Week 10 – Journal of Learning.
Carbon cycling in Coastal Environments.
How does the primary productivity, per unit area, of coastal primary producers compare to that of marine primary producers. Why, then, do you think oceanic primary productivity is greater overall? Write about this in your blog.
Coastal primary producers 10% of all marine production
Marine primary producers 90% of all marine production.
This is surprising as there is a larger number of organisms that enable primary productivity within coastal regions i.e. mangroves, coral reef algae, seagrasses etc. Whereas in the marine environment the main primary producers are phytoplankton and on occasion floating seaweed debris.
I believe oceanic primary production is generally much higher than coastal primary production due to the overall size of the ocean in comparison to that of coastal regions. The area of the ocean is much larger than the area of coastal regions. This means that there although there are fewer types of primary production in the ocean in comparison to the coast, there is a much higher volume of that particular primary producer (phytoplankton) due to the availability of area.
Explain where marine primary production is greatest, and why this is the case.
Marine primary production is greatest in coastal regions. This is due to a range of factors including temperature, currents, light and water movements (upwelling & down welling).
Upwelling is the process of a movement of water being forced upwards towards the surface. This water is pushed up from the colder deeper water and contains an abundance of nutrients. These nutrients are what stimulates the phytoplankton.
Upwelling do not happen everywhere (less than 1% of the world’s oceans) however they are responsible for more than 20% of the world’s oceans productivity. This could be due to currents transporting primary producers from one location to another, allowing for a greater dispersal of producers regardless of how restricted upwelling is.
Wind also has an effect in the way that is acts as a conveyor belt and pushes the coastal primary producers out to seas and draws in the ocean producers closer to the coast. Light also has an effect on coastal primary production as light can only penetrate the water so far, light/photosynthesis is what supports primary production. Without light, benthic producers cannot produce.
Of the marine primary producers included in the figure, which have the greatest carbon storage? Why is this the case?
Seagrasses have the greatest carbon storage. This is due to seagrass having the ability to store carbon in its roots and soil. According to a study by J.W. Fourqurean seagrass meadows store up to ninety percent of their carbon in the soil and are able to continue to build on these amounts of carbon for centuries.
Fourqurean, James W., et al. “Seagrass ecosystems as a globally significant carbon stock.” Nature Geoscience 5.7 (2012): 505-509.
Explain how coastal wetlands sequester and store carbon.
Sequester: Within coastal wetland environments plants collect carbon from the air and use it to produce their leaves, roots and stems. In turn plants also release carbon dioxide after using the carbon to produce energy – this is photosynthesis.
Storage: Carbon can be stored in the leaves, roots and stems of plants. When dead parts of these plants fall to the ground they are often covered by tidal waters (wetland environment), because of this the plant materials take a long time to break down allowing for carbon to remain stored. Carbon can also be stored in the surrounding soil, for example when a plant dies the carbon is released into the soil as the root system dies. It can stay trapped for many years.
What are the key threats to blue carbon, and how might these be curbed?
The largest threat to blue carbon is clearing of mangroves, saltmarshes and seagrass in order for further urbanisation (coastal development) and aquaculture (farming).
The loss of these aquatic plant life causes the sedimentation to mix, releasing carbon that may have been trapped for extended periods of time. When this carbon is released (CO2) it goes back into the atmosphere causing many issues in regards to climate change etc.
It is suggested that the loss of these ecosystems is causing approx. 500 million to 1 billion CO2 tonnes to be released into the atmosphere per year.
As banning coastal development entirely seems impossible – due to the need of land, urbanisation and aquaculture economy (fishing for money, food etc) in developing countries, I believe there needs to be a better monitoring system put in place. If a location can be tested and found to contain blue carbon deposits then that area can be protected, this enables the protection of high stores of carbon however still allows for developmental growth along the coast. Incentives may also help in the way that people are offered lower prices for land in areas where blue carbon deposits are found to be lowest/non-existent in comparison to locations where blue carbon deposits are highest and “Protected”.