HAB LESSON PLAN - PART 1: What are the basic growth requirements for algae?, grades 6-8

(Developed by Sarah Heinzelman and C. Mengelt, 2005; revised and illustrated by B. Prezelin, 2006):

Title: "How do algae grow and bloom?"

Focus: Basic algal growth requirements

Grade Level: Grade 6/7

Focus Question: "What are the basic growth requirements of algae that feed the rest of the marine food web?"

Learning Objective:

- Students learn about the basic growth requirements of marine primary producers

- Students learn the basics about photosynthesis

- Students will hear about the diversity of algae in the ocean

Materials:

- Slide show with pictures of algae and terrestrial plants

- Colored puzzle pieces (see instructions below)

Audio/Visuals: slide projector, overhead projector, or power point projector

Teaching Time: 1 hour

Background Information:

Microscopic algae (phytoplankton) are responsible for most of the primary production in the global ocean (all the oceans and seas of the world combined). Some additional primary production occurs In shallow waters along some coastlines, due to the growth of macroalgae (eg. red, brown and green algae) such as kelp (brown algae) and eelgrass (green algae). Primary production refers to metabolism of the most basic chemicals where inorganic carbon (carbon dioxide) is transported into a cell and there converted to organic carbon (eg. sugars) using energy. In the case of algae (phytoplankton + macroalgae), the energy is sunlight. The process is called photosynthesis. Primary producers can also satisfy all other growth requirements (more details in the learning activity III) from inorganic nutrients.

Where else might you find photosynthesizers in the world ??(answer: lakes, ponds, trees, crop plants, etc). While land plants can suffer from lack of water, especially during a drought, what about algae?? (they live in water so they do suffer from water stress). However, the nutrients for plants to grow are more dilute in seawater than in soil . And land plants and most macroalgae stay in one place while phytoplankton float around in the sea. Might these facts help explain why phytoplankton are very small (microscopic) and land plants can be gigantic? Why aren't there any ocean-going trees?

During this class we will focus on the small algae, invisible to the eye except when they form a dense bloom and discolor the ocean to a green, red or brown color, depending upon which algae is most abundant. From the slide show we can see how small algae are and how diverse they are in shape. Comparing them to the terrestrial plants makes us appreciate the fact that besides being the primary producers they have nothing in common. Microalgae are unicellular, have no leaves, no roots, no flowers... it is only when we look more closely we see some of the common features. For example the long spines on the diatoms, they are believed to have evolved as feeding deterrents just like the thorns on roses or cacti. Why do you think they have so little in common? How did the evolutionary forces differ in the two environments? What do they have in

common?

Despite their many differences in shape all the plants and algae shown have the same function in their ecosystem: They are the primary producers, the base of every food chain. In the learning activity III photosynthesis is explained in a little more detail.

Most marine algal blooms start when a pulse of inorganic nitrogen is provided to the surface water. Inorganic nitrogen (eg. ammonium and nitrate, NH4 and NO3) is usually most abundant deep in the ocean, in colder waters. This source of inorganic nitrogen, needed for algae to make proteins and DNA/RNA from sugars synthesized in photosynthesis, are mixed upward and can come to the surface when strong wind are blowing. These same kinds of nitrogen sources are found in fertilizers like Miracle Grow, but in much higher concentrations than in the ocean. . After a pulse of rich nutrient water occurs, phytoplankton cells divide (in two) rapidly and the total abundance of cells increases exponentially and this growth results in such high concentrations that the algal bloom is visible by the concentrated color of the algae in the water. Algal booms can be rich food for grazing animals who can catch them and/or filter them out of the water (filters are so fine nets, that the small phytoplankton are caught on the filters and from there are moved to the animals gut). Animals that eat plants only are herbivores. In the ocean animals that float are called zooplankton. And it is mostly the smaller zooplankton, micro-zooplankton, that are herbivores. They, in turn are eaten by larger zooplankton (carnivores), which are eaten by larger animals and so on up the food chain (see Lesson #3)

The more frequent and intense the upwelling of nutrient rich water occurs the richer the food chain above it. That's why the coast of Peru and of the US West coast are such rich fishing grounds, as the interplay between the coastline and winds provide many opportunities for upwelling of deep nutrient rich water.

Learning activity I - Phytoplankton slide show

1) Slide show with phytoplankton and macroalgae images, contrasting it with land plants. See numerous links to images on internet and incorporate images in handouts and/or powerpoint presentation.

2) Discuss the differences in the environment (terrestrial versus aquatic) that might have caused this functional group, i.e. the primary producers, to evolve so differently.

Learning activity II - BASIC GROWTH REQUIREMENTS: Make a puzzle

1) Students split up into groups of 4-5 students

2) They each receive puzzle pieces (please cut from stencils available online or in craft store; overlay on a picture of single algae glued to thin poster board and cut puzzle pieces, a minimum of 7 pieces) To the corner of each piece attach a label, sunlight, carbon dioxide gas, water, nitrate, phosphate, trace elements (e.g. metals like iron and magnesium) and, lastly silicate only if it is a diatom....omit it otherwise other wise). Some blank pieces can be left if you wish a bit more complex discussion.

Alternatively, you can follow a different and simpler approach to the puzzle, based upon photosynthesis as the driver of metabolism ,and directions to make such a puzzle are given at end of this lesson plan.

3) Have students helps with putting together puzzle pieces to make a square, each of which symbolizes symbolizing a complete algal cell (in order to obtain a square they will need a piece with sunlight (+CO₂+water), nitrate, phosphate, trace elements, and silicate)

4) Tell the students to put together all puzzle pieces even if they don’t obtain a complete square (e.g. you haven't given them a missing piece or they have blank pieces that they discuss what else might be required for a cell go grow...e.g. vitamins, chelators, sulfate, salts, etc).

5) Discuss at the end with the students what elements they were missing to complete the squares. In the case where they are missing silicate, the students still get a viable algal cell, it just wouldn't be a diatom, since they require silicate. In the case where the missing piece is nitrate they would not have a viable algal cell since that is a basic nutrient requirement of all algal cells

Learning activity III - Review and explain what they learned from previous game about the basic algal growth and physiology:

They are called phytoplankton for a reason: "Phyto" meaning plant - this means they are photosynthesizer. "Plankton" meaning drifter, which means they are moved along with the ocean currents and waves, and have to use the resources that surround them as they move.

What parts of the puzzle pieces are needed for just photosynthesis to occur? (water, carbon dioxide, sunlight).. if any is lacking, photosynthesis will not occur.

What is the organic matter (product) that photosynthesis produces? Sugar (only made of C and O2 from CO2 and H from water ). C₆H₁₂O₆

How photosynthesis works: (show diagram)

The process illustrated above takes place in the chloroplast (one of many organelle types in a cell, only found in plant cells) of an algal cell (as well as terrestrial plants). Light is captured (absorbed) by chlorophyll a - a pigment that is present and has the same function in every plant and algae. The energy captured in this chlorophyll molecule can be compared to the process when a coiled spring is stretched and is consequently under tension. This energy, this resonance (like in a guitar string when plucked or tuning forks when hit), is just the right amount that once it is released it splits water into its components (Oxygen and Hydrogen) and in that process frees an electron. This process is somewhat equivalent to making electricity from solar panels. However this energy needs to be turned into a form that can be stored for later biological processes. So just like the energy gained from solar panels is stored for later us in batteries, the energy from the first step in photosynthesis is converted into a form that can be stored, it's converted into ATP or NADPH, which is the equivalent to our battery storage. This ATP/NADPH is later used for all kinds of biological processes. Most importantly it is used for the "synthesis" part of photosynthesis, where carbon dioxide is used together with ATP/NADPH to make carbohydrates. This last step does not require light anymore as the light energy is stored in those molecules (ATP/NADPH).

What else they need for living:

Consider the other labels on your puzzles; these are the other resources necessary for algal growth. What are they used for is sugar is made by photosynthesis? (can't live on a sugar diet!)

- Nitrogen (NO₃, NH₄)...proteins, DNA

- Phosphate....ATP, ADP, Pi, (all regulatory, turn different metabolic pathways on or off)

- Silicate...essential to make shells of diatoms and regulates their metabolism

- Trace elements (iron, copper, etc)...vitamins, magnesium (Mg) is in chlorophyll, oxidation-reduction enzymes, etc

Depending upon level of class, can talk about a wide variety of cell compounds.

Explain to the students the concept of one limiting resource:

Lack of any needed element or resource to build cell compounds will cause cells to slow growth. If cells slow growth (divide less often), a needed resource must be limited (not abundant enough to support fastest growth possible). But which one? They are not all needed in large amounts, some just a minor amount (eg. Trace metals, vitamins, etc). And too much of some compounds (metals) is not a good thing and it can become toxic, so adding a lot of fertilizer may actually kill most phytoplankton.

So in order to get an algae to grow, or to put together a square (an algae in your puzzle) you need all these pieces. If you run out of silicate first you will still get algal growth but you end up with a different group of algae, diatoms can not grow without silicate, therefore you get dinoflagellates or other species of algae that don't require silicate. But once you run out of a nitrogen source (nitrate, ammonia) you cannot put together another algal cell that means you will not get algal growth.

If I (the teacher) were to come around and give you more nitrate puzzle pieces, what would happen? Right, you could grow more algae. If this addition of puzzle pieces that are missing to build algae comes from man-made sources, such as the fertilizers we use on our lawns and the farmers use to grow crop, it might lead to a much bigger bloom than the environment in its natural state would see. This might lead to a problem that is called " eutrophication", a form of water pollution. It's defined as unusually dense algal blooms resulting from anthropogenic (related to human activity) input of nutrients to the water with negative consequences to the aquatic ecosystem. Most often it causes lakes or estuaries to turn very dark green and impacts animals that live there negatively. This use to happen a lot when detergents for washing contained lots of phosphate..the phosphate would run down the drain and into the local waters where they caused the phosphate-limited algae to grow in massive amounts. When it was discovered what was the cause of this eutrophication (good growth conditions), phosphate was band from detergents and fewer blooms occurred. We will talk about the potentially negative outcomes of an algal bloom in our next class.

Extension:

The experiment described in the next lesson plan (HAB-lesson plan) could be incorporated with this lesson plan instead. The lesson plan could also be extended to introduce students to the basics of cell biology, by talking about the chloroplast and mitochondria, the basic cell organelles common to all plants and latter to all animals.

Evaluation:

Have students in group of 4 discuss the following problem:

Let's say the group would want to start a business producing fish food from marine algae. How would they go about it and what might be some of the problems the business venture would face? Would you produce the algae in a warehouse or in the ocean directly? Would you artificially stimulate growth, like farmers do with their crop?

Conclude with a class discussion on their findings.

Science standards:

Grade 6: Ecology 5 c-e

Grade 7: Cell Biology 1 a , Evolution 1a

Instructions to make puzzle:

1) print (20) copies of the front (colored surface) per student group

2) if possible to match up, print 'nutrient labels' onto the back of the colored surfaces otherwise, just handwrite the labels

3) cut along the black lines, so that each square yields 5 puzzle pieces

4) once pieces are cut out remove 5 nitrate puzzle pieces and 10 silicate puzzle pieces, so that students only receive a total of 10 complete squares

	Front:		Back: