For many the worlds oceans have little consequence on their daily lives. They are deemed beautiful but a resource that can be fully taken advantage of. Indeed we as the humans also have the tendancy of treating the oceans with little respect, polluting it with sewage, chemicals and rubbish.
However my motivation here, is not to complain and blame others but to simply describe some of the issues and science I come across in my daily life as an environmental scientist. After reading this you may have some insight into why I consider my career choice so fasinating yet equally depressing.
Sea Surface Temperature in the Polar regions
The Intergovernmental Panel for Climate Change (IPCC) projects anthropogenic induced climate change will increase sea surface temperature (SST) in the polar climate zone, particularly during winter and spring. Extensive microbial communities flourish within the polar ice covers, contributing significantly to the polar ocean carbon budget (Thomas & Dieckmann, 2002). Elevated SST during winter and spring could lead to a higher proportion of the total photosynthesised organic matter being metabolised and recycled by microbial loop organisms (bacteria) (Kirchman et al. 2005, Hoppe et al. 2008).
Rivkin et al., (1999) identified that microzooplankton (hereafter MICZ) obtain most of their nutrition from picoplankton (including bacteria). Thus the bacterial standing crop can be suppressed by MICZ grazing, resulting in the microbial loop experiencing a top-down control (Vaque and Pace, 1992; Ooms-Wilms et al., 1995).
Temporal changes in the occurrences of maximal bacterial production and grazing rates of MICZ may shift the predation rates of MICZ by higher trophic level species, having possible implications for fisheries and commercial enterprises.
Those who keep track of the news and modern issues, should be fully aware of the science behind climate change. However many may be unaware that there is another hidden danger to our carbon emissions.
The world’s oceans are critically important as a carbon sink; as anthropogenic carbon emissions rise, the oceans take up an increasing amount of CO2. When dissolved in the surface ocean, this additional CO2 causes re-equilibration of the seawater carbonate system, increasing the concentrations of aqueous CO2 (usually quantified by its partial pressure pCO2) and bicarbonate ion, HCO3− , while decreasing that of the carbonate ion, CO32−. These changes in the distribution of dissolved inorganic carbon (DIC) result in an increase in concentration of the hydrogen ion, H+, leading to a decrease in pH, a process known as ocean acidification (Shi et al., 2009). The impacts of this on phytoplankton are many and varied (see Doney, 2006), including an increase in primary production in the ocean caused by elevated pCO2 (Tortell et al., 2008).
There has already been observed lowered pH, and many diatom species are already reacting to these changes, either their shells start dissolving or changes in dominant species leading to higher extinction rates. As the primary producers of the oceans this has very bad consqeuences for fish stocks. Millions of people depend on fisheries for food and to make a living. Declines in fish stocks as a result could indirectly cause civil wars and starvation, not to mention the impacts on marine mammals and other predators.
Ah the life of an environmental scientist, I learn and research these amazingly complex systems only to see in front of my eyes their destruction. This is a small snippet of what I encounter every day, never mind deforestation, biodiversity loss/ extinctions, overfishing, climate change, habitat loss to name only a few. Look forward to more interesting but equally depressing tales soon.
References and Further Reading
Doney, S. C., 2006, Oceanography: Plankton in a warmer world, Nature, 444, 695–696.
Kirchman DL, Malmstrom RR, Cottrell NT (2005) Control of bacterial growth by temperature and organic matter in the Western Arctic. Deep-Sea Res II 52:3386–3395
Hoppe, H-G., Breithaupt, P., Walther, K., Koppe, R., Bleck, S., Sommer, U. and Jürgens, K. (2008) Climate warming in winter affects the coupling between phytoplankton and bacteria during the spring bloom: a mesocosm study, Aqu. Microb. Ecol., 51:105-115
Ooms-Wilms,A.L., Postema,G. and Gulati,R.D. (1995) Evaluation of bacterivory of Rotifera based on measurements of in situ ingestion of fluorescent particles, including some comparisons with Cladocera. J. Plankton Res., 17:1057–1077.
Rivkin, R.B., Putland, J.N., Anderson, M.R., Deibel, D., (1999) Microzooplankton bacterivory and herbivory in the NE subarctic Pacific, Deep-Sea Res. II, 46:2579-2618
Shi, D., Xu, Y. and Morel, F.M.M., 2009, Effects of the pH/pCO2 control method on medium chemistry and phytoplankton growth, Biogeosciences, Vol. 6, pgs 1199–1207.
Thomas, D. N., and Dieckmann, G. S. (2002) Antarctic sea ice-a habitat for extremophiles, Science, 295:641–644
Tortell, P. D., Payne, C. D., Li, Y. Y., Trimborn, S., Rost, B., Smith,W. O., Riesselman, C., Dunbar, R. B., Sedwick, P., and DiTullio,G. R., 2008,CO2 sensitivity of Southern Ocean phytoplankton, Geophysical Research Letters, 35, L04605, doi:10.1029/2007GL032583.
Vaque,D. and Pace,M.L. (1992) Grazing on bacteria by flagellates and cladocerans in lakes of contrasting food-web structure. J. Plankton Res., 14: 307–321.