Marine Organisms Research Articles

Acoustic Propagation and Transmission Loss Analysis in Shallow Water of Northern Arabian Sea

This study investigates acoustic propagation and transmission loss in shallow water at an unexplored site in the northern Arabian Sea near the Pakistan coastline using a normal mode theoretical framework. Sound propagation in shallow water with range-independent bathymetry was analyzed using a customized Kraken C program to compute eigenvalues and eigenfunctions. The sound speed profile and clay silt sediment samples of the northern Arabian Sea, which characterize the water column and ocean bottom, respectively, were determined. Coherent and incoherent transmission losses for frequencies ranging from 50 to 500 Hz were calculated across different ranges and depths. Results indicate significant intensity fluctuations with increasing range, leading to higher transmission loss. Low frequencies (50–225 Hz) exhibit more significant transmission loss, while higher frequencies (230–500 Hz) show reduced loss. Transmission loss is higher for receivers at 19 m depth compared to those at shallower depths (8 m and 12 m) because the receivers are positioned near the layer of bottom sediments. Factors such as source and receiver depth, sediment properties, bottom roughness, and sound frequency significantly influence transmission loss. The novel dataset for the region supports the assessment of sonar performance, underwater communication, navigation, and marine life exploration.

Nonunidirectional Habitat Changes Associated With Global Climate Change: The Example of the Indo‐Pacific King Mackerel (Scomberomorus guttatus) in the Taiwan Strait

ABSTRACTClimate change poses a significant threat to marine ecosystems, potentially altering the distribution of marine organisms and causing many species to migrate towards the poles. The habitat changes of species targeted for fishing are likely to affect fishing activities and the livelihoods of coastal communities. Hence, the present study analyzed the distribution of Indo‐Pacific king mackerel (IKM) in the Taiwan Strait (TS) by using ensemble modeling and considering two representative concentration pathway (RCP) scenarios (2.6 and 8.5) to assess the implications of predicted climate change. Four species distribution models incorporating sea surface height, chlorophyll, salinity, and temperature were used as inputs to create an ensemble model that replicated IKM distribution under current ocean conditions. The ensemble habitat model does not show monotonic decrease of IKM habitat but reveals more complex change in the 21st century with a hump around 2050. By end of the century, IKM is predicted to decline under RCP 8.5 scenario more seriously than under RCP 2.6. The study highlights the need for adaptation measures in managing IKM fisheries in the TS, emphasizing the importance of considering non‐unidirectional habitat changes in the global oceans as well.

Evaluating Climate Change Impacts to Qatar’s Marine Life: A Risk Assessment for SDG 14 (Life Below Water)

Marine life is integral to Qatar and the broader Arab region, serving as a cornerstone for biodiversity, economic activity, and cultural heritage. Despite the ambitious targets set by Sustainable Development Goal (SDG) 14, climate change is placing mounting pressure on conservation efforts. Recognizing that climate change cannot be entirely stopped, the focus should be on mitigating its effects through sustainable strategies. This study identifies twelve climate-related risks that impede Qatar's progress towards achieving SDG 14 - Life Below Water. To understand the region-specific climate risks, this study engaged in a focus group discussion with representatives from the government, NGOs, private sector, and academia. The Climate Change Risk Assessment (CCRA) identified the most severe risks as flooding associated with rising sea levels, modified species biogeography, and compromised coral reef health. While other risks were rated low, such as risks to seagrass meadows driven by increasing sea temperatures. Other significant findings include the need for increased awareness of climate change impacts on both the local and global administrative platforms. This risk assessment provides insights into the vulnerable facets of Qatar's marine environment, intending to guide forthcoming strategies for achieving SDG-14.

Plankton food web structure and productivity under ocean alkalinity enhancement.

Ocean alkalinity enhancement (OAE) is a nature-based technology for CO2 removal and storage, but little is known about its environmental safety. We tested a CO2-equilibrated OAE deployment in a close-to-natural community using in situ mesocosms in the oligotrophic subtropical North Atlantic and assessed metazoan zooplankton to inform about food web stability, structure, and production. In addition, a literature review complemented experimental results by summarizing physiological responses of marine animals to decreasing proton concentrations, or increased pH. The food web studied proved resistant, and zooplankton physiologically tolerant, to the OAE tested. We observed short-term effects of OAE on zooplankton reproduction and productivity, which were likely trophically mediated. Yet, these did not affect zooplankton populations or their nutritional value as food for fish. Our study demonstrates an environmentally safe OAE application, but also stresses the risks of more intense OAE options, and the vulnerabilities of other marine ecosystems.

Heavy metals concentration and human health risk assessment in selected shrimp species of Pakistan

ABSTRACT Heavy metal pollution in marine organisms poses a significant threat to both ecosystems and human health. Dumping untreated sewage into the sea pollutes coastal waters with toxic metals. This study examined the levels of chromium (Cr), lead (Pb), nickel (Ni), mercury (Hg), arsenic (As) and copper (Cu) in three shrimp species of genus Penaeus i.e. Penaeus merguiensis, Penaeus monodon, and Penaeus indicus. The findings revealed that the average levels of arsenic, lead, and mercury were considerably higher than the legislative limits. Furthermore, chromium and lead levels remained consistent across shrimp species, while other metals exhibited significant variation. Additionally, THQ and HI values were below the limit of 1, indicating low health risks from consuming shrimp species from this area. However, sustained monitoring and research are essential to protect consumer health and ensure long-term sustainability of seafood resources.

Flexible Photoacoustic Device Integrating Electroluminescence, Piezoelectric Vibration, and Pressure Sensing.

Marine organisms rely on the integration of light, sound, and pressure sensing for essential activities such as communication, hunting, and predator evasion. Current bioinspired devices, however, are limited by independent sensing modules, leading to complex designs and reduced adaptability. This study addresses these challenges by developing a multifunctional flexible photoacoustic device (MFPAD) that integrates electroluminescence, piezoelectric vibration, and pressure sensing into a single structure. Using airflow-assisted electrospinning, the device's fibrous layers were fabricated to optimize mechanical properties and enable synchronized responses to luminescence, sound, and pressure. Evaluations showed that MFPAD is highly sensitive to pressure changes, with corresponding light emissions, and efficient sound output modulated by input voltage and frequency. The device also enabled real-time posture tracking in robotic fish using an image recognition algorithm based on luminescence. Additionally, deep learning models allowed for the reconstruction of missing key points during motion. These findings demonstrate the promising potential of MFPAD for advancing bioinspired systems with multimodal sensing capabilities, offering a scalable solution for complex environments.

Isolation and Characterization of Effective Crude Oil Degrading Bacteria from Some Mussels Collected at Makaran Sea

Mussels are a group of beneficial marine organisms that have the ability to filter seawater so that seawater circulates inside the mussels and exits from the other side. Crude oil degrading bacteria exist in the tissue of mussels were enriched in ONR7a medium with crude oil as sole energy source. Some screening tests such as emulsification activity and bacterial adhesion to hydrocarbons were used for selection the best crude oil degrading bacteria. The quantity of heterotrophic bacteria was higher than degrading bacteria. Nineteen crude oil degrading bacteria were isolated from mussel’s samples collected from Makran shorelines. Most of the isolated bacteria were Gram-negative and bacilli. G5, O4, O10 and Q2 strains were selected as the best degrading strains based on screening analysis. The results of molecular identification showed that these four strains belonged to the following genera: Alcanivorax dieseloili Strain G5, Alcanivorax xenomutans strain O10, Halomonas denitrificans strain O4 and Pseudidiomarina aquimaris strain Q2. The results of this study showed that Makaran Sea have high diversity for degrading bacteria. If these bacteria were enriched and replicated in pilot phase the crude oil pollution can be managed in the real field at Makaran Sea.

One-step mass-production of CeO2 nanoparticles embedded in free-standing porous carbon as haloperoxidase mimetic coating to combat biofouling on steel surface

Marine biofouling poses significant challenges for maritime industries, leading to increased maintenance costs and ecological disturbances. While Cu-based biocide coatings are effective in combating biofouling, they raise environmental concerns and have limited lifespans. This has spurred interest in sustainable alternatives inspired by marine organisms, such as haloperoxidases (HPOs) found in certain algae, which can convert H2O2 and Br− in seawater into HOBr to mitigate biofouling. However, the practical implementation of HPOs is limited by their stability and cost. Nanozymes like CeO₂ have emerged as promising alternatives; however, conventional coating methods—typically involving the replacement of Cu-based biocides with CeO2 nanoparticles (NPs) in resin—restrict their exposure to H2O2 and Br⁻, resulting in significant activity loss. This study presents a simple method for mass-producing CeO2 NPs embedded in free-standing porous carbon as HPO mimetics. The optimized sample demonstrates exceptional HPO-like activity and antibacterial performance. Most importantly, we have shown that these HPO mimetics can be directly grown on steel surfaces during preparation, eliminating the need for a dispersant. This direct coating technique effectively addresses the challenges associated with conventional resin method, facilitating the development of a sustainable antibacterial and antifouling coating with preserved activity.

Evaluation of Microplastics Ingested by Sea Cucumber Holothuria Scabra from Pulau Jambongan, Sabah.

Microplastics (MPs) are tiny plastic pieces having a diameter of less than 5mm. They can arise from larger plastic debris that degrades over time, synthetic fibres from clothing, microbeads in personal care items and even larger plastic debris. Sea cucumbers are marine creatures vital to the ocean's ecosystem as they assist in maintaining a clean seabed and recycle nutrients. The aim of this research was to characterize the types of MPs isolated from the sea cucumber Holothuria scabra from Pulau Jambongan, Sabah. A total of 30 H. scabra were collected. Their gastrointestinal tracts were removed and digested using NaOH. The digestates were filtrated several times to extract the MPs. MPs were observed under microscope and categorized into shapes and colours. To determine the functional group of polymers, further analysis using Fourier Transform-Infrared Spectroscopy (FTIR) was performed. The samples contained a total of 7403 MPs. Majority of MPs were black colored (72.25%) and in the form of fibres (99.05%). Two types of polymers were detected: polycarbonate (PC) found in 4% of the population and polymethyl methacrylate (PMMA) present in 96%. In conclusion, the presence of MPs in the gastrointestinal tract of H. scabra suggests that the animals and their habitat have been contaminated. Further study is required to comprehend the effects of MPs on sea cucumbers and other marine organisms as well as to develop prevention strategies.

Metal concentrations in native and transplanted species in the Eastern Ionian Sea (Greece).

Metal concentrations (Cu, Cr, Ni, Zn, Fe, Mn, Cd, and Pb) in marine indicator species were assessed for the study of metal pollution in the Eastern Ionian Sea during the cold period of the year (December 2018 to February 2019). Limpets and sea urchins were collected from natural populations at seven coastal stations while mussels were transplanted at three near-shore stations in the study area. Mixed mesozooplankton samples were selected from a twelve-station offshore network. Additionally, fish, shrimp, and shortfin squid samples were collected by trawling. For the first time, metal concentrations in marine animals were measured in an extended variety of organisms in the area. Higher metal concentrations in limpets, sea urchins, and mussels were observed in the wider area of the two ports located at the sampling area's eastern and southern geographical borders. Levels in zooplankton also followed the same spatial variation. In general, metal concentrations in the investigated organisms were within the same range as those in other non-impacted Mediterranean areas. Accordingly, metal levels in the flesh of the fish, shrimps, and the mantle of shortfin squids did not reveal any risk for human consumption. Metal levels from the present study are proposed as a reference state for the area, while future deviations should be evaluated taking into account potential changes in the natural and anthropogenic pressures on the specific coastal marine ecosystem.

Research Progress on Using Modified Hydrogel Coatings as Marine Antifouling Materials

The adhesion of marine organisms to marine facilities negatively impacts human productivity. This phenomenon, known as marine fouling, constitutes a serious issue in the marine equipment industry. It increases resistance for ships and their structures, which, in turn, raises fuel consumption and reduces ship speed. To date, numerous antifouling strategies have been researched to combat marine biofouling. However, a multitude of these resources face long-term usability issues due to various limitations, such as low adhesion quality, elevated costs, and inefficacy. Hydrogels, exhibiting properties akin to the slime layer on the skin of many aquatic creatures, possess a low frictional coefficient and a high rate of water absorbency and are extensively utilized in the marine antifouling field. This review discusses the recent progress regarding the application of hydrogels as an important marine antifouling material in recent years. It introduces the structure, properties, and classification of hydrogels; summarizes the current research status of improved hydrogels in detail; and analyzes the improvement in their antifouling properties and the prospects for their application in marine antifouling.

Cyanoremediation of Polluted Seawater in the Arabian Gulf: Risks and Benefits to Human Health

Cyanobacteria play a crucial role in marine ecosystems as primary producers of food and oxygen for various organisms while helping remove waste and toxic substances from the environment. They are essential to the carbon cycle and help regulate the climate. These marine autotrophs also aid in the absorption of essential elements and support diverse life forms. They help degrade organic compounds, including petroleum hydrocarbons as well as heavy metals. Fluctuations in cyanobacteria populations can indicate ecosystem health, influencing both human well-being and wildlife. Their significance also extends to potential technological advancements, thus providing valuable resources for fields such as pharmacology, medicine, health care, biofuels, cosmetics, and bioremediation. However, some species produce toxins that pose risks to human health and marine organisms. Consequently, cyanobacteria are a major focus of research aimed at preserving and improving marine ecosystems—especially given the environmental damage caused by past and potential future conflicts. This review highlights their roles in cyanoremediation and other industrial and biotechnological applications with a particular focus on the Arabian Gulf region.

Heavy Metal Distribution in Aquatic Products from Eastern Guangdong and Associated Health Risk Assessment

With the rapid industrialization and urbanization of coastal areas, marine pollution (such as heavy metals) is increasingly contaminating the environment, posing significant public health risks. Eastern Guangdong, a key aquaculture and fisheries hub in China, has a growing market for aquatic products. Heavy metals persist in the environment and are difficult to degrade and bioaccumulate in marine organisms through the food web, presenting carcinogenic and mutagenic risks to humans, as top predators. This study analyzed 10 key species commonly consumed by residents of eastern Guangdong (bivalves, crustaceans, and fish), measuring the concentrations of six heavy metals (As, Cd, Cr, Cu, Ni, Pb) using inductively coupled plasma mass spectrometry (ICP-MS). Pollution levels were assessed using the pollution index (Pi), and dietary exposure risks were evaluated via the target hazard quotient (THQ) for different age groups. Results showed that Pi values for all metals were within normal background levels, but bivalves had a high capacity for Cd accumulation, with pollution severity ranking as bivalves > crustaceans > fish. The THQ values for both adults and teenagers were <1 across all samples, indicating no risk to the health of residents. However, the TTHQ for Sanguinolaria sp. exceeded 1, indicating potential health risks. This study highlights the health risks of consuming heavy metal-contaminated aquatic products, particularly bivalves. Reducing the consumption of these high-metal species could help lower dietary exposure and associated risks. Our findings provide essential data for the quality assessment of aquatic products and offer dietary recommendations for residents in eastern Guangdong.

Patagonian toothfish (Dissostichus eleginoides) stocks in South American waters and its implications for fishery management

Patagonian toothfish (Dissostichus eleginoides) is a highly prized resource in markets due to the quality of its meat. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) implemented controls and regulations in response to the sharp rise in the illegal fishing of D. eleginoides in the 1990s. Today, four fisheries in waters close to the southern tip of South America are managed in accordance with stringent sustainability standards. Even though they are separate management units, both abundance assessments and annual catch allocations are conducted using different criteria regarding stock considerations across the region, leaving one of the fundamental premises of fisheries management unclear. This study examines historical data and recent research to explore the potential differentiation between Patagonian toothfish populations in South American waters, which is crucial for the management of diverse fisheries. Genetic studies, otolith microchemistry, morphometry, parasitic fauna, tagging programs, reproductive characteristics, and the impact of ocean circulation on dispersal and recruitment were analyzed. Tagging studies in the southern hemisphere oceans confirm the species’ affinity to specific habitats, suggesting minimal fish exchange between South American fishing grounds. From a fisheries perspective, this review suggests the existence of distinct stocks of the species structured along the shelf and slope of the southern cone of America based on reproduction areas along the continental shelves and slope, the diverse parasitic fauna, the variability in stable isotopes and trace elements of otoliths, and the little significant exchange of fish between current fishing grounds. All of this could lead to considering the D. eleginoides fishery as independent exploitation units.

Paying attention to the safety of global edible seaweeds after the discharge of nuclear-contaminated water from Japan

Macroalgae play a crucial role as primary producers in the ecosystem. The increasing human demand for macroalgae has led to the development of the macroalgae aquaculture industry, which is seen as a potential solution to future food shortages. However, the Japanese Government's plan to discharge nuclear-contaminated water, which is projected to continue until at least 2053 with a total volume of at least 1.3 million metric tons, poses a significant threat to the macroalgae industry, ecosystems, and human health. Macroalgae can accumulate radionuclides from nuclear-contaminated water, which may then be transferred to other marine organisms or humans through the food chain or web, and the long-term implications of this ‘butterfly effect’ remain uncertain. In principle, international supervision and regulations should govern the management of nuclear waste, further filling the gaps in international law, including all aspects of addressing complaints and prohibiting the discharge of nuclear-contaminated water, to ensure responsible management based on scientific evidence. However, the current Japanese government's determination to proceed with the discharge of nuclear-contaminated water has revealed deficiencies in international legislation and a lack of enforcement power within international regulatory organizations, which demand further improvement. Herein, we call upon phycologists specializing in the utilization of macroalgal resources, marine organisms, and marine ecology to pay further attention to and conduct in-depth investigations into the potential long-term impacts of this event. Regardless, against the backdrop of Japan's ongoing discharge of nuclear-contaminated water, the commitment to advancing the health and stability of the global macroalgae industry and safeguarding the rights of seaweed farmers represents a lengthy but highly significant scientific endeavor.

Investigation of Microplastic Contamination in Diadema Setosum Obtained from a Fishing Barn

This study is undertaken to evaluate microplastic contamination levels in Diadema setosum specimens obtained from a fishing barn. Microplastic (MP) pollution levels and their potential impacts on marine biota are still unknown compared to coastal and offshore environments. For this purpose, 19 individuals of D. setosum were collected and microplastic abundance in their gastrointestinal tract (GIT) and gonad were investigated. Mean microplastic abundance in GITs was 3.0 MPs±3.1 MPs per individual and 0.9±1.0 MPs per g wet weight. Mean microplastic abundance in the gonads was 0.3±0.6 MPs per individual and 0.08±0.2 MPs per g wet weight. Among all MPs, 45% of extracted MPs were fibers, followed by fragments (44%) and pellets (11%). Regarding size, the majority of the MPs extracted from GITs and all of the MPs extracted from gonads were small size MPs (less than 1 mm in size). FTIR analysis validated the plastic nature of suspected particles. Polyethylene (PE) (50%) and polypropylene (PP) (50%) were the most common type of polymers. These are the main polymers used in production of fishing nets; therefore, this result seems to validate the anthropogenic influence in the study area. This study contributes to the knowledge of the transfer of microplastics to the marine food web and highlights the need for protective measures.

Mercury bioaccumulation and assimilation in marine plankton in meltwater influenced fjords and shelf waters along the east coast of Greenland.

The rapid melting of the Arctic cryosphere due to climate change will result in significant freshwater input into Arctic marine ecosystems. This might also cause the release of legacy mercury (Hg) stored in the cryosphere, increasing Hg concentration and its subsequent effects on the marine biota. However, there is scarce knowledge on the concentration of Hg in the lower trophic level organisms at the base of the Arctic pelagic food web. This is particularly important since these organisms modulate the transfer of Hg to higher trophic levels, including fish and marine mammals. We quantified the Hg concentration in two plankton size classes (> 200 and 50 – 200 μm) in coastal waters along the east Greenland coast and investigated the potential assimilation efficiency of both inorganic Hg (IHg) and methyl Hg (MeHg) in mesozooplankton and their faecal pellets in experimental incubations. The concentration of Hg in plankton ranged from 12 to 109 ng (g dw)-1 without clear trends between geographic locations or between fjords and coastal areas. Also, the concentrations did not vary between the different plankton size fractions. MeHg concentrations were lower in the mesozooplankton faecal pellets than IHg, which may be due to the higher assimilation of MeHg than IHg in mesozooplankton tissue. Our results confirm that Arctic zooplankton assimilates MeHg more efficiently than IHg and may contribute significantly to the partitioning and cycling of different Hg types in Arctic marine ecosystems.

Plastic Ingestion by Marine Biota in Five Southeast Asian Nations: Complex Challenges and Long-Term Implications

Plastic Ingestion by Marine Biota in Five Southeast Asian Nations: Complex Challenges and Long-Term Implications

Using diatom chain length as a bioindicator of heavy-metals contamination in marine environments

The increasing release of toxic heavy metals into marine environments poses significant risks due to their persistence and bioaccumulation. Diatoms are ideal bioindicators because of their sensitivity to environmental changes. Despite traditional methods for detecting these persistent pollutants effectively identify composition and concentration, they are time-consuming, they often require the use of harmful reagents, and do not allow a fast assessment of detrimental impacts on marine organisms. To fill this gap, we have successfully investigated the toxicity of different heavy metals in the marine diatom Skeletonema pseudocostatum thanks to a newly developed high-power terahertz (THz) spectrometer. By combining THz spectroscopy, microscopy and ecotoxicological assays, we found that the formation of long diatom chains is significantly inhibited by the presence of lead, copper, and chromium, which disrupt their metabolism. Although the THz absorption and refractive index spectra were not affected by diatom concentration in undoped samples, THz frequencies were highly sensitive to changes in diatom chain length due to heavy metals exposure. These findings suggest that this approach allows to investigate the biochemical processes involved in chain formation in S. pseudocostatum and related algae. THz spectroscopy could therefore provide deeper insights into the microscopic metabolic activity of diatoms, addressing key biochemical questions surrounding these organisms. Furthermore, we propose this novel approach for environmental pollution monitoring, since it could provide a rapid, harmless and sensitive detection method to assess heavy metal toxicity in marine diatoms, key organisms at the basis of the trophic chain.

Rapid characterization of polysaccharides from marine animals using chemical degradation combined with liquid chromatography mass spectrometry.

Glycosaminoglycans of marine origin have exceptional biological activities, but rapid elucidation strategies for precise structures are still lacking. In this study, the optimal conditions for deacetylation of glycosaminoglycans were optimized first. The hydrazinolysis time of 24 h was determined as the final condition, oligosaccharides with a degree of polymerization of 2-14 are mainly produced after hydrazinolysis. Then mixed oligosaccharides generated by deacetylation-deamination cleavage of polysaccharides were detected with hydrophilic interaction chromatography with tandem mass spectrometry (HILIC-MS/MS), and the total ion chromatography showed excellent resolution. The mass spectrometry data were automatically processed by GlycReSoft, and the corresponding matching results were obtained according to the set parameters. A small amount of keratan sulfate exists in oligosaccharides of Teuthida and Salmo salar, and ion peaks corresponding to IdoA-GalNAc4S exist in oligosaccharides of Scophthalmus maximus and Salmo salar. The results of the manual analysis of the mass spectrometry data verified that the HILIC-MS/MS combined with automatic analysis by software adopted in this study could achieve accurate matching and matching of mixed oligosaccharide components. The establishment of a rapid and accurate analysis strategy for the structure of glycosaminoglycans in this study will help the development of its application and standardized industrial production.