# Laminar _Ulva_ Species: A Multi-Tool for Humankind?
## 2 The Biology of _Ulva_ sp.
### Nutrients  
The nutrients required for seaweed growth can be found in seawater; however, they are often concentrated in plant tissue and can be divided into three categories: micronutrients or trace elements (e.g., Fe, Zn, Cu, Mn, etc. ); vitamins (B\({}_{12}\), thiamine, and biotin);and macronutrients (e.g., N, P, C, etc.). Seaweed concentrates nitrogen and phosphorus about 100,000 times [54]. Nitrogen is a key cofactor in cellular anabolic activities that produce amino acids, including nicotinamide adenine dinucleotide phosphate (NADP\({}^{+}\)). Phosphorus has a similar role in nucleic acid production and promotes photosynthesis, nutrition transport, and energy transmission via energy-rich adenosine triphosphate (ATP) linkages [54]. The optimal ratio refers to the amount of nutrients necessary for maximum plant development. The typical ratio for seaweed is 30N:1P, ranging from 10:1 to 80:1. When an excessive amount of a nutrient is delivered, the nutrient becomes a \"limiting factor.\" Chemical variables, such as nutrient content and the type of the inorganic nutrient (e.g., non-ionized ammonium nitrate NO\({}_{3}\)\({}^{-}\) or ionized ammonia NH\({}_{4}\)\({}^{+}\)), can influence absorption rates [54]. Some marine algae can absorb NO\({}_{3}\)\({}^{-}\) and NH\({}_{4}\)\({}^{+}\) simultaneously and in equal proportions, but most prefer to assimilate NH\({}_{4}\)\({}^{+}\), as is the case with _U. lactuca_. When nitrate is ingested, it can be retained intracellularly in the vacuole and cytoplasm or converted to nitrite by the enzyme nitrate reductase. Nitrite is transferred from the cytoplasm to the chloroplasts and converted to ammonia by the enzyme urease. Ammonium is taken up or transformed into amino acids by glutamine synthetase in chloroplasts [54]. [PERSON] [88] observed three phases of NH\({}_{4}\)\({}^{+}\) uptake (first observed by [PERSON] et al. [89]) in _U. lactuca_. These phases are epidemics that are managed both within and outside. When the absorption rate was several times higher than the growth rate, they referred to it as a \"surge\". This increased absorption rate enables the cell to \"catch up\" on its earlier nutritional shortage by absorbing the limiting material much quicker than required for development. For these reasons, it is critical to acclimate wild samples in order to homogenize any differences in nutrient absorption or needs. It should be noted that some nutrient-limited algae exhibit a decline in nutrient absorption over time after being introduced to saltwater. As a result, while performing research, it is critical to document the duration of nutrient measurements. It has been shown for _Ulva_ spp. that NH\({}_{4}\)\({}^{+}\) absorption rates decrease by 50% in the dark compared to light [54]. [PERSON] et al. [81] intended to evaluate the influence of light and phosphorus (PO\({}_{4}\)-P) on the germination and growth of _Ulva intestinalis_ spores; three light intensity levels (20, 40, and 90 \(\mu\)E m\({}^{-2}\)s\({}^{-1}\)) and three PO\({}_{4}\)-P levels (6.4, 2, and 0.8 \(\mu\)mol L\({}^{-1}\)) were combined and three levels of NH\({}_{4}\)-N (102.4, 32, and 12.8 \(\mu\)mol L\({}^{-1}\)). They noted that spore biomass increased with light and PO\({}_{4}\)-P concentration and the interaction between these factors was slightly statistically significant; that is, at a PO\({}_{4}\)-P concentration of 6.4 \(\mu\)mol L\({}^{-1}\), spore biomasses increased when subjected to 40 and 90 \(\mu\)Em\({}^{-2}\)s\({}^{-1}\)[81]. Regarding NH\({}_{4}\)-N, the spore biomass was inversely proportional to the concentration: the biomass of algal spores tended to decrease with increasing NH\({}_{4}\)-N concentrations. The highest salinity tested (35 PSU) together with the lowest concentration of NH\({}_{4}\)-N allowed a greater spore biomass and, consequently, a higher growth rate [81]. [PERSON] et al. in 2017 [87], when working with eight thalli (five wild type and three sterile mutants) of _U.