Warming waters means many marine species are on the move

Whoa there little fella where do you think your trying to hitch a ride off to? Actually, he’s not the only one on the move.  Elvira Poloczanska from CSIRO, and plethora of colleagues around the globe have been very busy bees over the past 3 years, assembling a database of a whopping 1,735 recorded changes in marine biological responses (distribution, phenology, community composition, abundance, demography, and calcification).  These changes come from a whole range of species from around the globe.  How far back data went varied, time span averaged at around 40 years (so back to the 1970s - I believe this is roughly around/just after Scuba diving started to become more main-stream).  So what did they find?  Well, out of all the changes, 81–83% of them were consistent with climate change.  Here’s two of the ‘headline’ changes that came out of this study…

Many (but not all) species are moving with the increasing sea surface temperature, and are moving towards the poles (where it is cooler). The big movers are shifting an average of 72 km a decade towards the poles.  Depending on location, fishermen may be quite pleased with the new fish coming into their waters.

Just like on land, many marine species have key times of year when they migrate and breed. These have started happening earlier….about four days earlier on average. Doesn't sound much, and the most extreme changes found in plankton and larval bony fish (11 days) doesn't sound like much either but it’s enough to cause potential problems.  For example, if you’re a fish whose kids love to eat plankton then on an evolutionary time scale your spawning may be timed to when plankton blooms are greatest.  After all, you don’t want all of your young’uns starving to death.  Suddenly the plankton blooms earlier…by the time you have spawned, it’s pretty much done and dusted.  Sure this happens from time to time, but the problem is if spawning timing is consistently missing the bloom.

This study does not suggest that all ocean life is doomed.  Some species may be able to adapt to the changing ‘ocean climate’, but when changes happen rapidly enough that evolutionary processes aren’t keeping up, that’s when the real problems start to seep in.  Impact will vary among species, and possibly across different populations of species.

And of course, some regions of the ocean are likely to experience greater impacts of climate change than others.  I’m thinking about south east Australia which has been experiencing sea surface temperature increases three times the global average…but more on that in a later post.  It’s also worth noting that some areas of the global ocean aren’t warming at all.  Just like species variation, regional variation is a very important consideration in these matters.

The database is only based on reported findings from peer-reviewed literature (that’s science papers that appear in scientific journals),  and so misses out on a whole heap of data held with individual groups, such as wildlife trusts, NGOs, and even avid wildlife recorders and just through TEK (traditional ecological knowledge).  Although sifting through this data would take an enormous amount of manpower (data would need to be verified as accurate as best as possible), I suspect the even more insights could be gained.  Regardless, the original message still stands….The ocean ecosystem is changing more rapidly than expected.

The original paper appears in the Journal ‘Nature Climate Change’.  In typical Nature style, you will need to be as subscriber or pay to access the paper, which can be found here http://dx.doi.org/10.1038/nclimate1958

I would also like to draw your attention to another paper released earlier this year by Dr Alistair Hobday of CSIRO, Australia which takes a look at how we should start looking at adaptation to the changing marine ecosystem.  Is work is available to read without payment

Image:  Credit Ryan Harvey/Flickr (CC BY-SA 2.0)