Section 4: Intertidal Zones

Transcription

1 Marine Conservation Science and Policy Service learning Program At the border between land and ocean there exists a wondrous diversity of life that can only be viewed by land lubbers at certain times of the day, and at other times surrenders itself to the fish and the crabs. This favorite location of beach combers is, of course, the intertidal zone. Module 1: Ocean and Coastal Habitats Section 4: Intertidal Zones Sunshine State Standard SC.912.N.1.1, SC.912.N.1.4, SC.912.E.7.4, SC.912.L.14.3, SC.912.L.14.7, SC.912.L.14.8, SC.912.L.14.10, SC.912.L.15.2, SC.912.L Objectives Learn about the ecology in the intertidal zone Learn about climate change studies in the intertidal zone Learn about experimental design to understand different ecosystems Using a given research question design an experimental procedure Vocabulary Abiotic- the physical factors influencing an organism. Diversity- the richness and evenness of a group of species. Evenness- a measure of the similarity of the abundances of different species in a group or community.. 1

2 Eulittoral zone (also called the midlittoral or mediolittoral zone)- is the intertidal zone, also known as the foreshore. It extends from the spring high tide line, which is rarely inundated, to the neap low tide line, which is rarely not inundated. Littoral zone- refers to that part of a sea, lake or river that is close to the shore. Microclimate- is a local atmospheric zone where the climate differs from the surrounding area. Richness- the number of different species in a group or community. Species- a group of organisms that have the ability to interbreed Sessile- is that quality of an organism which rests unsupported directly on a base, either attached or unattached to a substrate. Sublittoral zone- also called the neritic zone starts immediately below the eulittoral zone. This zone is permanently covered with seawater. Supralittoral zone- (also called the splash, spray, or supratidal zone) is the area above the spring high tide line that is regularly splashed, but not submerged by ocean water. Tides- are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. Background The intertidal zone (also known as the foreshore and seashore and sometimes referred to as the littoral zone) is the area that is exposed to the air at low tide and underwater at high tide (for example, the area between tide marks). This area can include many different types of habitats, including steep rocky cliffs, sandy beaches, or wetlands (e.g., vast mudflats). The area can be a narrow strip, as in Pacific islands that have only a narrow tidal range, or can include many meters of shoreline where shallow beach slope interacts with high tidal excursion. 2

3 Organisms in the intertidal zone are adapted to an environment of harsh extremes. Water is available regularly with the tides but varies from fresh with rain to highly saline and dry salt with drying between tidal inundations. The action of waves can dislodge residents in the littoral zone. With the intertidal zone's high exposure to the sun the temperature range can be anything from very hot with full sun to near freezing in colder climates. Some microclimates in the littoral zone are ameliorated by local features and larger plants such as mangroves. Adaption in the littoral zone is for making use of nutrients supplied in high volume on a regular basis from the sea which is actively moved to the zone by tides. Edges of habitats, in this case land and sea, are themselves often significant ecologies, and the littoral zone is a prime example. 3

4 A typical rocky shore can be divided into a spray zone or splash zone (also known as the supratidal zone), which is above the spring high-tide line and is covered by water only during storms, and an intertidal zone, which lies between the high and low tidal extremes. Along most shores, the intertidal zone can be clearly separated into the following subzones: high tide zone, middle tide zone, and low tide zone. In the intertidal zone the most common organisms are small and most are relatively uncomplicated organisms. This is for a variety of reasons; firstly the supply of water which marine organisms require to survive is intermittent. Secondly, the wave action around the shore can wash away or dislodge poorly suited or adapted organisms. Thirdly, because of the intertidal zone's high exposure to the sun the temperature range can be extreme from very hot to near freezing in frigid climates (with cold seas). Lastly, the salinity is much higher in the intertidal zone because salt water trapped in rock pools evaporates leaving behind salt deposits. These four factors make the intertidal zone an extreme environment in which to live. A typical rocky shore can be divided into a spray zone (also known as the Supratidal Zone, which is above the spring high-tide line and is covered by water only during storms, and an intertidal zone, which lies between the high and low tidal extremes. Along most shores, the intertidal zone can be clearly separated into the following subzones: high tide zone, middle tide zone, and low tide zone. 4

5 Zonation Marine biologists and others divide the intertidal region into three zones (low, middle, and high), based on the overall average exposure of the zone. The low intertidal zone, which borders on the shallow subtidal zone, is only exposed to air at the lowest of low tides and is primarily marine in character. The mid intertidal zone is regularly exposed and submerged by average tides. The high intertidal zone is only covered by the highest of the high tides, and spends much of its time as terrestrial habitat. The high intertidal zone borders on the swash zone (the region above the highest still-tide level, but which receives wave splash). On shores exposed to heavy wave action, the intertidal zone will be influenced by waves, as the spray from breaking waves will extend the intertidal. High tide zone (upper mid-littoral) The high tide zone is flooded during high tide only, and is a highly saline environment. The abundancy of water is not high enough to sustain large amounts of vegetation, although some do survive in the high tide zone. The predominant organisms in this subregion are anemones, barnacles, brittle stars, chitons, crabs, green algae, isopods, limpets, mussels, sea stars, snails, whelks and some marine vegetation. The high tide zone can also contain rock pools inhabited by small fish and larger seaweeds. Another organism found here is the hermit crab, which because of its portable home in the form of a shell does extremely well as it is sheltered from the high temperature range to an extent and can also carry water with it in its shell. Consequently there is generally a higher population of hermit crabs to common crabs in the high tide zone. Life is much more abundant here than in the spray 5

6 Middle tide zone (lower mid-littoral) The middle tide zone is submerged and flooded for approximately equal periods of time per tide cycle. Consequently temperatures are less extreme due to shorter direct exposure to the sun, and therefore salinity is only marginally higher than ocean levels. However wave action is generally more extreme than the high tide and spray zones. The middle tide zone also has much higher population of marine vegetation, specifically seaweeds. Organisms are also more complex and often larger in size than those found in the high tide and splash zones. Organisms in this area include anemones, barnacles, chitons, crabs, green algae, isopods, limpets, mussels, sea lettuce, sea palms, sea stars, snails, sponges, and whelks. Again rock pools can also provide a habitat for small fish, shrimps, krill, sea urchins and zooplankton. Apart from being more populated, life in the middle tide zone is more diversified than the high tide and splash zones. Low tide zone (lower littoral) This subregion is mostly submerged - it is only exposed at the point of low tide and for a longer period of time during extremely low tides. This area is teeming with life; the most notable difference with this subregion to the other three is that there is much more marine vegetation, especially seaweeds. There is also a great biodiversity. Organisms in this zone generally are not well adapted to periods of dryness and temperature extremes. Some of the organisms in this area are abalone, anemones, brown seaweed, chitons, crabs, green algae, hydroids, isopods, limpets, mussels, nudibranchs, sculpin, sea cucumber, sea lettuce, sea palms, sea stars, sea urchins, shrimp, snails, sponges, surf grass, tube worms, and whelks. Creatures in this area can grow to larger sizes because there is more energy in the localized ecosystem and because marine vegetation can grow to much greater sizes than in the other three intertidal subregions due to the better water coverage: the water is shallow enough to allow plenty of light to reach the vegetation to allow substantial photosynthetic activity, and the salinity is at almost normal levels. This area is also protected from large predators such as large fish because of the wave action and the water still being relatively shallow. Tide Pools Each tide pool is a unique environment formed in rocky depressions by the receding tide. Tide pool organisms face large and sudden changes in salinity, temperature, ph and other factors due to tidal movements. As a result, residents have many special adaptations. Tide pools differ from each other depending on depth and height in the intertidal. Anemones, sea urchins, barnacles, dog whelks, and sculpins create intricate interactions in these tiny, isolated micro-habitats. 6

7 Other Definitions In oceanography and marine biology, the idea of the littoral zone is extended roughly to the edge of the continental shelf. Starting from the shoreline, the littoral zone begins at the spray region just above the high tide mark. From here, it moves to the intertidal region between the high and low water marks, and then out as far as the edge of the continental shelf. These three subregions are called, in order, the supralittoral zone, the eulittoral zone and the sublittoral zone. Supralittoral zone The supralittoral zone (also called the splash, spray, or supratidal zone) is the area above the spring high tide line that is regularly splashed, but not submerged by ocean water. Seawater penetrates these elevated areas only during storms with high tides. Organisms here must cope also with exposure to air, fresh water from rain, cold, heat and predation by land animals and seabirds. At the top of this area, patches of dark lichens can appear as crusts on rocks. Some types of periwinkles, Neritidae and detritus feeding Isopoda commonly inhabit the lower supralitoral. Eulittoral zone The eulittoral zone (also called the midlittoral or mediolittoral zone) is the intertidal zone, also known as the foreshore. It extends from the spring high tide line, which is rarely inundated, to the neap low tide line, which is rarely not inundated. The wave action and turbulence of recurring tides shapes and reforms cliffs, gaps, and caves, offering a huge range of habitats for sedentary organisms. Protected rocky shorelines usually show a narrow almost homogenous eulittoral strip, often marked by the presence of barnacles. 7

8 Exposed sites show a wider extension and are often divided into further zones. For more on this, see intertidal ecology. Sublittoral zone The sublittoral zone, also called the neritic zone, starts immediately below the eulittoral zone. This zone is permanently covered with seawater. In physical oceanography, the sublittoral zone refers to coastal regions with significant tidal flows and energy dissipation, including non-linear flows, internal waves, river outflows and oceanic fronts. In practice, this typically extends to the edge of the continental shelf, with depths around 200 metres. In marine biology, the sublittoral refers to the areas where sunlight reaches the ocean floor, that is, where the water is never so deep as to take it out of the photic zone. This results in high primary production and makes the sublittoral zone the location of the majority of sea life. As in physical oceanography, this zone typically extends to the edge of the continental shelf. The benthic zone in the sublittoral is much more stable than in the intertidal zone; temperature, water pressure, and the amount of sunlight remain fairly constant. Sublittoral corals do not have to deal with as much change as intertidal corals. Corals can live in both zones, but they are more common in the sublittoral zone. Within the sublittoral, marine biologists also identify the following: The infralittoral zone is the algal dominated zone to maybe five meters below the low water mark. The circalittoral zone is the region beyond the infralittoral, that is, below the algal zone and dominated by sessile animals such as oysters. Shallower region of the sublittoral zone, extending not far from the shore, are sometimes referred to as the subtidal zone. Intertidal Ecology Intertidal ecology is the study of intertidal ecosystems, where organisms live between the low and high tide lines. At low tide, the intertidal is exposed whereas at high tide, the intertidal is underwater. Intertidal ecologists therefore study the interactions between intertidal organisms and their environment, as well as between different species of intertidal organisms within a particular intertidal community. The most important environmental and species 8

9 interactions may vary based on the type of intertidal community being studied, the broadest of classifications being based on substrates rocky shore and soft bottom communities. Organisms living in this zone have a highly variable and often hostile environment, and have evolved various adaptations to cope with and even exploit these conditions. One easily visible feature of intertidal communities is vertical zonation, where the community is divided into distinct vertical bands of specific species going up the shore. Species ability to cope with abiotic factors associated with emersion stress, such as desiccation determines their upper limits, while biotic interactions e.g.competition with other species sets their lower limits. Intertidal regions are utilized by humans for food and recreation, but anthropogenic actions also have major impacts, with overexploitation, invasive species and climate change being among the problems faced by intertidal communities. In some places Marine Protected Areas have been established to protect these areas and aid in scientific research. Types of intertidal communities Intertidal habitats can be characterized as having either hard or soft bottoms substrates. Rocky intertidal communities occur on rocky shores, such as headlands, cobble beaches, or humanmade jetties. Their degree of exposure may be calculated using the Ballantine Scale. Soft-sediment habitats include sandy beaches, and intertidal wetlands (e.g., mudflats, and salt marshes). These habitats differ in levels of abiotic, or non-living, environmental factors. Rocky shores tend to have higher wave action, requiring adaptations allowing the inhabitants to cling tightly to the rocks. Soft-bottom habitats are generally protected from large waves but tend to have 9

10 more variable salinity levels. They also offer a third habitable dimension depth thus, many soft-sediment inhabitants are adapted for burrowing. Because intertidal organisms endure regular periods of immersion and emersion, they essentially live both underwater and on land and must be adapted to a large range of climatic conditions. The intensity of climate stressors varies with relative tide height because organisms living in areas with higher tide heights are emersed for longer periods than those living in areas with lower tide heights. This gradient of climate with tide height leads to patterns of intertidal zonation, with high intertidal species being more adapted to emersion stresses than low intertidal species. These adaptations may be behavioral (i.e. movements or actions), morphological (i.e. characteristics of external body structure), or physiological (i.e. internal functions of cells and organs). In addition, such adaptations generally cost the organism in terms of energy (e.g. to move or to grow certain structures), leading to trade-offs (i.e. spending more energy on deterring predators leaves less energy for other functions like reproduction). Intertidal organisms, especially those in the high intertidal, must cope with a large range of temperatures. While they are underwater, temperatures may only vary by a few degrees over the year. However, at low tide, temperatures may dip to below freezing or may become scaldingly hot, leading to a temperature range that may approach 30 C (86 F) during a period of a few hours. Many mobile organisms, such as snails and crabs, avoid temperature fluctuations by crawling around and searching for food at high tide and hiding in cool, moist refuges (crevices or burrows) at low tide. Besides simply living at lower tide heights, non-motile organisms may be more dependent on coping mechanisms. For example, high intertidal organisms have a stronger stress response, a physiological response of making proteins that help recovery from temperature stress just as the immune response aids in the recovery from infection. 10

11 Intertidal organisms are also especially prone to desiccation during periods of emersion. Again, mobile organisms avoid desiccation in the same way as they avoid extreme temperatures: by hunkering down in mild and moist refuges. Many intertidal organisms, including Littorina snails, prevent water loss by having waterproof outer surfaces, pulling completely into their shells, and sealing shut their shell opening. Limpets (Patella) do not use such a sealing plate but occupy a home-scar to which they seal the lower edge of their flattened conical shell using a grinding action. They return to this home-scar after each grazing excursion, typically just before emersion. On soft rocks, these scars are quite obvious. Still other organisms, such as the algae Ulva and Porphyra, are able to rehydrate and recover after periods of severe desiccation. The level of salinity can also be quite variable. Low salinities can be caused by rainwater or river inputs of freshwater. Estuarine species must be especially euryhaline, or able to tolerate a wide range of salinities. High salinities occur in locations with high evaporation rates, such as in salt marshes and high intertidal pools. Shading by plants, especially in the salt marsh, can slow evaporation and thus ameliorate salinity stress. In addition, salt marsh plants tolerate high salinities by several physiological mechanisms, including excreting salt through salt glands and preventing salt uptake into the roots. In addition to these exposure stresses (temperature, desiccation, and salinity), intertidal organisms experience strong mechanical stresses, especially in locations of high wave action. There are myriad ways in which the organisms prevent dislodgement due to waves. Morphologically, many mollusks (such as limpets and chitons) have low-profile, hydrodynamic shells. Types of substrate attachments include mussels tethering byssal threads and glues, sea 11

12 stars thousands of suctioning tube feet, and isopods hook-like appendages that help them hold onto intertidal kelps. Higher profile organisms, such as kelps, must also avoid breaking in high flow locations, and they do so with their strength and flexibility. Finally, organisms can also avoid high flow environments, such as by seeking out low flow microhabitats. Additional forms of mechanical stresses include ice and sand scour, as well as dislodgment by water-borne rocks, logs, etc. For each of these climate stresses, species exist that are adapted to and thrive in the most stressful of locations. For example, the tiny crustacean copepod Tigriopus thrives in very salty, high intertidal tide pools, and many filter feeders find more to eat in wavier and higher flow locations. Adapting to such challenging environments gives these species competitive edges in such locations. Food web structure During tidal immersion, the food supply to intertidal organisms is subsidized by materials carried in seawater, including photosynthesizing phytoplankton and consumer zooplankton. These plankton are eaten by numerous forms of filter feeders mussels, clams, barnacles, sea squirts, and polychaete worms which filter seawater in their search for planktonic food sources. The adjacent ocean is also a primary source of nutrients for autotrophs, photosynthesizing producers ranging in size from microscopic algae (e.g. benthic diatoms) to huge kelps and other seaweeds. These intertidal producers are eaten by herbivorous grazers, such as limpets that scrape rocks clean of their diatom layer and kelp crabs that creep along blades of the feather boa kelp Egregia eating the tiny leaf-shaped bladelets. Crabs are eaten by Goliath Grouper, which are then eaten by sharks. Higher up the food web, predatory consumers especially voracious starfish eat other grazers (e.g. snails) and filter feeders (e.g. mussels). Finally, scavengers, including crabs and sand fleas, eat dead organic material, including dead producers and consumers 12

13 Species interactions In addition to being shaped by aspects of climate, intertidal habitats especially intertidal zonation patterns are strongly influenced by species interactions, such as predation, competition, facilitation, and indirect interactions. Ultimately, these interactions feed into the food web structure, described above. Intertidal habitats have been a model system for many classic ecological studies, including those introduced below, because the resident communities are particularly amenable to experimentation. One dogma of intertidal ecology supported by such classic studies is that species lower tide height limits are set by species interactions whereas their upper limits are set by climate variables. Classic studies by Robert Paineestablished that when sea star predators are removed, mussel beds extend to lower tide heights, smothering resident seaweeds. Thus, mussels lower limits are set by sea star predation. Conversely, in the presence of sea stars, mussels lower limits occur at a tide height at which sea stars are unable to tolerate climate conditions. Competition, especially for space, is another dominant interaction structuring intertidal communities. Space competition is especially fierce in rocky intertidal habitats, where habitable space is limited compared to soft-sediment habitats in which threedimensional space is available. As seen with the previous sea star example, mussels are competitively dominant when they are not kept in check by sea star predation. Joseph Connell s research on two types of high intertidal barnacles, a Balanus and a Chthamalus species, showed that zonation patterns could also be set by competition between closely related organisms. In this example, Balanus outcompetes Chthamalus at lower tide heights but is unable to survive at higher tide heights. Thus, Balanus conforms to the intertidal ecology dogma introduced above: its lower tide height limit is set by a predatory snail and its higher tide height limit is set by climate. Similarly, Chthamalus, which occurs in a refuge from competition (similar to the temperature 13

14 refuges discussed above), has a lower tide height limit set by competition with Balanus and a higher tide height limit is set by climate. Although intertidal ecology has traditionally focused on these negative interactions (predation and competition), there is emerging evidence that positive interactions are also important. Facilitation refers to one organism helping another without harming itself. For example, salt marsh plant species of Juncus and Iva are unable to tolerate the high soil salinities when evaporation rates are high, thus they depend on neighboring plants to shade the sediment, slow evaporation, and help maintain tolerable salinity levels. In similar examples, many intertidal organisms provide physical structures that are used as refuges by other organisms. Mussels, although they are tough competitors with certain species, are also good facilitators as mussel beds provide a threedimensional habitat to species of snails, worms, and crustaceans. All of the examples given so far are of direct interactions: Species A eat Species B or Species B eats Species C. Also important are indirect interactions where, using the previous example, Species A eats so much of Species B that predation on Species C decreases and Species C increases in number. Thus, Species A indirectly benefits Species C. Pathways of indirect interactions can include all other forms of species interactions. To follow the sea star-mussel relationship, sea stars have an indirect negative effect on the diverse community that lives in the mussel bed because, by preying on mussels and decreasing mussel bed structure, those species that are facilitated by mussels are left homeless. Additional important species interactions include mutualism, which is seen in symbioses between sea anemones and their 14

15 internal symbiotic algae, and parasitism, which is prevalent but is only beginning to be appreciated for its effects on community structure. Current topics Humans are highly dependent on intertidal habitats for food and raw materials, and over 50% of humans live within 100 km of the coast. Therefore, intertidal habitats are greatly influenced by human impacts to both ocean and land habitats. Some of the conservation issues associated with intertidal habitats and at the head of the agendas of managers and intertidal ecologists are: 1. Climate change: Intertidal species are challenged by several of the effects of global climate change, including increased temperatures, sea level rise, and increased storminess. Ultimately, it has been predicted that the distributions and numbers of species will shift depending on their abilities to adapt (quickly!) to these new environmental conditions. Due to the global scale of this issue, scientists are mainly working to understand and predict possible changes to intertidal habitats. 15

16 2. Invasive species: Invasive species are especially prevalent in intertidal areas with high volumes of shipping traffic, such as large estuaries, because of the transport of non-native species in ballast water. San Francisco Bay, in which an invasive Spartina cordgrass from the east coast is currently transforming mudflat communities into Spartina meadows, is among the most invaded estuaries in the world. Conservation efforts are focused on trying to eradicate some species (like Spartina) in their non-native habitats as well as preventing further species introductions (e.g. by controlling methods of ballast water uptake and release). 3. Marine protected areas: Many intertidal areas are lightly to heavily exploited by humans for food gathering (e.g. clam digging in soft-sediment habitats and snail, mussel, and algal collecting in rocky intertidal habitats). In some locations, marine protected areas have been established where no collecting is permitted. The benefits of protected areas may spill over to positively impact adjacent unprotected areas. For example, a greater number of larger egg capsules of the edible snail Concholepus in protected vs. non-protected areas in Chile indicates that these protected areas may help replenish snail stocks in areas open to harvesting. The degree to which collecting is regulated by law differs with the species and habitat. 16

17 Activity: Intertidal Experimental Design Duration: 1 or several classes Materials Ocean News article: Notes from a Scientist: Dr. Chris Harley Simple explanation of experimental design Lined paper and pens for their materials and methods section Blank, unlined paper for drawings Pencils for drawing Creative juices flowing Optional Materials Building materials such as popsicle sticks glue pipe cleaners string construction paper aluminum foil scissors any other building equipment Background In this activity students will read about a scientist and his work examining how climate change will impact the intertidal zone. Given a research question and some general information students will then come up with an experimental design that will test variables related to climate change in the oceans. This activity is more about designing the experiment than getting results. Dr Chris Harley and his students at the University of British Columbia are some of the many who are working to understand how climate change will affect the marine world. They are interested in understanding more about how the impacts of climate change will affect intertidal organisms and ecosystems. This way we can do more to protect the areas that will be most negatively impacted by the abruptly changing environment due to global climate change. Their main areas of research are how changing temperature and ph levels in the oceans will affect the intertidal environment. As the sea surface temperatures of the oceans rise some organisms will thrive in the warmer waters, but many will be pushed beyond their thermal tolerances. Scientists have already observed an increase in water 17

18 temperatures with this trend predicted to continue. What Dr. Harley and his group are testing is how different organisms will respond to these temperature changes. Climate change is also having an impact on the ph of the oceans. Naturally the oceans absorb carbon dioxide from the atmosphere. As carbon dioxide has increased in the atmosphere over the last several centuries it has been estimated that the ocean has absorbed as much as a third of it. When carbon dioxide dissolves into the water it becomes carbonic acid. This increase in dissolved acid in the oceans is causing the ph of the water to decrease, becoming slightly acidic. It is this chemical change that could have major impacts on ocean life. In more acidic waters organisms have been shown to have lower survival and have lower reproductive success. Researchers are faced with the challenge of studying how these predicted changes in temperature and ph will affect marine organisms. Many experiments can be carried out in the lab under controlled conditions with the variables being altered very specifically. After initial observations are done in the laboratory the next step is to take the experiments to the intertidal zone and see if the results are consistent. To date Dr. Harley and his students have carried out numerous lab experiments that have examined how increasing temperatures and decreasing ph will affect intertidal organisms. They are now challenged with how to run similar experiments on the intertidal shore to expand their tests to the next level. The idea is to alter the temperature and ph of some of the individuals on the shore, while keeping all the other biotic (predators, competition) and abiotic factors (light, salinity) constant. Procedure 1. Together out loud as a class or individually have the students read the Ocean News article: Notes from a scientist: Dr. Chris Harley 2. Answer any questions about vocabulary or understanding about the article. 3. Have the students summarize what they understand about Dr. Harley's work on paper, either with drawings or writing. 4. Introduce or review the concept of experiments and the scientific method depending on your class. The main areas to cover are: hypothesis, materials and methods, results, discussion and conclusions. For a simple outline of these see the resource section. 5. Explain to the class their challenge is to come up with an experimental design that would allow Dr. Harley and his students to test how rising temperatures and decreasing ph will affect intertidal organisms that can be carried out on the shore. The challenge is to create some type of design that will create small zones on the rocky intertidal that will test temperature and ph separately, and in another area potentially be combined to test both temperature and ph. Go over the list of experimental constraints that the students will need to keep in mind as they design their experiments. Put this list on the board or overhead as the students work so they can keep them in mind. 18

19 6. Have the students move into small groups where they will review the challenge and begin to design their experimental design. It may be easiest to have them start with a list of what they will to change as variables, and then what are the items that they will need to control on the shore. 7. As the students are brainstorming circulate around and give suggestions and ideas if they are needed. Remind students to focus their ideas and efforts into creating the treatments rather than coming up with a hypothesis. 8. The students will prepare a methods and materials section that is written out and takes into consideration controls, variables, treatments, etc. Also have the groups draw out a plan of their experimental design to help explain it to others. 9. When the designs are complete have the small groups present their designs to another small group. This gives the students an opportunity to share their ideas, and hear other plans, without needing the large amount of time for the entire class to hear everyone's designs. 10. Depending on your goals for the activity have the students hand in their written plans for marking. 11. When the designs are complete ask the students what they found was the hardest part of designing the experiment, and what was the biggest challenge with working in the intertidal zone? Experimental Constraints Create small compartments in the intertidal area that are easily accessible for observing. Compartments must be open to organisms to move through such as seastars, crabs, and snails that are part of the natural ecosystem. Within each compartment you must be able to alter the temperature, either warmer or cooler. Within each compartment you must be able to increase the ph or decrease the ph slightly but not have it carried off to other areas. The experimental design can be set up over several different near by rocky beaches. The experimental set-up needs to be anchored so that it does not drift away at high tide, or moved to a different location for following low tide. In the different compartments you must be able to test temperature affects, ph affects and in one set of compartments both temperature and ph. Discussion What type of consideration does one need to make when designing an experiment? How is designing an experiment in the intertidal zone so challenging? Why do we what to re-test experiments in the real world and not just see the results in the lab? Why is having a step-by-step procedure important in science? 19

20 Extension and Resources A simple outline of Scientific Methods to help familiarize the students with experimental design You can have the students plan out experiments and have them build small models of their proposed set-up. Dr. Chris Harley's website 20

21 Notes from a Scientist: Dr. Chris Harley Climate change is a big field of study these days and many researchers are trying to understand what the future has in store with abrupt warming occurring. Dr. Chris Harley, a biologist at the University of British Columbia, is one of many scientists studying how organisms adapt to climate change in the oceans. His focus is on the small intertidal creatures that find themselves sometimes above the water and sometimes below the water, always at the mercy of the tides. When asked why he works in the rocky intertidal zone, Dr. Harley's immediate response is that: It's pretty, who wouldn't want to work there? Elaborating, he explains that the intertidal zone is a great place to work because of the animals. Dr. Harley appreciates that in the intertidal zone you don't have to wait for decades for an area to mature, like you would if you studied forests: off the west coast of British Columbia, barnacle patches can grow in just 6 months. He also points out that removing 100 barnacles on the shore for a study is easier on both the fingers and the conscience than removing a 100-year old tree. organisms to additional stress. Currently, Dr. Harley examines how intertidal animals and communities respond to increases in temperature and increases in carbon dioxide (CO 2 ). Both of these factors affect how organisms live in any environment and in the intertidal zone both are predicted to change greatly in the coming decades. As temperatures rise, the animals are pushed beyond their thermal limits. As CO 2 enters the water, the ph drops and the water becomes more acidic, subjecting the To shed light on this problem, one of Dr. Harley's graduate students is raising sea urchins in different water treatments to see how well the animals can form their shells in acidic conditions. This is done by bubbling CO 2 into the water in the lab. In the coming year they hope to test this on the shore at the Bamfield Marine Sciences Centre, but are still working out the details on how to run the experiment, without the tide carrying their research out to the sea. 21

22 Although scientists have discussed and argued the occurrence of global warming for several years, many say the time for debate is over. When I asked Dr. Harley how he deals with such attitudes he says: Those people are just misinformed or have their own agenda. Within the scientific community, the debate on whether it is happening or not is over. What all the causes are and the impacts will be, may still be discussed, but it is happening. He reminds us that many theories in the past were not fully accepted at first, but as more and more people learn the new science, the debate fades, just as it did when the idea of a round earth and the theory of plate tectonics were first proposed. If he didn't work along the rocky shoreline, Dr. Harley says there are a few other areas that he would have liked to try out. But at 6'8, he does not fit well into submersibles so deep sea adventures are not really an option, and he gets the chills quickly so scuba diving in the Antarctic ice water was also ruled out. Luckily for us we find him in the intertidal zone with barnacles, mussels, and other amazing living things. His projects will help us improve our understanding of the marine environment and our impacts on it. As Dr. Harley points out: the more we know, the better we can predict what will happen in the future, and protect those areas that need it most. As we finish up our discussion about climate change and marine science, Dr. Harley has two parting messages. The first is climate change is happening and that it is going to have huge ecological implications for the world. Despite this warning, Dr. Harley believes that everyone can participate in preventing this ecological disaster by doing small things everyday. His second message is that ecology, the study of how organisms interact with their environment, is fun. Studying how relationships in nature fit together can yield lots of information and the more we know the better we can make decisions regarding the future of our vital ecosystems. 22

23 Observations Simple Scientific Method Notes This is where you want to make some simple observations about the environment that you would like to study. You need to know what physical conditions are in the area, what the biotic and abiotic factors are, and what organisms are present. Scientists must first familiarize themselves with the environment that they wish to study. Research A little research about an area helps scientists understand what is already known about their potential research. This can be done using the library or by talking to other people who are familiar with the area. Research can help answer some basic questions and focus your experimental question. During discussion and research you can decided on what you would like to study and come up with a topic you wish to investigate. Hypothesis Once you have a question you want to make some predictions about what you expect to happen. Here you will form an If.then. because statement. It should read: If I do this or change this, then the organism's response will be this, because the organism does this, or needs to... Methods and Materials This is where you spend most of your time planning out the research. There are several things that must be taken into consideration in this section. Variables this is what you want to change in your experiment. Your variables are what you want to alter in order to answer your research question. If you want to know how temperature affects an organism than your variable in the experiment is temperature. Treatments the treatments are the different conditions that you will create in order to test your variables. You want to create a standard environment and then each treatment changes the one variable you are trying to test. For temperature you may have a cooler treatement, a normal range treatment, and a warmer than normal treatment you will place the organism in. Controls every experiment needs to have controls. These are the things that you do not change. These are the constants that you make sure stay the same so that any differences between your treatments can be attributed to your variables. Replicates for each treatment that you have to test your hypothesis you want to have several replicates in order to get an average answer. The goal is not to 23

24 find out what could happen in extremes but what is most likely to happen in the different treatments. Data collection this is important to think about before hand. What data do you want to collect and record in order to test your hypothesis? You also need to consider how to measure your results. Will you need a ruler, a stopwatch, a scale? Materials needed once you have a plan you want to create a materials list that will include all the equipment needed in order to carry out the experiment. Results Most results are recorded in a table of some form so that recording and later reading the results is easy. What is important in a results section is turning the data collected into a form that can be easy viewed and discussed. This usually involves making graphs, and computing averages. Bar graphs, line graphs and pictograms are all useful in displaying results. Discussion One of the most important parts of the discussion is to re-address the hypothesis statement. Either you gained evidence to support you hypothesis or not. Experiments do not prove ideas, they gain evidence for theories. A theory is only proved or becomes a scientific law when tried and tested by many people over many years. You also want to address any experimental errors that may have occurred due to equipment or human errors. State what the errors were and how you would correct them the next time. Discussions should also include what you would improve on for next time and what other questions came up during the procedure. Many experiments may collect evidence for one question but many more come up during the process. The discussion also needs to include some sort of explanation and discussion of the results. You need to explain and answer the question "So What?" Why are the results you found relevant and interesting? How does this relate to the organism and the environment in which it lives? Answering so what? can be difficult but it is this discussion that can be the most interesting in research. This discussion often also leads to many new questions and research ideas to further explore ideas. 24

25 Activity: CSI: Coastal Shore Investigation Duration: 2 classroom periods, 1 field trip day Objectives 1. Recognize the effect common physical and chemical factors have on rocky intertidal systems 2. Become familiar with commonly found organisms of rocky shore. 3. Recognize adaptations of intertidal organisms 4. Recognize vertical zonation in rocky shore communities. 5. Quantify species diversity and abundance. Materials Five gallon buckets-to carry equipment Clipboard, field notebook/paper worksheet 1, worksheet 2 1 meter quadrats, or hula hoops-quadrats can be made from PVC pipe or wood, recommend drilling holes in pipe/hula hoops to prevent flotation Field guides for each group Hydrometer or refractometer for testing salinity Celsius/Fahrenheit thermometer Chemical test kits or electronic probes to test water quality 100m tape measure, or marked nylon rope Tide chart-*plan well in advance for best tide-very important! Hand lenses Shallow plastic containers (Gladware) for short term observations of organisms Students should dress for the weather, layers work best and wear appropriate footwear, rubber boots preferred or old sneakers that can get wet 100mL grad. cylinder Background Ecologists have long observed the vertical zonation that creates intertidal habitats along the rocky shore. The distribution of organisms in particular zones is consistent with the influence of abiotic and biotic factors. This activity will require students to document the phenomenon of vertical zonation by setting up a transect line from high to low levels and comparing abundances of species along the transect. Because it is impossible to account for every organism in the intertidal, the transect will narrow the field of observation, creating a reference boundary. If a transect is semi-permanent, it can be used to conduct seasonal observations over time. The transect should be long enough and in an area that will properly characterize the ecosystem. Data shoud be collected on population density for approximately intertidal species. Properly identifying the organism is critical and students should be familiar with and equipped with field guides 25

26 and organism identifiers. The information will be used to discuss the abiotic and biotic factors that affect the distribution and species diversity of the intertidal zone. Field Trip-Transect Activity Preparation for field trip One class period: Students should be given an introduction to the activity which includes a demonstration/practice using the equipment, introduction to habitat, review of common organisms, ecosystem etiquette (see below); time to form groups and choose roles for each member; practice setting up transect in hallway or school yard; review map of the field trip area, save precious field time by pre-assigning groups to specific locations of study area. As a class decide on about species that everyone is fairly confident identifying, these are the ones that you will census. Not all organisms will be found in every zone. Don t forget the seaweeds! Field Trip Day Transect Set-Up 1. Survey the study site and choose an area that has distinct zonation. Lay out the 100m tape measure or marked rope beginning at the Spray zone and extending down to the Subtidal zone, secure each end using a rock or stake. Based on the length of the transect line you can lay your quadrats (1m or 0.5m squares) in a couple of ways: a. standardized: generally used for seasonal or yearly comparisons-divide transect length by 10, place quadrats at regular intervals b. random: accomplished in two methods-use a random number table to measure off in inches between quadrats, or throw a stone over your shoulder to determine where to begin the next quadrat. 2. Once quadrats are placed count the number of individuals per organism within the quadrat space. If the number is too large to count individually, for example over 100, note 100+ on data sheet. Encourage students to look closely and carefully. They can look under rocks, algae, and ledges as long as they are returned to their original position. Use data worksheet provided. 3. Continue down the transect line completing 10 quadrats. Be sure to work from both sides of the transect line. 4. Observations should be recorded relating to substrate (sand, rock, ledge, boulders), feeding behavior, associations with other organisms. Collecting Abiotic Data using data sheet provided Group members should describe and sketch the general landscape of the study site. A report of the weather conditions is also important. Prominent features such as steepness of slope, wave exposure, man-made elements and influences in the 26

27 immediate vicinity of study area, etc. Once the general landscape is accounted for, the immediate area of the transect should be sketched and described. At selected points, within the various zones, along the transect, sample the environmental conditions such as water temperature salinity, ph, dissolved oxygen, duration of exposure to air. These can be obtained using water from a tidepool in the immediate area of the transect. Estimate the amount of time (can be expressed as % of time) the area of a quadrat is submerged through a tidal cycle (low to high to low). Transect Tips and Hints Check your tide charts well in advance to pick the best tide for working the transect. Move from Spray to Subtidal if the tide is going out, work from Subtidal to Spray if tide is coming in. Once a procedure has been worked out, students should know to move as quickly as possible through the quadrats. You may be competing with an incoming tide. Consistency, consistency, consistency!! Reinforce with students that it is critical that they maintain a consistent procedure with each quadrat. This is important to all scientific observations that are repetitive, to prevent bias. Agree as a class before heading out how you will handle organisms that might be located half in and half out of the quadrat. Student groups should work together to complete the transect-half of the group sampling the abiotic factors; the other half working the quadrats. Consider having them switch roles if you are planning more than one transect for each group. Ecosystem Etiquette Students should be dressed appropriately for the conditions. They should NEVER work with their backs to the water in the lower intertidal, keeping waves in view. All organisms should be returned to the location where they were found. All disturbed rock, seaweed or other substrate should be returned to its original position. Animals should be treated with respect and care. Carry in, carry out and make every effort to leave no trace! Data Analysis Each group will need to note on their data sheet which quadrats were in each of the four intertidal zones of their transect, for example Quadrat 1 and 2 were in Spray zone. All of the data from the quadrats in that zone will be added together and averaged by the number of quadrats. If more than one transect was completed, all the better, pool all of the data or have the entire class pool data to make more accurate statements about the diversity of the area. There are many methods for visualizing the data. Have the students create graphs and charts to illustrate their observations and records. 27