From classical to jazz: the rhythms of ocean life are starting to change
Migaloo, Queensland’s famous albino humpback whale, will be heading off on his spring migration early this year.
He’s not alone in this. Compared with the middle of last century, any creature in the ocean that has a backbone could now be starting its spring migration up to five and a half days earlier.
That is just one of many findings in a review paper published in Science today.
Professor Elvira Poloczanska, of CSIRO Oceans and Atmosphere, was part of an international research team that compiled the findings of over a hundred research articles on marine vertebrates from across the globe.
“We’ve tried to take the big picture view of how climate change is or might be affecting marine vertebrates – so that’s fish, mammals like whales and dolphins, sea birds and sea turtles.”
The planet’s orchestra is out of sync
Some of the most important findings lay in the timing of regular biological occurrences, or ‘phenology’.
“When birds lay their eggs, when whales migrate to their feeding grounds or their breeding grounds, when flowers bloom, when trees burst into leaf every year—looking at the timing of that, that’s phenology,” says Professor Poloczanska.
Professor Poloczanska likens it to an orchestra: “You could think about it as the different sections of the orchestra all of a sudden being out of step—the horn section coming in too early, the violins not playing when they’re supposed to.”
By collating research that included a minimum timespan of two decades worth of data, the team found that marine vertebrates were embarking on annual spring events, like migration or spawning, an average of 4.4 days earlier than the mid 20th Century.
Cues that triggered the initiation of those events were different across species, and included temperature, food abundance and daylight length – which can change if a population moves toward the poles.
Being ahead of schedule is not always good
So, is it really a problem that events are running a little ahead of schedule?
The situation is complicated when you are talking about entire interdependent populations of species that can range over hundreds of thousands of kilometres.
“The issue is that different species are shifting phenologies at different rates,” explains Professor Poloczanska.
“For some species, things are happening a lot earlier and for others, not so much. That has implications for the food web. For example, if seabirds are breeding earlier, is the food source there to feed their chicks?”
Like the awkward high-five, or the cheek-kiss that inadvertently hits the lips, some species that are supposed to dovetail are not.
Penguin species are playing tug of war with breeding times, some delaying, some advancing, depending on their food source.
Pelagic fish species, such as tuna, are peaking in number earlier in the year, while many of their prey species – fish that live near reef nutrient upwells – are starting to peak later.
Sea turtle laying time was associated with warmer sea temperatures, but was hard to link with climate, as they do not breed often enough to rule out other factors. However, turtle hatchling sex-ratios are determined nearly exclusively by temperature, so they are not off the hook.
“It’s like a band that is trying to effortlessly change key,” says Dr Tom Reed, a member of the research team from University College Cork, “but the bass player is shifting to C, the guitarist to D flat and the piano to E. Jazzy, perhaps, but it just won’t cut it in a changing climate.”
Can a symphony become a jazz ensemble?
So how are marine vertebrates adapting to the relatively rapid changes?
Some are relocating, but that can cause its own ecological problems. Some have nowhere to go—they are already as far south, north or as deep as they can go.
Dr Reed says species with a certain genetic flexibility, known as ‘phenotypic plasticity’, may be able to change the timing of their scheduled events. Phenotypic plasticity is the ability to express existing genes in different ways depending on environmental factors. It is the wriggle-room in your genes.
“In order to respond via phenotypic plasticity, individuals must rely on environmental cues that are typically imperfect”, he says. “For example, spring-spawning fish may benefit by spawning earlier in the year if seasonal plankton blooms occur progressively earlier in the year. But warm springs and early plankton blooms may not always go hand in hand.”
Beyond that, there is evolution. But can it happen fast enough?
Whatever music ocean life is making, we all dance to it. Perhaps it is time to pick up an instrument.