Impresión:PHYTOPLANKTON: THE BASIS OF THE FOOD CHAIN DOOMED?

Alejandro Albarracin, Juanita Barrera, Natalia Cruz, María Alejandra Gómez, Manuela Rivera, Cristian Rojas, Aletia Sánchez.

RESULTS

THE GREAT BARRIER REEF

The Great Barrier Reef is located at the Coral Sea, in front of the coastline of Queensland at the northeast of Australia. Since 1981, this ecosystem has been considered as a world heritage as it is estimated it has approximately 3,000 individual reefs and 900 coral islands separated by aisles underneath the sea. Accordingly, this chain extends for around 2,600 kilometres making it the longest coral reef of the world.

Additionally, inside this ecosystem, reefs are used as protection barriers for mangroves and seagrass beds which are other habitats found in the area. These also protect corals by avoiding sedimentation, a by-product of rock erosion. For that reason, by co-existing different sub-habitats the Great Barrier Reef has characterized for having high levels of marine biodiversity in comparison to other parts of the world.

Nonetheless, global warming and the amplification of ultraviolet radiation has caused a negative impact for this ecosystem in phenomena like ocean temperatures, ocean acidification and light availability. These being key variables for an optimal growth of one of the organisms that constitutes its high biodiversity: phytoplankton. Subsequently, if these are affected somehow, there will be significant changes in the environment that will become an obstacle to the production of this organism.

Thus, being phytoplankton the primary producer of its food chain, a study was conducted to analyse how directly related organisms such as zooplankton and krill were influenced. Considering that population dynamics of all the organisms mentioned (phytoplankton, zooplankton and krill) are key indicators to general biodiversity of the area, this lets us estimate their behaviour in years to come.

CONCLUSION

Phytoplankton, and in most cases zooplankton, have been affected by three main variables: sea temperature,ocean acidification and ultraviolet radiation. Despite having a negative relation, rising sea temperatures is thevariable that affects phytoplankton the least in comparison to the other two. On the other hand, ocean acidificationdoes have great influence in phytoplankton showing changes in its population dynamics. Lastly, variations in lightand ultraviolet radiation also affects several behaviors of this organism, specially its abundance period.

Therefore, we can conclude directly that:1.Phytoplankton is greatly affected by its environment and the specific variables mentioned above.2.Although there is evidence of damages in its population dynamics, because of global warming, phytoplankton’shigh biodiversity, short life span and genetic recombination give it an advantage to avoid its total disappearance.

However, the fast rate at which these variables are changing will have a notable impact on higher levels of theoceanic food chain as phytoplankton is the primary producer. Primarily, since the biggest changes are expected tobe seen in its nutritional value, quality and quantity as food for other animals.Hence, the following question is made: Do we need to wait for the basis of the oceanic food chain to be doomedto take action?

Octubre 2006 Octubre 2016

Octubre 2006 Octubre 2016

Global warming is a phenomenon that has affected oceans considerably by increasing its temperatures and exposition to ultraviolet radiation. A direct consequence has been its influence on phytoplankton, the organism that fulfils the role of the basis of the oceanic food chain and the responsible of producing the greatest quantity of oxygen that can be found in the atmosphere.

The Great Barrier Reef is a maritime area with substantial biodiversity levels in regards to the rest of the world. This way, the anomalies of concentrations of phytoplankton and therefore, zooplankton, which is its primary consumer, will have an influence on the species in higher trophic levels found in the area.

THE ROLE OF PHYTOPLANKTON

Fig. 2 Chlorophyll concentration

Fig. 3Sea temperature

Fig. 1 Chlorophyll anomalyvs Temperature anomaly

BIBLIOGRAPHY

• David McKinnon, Anthony J Richardson, Michele A. Burford, Miles J Furnes. ¨Vulnerability of great barrier reef plankton to climate change. ¨ http://www.gbrmpa.gov.au/__data/assets/pdf_file/0012/5421/chpt-6-McKinnon-et-al-2007.pdf. 2007.

• CSIRO, ¨Plankton 2015, state of Australia´s ocean.¨ http://imos.org.au/fileadmin/user_upload/shared/Data_Tools/15-00245_OA_Plankton2015_20ppBrochure_WEB_151116.pdf.

• Fig. 2 and Fig. 3 https://earthobservatory.nasa.gov/Features/Phytoplankton/page5.php• Fig. 1 "What are Phytoplankton? : Feature Articles", Earthobservatory.nasa.gov, 2017. [Online]. Available:

https://earthobservatory.nasa.gov/Features/Phytoplankton/page5.php. Fig. 3

Plankton is the term used to describe those organisms whose power of progressive motion is very limited compared to the body of water they live in. These organisms come in a wide variety of sizes each with different characteristics, since they can be as small as a virus (femtoplankton) and large as a jellyfish (megazooplankton).

Phytoplankton, another type of plankton, is responsible for approximately half of the global primary production in the ocean, therefore it plays an important role in the atmospheric cycle of carbon dioxide Since phytoplankton consumes as much carbon dioxide as forests to the point that if there is a small change in its population it could generate a great impact on the CO2 concentrations in the atmosphere.

Moreover, plankton is one of the most important primary producers in the GRB ecosystem since it fixes about 70% of the 2.2 x 105 tonnes of carbon dioxide that are fixed daily in the GRB. Additionally, it is estimated that at least two thirds of this is fixed especially by picoplankton.

On the other hand, plankton organisms such as micro- and mezooplankton are the basis of many food chains. So they have become the support of a series of organisms that feed by suspension-feeding and other planktivorousfishes, which can be found in coral reefs.

INFLUENCE ON PHYTOPLANKTON

VARIABLES GENERAL SPECIFICTemperature

• Phytoplankton is a poikilothermic organism (lacks of temperature-regulating mechanisms)

• Their growth, development and distribution depends on this factor• As the ocean's temperature increases, the number of available

phytoplankton decreases (Fig.1)

• Species that do not resist temperature change, migrate slowly to latitudes where they find optimal conditions (Fig. 2 and Fig. 3) Hence, there isn’t a general reduction in the satellite images.

• The quality, amount and nutritional value of food (Zooplankton and Phytoplankton concentrations) for higher trophic levels, decreases

Ocean acidification• The ocean's high pH causes a reduction in carbonated minerals that affect

the calcification of certain types of phytoplankton. • When nitrogen and phosphorus concentrations show an unbalance in water,

the production of zooplankton is affected.

• The specie of phytoplankton that is affected the most by changes in the ocean's pH is the Cavolinia longirostris.

• A reduction in pH levels disturbs the growing rhythm of photosynthetic organisms as it affects the way in which they absorb nutrients in water

• Changes in the cellular composition of phytoplankton harm their nutritional value

• It is estimated species with carbonated structures will disappear and remaining species will thrive

LIGHT AND ULTRAVIOLET RADIATION • They are photophilic organisms (organisms that require an illuminated

environment to live) • There might be mutations and cellular death in this organism due to the fact

that the process of photosynthesis and respiration is affected by this factor • Considerable increase in pigmentation altering their chemical composition • Ultraviolet radiation changes nutrient concentrations in water

• In tropical regions like the Great Barrier Reef, the projection of ultraviolet light has more intensity that in other regions

• Ultraviolet light damages another copepod specie, the Acartia clausi, which is affected as its adult life is reduced

• Additionally, eggs and larvae from distinct species are also affected directly