Stories tagged red tides


One way to determine the health of an estuary is to test some of its “vital signs”. Important vital signs in rivers and estuaries include things that affect the quality of the water for the health of the various living organisms that call that water home. If there are toxic materials, or even too much of a good thing, like oxygen, organism throughout the food chain can suffer.

One such vital sign can be the development in rivers and estuaries of “red tides”. This term is used to describe large “blooms” of phytoplankton in coastal waters. Phytoplankton are tiny floating plants. They obtain energy through the process of photosynthesis and must therefore live in the well-lit surface layer, where they account for half the photosynthetic activity on our planet. “Red tides” don’t have to be either red or associated with tides, but they concern scientists, because they can produce toxins that can overwhelm other organisms in the water.

Plankton bloom: Plankton bloom flows under Astoria bridge.
Plankton bloom: Plankton bloom flows under Astoria bridge.Courtesy Alex Derr, CMOP

CMOP is studying a plankton bloom that is dominated by one type of organism called Myrionecta rubra. The organism is technically a eukaryotic protist, a single-celled organism that floats in the water column. Under certain environmental conditions, the cells grow exponentially to millions of cells per liter of water within a few days. The cells are red and the shear numbers of them reflect the sun’s light and enhance their red color in the water.

Myrionecta rubra
Myrionecta rubraCourtesy CMOP

CMOP researchers Herfort and Peterson traveled to Astoria to collect samples of the plankton bloom. They gathered samples in both the dense red water and in clear patches of water. These samples helped them compare the conditions in the water and the influences the red tide organism might have on its environment.
CMOP scientists have already analyzed several samples collected during previous year’s blooms. Herfort and Zuber use molecular biology techniques to look at the genetic fingerprints of these organisms and others associated with the bloom. This molecular work is carried out in collaboration with Lee Ann McCue Ph.D., a scientist from Pacific Northwest National Laboratory, who performs genetic sequence analysis. Herfort said, “Our data will improve our understanding of the ecological impact of Myrionecta rubra bloom on the Columbia River estuary.”
Red tide, close-up
Red tide, close-upCourtesy CMOP

Eventually whatever caused the Myrionecta rubra to grow rapidly will change and they will no longer have a source of nutrients. Peterson stated, “When they die, they decompose and bacteria can feed on the decomposed material. This growth of bacteria then draws down the oxygen in the water around them while they are respiring”. So while the bloom itself is not toxic in this case, here’s where another vital sign comes in: the bacteria’s respiration may have a harmful effect to other species, by depleting oxygen available to them. (Due to a great deal of water flow and flushing in the Columbia River, this is currently not a danger.)

What's next?

Unanswered questions that CMOP researchers are exploring include:

  • Is the Myrionecta rubra an important “vital sign” for the estuary?
  • What controls the timing and behavior of the bloom?

The CMOP research team wants to start answering these and other questions by using a combination of physiological studies, molecular work, and observations and simulations from their end-to-end coastal margin observatory (SATURN). They hope this will provide clues about the factors that lead to plankton blooms, and ultimately improve the ability to predict these events.