Responses of Marine Benthic Microalgae to Declining pH Values
Johnson, V.R., Brownlee, C., Rickaby, R.E.M., Graziano, M., Milazzo, M. and Hall-Spencer, J.M. 2013. Responses of marine benthic microalgae to elevated CO2. Marine Biology 160: 1813-1824.
To further explore the potentialities of this situation, Johnson et al. compared periphyton assemblages on artificial substrata installed along a coastal CO2 gradient - which ranged from a median value of 419 to 592 to 1,611 ppm - at a shallow-water cold-vent system off the island of Vulcano, NE Sicily, with the aim of (1) testing the hypothesis that periphyton assemblages respond to CO2 gradients and (2) characterizing any changes in diatom and cyanobacteria populations to better understand the ecological effects of real-world ocean acidification.
In doing so, the six scientists report that periphyton communities were indeed "altered significantly as CO2 concentrations increased," and that "CO2 enrichment caused significant increases in chlorophyll a concentrations and in diatom abundance." Furthermore, "by using chl a as an index of the photosynthetic standing crop (Underwood, 1984)," they indicate that "periphyton biomass was found to increase substantially (fivefold) at the CO2-enriched stations," indicative of the fact that "elevations in CO2 stimulate primary productivity in these benthic assemblages."
Johnson et al. conclude that their findings are "likely to have wide-ranging consequences from local-scale influences on the structure of overlying benthic communities to effects on food web structure and larger-scale biogeochemical cycles." And all of these ecosystem-scale effects appear to be positive.
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