Learning about Staten Island seaweeds

[USA] An exploration of most natural beaches in the New York area at this time of year will reveal a variety of life in the intertidal zone. Mud snails abound, barnacles cover many rocks and grass shrimp dart around in tidal pools. Most of this activity occurs in, under and around large masses of seaweed that provide food and shelter for most of the invertebrates and small fish that live in the perilous area between the tide lines.

Three main types of seaweed

Seaweeds are considered to be multicellular forms of algae. They are classified into three groups based on the pigments they use for photosynthesis. These are the red, brown and green algae. Since they have not evolved complex tissues, seaweeds are considered algae, rather than true plants. Nonetheless, algae play a similar role in the ocean that plants play on land.

The most complex seaweeds are the brown algae that have rudimentarily specialized structures such as holdfasts for attaching to rocks and wide leaf-like blades for photosynthesis. Locally, rockweed with its bubble-shaped floats is the most common species. Kelp and sargassum are large types of brown algae that have significant ecological and economic value.

Due to their use of the blue end of the spectrum, the red algae can survive at greater depths than other algae. Along our shores, laver (aka porphyra) is the most common genus of the red algae.

The largest and most varied group is the green algae. Whereas brown and red algae are almost entirely multicellular seaweeds, many species of green algae are single-celled. Though individual cells can only be seen with a microscope, these algae give seawater in northern seas their green color and provide food for the base of marine food chains. Sea lettuce is a common local variety of green seaweed.

Seaweed extracts are in many foods and other products

Even if you don’t eat sushi, odds are that you have eaten something that contains an extract of seaweed recently. Seaweed extracts such as carrageenan and agar are commonly found in many processed foods and other products.

Red seaweeds are the source of carrageenans, which are a frequently found seaweed additive. Carrageenans form a gel at room temperature, so they are used to thicken and stabilize foods. Products that contain carrageenans include salad dressings, sauces, diet foods, preserved meat and fish products, dairy items and baked goods. They are also used in some toothpastes to hold the other ingredients together and in shampoos to make them thicker.

Agar is another product of red seaweed. Its main use is in microbiology as a growth material for bacteria and fungi. In culinary use it is found in confectionary foods, processed meat and poultry products, desserts, ice cream and even beverages such as beer. It is also used as a vegetarian gelatin substitute for thickening soups and jellies.

Alginates made from brown algae can be found in wound care products since they absorb fluid from wounds and maintain a moist surrounding.

Although sushi is well-known for including seaweed, Japan is not the only place where seaweeds are part of the national diet. Other nations where seaweed is consumed include Indonesia, Ireland, Scandinavia, Scotland and Peru. Laver bread is a traditional food in Wales made by boiling laver seaweed for a few hours then rolling it in oatmeal before frying.

It would actually be unusual for most people to go through a day without using at least one product that contained seaweed.

Beyond its uses as food or as a food additive, seaweeds are also being explored for their use in medications for tuberculosis, arthritis, influenza and worm infestations. Other uses of seaweed materials include preservatives for meat and fish, paper coatings, dyes, gels and even explosives.

Single-celled algae also matter

Other algae found in seawater include single-celled groups known as diatoms and dinoflagellates. Unfortunately, dinoflagellates are best known for causing red tide when their numbers soar. Diatoms have more redeeming values due to the glassy silica coverings that accumulate on the seafloor over millions of years.  Diatomaceous earth in pool filters strains small particles of dirt and debris from the water while diatoms in toothpaste help scrape plaque off the teeth.


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