The Impacts and Crises on Coral Reef Posed by Various Factor

Zhengqi Wang

Yushan Campus, Ocean University of China, Badaguan Road, Shinan District, Qingdao City, Shandong Province, China

Keywords: Coral Reef, Symbiotic Bacteria, Dissolved Organic Matter, Cryostorage, Microplastics.

Abstract: Since the late 20th century, the proliferation of industry and technology, alongside various biological factors,

has led to a progressive decline in the quantity of wild coral reefs within the oceans. The survival of coral

reefs and the equilibrium of coral reef ecosystems are under severe threat. The paper primarily outlines the

potential threats faced by coral reefs, the impact of human pollution on coral reefs, and the development of

novel technologies that offer new directions for the conservation of coral reefs and their ecosystems. This

study reveals that with the advancement of biotechnology, certain sponge symbiotic bacteria and dissolved

organic matter play crucial roles in maintaining the stability of coral reefs. Emerging cell engineering

techniques, such as cryopreservation, indicate a pathway for enhancing coral polyp biomass. Increasing

biomass is an innovative measure, yet it requires careful consideration of various tradeoffs to avoid

exacerbating adverse impacts. Simultaneously, bioremediation techniques offer potential for degrading

microplastics in the ocean and stabilizing aquatic environments.

1 INTRODUCTION

Coral reefs refer to underwater structures found in

tropical and subtropical shallow seas, consisting of

the skeletal remains of reef-building corals and

biological debris, possessing wave-resistant

characteristics. Within coral reefs, various reef-

building organisms such as corals of the order

Scleractinia, hydrozoans, and algae are encompassed.

Oman's territory encompasses more than 530 square

kilo-meters of coral reefs along one of the Arabian

Peninsula's longest coastlines, fostering the survival

of over 100 coral species and 579 species of coral

fish. Despite the unique biogeographical background

and evident significance for biodiversity and

economy, Oman's coral reef ecosystems are

recognized as being among the least researched in the

region. Since the late 20th century, these reefs have

faced threats from various biotic and abiotic factors,

including the adverse impacts of human activities

(Burt et al., 2016). Hurricanes have led to extensive

loss of shallow-water coral across the entire

Daymaniyat Archipelago. Particularly affected are

the coral communities dominated by branching

Acroporidae and Pocilloporids, where the

fragmentation of these coral colonies has resulted in

significant losses of coral cover and structural

heterogeneity.

Scholars from various fields both domestically

and internationally show significant concern for the

conservation of coral reefs and biodiversity.

Researchers conducted genetic analyses on 47 coral

reef species sampled across multiple islands in

Hawaii (Selkoe et al., 2016 & Voolstra et al., 2023).

The findings of the research highlighted the

fundamental connection between ecology and

genetics, paving the way for novel approaches to

monitor and conserve the biodiversity of coral reef

ecosystems. Additionally, advancements in cellular

engineering have made significant contributions to

the breeding and conservation of coral polyps,

playing a crucial role in enhancing the biomass of

coral reef ecosystems. Simultaneously, the

International Coral Reef Symposium (ICRS) has

proposed several feasible measures for coral reef

conservation, such as reducing carbon dioxide

emissions, enhancing pollution monitoring and

improving water quality.

This paper elucidates the pivotal role of coral reef

ecosystems in the marine environment, as well as the

diverse array of global factors impacting and

threatening these ecosystems. Such phenomena have

garnered extensive attention and research interest

among scholars. Some researchers are employing

biochemical approaches to enhance the biomass of

coral reefs, including investigating the roles of

symbiotic bacteria and dissolved organic matter in the

Wang, Z.

The Impacts and Crises on Coral Reef Posed by Various Factor.

DOI: 10.5220/0013844000004914

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 2nd International Conference on Renewable Energy and Ecosystem (ICREE 2024), pages 29-34

ISBN: 978-989-758-776-4

stability and protection of coral reefs (Marzuki et al.,

2023 & Nelson et al., 2023). With the development of

cellular engineering, the cultivation of coral larvae

offers a novel approach to enhancing the biodiversity

of coral reefs (Hagedorn et al., 2017). However, due

to the extensive distribution of coral reefs, some

measures are difficult to be implemented on a large

scale. There is still a long way to go for the protection

of coral reefs and biodiversity.

2 CASE DESCRIPTION

From the 1970s onwards, Omani coral reefs have

experienced ongoing disruptions caused by repeated

outbreaks of the predatory crown-of-thorns starfish.

These outbreaks typically occur at least once every

decade, leading to rapid changes in the structure of

coral communities. At the same time, the extensive

damage to Oman's coral reefs was also inflicted by

Hurricane Gonu in 2007. The entire Omani sea

witnessed significant impact from this cyclone,

causing widespread destruction to coral formations

(Burt et al., 2016). Furthermore, the substantial

amount of marine debris generated by industrial

production emissions poses a serious threat to the

survival of marine species. As a result, coral reef

ecosystems are highly susceptible to various natural

and anthropogenic disturbances, posing significant

threats to the survival of corals. Urgent measures are

imperative for the conservation of coral reef

ecosystems.

3 FACTORS AFFECTING CORAL

REEF ECOSYSTEMS AND

POSSIBLE MEASURES TO

PROTECT CORAL REEFS AND

BIODIVERSITY

Coral reef communities exhibit high biodiversity and

productivity, with some individual animal species

displaying remarkable characteristics. Coral reefs

provide habitat for a myriad of marine organisms,

including annelids, mollusks, sponges, echinoderms,

and crustaceans, among others. Many species have

developed symbiotic relationships with corals, such

as zooxanthellae, which utilize the metabolic waste

and carbon dioxide from coral polyps to undergo

photosynthesis and produce organic matter. These

compounds exist in the form of glycerol and glycerol

triesters, which are secreted into the extracellular

matrix to provide nutrition for coral polyps and are

readily absorbed by them. Today, due to industrial

pollution emissions and human activities in the

oceans, coral reefs experienced a serious global

decrease in their coverage area. Consequently, the

populations of some species dependent on coral reefs

for survival have decreased. Finding effective

measures to protect coral reef ecosystems has become

a focal point of research in this field. Maintaining

biomass, diversity, and ecosystem functionality is a

core objective of most initiatives aimed at protecting

coral reef ecosystems.

Some human activities like certain fishing

practices and construction projects, indirectly

induced climate change, can lead to coral loss,

resulting in declines in coral fish biomass and

changes in coral reef community structure.

Undoubtedly, this disrupts the balance of coral reef

ecosystems. Research indicates that global warming

will directly impact coral reef fish communities

through rising sea temperatures or ocean

acidification, or indirectly through habitat loss. The

coral reefs of Lizard Island, which is part of the Great

Barrier Reef in Queensland, have suffered greatly as

a result of terrible weather events. In 2014, The

northwestern region's shallow reefs suffered

significant damage from Hurricane Ita & Cyclone

Nathan in the previous year, which caused the coral

coverage to drop significantly from twenty-five

percent to nine percent. Numerous coral reefs have

seen the destruction of their branching corals, which

has led to the habitat loss of numerous coral fish

species (Triki et al., 2018). Some scholars have

pointed out that increasing the biomass of coral fish

could help maintain the diversity of coral reef

ecosystems. However, this approach does not

fundamentally address the issues of expanding coral

reef areas or mitigating coral bleaching.

On the other hand, need for industrial output is

rising in tandem with the global population growth,

leading to the construction of numerous new factories

along coastlines. This has directly resulted in a

significant discharge of production waste and

pollutants into the sea, including a substantial amount

of heavy metal contaminants. Using 14 samples of

planktonic species, researchers measured the amounts

of 19 common elements using Inductively ICP-OES,

covering the oligotrophic and mesotrophic zones

found in the Red Sea's northern and southern sections.

The findings showed that samples from Rabigh City's

southwest had noticeably higher amounts of Cr, Ni,

Pb, and Zn, which may have something to do with the

region's use of crude oil and related activities. These

elevated concentrations could be the result of the

ICREE 2024 - International Conference on Renewable Energy and Ecosystem

region's pollution-intensive sectors, like power plants

that use crude oil as fuel to generate electricity (Cai et

al., 2022). Various indicators suggest that human

industrial production is discharging a significant

amount of pollutant waste into the ocean.

Furthermore, it is worth noting that due to the unique

physical properties of heavy metals, they tend to

readily deposit in seabed sediments and are difficult

to degrade. This could result in heavy metals

remaining deposited in marine environments for

decades or even centuries, significantly impacting

nutrient absorption by coral reefs and potentially

indirectly leading to species mortality. Besides,

researchers also investigated the influence of

monsoons and ocean currents on the distribution of

heavy metals. The results indicate a close correlation

between the fluctuation of heavy metals and seasonal

variations: zinc (Zn) exhibits its highest concentration

in the western monsoon, while lead Pb content is

highest in the eastern monsoon (Raza'I et al., 2021).

This suggests that heavy metals can spread worldwide

with monsoons and ocean currents, indicating their

impact is inevitably global, posing a serious threat to

the entire coral reef ecosystem.

Research has indicated that certain cleaner fish

species can promote the diversity of coral reef fish.

Among coral reef fish, interactions with cleaner fish

represent one of the most prevalent interspecific

relationships. Each day on the Great Barrier Reef, an

average of 2297 client fish engage in interactions with

the cleaner fish species Labroides dimidiatus. Certain

client species individuals visit cleaner fish species up

to an average of 144 times per day. Researchers

discovered that on coral reefs containing cleaner fish

species, both the number of visiting client fish species

and that of individual visitors were approximately

double and quadruple, respectively, in comparison to

reefs lacking cleaner fish. This directly enhances the

biodiversity of coral reef ecosystems (Grutter et al.,

2003).

Governments propose establishing marine

protected areas to maintain the balance of coral reef

ecosystems. Indeed, this is one of the primary

conservation strategies for coral reefs. However,

marine protected areas alone cannot mitigate the

widespread impacts of climate change on coral reefs.

In the ENSO event of 2014–2016, coral reefs in the

vicinity of Zanzibar experienced coral bleaching,

leading to significant coral mortality.

Simultaneously, coral bleaching has resulted in a

series of adverse effects on the benthic community

structure of coral reefs and some omnivorous animal

populations. The coral mortality rate across all coral

reef locations reached as high as 68%, with a

concurrent increase in turf algae cover by 48%.

Human efforts to predict climate impacts or propose

mitigation measures remain challenging (Elma et al.,

2023).

In recent years, many studies have pinpointed

fresh avenues for safeguarding and preserving the

equilibrium of coral reef habitats. Research indicated

the potential applications of high-performance and

effective marine sponge-associated bacteria for the

elimination of heavy metal contaminants and PAHs.

Several types of marine sponge-associated bacteria

may be utilized to enhance waste remediation

capabilities. These marine sponges typically inhabit

coral reef communities, and the bacteria's capacity for

removing and absorbing certain heavy metal

pollutants holds potential advantageous effects for

improving the survival environment of coral reefs.

Studies have shown that when sponge habitats are

exposed to toxic metals or hydrocarbons pollution,

either separately or together, enhances the bacteria-

sponge symbiotic model. As sponges adjust to live in

the harsh conditions of their surroundings, this

happens. Meanwhile, these circumstances are also

used by symbiotic bacteria to create mucus. By acting

as an enzyme and spreading across the sponge's

surface, the mucous material lessens the effects of

harmful contaminants (Marzuki et al., 2023). Further

research indicates that the process of bacteria

adsorbing heavy metals is analogous to the formation

of X-EDTA complexes, where X represents the heavy

metal, using ethylenediaminetetraacetic acid

(EDTA). Extracellular ionic bonds are formed during

the heavy metals adsorption procedure, linking the

negatively charged bacterial cell surface with

similarly charged heavy metals. The adsorption time

of heavy metallic ions is less than that of polycyclic

aromatic hydrocarbons breaking down. The process

of adsorption keeps going until it reaches saturation.

SEM, EDS, and XRD analytical instruments can be

employed to observe the adsorption mechanisms and

alterations of bacterial cells regarding heavy metals.

Meanwhile, AAS or ICP techniques can be utilized to

determine the adsorption efficiency. By quantifying

the adsorption capacity of marine bacteria for heavy

metal pollutants, a new direction has been identified

for improving the marine environment conducive to

coral reef survival.

As scientific inquiry advances, researchers have

unearthed the pivotal role of specific marine

microorganisms in upholding the durability and

steadiness of coral reefs by facilitating the

transformation and recycling of dissolved organic

matter. Dissolved organic matter refers to organic

substances that can pass through a 0.5+ micron filter.

The Impacts and Crises on Coral Reef Posed by Various Factor

Dissolved organic matter permeates the world's

oceans and boasts a biomass comparable to that of

terrestrial plants. These organic substances play a

crucial role as mediators in coral reef production,

nutrient exchange, and biological interactions,

whereas the conversion and recycling of organic

matter is greatly aided by microbes. In maritime

contexts, coral reefs display five fundamental

ecological processes: increased productivity, rapid,

diversified biogeochemical cycle, high biodiversity,

intensive decomposition, and high adsorption.

Microbial interactions with dissolved organic matter

are central to each of these processes. Initially,

microorganisms recycle dissolved primary products,

with coral reef microbial communities swiftly

utilizing and transforming these compounds. This

dynamic mechanism plays a key role in the

transmission of coral reef higher trophic levels with

carbon by influencing the structure of microbial

communities. Additionally, it enhances nutrient

utilization and retention; in oligotrophic tropical

waters, microbiological remineralization of dissolved

organic compounds provides a major nutrient source

that allows the main producers in coral reef

ecosystems to survive. Furthermore, microorganisms

aid in the rapid decomposition of detrital

accumulation, and the broader nutritional interactions

between microorganisms and DOM play a crucial

role in maintaining a net metabolic balance and

minimizing detrital accumulation. Finally, coral reef

net accretion is facilitated by microbial development

and metabolism, which also affect ecosystem net

calcification through indirect as well as direct

processes. These mechanisms include the use of

heterotrophic feeding to stimulate coral development,

microbial precipitation to aid in the calcification of

aragonite, and microbial remineralization of

substances that affect the concentrations of carbonate

ions and alkalinity in the area. This fosters the

formation of reef-building microorganisms. In

summary, many key factors that sustain coral reefs in

oligotrophic oceans are to some extent facilitated by

microbial-DOM interactions. These mechanisms

encompass the transmission of nutrients from DOM

to seafloor suspension-feeding groups, the

remineralization and transformation of nutrients, the

facilitation of diverse biogeochemical cycling, the

regulation of dissolved metabolism, and the

promotion of highly interconnected trophic

structures. These are all core aspects contributing to

the high biodiversity of coral reefs (Nelson et al.,

2023).

With the developments in cellular and embryo

engineering technologies, cryopreservation has

emerged as a new possibility for increasing the

biomass of coral polyps. Cryopreservation refers to

the process of suspending in vitro cultures in a

solution containing cryoprotectants, lowering them to

a certain subzero temperature at a controlled freezing

rate, and maintaining them at this temperature for

long-term storage. Researchers have now

successfully cryopreserved many types of coral cell

cultures, and coral eggs have been fertilized and coral

larvae have been produced using these frozen

materials (Hagedom et al., 2017). In laboratory

settings, researchers have successfully produced

significant numbers of coral offspring from

cryopreserved coral sperm (Hagedom et al., 2017),

making significant contributions to increasing coral

biomass in marine environments. However, it is

worth noting that the use of cryopreservation to

increase and sustain coral biomass has not seen

widespread development and production on a large

scale. Much work is still needed to make these

cryopreserved biological repositories viable partners

in coral reef restoration efforts.

4 BIOLOGICAL AND MATERIAL

SOLUTIONS

Protecting coral reefs from the perspective of

increasing biomass is an innovative and challenging

approach, but it is essential to ensure the balance of

the entire ecosystem and the food web within the food

chain. Increasing coral fish species diversity

indiscriminately may impact the survival of other

creatures (Schiettekatte et al., 2022). Research on

fishing activities in the Gulf of Saros in the

Mediterranean region has revealed that

overexploitation of resources in the bay extends to the

entire habitat, affecting low-nutrient levels and top

predators. In the late 1990s, overfishing led to a

decrease in biomass for the bluefin tuna populations

in the eastern Atlantic and Mediterranean, as well as

for the Mediterranean swordfish population. This

resulted in the proliferation of small to mid-sized

pelagic fish, significantly impacting the balance of

the marine ecosystem food web (Bradley et al., 2020

& Papantoniou et al., 2021). Hence, human

management of biomass requires multifaceted

considerations, as even minor disturbances can

potentially lead to ecosystem collapse or other

significant impacts (Papantoniou et al., 2021).

Conservative measures aimed at maintaining the

nutritional structure of ecosystems will become the

main trend in coral reef protection, ensuring the

ICREE 2024 - International Conference on Renewable Energy and Ecosystem

stability and enhancement of biodiversity within coral

reef ecosystems.

Due to inevitable pollution discharge into the

ocean in certain circumstances, apart from curtailing

emissions at the source, the development and research

of new degradation technologies are crucial for

mitigating the extent of coral reef exposure to marine

pollution. Some emerging ubiquitous environmental

pollutants, such as microplastics, ultrafine fibers and

nanoplastics, are extremely difficult to degrade in

marine environments. Due to their unique physical

properties, they easily accumulate in organisms and

can lead to organism mortality. Researchers are

exploring the possibility of using bioremediation

methods to mitigate marine microplastic pollution

(Das et al., 2023). The process of bioremediation

involves the utilization of organisms to reduce,

degrade, or eliminate pollutants from the

environment. Until now, researchers have discovered

bacterial strains, fungal species, and various plant

species that exhibit the ability to degrade, decompose,

or ingest microplastics, as evidenced by laboratory

experiments (Bradley et al., 2020). This provides a

promising direction for reducing emerging marine

pollutants. It is also believed to play a crucial role in

protecting and balancing coral reef ecosystems,

shielding them from the impacts of marine pollution.

5 CONCLUSION

Absolutely, among the ocean's most important marine

ecosystems, coral reef systems should get

international attention and protection. Indeed, with

the continuous advancement of technology and the

increasing demands of humanity on nature, the

survival environment and space for coral reefs are

increasingly concerning. Besides, adverse climate

changes such as global warming and El Niño events

also have negative impacts on the survival of coral

reefs. Scientists' exploration and research on various

aspects of coral reef ecosystems, including biology,

materials, environment, chemistry, etc., play a crucial

part in the preservation, expansion, and enhancement

of maritime habitats. The paper ’ s multifaceted

discussion on coral reefs aims to provide feasible

directions for coral reef conservation in the scientific

community and enhance the importance of marine

environmental protection. It seeks to mitigate the

threats facing coral reefs from various angles.

However, despite being a globally significant species,

the protection and propagation of coral reefs still face

several challenges. Certainly, challenges persist in

understanding the regulatory role of marine

microorganisms in aquatic ecosystems within the

scientific community. Additionally, the widespread

implementation of cryopreservation technology is

hindered by limitations in funding and technical

resources. Moreover, there are constraints on the

number of species capable of degrading

microplastics. With the support of advancing

technology, it is believed that the challenges related

to coral reef survival can be gradually addressed in

the near future. Not only that, the biodiversity within

coral reef ecosystems will steadily increase, leading

to a more stable balance between humans and nature.

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ICREE 2024 - International Conference on Renewable Energy and Ecosystem