Variable Light Illuminates The Distribution Of Picophytoplankton

Tiny photosynthetic plankton less than a millionth of a millimeter in diameter numerically dominate marine phytoplankton। Their photosynthesis uses light to drive carbon dioxide uptake, fueling the marine food web over vast areas of the oceans. A new study by post-doctoral researcher Dr Christophe Six and a team of scientists from MountAllison University, Sackville, New Brunswick, Canada, illuminates how the environment regulates the distributions of these ecologically important species.

Dr Doug Campbell, Canadian Research Chair in Environmental Processes and co-author explains, "Phytoplankton are entrained in the water column and are thus subject to rapid changes in light as they mix through the upper layer of the ocean."
Dr Christophe Six adds, "Phytoplankton need light for photosynthesis and survival, but surprisingly this light also inactivates a key component of the photosynthetic apparatus, photosystem II. This Photoinactivation of photosystem II decreases photosynthesis and can even kill cells, unless they can counteract the damage through repair, which requires nutrients."
"We found the picophytoplankton species isolated from different regions of the ocean have different abilities for this repair, and therefore have different abilities to tolerate increases in light. Their repair capacities are consistent with the different light and nutrient regimes in their local environments; species from deep ocean regions with stable light and low nutrients have very limited repair capacity, but species from coastal regions with more variable light and higher nutrients are more able to cope with variable light through rapid repair."
This result indicates that picophytoplankton species' tolerance of exposures to high light can help to explain how these organisms are distributed throughout the ocean. The group measures the rates of photoinactivation and the rates of the counteracting repair in a wide variety of phytoplankton species, and next plans to contribute to ocean models to predict phytoplankton carbon cycling in response to future climate change.
Citation: Six C, Finkel ZV, Irwin AJ, Campbell DA (2007) Light Variability Illuminates Niche-Partitioning among Marine Picocyanobacteria. PLoS One 2(12): e1341. doi:10.1371/journal.pone.0001341. http://www.plosone.org/doi/pone.0001341
Adapted from materials provided by Public Library of Science.

Firefly fish for pollution monitoring

Schools of glowing fish could become a tool for monitoring water quality. The US government's National Institute of Environmental Health Services (NIEHS) has been funding research into fish that glow like a firefly when exposed to polluted water.Fireflies light up when an enzyme in their stomach called luciferase oxidises luciferin. The NIEHS hopes to insert luciferase-producing genes from fireflies into the eggs of zebrafish. Other genes would then be injected into the zebrafish making them sensitive to a particular pollutant. This could make the fish generate luciferase in the presence of mercury, for example.The genetically modified fish could then be dangled in a cage into water at risk of pollution. After half an hour they could be removed and dunked into a solution containing luciferin. If they start to glow, it means the water is polluted. The brightness of their glow could even reveal just how bad the pollution is. And the fish should survive the process for re-use later.

An US patent was claimed for this work and the abstract is as follows

The present invention provides methods and systems that uses transgenic zebrafish with an easily assessable reporter gene under the control of pollutant-inducible DNA response elements. Transgenic zebrafish, carrying pollution-inducible response elements, are placed in the water to be tested, and the contaminants become bioconcentrated (generally 1,000- to 40,000-fold, relative to the water) in the tissues of the fish thereby activating specific response elements, which up-regulate the LUC reporter gene. Fish are then removed from the test water and placed immediately in a luminometer cuvette and incubated with luciferin. Luciferin is rapidly taken up into the tissues of the fish, oxidized by luciferase, and light is produced. The luminescence is proportional to the environmental concentration of the pollutant (to which the fish had been exposed), which drives the expression of the LUC gene by means of the various DNA motifs. The luminescence is quantitated in the luminometer. In each response element-containing construct, a specific class of polluting chemicals, allowing for differential identification of pollutants in a complex mixture activates the expression of the LUC gene. This assay does not require killing the fish and allows for repeated analysis of the same site with the same fish. The sensitivity of the system can be manipulated by varying the sequence of the response element.

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