u3a

Exmouth & District

Lichens of the Estuary – December 2020

Members of the botany group spent some time exploring the lichens of the estuary flood defence wall, adjacent to the railway line and cycle track, on Tuesday 15th and Thursday 17th December. We were lucky not to get wet though it did get pretty cold after a while. 

We started off exploring the yellow and orange lichens growing on the wall. This lichen community corresponds to one of the lichen zones of rocky seashores where lichens can be seen in three main colour zones; the black zone, predominately the darkVerrucaria sppOf the intertidal area where lichensare submerged when the tide comes in; theyellow/orange zone, the Caloplacas and Xanthorias, exposed to a lot of sea spray; and the grey zone, predominantly Ramalina spp., exposed to light spray and harsh conditions. A look through a hand lens revealed a world of ‘jam tarts and volcanoes’! – or to put it technically, apothecia and isidia, the lichen reproductive bodies (Apothecia can be seen in photo one).  

We then moved up to the grassy field where the yellow Xanthoria grows on trees alongside several species of grey fruticose lichens, with one point of attachment, and the crustose lichens which cling tightly to the bark (or walls) and can’t be removed without damaging the substrate (photo two shows both of these structures).

Another fascinating world that’s often overlooked. Let’s hope we can enjoy it again in a different habitat very soon. 

Botany group