Lesson Title: Why swim, float, or stick? ​ Unit: Living Breakwaters (LB) Curriculum: Restoration and Resilience in Raritan Bay ​ Sub-Unit: LB Habitats Series: what’s the best habitat? ​ LESSON OVERVIEW Grade: 6-8 Class Periods: 1-2 Setting: classroom Subject Area(s): science Lesson Summary Students simulate the positions in the water column -- and the associated motility/sessility strategies -- of a variety of Living Breakwaters critters at different stages in their life cycles. Then students observe patterns in these positions and strategies, and draw inferences about the relationship between life stage, position in the water column, and motility/sessility strategy. Objective(s) ● Envision estuarine habitats in three dimensions. ● Categorize water column positions (benthic/pelagic) and motility/sessility strategies (nekton, plankton, sessile) ● Draw inferences about the relationships between pelagic/benthic positions in the water column and swimming/planktonic/sessile life stages. MATERIALS & RESOURCES Supplies ● String (depending on how many students you have you may need a couple hundred yards and it’s always good to have extra) ● Scissors ● Basic classroom supplies like markers and paper ● Optional: a bucket or fish tank full of water, and some items that can float in the water. You might use this to demonstrate how water currents push and pull planktonic organisms in different directions Handouts ● Observations / Inferences / Questions about underwater habitat ● Inhabitants of Raritan Bay Cards - this card set includes the life cycle cards (teal background) ​ for the following critters. For this lesson you’ll want to use at least one or two from each of the following categories. a. Pretty much floating wherever the currents take them (planktonic) i. Oyster embryo inside egg ii. Oyster free-swimming larva iii. Striped bass yolk-sac larva iv. Striped bass feeding larva v. Feather blenny yolk-sac larva vi. Feather blenny feeding larva vii. Eelgrass mature seed b. Pretty much stuck in one place (sessile) i. Oyster juvenile spat ii. Feather blenny embryo inside egg iii. Eelgrass embryo iv. Eelgrass seedling c. Movers, in or near the bottom all the time, or nearly all the time - some of these prefer hard structure but can live in or over soft bottom. They have different ways of moving around. (Motile benthic and epibenthic) i. Oyster settler larva ii. Blue crab juvenile d. Swimmers, always near a hard structure (pelagic, structure-oriented) i. Striped bass juvenile ii. Eel elver settler juvenile iii. Feather blenny juvenile e. Swimmers who live in open water, so if you see them at LB, they’re stopping by i. Eel glass juvenile ii. Eel silver adult f. Hardest to categorize i. Blue crab megalops larva - hard to categorize because it represents the blue crab’s transition from pelagic to benthic lifestyle ● The Inhabitants of Raritan Bay Cards set also includes the juv-adult species cards (white ​ ​ background) for the following critters. Depending on the number of students you have, choose additional cards from among the following taxa, which might be observed at the Living Breakwaters site. Between these and the previous list, be sure you have all the categories represented: a. Pretty much floating wherever the currents take them (planktonic) i. Diatoms ii. Dinoflagellates iii. Calanoid copepod iv. Lion’s mane jellyfish b. Pretty much stuck in one place (sessile) i. Eastern oyster (adult) ii. Blue mussel iii. Barnacle iv. Eelgrass (adult) v. Sea lettuce vi. Bladder wrack vii. Tubular hydroid viii. Ghost anemone - probably the least sessile, the ghost anemone does crawl along its surface. It’s in this group because, like all the other animals in this group, its feeding strategy depends on being stuck to a hard surface. c. Movers, in or near the bottom all the time, or nearly all the time - some of these prefer hard structure but can live in or over soft bottom. They have different ways of moving around. (Motile benthic and epibenthic) i. Hard clam ii. Blue crab (adult) iii. Summer flounder iv. Winter flounder v. American sand lance vi. Gammarid amphipod - some types (some tube-building amphipods are more sessile and require hard structure) vii. Caprellid amphipod viii. Bristle worms - some types (some tube-building bristleworms are more sessile and require hard structure) ix. Shore shrimp, grass shrimp x. Oyster drill d. Swimmers, always near a hard structure (pelagic, structure-oriented) i. Cunner ii. Naked goby iii. Feather blenny (adult) iv. Oyster toadfish e. Swimmers who live in open water, so if you see them at LB, they’re stopping by (pelagic, and feed on some or all of the above) i. Atlantic menhaden ii. Atlantic silversides - arguably silversides could go in the ‘movers in or near the bottom’ category: when they’re onshore, in the warmer months, that’s a good description of their habitat. But in winter they migrate far offshore. They are also schooling fish, which is a pelagic defense strategy. Many of these open water swimmers also school, and none of the other motile benthic animals school. iii. Bay anchovy iv. Atlantic striped bass (adult) v. Bluefish Lesson Materials ● Aquarium sounds - from Youtube, but you only need the audio ​ ● photo of a gap between rocks in Raritan Bay Vocabulary ● Plankton, planktonic - plankton are organisms that float where the water carries them. Many ​ don’t swim at all. Some do swim, but for the most part they can’t swim well enough to resist the water currents. That is especially common in fish larvae, who can propel themselves forward in still water, but don’t live in still water. ● Benthos, benthic - benthos are organisms that live near, on, or in the bottom sediments or ​ surfaces. Benthic organisms spend most or all of their time at the bottom of the water column. ● Water column - an imaginary vertical tube of water that reaches from the bottom to the ​ surface. People talk about the water column when they want to say something about a vertical ​ location within the water: at the bottom, at the surface, or somewhere in between. Picturing an ​ imaginary vertical column of water helps some people remember that the water is a three-dimensional environment. ● Pelagic - swimming. Pelagic organisms swim effectively, usually in pretty open water. ​ ● Open water - just water, where there are not a lot of other things in the way (such as rocks, ​ the shore, oyster reefs, or eelgrass beds) ● Structure-oriented - Fish that are structure-oriented do best when they can live near a ​ complex hard structure, such as an oyster reef. They find shelter (and often food) in the nooks and crannies of a complex underwater structure. If you wanted to build an intricate, three-dimensional structure, you’d probably do that with blocks rather than mud. In the same way, underwater structures are generally composed of hard surfaces, like rocks and shells. But one big exception is eelgrass meadows. A leaf of eelgrass is certainly not hard like a rock or a shell. And yet eelgrass somehow provides complex three-dimensional habitat for many other species -- although not necessarily the exact same set of critters that would inhabit an oyster reef or a rock structure like one of the breakwaters. Maybe you have an idea how eelgrass can be soft and still create three-dimensional structure? One thing is for sure: this neat trick of eelgrass only works in the water. If you saw eelgrass out of the water (where it would be dying, because it needs to stay rooted underwater -- so don’t actually take eelgrass out of the water! But if you did...), it would look pretty floppy. ● Sessile - stuck in one place, not moving. Sessile organisms actually do move, at least at ​ ​ ​ some point during their life cycle. People call an organism sessile if it has to be stuck to ​ ​ something at some point in its life cycle. ​ ​ For example, oysters have to be stuck to something as juveniles and adults, so they can go after oxygen and food. Detached juvenile and adult oysters are likely to end up buried in sediment, where they would quickly suffocate. Furthermore, even when sessile animals are stuck in one place, they don’t just wait for oxygen and food to come their way. From their sessile position, sessile animals move parts of their ​ ​ bodies. Rather than move their bodies through the water, sessile animals generally bring the water to or through their bodies. For example, oysters feed and get oxygen by creating a strong water current. They move tiny inside parts of their bodies very quickly and with incredible coordination to produce that water current through their shells. They create that flow of water to pull oxygen and food particles toward them, and to push their waste away from them. And finally, it’s rare to find a healthy sessile organism in still water. Sessile organisms do well in places where the water is moving enough to bring food and oxygen in their direction and carry waste away from them. But the water also can’t be moving too fast, because sessile organisms need to stay stuck to their surface, and not be washed away by the currents. So it’s also rare to find sessile organisms in places with very strong currents. In that way, sessile organisms are like Goldilocks: the water needs to move around them not too fast, and not too slow, but just the right amount. A lot of living things are like Goldilocks. BEFORE YOU GET STARTED Preparation ● Cards should be printed with the photograph on one side of the card and the information on the other side of the card. ● All cards should be laminated, hole punched and strung, so they hang around a student’s neck. This allows the students to be hands-free during the activity.