Toxic effects, mechanisms, and ecological impacts of harmful algal blooms in China.

Over the last 30 years, harmful algal blooms (HABs) have occurred frequently in the coastal waters of China, resulting in financial losses of over 5.9 billion yuan (about 0.87 billion US dollars) due to massive fish and shellfish mortalities and negative impacts on tourism. To better understand HABs in China, herein we summarized bloom events with massive fish/shellfish mortalities and/or economic losses. Our results suggest that the diversity of HAB species has increased over the last 30 years, with the main causative species shifting from the raphidophyte Chattonella marina and dinoflagellates Gymnodinium spp. to various other species, including the dinoflagellates Karenia mikimotoi and Prorocentrum donghaiense, the haptophyte Phaeocystis globosa, and the pelagophyte Aureococcus anophagefferens. In addition, new types of HABs, such as macroalgal blooms, emerged with severe ecological impacts. We also reviewed the toxic effects, mechanisms, and ecological impacts of common HAB causative species in China. Analysis of the toxic effects of three types of harmful algae (toxin-producing, fish killing, and ecosystem disruptive algae) on marine organisms commonly found in China at different trophic levels revealed that HABs often had toxic effects on multiple organisms in addition to fish or shellfish, with species-specific impacts. Common mechanisms of intoxication include shifting environmental parameters, shellfish poisoning, reactive oxygen species, and haemolytic/cytotoxic toxins. The main mechanism appears to vary with the type of HAB species, and for some notorious algae such as K. mikimotoi and C. marina, further investigations are needed to identify their intoxication mechanism.

[Three-dimensional fluorescence characteristic of dissolved organic matter in marine mesocosm experiment in Jiaozhou Bay, China].

The three-dimensional fluorescence of dissolved organic matter in the mesocosm with different nutrients enrichment experiments in Jiaozhou Bay was determined by using excitation-emission matrix spectrum. The result indicates that phytoplankton can produce protein-like and humic-like fluorescent matter. The protein-like fluorescence is composed of tyrosine-like fluorescence and tryptophan-like fluorescence. The main position of protein-like fluorescent peak is Ex(max)/Em(max) = 270 nm/290 - 310 nm. The fluorescent intensity of the peak located in Ex(max/ Em(max) = 270 - 290 nm/320 - 350 nm is less. The centers of humic-like peaks disperse at Ex(max)/Em(max) = 250 - 260 nm/380 - 480 nm (Peak A), Ex(max)/Em(max) = 310 - 320 nm/380 - 420 nm(Peak C) and Ex(max)/Em(max) = 330 - 350 nm/420 - 480 nm(Peak M) in which peak A is the main peak. The fluorescent intensity of tyrosine-like matter is stronger than the intensity of humic-like matter. When the amount of phytoplankton decreased, the fluorescent intensity of tyrosine-like matter has negative relativity with the chlorophyll-a concentration. Tyrosine-like matter and tryptophan-like matter have similar origin. Dinoflagellate can produce more protein-like fluorescent matter than diatom. The composition ratios of humic-like mixture are different in different environment. And it has a small A/C value in dinoflagellate environment compared to diatom environment.