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You are here: /main/research/NOWRAMP 2002/journals/limu/


Ship Logs

Written By Carlos Eyles
Underwater Photography by Jim Watt
October 3, 2002

Caulerpa sp., not common in Main Hawaiian Islands.Last night we had an all hands meeting. Randy Kosaki, the chief scientist spoke of our return, and how we would be pulling in to Aloha Tower on Monday the 7th of this month, four days away. In that moment, you could feel the helium leave the village balloon. Nothing was said in that regard, perhaps a collective sigh that only a monk seal could hear, but I certainly felt it. The work schedule has been the most intense that I have ever experienced. Those on board have been phenomenal in terms of their capacity to endure sixteen hour work days and nights week in and week out. But you can't go on indefinitely at that pace, and today we are in the middle of a thirty-seven hour transit, and things have understandably slowed. People are still focused at their computers, there is still work to be done, actually quite a bit of work, but the frenetic energy that propelled us these last twenty-five days is absent. Fortunately we have a following sea to ease the rock and roll so the work flows out of the computers with the regularity of a Swiss watch.

Dasya iridescens.  Found throughout Hawaiian Islands.So much of my focus throughout this expedition has been on the dramatic; sharks, ulua, fish populations, shipwrecks, and the like. But much of the science has focused on the baseline foundations of a reef system. The coral and other invertebrates, algal studies, terrestrial studies, all seemingly uninteresting until one begins to spend time with these specialists. Their enthusiasm for their respective fields is infectious, and they know that without the seaweed, or limu, (which means, the plant growing in a wet place), none of the dramatic would exist, no sharks, no big fish, no fish at all, not even the shipwrecks would occur. How you might ask is that possible? Limu is the base, the very foundation of the food chain. It captures the sun's energy and this captured energy is transferred to other organisms. Limu manufactures oxygen and releases it through photosynthesis. Allow me to point out that before photosynthesis just a mere 4 billion years ago there was no oxygen, no ozone layer, no people, no animals, and no video games. That was a very long time ago. Some microscopic limu even live within the tissues of reef corals and they produce most of the food these corals need to survive.

Most limu is reproduced by spores that are carried by underwater currents, the wind of the sea, they settle and begin to grow, but must contend with surge, strong currents, sand scouring, the grazing of herbivores, all which are factors in their development and growth. Limu is instrumental in creating three dimensional habitats in the tropics; they are the cement of the reef, the consolidators. There are many different kinds of limu, some five hundred species in Hawai‘i. Some produce sand when they die, some are as fine and delicate as a strand of hair, others are hard and strong, often tougher and more resilient than the coral in that it can handle far more abuse and thus build a reef system in harsh, stormy conditions. They provide a reef system with habitat, food, and oxygen; the big three.

Kallymenia thompsonii and Peysonellia sp.  Found throughout Hawaiian Islands.Here in the Northwestern Hawaiian Islands there exists limu that does not exist on the Main Islands. In this pristine environment the limu is diverse and often plentiful, and the healthy balance of a reef system is dependent on it. I asked Dr. Karla McDermid the seaweed team leader, as well as an REA team leader, what would happen if all the seaweed suddenly vanished. She said first off there would be no food for the manini, parrotfish, or green sea turtles. The herbivorous (plant eating) fish would die, and leave the ulua and sharks with nothing to eat. The reefs would lose their cement and soon crumble and erode. The entire ocean ecosystem would suffer a huge loss, the long-term consequences of which would be ugly to say the least.

It's all so delicate, a balancing act that is precarious at best. The ocean is an enigma wrapped in a mystery. So strong and powerful, yet so fragile and delicate. So intricate and yet so simple. Its softness can embrace and its hardness can kill. It appears invincible, but it is easily wounded. It is long lived, but parts of it have died. It gives generously but its generosity has limits. It is the life blood of the planet and in its purity and stability lays the hope for the future.

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Talk About It!

Algae and plant classification

Asked by Diane from Kealakehe Elem on Jan 22, 2004.
I just learned that algae is in a different classification than plants (protoctista). Why are they not plants? So technically, is a herbivore an animal that eats plants and non-animals (like algae)?

Answered by Paulo from UH on Jan 26, 2004.
Classification of life into neat and distinct groups is a difficult undertaking, one that needs to be updated and rearranged we discover new ones and understand the old ones better. Algae have their own kingdom, separate from that of the plant kingdom. This was not always the case, as algae were for a long time grouped together with plants by scientists. The reason that they were thought to be in the same group was that they both have the ability to photosynthesize (both have the ability to photosynthesize, but now we also know that even some form of bacteria can do this as well!). But unlike plants, algae do not develop from an embryo. Plants also have a vascular system (vein-like structures that transports nutrients within the organism) and roots used to absorb nutrients from the land, both of which algae do not have- being immersed in water they can absorb nutrients and other elements from everywhere (they anchor to the bottom with a “holdfast.”) The actual kingdom Protoctista is very varied, as the common trait among its members is the lack of traits the determine each of the other kingdoms- just as the majority of animals on earth are “invertebrates,” a group so varied that that the only common element is the lack of a vertebrate. There are a few plants (grass-like) that are found on the ocean, but for the most part, plants are terrestrial, whereas algae are strictly aquatic. So the term herbivore, which fits well on land animals (unless they also eat mushrooms too!), has to be interpreted broadly when applied to marine organism- the term “algaevore” never really stuck around, so we still use herbivore.

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