Freshwater Dinoflagellates of North America: A Guide to the Unicellular Algae at the Bottom of the Food Chain
Dinoflagellates are common unicellular organisms found in all types of aquatic ecosystems and are important contributors to freshwater ecosystems as significant primary producers of biomass. They are also fascinating organisms that can have complex life cycles, bioluminescence, toxins, symbiosis, and fossil records. Despite increasing interest in the biology of living and fossil dinoflagellates, there has been no compilation of dinoflagellate species found in North America since 1934, and no keys to species.
In this article, we will introduce you to the book Freshwater Dinoflagellates of North America by Susan Carty, which provides a much-needed taxonomic guide covering Canada, the United States, Mexico, all of Central America, the Caribbean, and Greenland. This book is available for download as a pdf file from various online sources[^1^] [^2^] [^3^].
The book features:
identification of dinoflagellate species,
distribution maps of species,
ecological and morphological keys to genera,
key to species within genus,
lists of references by location,
an extensive illustration program.
Following an introductory section on the biology, morphology, and ecology of freshwater dinoflagellates, the species are presented in a field guide format with distribution maps, written descriptions emphasizing notable features, line drawings, and black-and-white and color micrographs. The book covers both naked (athecate) and armored (thecate) taxa, and includes some rare and newly described species.
If you are interested in learning more about these amazing algae that live at the bottom of the food chain, Freshwater Dinoflagellates of North America is a valuable resource that will help you identify and appreciate the diversity and beauty of these microscopic organisms.
One of the most interesting aspects of dinoflagellates is their ability to produce bioluminescence, or light emission, in response to mechanical stimulation. This phenomenon can create spectacular displays of glowing water at night, especially in marine environments. However, some freshwater dinoflagellates can also produce bioluminescence, such as Pyrocystis lunula, which is found in North America and other regions. This species has a crescent-shaped cell with two flagella and a large nucleus that contains a single chromosome. The bioluminescence is produced by a chemical reaction involving luciferin and luciferase, which are stored in small vesicles called scintillons. When the cell is disturbed, the scintillons release their contents into the cytoplasm, where the light is emitted. The function of bioluminescence in dinoflagellates is not fully understood, but it may serve as a defense mechanism, a communication signal, or a way to attract prey or mates.
Another remarkable feature of dinoflagellates is their role as symbionts, or partners, with other organisms. Many marine dinoflagellates belong to the genus Symbiodinium, which forms mutualistic associations with corals, sea anemones, giant clams, and other invertebrates. These symbionts provide photosynthetic products to their hosts, while receiving protection and nutrients in return. However, when the environmental conditions become unfavorable, such as high temperature or pollution, the symbiosis can break down and the dinoflagellates are expelled from their hosts. This causes coral bleaching, which can lead to the death of the coral reef ecosystem. Some freshwater dinoflagellates can also form symbioses with other algae, such as Peridiniopsis penardii, which lives inside the cells of Oedogonium, a filamentous green alga. This symbiosis may enhance the growth and survival of both partners.
A third aspect of dinoflagellates that deserves attention is their fossil record, which dates back to the early Mesozoic era, about 250 million years ago. Dinoflagellates have a unique type of cell wall called a theca, which is composed of cellulose plates that fit together like a puzzle. These plates can be preserved as fossils when they are shed by the living cells or when the cells die. The fossilized plates are called dinocysts or dinoflagellate cysts, and they can provide valuable information about the evolution, diversity, ecology, and paleoenvironment of dinoflagellates and their associated organisms. For example, some dinocysts can indicate the salinity, temperature, or productivity of the water where they were deposited. Some dinocysts can also be used as biostratigraphic markers, which help to date and correlate sedimentary rocks from different locations. aa16f39245