Information in this section is from the 2003 Golden Alga Workshop and was current at that time. Please see the main Golden Alga page and Current Bloom Status for up-to-date information.

Golden Alga Workshop

Presentation Question & Answer Sessions

Speaker panel at Golden Alga WorkshopJoan Glass: Historical Review of Golden Alga (Prymnesium parvum) Problems in Texas

When you look at historical patterns, are they [fish kills due to toxic golden alga] moving east/west or randomly occurring?
The Pecos came first and then the Brazos. (Both have seen fish kills related to golden alga for years.) We’re not sure if it’s [golden alga] being moved or was already there. The dead fish look like a low dissolved oxygen kill, so it is often misidentified. We have a limited understanding on if P. parvum is endemic or introduced and a poor baseline to make conclusions.

What about silicon in the region?
It appears to be decreasing due to damming in the rivers according to some studies. There is currently not a good answer to this question. Patterns appear similar in Texas and Sweden, but this has not been studied for P. parvum due to funding limits.

Is there any data indicating why a pH in excess of 7 is significant?
The toxin does not finish forming in low pH; it requires cations, and they aren’t available when pH is below 7. This explains part of the reason the toxin is not there.

Have you developed any intuition or suspicion about where or when the next toxic golden alga [bloom] will happen?

Greg Southard: Overview of Texas Hatchery Management of Golden Alga, Prymnesium parvum

What about treatment following an ammonia shock?
With existing high levels (>0.2 mg/L un-ionized ammonia), adding additional ammonia will not help.

What size are the hatchery ponds?
About an acre.

Does continuous piping connect the ponds at a hatchery?
There is a common water supply to the hatchery ponds.

Do cutoffs exist to segregate the flow pond water, or is there continuous flow through?
We have a mechanism for cutting off flows (i.e. water does not flow from one pond to another).

Once a pond is clear how often does it become reinfested?
The pattern is unknown and random. We have seen recurrence within 2 months if a cyst stage is present. It appears to be dependent on water quality.

Bente Edvardsen and Aud Larsen: Phylogeny, Life History, Autecology and Toxicity of Prymnesium parvum

Do we have any idea of how long the cysts are viable?
Very little is known; they have only been found in a few locations in Norway. Blooms have occurred there every year from 1985 to 1995. It is believed the cysts can live through the winter.

Why avoid aeration?
Toxin production can increase dramatically during aeration. This should be avoided!

Do you ever collect enough cysts to run a ploidy analysis?

Under low toxicity, one organism eats the other; under high toxicity, the situation is reversed. Are there any indications why this happens?
Toxin production could be a function of grazer protection, or allelopathy. For example, at low toxin levels, grazers eat P. parvum; at high toxin levels, P. parvum eats others, including the grazers.

How does P. parvum protect itself from its toxins?
We don’t know at this stage. Cholesterol may play a role.

Carmelo R. Tomas: Prymnesium parvum: An Overview and Questions

Do hatcheries in Texas have the capability to reduce bloom potential by drilling freshwater wells? (Would the bloom potential be reduced in Texas by drilling freshwater wells?)
The Elizabeth City, NC resolution was only successful when it [the facility] was re-flooded with fresh water, dropping salinity to virtually zero. (TPWD Hatchery Personnel, post-conference: The groundwater around the affected hatcheries is brackish, making this a nonviable solution for us.)

What happens during the dark cycle? What is being regenerated at night?
Some toxin genes are turned on just before daylight. The dark cycle may be a recharge or a trigger that activates an aspect of the physiology of the organism.

What agents have been used to combat P. parvum?
In Artesian Aquafarms (4 ppt salinity water), Diuron and Loicidyn were both effective but illegal in the concentrations necessary. Loricidyn (a ham-curing product) was effective and approved.

Do you know anything about brood stocks for the ponds?
Private aquaculture isn’t always comprehensive about record-keeping and sometimes forgets to mention certain variables. Insuring that no other water was coming into the facilities was a problem in North Carolina. By being close to the Atlantic in Elizabeth City, part of the introduction could be the result of birds. Introducing fry might be another. We really don’t know, but there are 2, possibly 3, ways this might have been introduced.

Richard L. Kiesling: Analysis of Prymnesium parvum Blooms in Lake Whitney, Texas

Were nutrient bioassays included?
Single assays were performed.

Did you have a total nutrient control in the experimentation?
No full nutrient controls were performed.

Have you considered nutrient bioassays by exclusion?
We have never done this. It should be discussed and pursued. It looks promising.
A limited number of replicates that could be run on an exclusionary basis should be considered.

How much chlorophyll was generated in blooms?
15 -10 micrograms/liter. Typically, one approach that works in a study like this is adding three to five-fold amounts of ambient nutrients to avoid stressing the populations. Managing phosphorus production should reduce bloom production. This is an important takeaway message.

Were the incubations stirred or mixed in any fashion?
Achieving replication or maximum growth is the main objective here. Algae don’t respond well to any handling or storage conditions, although they are pretty good at adapting to nutrient pulses. Bioassays are done in large pools that are gently mixed. All bioassays are somewhat artificial. It is believed that there are nutrient effects on the bloom. This must be studied further. “Dinoflagellate whiners” can pose a challenge!

Edna Graneli: Kill your Enemies and Eat Them: The Role of Prymnesium Toxins

What are the observations from reservoirs and lakes on the phytoplankton community during a bloom? Are the blooms initially monospecific?
Glass: When the blooms start, we have mixed communities, and the toxicity is low. As they progress, the toxicity increases, and the community becomes monospecific.

Paul Kugrens:Prymnesium parvum Laboratory Studies: Structure, Reproduction, Salinity Tolerance and Bioassay

Have you found the small, immobile cells in the Colorado research?
Cyst-like structures ¾ the size of a cell have been identified in some of the Texas samples. They are not orange but rather greenish with very small chloroplasts.
The variability in the organism, depending on the geographic location it originates from, is remarkable. The Wyoming strain has distinctly different shapes than Texas and Colorado samples.

How was the Colorado fish kill attributed to Prymnesium?
The head fish pathologist contacted Texas. The Colorado organism was a similar shape (i.e. a Chrysophyte) but not Prymnesium.

Has any DNA sequencing been completed on the Wyoming sample?
Not yet. Blame Wyoming.

Linda Medlin, Gundula Ellers, Kerstin Toebe, and Katja Kerkmann: Rapid Tests for the Detection of Prymnesium parvum and Its Toxins

What is the limit of detection on the hand-held unit?
60 cells/liter is the lowest field sample limit of detection.

Could the filter be rotated for solid phase assays?
No, the shape of the probe limits rotation and interferes with measuring oblong cell shapes.

Donald M. Andersen and Mario R. Sengco: Bloom Control Strategies for Harmful Algal Blooms

Why does the requirement for only using incinerated clay in Europe exist?
There is nothing similar in the United States. European clay incineration is a requirement to kill nematodes for tulips.

How much clay per acre is recommended?
350-400 grams/square meter is the loading amount for per unit area. This clay will only be effective in the top 4 meters. Tiny particles have to flocculate to be effective. The Koreans are using much higher concentrations and are achieving success.

How does the clay treatment affect cyst formation?
There are two issues. Cyst-forming dinoflagellates take days to form and reproduce. This won’t happen in the two hours of a clay treatment. Temporary cysts that occur in the life cycle may remain dormant for longer periods. This has not been noted in the Woods Hole research, but some freshwater dinoflagellates may exhibit different behavior. Closer study is needed.

Marine hard clam studies are radically different organisms than rare and endangered freshwater mussels. Silt is a problem for them [rare and endangered freshwater mussels]; clay may be devastating.
Situational triage may have to be put in play. Responders must decide which is worse: a Prymnesium bloom or the effects of the clay. Remember, we will not be talking about a pristine environment when making these calls. More valid comparisons should be made with the effects of red tide and algae blooms.

At what water depths have the Koreans achieved success?
15-20 meters deep with good flushing. The clay does not persist with tidal patterns. They have not seen a major re-bloom of algae following major treatments. Consistently reducing the bloom cysts may reduce the propensity for future blooms (1995-1996). Korean fisheries are a $1 billion industry that has sustained over $1,000,000 in red tide losses.

Is there evidence suggesting there is a rebound of species after applications?

What permits are required for application?
Environmental Protection Agency/FIFRA (Federal Insecticide, Fungicide, and Rodenticide Act) permitting has been required. Additional permits have been obtained from the Florida Department of Environmental Protection. The issue in Florida is closely linked to phosphatic clay (a mining byproduct and a toxic waste). There is concern that by offering permits for limited small-scale application in Florida, additional requests may be triggered to dump 100,000 times that amount into the Gulf of Mexico by mining interests who want to dispose of a byproduct. This would be a problem.

How important is multiyear funding?
Critical. [$1.2 million] is not a lot of money. It is crucial to establish recurring funds for ongoing monitoring. Recurring general revenue funding is the best of all possible worlds.

Jan Landsberg: A Review of Fish-Killing Microalgae: Causes, Impacts, and Management with Emphasis on Prymnesium

Since the Israelis have a limited supplies of freshwater, is dilution less of an alternative there?
Most systems are brackish, and there is less access to freshwater. In Texas the question is less one of access than of timeliness. Freshwater for dilution near hatcheries does exist, but it has to be delivered rapidly in order to dilute blooms if it is to be effective.

Do you know how often the Israelis monitor (daily or some other schedule)?
It generally depends on the individual farmer and his area of responsibility. They have become more proactive in identifying emerging problems. In the past, most of this was triggered by fish behavior. There may be a brief window of opportunity for treatment (2-3 hours in the morning to afternoon) if response is rapid. Treatment and recovery can be possible if the symptoms are recognized and acted upon quickly. Fishermen do most of the monitoring themselves, and there is a much greater recognition of the problem. The smaller systems there lend themselves more readily to monitoring and treatment.
One of our strategies should include increasing the size of the volunteer monitoring.

Shrimp farms exist along areas of the Pecos that have experienced P. parvum blooms. Is there any reason NOT to expect shrimp mortality if there is a P. parvum bloom?
We would expect them to be affected. If they are NOT, it would be a basis for further study. The sodium/calcium channels of vertebrates vs. invertebrates should be examined. We do not recall this being an issue in Israel.

Could you elaborate on the cation exchange process for deactivating the toxin?
If any cation that could be complexed with the toxin could be removed, it should make a difference. Is it the P. parvum that is complexing with various cations? What are the implications of pH on the relationship? Many combinations of this matrix should lead to greater contact with Israeli partners.
Bioassay variability must take the variability of chemical composition into account. More needs to be known about the chemistry of the water.

Edvardsen: P. parvum toxins appear to be easily broken down with light. Reducing salinity to prevent the growth of P. parvum cells could be one key.

Glass: In Texas, one of the keys to a kill is that the aquatic insects remain alive and well. They appear to be unaffected by a P. parvum bloom.

Audience Comment: With respect to reducing salinity, reducing it even a few parts per thousand requires a significant volume of freshwater. It sounds terrific as a lab approach but can be potentially very expensive in the U.S.

Shrimp/crabs were salvaged by putting them in cages. Why were the crustaceans unaffected?

What animals were used as controls for bioassays?
Gambusia. There were many fish in the channels between the ponds in Israel, and they are very easy to collect.

Although magnesium and calcium are involved in increased toxicity, and sodium is involved in decreased toxicity, might NaCl be an alternative for reducing toxicity?
Clays are often high in magnesium and calcium. Could there be binding with the clays because of these tendencies?

Edvardsen: In Norway, high salinities reduced toxicity, but growth of the organism was stopped at very low salinities.

Are fish kills caused by a toxin that is free in the water and accumulating through time, or are they caused by bursting cells? How much time would it take for the toxin to recur to a level that was lethal?
The dynamics of the toxin need to be studied and identified. At the beginning of the bloom, the fish can be exposed by ingesting the toxin. With time (1-2 days) and lysing of cells, more extracellular toxin appears (depending on a range of variables). When all of the toxin is intracellular, we are not clear on the risk factors for fish consuming the algae.
Exposure by ingestion needs additional study.
Gambusia were used as test fish. They are generally a surface fish, which explains why they survive longest. Fathead minnows tend to swim deeper and are a more rapid indicator of P. parvum toxicity. If you have deep reservoirs, be aware if the benthic fish are being affected. Identify how the toxin is circulating within the system. It is crucial to verify how fish are being exposed and what they are being exposed to. Multiple effects must be sorted through.

Karen A. Steidinger: How to Use the Past to Plan for the Future

How important is recurring funding?
Critical. Having to go to the Legislature year after year is difficult, time-consuming, and tends to erode credibility over a long period of time.

top of page