The first plastic bag found in the ocean has been detected by researchers using data logged in historic records.
Continuous plankton recorders (CPRs) were used in the 1930s to capture samples of plankton.
The CPRs were metal boxes fashioned and towed behind ships and captured the plankton during their passage but also picked up plastics as they moved along, the BBC reports.
Believed to be a type of species that is an indicator of ocean health, the plankton provided key information for fisheries but also key information on ocean rubbish.
Lead researcher Dr Clare Ostle, from Plymouth's Marine Biological Association, says that whenever something became trapped on the recorder, it had to be removed and then recorded in a log.
"We search through [those logs] and what we realised was that we had some really early, historic entanglement cases of plastics," Dr Ostle explained.
"We can build a time series from that - so we can actually see the increase in larger plastic entanglements."
The first recording of a plastic bag was off the coast of Ireland in 1965 and researchers say it could be the first ocean litter to have been detected.
By studying the logs, researchers also found there had been an increase in ocean plastic since the 1990s.
The number of plastic bags found has also decreased in recent years but could not be attributed to bans or controls being put in place.
With plastics and microplastics being a danger to marine life, researchers involved in studying the logs hope the “wave of awareness” will help in litter reduction in our oceans.