TO divers off Port Stephens they’re the bashful eight; the newest sea slug discoveries that have blended into the nutrient-rich floor of Nelson Bay until now.
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Last weekend’s Sea Slug Census by 32 underwater camera-armed divers and Southern Cross University researchers was never likely to find a spectacular new species, mainly because the brightest slugs are the easiest to spot.
What they uncovered instead, the dive’s organiser Tom Davis said, are eight new species that amount to a slug-lover’s delight.
“We usually might find one or two new species but to find eight is a great result,” Dr Davis said.
“They weren’t the most brightly coloured or spectacular species, but they were more interesting to the dedicated sea slug searcher.”
The newly-recorded slugs include the semi-translucent Berthella Stellata, the unglamorous land slug-like Onchidella Nigricans and, most strikingly, the coral-eating Tenellia Minor.
Rather than presenting a threat to local coral, Dr Davis said, the Tenellia Minor slug photographed in the bay seemed more taken with algae.
“It would certainly be interesting to establish what it’s choosing to eat,” he said.
“Its discovery almost raises more questions than answers.”
Besides its shimmering reputation for bright and diverse sea slugs, Port Stephens has become a canary in the mine shaft for researchers tracking the warming of the world’s oceans.
In 15 seasonal slug surveys held at Port Stephens since 2013, Southern Cross University marine benthic ecologist Steve Smith said divers have found 20 species of sea slug further south than ever before.
“They’re a strong indicator of climate-driven changes, and we’re adding new species in Port Stephens that are at their record southward range all the time,” Professor Smith said.
“It enhances the high conservation value of the Port Stephens area.”
Some of the newly-recorded species found off Port Stephens would have travelled down the East Australian Current as larvae, Professor Smith said, and found enough food and shelter in Nelson Bay to thrive.
The next seasonal dive is scheduled for December when, Professor Smith said, he hopes more divers will expand the census area to the islands off Port Stephens and find more species of slug.
The census results will contribute to a scientific paper, currently being written, on how citizen scientists can gather valuable data on marine biodiversity.