Influence of photodegradation on the removal of color and phenolic compounds from palm oil mill effluent by Arthrospira platensis.

Palm oil mill effluent (POME) released from conventional treatment systems poses severe environmental problems due to its dark color, its high chemical oxygen demand (COD), and high content of phenolic compounds. However, the possible biodegradation of phenolic compounds and color by microalgae was not well explored. This research aimed to reveal optimal conditions for pollutant removal through biodegradation by the cyanobacterium Arthrospira platensis. This species was grown under a range of POME fractions and environmental conditions (irradiance, salinity, nutrients) during which growth, final biomass, color, COD, and phenolic compound levels were followed. POME fractions influenced A. platensis growth rate, final biomass, COD, and color removal. The optimization of phenolic compound removal by using central composite design (CCD) response surface methodology (RSM) showed that low light and high initial phenolic compounds promoted the activity of A. platensis to degrade phenolic compounds. The combination of high initial phenolic compounds and high light intensity increased the growth rate up to 0.45 days −1 and final biomass up to 400 mg L −1, while total phenolic compounds were almost completely (94%) removed. Finally, this study showed that phenolic compounds and color degradation from POME were dominated by the activity of photodegradation at high irradiance, while the activity of A. platensis dominated at low light intensity

Mediterranean alien harmful algal blooms:Origins and impacts

Harmful algal blooms (HABs) are mostly phytoplankton blooms, which have detrimental environmental and socioeconomic impacts. The Mediterranean Sea due to its enclosed nature is of special concern since it has an enormously rich native biodiversity. Though, it is also the world's most invaded marine ecosystem and is considered at very high risk of future invasions. The aim of this review study is to explore the origins, establishment, environmental, and socioeconomic impacts of HABs caused by nonnative algal species in the Mediterranean Sea. Based on this, it is also discussed whether HABs form an increasing threat in the basin, and what could possibly be done to prevent or to minimize their impacts. The increasing rate of their introduction and the harmful impacts that they have on the environment, economy, and human health makes it important to have accurate knowledge about HABs. Anthropogenic activities and climate change are considered the main contributors of alien invasions but also the main enablers of HAB events. Mediterranean HABs are adequately studied, but there are no studies purposefully concerning invasive microalgae species in the basin. In the present study, 20 species have been identified, and an attempt has been made to collect their introduction information, as well as known or suspected impacts. Future research should be focused on data mining, current legislation updates, and monitoring of Mediterranean coastlines

Acclimation to a dynamic irradiance regime changes excessive irradiance sensitivity of Emiliania huxleyi and Thalassiosira weissflogii

Effects of fluctuating irradiance regimes on excessive photosynthetically active radiation (PAR) and ultraviolet (UV) radiation sensitivity were assessed for Emiliania huxleyi (Lohman) and Thalassiosira weissflogii (Grunow) Fryxell and Hasle. Cultures acclimated to low irradiance were subjected to two irradiance regimes of equal daily dose: dynamic irradiance simulating vertical mixing within the water column and constant irradiance. For each regime two irradiance levels were studied. Growth was monitored for 3 d, after which pigment composition was determined. Next, excessive PAR and UV sensitivity was measured by studying viability loss during 4-h exposure to simulated surface irradiance (SSI). Furthermore, the effects of inhibition of D1 reaction center protein turnover were investigated by incubating samples with lincomycin prior to exposure. Dynamic irradiance reduced growth rates of both species as compared to constant irradiance. Pools of light-harvesting pigments increased in dynamic irradiance, whereas the protective pigment pools decreased compared to constant irradiance. Excessive irradiance sensitivity was enhanced in cells grown in fluctuating irradiance. Furthermore, viability loss was most pronounced in UV treatments combined with lincomycin. E. huxleyi was more sensitive to excessive irradiance than T. weissflogii, which coincided with a lower ratio between protective and light-harvesting pigments in the former species. Irradiance modulation by deep vertical mixing influences growth, pigment composition, and excessive PAR and UV sensitivity within days