Using historical and 2010 field data, the distribution of nutrients in the northern Beibu Gulf of China is described. There was a decreasing trend in the concentration of nutrients from the north coast to offshore waters of the northern Beibu Gulf, reflecting the influence of inputs from land-based sources. High concentrations of dissolved inorganic nitrogen(DIN) and phosphate(PO 4-P) occurred mainly at Fangchenggang Bay, Qinzhou Bay, and Lianzhou Bay. Four different methods were used to assess eutrophication. The trophic status of the Beibu Gulf was characterized using the single factor, Eutrophication index(EI), Trophic index(TRIX) and Assessment of Estuarine Trophic Status(ASSETS) methods. Based on nutrient concentrations, 73.9% of DIN and 26.7% of PO 4-P samples exceeded the fourth grade Seawater Quality Standard of China. Eutrophication index values varied widely, but higher levels of eutrophication were generally found in bays and estuaries. TRIX values ranged from 2.61 to 7.27, with an average of 4.98, indicating a mesotrophic and moderately productive system. A positive correlation between TRIX and harmful algal species richness and abundance was observed. The ASSETS model evaluates eutrophication status based on a Pressure-State-Response approach, including three main indices: influencing factors, overall eutrophic condition, and future outlook. The Beibu Gulf was graded as moderate using ASSETS. The single factor and Chinese nutrient index methods were considered inadequate for the assessment of trophic status. TRIX can be used as an indicator of trophic state and ASSETS showed good potential to assess eutrophication. The results of TRIX and ASSETS depend on threshold values. To establish these values, further research is required within the northern Beibu Gulf.
Two new compounds, namely taenialactam C and globorin A(1 and 2), as well as six known compounds,cornoside(3), 2-phenylethyl-b-D-glucoside(4), 3-isopropyl-5-acetoxycyclohexene-2-one-1(5), 4-methyl-phenol(6), 5-[(2S)-2-aminobutyl]-2-methyl-phenol(7), and 1-(4-methylphenyl)-1-propanone(8) were isolated from wild Phaeocystis globosa. The structures of the new compounds were established by detailed spectroscopic analysis and by comparison with spectral data of related known compounds.The structures of the known compounds were identified by comparing their spectroscopic data with those reported in the literature. This paper also reports toxicity properties of the eight compounds against the brine shrimp Artemia salina and juvenile Epinephelus akaara fish. Some of these compounds showed significant lethality on the brine shrimp A. salina and the juvenile E. akaara fish.
