Marina marine life

November 2nd, 2010

A marina ramble (or was it a pontoon safari?) was organised by John Hepburn with permission from the Managing Director of Plymouth’s Mayflower Marina, Charles Bush on Saturday 23 October.

There was a good turnout and lots of interest in the non-native species that arrive and thrive on boat hulls, chains and pontoons. Luckily, the MBA’s John Bishop was there to talk about why marinas are so important for non-native species and point out some of the sea squirts, molluscs, sponges and seaweed that cover all available surfaces.

A different perspective on Mayflower Marina. Photo: Keith Hiscock

Mussels and anemones (the orange ones are Diadumene cincta) on a floating pontoon. Photo: Keith Hiscock

There was an opportunity to snorkel amongst the pontoons too. Those in the water were rewarded with lots to see despite the water being a bit murky, due to spring low tide and a lot of rain.

The pontoons and boat hulls are unique habitats in that the plants and animals that grow on them aren’t subject to tidal movement (floating surface). The pictures how much life there is, taking advantage of the prime underwater real estate.

A plastic settlement panel after 8 weeks in a Plymouth marina. Photo: John Bishop

Predators that can’t swim aren’t able to get up onto floating structures so some of the filter feeding animals (e.g. the pretty oaten pipes hydroid) which would usually have been munched by sea slugs in the summer are still there in mid autumn!

Some of the large seaweeds such as the non-native Wakame (Undaria pinnatifida) also seem to be surviving the winter on pontoons, whereas on the rocky shore the familiar large-frond stage has given way by the end of the summer to the microscopic phase.

 For more information about marine invasive non-native (alien) species see the website of the Marine Aliens project.

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