I have noticed that most people - especially vegetarians or vegans (which completely I am) - do not have a correct understanding or knowledge of the micro-animal family in which algae and all the so-called "sea-weeds" belong! - So believing them to be vegetable matter, do eat them!
To call algae, kelp, nori, spirulina (sometimes spelled: spiralina), carrageenan or any "sea-weed" a "vegetable" is biological folly or simple ignorance of marine life fact! All so-called algae or seaweeds are made up of primitive animal cells called protists and are cyano-bacteria or flagellates - tiny animal cells!
They do exist as single cell organisms, as in the "algae", or as cooperating individuals in multi-celled (labor-organized) colonies, as in kelp, nori and all the other larger and complex "sea-weeds". (misnomer)
As with all other animals, these are oxygen consumers (not providers), so they will markedly deplete water of oxygen available to fish and all other sea life when excess blood, body fluids, decomposing animal tissues and animal wastes allow their "blossom" or "bloom" to occur in, and thus choking, a river, lake or sea!
Their "plant-like" structuring permits any colony of these organisms to take advantage of the water's layered current differentials - hence a continuously renewing food supply is provided to all individuals. But of equal survival value to the organism is its additional incorporating of chloroplast-like organelles. These chloroplast-like organelles in these submerged organisms rarely receive any appreciable sunlight for energy conversion value, but do really serve by its exhibiting of plant-like colors to camouflage the organisms as a plants - thus avoiding being devoured by fish and all sea mammals - all of which are obligate carnivores!
It is important for you to understand that all algae and sea-weeds also are obligate carnivores - filter-feeding upon bacteria, viruses, amoebas, and all decomposing animal fluids, tissues and waste! - They also pick, accumulate and concentrate all the toxins of man, industry, livestock, game, and runoff in the rivers and oceans. That waste is their food and its collection into themselves is their function. -- Do you want it to be yours?
Also you need to understand that as a small animal organism the algae (all sea-weeds) produce in their life chemical processes the base hormones - that is, the steroids extant to all animal life! These steroids (hormones) stimulate or manipulate all animal life processes - including yours! The common supplemental ingestion of algae and sea-weed facilitates the factual reason and explanation as to why several Olympic participants were recently tested positive for steroids, even when they and their trainers were certain and certified that no illicit steroids had been given to them! What they and you don't know - will hurt you!
Also know, as an associate to key marine disease biologists, we track and identify the viruses first in the algeas, then fish and sea mammals early in the year so as to permit the prediction of what strains of influenza, RSV, etc will passed through the marine-life-scavenging birds, then literally be flown to the game and livestock - and finally through those animal's (packaged and sold) fluids and tissues to your infant and you! Our identification of the pathogens earlier in the algae and marine life is how the vaccines are predetermined, formulated, cultured and prepared. But this year the birds confused by strange weather have tricked us a little with their changed travels and different mixing of migratory routes. So the vaccine producers must now reformulate! It is this unforeseen viral mixing/mutation and migratory delay that is the vaccine preparation problem, not a "shortage!"
So if you want to avoid viral (and mycobacterial) contact, heavy metals and halides (like mercury, fluoride, etc), steroids, antigenic reactions (autoimmune triggers), the consumption of animal tissues, chemical pollutants, agricultural and industrial runoff and nature's waste; then you must leave the algaes (all sea weeds) to do their divinely designed function -- to filter nature's and your waters -- while you do your divinely designed function -- to protect and preserve it! -- and your own life through it!
You don't eat your water filter! That is not smart at all!
The Algaes (all seaweeds) are Nature's water filters! So don't be fooled into purchasing and putting them and the filthy and hazardous filtrates they have consumed into you or anyone else you love!