Peter Vroom

Aloha from the University of Hawaii! I'm a doctoral student in the Department of Botany studying evolution, population genetics, and ecology in the green algal order Bryopsidales. This group of marine macrophytes is really interesting for a number of reasons.
First, the Bryopsidales contains the largest known green algae, yet all plants consist of a single undivided cell. In the Mediterranean, Caulerpa taxifolia is known to grow over 80 cm tall, and can have upright blades with a density of over 10,000 per square meter! Because these are multinuclear organisms, gene regulation must be a nightmare. Some really interesting studies looking at whether all nuclei share an equal role within the algal thallus could be really fascinating.
Second, many calcified genera in the Bryopsidales are tropical in distribution. Genera such as Halimeda are major contributors to coral reefs. As plants die and disintegrate, they break down to form sand. In some areas, coral sand beaches aren't composed of coral at all, but instead have an algal origin. The importance of these algae on tropical reefs is often neglected, and a greater effort needs to be made to recognize their contribution to the environment as reef conservation efforts continue. Two individuals of Halimeda incrassata from Key Largo, Florida are pictured at right. These holocarpic algae convert all cellular constituents into reproductive cells. Upon gamete release, the calcified segments break down to form sand.
Third, the Bryopsidales is an ancient order having arisen several hundred million years ago. Because of the lengthy time frame that extant genera have had to evolve, the diversity of life-history patterns, reproduction, and vegetative morphologies is astounding. The range of life histories found in just the family Bryopsidaceae is greater than the types of patterns found in many entire kingdoms! Unfortunately, all this diversity often makes it very difficult to determine evolutionary affinities. My goal is to try and sort out some of the confusion through both detailed morphological and molecular studies of the group.

To see represenatives of the 29 genera contained in the Bryopsidales, visit the Catalog of Siphonous Green Algae. Two Bryopsidalean genera: Caulerpa sertularioides (on left) is characterized by uncalicifed, pinnately branched upright blades while Rhipidosiphon javensis (on right; growing clumped on a dead piece of coral) consists of calcified, flabellate (fan-shaped) blades .

During summer months, Celia Smith (my major professor) and her graduate students regularly go to Florida to research the green algal genus Halimeda in Key Largo, Florida. This research has been funded through the The University of North Carolina, Wilmington's National Undersea Research Center (NURC). We are assessing dynamics of the Key Largo Halimeda populations through long term and short term longevity studies, studies of growth rate, and studies of reproduction. I currently have two Halimeda research projects underway:

Members of the Bryopsidales are known to reproduce both sexually and asexually. Vegetative fragments of Halimeda produced via mechanical damage (fish grazing, heavy water motion), have been shown to rapidly produce rhizoids, resettle, and begin growth. Because the Florida Keys are impacted regularly by hurricanes, and because fish grazing on Conch Reef can be intense, I'm curious to determine whether sexual or asexual reproductive strategies prevail in the populations we study on Conch Reef. Sexual reproduction would lead to high genetic diversity, whereas asexual reproduction could lead to almost clonal populations with extremely low genetic diversity. It is hypothesized that shallow populations that are exposed to higher water motion may exhibit more fragmentation than deeper populations. Randomly Amplified Polymorphic DNA (RAPD) analysis is currently underway to determine the degree of genetic diversity in Halimeda tuna from Conch Reef.

Halimeda tuna from two geographically close, but environmentally distinct populations have significantly different morphologies, rates of growth, and population numbers. Individuals from shallow depths are smaller in stature and, surprisingly, have lower growth rates than their deeper counterparts. Several factors including nutrient availability and photosynthetic efficiency may contribute to this unexpected finding. Despite faster growth rates at depth, shallow populations are still more important in terms of calcium carbonate production because of the sheer number of individuals found at shallower depths. The paper for this research in currently in preparation, and will be submitted in June, 2001.

My major professor, Celia Smith, and I studying Halimeda on Conch Reef, Key Largo, Florida.

Team Halimeda on the bow of the Wildcard.

In back: Jennifer Smith, University of Hawaii. In middle row: Celia Smith, University of Hawaii; Peter Vroom, University of Hawaii, Linda Walters, University of Central Florida. In front row: Giacomo Bernardi, Stanford University; Brenda Konar, University of Alaska, Fairbanks; and Cassandra Roberts. Not shown: James Coyer, University of Gronigen; Kevin Beach, University of Tampa; Ryan Okano, University of Hawaii.

Two recent cruises to the Northwest Hawaiian Islands during 2000 brought back algal samples from a number of islands where little was known about the algal flora. The French Frigates shoals consists of a variety of small islands, rocks, and shoals. Before 2000, only 14 species of algae had been recorded from this area. After six months of specimen identification, I have identified approximately 130 species, with several undescribed, endemic species. Identification continues, with the hopes of sending a paper off for publication this autumn.

Vroom, P. S., L. J. Walters, K. S. Beach, J. A. Coyer, M. J. Abgralle, K. L. DeAngelis, D. Byron, B. Konar, J. Liss, R. Okano, C.A. Roberts, J. E. Smith, L. Wick, M. Woo, and C. M. Smith. (in review, submitted June, 2001). Hurricane induced macroalgal bloom in the Florida Keys: Dictyota spp. (Phaeophyta) population explosion. Oecologia.
	*Vroom, Peter S., Jennifer E. Smith, Celia M. Smith. (2001). Observations of reproduction in Rhipidosiphon javensis* (Halimedineae, Bryopsidales) in Hawaii. Phycologia. 40.**
Kim, Hyi-Gyung, Sterling C. Keeley, Peter S. Vroom, Robert K. Jansen. (1998) Molecular Evidence for an African Origin of the Hawaiian Endemic Hesperomannia (Asteraceae). Proceedings of the National Academy of Sciences, USA. 95: 15440-15445.
	Vroom, Peter S., Celia M. Smith, Sterling C. Keeley. (1998) Cladistics of the Bryopsidales: A Preliminary Analysis. Journal of Phycology 34: 351-360.