HAB LESSON PLAN - PART 2: How Can Phytoplankton Be Harmful?? , grades 6-8 (Developed by Sarah Heinzelman and C. Mengelt, 2005; revised and illustrated by B. Prezelin, 2006):

Title: "How can something so tiny be so bad?"

Focus: when algal blooms become harmful

Grade Level: Grade 6-8

Focus Question: "How can something so tiny kill fish, birds & marine mammals"

Learning Objective:

- Students will learn to recognize the connection between human activity on land and the marine environment

- Students learn the definition of eutrophication

- Students learn about basic experimental design

- Students learn to quantify experimental results and explain results

Materials:

- phytoplankton net or bucket

- 20 ft. line to attach to the bucket

- jars (pickle jar size); 4 per experiment

- Miracle grow

- Mixing jar for miracle grow

- Labeling tape or stickers

- Eyedropper, Pasteur pipette or if not available measuring spoons

Audio/Visuals: none

Teaching Time: Most of one day for field collection and experimental set-up, 1 hour,. five times, for sampling and cell counts evenly spread over 2 weeks after the experimental setup; 1/2 hour for group discussion on results and conclusions on why some blooms can be harmful.

Background Information:

We’ve seen from the pictures shown in the previous lesson that algae can be very small, e.g. microscopic... It is difficult to imagine that a few types of these unicellular plants can make shellfish, fish, birds and dolphins sick and sometimes even kill them.. Why and how do algal blooms become harmful to higher trophic levels, sometimes even to us humans?

The way algal blooms can become harmful to higher trophic levels is in three ways:

1) As we'’ve seen in the slides, some of the algal species have quite long spines. If a bloom is mostly consisting of such algal species, they can cause strong irritations in the gills of fish. As a protective response to the mechanical irritation fish will produce mucous in the gills, which at too high concentrations can suffocate the fish.

2) Otherwise edible and benign algal species will become harmful if they are growing to concentrations so high, that their eventual decay and metabolic consumption by microbes causes a severe depletion in oxygen (remember, when microbes decompose dead material, they consume oxygen). The lack of oxygen will suffocate fish and be even more detrimental to the animals that grow at the bottom, since they often are sessile or move only very slowly, like the starfish. This condition is called anoxia and is quite often responsible for large fish kills, especially in harbors, estuaries and enclosed bays.

3) Lastly, some algae produce toxins, which are special chemicals, that when eaten can poison the animal consuming them. While the animal may not die, it appears that poisoned animals have a more difficult time reproducing. The number of such algal species and the associated toxins is getting larger as scientists find ways to identify them in natural communities and to test them for toxicity and to discover what kind of toxin is present and how it works. Sometimes the toxin does not hurt the animal, like shellfish, but does make humans who eat them sick.. Most of these toxins would also be very detrimental to humans. That's why state Health Departments keeps a close tab on toxin levels in shellfish along most coastlines. They also close sport harvest for shellfish during the summer months when most of the harmful dinoflagellates occur. However, in recent years the additional occurrence of toxic diatoms have made shellfish dangerous for human consumption even outside the annual quarantines and have increased the risk of human illnesses due to sport harvest of shellfish and sometimes even fish.

Note: Being toxic is just one way that algal blooms are harmful. A Harmful Algal Bloom (HAB) may or may not be toxic.

Given that the entire food chain depends on the primary producers ,it is important to understand why algal blooms occur before they become harmful. Unfortunately that is a very difficult question to answer and there may be different answers for different places or different times at the same place. We know that nutrient pollution (the flow of excess nutrients from land to the ocean, from agricultural use of fertilizer or sewer systems) is one of the most important causes for anoxia. The phenomenon of harmfully dense algal concentrations as a consequence of nutrient pollution is termed " eutrophication" and has been studied for a long time. It also has been aggressively combated, in many freshwater watersheds successfully.

Only recently, however have scientists acknowledged that eutrophication might also threaten coastal systems, and researchers wonder if some of the toxic blooms could be explained by nutrient pollution as well. It is important to stress at this point though that scientists don’t even know yet if these harmful blooms are more frequent, although it is often reported in newpapers that they are more frequent than in the past. Once the nature of harmful algal blooms was started to be widely understood, many more scientists and public members watched the beaches more carefully and reported sightings of bloom and/or sick animals to places that keep records (e.g. Fisheries, state health departments, conservation groups, universities, etc.) It is also not known whether, as a consequence of large algal blooms along the coast, if the marine ecosystem has changed such that higher trophic levels are more frequently affected by their harmful effectsy.

Learning activity I - EUTROPHICATION EXPERIMENT

1. Go to your nearest lake, pond, or ocean site with calm water. In case you want to sample from the ocean, off of a pier will work best.

2. Use the net tow, or if not available, simply collect water in a jar, bucket, etc. Collect at least three tows, depending on how many particles/organisms it looks like are in the water (just look with your eye). If the water looks completely clear, try to let the net sink deeper or try moving to another spot. Keep collecting samples until there is a thick coloration. Collect at least 500 mL of water.

(If time or location does not allow for field collection, contact local aquarium stores for availability of algae)

3. When you get back to the classroom, separate the larger sample into 4 X 50 -100 mL smaller samples (depending on how much you collected). You may have water left over. For the smaller samples, have students bring in a pickle jar, water jug with the top cut off, or something large enough to fit at least 150 mL of fluid in it. Each of the 4 smaller samples will serve as a treatment. One will be a control, to which nothing is added. Different amounts of Miracle Grow (a source of nitrate, a limiting plant nutrient) will be added to each of the remaining three treatments.

4. Add 1 teaspoon of miracle grow to 250 mL of distilled water (bottled water will do) and mix well. We are using de-ionized water or bottled water as to not contaminate our experiment with trace metals, nutrients or chlorine from tap water.

5. Using a pipette or eyedropper, determine some sort of small unit (i.e. one half or a third of the pipette). To the first treatment add 1 unit of Miracle Grow, to the second treatment add 2 units of Miracle Grow and to the third add 4 units of Miracle Grow. (You are welcome to do replicates of the treatments, or different amounts of Miracle Grow if there are a lot of students in the class, etc.)

6. Take a drop of water from each sample and look at it under a microscope, 10x magnification will work. Allow the students to observe the slides and see how many phytoplankton/zooplankton are in their samples.

7. Allow one student from each group (every student will have a chance to do this) to count the amount of phytoplankton they see in the one field of view, repeating this several times with different field of views of the same sample. An average of the numbers counted will give them an idea of how much would be in their whole sample, and then of course, the ocean.

8. Place each treatment near a window, but out of direct sunlight, but where they will get about the same light. Be careful not to put the samples where they will get too warm, as they usually come from much cooler habitats. They will be observed every few days and the phytoplankton in one drop of water will be counted by a different student in each group under the microscope. The class can compare numbers to see how the different treatments affected the growth of the phytoplankton.

(** Fill in the blank depending on how the teacher fits the experiment into their lesson plan and how much time they have.**)

IMPORTANT: Many water bodies (marine and freshwater) of the world are being invaded by plant and animal species that don't belong there. They have been introduced due to people's careless activities and have the potential to change the natural ecosystem and its indigenous food web. So, please tell your students not to dispose of any live algae or animal from the experiment down the drain. Before anything is "dumped" it has to be killed first. A good way is to add bleach (a 10% solution is plenty) and let it sit overnight before dumping it down the drain. Of course students should not handle bleach, as it is very harmful to skin and eyes, unless supervised very closely. THANK YOU for protecting our local species!

Learning activity II - Experimental results and analysis:

- Have each experimental team graph their results and discuss the possible differences or inconsistencies in class

- Students should put their data into a table and graph it the following way (note, the data from the experiment is not expected to resemble this data, since it's made up and represents the ideal case, where the algal growth responds only to the treatment variable and not to any confounding variables¹⁾, which is very often the case in a biological experiment):

Table:

	Treatment 1	Treatment 2	Treatment 3	Treatment 4
Day of	Number of	Number of	Number of	Number of
Experiment	Algal Cells	Algal Cells	Algal Cells	Algal Cells
[days]	[cells/L]	[cells/L]	[cells/L]	[cells/L]
0	8000	11000	10000	10900
3	11000	14000	12000	25000
6	13000	19000	30000	60000
9	20000	40000	80000	128000
12	15000	60000	90000	234000

Graph:

¹⁾ Confounding variables are other conditions that vary between the experimental treatments unintentionally. In this case it could be the following: varying temperature, different starting conditions (i.e. sample was not uniform before it was split into the different jars), different light condition, etc.

Learning activity III - What happens when an algal bloom gets out of control:

Have students discuss in groups of 4 or 5 ways in which they think algal blooms can become harmful. Discuss reasons why they would grow out of control and mechanisms by which they would harm the ecosystem. At the end, have an in-class discussion of their findings and make sure the points listed below are covered and understood.

Discussion outcome:

As the students now seen in the experiment, if you led these algae grow unchecked either because too much of the nutrients were added or not enough grazers were around or both, they just keep growing.

Now at first sight you would think more food isn't bad, right? But these are some of the basic ways too much algae can become harmful:

a) When the algae die they settle to the bottom of the water column, where they will be eaten by microbes, which decompose all detrital material. Because there is a lot of respiration associated with all that decomposition, the oxygen near the bottom is being depleted. In shallow waters, such as harbors, estuaries and bays this means that much of the water column will become anoxic, void of oxygen, which is necessary for local animals to breath. This often kills fish and more importantly the animal community at the bottom that is typically less mobile than fish.

b) Certain algal species can kill organisms just by being the wrong shape. If you get too many of those algae that have the wrong size or shape they can kill. For example certain diatoms with their long spins can irritate the gills of fish to the extent that they fish over-produce mucous to fight the irritation that they eventually suffocate from the accumulation of mucous. In some instances the algae are too small so that they clog the feeding apparatus of shellfish.

c) Lastly, as we've read in the newspaper article, some algal species produce toxins. There are many different algal toxins worldwide, too many to list. The most prominent on the West coast of the US are saxitoxins, from dinoflagellates, that cause paralytic shellfish poisoning (PSP) and domoic acid, from certain diatoms, which cause amnesic shellfish poisoning (ASP).

Other activities:

This lesson plan could be extended to include experiments with phosphate additions from detergents, by varying the amount of light the algae receive, or by including grazers caught in the net or obtained from an aquarium store.

Science standards:

Grade six: Investigation and Experimentation 7 a-e,

Grade seven: Investigation and Experimentation 7 a-c

Grade eight: Investigation and Experimentation 9 a-g