Striving to preserve taonga species
The Royal Society recently launched a lecture series highlighting the research carried out by female scientists. Will Harvie reports on the work of an environmental chemist and a conservation geneticist.
Some years ago, Dr Sally Gaw and PhD student Phil Emnet spent 12 months monitoring Christchurch’s Lyttelton Harbour for emerging contaminants.
They were looking for the compounds found in everyday items such as soaps, shampoos and pharmaceuticals that might be showing up in marine environments and might be causing harm.
Others were already monitoring known problems, such as petroleum compounds. Gaw and her team of environmental chemists were looking for the chemicals little is known about. There was some overseas research available on these chemicals but it was patchy and more data were needed, especially in the New Zealand context.
They strongly suspected some of these compounds were ‘‘candidates for future regulation’’, Gaw told a Royal Society Te Apa¯ rangi audience in Christchurch earlier this month.
They tested the three wastewater treatment plants emptying into the harbour, the sea water itself, sediments and had a go looking for these chemicals in mussels.
‘‘We were trying to get an idea of what might be there and what we could analytically do at the university at the time,’’ she said.
And they found these compounds in the wastewater, including preservatives, some anti-microbials found in toothpastes, UV filters from sunscreens, human hormones including from contraceptives, and plastics.
The sea water and sediment tests also returned many of the compounds but somewhat differently. The mussel tests also returned positives but there were problems with the data and further work will start next year on shellfish.
While the results were specific to Lyttelton, it’s believed the same sorts of compounds are probably found in marine environments around the country.
Armed with the knowledge that these groups of chemicals were present, Gaw and PhD student Nicole McRae tested the effects of an anti-inflammatory drug called voltaren (diclofenac) on inanga (whitebait).
They selected voltaren because it’s one of the few emerging compounds that’s already been placed on international watch lists as a ‘‘contaminant of concern’’, Gaw said. It’s likely to be regulated in the future, she predicted.
Whitebait is a taonga species, of course, but it’s useful to science because it’s different from fish species tested for voltaren overseas. It has skin rather than scales, for example, so the pathway to contamination might be different.
They found a ‘‘toxicologically relevant response. The fish weren’t happy. They were showing signs that they were being affected at environmentally relevant levels,’’ Gaw said.
Other students of Gaw’s have found microplastics in sediments and green lipped mussels from the Canterbury region.
Gaw added that overseas research strongly suggests polar fleece clothing is a significant source of plastic contamination. She and colleagues weren’t looking for polar fleece, but it ‘‘generates a very, very large number of fibres. It would probably have been better if polar fleece had never been invented, in terms of what’s being shed into the environment,’’ she said.
Genomics and the kak¯ı egg dump
Researchers at DOC’s kakı¯ captive breeding programme in the Mackenzie Country had a problem. Two birds, one juvenile and one adult, didn’t look entirely like kakı¯, also known as black stilt.
The were perhaps more reminiscent of poaka, an Australian import that’s closely related and also breeds on Mackenzie Country riverbeds near Twizel.
But the eggs had been retrieved from a kakı¯ nest. What was going on?
Dr Tammy Steeves and her team of conservation geneticists at the University of Canterbury used DNA to sort out what these two unexpected birds were.
Using straightforward comparisons of chick DNA to parental DNA, they first determined the two were not kakı¯.
Nor it turns out, were they poaka, also known as pied stilt.
Instead, they were kakı¯-poaka hybrids, which was OK (but not great) as the two species are capable of interbreeding.
But that didn’t solve the problem of why the two hybrids were in kakı¯ nests.
The answer, Steeves told the Royal Society lecture in Christchurch, was probably something called an ‘‘egg dump’’.
They believe a poaka or kakı¯poaka hybrid simply laid an egg in a kakı¯ nest.
‘‘We don’t know how often this happens in kakı¯ or closely related birds,’’ Steeves said, ‘‘but I can say we are picking up these [hybrids] from time to time’’.
That’s important because the kakı¯ captive breeding programme and Steeves and colleagues’ DNA research are important to the survival of the critically endangered bird.
Kakı¯ used to be widespread on the North and South Islands. By 1981, there were 23 known adults. By 2017, there were 106 known adults. So they’re another taonga species.
Early match-making relied on pedigrees, knowledge about the ancestry of each bird. Genetic tools came along and told researchers bird DNA comprises about 1 billion base pairs and human DNA has about 3 billion base pairs.
Genetic research, however, relied on a handful of markers, Steeves said. It was hoped these markers would provide a good indication of the amount of poaka DNA in kakı¯. But nobody knew for sure.
‘‘What if we missed something? What if kakı¯ aren’t as genetically pure as we think?’’ she asked.
Answers may be at hand. In recent years, the related science of genomics has led to maps of many more than a handful of DNA markers. In some species, the entire genome has been mapped. Work to map the entire genome of kakı¯ and poaka is currently underway at the University ot Otago.
‘‘We are at the stage now where we literally need to watch this research because we don’t know if we will find evidence of poaka DNA in kakı¯,’’ Steeves said.
But wait, some spillover might be beneficial. Kakı¯ evolved in Aotearoa and are naive about mammalian predators. Poaka evolved among Australian mammalian predators and are less naive. Maybe a little poaka DNA would help kakı¯ survive.
It’s hoped genomic research will shed light on some other apparent truths established by the less powerful genetic research.
It showed that the more closely related two birds were, the fewer chicks they hatched. And the opposite was true as well: less related birds hatched more chicks.
The genomic data on kakı¯ hasn’t come back yet but early indications are that the genetic approach has worked and more chicks are hatching. However, the way forward is with genomics, Steeves said.
There was a diversity aspect to this as well. Genetic research showed match-making two distantly related kakı¯ created more diversity in offspring.
More diversity is valued because it creates resilience.
If the environment ever changes again (due to climate change, for example), then a population with low diversity would have an even tougher time surviving.
Again the genomic research should indicate whether this approach to increasing diversity is working, Steeves said.
❚ Drs Gaw and Steeves spoke in the opening lecture in a Royal Society initiative called Great Kiwi Research: Sharing Women’s Discoveries. Five more lectures will be held on the North Island next month. See royalsociety.org.nz
Black stilt/kak¯ı at Lake Tekapo. The endangered kak¯ı were bred in captivity at Twizel.
Dr Sally Gaw.