Ac vi es:

A. Beginning

1. Gree ngs

2. Administra ve business – roll call, etc. (performed internally)

3. Reflec on - “Nature is very consonant and conformable with herself.” - Isaac Newton

4. The teacher will begin class by discussing the iden fica on key assigned the previous day. The teacher will ask the students to project their key (those who made an electronic version of it) or show their work (those who made physical versions). They must explain their keys and the visible characteris cs of the seagrasses. By doing this, they will review the different seagrass species found in Puerto Rico. The teacher will take the opportunity to review the nonvisible characteris cs as well.

B. Development

1. A er the review, the teacher will explain to the students how seagrasses require certain condi ons for survival and will begin a focused list to explore what the students know about this topic. The teacher will hand out a sheet tled Condi ons necessary for seagrass development. The students must use the space provided to write down all the condi ons they think are necessary for seagrasses to grow.

2. When they finish their list, students should be given a chance to express their thoughts. The teacher should keep a master list of the student responses on the board. The list should include that, as most other plants, seagrasses need sunlight for photosynthesis. Using this as a link, the teacher will then move on to the next ac vity. This involves a laboratory ac vity highligh ng the importance of sunlight and clear waters for healthy seagrasses.

3. The teacher will divide the class into subgroups for the lab ac vity tled How does water clarity affect seagrass meadows? The teacher will hand out the instruc ons and the fact sheet so the students can begin their work. In this exercise, students will no ce how important it is to maintain clean waters in order to preserve this ecosystem. In the first part of the lab ac vity, the students will observe how a secchi disk works. Please visit the following website and project it for the students: h p://www.mainevolunteerlakemonitors. org/recer fy/disk.php. If the technology is unavailable, the teacher must explain the way the disk works. Another op on is to acquire a water quality tes ng kit or build a secchi disk in the classroom and conduct water turbidity tes ng in the classroom.

Note: A er the laboratory ac vity, the teacher can plan a fieldtrip (to take place on a different day) to a nearby beach to measure water turbidity, so the students can make their predic ons about whether or not seagrasses could grow there. Students should remember that there are other important parameters that affect development in a specific area. However, the exercise can be done focusing only on turbidity.

4. A er finishing the lab ac vity, each student or sub-group will explain their findings. At this me, the teacher should discuss the necessary condi ons for seagrass growth and development with the students.

Necessary condi ons for seagrass growth and healthy development:

• They need sunlight in order to photosynthesize.

• They should be submerged underwater. Most seagrasses tolerate a high range of water salinity. So, these plants can inhabit areas with low salinity (estuarine zones) or high salinity areas (hypersaline environments).

• Waters should be clear and shallow, allowing sunlight to reach the plants on the seafloor. If there is sediment discharge near the coast, turbidity increases, and sunlight penetra on becomes difficult.

• Generally, they need temperatures around 24 ºC (75oF). Some species can survive in temperatures between 4ºC and 24ºC (39oF – 75oF).

• Seagrasses need soil to anchor their roots into and from which to absorb nutrients.

• They need rela vely mild currents and surf condi ons. Seagrasses cannot survive in areas with strong surf or currents.

E. Closing

1. To conclude the class, the teacher will ask the students to check the focused list they made at the beginning of class and determine which student or studentes came closest to describing the ideal environment for seagrasses. This student can be rewarded with a small prize if the teacher wishes to do so. Students will also turn in their completed laboratory reports.

2. The teacher will address any remaining ques ons or doubts about the subject.

Homework:

1. Students will be asked to look up informa on about the rivers in Puerto Rico, both in the northern and the southern regions. The teacher will assign each student a different river so that they can exchange informa on in the following class during the group ac vity. Each student should look up two rivers, one with a large volume of water, and a smaller, less voluminous one. Students can use the internet, encyclopedias, books, and other sources.

Praxis reflec on:

The reflec on will be performed by the teacher at the end of class.

Reasonable accommoda on:

Reasonable accommoda on will be offered to all students who need it. Students with physical or cogni ve difficul es will be offered reasonable me in which to complete their tasks, tutoring during office hours and all the necessary opportuni es, according to their par cular cases.

Oceanic literacy: Essen al principles and fundamental concepts

Principle 5: “The ocean supports a great diversity of life and ecosystems.” e. The ocean provides a vast living space with diverse and unique ecosystems from the surface through the water column and down to, and below, the seafloor. Most of the living space on Earth is in the ocean. f. Ocean ecosystems are defined by environmental factors and the community of organisms living there. Ocean life is not evenly distributed through me or space due to differences in abio c factors such as oxygen, salinity, temperature, pH, light, nutrients, pressure, substrate, and circula on. A few regions of the ocean support the most abundant life on Earth, while most of the ocean does not support much life.

Content standards and grade expecta ons

Biological sciences

Standard: Interac ons and energy

Expecta ons and indicators:

From molecules to organisms: structures and processes

EI.B.CB1.IE.2 Evaluates how gene c and environmental factors influence organism development. Understands how scien sts use gene c knowledge to predict progeny.

Biology

Standard: Conserva on and change

Expecta ons and indicators:

Ecosystems: Interac ons, energy, and dynamics

ES.B.CB2.CC.1 Iden fies environmental factors to argue about their nega ve and posi ve effects on popula on growth.

Standard: Subject structure and organiza on levels

Expecta ons and indicators:

Ecosystems: Interac ons, energy, and dynamics

ES.B.CB2.EM.1 Uses mathema cal or technological representa ons to support their explana ons about the factors that affect ecosystems and their load capacity at different scales.

ES.B.CB2.EM.2 Uses mathema cal representa ons to support and revise science-based explana ons about the factors affec ng ecosystem biodiversity and popula ons at different scales.

Standard: Interac ons and energy

Expecta ons and indicators:

Ecosystems: Interac ons, energy, and dynamics

ES.B.CB2.IE.4 Evaluates the statements, evidence and reasoning about the complex interac ons ecosystems encompass maintain the amount and variety of organisms in a rela vely consistent manner across stable condi ons. But changes in condi ons can cause a new ecosystem.

Focused list

Name: _________________________Date: _____________________________ Teacher: _______________________Grade-Group: _______________________

Instructions: Write the words or phrases related to the NECESSARY CONDITIONS FO R SEA GRASS DEVELOPMENT . Then, discuss your answers with your teacherand the other students in your class.

University ofPuerto Rico MayagüezCampus Sea GrantProgram

Seagrasses

Laboratory data sheet: How does water clarity affect seagrass meadowsdistribution?

Name: __________________________Date: _____________________________

Teacher: _______________________Grade-Group: _______________________

Theme: Water clarity and its importance for seagrasses

Background:

Sunlight in oceans is essential for several species’ survival; for instance, seagrasses need solar energy in order to perform photosynthesis. Sunlight penetrates ocean water and while part of it is readily absorbed by organisms, some of this energy is reflected by the water and the particles suspended in the water column. The more particles suspended in the water, the less depththe sunlight’s energy can reach because of all the particles absorbing and reflecting the light. Therefore, sunlight reaches greater depthsin clear water than it does in high-turbidity water.

Water clarity is diminished by suspended particles, which can include sediments and live organisms like plankton. There are different ways to calculate a body of water’s clarity, but the simplest and most traditional method is through the use of an instrument called a SecchiDisc (Figure1).

Generally, the saltwater Secchi Disc measures between 40 to 60 cm in diameter, and the freshwater Secchi Disc measures 20 cm. These discs are divided in 4 quarters, with two white areas and two black areas. The disc is tied at the center of its face with arope calibrated in centimeters; that is to say, a rope with centimeter intervals marked along its length. The first mark is set at0 cm, where the line is secured to the disc. A weightis attached to the disc’s underside. A person submerges the Secchi disc in the water, letting out the rope until the disc is no longer visible. A note is made indicatingthe centimeters of line below the surfaceat that point. Then, the disc is raised slowly toward the surface until it is once again visible.The depth, in centimeters, are again noted.Lastly, calculate the average between these two values (the depths at which the discdisappeared, and where it came back into view) toobtain the Secchi disc depth (Sd).

Example:

First measurement(when disc disappears) = 646 cm

Second measurement(when disc reappears) = 639 cm

Average Sd = (646 cm + 639 cm)/2 = 642.5 cm; this is theSecchidisc’s depth.

To convert the Sd from centimeters to meters, do the following:

Obtained value= 642.5 cm

Conversion factor: 1 cm = 10-2 m

Conversion:

642.5 cm 10-2 m= 642.5 x 10-2 m = 6.425 m = 6.42 m 1 cm

Note: Scientific notation and rounding will be reviewed in this section.

When water clarityis greatly reduced in an area, the organisms living in the ocean bottom are affected because the amount of light they receive is reduced, which can limit photosynthesis and organism distribution. Seagrass meadowsare highly important ecosystems to humans, sincethey provide many products and services. Therefore, theirdegradationposes a loss not only to local ecology but also the economy.

With the Secchi disc measurements (in meters), you can calculate the maximum approximate depth at which photosynthetic organisms can live; that is to say, the depth at which enough sunlight reaches so as to permit photosynthetic processes Pf (depth to which photosynthesis can occur, or approximately 1% of lightpenetration. This is also called the euphotic zone.)Use the following mathematical formula:

Pf = Sd* 2.8

In this example, Pf = 6.42 m *2.8 = 17.98m

What this means is that, in this particular location, no photosynthetic processes can occur beyond a depth of 18 m, and therefore, no seagrasses can be found beyond that point.

Turbidity

Turbidity is a property expressing the degree to which the water is clear. It is measured in Nephelometric Turbidity Units (NTU), Jackson Turbidity Unit (JTU) or m-1. Researcherscan calculate the maximum depth for photosynthesis(Pd)to occur if they know the turbidity quotient (k) in a location using the following formula:

Pd= ln (0.01)/k

Where:

Pd= maximum photosynthesis depth k = turbidityquotient for a location

0.01 = the minimum percentage of solar light (1%) required for photosynthesis to occur

Before performing this laboratory activity, you can practice how to determine turbidity in a body of water. This can be done in several ways:

1.Visit the following website: http://www.mainevolunteerlakemonitors.org/recertify/disk.php. Read the instructions carefully and take the measurements.

2.In the classroom, you can compare two liquids of different turbidities. To do this, fill two clear containers with tap waterand add a bit of milk to one of them, making itturbid. Place the mini Secchi disc*under one of the containersand carefully observe from above. Compare your observations with the following turbidity guide:

Of the three mini discs shown here, choose the one most similar to what you observe and write the turbidity value indicated on the image (0, 40 or 100 JTU). This will be the turbidity reading for the sample. Repeat the process with the second container andcompare the two containers’ turbidity.

*Note: Remember you can obtain a Secchi disc with a water quality testing kit or you can make one yourself. You can also print and cut out the mini disc on this sheet andthe turbidity guide for practice in class.

3.Build a saltwater Secchi disc in the classroom. Visit the nearest beach in your community and use the disc to take several measurements at different points along the coast. Follow the instructions above to determine water turbidity using the Secchi disc. Write your measurements (m) in the table below:

When you finish practicing, you can complete the following laboratory on water clarity and the distribution of the seagrass meadows.

Laboratory activity: How does water turbidity affect seagrass meadow growth?

You already know about water clarity and turbidity, and how this is measured. Now you will use these concepts in a laboratory activity about turbidity and seagrass meadow growth. Follow the instructions below.

Hypothesis: Answer the following questions in complete sentences. Then, compose a hypothesis using your answers as a guide.

1. Will high turbidity (or loss of water clarity) positively or negatively affect seagrass meadow growth? Explain.

2. If the water has high turbidity, can seagrasses perform photosynthesis?

Hypothesis: ______________________________________________________________________________

Procedure:

For this activity, you will calculate the maximum depth at which you will be able to find seagrass meadows in La Parguera, Lajas. To do this, you will use water turbidity data (turbidity quotient k measured in m-1) measured at 10 different coastal locations (all with a 20 m depth). All the data used were collected from reliable sources.

Use the data provided in the table below. The first column shows the sample points, while the second column shows the turbidity quotient at each of these points. In the third column, you must write the maximum depth (m) at which photosynthesis can occur at each sample site. To find this depth, use the previously mentioned mathematical formula:

Pd = ln (0.01) / k

Pd = 4.6052 / k in which Pd is the maximum depth in which photosynthesis can occur, and k is the water turbidity quotient. Use the absolute (positive) value when writing your result (+).

To calculate the maximum depth, follow the steps below:

Pd = ln (0.01) / k

Pd = 4.6052 / k

Pd = 4.6052 / 0.10 m-1

Pd = 46.052 m = 46.1 m

You can also use the Excel program to calculate and graph your results on a computer. To learn how to do this, please check the instructions attached at the end of this laboratory activity.

Use the data you obtained to build a graph in the space provided below orbuild your graph using a spreadsheet program like Excel (see attachment). The Turbidity data belongs on the X axis, while the Maximum Depth data corresponds to the Y axis. All ten data points should be reflected on the graph. Remember to add a title, axis names, scale, and curve to your graph.

Graph interpretation: Carefully observe the graph obtained fromthe data, analyze the information,and interpret the data. Then, answer the following questions:

1.What happens to the maximum depth as water turbidity increases?

2.At how many points on the graph does enough sunlight reach the seafloor(at 20 m) to allow photosynthesis? At how many points on the graph does the bottom not receive enough light to allow photosynthesis?

3. List which sites can sustain seagrass meadows growth.

4. Suppose that water turbidity in this region is primarily related to coastal building expansion, do you believe that urban sprawl is negatively affecting seagrass growth in La Parguera? Explain your answer.

5. What is the maximum level of turbidity the seagrasses in La Parguera can tolerate in depths up to 20 m?

6. If the data gathering points were set at a depth of 10 m, how many would obtain the necessary sunlight conditions for seagrass growth?

7. If the data gathering points were set at a depth of 30 m, how many would obtain the necessary sunlight conditions for seagrass growth?

Conclusion: Write a paragraph in which you present and summarize the conclusions you reached after performing this laboratory activity. Remember to review and revise the answers you used to prepare your hypothesis at the beginning of the activity. Finally, write your recommendations for preserving this ecosystem and using it in a sustainable manner.