Plastic bags have become so common around the capital's shoreline, divers call them "Wellington jellyfish".

Rob Wilson, organiser of clean-up diving group Ghost Fishing, said he and his crew regularly filled two sacks with plastic bags during their monthly clean up. But the majority were missed, obscured by silt.

"They are more prominent within the harbour, being an enclosed waterway, and storm drains feeding into it," he said.

"Around the Southern Ocean coastline we do find them embedded and tangled in weed. Anywhere there are fishing vessels, plastic bags are common."

It's not just Wellington. Wilson's dive crew have just completed their first regional clean up in Auckland, and he said they found more of the same.

So our shopping bags are finding their way to the country's shores, but what are they doing once they are out there? It's not good.

GHOST FISHING Plastic bags are common in our seas.

TURTLES MISTAKE BAGS FOR REAL JELLYFISH

Dan Godoy, of Massey University's Coastal-Marine Research Group, said a third of turtles washed up dead on New Zealand beaches had swallowed plastic, and the type of flimsy film used in most shopping bags was the worst culprit.

The creatures would suffer a "horrific" death, according to Godoy, as their digestive tract became blocked, and they either starved or died after their intestinal walls were ruptured.

AUCKLAND ZOO Auckland Zoo found 106 pieces of plastic inside an endangered hawksbill turtle, which died after 13 days of intensive care.

In August a critically endangered Hawksbill Turtle washed up near Mangonui. It later died at Auckland Zoo, and was found to have eaten more than a litre of plastic.

UP TO 90 PER CENT OF SEABIRDS EAT PLASTIC

Auckland Museum curator Matt Rayner has seen the devastating effect on seabirds first-hand.

Working alongside researchers from the University of Tasmania to autopsy 1700 birds from both countries, Rayner said 37 per cent had eaten plastic.

A piece of research published by the National Academy of Science in the United States in mid-2015 estimated up to 90 per cent of seabirds ate plastic.

The study found the highest area of expected impact occurred at the Southern Ocean boundary in the Tasman Sea between Australia and New Zealand, which contrasted with previous work suggesting the area was relatively untouched by human pollution.

SUPPLIED Dan Godoy said thirty per cent of stranded turtles has plastic in their stomachs

BIRDS FEEDING PLASTIC TO THEIR YOUNG

On the Otago Peninsula, albatrosses were found to be feeding plastics to their young.

Department of Conservation Ranger Jim Watts said hard plastic had been found in the chick's regurgitations.

SUPPLIED Dan Godoy has extracted many pieces of plastic from the intestines of death turtles in New Zealand.

"In the 2016-17 breeding season, 23 chicks fledged and in the nine regurgitations that we found and collected, plastic fragments were recovered from eight of these. In previous seasons plastic has also been found in a handful of regurgitations," he said.

"Northern royal albatross are surface feeders, scooping prey from the surface of the ocean. They mainly feed on squid, other cephalopods and fish.

"Adult birds could be scooping up plastic floating on the surface inadvertently or mistaking it as food.

SUPPLIED This Fairy Prion was found on a West Coast Beach with plastic inside its gizzard.

"The danger to the chicks is it is indigestible and in large quantities the plastic makes the albatross chick feel full so they may not beg for more food from their parents. Plastic has no nutritional value so the bird could potentially starve."

PLASTIC IN THE FISH WE EAT?

Ongoing research from the Auckland University Institute of Marine Science has shown of eight species common in New Zealand, only one did not eat plastic.

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Lead researcher Ana Markic, said the fish were species Kiwis regularly bought from local markets.

Markic was the first to explore plastic's impact on Kiwi fisheries, with neither the fishing industry nor the Ministry for Primary Industries having investigated in the past.

A 2017 United Nations report estimated that plastic production reached 322 million tonnes in 2015, which was expected to rise to about 600 million tonnes by 2025, and exceed one billion tonnes by 2050.

STUFF New data suggested a 2.5 million square-kilometre plastic patch has developed

An overview of lab experiments found that a lot of marine life ate microplastics, including molluscs and fish, and the plastics were observed in several studies to move up the foodchain.

However, the research concluded that accumulation was unlikely, since most microplastics would not enter the flesh of the creature.

Over 220 different species were found to ingest microplastic debris in nature. Excluding birds, turtles and mammals, 55 per cent were species of commercial importance, including mussels, oysters, clams, common shrimp, lobsters, anchovies, sardines, and many fish.

"In microplastic-exposed aquatic organisms the digestive tract contains the largest quantities of microplastics.

"However, seafood innards are normally discarded before human consumption, except for bivalves, echinoderms and some species of small fish," the report read.

MARINE MAMMALS AFFECTED

The UK government said experts estimated that plastic is eaten by 31 species of marine mammals and more than 100 species of sea birds.

As a study cited by the government explains,"when seabirds, sea mammals or fish ingest plastic particles, blocking of the gut is likely to harm or even kill the organism".