The Krustenstein of marl lakes;An indicator of lake ecological

status

Cilian Roden G.M.I.T.

Paul Murphy Eireco

Some Natural History

• The krustenstein is abundant in Irish marl lakes

• It occurs between 0-4 m depth• It can occupy up to 50% of the euphotic

zone• The major species is the cyanobacterium

Schizothrix fasciculata,• But many other species occur.• A large part is precipitated CaCO3

cross sections

… and horizontal extent

In 22 marl lakes, clear water is commonest habitat

Trouble ahead? decaying crust reveals eroded rock

Lough Corrib 2 m

The end of the road: green algae and zebra mussels have replaced the crust

Lough Mask 3 m

… and in Derravaragh

CorribLeane

Erosion is not seen on the limestone of Lough Leane, a “Najas” rather than a marl lake

In Muckanagh erosion can go no further!

But old rocks indicate old ecological status

In some clear water loughs, extensive

Krustenstein and a few zebra mussels co-exist,

Are nutrients rather than introduction Determining colonization?,

Bleach Lough Co. Limerick,

Hypotheses

• Extensive krustenstein indicates unpolluted marl lakes

• It erodes limestone in a characteristic way, thus eroded rock indicates former lake nutrient status

• Zebra mussels only replace krustensteinin low secchi, low euphotic depth, marl lakes, i.e. polluted ones!

Thank you to….

• National Parks and Wildlife Service

• Jim Ryan and Áine O Connor

• Galway Mayo Institute of Technology

• Bryan Kennedy of E.P.A. Castlebar

• Heritage Council