# Pharmacological and Cosmeceutical Potential of Seaweed Beach-Casts of Macaronesia
## 1 Introduction  
Beach-cast seaweeds, consisting in the accumulation of large amounts of algae detached from the bottom of the sea or coast platforms, are documented on beaches of many coasts around the world [1; 2]. This is a natural and seasonal phenomenon which is mainly influenced by climate, wind conditions, eutrophication, and more importantly, the occurrence of considerable wave episodes; due to climate change, the number of beach-casts has been increasing dramatically over recent years [3; 4].  
The biomass deposited during beach-cast phenomena is unpleasant for beach users and affects the tourism industry [5; 6], mainly because tourists often interpret stranded natural litter as lowering beach quality, especially if the material starts to decompose [7]. The beach-cast phenomenon has a huge impact in the Canary Islands (Spain), particularly on the island of Gran Canaria, which receives many swimmers, visitors and holidaymakers all year round, where rotting seaweed masses can become a nuisance affecting local businesses and the tourism industry. To understand the magnitude of this phenomenon, the amount of seaweed beach-casts varies from 400 to 1200 tons per year in Las Canteras beach in Grand Canaria, occurring with more incidence from November to March [8]. These beach casts are always variable mixtures of different species of seagrass and seaweed, and in the case of Gran Canaria island, the main species were reported to be _Cymodocene nodosa_ (Angiosperm), _Cymopolia barbata_ (Chlorophyta), _Haloptiphys incurva_ (Rodophyta), _Halopteris scoparia_ (formerly _Stypocaulon scoparium_), _Lobophora variegata, Teptacantha abies-marina_ (formerly _Cystoseira abies-marina_), _Dictyota_ sp. (Ochroophyta, Phaeophyceae), with _L. variegata_ being the most frequent and abundant seaweed [8].  
The management of all the biomass from a single beach-cast is difficult and costly, and, most of the time, the solution is to collect it from the beach and to dispose of it in landfills without further studies or valorization. However, seaweeds are gaining increasing attention in many industries like fuel, plastics, cosmetics, pharmaceutical, and food, essentially because they produce a wide variety of structurally and functionally diverse metabolites [9; 10]. These compounds display attractive biological activities (i.e., antioxidant, antimicrobial, anticancer, etc.) with various applications, many of which are already commercially exploited [10; 11; 12]. Due to all potential applications of seaweeds and their metabolites, it is illogical to waste this valuable biomass; in fact, the biomass obtained from beach-cast holds a large interest, and some works have proved that it can be valorized as a source of biochemicals, feed, food, fertilizer and fuel [13; 14].  
In view of the above-mentioned, the present work evaluated samples from different beach-casts with distinct seaweed composition, assaying several biological activities of crude and fractionated extracts, aiming to establish new potential applications to valorize seaweed beach-cast biomass converting it into new products.