As a natural androgen, androstenedione (AED) may pose potential risks to aquatic organisms due to its ubiquitousness in aquatic environments. Here we assessed the adverse effects of AED on histology of gonads, as well as mRNA expression levels of 34 genes concerned with hypothalamic‐pituitary‐gonadal (HPG) axis, germ‐cell differentiation and sex differentiation in zebrafish (Danio rerio). Adult zebrafish were exposed to solvent control and three measured concentrations of 0.2, 2.3 and 23.7 μg/L AED for 60 days. The results showed that AED did not induce any obvious histological effects in the ovaries and testes. Of the investigated genes, transcriptional expression levels of amh and cyp11c1 genes in the ovaries of females were significantly increased by AED at 2.3 or 23.7 μg/L. However, different exposure concentrations of AED significantly inhibited mRNA expression of gnrh3, atf4b1 and cyp19a1b in the brain of males. In the testes of males, AED at 2.3 μg/L led to a significant induction of sox9b gene, but it at 23.7 μg/L down‐regulated nr5a1b gene. These observed transcriptional changes indicated that AED could pose potential androgenic effects in zebrafish.

Dissolved oxygen (DO) is an important parameter for evaluating the seawater quality of the oce-anic environment, but the distribution of DO and its possible mechanisms of marine environ-mental regulation are less studied. Here, the spatial distribution of DO and the influence of main environmental factors on DO were explored using in-situ observation data collected in the northern coastal waters of the Beibu Gulf in April 2021, based on cluster analysis, partial correla-tion analysis, and multiple linear regression. The results showed that DO in surface water of the study area gradually increased from nearshore to offshore, with the nearshore’s DO being nearly saturated and the offshore supersaturated. Tieshan Port and the Maowei Sea had the lowest degree of DO saturation. The partial correlation analysis between DO concentration and environmental factors revealed that the distribution of DO concentration was mainly influenced by temperature and salinity as well as other biochemical factors (i.e., chlorophyll-a, turbidity, and pH). Significant differences existed between the dominant factors in various parts of the northern Beibu Gulf. The western river (Beilun River, Fangcheng River, Maoling River, Qinjiang River) estuaries and offshore areas were dominated by photosynthesis, while the eastern river (Fengfeng River, Nanliu River) estuaries were dominated by oxidation-decomposition. In addition, DO was also affected by the mangrove ecosystem, aquaculture, and coastal industry.

In the era of information explosion, mobile data is developing rapidly, and many fields are facing the challenges of data collection, analysis and operation. Heterosigma akashiwo is a kind of wide temperature and wide salt algae, belonging to the class Echinococcus and the genus heterobenthos. It is widely distributed in the coastal waters of the world. It has formed harmful red tides for many times in many countries, causing a large number of fish deaths, causing great economic losses and serious damage to aquatic resources. If toxic red tides break out frequently, they will pose a great threat to public health. Seawater eutrophication is the main environmental inducement for the formation of red tide by Heterosigma akashiwo. In particular, the content of nutrients in seawater significantly affects the reproduction of Heterosigma akashiwo and the excessive proliferation of plankton such as algae. At the same time, a large number of planktons will devour the dissolved oxygen in the water, thus affecting the photosynthesis of the water body, resulting in the deterioration of the water quality and the damage to the functions of ecology and water resources. As for the effects of nitrogen, phosphorus, iron and different vitamins on the growth of Heterosigma akashiwo, this paper takes Heterosigma akashiwo as the research object, and focuses on the analysis of the effects of ammonium chloride, urea and sodium dihydrogen phosphate on the proliferation of Heterosigma akashiwo. e results showed that the higher or lower the concentration of nitrogen and phosphorus, the slower the proliferation rate of Heterosigma akashiwo; Heterosigma akashiwo had the maximum proliferation rate under the nitrogen concentration of 300-500 μmol/L; At the concentration of 10∼15 μmol/L phosphorus, its growth rate is the fastest and its proliferation level is the highest. e selected nitrogen and phosphorus have a very significant impact on the proliferation of microalgae.