Clam Species Research Articles

Potentially toxic elements (PTEs) in the invasive Asian clam (Corbicula fluminea) from polluted urban river areas of Bangladesh and evaluation of human health risk.

The invasive Asian clam species, Corbicula fluminea, has significant ecological and societal implications at both local and international levels due to its nutritional aspects. C. fluminea from four urban rivers in Bangladesh exhibited negative allometric growth and degree of contamination with potentially toxic elements (PTEs), which posed a concern to human health based on the AAS and USEPA risk models. The highest mean concentration of PTEs followed a decreasing order: Zn (155.08 ± 4.98mg/kg) > Cu (53.96 ± 7.61mg/kg) > Mn (14.29 ± 3.25mg/kg) > Cd (2.23 ± 0.10mg/kg) > Pb (1.64 ± 0.14mg/kg) > As (1.51 ± 0.45mg/kg) > Ni (1.25 ± 0.27mg/kg) > Cr (0.65 ± 0.02mg/kg) in C. fluminea and raising safety concerns. With the exception of Cr and Mn, all element levels were exceeded safety guideline value (SGV) (mg/kg. ww) and exhibited a strong positive correlation (p < 0.05) among the sites. The target hazard quotient of Mn is THQ > 1, and As showed a non-carcinogenic risk in children at OBR, BR, and MR site. The hazard index (HI > 1) value at the BR and MR sites indicated a public health risk associated with the clam. The target cancer risk (TCR) values for As, Cd, and Ni showed that consuming clams posed a carcinogenic risk to human health. These findings suggest that eating these clams may put consumers at significant risk for health issues related to As, Cd, Ni, and Mn exposure. The study emphasizes the need for strict monitoring and preventative measures to reduce the health risks posed by PTEs contamination in clams.

Evaluating the impact of gadolinium contamination on the marine bivalve Donax trunculus: Implications for environmental health

Gadolinium (Gd), commonly used in contrast agents for medical imaging, has been detected in hospital wastewater and aquatic environments, raising environmental concerns. This study examined the accumulation and cellular impacts of Gd in the clam species Donax trunculus, commonly used as bioindicator of contamination. Gadolinium accumulation in clams increased with exposure and over time. Biological responses varied with Gd levels: low concentrations (10 and 50 µg/L) led to low metabolic activity and glycogen content, but high antioxidant activities and lipid peroxidation levels (LPO); high concentrations (250 and 500 µg/L) resulted in increased metabolic activity, while antioxidant enzyme activity was inhibited and LPO levels were the lowest. Metabolic activity decreased after two weeks, suggesting limited long-term metabolic resilience. The study underscores D. trunculus as an effective early warning species for Gd pollution and highlights the ecological risks of rising Gd levels, emphasizing the need for environmental monitoring and regulation.

MORPHOLOGICAL VARIATIONS IN MUD CLAM Polymesoda erosa (Lightfoot) USING FLUCTUATING ASYMMETRY ANALYSIS IN LA UNION, CABADBARAN CITY, AGUSAN DEL NORTE, PHILIPPINES

A geometric morphometric study was conducted on the population of Polymesoda erosa in La Union, Cabadbaran City, to investigate the morphological variations using fluctuating asymmetry (FA) analysis. FA acts as a reliable indicator of ecological stress and developmental instability since it detects genetic or environmental changes that an organism experiences. A total of ninety (90) individual mud clams were randomly collected and analyze. Water and soil samples were also collected to gather data on the degree of body variations and the impact of external factors on P. erosa. The result of the analysis using the SAGE software revealed a highly significant fluctuating asymmetry (P 0.0001). Significant variations in individuals, sides, and the interaction between individuals and sides symmetry were mostly responsible for the substantial variances seen in mud clam species. Particularly, landmarks 10 (dorsal margin maxima) and 13 (anterior margin maxima) exhibited notable variations. For the water quality results, the mud clam's internal valve was likely to be relatively unaffected or minimally impacted, but the level of nickel was high. In conclusion, the fluctuating asymmetry of P. erosa can be attributed to a stressed environment. Unfavorable environmental factors cause an organism's morphology to change, affecting its symmetry.

Symbiodiniaceae‐Derived Fatty Acids Are Stored Differentially Across Giant Clam Species and Organs

ABSTRACTGiant clams are invertebrates that form mutualistic associations with Symbiodiniaceae dinoflagellates. Despite their ecological significance, gaps persist regarding our understanding of their trophic ecology. Specifically, it is unknown whether Symbiodiniaceae‐derived photosynthates are metabolized differently according to species and organ. Therefore, we maintained Tridacna derasa and T. noae for 3 months in a well‐lit recirculated system without food supply. Samples were taken from eight organs and underwent lipid extraction and fatty acid esterification before analysis of three symbiont‐derived fatty acids (stearidonic acid, docosapentaenoic acid, and docosahexaenoic acid—SDA, DPA, and DHA, respectively) using gas chromatography. Results show considerable variation in fatty acids concentration among species and organs. SDA was found in higher concentrations in T. noae, especially in the adductor muscle. DPA was detected in low concentrations across T. noae organs and absent for T. derasa. DHA did not vary significantly among species and organs. Our findings indicate that Symbiodiniaceae supply clams with fatty acids, which are stored differentially according to species and organs. This demonstrates that these compounds are translocated to multiple organs throughout the complex giant clam anatomical system, in contrast to simpler hosts like corals. These results advance our understanding of the physiological dynamics of the mollusk‐algae association.

Guardians of the clams: a decadal monitoring effort of endangered giant clams by citizen scientists

ABSTRACT Giant clams are highly conspicuous marine bivalves in the tropical oceans because of their large shells and colourful outer mantle tissues. This makes them an appropriate iconic species for both trained and untrained citizen science surveys. In Singapore, because of good public awareness of giant clams, they are often reported by citizen scientists, who document marine species using photography. Furthermore, these opportunistic records are captured in a comprehensive public blog (Wild Shores of Singapore; https://wildshores.blogspot.com) with specific details of the field surveys. This study presents the first feasible effort in establishing a long-term dataset based on citizen science observations to report giant clam species-level population status and trends over time. Between 2011 and 2020, citizen scientists covered 8.53 km2 of intertidal reef areas and consistently recorded only two giant clam species (Tridacna squamosa and T. crocea) annually. Despite the more comprehensive coverage and sampling of reef areas, the citizen scientists did not encounter the other native species: Hippopus hippopus, T. gigas and T. maxima. Also, the respective densities of T. squamosa and T. crocea were 0.00120 and 0.00034 individuals per 100 m2, which makes them the smallest known giant clam populations in the Indo-Pacific region. Regardless, the sampling efforts of citizen scientists were generally similar across the years, but future surveys could adapt different survey protocols for the respective giant clam species. Findings from this study also support the marine conservation efforts in Singapore, such as using active intervention measures to protect their giant clams. Additionally, lessons learnt from these citizen science observations can be harnessed to encourage monitoring of giant clams throughout the Indo-Pacific region.

New clam species found in South Africa’s kelp forests

New clam species found in South Africa’s kelp forests

Ocean acidification will not affect the shell strength of juveniles of the commercial clam species Chamelea gallina: Implications of the local alkalinization of seawater

Ocean acidification (OA) is expected to decrease the strength of bivalves’ shells, especially during the early stages of development, with negative consequences to the resilience of natural populations and the economy. The objectives of the present study were to assess the long-term effect of increasing pCO2 after 217 days of exposure under controlled conditions of pH of ∼8.2, 8.0, and 7.7 on the strength and integrity of shells of juveniles of the commercial striped venus clam Chamelea gallina. Shell strength was estimated through compression tests and integrity through scanning electron microscopy (SEM) and dispersive X-ray analyses (EDX). The results showed that under increasing pCO2 the shell strength of juveniles is unaffected, which could be related to the locally elevated total alkalinity of seawater with respect to other parts of the coastal lagoon. However, despite this, it was also observed that the juvenile clams exposed to elevated pCO2 decreased their shell thickness and increased the porosity of their prismatic layer. Under future OA conditions, these changes could eventually compromise the integrity of the shells, becoming more vulnerable to the attack of predators and breakable during fishing operations. Future studies should address the plasticity of the organisms and the effect of the alkalinization of seawater on the resilience of shellfish juveniles under global change conditions.

Using Design-Based Research to Develop the Learning Outcomes of a Curriculum-Based Environmental Citizen Science Project

The Intertidal Monitoring Project (IMP) is a local, curriculum-based citizen science project intentionally designed to support the development of science competencies in elementary students. The focus of the IMP is the Research Days, where students follow an established scientific protocol to collect monitoring data on an introduced species of clam in British Columbia, Canada. The IMP represents a unique program to study because the school district funds transportation and programming costs so that all grade five students can engage in authentic place-based scientific research. A design-based research (DBR) approach was used to develop and refine the IMP activities between 2014 and 2023. This research is focused on a DBR Evaluation/Reflection phase that qualitatively assessed learning outcomes during the beta testing of a supplementary classroom activity. Student- and teacher-generated data were collected to understand the process of a class “coming to know” science and its community of practice during the IMP activities. This included student learning artefacts and a teacher interview. The findings show that participation in IMP activities: i) fostered the development of science competencies in a grade five learning community; ii) did not promote science identities; and indicated that iii) the Nature of Science (NOS) required more explicit instruction. Student-teacher-scientist partnerships (STSPs) emerged as a critical design element of curriculum-based citizen science.

First report of Noah’s clam Tridacna noae (Röding, 1798) in the reef of Culion: An addition to the distribution range in Palawan, Philippines

This study provides additional information regarding the distribution range and habitat characteristics of two specimens Tridacna noae (Röding, 1798), a previously misidentified giant clam species, encountered in Barangay Malaking Patag, Culion, Palawan, Philippines. The giant clams were identified as T. noae due to the presence of ocellate spots or teardrops and sparse hyaline organs on the mantle. The specimens measured 7.8 and 7.9 cm in shell length and were found partially buried in dead coral substrates at a depth of 2 meters. The current findings provide additional information on the distribution range of T. noae in the province of Palawan and the Philippines. Identification of the distribution of certain threatened species, such as the giant clams, is crucial step in protecting and conserving their population in the wild.

The Complete Mitochondrial Genome of the Chemosymbiotic Lucinid Bivalve Pillucina pisidium (Dunker, 1860) Occurring in Seagrass Zostera marina Bed in a Lagoon in Jeju Island, Korea

Commonly found in tropic and subtropic seagrass beds, lucinid clams host sulfur-oxidizing bacteria within their gills. These symbionts are crucial in converting phytotoxic sulfide in the sediment into less harmful sulfate, thus enhancing the environment for seagrasses and associated biota. We recently uncovered small clams within a Zostera marina seagrass bed situated in a lagoon on Jeju Island, off the south coast of Korea. These bivalves, with shell lengths of up to 7 mm, exhibited distinct features, including thick and hypertrophied gills, inflated and ovoid shells with a shell height/shell length ratio of 0.99, and the absence of a sulcus on the external shell surface. These characteristics align closely with those of Pillucina pisidium, a lucinid clam species originally reported in Japan. Analysis of the cytochrome b gene partial sequences of the clams from Jeju Island revealed a 100% match with P. pisidium reported in Japan, confirming their identity. Moreover, we successfully assembled the complete mitochondrial genome of P. pisidium for the first time, revealing a circular genome spanning 21,059 bp. Additionally, we constructed a phylogenetic tree using 13 protein-coding genes (PCGs) extracted from the mitochondrial genome of P. pisidium. Notably, P. pisidium formed a distinct clade within the subclass Autobranchia alongside other lucinid clams in the phylogenetic tree. However, within the family Lucinidae, synteny analysis of the 13 PCGs revealed diverse gene arrangement patterns, indicating considerable divergence. This divergence underscores the need for an extensive examination of Lucinidae mitochondrial genomes to elucidate the phylogenetic ties more precisely within the family, highlighting P. pisidium’s distinct evolutionary path within the family Lucinidae.

Vanishing giants: An assessment on the population status of giant clams across Malaysia

The iconic giant clams are known for its multifaceted importance throughout the Indo-Pacific –for functional, ecological, or cultural purposes. In Malaysia, habitat destruction and illegal poaching were main reasons behind the declining populations of giant clams. As previous surveys date back to 1990 s, an update on the status of giant clam populations in Malaysia is overdue. Using the extensive monitoring data from Reef Check Malaysia, we analysed and provided an assessment of population trends of giant clams between 2007 and 2021 in Malaysia. This study showed a decline in giant clam population in the east coast Peninsula and Sabah, while their abundances have always been low in the west coast Peninsula and Sarawak. In the east coast Peninsula, Tridacna maxima and T. crocea were most common (2.7 ± 7.3 and 1.4 ± 7.6 clams per 100 m2, respectively), followed by T. squamosa (0.7 ± 1.4 clams per 100 m2), and Hippopus hippopus (0.3 ± 2.5 clams per 100 m2). The boring species, T. maxima and T. crocea, typically displayed highly aggregated populations, reaching densities of 41.5 and 70 clams per 100 m2, where a reciprocal abundance shift between both species was observed between northern and southern sites of east coast Peninsula. The demography of T. maxima and T. crocea is either positively skewed or normally distributed, indicating abundant recruits that correspond to their higher densities. In contrast, T. squamosa showed a negative skew, suggesting poor recruitment rates. Findings here underscore the need to tailor conservation strategies for respective giant clam species in Malaysia. Proposed initiatives include establishing conservation zones in key areas like Perhentian, Lang Tengah, Redang, and Tioman Islands, which have significant T. maxima and T. crocea recruit populations. Also, targeted restocking efforts are necessary for T. squamosa and H. hippopus to ensure long-term viability of populations.

Ecological potential of giant clams in Ambon Island waters, Eastern Indonesia

Giant clams are protected marine organisms universally, thus information on giant clams is important for management purposes. This research was conducted in July to August 2021 in Morella and Suli, Ambon Island Maluku Province to get information on ecological potential which consist of species composition, density, occurrence frequency and diversity of giant clams. Sample was collected by using linear quadrat transect line. As many as 25 quadrants (10x10m) were used in both locations. Every individual of giant clams found in the quadrant was identified, photographed and counted. There were three species of giant clams found in Morella namely Tridacna crocea, T. maxima, and T. squamosa while four species were found in Suli i.e. those three species mentions earlier and Hippopus Hippopus. Totally, T. crocea had more individuals followed by T. squamosa and then T. maxima while the lesser belonged to H. Hippopus with one individual. Density of giant clams in Morella (428 ind./ha) was much higher than density of giant clams in Suli (48 ind./ha). Giant clams in Morella can be found in 16 - 19 quadrants of 25 quadrants used while in Suli only found in 1 - 6 quadrants. Ecological indexes for diversity, evenness and dominance showed that giant clams in Morella and Suli had moderate diversity, high evenness and low dominance.

Effects of Nutrient Source, Temperature, and Salinity on the Growth and Survival of Three Giant Clam Species (Tridacnidae).

The habitats of giant clams are undergoing environmental changes, and giant clam populations are declining. The present study was conducted to facilitate clam conservation. We conducted three 18-week trials to investigate the effects of nutrient, temperature, and salinity on the growth performance and survival rates (SRs) of juvenile Tridacna noae, adult Tridacna crocea, and subadult Tridacna derasa, respectively. Regarding nutrient sources, no significant differences were observed in shell length gain, specific growth rate, or SR between clams fed with Chaetoceros muelleri or commercial feed (hw nanotip) and those in a control group (juvenile phototrophs). Regarding temperature, clams cultivated at 27 °C exhibited significantly better growth performance and SR than did those cultivated at 19 °C or 31 °C (p < 0.05). By week 6, all clams in the 19 °C and 31 °C groups had died, indicating that suboptimal growth temperatures have severe adverse effects. Regarding salinity, clams cultivated at 34‱ exhibited significantly higher length gains and specific growth rates than did those cultivated at 20‱ or 25‱ (p < 0.05). SR was not significantly affected by salinity. Understanding how environmental factors affect giant clam populations may help researchers devise effective clam conservation strategies.

Recent record of True Giant Clam Tridacna gigas from the Sulu Archipelago and insight into the giant clam fisheries and conservation in the southernmost islands of the Philippines

The Philippines is a hotspot for marine biodiversity, particularly for giant clams like Tridacna gigas. Despite protective measures, giant clams are threatened with extinction due to overharvesting and habitat loss. We conducted a rapid documentation of a rampant giant clam fishery and trade we discovered in Panggungan Island in Sitangkai, Tawi-Tawi during our assessment, following a ship grounding incident in the area. We observed numerous empty shells of various giant clam species scattered across the area, indicating active harvesting by the community. The locals sell the meat, either fresh or dried and pearls collected from giant clams. The local community culture live with giant clams, including the true giant clam species, Tridacna gigas, along the shorelines. The largest live T. gigas individual we documented had a shell length of about 60 cm. Our study provides the first documentation of wild adult T. gigas in the Sulu Archipelago. It is also the only report of sighting of wild adult T. gigas aside from Palawan. Furthermore, our study marks the first account of giant clam trade within the Philippines since the early 1980s when the government issued a total ban on catching and selling of all species giant clams. Our findings highlight the critical need for a thorough assessment of T. gigas and other giant clam species in the biodiversity-rich Sulu Archipelago. Effective conservation of giant clams and the surrounding reefs will ensure the future of our marine ecosystems and the communities that rely on them.

Context-dependent resilience of intertidal seagrass and venerid clams after hyposalinity stress

Reduced salinity in estuarine areas can negatively affect intertidal seagrass meadows where clams are harvested. However, legacy effects of hyposalinity on seagrasses and infaunal clams and on their interactions have seldom been studied. Legacy effects were examined in the intertidal seagrass Zostera noltei and juveniles of the clams Venerupis corrugata, Ruditapes decussatus and R. philippinarum. Low-salinity stress was applied to mesocosms that included assemblages of seagrass and the 3 clam species that were subsequently transplanted to 2 shellfish beds characterized by different environmental conditions (i.e. seawater temperature, salinity and nutrient concentration). After 2 mo, the morphological and biochemical traits of Z. noltei and the growth and mortality of the clams were measured. Past hyposalinity stress increased clam mortality and decreased Z. noltei leaf length. The native V. corrugata was the most vulnerable to past hyposalinity, whereas the introduced clam R. philippinarum was the most resilient. The presence of clams was associated with greater nitrogen content and biomass of the above-ground parts of Z. noltei. Survival of the clams after past hyposalinity stress was greater below Z. noltei than below bare sediment, indicating persistent positive interactions following the harsh environmental conditions and during low-salinity periods in the field. At the colder and more nutrient-rich site, positive interactions were more frequent and Z. noltei performed better. This supported the influence of abiotic conditions on the recovery process. Nonetheless, enhanced survival of clams below Z. noltei indicates that Z. noltei could favour the sustainability of these shellfisheries after exposure to extreme rainfall events.

Correction to: The stress response of the seagrass Zostera noltei and three commercial clam species to low salinity associated with heavy rainfall

Correction to: The stress response of the seagrass <i>Zostera noltei</i> and three commercial clam species to low salinity associated with heavy rainfall

Using a metabolomics approach to investigate the sensitivity of a potential Arctic-invader and its Arctic sister-species to marine heatwaves and traditional harvesting disturbances

Coastal species are threatened by fishing practices and changing environmental conditions, such as marine heatwaves (MHW). The mechanisms that confer tolerance to such stressors in marine invertebrates are poorly understood. However, differences in tolerance among different species may be attributed to their geographical distribution. To test the tolerance of species occupying different thermal ranges, we used two closely related bivalves the softshell clam Mya arenaria (Linnaeus, 1758), a cold-temperate invader with demonstrated potential for establishment in the Arctic, and the blunt gaper Mya truncata (Linnaeus, 1758), a native polar species. Clams were subjected to a thermal stress, mimicking a MHW, and harvesting stress in a controlled environment. Seven acute temperature changes (2, 7, 12, 17, 22, 27, and 32 °C) were tested at two harvesting disturbance intensities (with, without). Survival was measured after 12 days and three tissues (gills, mantle, and posterior adductor muscle) collected from surviving individuals for targeted metabolomic profiling. MHW tolerance differed significantly between species: 26.9 °C for M. arenaria and 17.8 °C for M. truncata, with a negligeable effect of harvesting. At the upper thermal limit, M. arenaria displayed a more profound metabolomic remodelling when compared to M. truncata, and this varied greatly between tissue types. Network analysis revealed differences in pathway utilization at the upper MHW limit, with M. arenaria displaying a greater reliance on multiple DNA repair and expression and cell signalling pathways, while M. truncata was limited to fewer pathways. This suggests that M. truncata is ill equipped to cope with warming environments. MHW patterning in the Northwest Atlantic may be a strong predictor of population survival and future range shifts in these two clam species. As polar environments undergo faster rates of warming compared to the global average, M. truncata may be outcompeted by M. arenaria expanding into its native range.

Co-infection of two eukaryotic pathogens within clam populations in Arcachon Bay.

The parasitic species Perkinsus olseni (= atlanticus) (Perkinsea, Alveolata) infects a wide range of mollusc species and is responsible for mortality events and economic losses in the aquaculture industry and fisheries worldwide. Thus far, most studies conducted in this field have approached the problem from a "one parasite-one disease" perspective, notably with regards to commercially relevant clam species, while the impact of other Perkinsus species should also be considered as it could play a key role in the disease phenotype and dynamics. Co-infection of P. olseni and P. chesapeaki has already been sporadically described in Manila clam populations in Europe. Here, we describe for the first time the parasitic distribution of two Perkinsus species, P. olseni and P. chesapeaki, in individual clam organs and in five different locations across Arcachon Bay (France), using simultaneous in situ detection by quantitative PCR (qPCR) duplex methodology. We show that P. olseni single-infection largely dominated prevalence (46-84%) with high intensities of infection (7.2 to 8.5 log-nb of copies. g-1of wet tissue of Manila clam) depending on location, suggesting that infection is driven by the abiotic characteristics of stations and physiological states of the host. Conversely, single P. chesapeaki infections were observed in only two sampling stations, Ile aux Oiseaux and Gujan, with low prevalences 2 and 14%, respectively. Interestingly, the co-infection by both Perkinsus spp., ranging in prevalence from 12 to 34%, was distributed across four stations of Arcachon Bay, and was detected in one or two organs maximum. Within these co-infected organs, P. olseni largely dominated the global parasitic load. Hence, the co-infection dynamics between P. olseni and P. chesapeaki may rely on a facilitating role of P. olseni in developing a primary infection which in turn may help P. chesapeaki infect R. philippinarum as a reservoir for a preferred host. This ecological study demonstrates that the detection and quantification of both parasitic species, P. olseni and P. chesapeaki, is essential and timely in resolving cryptic infections and their consequences on individual hosts and clam populations.

Spatiotemporal variation in clam recruitment among beaches in Washington State (USA)

AbstractAbundant clam populations provide ecosystem services and commercial and recreational shellfish harvests worldwide. Two non‐native clams (Manila clams, Ruditapes philippinarum; eastern soft‐shell clams, Mya arenaria) commonly populate mid‐intertidal zones of coarse‐sediment beaches in Washington State, USA. To better understand factors influencing their abundance, we used passive mid‐intertidal spat collectors to determine the density and distribution of clam recruits (150–500 μm shell length) at eight beaches spanning over 500 km and over two reproductive seasons (2016 and 2017). Cumulative seasonal recruitment (clams &lt;500 μm) in 2016 and 2017 at +1.0 m MLLW ranged from 800 to 125,000 m−2 for Ruditapes philippinarum and 50–85,000 m−2 for M. arenaria, and did not differ by substrate type at small scales (gravel vs. crushed shell). At larger scales, different interannual recruitment patterns across sites did not dramatically shift the ranked order of highest and lowest recruitment sites. Cumulative recruitment tended to be lower at warmer sites, while timing of peak recruitment was not consistently related to temperature. Sites also differed in the relative recruitment of the two clam species, but most beaches had greater densities of R. philippinarum than M. arenaria at both recruitment and juvenile stages. Although recruitment densities differed by two orders of magnitude across sites, post‐settlement factors eliminated initial spatial variation within a year, dampening recruitment variability among these beaches that all contribute to commercial and recreational clam production.

Source-specific ecological and health risks of polycyclic aromatic hydrocarbons in the adjacent coastal area of the Yellow River Estuary, China.

Industrialization and urbanization have led to increasing levels of PAH pollution in highly urbanized estuaries and their adjacent coastal areas globally. This study focused on the adjacent coastal area of the Yellow River Estuary (YRE) and collected surface seawater, surface sediment, and clams Ruditapes philippinarum and Mactra veneriformis at four sites (S1 to S4) in May, August, and October 2021 to analyze the source-specific ecological and health risks and bioeffects. The findings revealed that the main sources of PAHs were traffic emission (25.2% to 28.5%), petroleum sources (23.3% to 29.5%), coal combustion (24.7% to 27.5%), and biomass combustion (19.8% to 20.7%). Further, the PMF-RQ and PMF-ILCR analyses indicated that traffic emission was the primary contributor to ecological risks in seawater and health risks in both clam species, while coal combustion was the major contributor in sediment. Taken together, it is recommended to implement control strategies for PAH pollution following the priority order: traffic > coal > petroleum > biomass, to reduce the content and risk of PAHs in the YRE.