P la nk t o n La b (3-6(3-6)) Overview: In this activity, students will collect a plankton sample from the slough and study the sample under microscopes. Then they will build a slough food pyramid to show the importance of plankton in the slough food chain. Content Standards Correlations: Science, p. 293 (2016)
Grades: 3-6 Time Frame for Conducting This Activity Recommended Time: 30 minutes Key Concepts: The open water Introduction and sloughs of San Francisco (5 minutes) Bay contain an abundance of • discuss the slough habitat microscopic or nearly micro- • introduce the terms “phytoplankton” and “zooplankton” scopic life called phytoplankton • discuss the use of the plankton net (small, drifting plants) and Collecting Plankton Sample (10 minutes) zooplankton (small, drifting • walk to the bridge with the students and the plankton net animals). Plankton plays an • help the students collect two plankton samples important role in the Bay, Observing Plankton (10 minutes) forming the base of food • distribute the plankton samples between the petri dishes pyramids that support mud • observe and identify plankton, using the hand lenses and creatures, fish, birds, and even humans. microscopes • ask discussion questions while observations are being made Objectives: Building a Food Pyramid (5 minutes) Students will be able to: • hand out wooden food pyramid blocks • collect a plankton sample, • guide the students through construction of the slough and using a plankton net mudflat food pyramid • observe, draw, and identify a variety of planktonic plants HHHooow Thihihis AAs ccctttiii vvviii ty RRty eeelalalattteees tts o tto hhhe RRe efefefuuuggge’s RRe’s eeesssooourururccceeesss and animals • describe the importance of What are the Refuge’s resources? plankton in food pyramids • significant wildlife habitat Materials: • endangered species Provided by the Refuge: • migratory birds • 1 plankton net with rope What makes it necessary to manage the resources? • 2 plankton net bottles • Pollution, such as oil, paint, and household cleaners, when • 12 petri dishes dumped down storm drains enters the slough and travels • 12 slides through the food chain, harming animals. • 12 eyedroppers What can students do to help? • 12 hand lenses Refuge staff study pollutants found in the Bay to see how they • 1 set plankton identification affect wildlife, but we need your help. cards • Never dump anything down storm drains. • 1 food pyramid blocks set of • Participate in Coastal Clean-ups. (17 blocks) • 6 microscopes • Tell others what you have learned. • 2 extra glass bowls for samples • bucket for recycling used samples Provided by the Educator: • data sheet, one per student • pencils (both optional) California Gull
200 Field Trip Activities: Habitat Studies SSSupupuppppooorrrtttinining InIng fofoformarmarmatttiii ooon fofon r TTr hihihis AAs ccctttiii vvviii tytyty portion of the oxygen found in the air Slough we breathe. • If the palm of one’s hand is used to represent • There are three main types of phytoplankton: San Francisco Bay, tidal sloughs may be nanoplankton, diatoms, and dinoflagellates. thought of as “fingers of the Bay,” winding • The nanoplankton are defined by their through the salt marshes. extremely small size. Nanoplankton’s impor- • Sloughs are natural waterways that carry water tance has only recently been discovered—off from the Bay into salt marshes as the tide comes in, the central California coast; for example, and returns the water to the Bay as the tide goes nanoplankton account for 60-99% of the food out. and oxygen produced! • Sloughs carry Bay water into the marshes twice a • Diatoms are much larger than nanoplankton, day during the flood (incoming) tide and back to the yet it still takes a microscope to see them. Bay twice a day during the ebb (outgoing) tide. • They are single-celled algae encased in • Mudflats appear in the slough channels during two-part silicon (glass-like) shells. when ebb tide. • Like all plants, diatoms need sunlight. They • Tidal waters transport detritus (decomposing marsh have various adaptations to keep them near plants and animals), phytoplankton (small, drifting the surface and near sunlight. plants, and zooplankton (small, drifting animals). • Increasing surface area is one strategy • Detritus and plankton form the base of food for retarding sinking. Diatoms may pyramids in the slough, mudflats, and open Bay, have long spines, may be round and supporting mud creatures, fish, waterbirds, flat, or may form long chains. shorebirds, harbor seals, birds of prey, and even • Diatoms can also regulate their density. humans. Some contain oils while others may • Phytoplankton exists in high abundance in estuaries, have a gas bubble inside their bodies. such as the San Francisco Bay, where the combi- • Dinoflagellates, while considered members of nation of river currents and tidal currents trap the phytoplankton, have characteristics of both nutrients necessary for plankton growth. plants and animals. • Like plants they contain chlorophyll which Plankton allows them to convert sunlight into food • The word “plankton” comes from the Greek word and they have a plantlike cell structure. planktos meaning “drifting.” • However, like animals, many varieties eat • This ecological term refers to the community of microscopic pieces of matter found in the plants and animals that drift in both fresh and water. Some dinoflagellates even eat each marine bodies of water. other! Dinoflagellates also have two • Currents and tides carry plankton through the whiplike appendages which provide some water. mobility. • Some plankton are fairly large, such as jellyfish, • Some dinoflagellates produce a toxin which but most are microscopic in size (not visible by causes mussel poisoning. During the the naked eye). summer months, mussels or other shellfish • Planktonic plants are called phytoplankton. eat large amounts of these dinoflagellates. • The primary importance of these plants, like Quarantines are established to prevent plants on land, is their ability to photosynthesize. people from eating these shellfish because Using chlorophyll, they capture the energy of they would become seriously ill. the sun to make food, releasing oxygen in the • A “plankton bloom ” or plankton population process. explosion, results when the water is • Virtually all aquatic life depends upon these unusually rich in nutrients. microscopic single-celled organisms for • Some species of dinoflagellates may food. Phytoplankton is the main source of occur in such numbers that they color food for zooplankton. the water a dark red, otherwise known • Phytoplankton also contribute a significant as “red tides.”
Field Trip Activities: Habitat Studies 201 • Some red tides may result in the • Ostracods are also small crustaceans, death of large numbers of fish, with a hinged, two-sided carapace (shell) because the plankton use up so that resembles a clam. Their antenna are much oxygen; there is not much left used as sensors and to assist in swimming. over for other marine organisms. Ostracods crawl along surfaces using two • Dinoflagellates are luminescent at night, pairs of legs with clawed tips. producing a soft glow when the water in • Another common type of zooplankton are which they float is disturbed. rotifers. Rotifers are almost constantly in • Planktonic animals are referred to as zooplankton motion, beating the cilia at their heads to (zoo is pronounced like toe). Many zooplankton are move and to bring food to their mouths. able to move up and down in a water column, When feeding, rotifers attach themselves to pursuing food and escaping predators. However, a bit of debris and the rapid beating of the their small size prevents them from moving against cilia draws a current of water towards the the currents. mouth. • Some zooplankton live their entire lives as part • Other species of zooplankton are planktonic of this drifting community. (drifters) only as eggs or larvae, then become • Copepods are the most numerous of all free swimming or sedentary (stay in one place) animals; they are small crustaceans that during their adult stages. Among the myriad of grow to 2 mm long and use their long, organisms included in this latter group are sea sensory antennae as rudders to direct urchins, sea stars, crabs, barnacles, clams, movement. mussels, sea snails, and many species of fish.
PPPlalalanknknktttooon IdeIden nnntttiii fffiii cccaaatttiii ooon GuideGuiden Phytoplankton
Diatoms Dinoflagellates Zooplankton
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Copepod & Copepod Larva Fish Larva
202 Field Trip Activities: Habitat Studies How to Lead This Activity by FollowinFollowingg Read t h e "Do , R ea d , A s kk"" T ea c hin g Fo rma t “The thin netting of the plankton net will allow water to flow through, but not all of the plankton. Very Introduction (5 minutes) small plankton will be able to get through the netting, Read but larger plankton will be collected in the bottle “We are going to study the microscopic life of the attached to the bottom of the net.” slough habitat and its importance in this slough food pyramid.” Collecting the Plankton Sample (10 minutes) Do Ask Take the plankton net and two of the plankton net ? What is a definition for “habitat”? (A habitat bottles and walk with the group of students to the is a home for a plant or animal. A habitat provides bridge that crosses the slough. Attach one of the food, water, shelter, and space suitable to the plankton bottles to the bottom of the plankton net. organism’s needs.) Keep track of the bottle caps, you will need them later. ? What is the slough? (If the palm of one's hand is used to represent the San Francisco Bay, tidal Ask sloughs may be thought of as "fingers of the bay," ? What is the color of the slough? (Green- winding through the salt marshes. It is a natural Brown.) waterway that carries bay water into and out of the ? What factors alter the water color of the marsh with the tides.) slough? (The phytoplankton that grow in the water, ? What are some animals that live or feed in the amount of small particles that are suspended in the slough? (Several different kinds of fish, includ- the water, water depth, and the soil color.) ing gobies and smelt, mud creatures, such as crabs, mussels, clams, and snails, and many different types Read of birds, including egrets, herons, terns, shorebirds, “I need one student to tie the end of the string and ducks.) connected to the plankton net to the bridge railing. ? What are the small animals drifting in the This is very important so we won’t accidentally lose water of the slough called? You need a micro- the plankton net. I need another student to throw the scope to see some of these animals. (Zooplank- plankton net into the slough.” ton.) ? What are the small, drifting plants living in Do the slough water called? (Phytoplankton.) After the student throws the plankton net into the slough water, allow the net to "skim" the surface of Read the water for a couple of minutes, Do not allow the plankton net to drag along the bottom of the slough or “There are many different types of phytoplankton and the sample will be muddy. zooplankton living in the slough. We are going to collect our own plankton samples at the slough, using Read a plankton net. We will bring the samples back to the table so that we can study the plankton, using micro- “I need two students to work together to pull up the scopes.” plankton net and sample.”
Do Do Show the students the plankton net. Allow them to • When the sample is pulled in, remove the bottle touch the netting carefully. from the bottom of the net. Be careful to not spill the sample. Put a cap on the bottle. • Put a new, empty bottle on the plankton net. Collect one more sample, allowing different students to participate in the collection. Walk back to the study area with the plankton net and the two samples.
Field Trip Activities: Habitat Studies 203 Observing the Plankton Sample (10 minutes) capture as much light as possible.) Do ? Dinoflagellates convert sunlight into food Back at the study area, distribute the plankton sample using chlorophyll and they eat microscopic (from the plankton bottles) among the students’ petri matter in the water. They also have two whip- dishes (put very little water in each of the petri like appendages which allow some mobility. Are dishes). dinoflagellates phytoplankton or zooplankton? (They are actually considered plants, but they have Have the students observe their samples under the characteristics of both plants and animals.) microscopes. Encourage students to move their dish ? What part of a life cycle of a fish could be around under the microscope in order to examine the considered a zooplankton: eggs, juvenile, or an entire sample. They can also make slides of their adult? (Eggs. Many aquatic animals are planktonic samples. (drifters) as eggs or larvae, then become free swim- ming or stay in one place during their adult stages, If copies of the plankton data sheet and pencils were including crabs, clams, mussels, barnacles, snails, and provided by the teacher, direct the students to draw many fish species.) several of the organisms they see under the micro- Can you think of an example of a very large scope. ? animal in the ocean that feeds only on plankton? (Some baleen whales, such as humpbacks and blue Using the plankton identification cards on the table, whales, feed primarily on krill, a zooplankton.) instruct the students to attempt to identify each organism they draw or find. Do not worry if they ? What is the connection between phytoplank- cannot find the exact species— there are thousands ton and oxygen? (Phytoplankton are the prime of different kinds of plankton. For example, there are producers of oxygen. Without them the Earth's some 20,000 different species of diatoms! atmosphere would lose a major source of oxygen.) ? Why is plankton important to humans? (We While observations are being made, ask the students breath oxygen produced by phytoplankton, we eat the following questions. fish, shellfish, and ducks that depend on plankton.) ? How are phytoplankton important to all life in Ask the Bay and the sloughs? (Phytoplankton are the ? What is a definition for “plankton”? (Plants or base of Bay and slough food pyramids, along with animals that drift in water.) detritus (decomposing marsh plants). Phytoplankton ? How do plankton move? (Plankton, as their and detritus support mud creatures, fish, and birds.) Greek name “planktos” tells, drift in the water. Currents and tides carry them from place to place.) ? What is the difference between phytoplank- Building a Food Pyramid (5 minutes) ton and zooplankton? (Zooplankton are animals Do (consumers) and phytoplankton are plants (produc- Ask the students to set aside their samples and use ers).) the area next to the tables for constructing a slough ? Can you describe a food chain in the slough, and mudflat food pyramid from the wooden blocks. having at least 3 members, including phy- Read toplankton and zooplankton? Hint: the produc- “We have been studying the plankton that lives in the ers need to be on the bottom (One example: slough. Next we are going to build a food pyramid.” phytoplankton —> zooplankton —> fish —> people.) ? Are diatoms a type of zooplankton or phy- Ask toplankton? (Phytoplankton. Diatoms are single- ? What is a food pyramid? (A food pyramid celled algae encased in silicon (glass-like) shells.) represents passage and loss of energy as levels of ? Why is it important for diatoms (phytoplank- producers and consumers feed on each other.) ton) to float near the surface, rather than sink to the ocean bottom? (Diatoms need sunlight to make Do food. Floating near the surface allows them to Pass out one or two wooden blocks to each student 204 Field Trip Activities: Habitat Studies (17 blocks total). Guide students through the con- Phytoplankton produces oxygen that humans and struction of the food pyramid (see illustration below). other animals breath.) Ask ? What happens when pollution, such as motor ? What is at the base of any food pyramid? oil, paint thinner, or pesticide, is poured down (Plants, which produce their own food or energy from storm drains? Could this pollution affect plank- sunlight.) ton? (Storm drains run directly to creeks and rivers ? What are the producers in the slough? which drain to San Francisco Bay. The plankton in the Bay and sloughs can be killed by pollution or (Phytoplankton (tiny, drifting plants) and detritus plankton can absorb or eat pollution and then be eaten (decomposing marsh plants).) by mud creatures and fish which are then eaten by Do birds, causing health problems in the fish, mud Ask the students with the blocks labeled phy- creatures, and birds.) toplankton and detritus to put together the first ? What would happen to the food pyramid if the level of the food pyramid on the table. plankton died because of pollution?(The food Ask pyramid would collapse.) ? Feeding on the producers are the first level Do of consumers. What are the small, drifting Have two students pull out the two phytoplankton animals that feed on phytoplankton and detri- blocks to make part of the food pyramid collapse. tus? (Zooplankton.) Ask Do ? What can you do to prevent pollution from Ask the students with zooplankton blocks to con- entering the slough? (Tell others not to put struct the second level of the pyramid. pollutants down the storm drain; recycle motor oil, take Ask paints and pesticides to designated hazardous waste ? What animals will feed on the detritus, phy- centers.) toplankton and zooplankton in the slough? Do (Mud creatures (crabs, clams, mussels, snails, and worms), and fish ( gobies and smelt).) Put old plankton samples into the bucket to be returned to the slough at the end of the day. Do Ask the students with the mud creature and fish SLOUGH AND MUDFLAT FOOD PYRAMID blocks to construct the third level of the food pyramid, on top of the zooplankton. Ask Sand- ? What animals will feed on the mud creatures Egret and fish? (Birds. Shorebirds - such as piper dowitchers and sandpipers - and ducks feed on mud creatures, egrets and herons feed on fish and large mud creatures.) Mud Fish Creatures Do Ask the students with the bird blocks (duck, dowitcher, egret, and sandpiper) to complete the fourth level of the food pyramid. Ask Zooplankton Zooplankton ?Who is on the top of the pyramid? Why? (The Harrier. The hawk is the top predator.) ? Do you think plankton is important? (Plankton is a primary source of food for many animals. Without plankton, many Detritus Phytoplankton animals would starve. Field Trip Activities: Habitat Studies 205 PPPlalalanknknktttooon LaLan b DDb aaattta SSa hhheeteeteet
Your Name:______
Draw and identify any plankton that you discover.
Circle one: Phytoplankton or zooplankton
Name:______
Circle one: Phytoplankton or zooplankton
Name:______
Circle one: Phytoplankton or zooplankton
Name:______
206 Field Trip Activities: Habitat Studies