SMM 2015 - How-the-whales-are-saving-the-planet-Tuesday

A giant skinny Nick Gales menaces his smaller brother.

 A stunning plenary session today. Introduced by President Nick Gales, three excellent speakers covered the positive role of whales in maintaining ocean ecosystems; how climate change is mediated via the jet stream and its implications; and climate change and the Arctic.

A giant smiley dolphin menaces Trish Lavery 

Trish Lavery, of the Department of the Environment, Australia, spoke with wonderful lucidity and enthusiasm on the topic of ‘Whales sustain fisheries: Blue whales stimulate primary production in the Southern Ocean’.

She started by noting that whales are not uniformly distributed across the oceans but associated with high productivity zones and that fertilisation of the oceans causes carbon to be drawn down from the atmosphere. Such fertilisation can be achieved by the defecation of whales – and she gave a clear example using sperms whales which feed at depth but defecate in the upper layers (in the photic/light zone) where the plant plankton (which underpin the productivity of the whole ecosystem grow). This movement of nutrients from the deeps means that sperm whales (at current population levels) contribute to the addition of some 200,000 tonnes of carbon more than they are using.  Whaling has hugely reduced the contribution that sperm whales now make.

Lavery also looked at blue whales – so like all baleen species – they feed and defecate in the upper levels. Hence no net gain might be expected and she commented on the advocacy from some to cull whales in favour of fisheries interests; a ‘bottom-up’ view. She noted that there has been a significant reduction in krill and that whilst this was typically linked to climate change, the removal of whales by whaling might have have played a part, noting that whaling selectively removed the older and bigger whales. Lavery was able to show a possible moderate stimulation of krill caused by the whales and she commented that whales being in balance with their ecosystem might explain why they have survived 30 million years ‘without eating all the fish’! She concluded by pondering about what other ‘ecosystem services’ the whale might be providing.    

Trish 

At the end of her talk and further to loud and prolonged applause, the president of the SMM, Nick Gales, commented that it was 'wonderful' that a paradigm shift in thinking was resulting from a student project.

You can link to Trish Levry's publications which will give a more fulsome and authoritative account of her work via Researchgate HERE  Incidentally in my blogs from meetings, I paraphrase what was said and strive for accuracy but welcome corrections.

It's all about the jet stream

Jenifer Francis of Rutgers University spoke on ‘Crazy Weather and the Arctic Meltdown’. She reminded us that CO2 in the atmosphere was at its highest level for 800,000 years; that the resulting warming was not evenly spread over the planet (with a particular focus in the Arctic).

She emphasised that weather was being driven by the Jet Stream - its strength and its location. A weak Jet Stream is being caused by sea-ices loss in the Arctic which allows major heat loss to the atmosphere in the winter. 

And a weak Jet Stream tends to stay in one place – hence, relative to what went before, weather systems tend to ‘get stuck’: this caused repeated storms (including in the Arctic and over the UK for example) and droughts in some places and enhanced precipitation elsewhere. The implications of this for marine mammals include those relating to sea-ice loss and changes in productivity - a theme picked up by the last speaker, Sue E Moore who spoke on ‘Marine Mammals as Sentinels to Impacts of Climate Change on Arctic Ecosystems’. She emphasised the likely movement of baleen whales north – so they may be net benefiters – and also the less positive implications for those species that are dependent on ice for resting and breeding (including walruses and polar bears).