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Impact of climate change on marine life

Organisms most likely to experience “significant problems” with climate change are algae, kina and microscopic marine life, said Dr Simon Hills in his talk about the impact of climate change on marine mollusc fauna.

Dr Simon Hills (Ngati Porou) is a senior lecturer at Massey University's school of agriculture and environment.

Climate change entails ocean acidification due to carbon absorption, and changes in ocean circulation, he said. Susceptibility occurs during an organism's life cycle. Each stage is vulnerable to different issues.

Because all marine organisms have adapted to live in a particular temperature over time, distribution of those organisms will change, he said.

“We can look at the past to see what climate change effects on oceans look like. When it is warm we start seeing species normally seen in more tropical places like Australian waters. The temperature increase increases the risk of other species taking hold.

“Ship movement in and out of port will bring about some concerns.”

Rough weather is one factor that causes pupu spawn but scientists cannot be certain what effect a rise in sea temperature will have on cues during the organism's life cycle, he said.

Ocean acidification

Acidic sea water can dissolve molluscs' shells. Increased acidity makes it harder for a mollusc to create its calcareous exoskeleton, said Dr Hills.

The impact of acidification on larval stages is also significant. High concentrations of carbon in the ocean in the past impacted shell development in juvenile scallops.

“When they grow their first shells, they are susceptible to changes in pH.”

A pH level measures how acidic or alkaline something is. A pH of 0 is totally acidic, while a pH of 14 is completely alkaline. If ocean pH is high and calcium carbonate levels are low, juveniles are unable to grow into adults.

“A lot of research to date has been done on individual species but ecosystems are extremely complex. It is hard to predict how changes in climate will affect each of these interactions.”

Few ecosystem-scale studies have been carried out, but the future of kaimoana in Tairawhiti entails altered ecological communities and smaller shellfish populations, and smaller individuals can be expected as growth rates and respective life cycles are impacted, he said.

Population and individual resilience is likely to be compromised. Monitoring and management will help ensure species are able to cope with present and future changes but changes will need active engagement, he said.

“Communities need better access and better tools to enhance kaitiakitanga (guardianship).”