The Toxic Effects Of Tributyltin Coupling With Environmental Factors On The Marine Maroalgae, Ulva Fasciata Delile

Organotin compounds, especially tributyltin (TBT) have been widely used as a biocide agent in antifouling paints of ship hulls, resulting in heavy pollution in coastal waters. Now, it has been proved that these chemicals can pose serious threats to marine animals and human beings. However, very few data are available about the effects on marine macroalgae, which is also one important member of the coastal ecosystem. Actually, TBT has been demonstrated to reduce growth and photosynthesis of marine algae even in a very low level. What's more, availabilities of nitrogen and phosphorus in seawater are known to affect algal physiological behaviour. The aim of this study was to investigate the combined effects of TBT and nutrients or salinity on the economic green seaweed Ulva fasciata Delile. The findings were as the follows:1)Growth and pigment content were not significantly affected at low TBT concentration (≤2μg/L), while significant increase in photosynthesis was recorded at 2μg/L. Irreversible metabolic damage of Ulva fasciata Delile was aroused at higher concentration (≥10μg/L). Physiological damages were found as a result of increase in reactive oxygen species production. The electron transport was significantly hampered when exposed to TBT with 25μg/L concentration at day 3. The superoxide dismutase activity (SOD) and superoxide anions were significantly enhanced when exposed to 10μg/L after 7 d incubation, but excessive TBT concentration (25μg/L) could destroy antioxidative enzyme system, which lead to decrease in SOD, CAT.2)In expereiment of TBT coupled with nutrient, we found both nutrient (nitrogen and phosphorous) and TBT both can throw significant effects on carotenoid, NR and superoxide anions. Significant increases in photosynthesis, dark respiration rate and algal growth were recorded with high nitrate concentration than those with environment nitrate concentration when TBT concentration at 25μg/L on 3^rd day and 0.5μg/L on 7^th day, and the same situation was also found in high phosphate vs environmental phosphate when TBT concentration at 25μg/L on 3^rd day and 10μg/L on 7^th day. Enrichment of nitrogen and phosphorus can provide growth signal and stimulation of algal growth controlling gene synthesis, along with promoting formation and transformation of germ cells as well as enzymatic activity, so that Ulva fasciata Delile could grow fast, which indicated that thallus had higher ability to resist the toxicity of TBT when exposing to elevated nutrient conditions.3)In expereiment of TBT coupled with salinity, TBT and salinity had different impacts with the exposure dutationstage. Algal growth, chla, and CA activity at day 1 were significantly affected with either TBT or low salinity treatment, and significant changes in growth, Yield, car, CA and SOD activities were also found at day 3. Moreover, these two factors can significantly impact growth, chla, car after 7d culture. It is showed that algal growth, photosynthesis, dark respiration rate, pigments content and CA activity were all affected under low salinity vs environment salinity after 7d cultivation. SOD activities and MDA content exposed to 2μg/L of TBT concentration at day 3 significantly changed under low salinity compared to environment salinity.In summary, the enrichment of nitrogen, phosphorus and the decrease of salinity can affect the physiological responses of Ulva fasciata Delile to TBT. Generally, nitrogen, phosphorus supplies and proper salinity can soothe the inhibition induced by TBT and relieve its negative effects on the green alga.