Physiological and ultrastructural responses of the brown seaweed Undaria pinnatifida to triphenyltin chloride (TPTCL) stress.

Triphenyltin chloride (TPTCL) is a well-known marine pollutant that may constitute major environmental threats to seaweed mariculture. In the present study, the toxic effects of TPTCL on physiology and ultrastructure of cultivated sporophytes of Undaria pinnatifida were investigated under different TPTCL concentrations ranging from 0 to 100 µg L-1. Significant negative effects of increased TPTCL concentration were detected in the relative growth rates, survival percentages and chlorophyll a contents of young and adult sporophytes. Low TPTCL concentrations could significantly stimulate the activities of enzymes related to nitrogen metabolism. The chloroplast, mitochondria and nucleus inside cells were greatly damaged by TPTCL. Meanwhile, significant increases of electron dense deposits and physodes were found. Additionally, young sporophytes exhibited greater tolerance to TPTCL stress than adult sporophytes. The results of this study indicate that coastal TPTCL pollution could reduce the productivity and quality of cultivated U. pinnatifida.

Effects of Cobalt on Spore Germination, Gametophyte Growth and Gametogenesis of Undaria pinnatifida (Phaeophyceae).

With rapid development of the construction of nuclear power plants along the coast, the concern of negative effects of potentially unexpected release of nuclides on marine organisms has increased. Cobalt (Co) is one of the crucial nuclides in nuclear polluted seawater. The effect of its presence in seawater on life cycle of macroalgae has seldom been studied. In this investigation, a series of Co concentrations including 1, 10, 100 µg L-1, and 1, 10 mg L-1 (the background concentration of Co in culture seawater was determined to be at the level of 0.75 ± 0.11 µg L-1) were used to test the effects of their presence on spore germination, gametophyte growth and gametogenesis of the important brown macroalga Undaria pinnatifida. It was found that the spore germination rate of 10 mg L-1 group was significantly lower than that of the control group after 1- and 2 days exposure. The gametophyte sizes of 1 and 10 mg L-1 groups were much smaller than that of the control group after 6- and 12-days exposure. Oogonia and juvenile sporophytes were observed to appear in 1, 10 µg L-1 and the control groups after 12 and 15 days, respectively, but not in the higher concentration groups. In the recovery test, sporophytes appeared in the 100 µg L-1 group on the 5th day, but not in 1 and 10 mg L-1 groups. These results demonstrate that presence of Co at high concentrations in seawater disturbs the life cycle by suppressing both the gametophyte growth and gametogenesis in U. pinnatifida.

Copper pollution exacerbates the effects of ocean acidification and warming on kelp microscopic early life stages.

Ocean warming (OW), ocean acidification (OA) and their interaction with local drivers, e.g., copper pollution, may negatively affect macroalgae and their microscopic life stages. We evaluated meiospore development of the kelps Macrocystis pyrifera and Undaria pinnatifida exposed to a factorial combination of current and 2100-predicted temperature (12 and 16 °C, respectively), pH (8.16 and 7.65, respectively), and two copper levels (no-added-copper and species-specific germination Cu-EC50). Meiospore germination for both species declined by 5-18% under OA and ambient temperature/OA conditions, irrespective of copper exposure. Germling growth rate declined by >40%·day-1, and gametophyte development was inhibited under Cu-EC50 exposure, compared to the no-added-copper treatment, irrespective of pH and temperature. Following the removal of copper and 9-day recovery under respective pH and temperature treatments, germling growth rates increased by 8-18%·day-1. The exception was U. pinnatifida under OW/OA, where growth rate remained at 10%·day-1 before and after copper exposure. Copper-binding ligand concentrations were higher in copper-exposed cultures of both species, suggesting that ligands may act as a defence mechanism of kelp early life stages against copper toxicity. Our study demonstrated that copper pollution is more important than global climate drivers in controlling meiospore development in kelps as it disrupts the completion of their life cycle.

Production of biodiesel from carbon sources of macroalgae, Laminaria japonica.

As aquatic biomass which is called "the third generation biomass", Laminaria japonica (also known as Saccharina japonica) consists of mannitol and alginate which are the main polysaccharides of algal carbohydrates. In this study, oleaginous yeast (Cryptococcus curvatus) was used to produce lipid from carbon sources derived from Laminaria japonica. Volatile fatty acids (VFAs) were produced by fermentation of alginate extracted from L. japonica. Thereafter, mannitol was mixed with VFAs to culture the oleaginous yeast. The highest lipid content was 48.30%. The composition of the fatty acids was similar to vegetable oils. This is the first confirmation of the feasibility of using macroalgae as a carbon source for biodiesel production.