Why Study Marine Microbes?

What do viruses, bacteria, archaea, phytoplankton, and protozoans all have in common? They are all single-celled and microscopic, belonging to a group of organisms known as marine microbes. Referred to as the “unseen majority” (Whitman et al. 1998) because of their microscopic size, marine microbes make up the largest contingency of living material or biomass in the ocean (Hatton et al. 2021). It is estimated that in the entire ocean, there are 10²⁹ bacteria and archaea – that’s 100,000x more than the number of stars in the visible universe (Bar-On et al. 2018; Harvey & Howell 2022; Whitman et al. 1998).

Marine microbes are incredibly important to food webs and biogeochemical cycling. For instance, primary producers like phytoplankton are the base of the food web, converting sunlight energy into sugars (glucose) that is transferred to higher trophic levels via predation. Furthermore, bacteria and archaea are critical to biogeochemical cycling in the ocean by functioning as decomposers to recycle organic matter like nitrogen and phosphorus back into bioavailable nutrients (NOAA a).

Many microbes are also critical to controlling the Earth’s climate and greenhouse gasses. Both photosynthesis and respiration by microorganisms impacts the concentration of oceanic and atmospheric oxygen and carbon dioxide concentrations (NOAA Ocean Exploration). For instance, primary producers like phytoplankton photosynthesize, absorbing carbon dioxide (CO₂) and converting it to breathable oxygen (O₂). Meanwhile, heterotrophic marine bacteria respire, taking in dissolved oxygen (DO) from seawater and converting it back to CO₂ via respiration. These two processes work synchronously: the photosynthetic organisms produce O₂ for organisms that respire, and the organisms that respire release CO₂ that can be used again by the photosynthetic organisms (Figure 1). However, these two processes are not always balanced.

Some regions of the ocean have low levels of oxygen and are considered oxygen deficient or hypoxic (<2 mg O₂/L). This lack of oxygen is problematic for animals and other heterotrophic, aerobic organisms that require adequate DO to respire (NOAA National Ocean Service). In some coastal regions, oxygen concentrations are low at depth due to nutrient pollution (USGS 2017). This overabundance of nutrients fuels phytoplankton growth. When these algal blooms terminate and sink, they are decomposed by marine bacteria. This decomposition process consumes oxygen at a high rate, leaving waters hypoxic if they cannot be adequately ventilated with the atmosphere or other DO-rich waters. When DO concentrations are so low such that they can no longer sustain animal life, they are considered “dead zones” (NOAA National Ocean Service). In these severely hypoxic regions, massive die-offs of fish can occur, consequently harming fisheries (NOAA b). Furthermore, coastal hypoxia is expanding with climate change, especially in the Southern California Bight and the Gulf of Mexico (Booth et al. 2014; Turner & Rabalais 2022). Research on hypoxia in coastal California is ongoing, and new information about what environmental and biological factors are contributing to expanding hypoxia is becoming available. Therefore, education of the general public on up-to-date hypoxia-related research is important as it impacts the communities in which they live.

To increase ocean literacy with regard to hypoxia and marine microbes, academic researchers, with expertise in marine microbes and coastal hypoxia, partnered with the USC Joint Educational Project’s (JEP) STEM Education Programs to develop curricula and host a professional development workshop for both formal and informal educators. Relevant research was translated into four lesson plans that are suitable for use in high school classrooms teaching environmental and marine science, biology, and chemistry. Lesson plans were aligned to Next Generation Science Standard (NGSS), California Common Core Standards, A Framework for K-12 Science Education, and Ocean Literacy Principles Scope and Sequence (NGSS 2017, California Department of Education 2013, National Academies 2012, NMEA a). The three-day workshop included an in-depth laboratory tour, a run-through of each of the four lessons, and a one-day excursion to the USC Wrigley Institute of Environmental Studies (WIES) on Catalina Island in the California Bight.

The objective of this workshop was to increase educator knowledge and confidence in teaching ocean sciences to high school students at Title I schools. Title I schools were our target audience to help increase access of disadvantaged students to hands-on science education that meets state academic content and performance standards. We aimed to increase ocean literacy in a larger population of students by equipping educators with the knowledge and resources to continue teaching our lessons year after year. Increasing ocean literacy helps students make educated decisions about the marine environment and its resources (NOAA c). The topics covered in these lessons are important and relevant, as climate change effects like deoxygenation can impact people from the communities in which our students and their families live. For instance, expanding hypoxic zones can be harmful to fisheries that people depend on for food or employment (Howard et al. 2020). Knowing how microbes influence these biological, chemical, and physical oceanographic processes is a key component of ocean literacy (NMEA b). Therefore, our lesson plans aim to increase ocean literacy and student awareness of pertinent issues facing their communities.

Alignment to Educational Standards

To make our lesson plans broadly available to California high schools, we aligned our lesson plans to NGSS and California Common Core Standards (NGSS, California Department of Education). We also aligned them to A Framework for K-12 Science Education standards and Ocean Literacy Principles Scope and Sequence to make these lesson plans applicable to educational standards in other states (National Academies, 2012; NMEA a). The NGSS standards covering biodiversity and populations in ecosystems and changing environmental conditions relate to our lessons about microbial diversity and climate change, while the standards covering geoscience relate to our lessons about the effects of physical and chemical oceanography on dissolved oxygen and nutrient concentrations. California Common Core Standards about carrying out experimental procedures and understanding science-specific words relate to performing the experiments in our lesson plans and analyzing the results, as well as comprehending the scientific content and vocabulary presented. A Framework for K-12 Science Education standards covering cycles of matter, cellular energy generating processes, adaptation, and climate change related to our lessons’ discussion of the role of microbes in biogeochemical cycling, energy generation via photosynthesis, phytoplankton adaptations to life in the surface ocean (e.g., the great plankton race), and consequences of global change. Lastly, Ocean Literacy Principles covering ocean circulation, biogeochemical cycling, climate change, oxygen production, primary productivity, and ecosystem and biological diversity relate to our lessons about the role of phytoplankton and bacteria in ocean biogeochemistry and DO content.

Survey results

Educators had a strong baseline understanding of microbial ecology before the workshop. When asked to define “marine microbe” and “ecology”, average scores increased minimally or did not change between the pre- and post-workshop knowledge assessments. On the pre-test, several teachers listed specific examples of microbes, including zooxanthellae and dinoflagellates, rather than a broader term such as “phytoplankton”. However, on the post test, a few educators were unsure if viruses were considered marine microbes. We did not cover viruses in our lesson plans, but this topic should be incorporated in the future to enhance comprehension of microbial ecology.

In contrast, educators had less background knowledge about chemical oceanography and dissolved oxygen (DO). When asked questions about DO on the pre-test, some teachers had a strong understanding of what DO is and why organisms need it, but some misconceptions were also present. Furthermore, teachers were only able to list a few examples of what impacts DO concentrations on the pre-test. After the workshop, the average score on this question increased from 2.57 to 4.57, indicating that our workshop helped educators better understand marine DO dynamics. When asked “what impacts the amounts of DO in the ocean,” some answers were high level (e.g., relating marine DO concentrations to upwelling and currents). This indicates that our workshop successfully increased educator’s knowledge of physical and chemical oceanography as it relates to DO.

The pre-lesson survey showed that educators thought it was important for students to learn about oceanography, with 100% answering “very important” or “somewhat important” (Figure 9A). Also, 85.7% of teachers thought most of their students were “not knowledgeable” or “somewhat not knowledgeable” about oceanography (Figure 9B). However, teachers did not feel as strongly that their students were interested in oceanography, with 50% answering “neutral” interest, 33.3% answering “somewhat interested”, and only 16.7% answering “very interested” (Figure 9C). Despite this lack of interest, we hope that our hands-on lesson plans will better engage students as hands on activities have been shown to increase student interest in the subject of study (Paris et al. 1998; Holstermann et al. 2009). We also made these lesson plans more relevant by putting them in the context of values that might be important to the students and how they interact with these concepts in their everyday lives. Together, this strategy should increase student interest and engagement. We did not follow up with educators to survey their students, but this should be incorporated to future workshops.

Regardless of student feelings about oceanography, it is clear that teachers believed that our educational framework could increase interest in STEM fields. One teacher wrote the following on their post-workshop survey: “It’s a great experience and reassures the importance of studying marine biology”. Though the pre-lesson survey questions regarding student interest were not asked again after the workshop, this indicates that the workshop may have further supported teachers’ positive feelings about the importance of marine science education.

The post-workshop survey on day three also asked teachers to rate workshop effectiveness. 85.7% strongly believed that the workshop increased their science knowledge. Additionally, 100% of educators strongly agreed that the workshop and the materials they received (supply kits and lesson plans) were useful to them. Overall, the teachers expressed that the workshop was a valuable experience and would recommend it to colleagues.

Reflections

Throughout the workshop, teachers were very engaged and asked lots of questions. Most of the questions were directed at gaining a deeper understanding of the subject material beyond what we planned on presenting, while others were based on previous knowledge of climate change to learn more about marine microbes in that context. For example, one teacher asked if phytoplankton, producers of oxygen, would be affected by expanding hypoxia. During the hands-on activities, they thought like students, preparing themselves to answer questions their students might ask. Similarly, during our presentation some of the ongoing research at USC, educators asked thoughtful questions to gain a deeper understanding of these topics. It was clear that educators had a strong interest in oceanography, hypoxia, and marine microbes.

Experiences interacting with academic researchers at WIES and USC were particularly memorable for educators. Several teachers wrote about how much they enjoyed the opportunity to observe academic scientists conducting research, saying that they really appreciated “…being able to talk to visiting researchers” and that “interacting with researchers was an added bonus!”. Others wrote about the experience of learning what a “real lab” and scientific equipment looks like. Often, there is a disconnect between research findings and how scientists come to these conclusions; the process of research can seem arcane. One goal of the workshop was to demystify the research process by bringing educators into labs actively conducting experiments. The opportunity to see flow cytometry measurements of cells in the lab and observe foraminifera research at WIES was highly valued by teachers. Furthermore, the immersive experience of making optode measurements allowed educators to participate in real time data collection using scientific equipment. One teacher remarked: “I enjoyed how interactive the workshop was…”.

While teachers participated in the scientific process, we discussed how it could be incorporated into the lesson plans. For instance, we drew connections between the optode measurements performed at WIES to the DO measurements made using a kit in Lesson 4. Bridging these two activities via the scientific concepts behind them demonstrates how real research techniques can be brought into classrooms to teach students how scientists make measurements and collect data.

Teachers valued witnessing real-time research being conducted on microbial organisms and felt that their students would value these experiences too. During the workshop, one teacher invited us to come speak in her classroom and asked if her students could visit USC for a lab tour. Another followed up after the workshop. She expressed that this experience would be highly valuable: “having [high school] students see college students doing their part in various research will no doubt increase their decision to attend college or pursue more science!”. It is clear that lab experiences like these, especially paired with field trips to universities, enhance both teacher and student engagement in science.

Educators thought the lessons were very engaging and fun stratification. They were amazed that the waters did not mix and the colors did not blend. Another teacher applauded the glitter “phytoplankton” in Lesson 1, saying “glitter will make any activity exciting and engaging”. However, some teachers did suggest substituting plastic glitter for an eco-friendly material or biodegradable glitter. Not only do these colorful tools increase enthusiasm for the subjects being taught, but also serve as great visual aids. For instance, in Lesson 2 a serial dilution of bacteria cannot be seen with the naked eye, yet the demonstration of serial dilutions with dyed water was a visual aid for this concept. Therefore, these visual tools may not only increase engagement, but also lead to a better understanding of the concepts presented.

Teachers also had excellent suggestions for incorporating the scientific method students are taught. When measuring DO of hot, cold, salty, and freshwater samples in Lesson 4, the results were not as expected. Teachers seized this opportunity to discuss errors in scientific research. They told us that students often struggle with this concept when writing lab reports but discussing it in this context might strengthen student comprehension.

Working through the lessons, educators also had suggestions for incorporating math standards. For example, in the great plankton race activity (Lesson 1) teachers suggested their students could calculate the surface area of their plankton after measuring sinking speed. By collecting this data from the whole class, students could make inferences about the relationship between surface area and sinking speed. Similarly, teachers suggested that students could calculate the volume of water filtered through a plankton net using the net’s diameter and length of tow. Therefore, quantitative science can demonstrate real world applications of math.

Estimated impact

Across the eight educators, these lessons are expected to reach at least 730 students in high school classrooms and over 850 in an informal education setting. These lesson plans are also publicly available (see Reproducibility). By sharing them online, we hope to expand ocean literacy and teach even more teachers and students about marine microbiology and hypoxia. Furthermore, most of the lessons require simple “grocery store” supplies, making them easy for teachers to reproduce in their own classrooms.