Ran Bi

Marine microalgae, as the primary producers in ocean ecosystems, play a critical role in global carbon cycling and are efficient accumulators of arsenic (As) from seawater, raising concerns about its trophic transfer through marine food webs. Rising terrestrial nutrient inputs, particularly excess nitrogen, have elevated nitrogen-to-phosphorus (N/P) ratios, representing a widespread ecological concern that alters marine biogeochemical cycles and threatens the survival of marine microalgae. A deeper understanding of how arsenic uptake and transformation biogeochemistry in marine microalgae respond to intensifying N/P ratios is thus crucial to predict the response of marine ecosystems and their contribution to global climate change. Despite these concurrent trends, the impact of altered nutrient dynamics on the arsenic biogeochemistry in marine microalgae remains largely unexplored. Here, we show that appropriately increased N/P ratios markedly enhance arsenic accumulation and promote the intracellular conversion of inorganic As to organic species. Transcriptome data further demonstrate that marine microalgae could significantly upregulate gene expressions associated with arsenic transport-related genes to cope with increased N/P ratios. Metabolomic flux analysis revealed that elevated N/P ratios promoted photosynthetic carbon fixation, ATP synthesis, and carbohydrate metabolism, while the amino acid metabolism was suppressed in marine microalgae, and the redirected energy flow may facilitate arsenic metabolism. Collectively, the reallocation of metabolic energy under high N/P conditions contributed to increased arsenic uptake and biotransformation in marine microalgae. An analysis of the Tara Oceans database confirmed these patterns and showed that arsenic metabolism-related genes are widely distributed across global surface oceans. Continuous nitrogen inputs and rising N/P ratios may alter arsenic speciation and mobility, benefiting cellular detoxification in the short term but potentially increasing organic arsenic accumulation, trophic transfer, and associated ecological and human health risks over longer time scales.

Microorganisms play an essential role in the biogeochemical processes of macroalgal cultivation ecosystems by participating in a complex network of interactions, significantly influencing the growth and development of macroalgae. This study used bibliometric analysis and VOSviewer based on Web of Science data to provide an overview by tracing the developmental footprint of the technology. Countries, institutions, authors, keywords, and key phrases were tracked and mapped accordingly. From 1 January 2003 to 31 December 2023, 619 documents by 2516 authors from 716 institutions in 51 countries were analyzed. Keyword co-occurrence network analysis revealed five main areas of research on microbes in macroalgal cultivation ecosystems: (1) identification of microbial species and functional genes, (2) biogeochemical cycling of carbon in microbial communities, (3) microbial influences on macroalgae growth and development, (4) bioactivities, and (5) studies based on database. Thematic evolution and map research emphasized the centrality of microbial diversity research in this direction. Over time, the research hotspots and the core scientific questions of the microorganisms in the macroalgal cultivation ecosystems have evolved from single-organism interactions to the complex dynamics of microbial communities. The application of high-throughput techniques had become a hotspot, and the adoption of systems biology approaches had further facilitated the integrated analysis of microbial community composition and function. Our results provide valuable guidance and information for future researches on algal–bacterial interactions and microbe-driven carbon cycling in coastal ecosystems.

Microorganisms play an essential role in the biogeochemical processes of macroalgal cultivation ecosystems by participating in a complex network of interactions, significantly influencing the growth and development of macroalgae. This study used bibliometric analysis and VOSviewer based on Web of Science data to provide an overview by tracing the developmental footprint of the technology. Countries, institutions, authors, keywords, and key phrases were tracked and mapped accordingly. From 1 January 2003 to 31 December 2023, 619 documents by 2,516 authors from 716 institutions in 51 countries were analyzed. Keyword co-occurrence network analysis revealed five main areas of research on microbes in macroalgal cultivation ecosystems: (1) identification of microbial species and functional genes, (2) biogeochemical cycling of carbon in microbial communities, (3) microbial influences on macroalgae growth and development, (4) bioactivities, and (5) studies based on database. Thematic evolution and map research emphasized the centrality of microbial diversity research in this direction. Over time, the research hotspots and the core scientific questions of the microorganisms in the macroalgal cultivation ecosystems have evolved from single-organism interactions to the complex dynamics of microbial communities. The application of high-throughput techniques had become a hotspot, and the adoption of systems biology approaches had further facilitated the integrated analysis of microbial community composition and function. Our results provide valuable guidance and information for future research.

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 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.

Little is known about the comprehensive factors influencing temporal changes in microplastic abundance in marine ecosystems. We investigated seasonal variations in the microplastic distribution in marine sediments in multiple-used zones of Eastern Guangdong in the South China Sea. The top 10 cm sediments from 26 sites were collected by grab sampling in the spring, summer, and winter of 2021. Marine sediments had the lowest microplastic abundance in summer, significantly lower than in other seasons. The size of microplastics varied from 22.5 to 4363.3 µm but the 50–200 µm range was the most abundant. Transparent and fragmented microplastics were the most frequently observed composition. Microplastic abundance negatively correlated to distance to the coast. However, seaweed ecosystems impacted microplastic abundance by changing the microenvironment and/or direct contact and entrapment. Microplastic abundance is closely related to coastal mariculture and local residential and industrial activities. Polypropylene, polypropylene-polyethylene copolymer, polyethylene terephthalate, and polyethylene were the most frequently detected compositions, probably from packaging materials, textiles, and electronic/electrical/building industries. This work helps to understand the role of multiple-used zones and their influence on microplastic distributions in marine ecosystems. Appropriate management of the use and disposal of plastic waste on land was recommended to alleviate microplastic pollution in the marine environment.