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Figure 1. Microscopic image of the Karenia brevis. Image from: http://mote.org/clientuploads/Documents/MPI/Final_MPI_RedTide_no_embargo_bar.pdf
Introduction
Introduction
Karenia brevis is a type of single-celled organism called a dinoflagellate. The accumulation of this organism caused what's known as Red Tide, which are mainly harmless though some, including K. brevis, produce neurotoxins that can cause respiratory problems in humans and attack the central nervous systems of fish and other wildlife. (Thompson Earth Systems Institute, 2019)
The red tide dinoflagellate Karenia brevis is noted for causing mass mortalities of marine organisms in the Gulf of Mexico. (G. Hansen & Moestrup, 2005)
This organism produces potent neurotoxins (brevetoxins) that are harmful to both fish and mammals, and can have significant human health impacts.
Red tide blooms in Florida begin 10-40 miles offshore in the bottom waters of the Gulf of Mexico, where K. brevis is almost always present at low and harmless concentrations. K. brevis cells are brought to the surface by upwelling*. (Thompson Earth Systems Institute, 2019)
Primary literature examines the effects of light, temperature and salinity* on the growth rate of K. brevis from the western Gulf of Mexico. Growth rates of K. brevis were determined under various combinations of irradiance (G. Hansen & Moestrup, 2005)
salinity*: concentration of salt in water
upwelling*: a process in which deep, cold and nutrient-rich water rises to the surface
Background
Background
Taxonomy
Taxonomy
Kingdom: Protista (NCBI Taxonomy, 2020)
Phylum: Dinophyta
Class: Dinophycease
Order: Gonyaulacales
Family: unknown
Genus: Prorocentrum
Species: Karenia brevis
The objective of this study is to define the range of environmental factors that provide optimal growth for a Texas clone of K. brevis under various environmental conditions (light, salinity, and temperature). (G. Hansen & Moestrup, 2005)
Annual kills caused by K. brevis red tides involve hundreds of thousands of fish and other animal species. However, data describing declines in fisheries, and the evident rebound of selected fish species every year have provided no indication that frequent red tides could lead to an unsustainable reduction in fish populations or even threaten the long-term survival of local populations of imperiled species. (J.H. Landsberg, 2008)
Habitat and Eating:
Habitat and Eating:
This organism can eat: (Thompson Earth Systems Institute, 2019)
This organism can eat: (Thompson Earth Systems Institute, 2019)
Zooplankton and microplankton waste
Grazing food waste
Benthic flux, or the exchange of nutrients from the sediment to the water.
Red tides can have human health impacts. Exposure to brevetoxins occur through inhalation or ingestion. K. brevis cells are weak, so wave action can break open the cells, releasing the brevetoxins as an aerosol. People in coastal areas can experience varying degrees of eye, nose, and throat irritation. (Thompson Earth Systems Institute, 2019)
Habitat:
Habitat:
Commonly found in water of Gulf of Mexico. (J.H. Landsberg, 2008)
Data Analysis:
Data Analysis:
Study was done to find optimal growth conditions of Karenia brevis so scientists can determine if the waters of the Gulf of Mexico have similar characteristics (G. Hansen & Moestrup, 2005)
Salinity was measured with a Fisher Scientific refractometer (20, 30, 35, 40, 45)
Illumination was provided by overhead fluorescent “warm white” 40 W lights for all experiments.
Walk-in incubator maintained at the appropriate temperature for each experiment (15, 20, 25, 30, or 35 °C).
Exponential growth rates of K. brevis increased with irradiance however the cultures at salinity of 45 maintained at 15, and 30 °C, had no growth. Negative growth rates are due to the inability of K. brevis to grow at high salinity levels except at the highest light regime.
Fig. 1. (A–D) Growth rate of Karenia brevis Texas clone SP3 at different temperatures and irradiance levels. (A) Irradiance-growth curves 15 °C. (B) Irradiance-growth curves 20 °C. (C) Irradiance-growth curves 25 °C. (D) Irradiance-growth curves 30 °C. (G. Hansen & Moestrup, 2005)
Fig. 1. (A–D) Growth rate of Karenia brevis Texas clone SP3 at different temperatures and irradiance levels. (A) Irradiance-growth curves 15 °C. (B) Irradiance-growth curves 20 °C. (C) Irradiance-growth curves 25 °C. (D) Irradiance-growth curves 30 °C. (G. Hansen & Moestrup, 2005)
Fig. 2. (A–D) Light compensation-growth rates. (A) Light compensation-growth rates 15 °C. (B) Light compensation-growth rates 20 °C. (C) Light compensation-growth rates 25 °C. (D) Light compensation-growth rates 30 °C.
Results from this study indicate only a slightly narrower range of salinity tolerance (25–40) than those reported from previous studies. K. brevis clone SP3 could not be acclimated to salinity levels above 45 or below 25
Suboptimal temperature and light conditions resulted in an inability to tolerate the highest salinity. Results indicate that, under normal environmental conditions (20–25 °C), a light intensity of approximately 67 μmol m−2 s−1 could be the saturation point for the Texas clone.
The temperature tolerance of the Texas clone (SP3) appeared to generally resemble that for the Florida clones, with only minor differences shown at the temperature extremes. Growth rates in this study were significantly lower at 15 °C than other temperatures indicating that low temperatures probably restrict its growth in Texas coastal waters in late fall and winter.
Texas K. brevis clone SP3 varied in growth rate when cultured under different light, salinity, and temperature criteria. The Texas clone (SP3) had a similar light saturation point compared to that of the Florida isolate (67 μmol m−2 s−1 versus 65 μmol m−2 s−1), and similar light compensation point (20–30 μmol m−2 s−11) to most previous studies.
Conclusion:
Conclusion:
The temperature tolerance of the Texas clone (SP3) appeared to resemble that for the Florida clones, with only minor differences shown at the temperature extremes. Growth rates in this study were significantly lower at 15 °C than other temperatures indicating that low temperatures probably restrict its growth in Texas coastal waters in late fall and winter. (G. Hansen & Moestrup, 2005)
Statement: Karenia Brevis have a slight narrower range of salinity than past studies have shown.
This study helps determine growth conditions for Karenia brevis which can help stop the toxins from killing marine organisms.
Further, this study can help alleviate respiratory problems in humans.
References:
References:
Primary Article:
G. Hansen, Moestrup, The effect of environmental factors on the growth rate of Karenia brevis
(Davis) G. Hansen and Moestrup, Science Direct. (n.d.).
https://www.sciencedirect.com/science/article/pii/S1568988305000788 (accessed
September 12, 2023).
Secondary Article:
J.H. Landsberg a, a, b, AbstractAs recently as a decade ago,
Backer, L. C., Fleming, L. E., Ishida, H., Leverone, J. R., Magaña, H. A., McFarren, E.
F., Naar, J. P., Plakas, S. M., Poli, M. A., Steidinger, K. A., Trainer, V. L., Walsh, C. J.,
Wang, Z., Abbott, B. C., Baden, D. G., … Kreuder, C. (2008a, December 9). Karenia
brevis red tides, brevetoxins in the food web, and impacts on natural resources: Decadal
Advancements. Harmful Algae.
https://www.sciencedirect.com/science/article/pii/S1568988308001571
Mote Marine Laboratory & Aquarium. (n.d.). https://mote.org/clientuploads/Documents/MPI/Final_MPI_RedTide_no_embargo_bar.pdf
Schoch CL, et al. NCBI Taxonomy: a comprehensive update on curation, resources and tools. Database (Oxford). 2020: baaa062.
Red Tide: Karenia Brevis. Thompson Earth Systems Institute. (2019, August 19). https://www.floridamuseum.ufl.edu/earth-systems/blog/red-tide-karenia-brevis/
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