NJCWST's
Visual Guide to Aquatic Microorganisms
About the Guide
How to Use the Guide
Every step of the guide presents the user with two options to choose from. Each option is represented by a photo collage and a written description. At each step, compare the two options presented, and click the button below the option that best describes the specimen you wish to identify.
Upon selecting one of the two options at each step, you will be directed either to a subsequent step in the guide, or to a taxonomic description page. If you are directed to another step in the guide, there will be a button in the lower left corner that you can click if you wish to return to the previous step. If you are directed to a taxonomic description page, there will be a button at the top left corner that you can click if you wish to return to the step in the guide that you left off at. Some steps in the guide contain relevant glossary terms at the bottom of the page; if you encounter a term you are unfamiliar with and it is not included on the page itself, visit the glossary page.
Progress through the guide until you are directed to a taxonomic description page; the description page you land on is the group that your specimen likely belongs to. For example, if the guide directs you to the Diatoms page, this means that your specimen is likely a diatom.
What to do With Your Results
The guide will ultimately direct you to a page containing information about a specific taxonomic group (for example, Green Algae)—the taxonomic description page you are directed to is the taxonomic group that your specimen most likely belongs to, based on the options you selected at each step of the guide. Each taxonomic description page will include information about the morphology and ecology of that group.
Compare your specimen to the the information and photos provided on the description page—does your specimen fit the morphological description provided on the page?
Yes, my specimen fits the description
Great, it sounds like you’ve correctly identified the group your specimen belongs to! If it belongs to one of the major algal groups and you are interested in determining which genus your algal specimen belongs to, here are some steps you can take:
At the bottom of each taxonomic description page you’ll find photos of some of the genera commonly observed by NJCWST. Compare your specimen to the photos of each genus—do any of the genera pictured look like a match? If so, consult one of the following resources to learn more about the genus so that you can confirm your ID:
AlgaeBase (Guiry & Guiry, 2023) is a reliable online resource for images and descriptions of a variety of algal taxa.
If the specimen is a diatom, visit Diatoms.org (Spaulding et al., 2021), which provides descriptions and images of a wide variety of freshwater diatom genera.
If possible, consult an identification guidebook. We at NJCWST use Freshwater Algae of North America: Ecology and Classification, 2nd ed. (Wehr et al., 2015).
If none of the genera pictured on the taxonomic description page look like your specimen, here are some other resources you can consult to help identify the genus:
PhycoKey (Baker et al., 2012) is an excellent online key to various algal genera—see if you can identify the genus of your specimen using PhycoKey!
Diatoms.org (Spaulding et al., 2021) provides descriptions and images of a wide variety of diatom genera and species. Genera are organized into several categories based on similar morphological features, which is helpful for identification purposes, and the site also has a thorough glossary of relevant terms.
PhycoTech, Inc. has an extensive library of images of various algal genera, organized by genus. Exploring their image library may help you identify the genus of your algal specimen!
If possible, consult an identification guidebook that includes images and keys to genera in each major algal group. We at NJCWST use Freshwater Algae of North America: Ecology and Classification, 2nd ed. (Wehr et al., 2015).
As a side note: once you’ve found a match to your specimen using an online or print guide, it never hurts to check AlgaeBase for more information about the genus. AlgaeBase doesn’t have genus identification keys, so it isn’t very practical to use as a guide, but it is regularly updated to reflect taxonomic revisions—thus, it’s a great resource for confirming your IDs, since algal classifications are frequently revised.
No, my specimen doesn’t fit the description—what should I do?
Review our Algae Identification Advice & FAQs page, which addresses many common algae identification difficulties!
Browse through our taxonomic description pages individually; there are taxa within each major group that can be tricky to identify based on a beginner-friendly key (like ours). By reading more about each group—and examining more photos of representative genera within each group—you may be able to determine which group your specimen belongs to.
If you still can’t confidently figure out which group your specimen belongs to, consult an identification guidebook if possible. NJCWST frequently uses Freshwater Algae of North America: Ecology and Classification (2nd ed), which includes a key to the major groups of freshwater algae.
Which of the following options best describes the organism(s) of interest?
Click one of the green buttons below to proceed.
Cell(s) with distinctly pigmented contents (green, golden-brown, blue-green, etc). Cell(s) microscopic; unicellular, colonial, or filamentous. Without cilia. With or without flagella. Non-motile or motile; if motile, either free-swimming or gliding/creeping on surfaces.
Organism(s) essentially colorless or with very dull coloration (greyish, brownish, etc). Individual organism(s) microscopic or larger in size (up to ~6 mm in length); solitary or colonial. May have cilia, one or more flagella, or pseudopodia. Motile; free-swimming or gliding/crawling, or attached to substrates (but still exhibiting movement). May be observed ingesting/engulfing algal cells, and/or ingested algae may be visible within the body.
Glossary Terms on This Page
Cilia: Short, hairlike structures projecting from the surface of some eukaryotic cells, including many non-photosynthetic protists. Shorter than flagella, and present in greater numbers than flagella.
Pseudopodia: motile projections of the cell surface. May be blunt and finger-like, or thin and thread-like.