Crustose Coralline Algae: Photosynthetic Processes and Calcification in the Face of Climate Change
Photosynthesis uses water, carbon dioxide and sunlight to produce energy and oxygen. Oxygen is produced as a bi-product of photosynthesis and oxygen is used by the majority of other lifeforms for cellular respiration (Martin, 2013). Photosynthesis removes carbon dioxide from the environment and is one the main players in the global carbon cycle. Photosynthesis is light energy converted into chemical energy which is then stored in the form of glucose (C6H1206). Photosynthetic organisms such as CCA use carbon to generate organic molecules carbohydrate, lipids, and proteins in order to build biological mass. This experiment measured the oxygen rates to create the PI curve, the daily cycle of fluorescence, rapid light curves, and the photosynthetic rates and light levels in the field.
This study looked at two species of crustose coralline algae: Porolithin sp. and Sporolithin sp. The light meter was used to measure the average light intensities in the field in comparison to the light measurements in the laboratory. The Pre-Sens was used during the four light incubations in order to create a photosynthesis-irradiance curve (PI) for both species by measuring the oxygen concentration in the water. Finally, the PAM was used to create Rapid Light Curves to find the photosynthetic efficiency and photosynthetic maximum. Additionally, the PAM was used in the field to measure the organism’s instantaneous response to light throughout the day in the field. All of these methods provided a distinctive way to look into CCA’s photochemistry.
By looking at the photosynthetic parameters of different CCA taxa, this experiment was intended to assess the health of the organism. This data suggests that CCA make a larger contribution to organic production on coral reefs than originally predicted (Chisholm, 2003). The rate in which crustose coralline algae calcifies is directly correlated to their rate of photosynthesis. This calcification process creates a protective layer to bind the substrate and provide a barrier to erosion (Chisholm, 2003).
The main factors which effect underwater photosynthesis are depth, suspended particles, and temperatures. In the bottom of the euphotic (sunlit) zone, only blue light can penetrate through the surface. Blue light is high in energy and is strongly absorbed by chlorophyll (source). Darker species typically found in the depth are light-sensitive and will photo inhibit at a faster rate than the shallower species. Suspended particles and the overall turbidity of the water affects the amount of light that can reach into the water. As there is less light, there is less photosynthetic production.
Between Palfrey and South Island at Lizard Island National Park, we collected the samples of Porolithin sp. and Sporolithin sp. The light measurement on the surface of the water was 1300μmol/m2 and 962μmol/m2 on the surface of the reef. The Sporolithin sp. was collected at 293 μmol/m2, 337 μmol/m2, and 253 μmol/m2. The Porolithin sp. was collected at 747 μmol/m2, 782 μmol/m2, and 791 μmol/m2. The Porolithin sp. was found between 2.0-2.4 meters deep at high tide. The Sporolithin sp. was found between 2.6-2.8 meters deep at high tide. Sporolithin was found in a higher light environment than Sporolithin is normally found which is typically 10 around 6-12 meters.