This work aims to measure the role of zinc as an essential micronutrient for algal growth and the effect of using different concentrations of this heavy metal on growth and essential metabolites of Dunaliella tertiolecta. The EC50 obtained was around 15 mg/l. The results obtained proved that lower concentrations of the element increased growth and the content of the measured metabolites (photosynthesis pigments, fatty acids, and protein) but with different responses. The increase in content of these metabolic products with low concentrations of the tested heavy metal may be attributed to inhibition to these metabolites’ export out of cells by heavy metals. The obtained infrared peaks of the major cell constituents of the treated cells revealed the emergence of new peaks and the removal of others, indicating changes in cell constituents due to changing zinc concentrations.

The runoff of textile dye effluents into public water bodies is a major environmental and health problem. Color removal, in particular, has recently become of substantial scientific interest, as revealed by the multitude of related research reports. The present study focused on measuring the efficiency of two marine algae, Ulva fasciata and Pterocladia capillacea, in bio-removal of four synthetic dyes (RY2, RR195, RB19, and RB5) based on the fresh and dried biomass of the tested algal species. According to the highest removal efficiencies of the dyes, two algal species were chosen from among nine different algae. Bio-removal efficiency was examined under the effects of salinity and contact time. The results of this experiment revealed that algae achieved high bio-removal efficiency of the examined dyes in both fresh and saline water, but the removal percentages were higher in saline water compared to fresh conditions. The highest removal percentage recorded after 8 h by fresh U. fasciata in saline water reached 82.75 and 83.23% for RY2 and RR195 dyes, respectively. Contact time has the highest impact on dye removal in both algal species. The highest removal values were obtained in the case of dried U. fasciata, which achieved impressive removal percentages that reached 100% for RB195 and RB5 and fresh P. capillacea which had high removal percentages of 91.11, 94.85 and 97.13% for RR195, RB19, and RB5 dyes, respectively, after 8 h. Our results revealed that the used algal species were highly significant in the biosorption of most used dyes.

In all living cells, phosphorus plays an important function in the transport of metabolic energy and as a structural component of nucleotide and phospholipid molecules. Ni²⁺ is found in industrial water effluent and has the potential to harm aquatic ecosystems. The study was designed to assess the effect of phosphorous-limiting conditions in combination with the absence or presence of different concentrations of nickel on growth, pigment content, photosynthesis, and respiration activities of the studied alga Dunaliella tertiolecta. The EC₅₀ for dissolved nickel was around 15 mg/L. Results obtained showed that, growth and chlorophyll content under phosphorus limiting conditions increased under low concentrations of dissolved nickel. The amount of O₂-evolution with phosphorus limiting conditions was lower than those of untreated normal cultures. Lower dissolved nickel concentrations resulted in higher photosynthesis rates in the treated phosphorus-starved cultures than higher concentrations. The degree of response to metal toxicity in phosphorus-starved medium is depending mainly on the concentration of the element and the length of the culturing period and it was less than those in normal control culture containing phosphorus.

Preventing fouling is crucial for maintaining ship performance, as it reduces speed, increases fuel consumption, raises greenhouse gas emissions, and spreads invasive species. Irgarol 1051, an antifouling agent (2, methythiol-4, tert-butylamino, 6-cyclopropylamino, s-triazine), is a toxic compound that impacts various marine species. It inhibits algal growth and disrupts key metabolites, posing a threat to the marine ecosystem. This study aimed to assess the toxic effects of Irgarol 1051 on Chlorella salina and Dunaliella bardawil, two nutrient-rich marine algae commonly used in fish feed. In addition, the suitability of the Mediterranean Sea coast for algal proliferation was assessed using geospatial techniques. The data were statistically examined using a two-way ANOVA test. Lethal and sublethal effects of Irgarol 1051 were measured in the laboratory to identify the consequences of this biocide on certain metabolite compositions. EC50 for C. salina and D. bardawil was estimated to be 0.50 µg·L⁻¹ and 0.025 µg·L⁻¹ respectively. IR spectroscopy of total cell constituents, protein profile, and the damaging effects of antioxidants have been evaluated for the two algal species. The findings of this study revealed that Irgarol 1051 negatively affected all the examined metabolites in both algal species, with more pronounced impacts on the wall-less alga Dunaliella bardawil compared to the walled alga Chlorella salina. A notable increase in total antioxidants was observed in both algae as the Irgarol concentration increased. The study reveals high algal growth areas near the Nile Delta along the Egyptian coast, potentially vulnerable to the effects of Irgarol 1051 due to nutrient runoff and eutrophication. The spatial analyses showed that the growth of C. saline and D. bardawil in Egyptian seawater is high in front of the Nile delta governorates: Port Said, Damietta, and Dakhalia shores reporting 6, 4.5, and 4 mg·m⁻³, respectively. The level of mass chlorophyll “a” in front of the Egyptian northern governorates can be ordered as follows: Port Said > Damietta > Dakahlia > North Sinia > Kafr El-Sheikh > Alexandria > Matrouh. This study highlights the use of spatial analyses to assess algal distribution, pollution impact, and ecosystem vulnerability along the Egyptian Mediterranean coast for effective environmental management.

Biological monitoring of inhibitory effects of antifouling agent Irgarol 1051 on growth and essential metabolites of marine alga Chlorella salina