Introduction

(1) While still an undergraduate student at the then Dar es Salaam University College of the University of East Africa, in 1968, I discovered that Tanzania’s coastal village communities were involved in harvesting and drying species of the red seaweed genus Eucheuma, for export trade. Locally known as mwani, the seaweed found markets in the U.K., France, and Denmark.

(2) In Europe the Eucheuma seaweed is boiled to produce a gel, which has a wide range of applications in industry, as a gelling, thickening, and emulsifying agent. We all use colloids from Eucheuma and related seaweeds practically everyday, often quite unaware. When you eat ice cream, chocolate, milk products, and salad dressings; when you drink medicinal syrups, beer, wine, fruit juices and other beverages; when you swallow capsules of antibiotics; when you use textile printing pastes, shaving creams, toothpastes, waxes, shoe polish, paints, varnishes, body lotions, and shampoos of various kinds, you are, almost invariably, making applications of colloids extracted from seaweeds.

(3) In the United States, and now also in many countries in Europe, you now can buy a hamburger enriched with a layer of seaweed colloid. Such sandwiches are low in calorie, and ideal for individuals with obesity problems, who thus need assistance to level off that ugly looking, excessively convex, patriotic front, which, they say, is an abomination to the Lord. They are also recommended to those who desire to maintain a body configuration which touches the emotions of the beholder.

(4) It is surprising, therefore, that such important and useful plants, the algae, which also constitute the supporting base of food pyramids in our marine ecosystems, and which thus sustain the lives of the myriads of fish and other aquatic biota that we harvest everyday for food and other applications, should be referred to as weeds. The term seaweed for the sea plants under discussion, is certainly inappropriate.

(5) The organisms embraced under the term algae share the following general attributes:

· simple anatomical and morphological structure, lacking true roots, leaves, flowers, seeds, and vascular xylem and phloem;

· possession of chlorophyll a (and often one additional, other type of chlorophyll), as well as a wide array of accessory photosynthetic pigments;

· ability to photosynthesize, by virtue of their chlorophylls and associated pigments;

· adaptation for life in aquatic environments, in the sea, in lakes, rivers, moist soils, and even in snowfields. Some algae even grow inside the tissues of other aquatic plants and animals, including the coral polyps. Others occur in relatively dry habitats, as phycobiont components of lichens, while a few can even tolerate life in hot springs. One could, indeed, almost adapt the well known dictum in the Ancient Mariner, “...water, water everywhere”, to “algae, algae everywhere.”

(6) I have selected a few series of slides which will, I hope, give you a better idea about the organisms embraced under the name, algae. In fact, if you are looking for surprises in the biological world, you will find many amongst the algae. Through the slides you will see some of these.

(a) Some algae are amongst the most photogenic and the cutest organisms in our biosphere. Names of algae such as Nothogenia majestica, Polyzonia elegans, and Vanvoorstia spectabilis, speak for themselves, with regard to the extent to which they had excited the imagination of the scientists who first described them. They are, indeed, majestic, elegant, and spectacular.

(b) Algae exhibit all shades of colour, often in the most agreable combinations. This is because in addition to their green chlorophylls, they also have a wide array of yellow carotenoids; some also contain the red pigment, phycoerythrin; others also contain the blue pigment phycocyanin; or the brown pigment, fucoxanthin, etc, etc. Many of the accessory pigments are a monopoly of the algae.

(c) Algae show remarkable biodiversity with respect to their sizes. Many are microscopic, and these range from single-celled organisms, to colonies of tens, hundreds, or thousands of identical cells. Many others attain sizes ranging from a few centimetres to about a metre or so in height. But there are also some macrophytic giants, which attain heights of 20.0 to 40.0 metres or more. One of such astonishing macrophytes, is the brown seaweed Macrocystis pyrifera, which can reach 45.0 metres in height.

(d) Algae also offer many pleasant surprises with respect to their architecture. They range from single-celled or multicellular spherical balls, to star-shaped fronds, to cresent shapes, to castus-like, berry-like, worm-like, umbrella-like, palm-like, wine-glass like, and other forms.

(e) It is also surprising that so many edible algae have been neglected as a food item in Africa. But in Japan, China, Korea, The Philippines, Hawaii, Malaysia, and Indonesia, many species of algae are regularly harvested for use as food, to supply the body with a wide range of vitamins, inorganic minerals, and some also with protein. Some of the edible seaweeds, e.g., Porphyra, Laminaria, Undaria, Monostroma, and Caulerpa, are now produced through cultivation, and constitute a multi-million dollar industry. In Hawaii, one of the most esteemed amongst the edible algae, Asparagopsis taxiformis, commands an unbelievable price of over US $ 35.0 per kilo (fresh weight), making it the most expensive vegetable in the world. In Chad, the micro-alga Spirulina platensis is also harvested for use as food. Spirulina is also abundant in East Africa’s inland alkaline lakes, such as Lake Natron and Lake Nakuru, where it constitutes the choice food of the lesser flamingoes. Since the mid 1960’s when it was discovered that Spirulina is 60 to 70% protein, the alga has been domesticated in commercial farms, in Mexico, California, and elsewhere, for the production of protein and other valuable natural products of commerce. You now can buy Spirulina tablets for your daily protein requirements. In fact, Spirulina is also very rich in vitamins and iron.

(f) Some algae exhibit the phenomenon of bioluminescence, and can emit light, like the fire-flies we see at night, One such alga is the dinoflagellate, Noctiluca. Its very name is indeed suggestive of bioluminescence. When in large numbers in the sea, such micro-algae can be quite a delight to the on-lookers at night.

(g) The seaweed Desmarestia offers another surprise: its cells constitute a miniature factory of sulphuric acid. Yes, H₂SO₄, of all things, for whatever reason. Certainly, a corrosive acid such as H₂SO₄, would scare off potential grazers.

(h) Final surprise. None of the species amongst the Blue-green algae, the Cyanophyta, not a single one of them, has ever been caught in the sexual act. And the assumption has always been that, either they are too good in keeping the secrets to themselves, or they don’t do it, which is quite unusual. Sometimes I imagine that King David might have had plants like algae in mind when he wrote one of his psalms:”...O Lord, how wonderful are thy works. And thy thoughts are very deep” (Psalm, 92:5). Sometimes I tend to think that Leveillea jungermannioides, or Polyzonia elegans under the microscope. When you see their surpassing beauty, you will, I believe, understand why a person such as me, a typical mountain species, who first saw the ocean at the age of 20, decided to devote so much attention to the biota in question: the algae. Let us now get into the subject of my lecture, the Eucheuma seaweed.