A SURVEY of the River Fowey's underwater habitat has revealed a wealth of wildlife thriving in waters of high purity.
The study was instigated by Clare Marshall as part of her studies for the second year of a marine science course at Falmouth Marine School.
Initial mapping took place on September 10 at Polruan Pool using remotely operated vehicles lent by Plymouth University, and on Saturday divers took the plunge to assess the presence and extent of sea grass or eel grass, a nationally protected habitat.
Fowey Harbour is a Voluntary Marine Conservation Area (VMCA), and those behind the study hope to confirm healthy biodiversity and secure its future from threats to wildlife, such as dredging.
Eel grass grows in soft sediment such as gravel, mud and sand, which can reveal information about the composition of the riverbed. It naturally dies away in October, meaning that the gathering of resources to conduct the underwater mapping has been a race against time.
"The presence of eel grass is a good indicator of water quality," said Miss Marshall, one of the divers who spent almost an hour examining the riverbed.
"Within the eelgrass, species seen included snakelocks anemone, daisy anemone, sand mason worms, sea lettuce and brittlestar. Other species may be identified following analysis of video and photographs from both surveys."
Plymouth University was enlisted to help her with her research following an approach from Natural England.
"Getting equipment to do marine surveys can be difficult," said Miss Marshall, who is a volunteer for Cornwall Wildlife Trust and has conducted a similar survey in Looe.
Saturday's dive was organised with the assistance of Cornwall Wildlife Trust's Seasearch group.
Cat Wilding, the group's marine survey officer, said: "We have a particular interest in collecting data on important habitats such as sea grass meadows, which are nationally protected by a Biodiversity Action Plan, and provide shelter for fish and crustaceans, acting as an important nursery ground for many commercially valuable species."
Claire Hoddinott, environmental officer for Fowey Harbour Commissioners, said the results of this survey would provide a baseline reference for future studies.
"In the longer term it's something we're developing with the Falmouth Marine School students to find a working method for future study," she said.
"This sort of work is brilliant for Fowey; we get something from it that we haven't had for some time. It's been decades since the last official surveys."