Protists
Second to the diatoms, dinoflagellates are the second most important primary producer in the sea and yet are quite animal like. These single-celled creatures are always present in Dale plankton samples and are extremely varied from forms barely 25 microns to Noctiluca often visible to the naked eye at several millimetres across.
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Two different flagella are present. Some like Noctiluca are naked others are covered in armour plates or thecae.
The tiny dino, Akashiwo, approx 50 microns across
Noctiluca among barnacle larvae
Noctiluca extended tentacle used to catch food.
The Dinoflagellates
Noctiluca scintillans, approx 1mm across
Bouyancy is achieved by accumulating lighter ions in the cytoplasm. Noctiluca is the best example of a bioluminescent plankter and people use social media to track the best shores where waves break in a blue glow of light. While common in the open sea samples within the Haven usually only have this species in autumn.
Armoured or thecate Dinoflagellates
Tripos (formally known as Ceratium) spp, approx 200 microns
Dinophysis sp, approx 60 microns
Protoperidinium spp, approx 80 microns
Polykrikos resting cyst
The photo examples of Protoperidinium show the pink interior as a "heart" shape. This is a developing resting stage. When environmental conditions become stressful the dinoflagellates typically produce a resting cyst structure, quite distinct for different genera. They eventually sink to the bottom where they need several months before they are able to develop into a dinoflagellate.
Protoperidinium resting cyst
Haptophyta and Climate Change
As stated before, classification is difficult as there is so much biodiversity and variation within the single-celled organisms. This group contains an array of species that are mainly marine and probably the most important with regard to carbon cycles and climate change. This importance has existed for the last 150 million years. Some of these haptophytes have outer scales of calcium carbonate called coccoliths and a blizzard of these drop to the bottom of the oceans taking 25% of all sea carbon to create a limestone sea floor.
The haptophyte most abundant around Milford Haven is Phaeocystis and does not have a coccolith. Its significance, however, is also profound as it can cause huge blooms. These produce dimethylsulphide (DMS) which can stimulate/enhance cloud formation over the ocean and cooling.
These photos are of non-motile Phaeocystis when it comes together in colonies encased in mucilage. When blooms cocur in the Haven these coalesce into huge clumps of mucus often completely filling the plankton net. When cells are mobile they have two flagella between which is another extension called the haptonema from which the group get their name.
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Photo below is of a Phaeocystis colony with a polychaete larva stuck to the mucus
