A spokesperson from the Scottish Environment Protection Agency (SEPA) said:
"Every day SEPA works to protect and enhance Scotland's environment. SEPA has received reports from members of the public regarding a yellow substance on the surface and banks of Loch Lomond and Loch Long. SEPA Officers attended the area to investigate potential sources and take samples of the substance. Our investigation has confirmed that the substance is pollen from conifer trees. We would advise members of the public to contact our 24-hour Pollution Hotline on 0800 807060 or use our online form at sepa.org.uk/report to report any potential pollution events."