Category Archives: algae

Dangerous Photosynthesizers

Because photosynthetic organisms are the energetic foundation of our biosphere, we always tend to think of them as allies, organisms with a positive connotation. Their trademark color green is universally linked with goodness, growth, and life. However, there are some bad apples in the bunch that just seem to have it out for us heterotrophs. Well, maybe not apples (though I’m sure there are some poisonous apples out there somewhere*), but nature is filled with examples of poisonous plants. Many toxins and pharmaceuticals have botanical origins.

The focus of today’s blog post sinks even lower- algae, pond scum, cyanobacteria. Most of these aquatic photosynthesizers quietly convert sunlight to biochemical energy without any ill effects to anyone. I’ve written previously, that under the right conditions (warm and nutrient-rich waters) these otherwise inconspicuous organisms bloom in great numbers and overwhelm their environments. Like all life on earth, algae are programmed to capitalize on favorable conditions for reproduction. The ultimate crashes of these blooms can result in aquatic dead zones, areas with dissolved oxygen levels too low to support life.**

Algal bloom in Lake Erie 2011 from the NASA Earth Observatory Credit: Jesse Allen and Robert Simmon via Wikimedia

However, in some cases, the effects of these algal ‘blooms’ go beyond sheer numbers. Some algae produce toxins which cause serious health problems for those of us heterotrophs sharing their environment. The individual constituents of these ‘harmful algal blooms’ (HABs) measure in at ~1-2 µm, but they can wreak all kinds of havoc on the scale of large cities. HABs can stop your summer fun by forcing beaches to close or eliminating certain shellfish from your diet, but this summer the problems went beyond recreation to something much more fundamental- potable water.

Clean, safe drinking water is a fundamental service of human civilization. In our modern society, just turn on the tap, cook, clean, bathe, drink. It has been such a staple of American cities that it is taken for granted. That is, until it’s no longer available. That was the exact situation in Toledo earlier this month. A large American city, in the year 2014, was without safe drinking water for a whole weekend. Approximately, 500,000 citizens were affected. All because of toxic algae.

Microcystin-LR chemical structure Credit: cacycle via Wikimedia

In this case, the culprit was a bloom of cyanobacteria which produce the toxin microcystin. This molecule is harmful to the health of humans, pets and wildlife by acting as a liver toxin. It also has neurotoxic effects. The toxicity of microcystins has been extensively characterized and long-known to be associated with certain cyanobacterial species. Because of the potential adverse effects of microcystin-producing cyanobacteria on modern water supplies, treatment facilities routinely check the levels of this toxin. Only one part per billion of this molecule is considered acceptable. When a microcystin-producing algal bloom occurs near the intake of a municipal water supply (as it did for Toledo this month) the facilities can quickly be overwhelmed causing the water supply to exceed acceptable microcystin levels. The situation is compounded by the fact that microcystins are resistant to boiling. While boiling water may destroy other toxins or contaminating bacteria, it only concentrates microcystins. In order to bring the toxin levels down, the problem must be addressed at the water treatment facility (using methods like activated carbon, ozone treatment and membrane filtration). By adjusting the normal procedures to account for increased microcystins, the water supply can be treated to once again safe levels. All of this is accompanied by exhaustive analysis of microcystin levels and vigilant monitoring after the incident.

Scientists and government agencies are always working to monitor our water systems for HABs. Check out some of the links below for descriptions of continuous efforts to monitor our environment for HABs. How do we get to the point of 500,000 people without water for a weekend with everyone watching out for it? I mean, we’re watching it from space! Even with all of these sophisticated tools and models, nature can be surprisingly swift. Check out these images and reports from the NOAA Great Lakes Environmental Research Lab on Aug 1, 2014 and Aug 4, 2014 showing false-colored images tracking the algal growth.

Simultaneously in the news cycle with the Toledo water crisis, two Ebola patients were being treated in premier isolation facilities on American soil. The nation’s attention was rapt with the details of their treatment and speculation was rampant as to the possibility of an outbreak in America (an infinitesimally small probability not worth talking seriously about among scientists and epidemiological experts, but a great ratings-driver). Worldwide, the Ebola death-toll numbers in the thousands, not just from this year, but ever. Based on pure body count, there are many deadlier infectious diseases, which we as the public dismiss more easily. Beyond those numbers, the lack of clean water for drinking, food preparation and sanitation results in the deaths of ~3 million people every year across the globe. A safe and reliable water supply, as a basic right, continues to elude human civilization.

Water, water everywhere, but not a drop to drink… Credit: de:Benutzer:Alex Anlicker

HABs are only a part of the world’s water problem. However, the disruption of Toledo’s water supply should have been an event that caught our attention and held it for a while longer. It may be easy to turn on the tap, but getting the clean water to that point takes a significant amount of effort with infrastructure maintenance, monitoring and treatment. All of these things are largely invisible to us in modern society. Unfortunately, all of these things are affected by other societal choices like economics, aesthetics, environmental regulations, and the practices of our agricultural systems and other industries. As a society, we should start having the longer, difficult conversations necessary to attack this complicated problem rather than the transient chats that occur when we are in crisis mode. Find out about your community’s water situation and the issues related to your supply. Talk to your community leaders today to ensure that safe water is part of your future.




*Hey, it’s hard to transition away from the summer’s Disney theme completely in a single post. However, I’m not just talking about the evil queen’s poisoned apple from the fairy tale. Apples have a huge amount of genetic diversity and I’m sure there are some varieties out there that are poisonous or so foul-tasting that you would think they are. After all, apples concentrate toxic substances in their seeds.

**In case you’re wondering, this year’s Gulf of Mexico hypoxic zone measured ~5500 square miles. That’s not breaking any records for size, but still about as large as the state of Connecticut. Read more about it here.


References and Links:

Independence Day: Red, White and Blue

In celebration of July 4th, this typically green blog is going red, white and blue.


There are lots of connections between plants and the color red. Roses are red. Plants emit a faint red fluorescent glow, as I wrote about in my previous post. But it isn’t all about plants; there are other photosynthesizers, like algae. While green may dominate your perception of algae, there is an entire group of red algae, the Rhodophyta, that exist below the surface of marine environments. Like plants and green algae, they are eukaryotes, but they have many photosynthetic characteristics that are closer to the prokaryotic cyanobacteria. Most notably, they contain the phycobilisome antenna structures to funnel light into their photosynthetic machinery. Since the red algae live in the ocean below other photosynthetic organisms, they take advantage of the higher-energy blue light that penetrates deeper into the water. To do this, they make the phycoerythrin pigment which appears red. This may sound exotic, but you may be more familiar with red algae than you think. The agar and agarose used in microbiology labs is derived from species of red algae as well as the nori used to roll your sushi.

Red Algae Chondrus Cripsus via Wikipedia


The ‘color’ white in plants is an interesting case. It means that no pigments are present, and all visible light is being reflected from the plant tissue. Very little, if any, light is being absorbed. Since their lives depend on converting sunlight into chemical energy, reflecting all of it away from themselves represents a risk by the plant. However, it is a calculated one that pays off. The white tissue of flowers depends on the other green parts of the plant to supply it with sugar and other energy molecules for biochemical support, but it creates a contrast from the rest of the plant. In this way, the plants have made it easier for pollinators to home in on flower tissue with its nectar and pollen. It creates the most basic win-win situation for plants and pollinators- no extra biochemical pathways required. Of course, some ‘plants’ take white too far and lose the ability to be photosynthetic as in the case of the ghost plant.

Pentas lanceolata via Wikipedia


True blue can also be difficult to come by in the plant world. Because blue light resides on the high-energy side of the light spectrum, it is in the best interest of the plants to absorb that energy to drive photosynthesis. Indeed, the antenna pigments of photosynthetic organisms are very good at absorbing blue and red light. However, some plants can make a special class of anthocyanidin that reflect blue light. Pigments like delphinidin give larkspurs, violas and grapes their distinctive bluish hues. Alas, not all plants have the biochemical pathways to create blue flowers, but the demand for blue blooms in the horticultural sector doesn’t let nature get in its way. Plant scientists can use biotechnology to insert the genes necessary to produce the blue pigment. While true blue roses haven’t quite come to fruition, blue varieties of carnations and chrysanthemums have been engineered.

Delphinium x Belladona Bellamosa via Wikipedia

These examples show that the photosynthetic world can be patriotic as well. Colors, like red, can come from common places and overlooked depths, while white can be a beneficial sacrifice. Blue can be true or migrate in from exotic sources.



References and Links:

April Berry Go Round: Plant Colors

When your life depends on light, as it does for plants and other photosynthetic organisms, color is important. Even the most flamboyant displays are functional not frivolous. Beyond being a consequence of the biophysics of photosynthesis, these exhibitions are used to attract pollinators, to send warnings to would-be herbivores, and to adapt to their surroundings. Of course, humans find these colors fascinating for reasons unrelated to their purposes for the plants. As a result, these beautiful botanicals have become entwined with human culture as well- in our gardens, in our kitchens, and in our artistic expressions. This edition (#69) of the Berry Go Round blog carnival explores the diverse topic of plants’ use of color.

Before we delve into the details of how plants use their colors or the extreme colors plants employ, start with this post from the As many exceptions as rules blog, which describes the extensive biochemical repertoire of plant pigments. Now let’s take a journey across the wavelengths of the spectrum of visible light. As you will see, plants don’t let any wavelengths go to waste. There is a purpose for every color and then some.

Spectrum of visible light via Wikipedia Original source: hi:Image:Srgbspectrum.png

When it comes to the color red, this vibrant color serves as an attractant that is perfectly adapted to the visual systems of their bird pollinators. The color red is also a strong attractant for humans because plants like Rubia tinctorium became so popular at one point as to be synonymous with empires.

Colors can be simultaneously beautiful and delicious as described in this post by Sarah Shailes. If you’ve ever wondered why saffron is so expensive, you should definitely click the link. A common flash of yellow in Louisiana these days is the yellow iris, which is the subject of this post by Dave Spier at the Northeast Naturalist blog.

Green is so ubiquitous among plants that it is often taken for granted. Yet plants do not take it so lightly, as explored in this post Beyond Green at the Postdoc Street blog. This post on the Plants And Rocks blog also describes how green bark can help give aspen trees a head start on photosynthesis before their leaves develop.

In the literary world, violets may be blue, but other botanicals come much closer to true blue in real life. One striking example that you may not be familiar with are the seeds of the Malagasy traveller’s tree (Ravenala madagascariensis) described in this post from Kew Millennium Seed Bank blog. When it comes to indigo, the plant and the color are one in the same. Find out more about the plant behind this pigment in this post by Sushmitha on a Blog of Scientific Nature.

There’s a new kid on the block when it comes to purple plants- the tomato. There are some heirloom varieties of purple tomatoes, but recently genetic engineering has been used to increase the amount of anthocyanins (antioxidant pigments) in tomatoes. Read more about them (and other genetically engineered plants) in this post by Izzy Webb on the John Innes SVC blog. Of course, other naturally-occurring pigments are found in our favorite edible plants. Check out the chemistry in these posts on Beetroot and Grapefruit from the Compound Interest blog.

Plants also display other colors beyond the typical rainbow of the visible spectrum. In fact, one species of tree, the rainbow eucalyptus, lives up to its name in a display of color more akin to the neon colors of an ‘80s music video than nature.

A grove of Rainbow Eucalyptus Eucalyptus deglupta trees, planted along the hana highway, Hawaii. Credit: Amelia via Wikipedia

Other plants are studies in monochrome. Ornamentals like the black pearl peppers described in this post by Mark Dwyer at the blog of Rotary Botanical Gardens in Wisconsin are entirely ink black– leaves and fruit. Emma Cooper offers you a steamy list of fifty shades of grey in the garden. Don’t worry, these are suitable for public display. Rebecca Deatsman describes a plant on the other end of the spectrum on her blog Rebecca in the Woods- the completely white Indian Pipe. It may look like a fungus, but it’s really a plant despite the fact that is eschews a photosynthetic lifestyle. I’ve mentioned before on this blog that it lacks all pigments required for photosynthesis and therefore lives a shameful (for a plant) heterotrophic existence.

Black Pearl Pepper by Mark Dwyer, Rotary Botanical Garden reused with permission

Montropa Uniflora stem detail. Matthew S. Staben via Wikipedia

Over at The Botanist in the Kitchen blog, Jeanne L. D. Osnas serves up a colorful nasturtium salad with a helping of explanations on the patterns plants use as ‘nectar guides’ to direct their pollinators to their sweet spots. There are also some great examples of how plants use colors that human eyes can’t see. When the pollinators are insects with the ability to see ultraviolet colors, some plants color their flowers with pigments that reflect UV rays. Take some time to chew on the fact that the flowers that bees see have patterns on them that you cannot see.

Mimulus flower photographed in visible light (left) and ultraviolet light (right) showing a nectar guide visible to bees but not to humans. By Plant Surfer via Wikipedia

Simon Norton Museum via Wikipedia

Think it’s silly that plant patterns would create such a frenzy in a species from another kingdom? Before you start to feel too superior, consider the tulip. Fortunes were traded over the newest colors and patterns of tulips in the late 17th century in the Netherlands. Shown at the right is a picture of the Semper Augustus. This tulip is famous for being the most expensive tulip sold during the tulipomania in the Netherlands in the 17th century. The highest sums were traded in speculation over bulbs producing the striped or variegated varieties, but the underlying cause wasn’t superior genetics. Read this post by Suzi Claflin on the Direct Transmission blog that describes the virus that caused the hullabaloo.

It isn’t all elaborate chemistry and genetics behind the colors plants use. The most interesting expressions of color are the polish of shine and the shimmer of iridescence, where the illusions are a trick of physics. For more on what this is, check out Anne Osterrieder’s post on structural color on the AoB blog. It may seem like something from science fantasy, but this earthly phenomenon is real and the research subject of Dr. Heather Whitney as she writes in this blog post. The shiniest living things on Earth are the fruit of Pollia condensate. As Ed Yong writes on his Not Exactly Rocket Science blog, they look more like Christmas decorations than edible fruit. Even certain seaweeds and algae are iridescent as illustrated in this post on the Coastal Pathogens blog by Michiel Vos.

Pollia condensata Credit: Juliano Costa via Wikipedia

For some plants, a single color is not good enough, and they change color when environmental conditions change. The most familiar of these is the spectacular display deciduous forests put on each autumn. I’ve written about the biochemistry behind that event on this blog previously. Gardeners may also be familiar with the fickle hues of hydrangeas. Read this post at the Reaction of the Day blog for a refresher on pH and this plant’s pigments. Poinsettias are also good at telling the pH as described in this post at the Compound Interest blog.

Hydrangeas in France Credit: Ookwormbay7 via Wikipedia

Plants are only one class of photosynthetic organism, but they are far from the only ones prone to pageantry when it comes to pigments. Remember the horse of a different color from the Emerald City in Oz? The cyanobacterium Fremyella diplosiphon is a real-life version that changes its color based on its environment. If you’re curious how and why they do it, check out my post from earlier this week. Even on a macroscopic scale, there is plenty of algal color diversity to be found under the sea as shown on this post by Michiel Vos on the An Bollenessor blog.

I think this linkfest has literally spanned the spectrum on the use of color by photosynthetic organisms. If you enjoyed this month’s Berry Go Round, check back next month for the next edition at the Roaming Naturalist’s blog exploring important backyard plants.

UPDATE: Be sure to check out this link from Jessica Budke at Moss Plants and More. It’s not just about the color plants use, but the colors plants ‘see.’ And this latest post from The Botanist in the Kitchen blog about botanical dyes.


Armored Autotrophs

Algae can be considered the lowest of the low, the most basal level of the ecosystem. Called pond scum and otherwise considered green and slimy, algae may hold a place at the bottom of the food chain, but it would be a mistake to think they were weak and defenseless. Some algae have elaborate coats of armor made of either calcite or silica to give them a rigid structure in their aquatic environment.

Gephyrocapsa oceanica Kamptner from Mie Prefecture, Japan. SEM:JEOL JSM-6330F. Scale bar = 1.0 μm. Photo by NEON ja, colored by Richard Bartz

Coccolithophores are algae with golden-brown chloroplasts because of the presence of the pigments diadinoxanthin and fucoxanthin. Emiliania huxleyi is a well-studied species of coccolithophore, which is abundant in the world’s oceans and also forms massive blooms under favorable conditions. These organisms make an exoskeleton of calcite plates that looks like a collection of armored discs over the cell surface. These coccolith scales are continually shed into the ocean as the algae grow and divide. Of course, this coat of armor must be translucent to allow for visible light to penetrate to the chloroplasts where photosynthesis occurs. They must also be somewhat porous to allow for the uptake of carbon dioxide and other nutrients. They may look like alien spacecraft, but you may be more familiar with these organisms than you might expect, as they are the main components of chalk and chalk-based rock formations.

Diatoms arranged on a slide credit: Wipeter via Wikipedia

Other algae prefer to make an armor of silica. A thin layer of glass may not seem like an appropriate substance for fortification, but it is sturdier than the typical biological membrane. Diatoms use this strategy in seemingly infinite variations in form.* While the shapes may change, the basic architecture is the same; in that, these glass houses are comprised of two halves or frustules (science word of the day) that fit together like a pill box. The top half (called the epitheca) is slightly larger and fits over the bottom half (called the hypotheca) so that the algal cell is completely surrounded by rigid silica, but with some flexibility. These two halves allow for the algae inside to divide without breaking their protective shell. Upon cell division, each new algal daughter cell takes one of the parent frustules to be its epitheca valve. The new daughter cells create their own hypotheca within about 10 – 20 minutes. For those of you paying attention, this means that over the course of several cell divisions, the daughter cells that inherit the parental hypotheca (which then becomes their epitheca) will be smaller than those that inherited the larger epitheca from the parent cell. At some point the size of the frustule must be restored to its larger typical size and the algae produce auxospores, which lack the silica frustules. During this part of the life cycle, the algal cells swell to a larger size and create a new frustule of maximum size. Each of the frustules also contains numerous pores to allow for the exchange of gases and nutrients at the cell membrane because the single slit where the two halves come together is insufficient.

These coats of armor come at a cost to the algae because it makes the organisms denser than the surrounding aqueous environment. In other words, they are constantly sinking in the water column, just as anyone else wearing a coat of armor would do. This is a problem when they still require access to sunlight to fuel their photosynthetic lifestyle. Consequently, they are at the mercy of water turbulence created by the wind to remain within the appropriate zone in the water column. This leads to a cycle of bloom and bust for their reproduction and existence in their environments. The algae have some strategies to keep their coats of armor from completely weighing them down into the dark abyss and extinction. As mentioned above, they can undergo elaborate life cycles, parts of which abandon their armor during which time they would float higher in the water column. The fanciful shapes of some diatoms also optimize the lift they receive from wave action and water mixing to increase their chances of getting closer to the sunlight. Others can modify their lipid content or ionic content of their central vacuoles to create more buoyant cells within their heavy shells to slow their sinking.

Even those autotrophs on the small end of the size spectrum have elaborate defense systems. Diatoms and coccoliths prove that even Medieval-style fortification can be compatible with the photosynthetic lifestyle.


*For more beautiful images of diatoms, check out the Flickr feed of the California Academy of Sciences.

This post was written for the February edition of Berry Go Round, Botanical Warfare: The Parasites, Stranglers, Chemists and Thieves. Click here if you’d like to read more about botanical battle tactics.

References and Links:

For more diatomaceous microscopy art:

Diatoms may also be a useful measure of environmental health: