Marine organisms are one of the oldest and most diverse forms of life on Earth, forming complex and sophisticated ecosystems in the vast marine environment. However, with the development of human society, nuclear pollution has emerged as a severe global environmental issue, impacting not only terrestrial ecosystems but also posing a profound threat to the health of marine ecosystems. Nuclear pollution primarily refers to the environmental damage caused by the residues of nuclear substances, including pollution caused by nuclear radiation, atomic dust, and secondary pollution resulting from the impact of these substances on the environment, such as harm to humans and animals from water sources contaminated with nuclear substances. The issues of nuclear pollution stem from various factors, including the development of nuclear energy, nuclear weapons testing, nuclear accidents, and the disposal of nuclear waste, all of which contribute to the release and accumulation of radioactive substances in the marine environment. Consequently, marine ecosystems are exposed to the threats posed by various radioactive isotopes, including radioactive iodine, strontium, plutonium, etc. (Fereshteh et al., 2021), which can elicit a wide range of physiological responses in marine organisms.

The physiological responses of marine organisms to nuclear pollution constitute a complex research field, involving various levels such as biochemical processes, gene expression regulation, metabolism, and adaptive mechanisms within organisms (Cui, 2018). The significant impact of nuclear pollution on marine ecosystems has led to numerous environmental problems, with the most severe being genetic damage to marine organisms. Radiation can alter the genetic material of marine organisms, leading to genetic mutations and other harmful effects. These mutations can be passed down through generations, resulting in long-term genetic damage to marine populations.

Therefore, the purpose of this study is to delve into how marine organisms generate physiological responses when faced with nuclear pollution and how these physiological responses affect the structure and function of marine ecosystems. In addition, the study discusses the sources and types of nuclear pollution, the basic structure of marine ecosystems, and the physiological response mechanisms of marine organisms as crucial components of ecosystems. Attention is also given to factors influencing the ecological effects of nuclear pollution, including the properties and concentration of radioactive substances, pollution sources and emission pathways, as well as ecosystem factors. This research aims to raise awareness of the issue of nuclear pollution, promote further research and collaboration, and ensure that marine ecosystems can continue to provide essential ecological services for humanity while preserving the beautiful and diverse world of marine organisms for future generations.

1 Sources and Types of Nuclear Pollution

Nuclear pollution originates from two main channels: natural nuclear radiation and anthropogenic nuclear pollution. Natural nuclear radiation is is a type of nuclear radiation commonly present on Earth and includes radiation from radioactive isotopes in the Earth's crust, such as radioactive potassium and radioactive carbon. On the other hand, anthropogenic nuclear pollution stems from human activities, including nuclear energy development, nuclear weapons testing, nuclear accidents, and nuclear waste disposal. Nuclear pollution encompasses various types, involving different radioactive isotopes and isotopes. Uranium, plutonium, strontium, iodine, and radon are major representatives of nuclides in nuclear pollution, each possessing distinct chemical properties and radioactive characteristics. Consequently, marine organisms exhibit diverse physiological responses to these nuclides, and the control and protection of marine ecosystems from nuclear pollution require a comprehensive consideration of these sources and types of nuclides.

1.1 Natural nuclear radiation and anthropogenic nuclear pollution

Natural nuclear radiation and anthropogenic nuclear pollution represent the two primary sources of nuclear pollution, playing crucial roles in its formation and impact. Natural nuclear radiation is inherent to Earth and originates from radioactive isotopes naturally present in the environment. These radioactive isotopes can be categorized into two types: natural isotopes and cosmic rays. Natural isotopes, such as radioactive potassium and radioactive carbon, etc., which exist in the Earth's crust, naturally distributed in crustal rocks, soil, and sediments, ultimately entering the oceans. On the other hand, cosmic rays consist of high-energy particle radiation from outer space, interacting with molecules in the atmosphere to generate radioactive isotopes (carbon-14), which then enter the oceans (Li, 2023). The presence of these natural nuclear radiations in marine ecosystems is inevitable and typically exists in low concentrations, resulting in relatively minor physiological responses in most marine organisms.

Artificial nuclear pollution originates from human activities, including nuclear energy development, nuclear weapons testing, nuclear accidents, and nuclear waste disposal (Figure 1). These activities have led to the release of a large amount of radioactive materials into the marine environment, posing severe threats to marine ecosystems. Nuclear power plants represent a significant source of anthropogenic nuclear pollution, which may lead to radioactive substances such as uranium and plutonium into the oceans. Nuclear weapons testing releases large quantities of radioactive isotopes being released into the atmosphere, subsequently depositing through precipitation into the oceans, exerting irreversible impacts on ecosystems. Nuclear accidents, such as the Chernobyl nuclear power plant disaster and the Fukushima nuclear disaster, can lead to extensive nuclear pollution, causing large-scale release of radioactive isotopes and seriously affecting surrounding marine ecosystems, jeopardizing the survival and health of marine organisms. Additionally, nuclear waste disposal may result in the leakage and release of radioactive isotopes into the oceans. The characteristic feature of anthropogenic nuclear pollution is that it often leads to a significant increase in the concentration of radioactive substances, thereby posing greater ecological risks to marine organisms. Different types of radioactive isotopes vary in their sources and properties, consequently eliciting different physiological responses in marine organisms.

Figure 1 Deep hole processing of nuclear waste

1.2 Types and sources of radioactive substances

Understanding the different types of radioactive isotopes and their sources is crucial for the effective management and mitigation of ecological risks associated with nuclear pollution. This understanding assists researchers and policymakers in better assessing and addressing the impact of nuclear pollution on marine ecosystems.

The types and sources of radioactive substances are integral components of nuclear pollution. In the context of nuclear pollution, different types of radioactive isotopes vary in their sources and properties, resulting in distinct impacts on marine ecosystems and organisms. Some of the main radioactive isotopes include uranium, plutonium, strontium, iodine, and radon. Uranium is a common radioactive element that is widely present in the Earth's crust and it may be released into the oceans during accidents at nuclear facilities or nuclear weapons testing (Fadhil, 2023). Plutonium, often used in nuclear weapons manufacturing, is a highly radioactive element that may be released in significant quantities into the oceans through nuclear weapons testing and nuclear waste disposal. Strontium, a radioactive element, has a common radioactive isotope known as strontium-90, which may be released during nuclear facility accidents and nuclear weapons testing. Iodine, particularly the radioactive isotope iodine-131, is a common byproduct of nuclear facility accidents and should not be underestimated in nuclear pollution. Radon, a naturally occurring radioactive element primarily from the Earth's crust, may enter the oceans through groundwater. In addition, tritium is an isotope of hydrogen, widely used in nuclear power facilities and may be released into the ocean through nuclear power facility accidents or radioactive waste.

These radioactive isotopes primarily originate from human activities such as nuclear energy development, nuclear weapons testing, nuclear accidents, and nuclear waste disposal. Leaks or accidents at nuclear power plants can result in the release of radioactive substances into the oceans, posing a threat to the survival of marine organisms. Improper nuclear waste disposal may also lead to the leakage and release of radioactive isotopes.

1.3 Ocean distribution and dispersion of nuclear pollution

The distribution and spread of nuclear pollution in the ocean constitute a complex process influenced by various factors, including the types and properties of radioactive substances, release sources, oceanic water currents and depths, and the biologically availability of nuclides. Once radioactive isotopes enter the ocean, they will settle, diffuse, and transport within the water column at different rates.

The sources of nuclear pollution can be categorized into natural sources and anthropogenic sources. Natural sources include radioactive isotopes in the Earth's crust and cosmic rays, resulting in low levels of natural nuclear radiation (Amjed et al., 2023). However, anthropogenic sources, such as nuclear energy development, nuclear weapons testing, nuclear accidents, and nuclear waste disposal, lead to significant releases of radioactive isotopes, significantly elevating the degree of nuclear pollution in the oceans. Oceanic water currents and depths play a crucial role in the distribution and spread of nuclear pollution. Surface waters are often directly influenced by atmospheric transport of nuclides, while deep waters may take longer to be affected by atmospheric transport of nuclides. The distribution of nuclides in the water column in different ways often leads to uneven vertical and horizontal distribution of radioactive nuclides in the water column.

The biological availability of radioactive isotopes is another critical factor. Different tissues of organisms exhibit varying rates of absorption and accumulation of nuclides, resulting in a complex process of transfer and accumulation of nuclear pollution in the food chain, ultimately affecting different levels of marine organisms (Figure 2).

Figure 2 Radioisotope leakage causes massive death of marine organisms

The ecological effects of nuclear pollution on marine organisms also depend on the structure and biodiversity of the marine ecosystem. Certain organisms may exhibit higher tolerance to nuclear pollution, while others may be more susceptible to its impact. Interactions within the ecosystem and ecological niches also influence the ways in which nuclear pollution is propagated. In summary, the distribution and spread of nuclear pollution in the ocean are complex processes involving multiple interactive factors, including the sources of radioactive substances, characteristics of oceanic water bodies, behaviors of organisms, and the dynamics of the food chain.

2 Physiological Response Mechanisms of Marine Organisms to Nuclear Pollution

The physiological response mechanisms of marine organisms to nuclear pollution constitute a complex process that depends on multiple factors. Nuclear pollution can have widespread effects on marine organisms and ecosystems. Some common physiological response mechanisms include DNA damage repair, antioxidant defense mechanisms, metabolic adaptations, reproductive and developmental damage, as well as changes in behavior and life history strategies (Figure 3).

Figure 3 Biological cell damage

2.1 DNA and cellular damage caused by nuclear pollution

DNA and cellular damage caused by nuclear pollution in marine organisms have widespread effects on their survival and reproduction. Radioactive isotopes such as uranium, strontium, iodine, and radon, when released into the ocean, interact directly or indirectly with cells and DNA through their radioactive radiation, leading to DNA and cellular damage. Direct DNA damage includes DNA strand breaks, base damage, and cross-linking between DNA strands. These damages may result in the incomplete DNA molecules and mutations in genetic information, posing a severe threat to the normal functioning of cells. Furthermore, radioactive radiation may lead to the accumulation of DNA damage, exerting long-term effects on the genetic material within cells.

Indirect DNA damage involves free radicals or oxidative stress induced by radioactive isotopes. These free radicals can trigger oxidative damage, including oxidative damage, phosphodiesters, and DNA strand breaks. Oxidative damage poses a serious threat to the integrity and stability of cellular DNA, thereby affecting the normal functioning of cells. Cellular damage not only includes DNA damage caused by nuclear radiation but also involves other essential components within cells. Damage to mitochondria may hinder cellular energy production, affecting cellular metabolism (Pei et al., 2023). Damage to the cell membrane may disrupt the balance between the internal and external environment, thereby interfering with cell function. These cellular damages not only threaten the health of individuals but may also lead to damage at the tissue and organ levels.

DNA and cellular damage caused by nuclear pollution in marine organisms may result in genetic mutations, cell death, cellular dysfunction, and metabolic abnormalities. These effects may ultimately lead to a reduction in marine organism populations, ecosystem imbalance, and a decrease in biodiversity. In order to maintain the health and stability of marine ecosystems, as well as reduce the ecological risks of nuclear pollution, scientists and policymakers need to gain a deeper understanding of the DNA and cellular damage caused by nuclear pollution and its physiological response mechanisms. This will aid in implementing measures to reduce the sources of nuclear pollution and implementing appropriate protection and management measures to safeguard marine organisms from harm.

2.2 Regulation of gene expression and protein synthesis in marine organisms exposed to nuclear pollution

Nuclear pollution has profound effects on the gene expression and protein synthesis of marine organisms. These effects are realized through various complex molecular mechanisms, encompassing multiple levels such as the regulation of gene expression and protein synthesis (Chen, 2021). The radiation energy released by radioactive isotopes in nuclear pollution directly interacts with the DNA molecules of living organisms, causing DNA damage. This includes DNA strand breaks, base damage, and cross-linking between DNA strands. These damages not only affect the integrity of DNA but may also trigger intracellular DNA repair mechanisms, leading to upregulation of gene expression related to DNA repair.

Furthermore, radioactive radiation induced by nuclear pollution triggers oxidative stress reactions, generating reactive oxygen species and other oxidizing substances. This may influence the expression of genes related to oxidative stress within cells, such as antioxidant enzymes and genes involved in clearing reactive oxygen species. The regulation of the expression of these genes is crucial for maintaining oxidative balance within cells, but it may be disrupted under nuclear pollution conditions. Nuclear pollution may impact the expression of genes involved in cell cycle regulation, affecting cell division and proliferation. These effects can lead to changes in cell growth limitation, differentiation, and proliferation. Cell cycle regulation is a crucial aspect of gene expression, and changes in gene expression associated with nuclear pollution may have widespread effects on cell function and characteristics.

In terms of protein synthesis regulation, nuclear pollution also influences the translation process. This includes affecting the translation rate and protein levels by modulating the activity of translation factors or altering the structure of RNA molecules. Translation is a key step in protein synthesis, and changes in translation regulation induced by nuclear pollution may result in alterations in the synthesis levels of proteins. Nuclear pollution may also affect post-translational modifications of proteins. This includes modifications such as phosphorylation, methylation, and acetylation, which can alter the function and stability of proteins. Nuclear pollution may lead to changes in the synthesis and modification of specific proteins, thereby affecting protein function.

2.3 Impact of nuclear pollution on adaptation and resistance mechanisms in marine organisms

The adaptation and resistance mechanisms of marine organisms to nuclear pollution have a significant impact. This impact is realized through various complex molecular mechanisms, covering multiple levels such as the regulation of gene expression, DNA repair, antioxidant defense, protein modification, and cell survival strategies. DNA damage triggered by nuclear pollution is a crucial starting point. Subsequently, oxidative stress induced by nuclear pollution is a common physiological response. Moreover, nuclear pollution may alter the synthesis and modification of specific proteins, regulate changes in cell division and proliferation, and some marine organisms eliminate damaged cells by promoting apoptosis and autophagy to prevent the continued existence of damaged cells (Li et al., 2023). Marine organisms exposed to nuclear pollution for an extended period may accumulate beneficial genetic variations through genetic adaptation. These adaptive genotypes can enhance the organism's resistance, enabling it to better adapt to the environment affected by nuclear pollution.

The various complex adaptation and resistance mechanisms triggered by nuclear pollution involve multiple biological aspects such as gene expression regulation, antioxidant defense, protein modification, cell cycle regulation, apoptosis, and autophagy, among other biological levels. These mechanisms enable marine organisms to survive in environments affected by nuclear pollution, mitigate damage, and maintain their viability. However, detailed research on these mechanisms is still ongoing.

Studies on the physiological response of different types of marine organisms to nuclear pollution demonstrate diversity. Research indicates that bivalves such as oysters and clams exhibit strong resistance mechanisms to nuclear pollution. These organisms can reduce the uptake of radioactive isotopes by accumulating heavy metal ions, thereby minimizing the impact of nuclear pollution. Oysters in nuclear pollution environments show enhanced antioxidant defense systems to neutralize reactive oxygen species and alleviate oxidative stress. Some algae species demonstrate adaptability in nuclear pollution environments. For example, after the Fukushima nuclear accident, certain algae species exhibited increased growth rates and photosynthetic rates, considered adaptive responses to nuclear pollution, possibly associated with oxidative stress and DNA damage induced by nuclear pollution.

3 Factors Influencing Nuclear Pollution

Nuclear pollution is a complex issue influenced by a combination of various factors, categorized into natural factors, human factors, and ecosystem factors. Together, these factors shape the complexity and diversity of nuclear pollution.In terms of natural factors, geological features significantly impact the pathways of nuclear pollution spread. Geological characteristics such as groundwater levels, soil types, and underground flow paths determine the distribution of radioactive isotopes in groundwater and soil. Weather and meteorological conditions, including wind direction, wind speed, precipitation, and atmospheric pressure, directly influence the dispersion pathways and speed of nuclear pollutants in the atmosphere (Gu, 2021) (Figure 4). Additionally, natural Earth radiation interacts with nuclear pollution, contributing to increased environmental nuclear radiation.

Figure 4 Schematic diagram of nuclear pollution affected by wind direction

Human activities contribute significantly to nuclear pollution, with major sources including nuclear facilities, nuclear waste management, nuclear weapons usage, and nuclear waste disposal. Unsafe management of nuclear facilities, accidents, or leaks can lead to the release of radioactive substances, exemplified by the Chernobyl nuclear accident (Figure 5). The use of nuclear weapons and nuclear explosions generates a large amount of nuclear radiation and pollution, causing long-term effects on the global environment, as observed in the nuclear explosions in Hiroshima and Nagasaki. Improper disposal and storage of nuclear waste also constitute significant contributors to nuclear pollution, illustrated by facilities such as the Hanford Nuclear Waste Storage Site in the United States.

Figure 5 Chernobyl Fukushima nuclear waste discharge

Ecological factors encompass ecosystem types, biological accumulation and ecological chain transmission, as well as the restorative capacity of ecosystems. Different types of ecosystems exhibit varying responses to nuclear pollution; wetlands and coastal ecosystems may be more adept at absorbing and storing nuclear pollutants (Li et al., 2022), while forests and mountain ecosystems may have distinct diffusion patterns in the nuclear pollution process. Organisms within ecosystems absorb and accumulate nuclear pollutants, transferring them up the food chain, resulting in cascading effects. The resilience of ecosystems plays a potential role in addressing nuclear pollution, with some ecosystems possessing inherent self-repairing potential.

4 Summary and Outlook

Research on nuclear pollution contributes to revealing the accumulation and enrichment processes of radioactive substances in the environment on organisms. This helps researchers better understand which marine organisms are more susceptible to nuclear pollution and how they transfer nuclear pollutants into the food chain, ultimately affecting human food safety. Understanding the physiological responses of marine organisms is more helpful in predicting the long-term effects of nuclear pollution, including potential threats to biodiversity, ecosystem health, and the entire marine ecosystem.

This review systematically explores the physiological responses of marine organisms to nuclear pollution, emphasizing the analysis of the sources and types of nuclear pollution, the physiological response mechanisms of marine organisms, and the various factors influencing nuclear pollution. As a serious global environmental issue, nuclear pollution has profound effects on marine organisms and the entire ecosystem. In-depth research into the effects of nuclear pollution on marine organisms enhances our understanding of marine ecosystems.

Future research directions should delve deeper into nuclear pollution to comprehensively understand its additional impacts. Firstly, research should focus on biodiversity in different ecosystems, gaining insights into the adaptability and resistance mechanisms of different species, habitats, and ecosystems to nuclear pollution. Long-term monitoring and trend analysis are necessary to understand the evolution process of nuclear pollution and the long-term recovery capacity of ecosystems. Ecological risk assessment is also a crucial future research direction, enabling researchers to delve into the potential threats of nuclear pollution to ecosystem health and biodiversity, in order to mitigate the adverse impacts of nuclear pollution (Davis and Conroy, 2018). Interdisciplinary collaboration will continue to be crucial in future research, combining expertise from various fields to comprehensively understand the multi-faceted nature of the nuclear pollution issue. This will promote comprehensive research approaches that facilitate addressing the complexity of nuclear pollution problems.

These research directions will contribute to deepening our understanding of nuclear pollution issues, providing a more comprehensive scientific basis for the effective management and environmental protection of nuclear pollution. Protecting marine life and maintaining ecological balance are common responsibilities of humanity, and through ongoing research and collaboration, we can better achieve this goal.

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