The study shows that harmful and ubiquitous Karenia brevis algae, which cause red tide blooms across the Gulf of Mexico, become two to seven times more toxic when levels of phosphorus, a major algal nutrient found in fertilizers and human waste, are low. Like wearing a suit of armor, producing highly toxic cells allows the algae to defend themselves against opportunistic waterborne grazers like zooplankton.
Red tide blooms in the Gulf are linked to fish kills and other ecological and economic damage in the region, and are also linked to respiratory ailments in humans. These blooms occur annually in the Gulf, but it’s hard to predict where or when they’ll occur or how long they’ll last.
Drs. Rance Hardison and Damian Shea, co-authors on a paper appearing online in the journal PLOS ONE, say that the findings could help coastal managers make better predictions about the harmful effects of red tide blooms.
“Public-health managers can test phosphorous levels in waters across various Gulf locations,” Hardison said, “and know that low levels could indicate highly toxic red tide blooms. Then they can close nearby shellfish beds or take other measures to keep sea life – and humans – safe.”
The researchers tested five different K. brevis species from varied geographic locations and limited some samples’ growth by withholding phosphorus while allowing others to enjoy a full diet of phosphorus. Depending on the species, algal cells with limited access to phosphorus had 2.3 to 7.3 times more toxin than algal cells that were filled up with phosphorous.
“At the end of a red tide bloom, when the nutrients are used up, K. brevis cells produce a burst of toxicity. Now we understand the biological mechanism behind some of the varied toxic levels seen in Gulf algal cells,” Shea, an NC State professor of biology and environmental toxicology, said.
The irony of the inverse relationship between phosphorous and algal toxicity is not lost on the researchers. In a modern-day catch-22, excess nutrients like phosphorus and nitrogen play key roles in fueling algal growth and harmful algal bloom development. As bloom density increases, cells use up the available nutrients such as phosphorous. This slows the growth of K. brevis cells causing them to become more toxic. Previous research conducted by Hardison, a NOAA oceanographer who received his Ph.D. from NC State, showed similar effects when nitrogen was the limiting nutrient.
“We believe the findings will be useful to help model future toxic algal blooms and how harmful they’ll be,” Hardison said.
- kulikowski -
Note to editors: An abstract of the paper follows.
Increased toxicity of Karenia brevis during phosphate limited growth: ecological and evolutionary implications
Authors: D. Ransom Hardison, William Sunda, R. Wayne Litaker, National Oceanic and Atmospheric Administration; Damian Shea, North Carolina State University
Published: March 12, 2013, online in PLOS ONE
Abstract: Karenia brevis is the dominant toxic red tide algal species in the Gulf of Mexico. It produces potent neurotoxins (brevetoxins [PbTxs]), which negatively impact human and animal health, local economies, and ecosystem function. Field measurements have shown that cellular brevetoxin contents vary from 1? 68 pg/cell but the source of this variability is uncertain. Increases in cellular toxicity caused by nutrient-limitation and inter-strain differences have been observed in many algal species. This study examined the effect of P-limitation of growth rate on cellular toxin concentrations in five Karenia brevis strains from different geographic locations.
Phosphorous was selected because of evidence for regional P-limitation of algal growth in the Gulf of Mexico. Depending on the isolate, P-limited cells had 2.3- to 7.3-fold higher PbTx per cell than P-replete cells. The percent of cellular carbon associated with brevetoxins (%C-PbTx) was ~ 0.7 to 2.1% in P-replete cells, but increased to 1.6? 5% under P-limitation. Because PbTxs are potent anti-grazing compounds, this increased investment in PbTxs should enhance cellular survival during periods of nutrient-limited growth. The %C-PbTx was inversely related to the specific growth rate in both the nutrient-replete and P-limited cultures of all strains. This inverse relationship is consistent with an evolutionary tradeoff between carbon investment in PbTxs and other grazing defenses, and C investment in growth and reproduction. In aquatic environments where nutrient supply and grazing pressure often vary on different temporal and spatial scales, this tradeoff would be selectively advantageous as it would result in increased net population growth rates. The variation in PbTx/cell values observed in this study can account for the range of values observed in the field, including the highest values, which are not observed under N-limitation. These results suggest P-limitation is an important factor regulating cellular toxicity and adverse impacts during at least some K. brevis blooms.
Dr. Rance Hardison | Source: Newswise
Further information: www.noaa.gov
More articles from Ecology, The Environment and Conservation:
Atlantic Research Expedition Uncovers Vast Methane-Based Ecosystem
24.05.2013 | University of North Carolina Wilmington
Reforestation study shows trade-offs between water, carbon and timber
24.05.2013 | Arizona State University
This morning at 05:45 CEST, the earth trembled beneath the Okhotsk Sea in the Pacific Northwest. The quake, with a magnitude of 8.2, took place at an exceptional depth of 605 kilometers.
Because of the great depth of the earthquake a tsunami is not expected and there should also be no major damage due to shaking.
Professor Frederik Tilmann of the GFZ German Research Centre for Geosciences: "The epicenter is exceptionally deep, far below the earth's crust in the mantle. Such strong ...
The Ring Nebula's distinctive shape makes it a popular illustration for astronomy books. But new observations by NASA's Hubble Space Telescope of the glowing gas shroud around an old, dying, sun-like star reveal a new twist.
"The nebula is not like a bagel, but rather, it's like a jelly doughnut, because it's filled with material in the middle," said C. Robert O'Dell of Vanderbilt University in Nashville, Tenn.
He leads a research team that used Hubble and several ground-based telescopes to obtain the best view yet of ...
New indicator molecules visualise the activation of auto-aggressive T cells in the body as never before
Biological processes are generally based on events at the molecular and cellular level. To understand what happens in the course of infections, diseases or normal bodily functions, scientists would need to examine individual cells and their activity directly in the tissue.
The development of new microscopes and fluorescent dyes in ...
A fried breakfast food popular in Spain provided the inspiration for the development of doughnut-shaped droplets that may provide scientists with a new approach for studying fundamental issues in physics, mathematics and materials.
The doughnut-shaped droplets, a shape known as toroidal, are formed from two dissimilar liquids using a simple rotating stage and an injection needle. About a millimeter in overall size, the droplets are produced individually, their shapes maintained by a surrounding springy material made of polymers.
Droplets in this toroidal shape made ...
Frauhofer FEP will present a novel roll-to-roll manufacturing process for high-barriers and functional films for flexible displays at the SID DisplayWeek 2013 in Vancouver – the International showcase for the Display Industry.
Displays that are flexible and paper thin at the same time?! What might still seem like science fiction will be a major topic at the SID Display Week 2013 that currently takes place in Vancouver in Canada.
High manufacturing cost and a short lifetime are still a major obstacle on ...
24.05.2013 | Life Sciences
24.05.2013 | Ecology, The Environment and Conservation
24.05.2013 | Physics and Astronomy
17.05.2013 | Event News
15.05.2013 | Event News
08.05.2013 | Event News