Long-running geographically extensive marine ecological survey, providing the 'big picture' on global ocean change
Driven by almost a century of sustained plankton observations, scientific excellence and innovation, the Continuous Plankton Recorder (CPR) Survey is a globally recognised leader on the impacts of environmental change on the health of our oceans.
As a large-scale global survey, it provides the scientific and policy communities with a basin-wide and long-term measure of the ecological health of marine plankton. Established in 1931, the CPR Survey is the longest running, most geographically extensive marine ecological survey in the world. Home to a considerable database of marine plankton and associated metadata that is used by researchers and policy makers to examine strategically important science pillars such as climate change, human health, fisheries, biodiversity, pathogens, invasive species, ocean acidification and natural capital.
Our focus on the ocean plankton is important. Plankton sustains life on this planet by producing almost half the oxygen we breathe; it is the planet’s second lung.
Plankton are very sensitive to changes in their environment (e.g. temperature and pH) and due to their rapid turnover, they are excellent indicators of change in the marine environment. By monitoring plankton communities across basin scales and over many decades, the CPR Survey provides us with the ability to recognise changes in our marine environment over and above natural variations and trends.
Anthropogenic and global climate pressures on the marine environment are set to increase over the coming decades. Tools such as the CPR Survey help progress our understanding of changes occurring in the marine environment, and are essential to inform appropriate and effective management decisions at local, national and international levels.
2018 is a milestone year for the CPR Survey, marking 60 years of continuous monitoring in the North Atlantic. Although the Survey has been operating since 1931, standardised methods of sample collection and analysis were brought in to start in 1958, and have remained unchanged since then, resulting in a globally important and unique source of information on the health of the ocean.
In the marine environment, long-term datasets are rare, and those that do occur typically collect samples in coastal environments. In contrast, the CPR Survey operates in the open ocean, towing transects every month over thousands of nautical miles. By using the same methods over 6 decades, CPR data have helped progress our understanding of the marine environment, providing a form of “yard-stick” against which new measurements can be compared. Such baseline information is essential in identifying if, when and where changes have occurred, and help support the development of appropriate management of our seas.
Throughout 2018 we will be using the hashtag #60yearsofdata to highlight both the achievements of the CPR Survey during this time, and the work done on a day to day basis by the CPR team that goes in to running and maintaining this unique monitoring programme. You can follow these posts throughout the year on our official Twitter page.
Providing the 'big picture' on global ocean change from genes to ecosystems
The CPR Survey is of global importance in progressing understanding of natural variability and human-induced changes in our oceans. It is used by scientists, policy makers and environmental managers across the world. Over the last eight decades the purpose of the Survey has co-evolved with changing environmental policy, from purely monitoring plankton distributions to addressing and providing indicators for major marine management issues, ranging from fisheries, harmful algal blooms, biodiversity, pollution, eutrophication, ocean acidification and climate warming.
Many scientific firsts and insights have developed from examining and interrogating the CPR Survey's extensive time-series. The Survey has provided primary evidence of changes in global ocean biology for the last two IPCC reports and the UN’s first World Ocean Assessment. The results have included the first documented studies of large-scale ecological regime shifts, biogeographic, phenological and trans-arctic migrations in the marine environment in response to climate change.
The CPR Survey's science includes both operational and innovative, blue skies research, directed along four broad science themes:
Climate change is one of the greatest societal changes of the 21st Century. The continued collection and interpretation of CPR data provides unique insights into how the marine environment is responding and the potential for future change.
Biodiversity is fundamental for the functioning of the marine ecosystem. The taxonomic richness of the CPR data is a major resource enabling marine researchers to gain insights into the form and function of the ecosystem and how it is changing.
Marine bio-resources are increasingly used to support human population growth. The blue-economy is underpinned by bio-resources. CPR Survey science provides valuable insights for effective management strategies.
HEALTH AND WELLBEING
The health of people and marine sources of food can be compromised by some marine organisms. Harmful algae and bacterial infections appear to be on the increase. New molecular tools and techniques will allow the CPR Survey to contribute to this growth area.
Each theme is highly relevant to emerging scientific questions, marine policy requirements and the main societal concerns on the marine environment, such as:
- Are marine habitats changing?
- Is species diversity changing?
- Are food webs changing?
- Are human pressures changing?
The CPR Survey currently covers 8,000 nautical miles each month, presenting significant opportunities to maximise the monitoring potential of the pelagic environment. The development of new technologies and tools will enable the entire plankton community, from viruses to jellyfish, to be examined using molecular and optical technologies, in addition to instrumented data. Increasing the geographical range and scope of the Survey, particularly into sentinel ecoregions that are hotspots for environmental change, such as the Arctic, are essential in providing a truly global picture of our oceans.
Accessing CPR Survey data
The CPR Survey has an open and transparent approach to data availability, data requests and data citation. The Survey believes its plankton observation, ancillary datasets and associated metadata should be freely available to collaborating researchers. To find out which data are available and for more information accessing CPR Survey data, please visit our data portal at https://www.cprsurvey.org/data/our-data/
Research services we can provide
The CPR Survey offers a broad range of skills and expertise, from genes to entire marine systems. We use a variety of approaches, from the most conceptual (ecological theories) to the most practical (laboratory-based experimentation). These include:
- Provide robust and sensitive indicators of environmental changes
- Offer expertise in time-series analysis and interpretation of climate change impacts, phenology, regime shifts, biodiversity and invasive species
- Expertise in creating, managing and processing large geospatial databases
- Expertise in species distribution and biodiversity modelling
- Expertise in molecular analysis of plankton specimens, including preserved archival samples
- Expertise in bioinformatics analysis of next generation sequencing metagenetic datasets from marine environmental samples
- Phytoplankton and zooplankton
- Including organisms such as bacteria and viruses
- Harmful organisms from pathogenic eukaryotes to harmful algae
- Preparation of environmental assessments using historic datasets
- Development of appropriate planktonic indicators
- Report writing for governmental bodies, NGOs and companies
- Facilitating the application of science in response to specific targeted questions (e.g. for policy/environmental assessments etc.).
IMarEST accredited CPR technical course
This five day practical course is aimed at new technicians from established CPR surveys and scientists/technicians wishing to operate a CPR from a research vessel.
Taking a hands-on approach the course covers:
• preparation of filtering silks
• setting up and maintaining a CPR
• record keeping of CPR tows and samples
• CPR unloading and processing
• sample preservation
This course is available on request, email: CPRSurvey@mba.ac.uk for further information
The CPR Survey International Sample Archive
Collecting today for tomorrow's technology
We hold one of the oldest, most large scale sample archives in the world. Samples collected by the CPR Survey since 1958 are stored and carefully curated, providing a bank of samples available for future analysis using new and innovative methodologies.
During routine plankton analysis, every other sample on a tow is processed by our team of specialist analysts, before being archived. The remaining 50% of the tow is not analysed but archived immediately, resulting in a library of samples available for further/alternative analysis.
The archive is home to all our samples from routine North Atlantic, South Atlantic and North Pacific tows, in addition to one-off cruises, e.g. circumnavigation of the Arctic collected in 2012. Please contact us if you are interested in accessing our International Sample Archive, or would like more information on what is available.
CPR Survey data philosophy
The CPR Survey has an open and transparent approach to data availability, data requests and data citation. The Survey believes its plankton observation, ancillary datasets and associated metadata should be freely available to collaborating researchers. Increasing the number of scientists that can access and work with CPR Survey datasets will accelerate the progress of marine ecological science and understanding; enhancing the societal benefit derived from Survey data.
To find out more about our data, and for information on how to access them, please visit our data portal at https://www.cprsurvey.org/data/our-data/
Since the first Continuous Plankton Recorder was towed by the SS Albatross between Hull, NE England and Bremen, Germany on the 15/16th September 1931, more than 300 vessels have helped in a voluntary capacity to maintain the Survey.
The CPR Survey is greatly indebted to the Captains and Crews of all the tow ships, their ship owners, management companies, charterers, port staff, stevedores and agents. Their support and participation in our global research is gratefully acknowledged.
Details of the shipping companies and photographs of the current participating vessels are below.
|DI / DJ||
|Z- / ZB / ZC||
Hook of Holland
|LR / V-||
ACL ATLANTIC SEA
|MD||Nova Scotia Shelf|
Publications produced by CPR Survey scientists and collaborating researchers using CPR Survey data.
CPR Survey Staff in bold. *Associate Researchers/ Research Fellows/ PhD Students
Beaugrand, G., A. Conversi, A. Atkinson, J. Cloern, S. Chiba, S. Fonda-Umani, R. R. Kirby, C. H. Greene, E. Goberville, S. A. Otto, P. C. Reid, L. Stemmann and M. Edwards (2019). "Prediction of unprecedented biological shifts in the global ocean." Nature Climate Change 9(3): 237-243.
Beaugrand, G., M. Edwards and P. Hélaouët (2019). "An ecological partition of the Atlantic Ocean and its adjacent seas." Progress in Oceanography 173: 86-102.
Brun, P., K. Stamieszkin, A. W. Visser, P. Licandro, M. R. Payne and T. Kiørboe (2019). "Climate change has altered zooplankton-fuelled carbon export in the North Atlantic." Nature Ecology & Evolution 3(3): 416-423.
Estrella-Martínez, J., B. R. Schöne, R. H. Thurstan, E. Capuzzo, J. D. Scourse and P. G. Butler (2019). "Reconstruction of Atlantic herring (Clupea harengus) recruitment in the North Sea for the past 455 years based on the δ13C from annual shell increments of the ocean quahog (Arctica islandica)." Fish and Fisheries 0(0).
McQuatters-Gollop, A., A. Atkinson, A. Aubert, J. Bedford, M. Best, E. Bresnan, K. Cook, M. Devlin, R. Gowen, D. G. Johns, M. Machairopoulou, A. McKinney, A. Mellor, C. Ostle, C. Scherer and P. Tett (2019). "Plankton lifeforms as a biodiversity indicator for regional-scale assessment of pelagic habitats for policy." Ecological Indicators 101: 913-925.
*Bedford, J., D. G. Johns, S. Greenstreet and A. McQuatters-Gollop (2018). "Plankton as prevailing conditions: a surveillance role for plankton indicators within the Marine Strategy Framework Directive." Marine Policy 89: 109-115.
*Chiba, S., S. Batten, C. S. Martin, S. Ivory, P. Miloslavich and L. V. Weatherdon (2018). "Zooplankton monitoring to contribute towards addressing global biodiversity conservation challenges." Journal of plankton research 40(5): 509-518.
Batten, S. D., D. E. *Raitsos, S. Danielson, R. Hopcroft, K. Coyle and A. McQuatters-Gollop (2018). "Interannual variability in lower trophic levels on the Alaskan Shelf." Deep Sea Research Part II: Topical Studies in Oceanography 147: 58-68.
Batten, S. D., G. T. Ruggerone and I. Ortiz (2018). "Pink salmon induce a trophic cascade in plankton populations in the southern Bering Sea and around the Aleutian Islands." Fisheries Oceanography.
Beaugrand, G. and R. R. Kirby (2018). "How Do Marine Pelagic Species Respond to Climate Change? Theories and Observations." Annual Review of Marine Science 10(1): 169-197.
Bonitz, F. G. W., C. Andersson, T. Trofimova and H. Hátún (2018). "Links between phytoplankton dynamics and shell growth of Arctica islandica on the Faroe Shelf." Journal of Marine Systems 179: 72-87.
Boss, E., A. Waite, F. Muller-Karger, H. Yamazaki, R. Wanninkhof, J. Uitz, S. Thomalla, H. Sosik, B. Sloyan and A. Richardson (2018). "Beyond Chlorophyll Fluorescence: The Time is Right to Expand Biological Measurements in Ocean Observing Programs." Limnology and Oceanography Bulletin.
Burns, F., M. Eaton, D. Hayhow, C. Outhwaite, N. Al Fulaij, T. August, K. Boughey, T. Brereton, A. Brown and D. Bullock (2018). "An assessment of the state of nature in the United Kingdom: A review of findings, methods and impact." Ecological Indicators 94: 226-236.
Di Cesare, A., S. Petrin, D. Fontaneto, C. Losasso, E. M. Eckert, G. Tassistro, A. Borello, A. Ricci, W. H. Wilson and C. Pruzzo (2018). "ddPCR applied on archived Continuous Plankton Recorder samples reveals long‐term occurrence of class 1 integrons and a sulphonamide resistance gene in marine plankton communities." Environmental microbiology reports 10(4): 458-464.
Fowler, A. M., A. M. Jørgensen, J. C. Svendsen, P. I. Macreadie, D. O. Jones, A. R. Boon, D. J. Booth, R. Brabant, E. Callahan and J. T. Claisse (2018). "Environmental benefits of leaving offshore infrastructure in the ocean." Frontiers in Ecology and the Environment.
Hartman, S. E., M. P. Humphreys, C. Kivimäe, E. M. S. Woodward, V. Kitidis, T. McGrath, D. J. Hydes, N. Greenwood, T. Hull, C. Ostle, D. J. Pearce, D. Sivyer, B. M. Stewart, P. Walsham, S. C. Painter, E. McGovern, C. Harris, A. Griffiths, A. Smilenova, J. Clarke, C. Davis, R. Sanders and P. Nightingale (2018). "Seasonality and spatial heterogeneity of the surface ocean carbonate system in the northwest European continental shelf." Progress in Oceanography.
Miloslavich, P., N. J. Bax, S. E. Simmons, E. Klein, W. Appeltans, O. Aburto‐Oropeza, M. Andersen Garcia, S. D. Batten, L. Benedetti‐Cecchi and D. M. Checkley Jr (2018). "Essential ocean variables for global sustained observations of biodiversity and ecosystem changes." Global Change Biology 24(6): 2416-2433.
Record, N. R., R. Ji, F. Maps, Ø. Varpe, J. A. Runge, C. M. Petrik and D. Johns (2018). "Copepod diapause and the biogeography of the marine lipidscape." Journal of Biogeography.
Stern, R., A. *Kraberg, E. Bresnan, W. H. Kooistra, C. Lovejoy, M. Montresor, X. A. G. Morán, F. Not, R. Salas and R. Siano (2018). "Molecular analyses of protists in long-term observation programmes—current status and future perspectives." Journal of Plankton Research 40(5): 519-536.
Turner, J. T. (2019). "Trends in Copepod Studies. Distribution, Biology and Ecology." Uttieri Marco (editor). Nova Science Publishers, New York (USA)
Brown, T., D. D. Kelly, S. Vercauteren, W. H. Wilson and A. Werner (2017). "How Biobanks Are Assessing and Measuring Their Financial Sustainability." Biopreservation and Biobanking 15(1): 65-71.
Capuzzo, E., C. P. Lynam, J. Barry, D. Stephens, R. M. Forster, N. Greenwood, A. McQuatters-Gollop, T. Silva, S. M. van Leeuwen and G. H. Engelhard (2017). "A decline in primary production in the North Sea over 25 years, associated with reductions in zooplankton abundance and fish stock recruitment." Global Change Biology: 1-13.
Chivers, W. J., A. W. Walne and G. C. Hays (2017). "Mismatch between marine plankton range movements and the velocity of climate change." Nature Communications 8(14434).
Clare, D. S., M. Spencer, L. A. Robinson and C. L. Frid (2017). "Explaining ecological shifts: the roles of temperature and primary production in the long‐term dynamics of benthic faunal composition." Oikos 126(8): 1123-1133.
Dees, P., E. Bresnan, A. C. Dale, M. Edwards, D. G. Johns, B. Mouat, C. Whyte and K. Davidson (2017). "Harmful algal blooms in the Eastern North Atlantic Ocean." Proceedings of the National Academy of Sciences 114(46): E9763-E9764.
Dencker, T. S., L. Pecuchet, E. Beukhof, K. Richardson, M. R. Payne and M. Lindegren (2017). "Temporal and spatial differences between taxonomic and trait biodiversity in a large marine ecosystem: Causes and consequences." PLoS ONE 12(12): e0189731.
dos Santos Schmidt, T. C., A. Slotte, J. Kennedy, S. Sundby, A. Johannessen, G. J. Óskarsson, Y. Kurita, N. C. Stenseth and O. S. Kjesbu (2017). "Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well." Proceedings of the National Academy of Sciences 114(10): 2634-2639.
Evans, C., J. Brandsma, D. W. Pond, H. J. Venables, M. P. Meredith, H. J. Witte, S. Stammerjohn, W. H. Wilson, A. Clarke and C. P. Brussaard (2017). "Drivers of interannual variability in virioplankton abundance at the coastal Western Antarctic Peninsula and the potential effects of climate change." Environmental Microbiology 19(2): 740-755.
Everett, J. D., M. E. Baird, P. Buchanan, C. Bulman, C. Davies, R. Downie, C. Griffiths, R. Heneghan, R. J. Kloser, L. Laiolo, A. Lara-Lopez, H. Lozano-Montes, R. J. Matear, F. McEnnulty, B. Robson, W. Rochester, J. Skerratt, J. A. Smith, J. Strzelecki, I. M. Suthers, K. M. Swadling, P. van Ruth and A. J. Richardson (2017). "Modeling What We Sample and Sampling What We Model: Challenges for Zooplankton Model Assessment." Frontiers in Marine Science 4(77).
Fu, C., N. Olsen, N. Taylor, A. Grüss, S. Batten, H. Liu, P. Verley, Y.-J. Shin and H. e. J. Link (2017). "Spatial and temporal dynamics of predator-prey species interactions off western Canada." ICES Journal of Marine Science 74(8): 2107-2119.
Giering, S. L. C., R. Sanders, A. P. Martin, S. A. Henson, J. S. Riley, C. M. Marsay and D. G. Johns (2017). "Particle flux in the oceans: Challenging the steady state assumption." Global Biogeochemical Cycles 31(1): 159-171.
Giron-Nava, A., C. C. James, A. F. Johnson, D. Dannecker, B. Kolody, A. Lee, M. Nagarkar, G. M. Pao, H. Ye and D. G. Johns (2017). "Quantitative argument for long-term ecological monitoring." Marine Ecology Progress Series 572: 269-274.
Howells, R. J., S. J. Burthe, S. O. Green, M. P. Harris, M. A. Newell, A. Butler, D. G. Johns, E. J. Carnell, S. Wanless and F. Daunt (2017). "From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator." Marine Ecology Progress Series 583: 227-242.
Holm, M. W., T. Kiørboe, P. Brun, P. Licandro, R. Almeda and B. W. Hansen (2017). "Resting eggs in free living marine and estuarine copepods." Journal of Plankton Research: 1-14.
Hoppenrath, M., N. Yubuki, R. Stern and B. S. Leander (2017). "Ultrastructure and molecular phylogenetic position of a new marine sand-dwelling dinoflagellate from British Columbia, Canada: Pseudadenoides polypyrenoides sp. nov.(Dinophyceae)." European Journal of Phycology 52(2): 208-224.
Howells, R. J., S. J. Burthe, J. A. Green, M. P. Harris, M. A. Newell, A. Butler, D. G. Johns, E. J. Carnell, S. Wanless and F. Daunt (2017). "From days to decades: short-and long-term variation in environmental conditions affect offspring diet composition of a marine top predator." Marine Ecology Progress Series 583: 227-242.
Lawrence, S. A., S. A. Floge, J. E. Davy, S. K. Davy and W. H. Wilson (2017). "Exploratory analysis of Symbiodinium transcriptomes reveals potential latent infection by large dsDNA viruses." Environmental Microbiology.
Lindegren, M., M. Van Deurs, B. R. MacKenzie, L. Worsoe Clausen, A. Christensen and A. Rindorf (2017). "Productivity and recovery of forage fish under climate change and fishing: North Sea sandeel as a case study." Fisheries Oceanography.
Lynam, C. P., M. Llope, C. Möllmann, P. Helaouët, G. A. Bayliss-Brown and N. C. Stenseth (2017). "Interaction between top-down and bottom-up control in marine food webs." Proceedings of the National Academy of Sciences 114(8): 1952-1957.
Mahadik, G. A., C. Castellani and M. G. *Mazzocchi (2017). "Effect of diatom morphology on the small-scale behavior of the copepod Temora stylifera (Dana, 1849)." Journal of Experimental Marine Biology and Ecology 493(Supplement C): 41-48.
Manno, C., N. Bednaršek, G. A. Tarling, V. L. Peck, S. Comeau, D. Adhikari, D. C. E. Bakker, E. Bauerfeind, A. J. Bergan, M. I. Berning, E. Buitenhuis, A. K. Burridge, M. Chierici, S. Flöter, A. Fransson, J. Gardner, E. L. Howes, N. Keul, K. Kimoto, P. Kohnert, G. L. Lawson, S. Lischka, A. Maas, L. Mekkes, R. L. Oakes, C. Pebody, K. T. C. A. Peijnenburg, M. Seifert, J. Skinner, P. S. Thibodeau, D. Wall-Palmer and P. Ziveri (2017). "Shelled pteropods in peril: Assessing vulnerability in a high CO2 ocean." Earth-Science Reviews 169: 132-145.
McQuatters-Gollop, A., D. G. Johns, E. Bresnan, J. Skinner, I. Rombouts, R. Stern, A. *Aubert, M. Johansen, J. *Bedford and A. Knights (2017). "From microscope to management: The critical value of plankton taxonomy to marine policy and biodiversity conservation." Marine Policy 83: 1-10.
Meyer-Gutbrod, E. L. and C. H. Greene (2017). "Uncertain recovery of the North Atlantic right whale in a changing ocean." Global Change Biology: 1-10.
Middleton, J. E., J. Martínez Martínez, W. H. Wilson and N. R. Record (2017). "Functional dynamics of Emiliania huxleyi virus‐host interactions across multiple spatial scales." Limnology and Oceanography 62(3): 922-933.
Reuman, D. C., L. Zhao, L. W. Sheppard, P. C. Reid and J. E. Cohen (2017). "Synchrony affects Taylor’s law in theory and data." Proceedings of the National Academy of Sciences: 201703593.
Serpetti, N., A. R. Baudron, M. T. Burrows, B. L. Payne, P. Helaouët, P. G. Fernandes and J. J. Heymans (2017). "Impact of ocean warming on sustainable fisheries management informs the Ecosystem Approach to Fisheries." Scientific Reports 7(1): 13438.
Sheppard, L. W., P. C. Reid and D. C. Reuman (2017). "Rapid surrogate testing of wavelet coherences." EPJ Nonlinear Biomedical Physics 5: 1.
Weynberg, K., M. Allen and W. H. Wilson (2017). "Marine Prasinoviruses and Their Tiny Plankton Hosts: A Review." Viruses 9(3): 43.
Wilson, W. H., I. C. Gilg, M. Moniruzzaman, E. K. Field, S. Koren, G. R. LeCleir, J. M. Martínez, N. J. Poulton, B. K. Swan and R. Stepanauskas (2017). "Genomic exploration of individual giant ocean viruses." The ISME Journal 11: 1736-1745.
Technical Reports/ Books
Bresnan, E., C. B. Austin, C. J. A. Campos, K. Davidson, M. Edwards, A. Hall, D. Lees, A. Mckinney, S. Milligang and J. Silkeh (2017). Human Health. MCCIP Science Review 2017.
Castellani, C. and M. Edwards (2017). Marine Plankton: A Practical Guide to Ecology, Methodology, and Taxonomy, Oxford University Press.
Costello, M. J., Z. Basher, L. McLeod, I. Assad, S. Claus, F. Hernandez, J. Mees, L. Vandepitte, M. Yasuhara, H. Gislason, M. Edwards, W. Appeltans, H. Enevoldsen, G. Edgar, P. Miloslavich, S. D. Monte and I. S. Pinto (2016). Chapter 7. Methods for the observation of marine biodiversity In: The GEO Handbook on Biodiversity Observation Networks, Springer International Publishing AG.
Cottier-Cook, E. J., C. Beveridge, J. D. D. Bishop, J. Brodie, P. F. Clark, G. Epstein, S. R. Jenkins, D. G. Johns, J. Loxton, A. MacLeod, C. Maggs, D. Minchin, F. Mineur, J. Sewell and C. A. and Wood (2017). Non-native species. MCCIP Science Review 2017: 47-61.
Edwards, M., D. Broughton, R. Camp, G. Graham, P. Helaouët and R. Stern (2017). AtlantOS plankton report: Based on observations from the Continuous Plankton Recorder Survey. SAHFOS Technical Report. 12: 1-15.
Williamson, P., C. Turley and C. Ostle (2017). Ocean acidification. MCCIP Science Review 2017: 47-61.
Wootton, M., A. C. Fischer, C. Ostle, J. Skinner, D. P. Stevens and D. G. Johns (In Press). Using the Continuous Plankton Recorder to Study the Distribution and Ecology of Marine Pelagic Copepods. New York Nova Science Publishers, Inc.