used to measure adverse
effects of marine metals?
Scope for growth (SFG) is the surplus of energy available for growth beyond that required for
maintenance. It represents the amount of energy available to organisms for growth and
reproduction after excretion, and metabolic requirements have been met (Warren & Davis,
1967).
Scope for growth (SFG) is a method of assessing the whole-animal physiological response to
sublethal stress induced by pollutants. It has been applied widely in small- and large-scale
pollution monitoring programmes in various regions of the world, ranging from temperate to
tropical. SFG was primarily developed for use with suspension-feeding mussels (Mytilus
edulis or similar indigenous species) and in combination with the analysis of chemical
contaminants in mussel tissues. SFG is based on the measurement of physiological responses,
such as feeding and respiration rate, and is derived from the difference between energy
acquisition (rate of feeding and digestion) and energy expenditure (metabolic rate).
Question 7
How can metals accumulated in sediments become bioavailable and thereby cause adverse
effects in marine biota?
Heavy metals can accumulate in aquatic habitats to toxic levels because they are not
biodegradable, although some metals are essential to the ecosystem's function. Metals are
eventually integrated into the sediment at the bottom, where organisms (benthic organisms)
can gather them.
Bioaccumulation and further transfer of heavy metals into the food chain can lead to
biomagnification at upper trophic levels, resulting in an elevated concentration of a
contaminant in an organism than in its prey.
In finer sediments, organic carbon plays a vital role in the binding of the metals, and higher
organic carbon reduces metal solubility and toxicity [3, 4]. Especially humus in soil binds
metals more than any other organic matter.
The accumulation of heavy metals in the sediment directly affects benthic organisms and also
influences many other organisms through the food web [19, 20], and endangers the wellbeing
of the aquatic ecosystem.
Exam questions
A range of metals can be found in marine waters and sediments. (weight 15%)
a. Why do coastal marine sediments often act as sinks for metals?
Sediments are generally considered to behave as a sink for pollutants such as heavy metals
in the aquatic environment, frequently acting as a source for their presence in waters, with
implications for catchment management.
b. How does the microbial transformation of mercury (Hg) to methyl mercury (CH3Hg+)
affect bioavailability and toxicity of Hg to larger organisms?
The toxic effects of mercury depend on its chemical form and the route of exposure.
Methylmercury [CH3Hg] is the most toxic form. It affects the immune system, alters genetic
and enzyme systems, and damages the nervous system, including coordination and the
senses of touch, taste, and sight.
Mercury is the only metal showing biomagnification across trophic webs. This is mainly due to the high
bioavailability of the methylmercury, which readily pass across biological membranes, and the difficult
excretion of this Hg species that binds to the proteins.
c. Why are benthic marine organisms often more exposed to metals than pelagic marine
organisms?
Benthic organisms interact with, and are exposed to, contaminants present in both dissolved
and particulate forms, with contaminant uptake occurring from porewater and overlying
water, the direct ingestion of prey, and direct or inadvertent ingestion of sediments
Because of sedimentation?
However, the presence of sediment layers at the benthic zone provides many nutrients and
adds greatly to species richness.
A range of marine pollutants has a potential for biomagnification. The figure below
illustrates some key processes in biomagnification. (weight 15%)
a. Describe the principle of biomagnification and the mechanisms that can explain changes
in tissue concentrations.
Biomagnification is due to enrichment in pollutant concen- tration in the consumer compared to its food
at each step of the food chain. As a result, when we measure the concentration of the pollutant in the
different or- ganisms of the food web, we find a direct relationship between tissular concen- tration and
the trophic level occupied by the organism
Biomagnification (also termed as bio amplification) in toxicology terms defined as the
increase in concentration of the substance that is toxic to the individual like pesticide
at the successive trophic levels in a food chain.
Biomagnification is a process causing the concentration of a substance (crosses) to
increase at higher levels of the food chain.
accumulate in the tissues of organisms higher up in the food chain
b. Which biological factors and properties of a chemical will increase the likelihood of
biomagnification of a pollutant in marine food webs?
This increase can occur as a result of: Persistence – where the substance cannot be
broken down by environmental processes. Food chain energetics – where the
substance's concentration increases progressively as it moves up a food chain.
c. Some microorganisms can bioaccumulate in marine biota. Provide examples of marine
organisms that can bioaccumulate microbial pathogens and describe factors that can affect
depuration (“self-cleaning”).
Shellfishes-Bioaccumulation of enterococci in the blue mussel M. edulis
Plastic pollution is a major problem in the marine environment. Plastic is normally
characterized as macro or micro-plastic. (weight 15%)
A. What is the difference between primary and secondary micro-plastic in the marine
environment.
Primary microplastics are tiny particles designed for commercial use, such as cosmetics, as
well as microfibers shed from clothing and other textiles, such as fishing nets.
Secondarymicroplastics are particles that result from the breakdown of larger plastic items,
such as water bottles.
B. Have these two types of plastics different impacts on the marine environment?
Secondary more hazardous
C. What effect does macroplastic have on the marine environment
Floating macroplastics also have apparent impacts on marine megafauna through ingestion
or entanglement. As they degrade over time, they can generate large numbers of
microplastics – and like their smaller counterparts, macroplastics can carry chemicals and
invasive species.
The figure below illustrates processes that can influence the fate and availability of
organic pollutants in marine waters. (weight 15%).
a. Describe the major processes that affect the fate of organic xenobiotic pollutants in
marine waters.
Factors Affecting Biodegradation: Several factors influence biodegradation. These
include the chemical nature of the xenobiotic, the capability of the individual
microorganism, nutrient and O2 supply, temperature, pH and redox potential.
b. A range of processes can affect the bioavailability of organic xenobiotic pollutants. What
is meant by “bioavailability” and which processes mentioned in question a. will affect
bioavailability?
Bioavailability may be defined as the ratio between the dose at the site of action and the exposure dose
Bioavailability integrates environmental chemistry and ecotoxicology concepts. The
bioavailable contaminant fraction represents the relevant exposure dose for organisms. Many
complex processes describe bioavailable exposure dose, including the mass transfer and
uptake of contaminants into organisms, which are determined by substance properties,
compartment properties, the biology of organisms, and climatic influence
c. Some organic xenobiotic pollutants are referred to as “persistent” or “conservative”
pollutants. Describe some characteristics of a “persistent” marine pollutant”?

mainly man-made synthetic compounds that do not occur naturally in the
environmentPersistent: ≈ (relatively) resistant to degradation (removal)
they are toxic; they are persistent, resisting normal processes that break down
contaminants; they accumulate in the body fat of people, marine mammals, and
other animals and are passed from mother to fetus; and they can travel great
distances on wind and ...
Conservative pollutants are substances that are inert in the marine
environment; their concentrations change only as a result of
turbulent diffusion.
Oxygen depletion in marine environments is a recurring condition that may cause
severe harm to the affected areas. (weight 10%)
a. What is oxygen depletion?
In ocean and freshwater environments, the term "hypoxia" refers to low or depleted oxygen
in a water body. Hypoxia is often associated with the overgrowth of certain species of algae,
which can lead to oxygen depletion when they die, sink to the bottom, and decompose.
Oxygen depletion is a phenomenon that occurs in aquatic environments as dissolved oxygen
(DO; molecular oxygen dissolved in the water) becomes reduced in concentration to a point
where it becomes detrimental to aquatic organisms living in the system.
b. Why are some coastal marine areas prone to oxygen depletion?