Lake stratificationis the separation oflakesinto three layers, two main layers (top layer and bottom
layer) and one layer on the middle which separate the two main layers, the
separate of these main layers would influence the concentration of the
nutrients on the layers, it's happening during the summer season and reduce the
concentration of the nutrients on the top layer, because all the nutrient will
This picture/graph shared under Creative Commons Licenses, Ecology for Engineers Course, Technion institute, Haifa
We can see in this graph the two main layers
separated and there is a change in the
temperature at different depths in the lake, in addition of the temperature,
the nitrogen separate (it is known that there are two types of nitrogen, the
atmospherical nitrogen and thedissolved
The red section shown in the graph is the warm
water, the blue section is the cold water, and we can see the sharp raise of
the temperature between the layers.
This video shared under Creative Commons Licenses, youtube
Recently the bloom became popular because of
the global warming, that rise the temperature all around the world.
As you learn from the
is the preference of the algae that lives on the top layer of the lake and
how does it effect the bloom?
Your question is very interesting. The attached film is related and presenting the issue clearly.
I think you can improve your presentation by writing the question and the answers more clearly.
Here is my suggestion to rewrite the question:
Algae blooms in lakes and seas occur in specific environmental conditions. The bloom is a seasonal but some years it does not appear at all. Under certain conditions a massive blooms accurse.
Please watch the attached film and figure out what are the environmental condition that increase Algae blooms
And the right answer should be:
The bloom consists of a large number of cells in a very high concentration that forms colonies.
Strengthened when the following conditions are met: the water has a high concentration of nutrients in the lake . In addition, the weather conditions are good for the algae - sun, heat and lack of winds are perfect for creating a rash.
The harmful Algae Bloom is a relevant issue to the country and to the
rest of the world. We can see the connection between the Global Warming and the
increase in the number of such incidents of Algal Blooms worldwide.
When I read your question I did not
understand immediately what is the intention of the question.In addition ,the Detractors
contain a correct answers, For example, Heat and Nutrients: algae thrives in
hot water that filled of nutrients .Such environment exists in the upper
layer of the sea.
I would suggest to rephrase the
question, that the intent will be
clearer, In addition I would suggest to link the question to the Global
Warming, which has a big effect on Algal Blooms worldwide.
It is the first time I read about Algae and Algae bloom, and I enjoyed
reading your question and gained knowledge - high quality question.
I have few comments and suggestions, and for that I would divide your entire
question into several items:
1.The introduction (Lake
Good and short intro of the phenomena. As it is a new concept for me, I quickly
understood it and I think it is well serves its purpose.
2.Graph + text (on the
temp. depth & nitrogen):
Great to have graphics in the question which can explain a lot w/ minimum
text. The graph and text are good but I think it can be better: the text
section beneath the graph can be reduced and you may add notes and arrows on
top of the graph so the graph will be self-explanatory e.g. adding note to
explain the black lines, another note for the orange and the blue sections.
Thus the learner can find a much of the info he needs in one place (the graph).
In addition, you may add the global-warming concept in the text section
as it is related to the rising of the temperature.
3.Video (Algae bloom in Lake
Erie near Toledo, Ohio) + View
points on the map:
These 2 parts show excellent and various examples of the issue, the relevant parameters, the risks, affect on
humans/animals (echo system) and ways of dealing w/ that. They show that the
issue is a global risk (points in the map from US, china, Israel) – very important
for the learner so he can be more connected to the issue.
I would have reduced the amount
of text and the font size in the Western-Coast video (point in the map – San Francisco)
– the video tells almost all the info you need on that example.
I would have added text to
the china point in the map, short explanation about the example in china – not a
must but nice to have (the video shows all you need to know).
Change text format in the
Eilat point: the sentences are very long, going out of the normal frame –
Too much text in the Yigal
Alon Laboratory point, I have a suggestion for text improvement:
"The Kinneret Allon Limnological Laboratory (A.K.A KLL) is a
relatively big laboratory w/ the following goals:
Most important goal is determine whether the quality of the water is
good enough for national supply or not (by collecting weekly samples from
different places in the lake, analyzing them, which will be transmitted into
real-time data for laboratory database) – many chemical, physical and
biological parameters in addition to major environmental factors are being
Monitoring activities to provide data, information and advice to several
related governmental agencies working in the area – growing importance to these activities.
Examing topics e.g. the structure
and function of the lake ecosystem, responses of the lake ecosystem to water
level fluctuations, the effect of human activities and agricultural/urban
developments on the lake system, transport processes of nutrients and
pollutants into the lake and their bio-geochemical cycles within the lake and
many other topics.
These activities are being carried out by 30 scientists, research
assistants, technicians and students carrying out research projects for
4.Question itself +
Very relevant question to the subject as it is not only related directly
to Algae bloom but also integrates all the aspects shown in the intro, grap,
text, video and the points on the map. I think that for a learner to answer correctly,
he/her should understand these aspects well before answering the question.
I see a strong correlation between the question parts, each part is
relevant to the subject (Algae Bloom), adds info and each part is complementary
to the other parts, thus creating almost a full picture to the learner.
The contributions by each part to the entire question:
·Scientific and technical
background: contributed by the intro (Lake stratification), the graph and
the text section.
·Examples around the
world, risks and impacts on echo-system: contributed by the video and the
points in the map.