DMSP: a bioindicator for corals?

Dimethylsulfoniopropionate (DMSP) is an organic sulphur compound which is produced by many types of phytoplankton. It plays various roles for phytoplankton and in the marine microbial world e.g.: anti predation, osmolytes and cryoprotectants.  Until recently, it was thought that phytoplankton were the only producers of this molecule, however recently it was discovered that the gastrodermis of corals symbiotic zooxanthallae contains DMSP lyase, and their symbiotic dinoflagellates contain high levels of DMSP. Researches in the past have found that stressed conditions causes an increase of reduced oxygen species accompanied by increased DMSP.  If DMSP production in corals changes in stressed conditions, it could become a bioindicator, which would be very useful with the increase of temperatures and severe weather patterns.

The study was carried out at several different stations in the Great Barrier Reef, one at the Heron Island Research Station’s aquarium complex though out a succession of winters (September) and summers (February) from 2001 to 2003.  Another base was at Nelly Bay, on the eastern coast of Magnetic island. This fringing reef has many environmental impacts: increased nutrients, suspended sediments due to dredging, nutrient run-off, sewage discharge and increased bleaching events. The studies on this fringing reef were conducted 5 months after the severe bleaching event in the summer of 1994. This site was used to compare to other reefs as “stressed”.

This study measured two different factors with Acropora intermedia, : DMSP  production between 2001-2003, and the effects of raising the seawater temperature by +2 °C measured by production DMSP and levels of cellular DMSP and  Chlorophyll a(Chl. a). They then compared this to the Magnetic Island reef (consisting of Pocillopera damicornis ) off the coast of Magnetic Island in the central Great Barrier Reef,  to study the differences between stressed an non stressed  corals. 

Acropora intermedia collected from Heron Island showed distinct seasonal cycling of DMSP with increased production during the summer, and lower in the winter. This was distinct each year despite the severe bleaching event of 2002.  The year with the largest production of DMSP was the summer months with the high sea surface temperature (SST), solar radiation and rainfall.  By increasing the water temperatures by +2 °C in the summer and winter, A. intermedia’s DMSP production increased by 45%, compared to the winter 2001 and summer  2002.  The cellular DMSP increased in the winter of 2002 and summer 2003, almost half a year after coral bleaching. The authors suggested that the increase was due to higher temperatures and high rainfall. Cellular chlorophyll a concentrations decreased from 2001-2001 (bleaching) but then increased the next summer as the coral recovered.

When comparing the Heron Bay site to the Magnetic Island site, they found that there was a highly significant correlation between cellular DMSP and chlorophyll a. This could show an adaptive response to increased numbers of reduced oxygen species which had been produced during the bleaching event, and also may have helped the corals recovery. The Increased cellular DMSP could also have been caused by changes in the symbiont community. Measurements have been made on Acropora coral from many different locations from across the Great Barrier Reef which leads to the suggestion that changes in the cellular/tissue concentration is a sensitive indicator to stress

This study suggests that DMSP is a bioindicator for all types of stress and does put forward some evidence for this theory, however there was little evidence that any of the stress that caused the DMSP to be released was manmade, it may have been mainly temperature. If this is the case, although it is interesting, how could we use this indicator? If it was affected by the sediments/ nutrient run-off, then we could use the indicator to reduce the anthropogenic pollutants in the area but we cannot change temperature. On the other hand it may be interesting to see if this effects when pathogens attack the corals, as they can use chemotaxis to follow DMSP to stressed corals which are easier to attack. 

Jones, Graham B., et al. "The effect of coral bleaching on the cellular concentration of dimethylsulphoniopropionate in reef corals." Journal of Experimental Marine Biology and Ecology 460 (2014): 19-31.

http://www.sciencedirect.com/science/article/pii/S002209811400166X