## 4 Discussion
Moreover, minor peaks detected in other regions (e.g., 1020-1100 cm\({}^{-1}\)) may correspond to C-O stretching in alcohols and polysaccharides, further substantiating the carbohydrate-rich nature of the material [87]. The natural environment provides a wide range of elements that are essential for the survival and functioning of living organisms. In addition, the environment also contains heavy metals, which can play a dual role, either supporting biological functions or causing toxicity [88]. Heavy metals are present in the environment from natural or anthropogenic sources, including industrial effluents, organic waste, waste burning, and transport and power generation. As seaweed can absorb these hazardous compounds in large quantities, their consumption can lead to the intake of these contaminants [89]. As mentioned above, the levels of arsenic found in most of our samples were rather high compared to the levels mentioned in Commission Regulation (EU) No. 465/2023 [90], which recommends a maximum level of inorganic arsenic between 10 and 300 ug\(\cdot\)kg\({}^{-1}\) of wet weight. These values are within the range reported by [PERSON] and coworkers [91] for Phaeophyceae, usually the group with the highest arsenic concentration among seaweeds. However, the most common types of arsenic found in seaweed are arsenic sugars, which are believed to be like arseno-betaine in that they are harmless to the human body [92]. On the other hand, other authors point out that arsenic can be converted by mammals into toxic dimethylacetamide, a carcinogenic compound [93]. To assess the food safety of these algae, it is therefore necessary to obtain new data on the levels of organic and inorganic arsenic in the seaweeds and kelp pulp biomass. Regarding macro- and microelements, the values recorded in the present study are generally in line with those reported by [PERSON] et al. [6] for brown algae, although, as mentioned above, large variations were recorded depending on the location, season and other environmental parameters. Seaweeds are usually rich in macroelements, making them valuable dietary sources of essential nutrients. These nutrients are needed to produce metabolites and cellular metabolism. However, the recommended daily intake of seaweed is between 5 and 10 g dw per day [94]. Hence, the macro- and microelements are found at lower levels than the dietary reference values [95], as only small amounts of seaweed can be consumed daily. Like all photosynthetic organisms, brown algae contain chlorophyll \(a\). These organisms also have other accessory pigments. In addition to chlorophylls _c1_ and _c2_, they are rich in fucoxanthin and other carotenoids. Together, these pigmented metabolites give these algae their yellowish-brown or dark brown colour. These natural pigments, regardless of their source, can be used in the food, cosmetic and pharmaceutical industries [12] as they have antioxidant, anti-inflammatory, antidiabetic, antiobesity, neuroprotective, anticancer and photoprotective properties [75]. The quantification of these pigments hence helps to determine the biotechnological potential of these samples. The analysis of pigment profilesin both fresh and dried macroalgal biomass revealed species-specific differences and notable changes induced by biomass drying. Fresh samples of _L. ochroleuca_ and _S. polyschides_ gave the best results for both fucoxanthin and chlorophylls \(a\) and _c_[96]. Freeze-thawing of fresh samples reduces molecular movement and promotes the formation of ice crystals, which can lead to membrane rupture due to hydrogen bridge dissociation [73]. In the fresh samples, _S. polyschides_ consistently exhibited the highest concentrations of photosynthetic pigments, with chlorophyll \(a\) reaching 4218.74 \(\pm\) 93.53 \(\upmu\)g\(\cdot\)g\({}^{-1}\) fw, significantly higher than the value in _L. ochroleuca_ (2599.38 \(\pm\) 701.51 \(\upmu\)g\(\cdot\)g\({}^{-1}\) fw). This dominance of chlorophyll \(a\) in _S.