The Plankton Project: A mid-project report on surveying the near-shore plankton of Norfolk.

Elizabeth Beston

The near-shore plankton of Norfolk is historically under-recorded, with a literature search only yielding a few CEFAS (Centre for Environment, Fisheries and Aquaculture Science) surveys from 2016-2018 from Blakeney Point (CEFAS 2018/19). The Continuous Plankton Recorder (CPR) survey collects plankton data from the North Sea around Norfolk, but far from shore (CPR Survey 2023). The Plankton Project aims to fill this data gap by collecting and recording plankton species from around the Norfolk Coast.

Four sampling sites along the Norfolk coastline were chosen for their accessibility (having a hard-standing area such as a pier or quay from which to sample) and their different conditions (Figure 1). The estuary of the Great Ouse River at King’s Lynn is a brackish site with a very muddy substrate. The Quay at Wells-next-the-Sea joins the North Sea to the local saltmarsh. The substrate here is fine sediment, and it is sheltered from the coastal winds. Cromer Pier is the most exposed of the sites and the sampling location is approximately 160 metres into the sea from the high tide line. The pier sits atop the chalk reef, which is interspersed with other substrates including gravel and sand. Gorleston Pier is the sample site furthest East and South. The location here for surveying is a small area tucked into the pier walls, facing the beach, away from the strong currents at the mouth of the estuary. The substrate here is sand.

The project began in April 2023 and will run until the end of March 2024. This report presents the methods and preliminary findings of the first 6 months of the project. Transport to the sampling sites is being supported by the Porcupine Marine Natural History Society (PMNHS) via the Roger Bamber Award.

Fig. 1: A map of sampling sites in relation to each other (Google Maps 2023) and photographs of the locations

The same weighted plankton net sampling technique is employed across all sites, although the number of tows varies depending on the sea conditions. The tow number is usually 10 (vertical tow to a depth of 1 metre as indicated by a marker ribbon on the plankton net rope) but if sampling is difficult due to high winds, or if there is a lot of sediment blocking the net, a lower number of tows is employed. The amount of water sampled through the net is roughly calculated after each sampling session by multiplying the area of the plankton net opening (0.049 m) by the distance the net travels through the water (1 m), multiplying by 1000 to convert to litres and then adding the volume of water used to wash through the filters (0.1 l). The plankton net used has 53 μm netting with a 250 mm opening. Half of the tows are done with a 150 μm filter attached to the bottom of the net, and the other half with a 53 μm filter to capture smaller species. Samples are taken each month at each site within half an hour before or after daytime high tide. The sample is kept in a plastic watertight container and kept in a cool bag with a cool pack and towels for the duration of the journey back to the laboratory. Within 1 hour of returning to the lab, the larger zooplankton are extracted from the sample via pipette and placed in small Petrie dishes labelled for crustaceans, molluscs, worms and other. Some of the organisms are observed alive before the extracted zooplankton is preserved in 10% buffered formalin for more detailed examination. Phytoplankton is observed alive, and samples are extracted by pipette directly from the sample pot. Samples are continuously extracted and observed until no more novel species are seen. Samples are observed using a dissecting and a compound microscope and the presence of different species is recorded. An informal estimation of any dominant species is made through general observation. The main texts used for identification can be found in the reference section. The data collected so far can be analysed in several different ways: by location, by species, by month/season, as well as by other variables such as water temperature, salinity, or weather conditions. All of these variables can be compared against each other and the species lists generated can be compared with off-shore sampling species data (for example by the CPS). Examples of some observations are provided below:

Location and species

There were species of phytoplankton that appeared at all sampling sites across the coast of Norfolk in the first 6 months of the project, for example, the diatoms Actinoptychus splendens (Shadbolt) Ralfs ex Pritchard 1861, Guinardia flaccida (Castracane) H.Peragallo 1892 and Zygoceros rhombus Ehrenberg 1839. The Calanoid copepod Centropages hamatus (Lilljeborg 1853) was also present at all sampling sites. Other species were specific to location. The diatom Bacteriastrum hyalinum Lauder 1864 was only present in samples from Gorleston Pier, as was the dinoflagellate Prorocentrum micans Ehrenberg 1834 (see Figure 2).

Fig. 2: a. Actinoptychus splendens, b. Guinardia flaccida, c. Zygoceros rhombus, d. Centropages hamatus, e. Bacteriastrum hyalinum, f. Prorocentrum micans

Temporal and spatial variations

There were a few species that consistently appeared in all samples from all sites and in all months. The diatom Zygoceros rhombus Ehrenberg 1839 is an example of one such species. Copepods and crustacean nauplii were present in every sample collected. The absence or presence of certain species in certain months across the sites was interesting. For example, the sea-foam-causing flagellate Phaeocystis globosa Scherffel 1899, appeared at all four sampling sites, blooming in different months. This organism first appeared in samples from Wells Quay and Cromer Pier in April 2023. In May, it appeared at King’s Lynn Estuary and Gorleston Pier, and seemed to increase in concentration at Wells Quay and Cromer Pier. By June, P. globosa had disappeared from samples from King’s Lynn Estuary and Wells Quay, but continued to be present at Cromer and Gorleston Pier. Small amounts of this species (Figure 3) reappeared in the Gorleston Pier sample in September 2023.

Fig. 3: Phaeocystis globosa

Possible effects of salinity

The estuary at King’s Lynn is the sample site with the lowest salinity (ranging from 11.8 ppt to 27. 1 ppt), which could be associated with certain species (further hypotheses would have to be formulated and tested). For example, there have been no Carcinus maenas (Linnaeus 1758) larvae observed at this site as yet. Out of the four sampling sites it also appears to have the most diverse range of rotifers (Cephalodella sp. Bory de St. Vincent 1826, Keratella sp. Bory de St. Vincent 1822, Notholca sp. Bory de St. Vincent 1826, and Trichocerca sp. Lamarck 1801) (see Figure 4).

Fig: 4: a. Carcinus maenas, b. Rotifers (left to right) Cephalodella sp., Keratella sp., Notholca sp. and Trichocerca sp.

Limitations of the data - While dominant species and blooms were recorded, no quantifying techniques were used to count plankton. It should also be noted that as the project has progressed, the knowledge of the observer has increased, allowing for more accurate and higher taxonomic identification in later sampling.

This project is only halfway through, and the first full year of data collection will be complete at the end of March 2024. Preserved specimens of individual species (in 10% buffered formalin) are occasionally sent to the Natural History Museum. No feedback regarding these donations has yet been received. The data collected is being sent, via PMNHS, to the NBN Atlas and the species information will be available online at planktonproject.org.uk. A full report of the first year of sampling will be available in the summer of 2024. The Plankton Project also engages in science communication, with talks and workshops about diatoms being premiered at the Norwich Science Festival in February 2024. An international marine plankton bioblitz is being organised for March 2024. If you are interested in taking part, please contact elizabeth@beston.me.

References

Castellani, C. and Edwards, M. (ed.) (2017) Marine Plankton: A Practical Guide to Ecology, Methodology, and Taxonomy. Oxford: Oxford University Press.

CEFAS 2016-2018. CEFAS Data Portal Available at: https://data.cefas.co.uk/search/1/phytoplankton%20glaven (Accessed 19 July 2023).

CPR Survey 2023. CPR Survey Available at: https://www.cprsurvey.org/ (Accessed 19 July 2023).

Conway, D.V.P. (2012) Marine zooplankton of southern Britain. Part 1: Radiolaria, Heliozoa, Foraminifera, Ciliophora, Cnidaria, Ctenophora, Platyhelminthes, Nemertea, Rotifera and Mollusca. Edited by A.W.G. John. Plymouth: Occasional Publications. Marine Biological Association of the United Kingdom.

Conway, D.V.P. (2012) Marine zooplankton of southern Britain. Part 2: Arachnida, Pycnogonida, Cladocera, Facetotecta, Cirripedia and Copepoda Edited by A.W.G. John. Plymouth: Occasional Publications. Marine Biological Association of the United Kingdom.

Conway, D.V.P. (2012) Marine zooplankton of southern Britain. Part 3: Ostracoda, Stomatopoda, Nebaliacea, Mysida, Amphipoda, Isopoda, Cumacea, Euphausiacea, Decapoda, Annelida, Tardigrada, Nematoda, Phoronida, Bryozoa, Entoprocta, Brachiopoda, Echinodermata, Chaetognatha, Hemichordata and Chordata. Edited by A.W.G. John. Plymouth: Occasional Publications. Marine Biological Association of the United Kingdom.

Google Maps 2023. Norfolk Coast Available at: https://www.google.com/maps/@52.7308676,1.0436382,10.16z/data=!4m2!10m1!1e4?entry=ttu (Accessed 9 November 2023).

Kraberg, A., Baumann, M. and Dürselen, C.-D (2010) Coastal Phytoplankton: Photo Guide for Northern European Seas. München: Verlag Dr. Friedrich Pfeil.

Larink, O. and Westheide, W. (2011) Coastal Plankton: Photo Guide for European Seas. München: Verlag Dr. Friedrich Pfeil.

Tomas, C.R. (ed.) (1994) Identifying Marine Plankton. San Diego: Academic Press.