unlightadmin / March 17, 2019
unlight, water, temperature, food and air are the five basic needs that every living organism on earth requires to survive. However, factors called ‘limiting factors’ in a living organism’s environment can prevent it from surviving there. Limiting factors are described as an issue that limits growth, abundance, and distribution of a population of organisms in an ecosystem outside of their preferred niche (Biology Online 2018). Shelford’s law is a law of tolerance, that states everything exists within a niche, beyond that, the organism is only existing within its range of tolerance and outside of that, due to these limiting factors, the organism won’t exist. Predators are an example of limiting factors, they can limit an organism’s niche and particularly where it can find safety and will also limit food sources. However, not all relationships are competitive, organisms may also seek positive interactions. Examples of positive relationships include commensalism and mutualism. Commensalism occurs when one species benefit and the other is unaffected, for example, when remora fish ride attached to sharks and other fish. Whereas, mutualism befalls when both species benefit, for example, sea anemones and clownfish (Science Struck 2018 and NECSI 2018).
Corals are invertebrate animals belonging to a large group of colourful and fascinating animals called Cnidaria, they are composed of thin plates, or layers of calcium carbonate created over time by hundreds of soft bodied animals called coral polyps (ICRI 2018 and Reef Relief N.D). Each polyp lives in a symbiotic relationship with a host zooxanthella that gives the coral its colour by taking in carbon dioxide, processes it through photosynthesis and then gives off oxygen. As the process of photosynthesis needs a lot of sunlight, the coral must be exposed to a sufficient amount and are limited to shallow waters that are clean and clear (Reef Relief N.D). Two kinds of coral exist, these include, hard and soft. Hard corals such as brain, boulder and branching have rigid exoskeletons that protect their soft delicate bodies. Soft corals such as sea fans sway with the currents and lack an exoskeleton.
Coral reefs are one of the most biologically diverse ecosystems on earth and is home to by far one of the most colourful and diverse groups of animals (The Sea N.D and Kerry N.D). They are the result of millions of years of coevolution among algae, invertebrates and fish. The different types of animals found along the Reef help make it one of the richest and most complex natural systems on Earth. In fact, it is home to more than 1,500 species of fish and 411 types of hard coral (WWF 2018). According to Coral Reef Alliance (2018), coral reefs are known comprise 25% of the biodiversity of marine life, however, are only occupying less than one percent of the ocean floor. This is because of the importance in withstanding and recovering from impacts and stress and being resilient to changing conditions (QPRMBA 2018 and Coral Reef Alliance 2018). Other important reasons for having a diverse range of species among reef habitats is how they provide habitats for marine organisms and are the source of nitrogen and other nutrients for food chains (QM 2018). As coral types vary, so do the fish species that are living in close proximity. ‘Branching’ refers to any branching coral, for example Acropora species and ‘Boulder’ refers to rounded corals such as some Platygyra and Porites species (Coral Watch 2018). Branching coral have a more diverse range of species in comparison to boulder coral as it provides fish with protection and camouflaging zones to hide from predators, due to the extensive structure of branching coral (crevices), compared to the smooth, rounded boulder coral. Rugosity is a simple measurement of the surface roughness, it is the state of the ruggedness (Magno and Villanoy 2006). Increasing the surface area of coral will increase the fish species that exists there. This is because, an increase of surface area means a further amount of rugged surface, creating more crevices for fish to occupy. Therefore, areas of high rugosity are likely to provide more cover for reef and consequently, proving that branching coral accommodates more fish in comparison with the smooth boulder coral.
Hypothesis: Branching coral will have increased fish species biodiversity as compared to boulder coral.
(Changed) Dependant Variables
(Measured) Controlled Variables
(Kept the Same)
• Coral types • Fish biodiversity • Weather
The experiment being conducted took place in the Lady Elliot Island lagoon, on the eastern side at the permanent transect line, which encompassing an extensive area of protected coral reef with variety of fish species in close proximity to a diverse abundance of coral types for habitat needs. Three quadrates were placed on coral to identify coral types, these included, branching coral, boulder coral and no coral sections. To estimate the biodiversity and structure of the fish community on coral types in the lagoon, 3 RUV’s (remote underwater video) were swum out, sunk in the sand in front of each of the 3 sections of coral and set on record for 30 minutes, to ensure each location had an equal amount of time. The variables present throughout this experiment were the coral types surveyed, portraying the independent variable and fish biodiversity as the dependant variable. Controlling the experiment was represented by 0% coral cover which could be used to compare and contrast the different types of coral present. Time and location were controlled within the experiment, which also allowed temperature, tide, dissolved oxygen, available nutrients and surface conditions. The cameras were then collected and placed on a hard drive. The data collected was then viewed and filtered into two groups; supportive data and unhelpful data such as, footage showing no signs of fish on coral, or blurry/ jittery footage, which was discarded, leaving 3 clear videos of each section of coral (branching, boulder and no coral) to analyse. Every 3 minutes, 30 seconds of each video was analysed, and the fish species biodiversity was identified and the maximum number (max n) of each fish species was calculated by counting every fish species on the screen at that given time. To ensure a fair experiment, each video had only 4 lots of 30 seconds watched. Tables and graphs were created to display the results clearly and were then analysed and discussed.
A variety of risks had been revealed through conducting this experiment ranging from low to extreme risks. To ensure safety for yourself and others around, safety precautions are taken. Reef shoes were worn to prevent students from stepping on coral, not only to prevent destroying the coral habitat but to prevent the students from getting coral cuts also. Wet suits were also worn for the purpose of both safety and comfort. The buoyant wetsuits were a safety precaution, making it easier to swim but also made swimming in freezing water, very comfortable. Lastly, at the end of every snorkelling session, it was made clear, any coral cuts were to be reported and taken care of immediately to avoid infection.
Legend- red = fish that are present only in that specific coral
(lagoon) Present coral type/s Present fish types
No coral Thumbprint emperor (Lethrinus harak, Max n 24), Threadfin butter fly fish (Chaetodon Auriga, Max n 7), Yellow angel fish (Centropyge heraldi, Max n 1),
Sangi cardinal fish (Fibramia thermalis,Max n 2) Multispine damsel (Neoglyhidodon polyacanthus, Max n 7)
Boulder Thumbprint emperor (Lethrinus harak, Max n 22),
Black saddle goatfish (Parpeneus spilrus, Max n 1), Lemon damsel (Pomacentrus moluccensis, Max n 5), Moses snapper (Lutjanus argentimaculatus, Max n 5), Sharp nose grub fish (Parapercis cylindrica, Max n 4), Yellow fin hamlet (Hypoplectrus chlourus, Max n 4, White bait (Galaxias), Max n 4).
Branching Threadfin Butterflyfish (Chaetodon Auriga, Max n 5), Thumbprint Emperor (Lethrinus Harak, Max n 51), Lemon Damsel (Pomacentrus Moluccensis, Max n 17), Yellow Fin Hamlet (Hypoplectrus Chlourus, Max n 56), Sergeant Major (Abudefduf Saxatilis, Max n 36),
Moses Snapper (Lutjanus Argentimaculatus, Max n 5), Spiny Puller (Acanhocromis Polycanhus, Max n 15), Coral Sea Gregory (Stegastes Gascoynei, Max n 1),), White Damsel (Dascyllus Aruanus, Max n 3),
Stout Body Puller (Chromis Chrysura, Max n 6),
Bird Wrasse (Gomphosus Varius, Max n 1),
Starry Eye Parrot Fish (Calotomus Carolinus, Max n 2), Blackbutt Butterflyfish (Chaetodon Flavirostris, Max n 5), Blacktip Silverbiddy (Gerres Oyena, Max n 13),
Reef Crest Parrotfish (Chlorurus Microrhinos, Max n 1), Half and Half Puller (Chromis Iomelas, Max n 2),
Fringe Lip Mullet (Crenimugil, Max n 6),
Lined Brissle Tooth (Ctenochaetus Striatus, Max n 3), Sailfin Tang (Zebrasoma Veliferum, Max n 3),
Smooth Tail Trevally (Selaroides Leptolepis, Max n 1), Black Butterfly fish (Chaetodon Melannotus, Max n 1),
The videos produced from this experiment demonstrate that the most prevalent coral structure in the Lady Elliot lagoon is branching coral, which is home to the greatest variety of individual fish species in the lagoon. The location containing branching coral supports a significantly larger diversity of fish species, accommodating 25 different species. Table 1 represents the diversity of species among the coral types clearly, showing that the boulder coral knowingly decreases in fish biodiversity, as it is only supporting 8 species. Even lower, the no coral sections were showing to support just 5 types of fish. After analysing the data collected, a distinct relation between the number of certain fish species with types of coral has occurred. Branching coral has shown to be encompassing a greater range of fish species, where small fish override the population. Fish such as Half and half pullers are just one of the small fish occupying branching coral for habitat uses as is creates shelter and protection for the fish. Due to the complex structures of coral reefs, with their many nooks, crannies, and hiding spaces, the fish that are found in and around branching coral have adapted small, manoeuvrable body structures to hide in the coral. Damselfish species are expected to have close associations with habitat structure due to their site attached behaviour (PLOS 2013). Other small fish such as Coral Sea Gregory fish are brightly coloured and use branching coral to hide from predators as they have the ability to camouflage using their colouration against coral shades. Thus, supporting the hypothesis of a greater fish biodiversity existing in branching coral in comparison to the other coral types. It can also be seen that a small existence of fish species was using boulder coral as habitats. Larger fish such as, Moses Snapper’s and Sharp Nose Grub Fish were of these species using boulder coral, as they are in less need of protection from predators and boulder coral does not have an extensive range of protective qualities like branching does. Finally, an even lower number of species were found in no coral locations, also proving that a greater range of species live within coral areas, specifically more in branching. The even larger types of fish include; Multispine Damsel fish, they commute in schools to protect each other and are in no need to be protected by coral.
An experiment conducted on Lizard Island reveals a similar hypothesis and results to the Lady Elliot testing. The Lizard Island investigation examined the strength of the relationships between habitat features and local fish diversity, abundance and community structure in the lagoon of Lizard Island, Great Barrier Reef. Results in this experiment comprise findings of how hard coral cover had a weak but significant positive relationship with coral species richness. Therefore, it is reasonable to assume, that a reduction in hard coral cover would be associated with some reduction in coral species richness. This experiment had similar finding to the lady Elliot experiment in the sense that they found the habitat appeared to not only influence fish species richness and abundances, but also species composition. Hard coral cover, habitat complexity, coral species richness and branching coral cover were identified as important variables in determining fish community structure. Lastly, the experiment shows the same findings, that smaller fish species occupy branching coral as they are susceptible to predation. These findings are shown through their results of; smaller fish species would be expected to be more vulnerable to predation and the availability of a range of shelter sites might have fitness advantages for these species (PLOS 2013).
This experiment and the results calculated with, proved true to the thesis that a larger variety of fish species existed in branching coral compared to boulder and no coral. Taking into account the anomalies and experimental errors, improvements to this experiment could be made to ensure a fairer test. Anomalies affecting the conducting of this experiment include the uncontrolled variables of temperature, location and human interactions. As the collecting of data took place at midday, on a hot and sunny day, the water temperature went up a 4-degree increase, from 21 to 25 degrees, reducing the dissolved oxygen concentration and also increasing respiration rates. This demonstrates that water temperature can affect the metabolic rates and increase respiration rates of aquatic organisms. Increased respiration rates at higher temperatures lead to increased oxygen consumption, which can be detrimental, creating an unsafe habitat for marine life. (FONDRIEST ENVIRONMENTAL 2016). Therefore, creating an anomaly in the data, as the water was affecting the organisms, reducing the number of them. Human interaction also caused anomalies in the data. Up to 30 students collected data at the same time, in a small passage way in the lagoon, causing water movement and noise, chasing the fish away. Interrupting the presence of organisms would have caused major outliers in the data, as many more fish could have been observed and filmed if they weren’t scared away. Experimental errors that occurred during the experiment could have also impacted on the results gathered. As Lady Elliot Island is a green zone, no fishing is permitted within the boundaries. This is also the case with BRUV’s (baited remote underwater video), as they are protecting the marine life. These BRUV’s are what are usually used to collect data from underwater in marine science, but as there was no permit to do such, a RUV was used instead. The RUV works and films the exact same, the only difference is one is baited, and the other isn’t. The data collected using the RUV was still useful but there is definitely potential to record many other species using the bait. There is also the chance, that using a BRUV would attract fish into unwanted destinations, such as boulder corals, therefore disrupting the data even more. Other strategies to improve this experiment and making in a fair test could be using longitudinal and repetitional data. Longitudinal data is data collected over a long period of time, to improve the accuracy of the results from Lady Elliot, longitudinal data could be used as a more reliable source, collecting more footage and data over a longer period of time. Repetitional data is the collection of data that is repeated. Repeating the experiment on Lady Elliot could also create accurate results as any anomalies would be revealed. These reasoned improvements could ensure a fair experiment, therefore preventing outliers in the data and making the results clear and reliable.
The videos and data gathered represents a clear relationship between a large biodiversity of fish species and coral types. After analysing the data collected, a distinct relation between the number of certain fish species with branching coral has occurred. As branching coral structures have protective nooks, crannies and hiding spots, most fish species inhabit branching coral for protection against predators. Many species are suggested to use corals for refuge sites as they are the most favourable coral types in comparison with the other two less diverse habitats. Thus, supporting the hypothesis of a greater fish biodiversity existing in branching coral in comparison to the other coral types. Consequently, we should expect that loss of branching coral species or reduction in coral cover will have a significant impact on fish communities and these factors must be distinguished in future studies.
Coral reefs are very prolific ecosystems. Not only do they support vast biodiversity, they are also of immense worth to humankind, such as tourism, fisheries and coastal protection. Almost everything in a coral-reef system depends on corals, or on the reef structure in some way as they provide a source of food and shelter for organisms. The results revealed in this experiment could possibly be affected by other broader scientific issues such as coral bleaching. According to National Ocean Service (2018), when corals are stressed by changes in conditions such as temperature, they eject the symbiotic algae living in their tissues, causing them to turn completely white. Fertilisers have also been linked with coral bleaching, deteriorating water quality and reducing the growth rate.
If the Great Barrier was to experience extensive coral bleaching, a significant decrease in fish species will occur, as organisms are attracted to living coral and avoid unhealthy coral. A severe decrease in branching coral would also occur as branching coral is at a greater risk of being affected by bleaching, because of the weakness of it (Nogrady 2017). A decrease in branching coral will have detrimental effects to the biodiversity of smaller fish occupying it, as they are losing protection. This will lead to an unstable reef habitat as most of it will die due to the removal of important habitat mutualism relationships. Coral reefs play a vital role in sustaining the health of oceans and economy. NOAA is at work to increase the education and understanding of the causes of reef declining and coral bleaching. Scientists are racing against time to lessen the damage from coral bleaching and are already working on several projects to prevent bleaching, including placing shades above corals during the summer (UQ 018).
Possible solutions for society to participate in declining the risk of coral bleaching are to conserve water, the less water usage, the less runoff and wastewater that will eventually find its way back into the ocean. Become an informed consumer and learn how daily choices such as water use, recycling, seafood, vacation spots, fertilizer use, and driving times can impact the health of coral reefs (National Ocean Service 2018). Through the execution of these solutions, coral reefs will be able to regenerate over time and in the future, will bring an end to coral bleaching.