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For each day's sampling I fill in a spreadsheet not just of the species but also an indication of the relative abundance. This is a 5-point score: 1 refers to just one instance of seeing the organism out of all the drops of water that I view under the microscope that day. At the other end of the spectrum is 5 meaning that every sample seen under the microscope had numerous examples of the organism, i.e. a bloom.

On this page I will be providing a selection of graphs. It takes time going through the data and I will add material when I can, typically at the end of the year. The current species list has a total of 173. If there are any species or groups you are interested in please contact me.

For the latest news please go to Blog/News

The section below covers some interesting examples from 2021 - 2023

  • Diatoms

  • Protists

  • The tunicate Oikopleura

A Diatom

Small Periwinkle. Adults found on the side of the jetty

The larvae of Sea Mat colonies

Data compiled December 2023

The variety of diatom species varies considerably over the year and from year to year. The question mark for 2022 is probably human error, i.e. I was not identifying the smaller diatoms especially distinguishing the differences.

Both the counts and the relative frequencies of all species show similar changes. Most significant is that the dominant blooms occur in summer and autumn. The spring peak is much lower. 10 years ago it was the reverse and in the literature the spring is always the time listed as when the greatest bloom occurs.

Below is a graph of a common and abundant diatom species, Odontella sinesis.  Interestingly, the changes in 2022 are repeated in 2023

Odontella sinesis a common diatom in the phytoplankton. This shows a pair after cell division

Protists species count.graph.jpg


Possibly linked to the rise in water temperature the main bloom of protists occurs in both years at the same time, July through to October. A slight peak in early spring is followed by a June dip, again consistent in both years. The species count graph is very similar to the relative frequency. 41 Protist species have been identified over the 2 years. The ciliate group of Tintinnids is especially common and found in every sample. The density builds through the spring and summer with high numbers in autumn especially in 2023 after a warm seawater summer.

Forams typically appear after rough weather when they have been lifted from the sediment into the water column. The graph shows this well: high occurrence in late autumn, winter and early spring. Most dramatic is the difference in the 2 summers: 2022 was a very calm period while 2023 was a "poor" summer where 2 storms, Antoni and Betty, in August caused a sudden spike in forams before the storms of late October.

Dinoflagellates also makes up a significant proportion of the protists and are found in every samples.

The bioluminescent Noctiluca does well in the autumn but in 2023 was blooming off Skomer throughout the summer coming into Dale in late August, remaining to winter. Dinophysis is easily missed as it never reaches high densities and is tiny but none were seen in 2023. Several species of Protoperidinium commonly occur especially in the first half of the year while the 4 species of Ceramium appear mainly in the second half and may reach bloom proportions.

Oikipleura and Tunicates:

Relative Frequency

For a discussion of the graph please click here to go to the Tunicate section.

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