Science Corner: Toxic Algae, aka Cyanobacteria

Kristie Ehrhardt • April 23, 2024
Photo by Centers for Disease Control

It seems to be a fairly familiar summer local news story; beware - toxic algae may be present in neighborhood ponds. Often called toxic algae, in reality, it’s not an algae at all that threatens our summer fun; it is Cyanobacteria.


Blue-green algae is often given credit for changing Earth’s lifeforms by being the first known organism able to photosynthesize and produce oxygen - the basis of life on Earth. They are among the oldest known organisms with fossil records that date back over two billion years ago. However, blue-green algae isn’t an algae at all, it’s actually a specialized bacteria and belongs to one of the most numerous taxon - Cyanobacteria. Named for their color and identified by their pigments and ability to photosynthesize, they are an extremely important component in marine food webs. They naturally occur in fresh, brackish and marine environments and thrive in low oxygen environments. This charismatic bacteria that kick-started life as we know it also contains lethal toxins that can also be deadly to pets, people, livestock and wildlife.


When the weather gets warm, isolated bodies of water such as retention basins, stock ponds and even unmaintained backyard pools and fountains become stagnant. Nutrients from over-fertilizing and then over-watering lawns and gardens run off and can collect in neighborhood retention ponds causing eutrophication - when organisms such as algae and bacteria reproduce explosively in warm, nutrient rich waters depleting the oxygen level and resulting in environmental degradation. The optimal conditions for a cyanobacteria bloom.


Warm, oxygen deprived water brimming with organisms that thrive in these conditions can result in an overabundance or “bloom”. Some cyanobacteria contain lethal toxins and when present in out of control numbers decompose aquatic ecosystems and can cause potentially lethal intoxication of pets, people, livestock and wildlife if they come into contact with it. Cyanobacteria is too small to be seen with the naked eye but when conditions result in a bloom, gobs of bacteria collect on the surface of the water and may look like mats of floating vegetation, foam, pond scum, or even a film of paint or oil floating on the water. Colors range from vibrant greens and blues to yellow, red and brown and sometimes the mats sink which causes the water to smell like rotting vegetation or worse.



Cyanobacteria can produce different types of toxins including liver and neurotoxins which can cause serious illness and sudden death. Dogs are especially at risk because of their infatuation with water, the stinkier the better (according to them). They can ingest cyanobacteria by drinking contaminated water directly or by simply fetching an object that was tossed into the water. They can also get it just from licking the bacteria-laden water off of their wet paws and fur. Depending on which type of toxin they were exposed to, symptoms can arise less than 15 minutes to a couple of days after exposure and may include diarrhea or vomiting, drooling or foaming at the mouth, jaundice and neurologic signs such as weakness, disorientation, seizures and difficulty breathing. If you know your dog was in contact with cyanobacteria, immediately and thoroughly rinse them off with fresh water and urgently get them to the veterinarian. If caught very early, the vet may be able to flush out the toxins.

To help keep you and your dog safe, keeping them leashed around water, especially if it appears dirty, foamy or has mats floating on top is always a good idea and bring plenty of fresh water for them to drink. Although not all cyanobacteria is harmful, there are no clinical tests, designated treatments or antidotes so when in doubt, keep them out.


-Kristie Ehrhardt (kehrhardt@tuleyome.org)

Tuleyome Land Conservation Program Manager

RECENT ARTICLES

Wildfires and California Oaks – Nature and You Lectures

By Geoff Benn • October 7, 2026
Blue oaks on the Berryessa Peak Trail. Photo by Geoff Benn. Our September Nature and You speaker was Tuleyome Education Associate Geoff Benn, who gave a lecture on one of his favorite subjects, California’s amazing oaks. In the lecture, Geoff discussed how California’s oaks evolved and how they deal with a range of challenges, including drought, fire, and diseases. If you missed it, be sure to check out his talk here. 

Welcome Interns!

By Geoff Benn • October 7, 2026
Interns Deana Martinez, Yaquelin Gonzalez, Gabriella Limon, Ben Hubbard, and Keira Lazaro at Woodland Regional Park Preserve. Tuleyome is excited to welcome our largest ever cohort of interns, including four Horticultural Interns and one Communications Intern! Our Horticultural Interns are paired with volunteer mentors at Woodland Regional Park Preserve where they learn about managing invasive plants and monitoring populations of rare native plants. This year’s mentors are Jennifer Hogan and Teri Barry, both longtime volunteers and leadership team members at the Preserve. Our Communications Intern works closely with Program Director Nate Lillge to shape and execute our communications, including social media, e-newsletters, and more. Keep reading to meet each of our interns: Horticultural Intern Yaquelin Gonzalez has lived within the bounds of Sacramento County her whole life, where her mother’s garden and love for rock collecting sparked her appreciation for nature. Her desire to enter the environmental field was further fueled via nature-based field trips during elementary school. After high school, she began studying at American River College and eventually transferred to the University of California, Davis in 2025 to study Environmental Science and Management, focusing on Ecology, Biodiversity, and Conservation. Here, she has gained an interest in soil science as well as plant ecology and hopes to pursue a research career in restoration ecology. In her spare time, she likes to go on nature walks, play the guitar, read, bake, and listen to podcasts. Horticultural Intern Ben Hubbard grew up in Roseville, California where he spent a lot of time outdoors with friends, competing in sports, hiking, as well as instructing elementary school field trips about the environment, specifically wetlands. He just recently transferred from Sierra College to the University of California, Davis and is working towards completing his Bachelor’s degree in Environmental Science and Management with a specialization in Ecology. When he completes his education, he hopes he can make a difference in the world and help to preserve wildlife and natural land for the next generation to enjoy as much as he has. When he’s taking a break from studying you can find him practicing with his recreational sports team, grabbing a coffee, hiking, enjoying a good story, or just hanging out with friends. Horticultural Intern Keira Lazaro is a third year undergraduate at University of California, Davis where she majors in Environmental Toxicology. She’s specializing in pharmacology and biotechnology with hopes to work in a research lab on specific pathogens that attack native California crops. She is also a part of the University Honors Program in Davis and is taking the first couple of steps towards her fourth year signature work on the oxidation chemistry behind electronic cigarette devices, specifically with exposure in indoor environments. Keira grew up in Los Angeles County and hopes to find a career in Southern California once she graduates. When she is able to go back home she spends most of her free time at the beach or hiking. Communications Intern Gabriella Limon grew up in Bishop, California, within the Sierra Nevada and Owens Valley where she became connected with wildlife and stewardship. She spent her later teenage years in Southern California and committed to the University of California, Davis, where she is currently pursuing a Bachelor's Degree in Environmental Policy Analysis and Planning with a focus on conservation management. In addition, she is also a scholar staff member of the UC Davis Women’s Resources and Research Center where she provides STEM-based programming and academic support to students of marginalized identities. Gabby is especially passionate about wildlife justice, land protection, and environmental education. She spends her free time writing, playing video games, tide pooling, hiking, and logging critters. Horticultural Intern Deana Martinez grew up in Arbuckle, California, surrounded by rice fields and almond orchards, which grew her interests in agriculture. She is currently in her 4th year at the University of California, Davis, where she is pursuing a Bachelor’s Degree in Entomology with a Soil Science minor. Along with classes, she is involved in a Nematology research lab, working with plant parasitic nematodes and their interactions with common crop systems in California. She has also held a student position with the Plant Biology research greenhouses as a technician for the past 3 years. Outside of school and work, Deana enjoys hiking, reading, and spending time with her family.

Policy Corner: California Fights Back on Endangered Species Protections

By Shai Demus • October 7, 2026
California’s condors and sea otters are two of conservation’s great comeback stories – species that were once on the brink of extinction and have rebounded thanks in large part to the Endangered Species Act (ESA). That 50-year-old law is now facing one of the most significant rollbacks in its history, and California is fighting back in court. Last week, Attorney General Rob Bonta, joined by a coalition of 21 state attorneys general, filed two lawsuits challenging the Trump administration’s recent changes to the ESA. At the center of the fight is a single but enormously consequential change: the administration rescinded the longstanding definition of “harm” under the Act – a definition that, since the early 1980s, has made it illegal to destroy or damage the places endangered species live, breed, and feed. Without it, habitat destruction itself may no longer count as illegal “harm” to a species, even though most biologists agree habitat loss is the single biggest threat facing endangered species today. The changes don’t stop there. The administration is also making it easier for federal agencies to avoid designating “critical habitat” for at-risk species, and it has eliminated automatic protections for newly-listed threatened species – meaning wildlife officials must now write custom protection rules for each species one at a time. That’s a heavy lift for an agency that has reportedly lost more than a third of its staff, and which currently has 400 species waiting for a protection decision. Why this matters here at home California is home to more threatened and endangered species than any other state. It’s natural to assume the state’s own Endangered Species Act would fill any gap left by federal rollbacks – but legal experts point out that California’s law, as written, doesn’t clearly protect habitat at all. It primarily prohibits killing or injuring individual members of a listed species, not damaging the places they live. That means the very thing under threat federally – habitat protection – may not have a reliable backstop at the state level either. What this means for our work At Tuleyome, so much of what we do, protecting oak woodlands, wildlife corridors, and watershed habitat across our region – depends on the basic principle that a species' home matters as much as the species itself. A condor or a Clear Lake hitch can’t survive court-ordered protection from hunting alone if the habitat it depends on is quietly bulldozed, drilled, or logged out from under it. This lawsuit is about defending that basic principle at the federal level, and it’s a reminder of why local land protection and legislative advocacy matters now more than ever – because the safety net above us may have real holes in it.