UH Scientists‘ Research of Single-Celled Green Algae Featured in American Scientist

University of Hawaiʻi
Shawn Nakamoto, (808) 956-9095
University and Community Relations
Kristen Cabral, (808) 956-5039
University and Community Relations
Posted: Dec 26, 2001

HONOLULU — The research of University of Hawaiʻi at Manoa Botanical Sciences Professor Celia Smith and doctoral candidate Peter Vroom and their observations of a group of marine plants called siphonous green algae is featured in the November/December issue of American Scientist, a bimonthly magazine of science and technology published by Sigma Xi, a scientific research society.

Because many algae in this group of marine plants are able to fragment and re-grow, they possess traits that give them a competitive edge over other marine creatures and allow them to become invasive in certain environments. This is of huge concern for researchers and environmental managers who are worried about possible species invasions that can upset ecological balances in natural communities as well as cause serious economic consequences. Examples of this include the explosive spread of one species, Caulerpa taxifolia (a native alga in Hawaiʻi), in the Mediterranean in which its range expands on average by some 50 kilometers each year, aggressively overtaking native species. Another species, Codium fragile, introduced into New England waters, often settles on oyster and scallop shells found in commercial fishing beds. The shape and size of the plants can cause them to be swept away during storms, taking the underlying scallops and oysters with them. Research exploring the ecological and molecular characteristics of native species in Hawaiʻi needs to be conducted in order to effectively manage these plants and ensure that similar ecological havoc does not occur here.

Siphonous green algae are able to become effective invaders because they possess a variety of unique features. These organisms take the form of tubes, or "siphons," arranged in elaborate networks that, in some genera, can affix to the sea floor at many points. Although some of these plants can stand up to as much as three feet tall, each is composed of a single, huge cell. Within that one large cell, millions of nuclei, chloroplasts and mitochondria move about freely. What is even more unique about these plants is that though this characteristic may make them seem particularly vulnerable to injury, these algae are actually quite robust, primarily because of their ability to reproduce clonally. "Instead of being vulnerable to, say, storm damage, these plants benefit when they are smashed to pieces, each of which can then sprout and become an adult," explained Vroom.

The researchers saw this first-hand in Hawaiʻi after Hurricane Iniki in 1992. Many hurricane-generated fragments of Halimeda, a type of siphonous green alga, drifted to shore. When collected and cultured, the fragments remained healthy and quickly developed attachment rhizoids — small colorless siphons with which the alga attaches itself to the floor of a reef.

Despite the proliferation of "weedy" types in some regions, there are other species of siphonous green algae that are so specialized that they are actually rare. One type, an endemic Hawaiian alga called Boodleopsis hawaiiensis, requires a habitat so rare that it could actually become the first alga to be listed as an endangered species.

Smith and Vroom have been and continue to study how siphonous green algae grow and reproduce in hopes of discerning better the evolutionary relationships between the different species, understanding how they affect the health of tropical ecosystems and figuring out what exactly causes the proliferation of "weedy" types in some environments. They hope to obtain and collect more information and descriptions of these species‘ life histories, reproductive structures and ecological distributions.