One of the most dangerous impacts of climate change for our oceans is the uptake of increased carbon dioxide emissions caused by human activities. An estimated 30-40% of CO2 produced by burning fossil fuels is absorbed by the oceans, seas and lakes which has helped to buffer the changes to our terrestrial environment. Unfortunately, this has huge consequences for marine habitat as when CO2 dissolves in seawater, it forms carbonic acid which creates increasingly more acidic oceans. The impacts of acidification are extremely varied from causing increased rapidity of shell dissolution in molluscs, to impacting coral reef recovery, however a new study published last week suggests there are further changes afoot.
We have all seen documentary footage of beautiful, colourful coral reefs, with fronds of soft corals drifting in the current and shoals of silvery fish; they appear peaceful and serene oasis of calm in a frantic ocean. However, appearances can be deceptive!
Coastal reefs are loud dynamic environments filled with sounds of crackling, snapping and even grunting creatures. These sounds are not just the by-product of the traffic in coral cities, but also vital for species communication and guiding juvenile fish in the plankton to their future homes. Whereas light and scent transmissions are quickly affected by water, sounds such as these are one of the more reliable directional cues in the seas.
The loudest invertebrate in the ocean is the snapping shrimp, Alpheus novaezelandiae, also one of the most common of the sound-producing reef inhabitants. Groups of shrimps snapping their claws can be heard as “choruses” from kilometres away, as each shrimp can produce sounds of up to 210 dB! This is through production of bubbles in the rapidly snapping claw that makes a loud clicking sound.
However, a team of researchers from the University of Adelaide have discovered that under increased ocean acidification conditions, the shrimp significantly reduce the frequency and volume of their snaps. The results suggested this was not due to any physical changes in the claw, but to behavioral differences in the shrimp themselves.
With so much at stake, perhaps this latest piece of evidence can be used to strengthen our resolve to try reduce our carbon footprint wherever possible; from using public transport and turning off light switches to only filling the kettle as much as needed. I know I am guilty of wasting energy (and thereby burning excess carbon) on a regular basis, and the terrible predictions of this study will now ensure I remember to do my best.
I hope the day never arrives where silence fills our oceans, without a snap to be heard…