Not a waterproof coat in sight!

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Lecturing al fresco

Now there couldn’t be a finer way to listen to a lecture! These first-year undergraduate students from the University of Manchester are in Mallorca to learn about Mediterranean ecosystems and plant adaptations to the climate. On days like today it’s much easier to explain the challenges of the Mediterranean climate than on days when the rain is falling steadily. They also get to appreciate the view too; this view is out across the Bay of Pollensa where underneath the water there are large beds of seagrass called Posidonia oceanica or Neptune’s grass.

Shadowy underwater meadows

 Although underneath the waves, it not a seaweed and is actually a flowering plant. It can produce fruits which float on the ocean, but it also spreads very slowly by creeping rhizomes. A recent study published in the journal Plos One has shown that these clonal meadows of seagrass could be thousands of years old.

A washed up Posidonia oceanica rhizome

Growing at depths of about 1-45m (depending on water clarity) these seagrass beds are very important ecosystems. These meadows trap carbon dioxide and release oxygen in coastal waters through photosynthesis, provide energy at the bottom of the food chain and act as nursery grounds for many fish and invertebrates. The environmental importance of this ecosystem is reflected by its protection as a priority habitat by the legislation of the EU Habitat Directive and by the programs aimed at conserving it.

Sculpted mounds of debris

These meadows also have important effects on the seashore. Debris is washed-up from below the sea and collects on the beaches, sometimes forming great sculpted ‘cliffs’ of  plant material. These heaps of dead seagrass leaves and rhizomes are striking, but far more curious are the fibre balls which can also be found on some beaches. Wave action on the beach smashes up and wears away the tissue of the seagrass leaves, leaving only the leaf veins which get tangled up and moulded into these pebble shapes.

Fibre balls in the herbarium collection.
Dead leaves and fibre balls on the seashore

Which ever form the material ends up on the beach in, once there it helps to stabilize the shifting sands to build dunes, to retain water and to provide nutrients which allows plants to colonize the strandline.  Plants such as this lovely yellow-horned poppy (Glaucium flavum) which sadly isn’t in flower yet.

Glaucium flavum

Best go back to staring a that sunny view………..

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