Aquariums – Miniature Oceans (part 2)

Photosynthesis, Respiration, and pH Goals Challenge students to link CO2 concentrations and pH values Challenge students to think of photosynthesis as a sink for CO2 and buffer against acidification Expose students to simple experiments that connect respiration and CO2 to increasing acid levels

Ocean Acidification Increasing CO2 leads to more carbonic acid (H2CO3) and pH of the ocean decreases Impacts organisms with calcium carbonate components Corals, Snails, some phytoplankton, etc… This is a problem as trends in CO2 production are increasing How could photosynthesis affect pH in a closed system like an aquarium? If photosynthesis uses CO2, CO2 should decrease and pH should increase (become more basic)

Activity 1 – Bromothymol Blue Assay Add 50mL water to a clear bottle Add ~20 drops of BTB or enough until solution becomes blue Using a straw, gently blow into the solution for 30 seconds. The solution will become yellow, indicating that the solution has become a weak acid. Do not inhale! Or drink the BTB solution

Activity 1 – Questions How does our breath turn water into a weak acid? Is respiration done only by animals? What other human activities produce CO2? Why are they so impactful? No, microbes and plants break down organic matter with oxygen producing CO2 (i.e. respiration) Burning fossil fuels and deforestation. These disrupt the balance between photosynthesis and respiration, leading to excess CO2

Activity 2 – Checking pH between light and dark aquariums Check pH using test strips between the light and dark aquariums Check pH using a pH probe Questions Is there a difference between the two tanks? Why? Is this difference large enough to make an impact on organisms or food webs?

Coral Dissections Goals Introduce students to microbial symbioses and corals Provide basic introduction on microscope use Encourage students to think about the importance of organism interactions and their roles in ecosystem health (e.g., why does bleaching occur?)

Coral – The great host Micro Zooxanthellae photosynthesis Bacteria Stained bacteria Photosynthetic zooxanthellae Micro Zooxanthellae photosynthesis Bacteria Antibacterials Gut microbiome Macro Invertebrates Fish Anemone fish will host them As will shrimp and crabs

Coral Polyp Anatomy

The coral we’ll be working with Discosoma Palythoa Large polyp No tentacles Soft coral (does not have a calcium skeleton) Common in the aquarium trade Highly diverse Small polyp Short thin tentacles Soft coral (does not have a calcium skeleton) Common in the aquarium trade Highly diverse

Activity – Coral Dissection Select 1 polyp of each specimen (Actinodiscus and Palythoa) Examine structure of each intact coral under the dissection scope Using a scalpel, carefully make an incision around the edge of the coral Identify zooxanthellae symbionts

Coral Dissection – follow up questions Are there any differences between zooxanthellae symbionts in the two species? Why is coral bleaching an indicator of reef health? Why is the symbiosis between the zooxanthellae and coral important?

Bioluminescence & Coral Fluorescence Goals Introduce students to the topic of bioluminescence and fluorescence Challenge students to critically think about biologically produced light in the oceans and its potential uses Link microbial symbioses and bioluminescence to living strategies

Bioluminescence What are some of the purposes of bioluminescence? Videos https://www.youtube.com/watch?v=9HXXQBz6Vv0 https://www.youtube.com/watch?v=oKjFVBVGad0 What are some of the purposes of bioluminescence? Are bacteria the only organisms that can bioluminesce? Do you think it would be more/less beneficial to bioluminesce yourself, or to host bioluminscent bacteria in a symbiotic relationship? Cost/benefits?

Fluorescence Corals fluoresce under certain light wavelengths This a relatively common phenomenon, although the benefit of coral fluorescence remains unclear What are some potential reasons why corals fluoresce?

Activity View a culture of Vibrio harveyi in the dark and discuss bioluminescence View coral under 460nm light to view fluorescence discuss fluorescence

Bioluminescence & Coral Fluorescence – Follow up questions Does bioluminescence begin immediately after the lights go out? Why or why not? How does bioluminescence differ between V. harveyi in liquid culture, versus on agar plates? Is all bioluminescence caused by symbionts? What are the possible benefits to producing your own light in the deep ocean? Compare benefits of deep bioluminescence to surface planktonic bioluminescence How can predators and prey utilize bioluminescence? Why would some corals reflect certain wavelengths of light to emit their own light? What could be some drawbacks?