Seaweeds thrown up onto the shore at this time of year can include Egg wrack, (Ascophyllum nodosum), the green stuff with the large bladders in the photo, and Bladderwrack (Fucus vesiculosus) which is the brown one. Bladderwrack often has its bladders arranged in pairs.
The air bladders allow the seaweed to float upright when underwater. The number of air bladders on each frond depends upon how exposed the shoreline is – on exposed shores bladder wrack has fewer air bladders than on sheltered shores.
For further information on seaweed identification see Natural History Museum
Uses: Bladderwrack is used as an additive and flavouring in various food products in Europe. Bladderwrack is commonly found as a component of kelp tablets or powders used as nutritional supplements. It is sometimes loosely called "kelp", but that term technically refers to a different seaweed.
Primary chemical constituents of this plant include mucilage, algin, mannitol, beta-carotene, zeaxanthin, iodine, bromine, potassium, volatile oils, and many other minerals. The main use of bladderwrack (and other types of seaweed) in herbal medicine is as a source of iodine, an essential nutrient for the thyroid gland. Bladderwrack has proved most useful in the treatment of underactive thyroid glands (hypothyroidism) and goitre. Through the regulation of thyroid function, there is an improvement in all the associated symptoms. It has a reputation in helping the relief of rheumatism and rheumatoid arthritis, both used internally and as an external application upon inflamed joints.
A chemical constituent of bladderwrack called alginic acid swells upon contact with water; when taken orally, it forms a type of "seal" at the top of the stomach, and for this reason is used in several over-the-counter preparations for heartburn. The same constituent gives bladderwrack laxative properties as well. Other proposed uses of bladderwrack include treating atherosclerosis and strengthening immunity, although there is no scientific evidence at present that it works for these purposes.
Bladderwrack has been shown to help women with abnormal menstrual cycling patterns and/or menstrual-related disease histories. Doses of 700 to 1400mg/day were found to increase the menstrual cycle lengths, decrease the days of menstruation per cycle, and decrease the serum levels of 17B-estradiol while was later carried out and showed similar effects.
Bladderwrack should not be used in cases of hyperthyroidism or cardiac problems, or during pregnancy and lactation. Excessive dosage (many times the recommended dosage) may lead to hyperthyroidism, tremor, increased pulse rate and elevated blood pressure. (Wikipedia)