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Previous Photos of the Month

Below are some of the photos that have appeared on the home page and represents some of the amazing and spectacular beauty of plankton

May 2024

Photographed on 9th May 2024 this is the first time I have found a living Evadne nordmanni at the Dale pontoon. These water fleas are quite different to the freshwater forms in that they are predatory. Generally they are a rarity in the Haven. Last summer a different species Podon appeared in Dale and did well for a few months before disappearing. Currently, Evadne has a thriving population off Skomer. High population densities there usually cause the eventual arrival, weeks later, of individuals in the Haven.

Photo is a stacked composite of 18 images taken with DIC lighting. In length the size is about 600 microns or 0.6mm.

Evadne cladoceran

April 2024

Photographed on 8th April 2024. Collected from Dale Fort Jetty a solitary specimen has appeared each April  for the last two years. During this time it has been unidentified despite much effort. Finally help arrived in the form of Prof. Otto Larink (co-author of Coastal Plankton - see details at the bottom of Methods page). He correctly identified it as an early trochophore polychaete larva of the strange Knot Worm Polygordius. The larva is surprisingly large at 1-1.5mm and this is a top view. Thank you Otto. 

Trochophore larva of the polychaete Polygordius

March 2024

The main diatom here is Corethron criophilum, one that I am always pleased to see. Not especially common in the Haven but pops up in the spring. This was in the 25th March 2024 sample when I took a stack of 25 photos to combine into one composite image. A x40 objective with DIC lighting was used. The length of the diatom is about 100 microns. The two additional cells below are Thalassiosira rotula which is beginning to bloom in the waterway. Corethron is considered an alien species, more typical of cold water like Antarctica where the highest densities are found. It is also a unique species of diatom for several reasons including having mechanically moving parts like the spines.

Corethron criophilum diatom Thalassiosira rotula

February 2024

During the mid-February sampling I was a little surprised to see a number of zoea crab larvae appear. While this is not particularly unusual to find zoea I have not found them so early in the year before. I rather like this photo as the larva is looking at the camera and the various spines, even the lateral ones, are visible. This is a stacked image made from 14 photos taken with a x4 objective lens on bellows mounted on a OM-1 camera. Twin flashes, the main one below and a fill in one above. 

Zoea Crab larva Carcinus maenas

January 2024

 Young Veliger larva, most likely of a Small Periwinkle Melaraphe neritoides. Approximately 200 microns across. This tiny snail lives at the top of the shore and is very abundant on the Dale Fort jetty where the samples are taken. During the last few months periwinkle eggs have been appearing in the plankton which have hatched into a ciliated ball (the trochophore stage). In December the trochophore was very abundant and now these have metamorphosed into veligers. The one pictured was photographed on 30th December and has withdrawn inside the shell. They spend only a matter of days in the plankton before settling out on to the shore. That is if they are lucky as most will drift to the wrong habitat and die before finding a suitable location.

Veliger of Melaraphe periwinkle

December 2023

Forameniferans (often called forams) are a group of single-celled protists, many only known from fossils. They are essentially amoeba-type creatures that live in a shell called a "test" made from calcium carbonate. Around Dale most are very small, this one being about 120 microns in length. The tiny pores in the surface allow specialised cytoplasm from the cell to pass through to collect food. There are more than four different species appearing in these samples, some rounded others elongated. They are not abundant members of the plankton and really live in the surface sediment at the bottom of the Haven. Heavy weather in the autumn disturbs them bringing them up into the water column. During November they were especially common due to the gales. This one was photographed at the end of November.

Forameniferan

November 2023

An isopod crustacean, Gnathia. Photographed in the sample of 17th November 2023. Almost 4mm long this is a zuphea stage-3 larva. The non-feeding female adult lives on the rocky shore and releases tiny zuphea larvae into the plankton where they actively swim to find a fish. This can take days or weeks and once attached sucks blood for a day or two before turning into a praniza stage 3 larva, sinking to the shore digest the meal over weeks. Find out more here.

October 2023

Radiolarian, Acanthometra. 

This is a beautiful single-celled protist that I have not previously found in the Haven. The spicules are uniquely made of strontium sulphate (called celestite) and, like the spokes of an umbrella, hold a membrane out to create drag and reduce sinking. The membrane here was about 300 microns across, Photo graphed in the sample on 16th October 2023

Predatory marine worm Tomopteris

Tomopteris, a predatory polychaete worm, 1cm in length, beautifully adapted to live in the open water. A completely transparent worm, very difficult to see collected off Skomer at 40m depth on 25th September 2023

See Polychaetes

September 2023

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