As expected, August was a month with elevated temperatures and little rain in most areas of the state. This led to an influx of questions on the identification, control, and testing of blue-green algae directed to the Aquatic Diagnostics Laboratory (ADL).

The common name “blue-green algae” is a little misleading for cyanobacteria species since they are in fact, photosynthetic bacteria that can have many different growth forms. Some cyanobacteria species considered to be similar to true planktonic algae species and are mixed evenly throughout the water column, not giving off any visual cues. Other, more visible cyanobacteria species can be found floating around the shoreline in various growth forms, largely characterized as “spilled paint”, globules, or mat forming. Furthermore, noticeable cyanobacteria blooms are not always “blue-green”. They can appear green, yellow, brown, red, purple, etc. due to protein complexes that produce various pigmentations in their cells.

See below for several examples.

Cyanobacteria should not be confused with golden alga (Prymnesium parvum) or Euglena (Euglena spp.).

Golden alga are pigmented to give off a golden appearance, and are commonly found in waters with high salinity or rich in minerals during cooler months.  While golden alga blooms do produce toxins and pose a threat to aquatic organisms, there is no known direct threat to humans, wildlife, livestock, or pets. Whereas, Euglena can be found in any water body and even soil. Euglena are unique in the fact that they can change color rapidly depending on sunlight, going from green to a rusty red within minutes. A good indication that a pond is experiencing an Euglena infestation versus a cyanobacteria bloom is the water changing color within a 24 hour period, becoming more red with more sunlight.

Sometimes to the untrained eye, a cyanobacteria bloom may also be confused with what is actually an infestation some of the world’s smallest flowering plants, watermeal (Woffia spp.).  Like some cyanobacteria species, they are bright green and can be found heavily concentrated along the edges and in downwind areas of a pond. However, upon closer inspection, watermeal will have a seed-like appearance with a gritty texture.

These common misidentification mistakes may seem irrelevant but each of these groupings have unique survival strategies which plays a huge role in management.

There are no reporting or monitoring programs for cyanobacteria at the state or federal level in private waters. If you believe that you are experiencing a fish kill related to cyanobacteria issues, you should contact the Texas A&M AgriLife Aquaculture Extension Specialist, Dr. Todd Sink . The ADL can test for cyanotoxins in water but testing is expensive and does not always lead to definitive answers. See “Texas A&M AgriLife Aquaculture Specialist Addresses Algae-related Dog Deaths” for more information on testing.  The ADL does not test fish tissue. Cyanobacteria issues involving wildlife or livestock can be directed to the Diagnostic Toxicologist at Texas A&M Veterinary Medical Diagnostic Lab, Dr. Catherine Barr, and Texas A&M AgriLife Extension Specialist, Dr. Thomas Hairgrove. To a confirm that cyanotoxins are the cause of death for livestock or wildlife, a necropsy is recommended over a water sample. More information on the management of cyanobacteria, can be directed to the Texas A&M AgriLife Aquatic Vegetation Management Program Specialist, Brittany Chesser.

References & Resources:

AgriLife Today

AquaPlant

EPA: Cyanobacterial Blooms

SRAC: Algal Toxins in Pond Aquaculture

TPWD: Harmful Algal Blooms

When it comes to managing aquatic vegetation, the first critical step in selecting an effective control method is identification. Individual treatments do not work across all, or even most, aquatic vegetation species. Selecting treatments before proper identification can result in an ineffective treatment and a waste of money, time, and labor.

Thanks to current technology, specifically the widespread use of cell phones with high quality cameras, pond owners can forgo collecting a plant specimen and sending it in the mail. This is good news as plant material and Texas heat do not mix well. Mailing usually leaves the recipient with a smelly, decomposing plant, which can make identification hard. Instead, photos of the unidentified plant can be taken and sent directly using a phone, computer or tablet.

The main caveat of plant material being physically absent during identification is the requirement of high quality photos. Some plants, especially those with large, showy flowers, can be identified from a far, however as you can see from the photos below, this is not usually the case and closer inspection is required.

So, what classifies as high quality? Photos should be taken to highlight key characteristics like flowers, leaf arrangements, and nodes (stem area from which a leaf or leaves, branch or branches originate). The unidentified plant should be taken out the water, placed against a contrasting background (preferably white), with stems and leaves spread out. The photo should then be taken up close (preferably within 1 foot, or until the plant fills the frame), with the plant material in focus, and eliminating any shadows. Including scale items, like a hand, coins, or other readily available items, will also help for size comparison. See below for examples.

Additional information like pond use and overall goals, along photos of the plant material relative to the water column (emergent vegetation) and coverage area (all vegetation types), will help provide more guidance when coming up with a management plan.

For more information on aquatic vegetation identification, please visit AquaPlant or contact the Aquatic Vegetation Management Program Specialist, Brittany Chesser (Brittany.chesser@tamu.edu).

Planktonic algae, otherwise known as phytoplankton, are microscopic, single celled, free floating algae that can exist wherever the sun penetrates. Planktonic algae thrive under sunny conditions at water temperatures greater than 60°F, and contributes to water’s greenish tint. Typically, planktonic algae are considered desirable as they shade the pond bottom which suppresses the establishment of rooted aquatic plants, are the foundation of a pond’s food chain by providing food for zooplankton and larval fishes, and provides 80% of the oxygen in the water.

However, an overabundance of planktonic algae, called “Blooms” – particularly their eventual death – can lead oxygen depletions, and eventually fish kills. Planktonic algae can die-off naturally and rapidly due to cloudy days and cold snaps during rain events or colder months. After the algae cells die, they begin to lose their chlorophyll and green coloration. This is why a tell-tale sign of a die-off is a change in water color, in streaks or entirely, from green to brick-red, brown, or black, and can give off a foul odor. Ultimately, these dead cells will settle to the pond’s bottom, giving the pond a clearer appearance. These dying cells are not only a nuisance aesthetically; beneficial bacteria require oxygen to break down these cells. This lowers the amount of oxygen available to fish and other aquatic organisms.

Samples that are sent in to the Aquatics Diagnostic Laboratory after a planktonic algae die-off, may contain these dead, discolored cells, which are confirmed through microscopic examination. Additionally, samples can have high total ammonia nitrogen (TAN) concentrations through the algae decomposition process. During warmer months or in high pH ponds, high TAN is a serious issue that may lead to a fish kill due to unionized ammonia (UIA) levels. UIA is toxic to fish and concentrations are dependent on TAN, temperature, and pH. Therefore, when the water temperature is cool and pH is low, high TAN levels will result in low UIA and pose little risk to fish.

Negative effects of a planktonic algae die-off can be minimized by stopping all fish feeding until spring when the water temperatures are 60°F or higher. Feeding during winter months (<60°F), when fish are eating less, can contribute to excess ammonia in the pond from protein in uneaten feed and excess protein in feces. An aerator can also be added to increase overall dissolved oxygen and reduce the chances of a potential fish kill. Regardless, stress put on fish due to decreased water quality conditions can lead to secondary diseases.

If you are concerned your planktonic algae bloom density is problematic, a secchi disk can be used to measure water clarity, which can help indicate planktonic algae levels. For more pictures and information on planktonic algae, please read Managing and Controlling Algae in Pond and visit AquaPlant.tamu.edu.

Streptococcosis, also known as strep, is the term for diseases caused by a genus of bacteria, Streptococcus. These bacteria are known to be very aggressive in fish causing large die-offs of over 50% mortality within a few days, hindering production and causing massive economic loss.

Aside from rapid and increasing mortality, fish suffering from strep can exhibit a long list of potential symptoms but hemorrhaging, “pop-eye”, and swimming or behaving abnormally, such as spinning, are commonly observed. Erratic behavior can be one of the first tell-tale signs, due to infection of the brain and nervous system, but not all infected fish are symptomatic.

Like most other diseases the key to prevention is minimizing stress, which can be achieved by avoiding crowded stocking conditions and poor water quality. These conditions should particularly be avoided during summer months when water temperatures are at their highest. Commonly stocked fishes like largemouth bass, bluegill, striped bass, golden shiner, channel catfish, and tilapia are found to be susceptible to strep infections.

To prevent further spread, reduce overall mortality, and minimize economic loss, fish should be isolated from other populations immediately if strep is suspected. If a strep confirmation is made rapidly and fish are readily accepting feed, an antibiotic may be prescribed. Sometimes strep can become a reoccurring issue and vaccinations are needed, although not always available or effective.

Fish suspected to have a strep infection can be sent to The Texas AgriLife Extension Service Aquatic Diagnostic Laboratory for a gram positive streptococci selective media isolation to confirm diagnosis.

For more pictures and information on strep, please read Streptococcal Infections in Fish.

It’s that time of year when water temperatures are reaching 60-65° F, and pond owners are hearing now is the optimal time for pond fertilization. Fertilizing a pond is different than fertilizing a field and requires using a fertilizer that is high in phosphorus rather than nitrogen. When done correctly, pond fertilization can provide many benefits including enhancing the overall food chain by providing food for phytoplankton which in turn allows the pond to produce more pounds of fish. Additionally, fertilization can reduce the presence of submerged aquatic vegetation by decreasing water clarity and limiting the amount of light that reaches the pond bottom.

As temperatures begin to warm up, pond owners may begin to look forward to stocking their ponds. One of the most common questions we get from new and experienced pond owners is “What tests should I get to determine if this pond will support a fishery?”. Usually when this question is asked, there are no obvious indicators to point pond owners in the right direction, which can lead to endless internet searches, leaving their heads spinning with a long list of tests and their associated costs.