Ten of thousands of dead and dying starfish and shellfish have been washed up a beach.
Mussels, crabs, razor clams and starfish have been seen on the sands at Saltburn-by-the-Sea, south of the River Tees.
The Environment Agency (EA) said it was caused by the weather and high tides and was normal for the time of year.
But Stuart Marshall, 58, who owns a beach side hut, said:
“It is devastating.
“A large deposit of black debris had just arrived on the tide and was not normal.
“We do get bits of coal from time to time but not anything like this.”
Helen Whitworth, from Northallerton, North Yorkshire, also said the black deposit was unexpected.
She added:
“This black area is not usually here – usually it’s a really beautiful beach.”
The EA said the recently arrived black substance was coal deposit “which is not unusual for this stretch of coastline”.
A spokesperson said:
“While we know people are concerned, the combination of recent heavy swell, spring tides and onshore winds means natural wash ups will occur more often.
“Starfish, razor clams and mussels were easily dislodged during storms and some young fish were vulnerable to being stranded on shallow gradient beaches such as Saltburn.”
