Deciphering the diversity and distribution of chromophytic phytoplankton in the Bohai Sea and the Yellow Sea via RuBisCO genes (rbcL).

Present study investigated composition and distribution of chromophytic phytoplankton in the Bohai Sea (BS) and the Yellow Sea (YS) by using rbcL genes. Bacillariophyceae, Haptophyceae and Pelagophyceae were the most abundant phytoplankton groups. Distinct phytoplankton communities were observed in the BS and the YS: offshore stations were dominated by bloom forming genera Thalassiosira and Skeletonema, while brown tide-forming species including Chrysochromulina spp. and Aureococcus anophagefferens were commonly found in the nearshore areas. Redundancy analysis showed that phosphate, temperature and silicic acid play key roles in structuring chromophytic phytoplankton, such as phytoplankton at nearshore stations were affected by nutrient runoff from adjacent rivers (Yellow River). Anthropogenic activities in the Bohai Sea and seasonal circulation of ocean currents may also contribute to shaping chromophytic phytoplankton communities. This study provides data support and foundational observations of chromophytic phytoplankton in the BS and the YS, and their responses to environmental gradients and human activities.

Gambierdiscus and Its Associated Toxins: A Minireview.

Gambierdiscus is a dinoflagellate genus widely distributed throughout tropical and subtropical regions. Some members of this genus can produce a group of potent polycyclic polyether neurotoxins responsible for ciguatera fish poisoning (CFP), one of the most significant food-borne illnesses associated with fish consumption. Ciguatoxins and maitotoxins, the two major toxins produced by Gambierdiscus, act on voltage-gated channels and TRPA1 receptors, consequently leading to poisoning and even death in both humans and animals. Over the past few decades, the occurrence and geographic distribution of CFP have undergone a significant expansion due to intensive anthropogenic activities and global climate change, which results in more human illness, a greater public health impact, and larger economic losses. The global spread of CFP has led to Gambierdiscus and its toxins being considered an environmental and human health concern worldwide. In this review, we seek to provide an overview of recent advances in the field of Gambierdiscus and its associated toxins based on the existing literature combined with re-analyses of current data. The taxonomy, phylogenetics, geographic distribution, environmental regulation, toxin detection method, toxin biosynthesis, and pharmacology and toxicology of Gambierdiscus are summarized and discussed. We also highlight future perspectives on Gambierdiscus and its associated toxins.

Regional distribution and environmental regulation mechanism of nitrous oxide in the Bohai Sea and North Yellow Sea: A preliminary study.

Nitrous oxide is one of the most powerful greenhouse gases and can destroy the ozone layer through photochemical reactions. In 2019, we conducted three cruises to study the spatial and temporal variability of N2O distribution and emissions in the Bohai Sea (BS) and North Yellow Sea (NYS), and analyzed the regional sources and sinks. The maximum average N2O concentrations were observed in the summer, followed by autumn, while the minimum was observed in the spring. The N2O concentration decreased in a gradient from the estuary to the continental shelf, particularly in summer, which indicated that the riverine input from the estuary was a strong source of N2O in the Bohai Sea. Due to the vertical mixing of the water column, the vertical distribution of N2O was moderate in autumn, while the bottom remained a hotspot for N2O emissions in spring and summer. The generalized additive model (GAM) showed that the temperature, salinity, DO and pH were strong predictors of N2O in the BS and NYS. Excess N2O concentrations were positively linearly correlated with the apparent oxygen utilization and NO3- concentrations, which suggested that nitrification was the dominant process of in situ N2O production in the BS and NYS. The mixing of water masses, especially DW (diluted water) and BCW (Bohai Sea coastal water), provided a significant amount of N2O to the entire shelf area of the BS. In addition, the coastal input was a dominate pusher of N2O emissions in the estuarine region. Overall, the annual N2O emissions from BS and NYS were approximately 1.72 × 10-2 Tg yr-1, which accounted for 0.51% of the annual global marine N2O emissions, but only 0.04% of the total area of the world's oceans. Hence, both the BS and NYS acted as N2O sources to the atmosphere.