To follow the trend of lands in trouble, to the wetlands divide, now I’ll let go of the lands completely and take an ever too brief look at the state of our ocean. I feel that I will unable to give this environment enough justice in this format, however for the sake of consistency, I’ll try my best. Looking at the impacts we’ve had on our oceans, it’s like saying, “pick a card; any card!” Our attitude towards this alien environment has been at best, appalling. Over the previous two centuries we have proven ourselves to be increasingly efficient at pulling every living thing out of the oceans – from anchovies to whales and while big boats are bringing ever bigger catches in, other big boats are taking our effluent and refuse out and dumping it out of sight. As soon as the catch starts to fall off, the boats move somewhere else.
respect it’s similar to poor farming techniques in Australia that continues to move it’s stock across the land, leaving a simplified and chemically poisoned scape in its wake. The old time stereotypical dirty sailor, going from port to port should at least continue to apply to their ships and the biological matter that is transferred in their ballast water.
And while all this plundering and polluting of the oceans occurred, a silent foe – the child of our emissions – has slipped onto the scene to make the atmosphere of this underwater world even less pleasant for the remaining locals.
Taking the base out of a limestone home
Unlike the uncertainties related to climate change predictions, the result of CO2 concentration changes in water is predictable (Doney et al. 2009). As previously stated, around a third of the CO2 emissions since the industrial revolution have be absorbed into the ocean were it interacts with water molecules to produce carbonic acid, H2CO3 (Doney et al. 2009). Pre-industrial ocean pH was 8.21, which has since dropped to currently 8.10 (Doney et al. 2009). As the pH decreases, the amount of carbonate ion available within surface waters (the most active region) also decreases, which is important component for species that excrete calcium carbonate shells (Fabry et al. 2008). Thus far, carbonate depletion has been roughly 30 μmol kg−1 seawater (Hoegh-Guldberg et al. 2007).
Although it has been demonstrated that coral polyps may be able to persist in lower pH oceans, where they are unable to construct coral, fitness is decreased due to the absence of this protective cover (Fine and Tchernov, 2007) and/or the extra energy invested in calcification (Hoegh-Guldberg et al. 2007), and with the bed of calcium carbonate on which new coral is formed close to the surface at increased risk of erosion, it is unlikely that polyps will be able to migrate to higher latitude under a changing climate (Doney et al. 2009) (see part 5 on distribution) or be able to build structures higher as sea levels increase.
Calcification is prolific among many phyla. Many of these species are important food sources (ie. plankton, coral and algae), provide nursery environments for other species (ie. algae and coral), are important for nitrogen fixation in oceans (ie. cyanobacteria) and protection for storm surges (ie. coral), (see Doney et al. 2009 and Hoegh-Guldberg et al. 2007). As fitness of these groups diminish with decreasing pH of oceans, there are wide range of biodiversity and socio-economic ramifications that will occur (Hoegh-Guldberg et al. 2007).
To put it another way; as carbonate ions become less available, these species will have to work harder to product protective shells – either spending more energy to do so or on other methods to protect themselves. Less will be successful, thus providing less homes and food for other species – including economically valuable fish species. These in turn provide less food for predatory species (including us). With the likelihood of increased storm events, corals will be less able to provide coast protection from surges. Many coastal molluscs are keystone species which too will have reduced fitness, with detrimental ramifications on the local ecology. In every way, ocean acidification will effect the ecology of our oceans.
The current concentration of CO2 in the atmosphere is higher than that seen in over 740,000 years, if not much longer (Hoegh-Guldberg et al. 2007), with the rate of change accelerating (Raupach et al. 2007). Although the ability to adapt to these changes are not well known (see Doney et al. 2009 and Hoegh-Guldberg et al. 2007), certainly the rate of change over the coming centuries, coupled with many anthropogenic impacts discussed at the beginning of this piece would suggest that without better management, we are likely to witness degradation of the ecology and ever increasing extinction rates in all oceans.