Food Webs in the Great Barrier Reef: Explanations and Challenges

Food Webs and Biomass Pyramids 

Food chains and food webs are part of an ecosystem and can be described as the community of Autotrophs and Heterotrophs that feed, reproduce, respire, interact and die in the same environment (Rachna, 2017). As well as the decomposer, which is a continuous procedure of cycling nutrition for the consumer to use again. The diagrams illustrated above, display all the interconnecting pathways throughout the food web and biomass pyramid also all possible feeding relationships between producers, primary, secondary and tertiary consumers accompanied by the predator and prey relationship within each trophic level.

Abiotic and Biotic Components 

The Great Barrier Reef principally comprises from numerable biotic (living) and abiotic (non-living) components, which create interdependencies that are contingent for the overall survival and sustainability of this natural ecosystem. Additionally, biodiversity is the foundation of ecosystems diversity within and between species (Digests, 2019). Thus, without biodiversity the sustainability of the environment would be jeopardized (Gillaspy, 2019). Within the GBR ecological sustainability is when its biotic components- living factors- can rejuvenate themselves and maintain suitable living conditions for the community when responding to fluctuations of abiotic- inorganic chemical/physical parts that affect living organisms- factors (Gillaspy, 2019).

Interdependencies Between Abiotic and Biotic Components 

With further investigation numerous relationships between abiotic and biotic components can be identified throughout the GBR. Coral is a significant factor for the overall survival of this ecosystem. Coral relies on sunlight and sunlight penetration in order to provide the zooxanthellae and coral polyps with compounds needed for photosynthesis (Noaa, 2017). Which is when carbon dioxide and water is transformed using sunlight and chlorophyll to produce glucose and oxygen (RSC, 2018). In return the algae use that oxygen to help the coral remove wastes (Noaa, 2017). This process enables survival for the coral, and a food source for the primary consumers. Decreased salinity levels will also result in coral dying, as fluctuations in precipitation will increase runoff of sediment, freshwater and land-based pollutants causing an unbalanced ratio of salt to water (CRA, 2019). Also contributing to algal blooms, causing murky water conditions which will reduce the amount of light to travel through the water (MPA, 2019). Which as evidenced means clear water is a crucial factor for photosynthesis. The abiotic components buoyancy and viscosity affect the sea animals of small/ large reef fish, sharks and ray's ability to swim within the water. Buoyancy is demonstrated by keeping marine animals afloat, by when the buoyant force equals the objects weight it remains suspended at that dept (Lumen, 2018). Which is why it is dependent on water density, as the net force increases with depth (Lumen, 2018).

Whereas, viscosity influences stimulus to the fish lateral-line system (Windsor, 2017). As the fish's body creates flows that interfere with the detection of external signals and give information about nearby obstacles and their own hydrodynamic performance (Windsor, 2017).

Research has allowed the conclusion that abiotic components collaborate in order to create sustainability within the ecosystem, which subsequently cause significant affects for the energy transfer in the biomass pyramid and how every living organism depends on abiotic factors for survival.

How Energy is Transferred Through Interdependencies Between Organisms  

The GBR encompasses multiple interdependencies between two or more organisms. An affiliation whereas they live closely together, known as a symbiosis relationship. Entailing commensalism, mutualism and parasitism (GSLC, 2019). Conversely with symbiosis bioaccumulation and biomagnification can too, affect how energy is transferred through a biomass pyramid (Toxicology, 2017). Bioaccumulation is when there is a gradual accumulation of living chemicals in the tissue of an animal, and biomagnification occurs when compounds (pollutant or pesticide) increase their concentration in the tissue of organisms (Toxicology, 2017).

Commensalism is when one species obtains benefits whilst the other is unaffected (Britannica, 2019). For instance, suckerfish attach themselves to larger marine animalssharks and manta rays- via a specialized organ (RICE, 2017). This allows the fish to travel with their hosts, and collecting their food particles (RICE, 2017). This means the energy is transferred when the suckerfish eats the food particles on the host, for 10% of the hosts energy will be carried through, ready for the next predator to consume the fish for only 10% of the fish's energy will be transferred.

Mutualism is where both organisms benefit from the interaction (Britannica, 2019). This can be demonstrated between clown fish and coral (Sackett, 2018). Coral provides food and shelter to the corallivores, and in return they offer protection for the coral from its competition of seaweed (Sackett, 2018). Thereby, as evidenced 10% of the coral's energy is transferred when the clown fish consumes the food supply. Parasitism, where one benefits at the expense of the other, often concluding in killing the host (Britannica, 2019). An example is the parasite, Amakusaplana acroporae which infects and destroys the staghorn coral (host) rapidly (YaleEnvironment, 2014). How it destroys host

When eating the coral tissue, it ingests the coral's symbiotic algae and keeps a fraction of them alive to distributes them, along with the fluorescent pigments throughout its gut so that it perfectly mimics the appearance of the coral whilst also 10% of the corals energy is being transmitted through (YaleEnvironment, 2014).

An examination of the findings can justify the fact that symbiosis relationships are vital in order for energy to be transmitted up the food web and biomass pyramid. As well as the overall survival and diversity of species in the GBR.

Threats of Temperature Fluctuations 

Fluctuations of temperatures are significant threats to the GBR, causing ocean acidification and rising sea temperatures. Living organisms will then respond with structural, behavioural and physiological adaptations to survive this heat-stress (Cranitch, 2019). Ocean acidification will change the ocean chemistry, decreasing the capacity of corals to build skeletons. Thereby as a structural adaptation the coral will expel the poisonous zooxanthellae, as temperatures in excess of 30 degrees blocks photosynthetic reactions (Reefteach, 2017). Behavioural adaptations of climate change will cause fish to establish themselves in different areas, so as to stay within their preferred temperature range (minimum of 20 degrees) (GRRMPA, 2019). Physiological adaptations would be demonstrated by larger endothermic marine animals (sharks, whales and rays) Whom have the ability to cope with the temperature fluctuations by maintaining a constant body temperature that is not dependent on surrounding water (RHA, 2019). All evidence emphasises that fact that without an organisms adaptation, the significant threat of climate change would destroy the foundation of this ecosystem (coral), consequently decreasing the primary consumer and eventually other organism from higher trophic levels.

Coral also relies on warm water temperatures of 20-30 degrees as a necessity for survival (CRA, 2019). However, some reefs in different regions can withstand various temperature variations. Temperatures in excess of 30 degrees for a period of time, will result in a suspected effect of global warming, coral bleaching (RSC, 2018). Causing coral to expel algae living in their tissues, by exposing the coral's white exoskeleton (NOS, 2018).

Traditional Indigenous Fishing 

Traditionally, fishing has been a custom the indigenous people have carried through decades in the GBR. Their methods included hand-lining, diving, spearing and cast-netting, which has been efficient in catching marine species for subsistence and cultural uses (TSRA, 2019). However, the GBRs ecosystem is being disrupted. Because of cast-netting, corals are being destroyed and consequently the ecological niche of species is becoming threatened (NOS, 2019). Additionally, catching smaller fish will lead to breeding of smaller offspring which can be problematic, as smaller females means they are less fecund (NOS, 2019). Meaning it will cause impacts and decrease the fish population, as well as genetic diversity of species marking them more susceptible to disease, and less likely too adapt to stressors in their environment (NOS, 2019). By targeting specific species, it disrupts food webs, as too much fishing of preys will reduce the food supply of predators and decreasing their population (NOS, 2019). However, on the other hand, if predators are being targeted, it will consequently increase prey population. Therefore, traditional indigenous fishing can significantly impact population size, survival of each organism, whilst succeeding in disrupting the overall ecosystem.