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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Common piddock found in Cornwall

March 3rd, 2010

Found on the lower shore of a beach in Cornwall, the common piddock (Pholas dactylus) is a bivalve that can grow up to 15cm long. Pholas dactylus is a borer and bores into peat, clay and even wood. It has phosphorescent properties and glows green-blue around the edges in the dark.

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Sea anemone in Bournemouth

February 26th, 2009

Photo: Steve Trewhella

The sea anemone, Diadumene cincta, was found under Bournemouth Pier. Diadumene cincta is a small and slender anemone and can reach up to 60 mm in height. It is usually orange in colour. On its oral disk, it has up to 200 tentacles, also orange in colour. The column is smooth and dotted with pores (cinclides) that release water from the body to allow the anemone to contract if disturbed. Diadumene cincta also has a defence mechanism in the form of stinging tentacles called acontia which are forced through the mouth.

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Chameleon prawns

December 2nd, 2008

Chameleon prawns (Hippolyte varians) have been sighted in Studland, Dorset. Hippolyte varians is a small prawn, up to 3.2 cm in length and is widely variable in colour, hence its name, from red to brown through to green or transparent with red or yellow blotches. Hippolyte varians uses this variable colouring as camouflage during the day but turn a blue-green colour at night independent of their habitat.

Photo: Steve Trewhella

A Ray’s Bream was discovered, also known as the Atlantic pomfret (Brama brama) in a rock pool at West Runton, Norfolk. The fish was approximately 50cm long from nose to tail.

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Increased portuguese man o’war sightings

August 30th, 2008

There have been increased reports of Physalia physalis sightings over June, July and August. Physalia physalis or the Portuguese man o’war consists of a large gas-filled float (pheumatophore) which reaches 300mm in length and 100mm in width. Physalia physalis is light blue/purple in colour and has a bright pink crest running along the top of the float or pheumatophore that acts as a sail. Physalia physalis has polyps under the pheumatophore for feeding, defence and reproduction that are several metres in length. Physalia physalis are carnivorous and feed on small crustaceans and larval fish primarily. They do this by delivering an immobilising sting to their prey with tentacles covered in nematocysts or stinging cells. The sting of Physalia physalis is potent, even after death.

Photo: Steve Trewhella

There have also been reports of sightings of Pelgia noctiluca and Buoy Barnacles in Dorset.

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Seahorses in Dorset

June 26th, 2008

There have been reports of a number of seahorses sighted during dives in Dorset. The Seahorses are of species Hippocampus hippocampus and Hippocampus guttulatus. Many of the seahorses present were pregnant.

Photo: Steve Trewhella

Hippocampus hippocampus, otherwise known as the short-snouted seahorse can reach about 15cm in length but has a short and fat body shape. It has a short snout, hence its name, that is less than one third of the length of its head. Hippocampus hippocampus has a spine above each eye and bony tubercles on its body that give the seahorse a rather knobbly appearance. Hippocampus hippocampus varies in colour from brown to orange, purple or black and is one of two main species of seahorse found in the UK.

Photo: Steve Trewhella

The long-snouted seahorse, Hippocampus guttulatus, also called the spiny seahorse, grows to about 15cm in length. Like the short-snouted seahorse (Hippocampus hippocampus), it has bony tubercles that give the body a knobbly appearance. This seahorse also has fleshy protuberances on the back of its neck which gives the appearance of a mane. Hippocampus guttulatus is green-yellow to reddish-brown in colour, often with bluish-white spots and flecks.

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The celtic sea slug

May 9th, 2008

The Celtic sea slug (Onchidella celtica) has been sighted on a rocky outcrop at St. Martins Point, Guernsey. Onchidella celtica is a small oval slug with a fleshy body or mantle that is dark green to black in colour and is covered in tubercles. It is about 12mm in length and 6mm in width. When motionless, the mantle covers the head and the foot. The head is only visible when the slug is mobile.

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Sightings of sea hares on Guernsey

April 10th, 2008

There have been a number of sightings of the sea hare Aplysia depilans on Belle Greve Bay, Guernsey from January-April. Aplysia depilans grows to about 30cm long and is brown to green in colour often with pale spots or speckles. As with all species of sea hare, Aplysia depilans has an internal shell and releases ink when disturbed. It is also a herbivore and feeds on seaweeds.

Photo of Aplysia depilans found here.

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Sea snail found depositing eggs and boar fish sighted

February 26th, 2008

Lamellaria have been found depositing eggs in Guernsey and Boar fish have been reported in Jersey and Dorset.

On Guernsey’s east coast, Belle Greve Bay, Lamellaria were found excavating holes in ascidians in order to deposit their eggs. Lamellaria has a shell of 10mm length and the animal can grow up to 20mm. This slug-like mollusc varies in colour; yellow, grey or lilac and often with coloured flecks of yellow, black or white. Lamellaria have internal shells enclosed by a mantle which is covered in tubercles. Lamellaria feeds on ascidians and lays their eggs in capsules deposited in holes eaten out of the ascidians by the female. Each flask-like capsule is holds up to 3000 eggs!

In Jersey and Kimmeridge bay, Dorset, Boar fish or Capros aper have been sighted. Capros aper is an oval fish, growing up to 30cm in size. They vary in colour from brick-red for individuals from deep water (200m or more), sometimes with yellow bars, to a yellow-straw coloured fish in shallower waters. It has small, rough scales and feeds on molluscs and crustaceans.

Click here to see pictures of the Lamellaria and Capros aper.

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Jellyfish in November

November 19th, 2007

This month, there have been a number of jellyfish sightings including the String Jellyfish in Cornwall and the Mauve Stinger in the North Channel.

The String Jellyfish Apolemia uvaria, is not actually a jellyfish but belongs to a related group Siphonophora and is related to the Portuguese Man o’ War. They were reported in large numbers and have been spotted off Plymouth sound in the last 4-5 weeks. These unusual creatures have not been recorded in Plymouth or Cornwall before. They are usually found in oceanic waters and have a nasty sting.

Recently, there have been several sightings recorded in the North Channel, North West Ireland and Western Scotland of the jellyfish Pelagia noctiluca, more commonly known as the mauve stinger.

Photo: Steve Trewhella

The mauve stinger can grow up to 10cm in diameter; its tentacles can extend up to 3m and are covered in nematocysts. Its colour varies from mauve-brown to purple and pale red and the exumbrella or the outer surface of the mushroom-shaped bell is covered in nematocyst-bearing warts, pink or mauve in colour. Nematocysts, also called stinging cells, contain small poisoned tubes that deliver its sting. Pelagia noctiluca usually feed on sea squirts and other small jellyfish.

These species also have a nasty sting so approach with care!

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