PRE2019 3 Group17

Group Members

Name	ID	Email	Major
Amit Gelbhart	1055213	a.gelbhart@student.tue.nl	Sustainable Innovation
Marleen Luijten	1326732	m.luijten2@student.tue.nl	Industrial Design
Myrthe Spronck	1330268	m.s.c.spronck@student.tue.nl	Computer Science
Ilvy Stoots	1329707	i.n.j.stoots@student.tue.nl	Industrial Design
Linda Tawafra	0941352	l.tawafra@student.tue.nl	Industrial Design

Work Breakdown & Task Division

Work Hour Breakdown

Work Breakdown per Group Member per Week

	Week 1		Week 2		Week 3
Name	Total Hours	Work Breakdown	Total Hours	Work Breakdown	Total Hours	Work Breakdown
Amit Gelbhart
Marleen Luijten
Myrthe Spronck
Ilvy Stoots
Linda Tawafra

Problem Statement and Objectives

Problem Statement

“Coral reefs worldwide are increasingly damaged by anthropogenic stressors”(Gordon, et al., 2019). We look towards alternative methods of reviving dying and dead coral reefs. Acoustic enrichment is a tested method that seems to be able to bring fish back to coral reefs. Robots could be created to automate labor and time-intensive work, as well as remove the skill floor required to revive a local reef.

Objectives

The main objective of the robot is to prevent reefs from downgrading by improving the coral reefs' resilience and bring back dead coral reefs through attracting fish. Additionally, the robot helps with monitoring and managing coral reefs by automating manual labor and improving data efficiency.

Prevent downgrading

Due to the acidification and warming of oceans due to climate change, pollution and destructive fishing practices (Ateweberhan et al., 2013)the amount of coral reefs is declining. One of the factors that could prevent the downgrading of a reef, is the resistance of a reef, its ability to prevent permanent phase-shifts, and the resilience of a reef, its ability to bounce back from phase-shifts (Nyström et al., 2008). These phase-shifts are undesirable because the reef ends up in a state where it can no longer return to a coral-dominated state (Hughes et al., 2010). If the reef has better resilience, it will be able to bounce back quicker. The robot improves the resilience of the reef by increasing the species richness and abundance through the use of acoustics (Gordon et al., 2019), which improves the reef’s resilience by giving it protection from macroalgae (Burkepile and Hay, 2008).

Bring back dead coral reefs

For a coral reef to flourish, a wide biodiversity of animals is needed. Fish that lay their larvae on corals are one of the essential components in a healthy reef ecosystem. However, once corals are dying, the fish do not use them for their larvae and the whole system ends up in a negative cycle. By playing sounds, with different frequencies, fish are tricked into believing that the corals are alive and come back with their larvae. This attracts other marine animals, which causes the entire system to flourish again (SOURCE!!).

Monitor and manage coral reefs

The monitoring of coral reefs nowadays is a time consuming and cumbersome method, which requires a lot of manual activities (SOURCE!!). The robot is able to scan reefs and provide researchers with an accurate and continuous database regarding the status of the coral and the population of fish and other marine animals. This reduces the amount of manual actions that otherwise would have been performed by divers and researchers. The database allows researchers to study reef ecosystems worldwide, which leads to a better understanding of the ecosystems and allows better management.

sources used in this section:

https://www.nature.com/articles/s41467-019-13186-2 https://www.pnas.org/content/105/42/16201.short https://www.sciencedirect.com/science/article/abs/pii/S0169534710001825 https://link.springer.com/article/10.1007/s00338-008-0426-z https://www.sciencedirect.com/science/article/abs/pii/S0025326X13003020?via%3Dihub

Literature Study

Use of acoustics for coral fish

• (https://www.nature.com/articles/s41467-019-13186-2). The nature article we based ourselves on. Experiment to test the effects of acoustic enrichment. They set up loudspeakers that broadcast healthy soundscapes for 40 days, specifically on coral-rubble patch reefs in Australia’s northern Great Barrier Reef and compared the development of local fish communities to those in reefs with no speakers at all and ones with speakers that broadcasted no sound at all. After 40 days they found that there were more fish present of each trophic guild (herbivores, omnivores, planktivores, invertivores and piscivores), with the balance of fish types being unaffected. The acoustically enriched reefs also had 50% increased species richness. This study did not experiment with different types of sounds but based itself on other studies that have done so (later sources). The study acknowledges that the speakers create relatively small acoustic halos, but they suggest that since fish tend to migrate away from their initial settlement site, the extra fish will also move to other parts of the reef. They suggest further research must be done on the effects in different reef habitats, how the acoustic enrichment affects adult fish, the long-term effects of enrichment and the spatial scale of the effects. They recorded the audio transmitted by the loudspeakers again at 1m, 50m and 100m distances and found that at 50m distance from the loudspeaker the transmitted audio already cannot be detected anymore. The specifics of their loudspeaker, amplifier, battery and mp3 player are mentioned in the method section. Speakers were angled upwards for even audio distribution. The audio used was actually from the same reef, but taken before two major bleaching events. The audio was only played at night as that is when settlement behaviour happens. There were a few days throughout the process where acoustic transmissions were interrupted, this seemed to have no negative effects on the final result.

• (https://www.int-res.com/abstracts/meps/v533/p93-107/). This study is an analysis of the acoustics of a few different coral reefs and how they could be used to assess the state of a reef. It suggests that different reefs (in different parts of the world) sound very different. Data from a single recorder can be used to analyse the whole reef, as there is very little variation in acoustics throughout the reef. The acoustics of a reef vary a lot throughout the day. To use acoustics to analyse a reef you really need at least 24 hour recordings. Low frequency sounds give a better indication of the fish density than high frequency sounds (below 1000Hz).

• (https://www.sciencedirect.com/science/article/pii/S0003347207005933). In general, larval fish are attracted to 570-2000Hz reef noise more than no sound or <570Hz reef noise. Some species have no preference, but the species investigated in this paper (specific names in results section, likely not relevant for us) were either ambivalent or preferred the >570Hz sounds. Additionally, low frequency sounds were still preferred to silence. The researches of this paper did not record and analyse their own sound transmissions, but believe that their speakers would have been noticeable up to 50m distance.

• (https://link.springer.com/article/10.1007%2Fs00338-010-0710-6). This study focusses on juvenile (non-larval) fish and how they are affected by acoustic ques. Here the speaker hung under a buoy and was pointed downwards. Also briefly mentions how different reefs have different progressions of noise throughout the day, and that most differences seem to be located in the 500-1000Hz range. Study indicates that some or all fish can distinguish between sounds coming from different habitats and specifically that reef sounds attracted fish more often present in reefs. The article makes no judgement on whether this is good or bad. The information that non-larval fish are also affected by audio cues is relevant because of

• (https://www.jstor.org/stable/40062249?seq=1#metadata_info_tab_contents) which is a study on the effects of audio cues for birds resulting in a decrease in species richness, but these are sounds taken directly from birds that are very territorial and it therefore makes sense that their sounds could scare other birds off.

• (https://academic.oup.com/icb/article/51/5/826/625886). This article explains what fish larvae are exactly, if we want this information. Acoustic cues for location are current-independent whereas olfactory cues are current-dependent, so fish must be capable of swimming upstream to use them. Both types of cues are location-dependent (unlike, for instance, magnetic fields or celestial bodies, which are location-independent). There are some indications that the larvae move towards sound at night, but away from it (or ignore it) during the day. Due to different olfactory receptors, different species of larvae might interpret the same batch of chemical differently. Fish cannot detect odour in stagnant water. Some larvae can imprint on specific olfactory cues.

• (https://pdfs.semanticscholar.org/0917/ba41332a801a60f2373d9ce172eced710720.pdf). Some families of fish don’t respond to sound at all. Most studies on using acoustic enrichment were carried out in just one region (Lizard Island). In a study in a different location, larvae were actually repelled by the noise. However, this was likely because they played daytime recordings at night, which as shown in other sources does not work. It might also have been because the healthy reef sounds were recorded far away from the reef that the experiment was performed on. This is not necessarily a problem (the recording in the Lizard Island tests was from even further away), but in this case the ambient noise from the recording likely did not match to the ambient noise of the reef.

• (https://www.pnas.org/content/115/20/5193.short). Unhealthy reefs sound different from healthy reefs and larvae prefer the sounds from healthy ones.

Reef resilience

• (https://www.sciencedirect.com/science/article/pii/S0169534710001825). Once corals start to degrade (from overfishing, or bleaching events caused by climate change or pollution) they can end up in a phase-shift, where they no longer have the capacity to return to a coral-dominated state. “The resilience of a complex system (e.g. an ecosystem, society or economy) is its capacity to absorb recurrent disturbances or shocks and adapt to change without fundamentally switching to an alternative stable state”. More herbivorous fish present helps combat macroalgal dominance, which means that the fish protect the corals. Larval connectivity is important, which is the ability to fish larvae to reach the reef. There have been past instances where a coral reef experienced a phase-shift but, after the re-introduction of herbivorous fish, they returned to a coral dominated state.

• (https://link.springer.com/article/10.1007/s00338-008-0426-z). This paper attempts to operationalize the concept of resilience by looking at how the term has been used in the past and trying to settle on a clear, measurable definition. Resilience is only one part of the story, resistance is the other. It describes the resistance of a coral reef to phase shifts, rather than their ability to return to their old state (resilience). This paper is specifically on resilience. Once a phase-shift has happened, there are self-reinforcing systems to keep it in the new state. Even if it can return to a coral dominated state the change in species distribution reduces to resilience going forward. This article also gives a quick overview of how algae can prevent coral from reforming. Species richness and abundance improve response diversity and redundancy (a stable and complete ecological system), and so help resilience. Connected reefs (close to each other) can share resilience, they can quickly regain their biodiversity from nearby reefs. However, strong connectivity can also mean a quick spread of disease or invasive species. This paper expands on a lot of factors that could be used to assess the resilience of a reef, but this will likely not be relevant for our project.

• (https://www.pnas.org/content/105/42/16201.short). “Maintaining herbivore species richness appears critical for preserving coral reefs, because complementary feeding by diverse herbivores produces positive, but indirect, effects on corals,the foundation species for the ecosystem.” Herbivore fish eat macroalgae that compete with the coral, a diverse mix of fish means that no macroalgae are immune to all herbivores in the ecosystem. This is particularly important after a disturbance has taken place, because at that point the macroalgae will usurp the corals and cause a phase-shift

• (not the term used in this paper but the term for this used in another source we used). The presence of a diverse group of herbivore fish reduced algae cover, diversity and biomass. This allows the corals free reign, resulting in a larger coral cover and decreased coral mortality.

• (https://www.jstor.org/stable/30034127?seq=1).

• (https://pubmed.ncbi.nlm.nih.gov/25607371-predicting-climate-driven-regime-shifts-versus-rebound-potential-in-coral-reefs/).

• (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3377479/ ).

• (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3053366/).

• (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0003039).

The importance of coral reefs

• (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4354160/). Reefs reduce wave energy and therefore wave height, which reduces the risk and extent of the waves damaging structures on the shore.

• Need more sources

Alternative ways to help coral reefs

• (https://peerj.com/articles/1313/).

Other threats to corals

• (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2291018/).

• (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4841221/).

• (https://stopillegalfishing.com/issues/blast-fishing/). Blast fishing is the use of explosives to stun or kill fish to then collect. These explosions also damage corals, and kill any fish present.

• (https://www.sciencedirect.com/science/article/pii/S0025326X13003020?via%3Dihub). Climate change affects coral reefs in a number of ways, mainly through the warming of the oceans and ocean acidification. Other, local factors damaging coral reefs include overfishing/destructive fishing and pollution (brings both pathogens as well as nutrients that cause algae to grow too fast - the reasoning behind the damage of too many nutrients is not mentioned in this source). Shoreline alterations can also do damage. Climate change damages both the corals themselves as well as the calcifying algae they are built around. The warming of the oceans leads to coral bleaching events, which kills corals, reduces coral cover and, even if the reef survives, changes which kinds of coral dominate the reef. The acidification reduces calcification, which causes reefs to grow slower. Acidification can also cause bleaching events and slow down recovery after bleaching. Acidification can also damage fish and other organisms present in the reefs. It is also likely that warmer waters make coral reefs more susceptible to disease. Acidification makes olfactory detection less viable, particularly when it comes to detecting predators and prey. We cannot save coral reefs by addression just one factor, all destructive elements need to be dealt with.

Look up the crow-of-thorns starfish that keeps being mentioned Factors affecting fish recruitment

• (https://www.researchgate.net/publication/233715881_Rehabilitation_of_coral_reef-fish_communities_The_importance_of_artificial-reef_relief_to_recruitment_rates).

• (https://link.springer.com/article/10.1007/s00442-007-0773-4).

Acoustics underwater

• (https://link.springer.com/article/10.1007/s00338-012-0892-1).

• (https://asa.scitation.org/doi/abs/10.1121/1.2836780).

Users and Needs

Tasks:

For whom would the invention of this robot be of great interest? One of the great benefits of the coral reef is that in case of natural hazards, such as coastal storms, the reef on average can reduce the wave energies by 97% (Ferrario, 2014). Meaning that it can prevent storms and flooding and thus protect the coastal inhabitants. Since roughly 40% of the world’s population is located within a range of 100 km from the coast (Ferrario, 2014), protecting the coral reef will result in a reduction of a great amount of damage. This would not only be in regard to human lives but also to environmental destruction. In the case of these natural hazards, it is the government that will be imputable for the caused devastation. This is why they are the main users of a robot that helps recover the coral reef.

In order to prevent further downgrading and instead increase the growth of the reef, large biodiversity of animals is required. It is therefore important that the robot can navigate through the water to guide the fish towards the reef. For this, the robot should firstly be able to detect where fish should be guided and then maneuver in the ocean without damaging any of the already existing reefs. Establishing which parts of the reef need to be tackled can be done by scanning the reef by means of taking pictures and comparing them to a database full of images of coral reef. A camera that operates well underwater is, therefore, a must. This camera will also be used in combination with a filter to navigate the robot in the water.

Since fish can be tricked in believing the coral is still alive through sounds of different frequencies, the robot will have to be capable of creating these sounds underwater. To achieve this, an underwater sound system is needing to be implemented inside the robot. Research done by Enger, Karlsen, Knudsen, and Sand (1993) shows that there is a wide range in frequency of what fish can hear. In this research, tests were done on different fish which resulted in hearing thresholds differing between the species. To know what frequency to send out at what moment, the robot will have to know what kind of fish are around and adjust its emitting sound. A database of the types of fish is needed to compare the with the camera detected fish.

Currently, the work that is needing to be done to make sure the coral reef is either still intact or regrowing, requires divers to go down in the ocean to explore and help out. Since the robot is going to replace these divers, they will have to be able to do exactly what the divers already can. This means that the robot should not solely be capable of helping the coral grow back, but also be able to communicate the current state of the ocean back to researchers. For this reason, underwater wireless communication should be possible.

For to robot to be moving around in the water and going fairly deep, it should contain a battery that can last long enough for the robot to go down explore the area and lure fish long enough to an area that they will migrate there. However, implementing a system inside the robot that will generate energy, would increase the robot's functionality. This way the robot can be used more effectively over greater distances.

Approach, Milestones and Deliverables

State of the art research needs to be done to see what is already done in the field of saving corals. Also, this will generate knowledge about and what can be improved on these designs so this project will be useful in this field. The needs of corals and people will also become clear when doing user research.

When there is found what is useful and needed to develop, an RPC list will be made to make clear what is wanted to accomplish. In this list requirements, preferences and constraints will be noted. This is useful for making designs that are wanted.

Multiple design strategies will be considered and one will be chosen. A design concept is developed keeping the goal and RPCs of the project in mind. Choices need to be made about what techniques will be used to help the corals, in which way the robot is going to move and how the robots will communicate as a system. Also hardware for the robot and a way to model the system needs to be chosen.

The design concept will then be executed into deliverables. The deliverables for this project are:

• A model of the way the system works
• A detailed sketch of the robots itself
• The semi-functional prototype of the robot
• An additional report or Wiki for the explanation of the concept

Also, a conclusion needs to be drawn from this project. For this, also recommendations for further research needs to be made. The robot/prototype needs to be demoed. After that, the robot and the model need to be evaluated.

Before reaching the final goal of this project, some milestones need to be passed.

• State of the art research is done
• RPC list is made
• The design concept is decided on
• Model and prototype are made
• Demo and evaluation are done

References

Gordon, T. A. C., Radford, A. N., Davidson, I. K., Barnes, K., Mccloskey, K., Nedelec, S. L., … Simpson, S. D. (2019). Acoustic enrichment can enhance fish community development on degraded coral reef habitat. Nature Communications, 10(1). doi: 10.1038/s41467-019-13186-2

Ferrario, F., Beck, M. W., Storlazzi, C. D., Micheli, F., Shepard, C. C., & Airoldi, L. (2014). The effectiveness of coral reefs for coastal hazard risk reduction and adaptation. Nature Communications, 5(1). https://doi.org/10.1038/ncomms4794

Enger, P. S., Karlsen, H. E., Knudsen, F. R., & Sand, O. (1993). Detection and reaction of fish to infrasound. ICES mar. Sei. Symp., 196, 108–112. Retrieved from https://pdfs.semanticscholar.org/7491/2a618da033b24796f48e88e71eaa00a9b57d.pdf