When water turns red, would you swim here? “Bioluminescent dinoflagellates (Lingulodinium polyedrum) lighting a breaking wave at midnight. The blue light is a result of a luciferase enzyme (like firefly luciferase, but the enzyme in L. polyedrum shares no similarity with that of the firefly enzyme). Under the right conditions, the dinoflagellates become so numerous that the water takes on a muddy reddish color (hence the name ‘Red Tide’). The bioluminescence is only visible at night. The photo was taken 6/26/2005 with a Canon Rebel XT – 6s, f5.6, ISO 1600, 85mm (135mm equiv).” Photo #1 by Mike (msauder)

Bioluminescent dinoflagellates producing light in breaking waves. According to these FAQs, “Blooms are commonly called red tides, but scientists prefer the term ‘harmful algal blooms’ (or HABs). The term red tide erroneously includes many blooms that discolor the water but cause no harm, and also excludes blooms of highly toxic cells that cause problems at low (and essentially invisible) cell concentrations. Therefore, harmful algal bloom is a more appropriate descriptor.” Photo #2 by Yikrazuul

“Red Tide Luminescence.” The Florida Fish and Wildlife Conservation Commission maintains a “current red tide” status as does Texas Parks and Wildlife. Photo #3 by catalano82

Aerial view of the Easter lakes, looking north towards Lake Starnberg. The CDC wrote, “Algal blooms can deplete the oxygen and block the sunlight that other organisms need to live, and some can produce toxins that are harmful to the health of the environment, plants, animals, and people. Harmful algal blooms have threatened beaches, drinking water sources, and even the boating venue for the 2008 Olympic Games in Beijing, China. Cyanobacteria (blue-green algae) and red tides are examples of algae that can bloom and produce toxins that may be harmful to human and animal health. HABs can occur in marine, estuarine, and fresh waters.” Photo #4 by Michael Knall

This spectacular “red tide” bloom was non-toxic (Noctiluca scintillans) at Leigh, near Cape Rodney in New Zealand. “Some cyanobacterial blooms can look like foam, scum, or mats on the surface of fresh water lakes and ponds,” according to the CDC. “The blooms can be blue, bright green, brown, or red and may look like paint floating on the water. Some blooms may not affect the appearance of the water. As algae in a cyanobacterial bloom die, the water may smell bad.” Photo #5 by Miriam Godfrey via Science Education Resource Center Carleton.edu

“During the first week of August 2005, the FWC’s Fish and Wildlife Research Institute (FWRI) received reports from diving and fishing charter businesses of mass deaths of fish and other reef animals offshore of Pasco and Pinellas counties. Examination of water samples from that area identified a bloom of Karenia brevis, the Florida red tide organism. Red tide had been present since mid-July in a large coastal region to the west of Central Florida. During August and September, FWRI staff participated in aerial surveys to assess the geographic extent of the bloom.” Photo #6 by FWC Fish and Wildlife Research Institute

Karenia brevis Bloom, Offshore Pinellas County, September 16, 2005. Karenia brevis is a single-celled organism belonging to a group of algae called dinoflagellates. Large concentrations of these cells can discolor water red to brown. Karenia brevis can be found in Gulf waters any time of the year, but blooms along Florida’s coastline most commonly occur in the fall. Karenia brevis produces a neurotoxin that can kill marine life, cause respiratory irritation in humans, and make shellfish unsafe for people to eat.” More about this red tide: Frequently Asked Questions About the 2005 Red Tide and Offshore Benthic Mortality Event. Photo #7 by FWC Fish and Wildlife Research Institute

Thalassiosira species Bloom, Offshore Volusia County, July 25, 2010. “During the last week in July 2010, the FWC’s Fish and Wildlife Research Institute began receiving reports of red and brown water along Volusia County’s coastline. Examination of water samples from the area indicated a bloom of Thalassiosira, a single-celled organism that belongs to the algal group called diatoms.” Photo #8 by NOAA / FWC Fish and Wildlife Research Institute

Red and brown water along coastline of Volusia County, Florida. “Blooms can discolor the water yellow to brown and may produce foam on the water’s surface. They occur year-round in Florida waters. Thalassiosira does not produce a toxin, but blooms can kill fish by clogging their gills or depleting dissolved oxygen in surrounding waters. No fish kills were reported in association with this bloom.” Photo #9 by National Oceanic and Atmospheric Administration via FWC Fish and Wildlife Research Institute

Mesodinium rubrum Bloom, Sanibel, Lee County, November 12, 2010. “In November 2010, the Sanibel-Captiva Conservation Foundation staff noted red discolored water inshore of Sanibel Island. Examination of a water sample from that area identified a bloom of Mesodinium rubrum a single-celled marine ciliate found worldwide.” Photo #10 by Sanibel-Captiva Conservation Foundation via FWC Fish and Wildlife Research Institute

Fibrocapsa japonica Bloom, Tarpon Bay Mangroves, Sanibel, Lee County, August 4, 2011. “On August 4, 2011, the Sanibel-Captiva Conservation Foundation staff noted discolored waters in the mangroves east of Tarpon Bay. Examination of a water sample from that area identified a bloom of Fibrocapsa japonica. This golden to brown alga belongs to a group of plankton known as raphidophytes. Fibrocapsa japonica occurs in coastal waters and has caused major fish kills around the world. Outside of Florida waters, F. japonica has been known to produce brevetoxins, the same toxins produced by the Florida red tide organism, Karenia brevis. No adverse impacts were reported from this bloom.” Photo #11 by Sanibel-Captiva Conservation Foundation via FWC Fish and Wildlife Research Institute

“Ciliates belong to the group known as protozoans; what sets them apart is the presence of hairlike projections from their cell wall. While M. rubrum is nontoxic, it can deplete dissolved oxygen in the waters where it forms blooms; rarely, it has caused shellfish and crustacean deaths. In Florida, no adverse effects from a bloom of these cells have been reported.” Photo #12 by FWC Fish and Wildlife Research Institute

“On May 10, 2010, during an aerial survey to assess the extent of the Deepwater Horizon oil spill in the Gulf of Mexico, staff with the FWC’s Fish and Wildlife Research Institute noted discolored water that was not oil-based, but rather appeared to be an algal bloom. Examination of a water sample identified a bloom of Ceratium, a single-celled organism belonging to a group of algae called dinoflagellates. This dinoflagellate is nontoxic but may cause oxygen depletion in the surrounding waters at high cell concentrations. No adverse effects from this bloom were reported. Ceratium can be found in cold and warm waters and from freshwater to saltwater environments worldwide. Some species are bioluminescent, meaning they light up the water with a blue glow at night.” More info about “Deepwater Horizon Oil Spill Response” here. Photo #13 by FWC Fish and Wildlife Research Institute

“In late May 2010, the FWC’s Fish Kill Hotline began receiving reports of dead and dying fish in the lower St. Johns River (St. Johns and Putnam counties). Water samples indicated high concentrations of a harmful cyanobacterium (blue-green alga) species, Aphanizomenon cf. flos-aquae.” Photo #14 by FWC Fish and Wildlife Research Institute

“Aphanizomenon is found in fresh water bodies throughout Florida, and blooms of this species are common in the St. Johns River. Blooms can appear as blue-green threads in the water column or as surface scum during summer and fall months. Aphanizomenon produces several types of toxins that can affect the human nervous system and liver. High concentrations of cells can deplete dissolved oxygen in surrounding waters, resulting in fish kills.” Photo #15 by FWC Fish and Wildlife Research Institute

Noctiluca scintillans Bloom, Offshore Walton County, February 19, 2011. “In mid-February 2011, the FWC’s Fish and Wildlife Research Institute received a report from the National Oceanic and Atmospheric Administration regarding orange discolored water and “froth” offshore from Fort Walton Beach east to Topsail (Okaloosa and Walton counties). Examination of water samples from the reported area of discolored water identified a bloom of Noctiluca scintillans. This large (1 mm diameter) single-celled organism belongs to a group of algae called dinoflagellates.” Photo #16 by FWC Fish and Wildlife Research Institute

“Noctiluca scintillans can be found along Florida’s Panhandle and Space Coast. Large concentrations of cells appear orange-red to brown in daylight, varying with the color of the phytoplankton on which N. scintillans feeds. At night, N. scintillans lights up the water with a blue glow through bioluminescence. No negative effects from blooms of N. scintillans in Florida waters have been reported.” More information here. Photo #17 by FWC Fish and Wildlife Research Institute

Kryptoperidinium foliaceum Bloom, St. Petersburg, Pinellas County, May 13, 2003. “In early May 2003, the FWC’s Fish and Wildlife Research Institute staff noted discolored water in Lassing Park. Examination of a water sample from that area identified a bloom of Kryptoperidinium foliaceum, a single-celled organism belonging to a group of algae called dinoflagellates. Unique among phytoplankton, K. foliaceum has two nuclei: its own and that of a diatom that lives within it. Kryptoperidinium foliaceum can be found year-round in many estuarine areas of Florida. Large concentrations can discolor water red to brown and can deplete dissolved oxygen in surrounding waters. No adverse effects from this bloom were reported.” Photo #18 by FWC Fish and Wildlife Research Institute

Peridinium quinquecorne Bloom, Bayboro Harbor, Pinellas County, July 21, 2010. “On July 21, 2010, the FWC’s Fish and Wildlife Research Institute staff noted patches of discolored water in St. Petersburg’s Bayboro Harbor. Examination of a water sample from that area identified a bloom of Peridinium quinquecorne. This single-celled organism belongs to a group of algae called dinoflagellates. It can be found year-round in many estuarine areas of Florida. Peak concentrations occur after rainfall heavy enough to cause runoff. Large concentrations of P. quinquecorne can discolor water red to brown and can cause fish kills by depleting the available dissolved oxygen in the surrounding waters. No adverse effects from this bloom were reported.” Photo #19 by FWC Fish and Wildlife Research Institute

Peridinium quinquecorne Bloom, Fort Myers Beach, Lee County, October 20, 2010. “In mid-October 2010, the Lee County Department of Health investigated a report of discolored water, fish kills, and foul odor on Fort Myers Beach. Examination of a water sample from that area identified a bloom of Peridinium quinquecorne. This single-celled organism belongs to a group of algae called dinoflagellates. It can be found year-round in many estuarine areas of Florida. Peak concentrations occur after rainfall heavy enough to cause runoff. Large concentrations of P. quinquecorne can discolor water red to brown and can cause fish kills by depleting the available dissolved oxygen in the surrounding waters.” Photo #20 by Lee County Health Department via FWC Fish and Wildlife Research Institute

“Crimson tide.” Freaky “blood red” waves of algae: A Noctiluca bloom in Union Bay, British Columbia. Photo #21 by Lisa M. Holm / U.S. National Office for Harmful Algal Blooms / NOAA Center for Sponsored Coastal Ocean Research

South of Cornwall, Great Britain, July 24, 1999. “Under certain conditions, Emiliania huxleyi can form massive blooms which can be detected by satellite remote sensing. What looks like white clouds in the water, is in fact the reflected light from billions of coccoliths floating in the water-column.” Photo #22 by Steve Groom / Plymouth Marine Laboratory

Inflorescence plankton. “These are a priori cyanobacteria (blue-green algae). In this case, a few hours (the next fifteen hours) after the start of the episode, the blue spots were extended. Traces in the form of streaks are traces of fish and ducks that run on water, ‘breaking’ the biofilm. The characteristic blue color of accumulation zones of blue pigments released by dead bacéries. Here the water has a consistency of ‘soup’ of 5 to 10 mm below the surface. Location: Vault dock in Lille, not far from the city center (France), after a long rainy period (not scorching, and even under the seasonal average, but with unusually mild nights). Near the channel (Deûle) is also covered with a layer of green plankton over large areas (hundreds of square meters), but much thinner. Samples have a strong smell of seaweed.” Photo #23 by Lamiot

“Ducks swimming and ‘grazing’ in an area of ​​accumulation in surface plankton priori consists of cyanobacteria (formerly classified as ‘blue-green algae’), located in the former arms of a channel now closed. Location: Quai du Vault in Lille (France), not far from the city center after a long rainy period (not scorching, and even under the seasonal average, but with unusually mild nights).” Photo #24 by Lamiot

Water blooms. Photo #25 by Shizhao

France: “Inflorescence plankton. These cyanobacteria (blue-green algae) traces in the form of streaks are traces of fish and ducks that run on water, ‘breaking’ the biofilm. Samples have a strong smell of seaweed (type spirulina). Location: ‘Quai du Wault’ in Lille, not far from the city center (north of France, a location with Google maps: 50.637485,3.05425).” Photo #26 by Lamiot

Blooms: Left: A Noctiluca bloom in the Sea of Cortez, Mexico. Top Right: A Noctiluca bloom in China. Bottom Left: This massive “red tide” of the dinoflagellate Noctiluca stretched for more than 20 miles along the southern California coast. Non-toxic blooms such as these can cause extensive mortalities of plants and animals in shallow waters when the bloom biomass decays, stripping oxygen from the water. Bottom Right: A red tide. Photo #27 by M. Gaskins / NOAA & #28 by M. Zhou / NOAA & #29 by P. Franks / NOAA & #30 objetivo

Red Tide, La Jolla, California. Photo #31 by eutrophication&hypoxia

Algal blooms Southern Florida and the Florida Keys, December 2, 2003. Photo #32 by Jeff Schmaltz, MODIS Rapid Response Team, NASA / GSFC

Greenish phytoplankton swirls in the dark water around Gotland, a Swedish island in the Baltic Sea. Photo #33 by Landsat 7 / NASA

Algal bloom by Noctiluca in Isahaya Bay. Photo #34 by Marufish

Left: A freshwater red tide in the Italian Alps, species unknown. Right: Cameron Creek had turned blood red from sediment, not algae this time. Lower: Scripps La Jolla Algal Bloom 2011-09-29. Photo #35 by NOAA & #36 by The Jet Backpacker & #37 by Derek Hofmann

“Red Tide” luminescence is not red, not a red tide either, but instead glowing blue mats of floating algae called phytoplankton. Photo #38 by catalano82