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  • Marine Record
  • Open Access

Further records of a new diatom species in the English Channel and North Sea: the importance of image-referenced data

Marine Biodiversity Records201811:21

https://doi.org/10.1186/s41200-018-0155-0

  • Received: 18 May 2018
  • Accepted: 19 August 2018
  • Published:

Abstract

Background

In September 2015, an at the time undescribed, autotrophic taxon was discovered in the western English Channel (station L4) and also in the eastern English Channel and Celtic Sea during the Polarstern Cruise PS95 a month later. Subsequent investigations revealed further extensive records (going back to 1992) at stations in the English Channel and the southern North Sea (e.g. Helgoland Roads and Sylt Roads time series stations). Stations in the Northern North Sea have not recorded this distinct taxon. With the available records and crucially, the accompanying image metadata, we are able to chart a clear distribution record with occurrences being restricted to the southern North Sea and English Channel.

Methods

The biological data shown are from Lugol-fixed Utermöhl counts and investigations of live and Formalin-fixed net hauls (20 μm mesh size). All image material shown is available in the online repository Planktonnet (http://planktonnet.awi.de).

Results

We report the distribution, based on geo-referenced image records of an easily recognisable, yet taxonomically uncertain, autotrophic organism.

Conclusions

Distribution patterns of the unidentified autotrophic taxon suggests entry of this taxon into/out of the North Sea via the English Channel. Further investigations providing image-documented information over several years is clearly necessary to clarify its dynamics and ecological characteristics.

Keywords

  • Diatom
  • English Channel
  • North Sea
  • Phytoplankton

Background

Regular phytoplankton monitoring stations in the North Sea and English Channel possess detailed records of the taxa that have been observed there for at least 20 years (Hoppenrath 2004; Widdicombe et al. 2010). These include the Western Channel Observatory‘s stations L4 and E1, stations along the Dutch coast, the Biologische Anstalt Helgoland with its Helgoland Roads long-term phytoplankton time series (located in the German Bight (Wiltshire et al. 2010)) as well as the Wadden Sea station Sylt. Collectively, these time series stations are ideally placed to chart differences in the dynamics and distribution of phytoplankton diversity in the English Channel and North Sea. However, while the taxon lists generated during routine regular observations are extensive, they often comprise a large number of unidentified taxonomic units which are only recorded as size classes or verbatim taxa without assigning an accepted species name to the taxon (as an example the Helgoland Roads taxon list comprises 356 taxa and 250 distinct species). The comparability of the unidentified taxa between different time series stations is usually very limited, especially size classes e.g. unidentified Gymnodiniaceae, can also comprise different species at different times of the year. Increasingly this situation is remedied however by the fact that analysts produce detailed photographic documentation of the taxa (both unidentified and known tax) that are routinely recorded or appear at a site for the first time. Here we report a first distribution record, collated from multiple time series stations and cruises of an organism for which the taxonomic identity is still under discussion but that can be identified reliably on the basis of its morphological characteristics based on photographic material available in a number of research stations.

This organism (referred to as the ‘pringle’) is morphologically distinct, with an undulating parabeloid movement that appears to be typical for this organism. It can be identified reliably and data for this taxon can be analysed jointly between different data sets. Here we review all available data for this taxon to make a first attempt at characterizing it ecologically.

Methods

For this study, records from a large number of ship records and time series stations were collated from live and preserved samples. For counts in the context of routine monitoring programmes, Lugol’s-fixed sample counts are used by each time series represented here. Additional records were obtained from net hauls (20 μm mesh size) and analysed live (L4 and E1, Sylt Roads) or fixed in hexamine-buffered Formalin (Helgoland Roads). Pre-requisite for being included in the study was that at least some records were annotated photographically, as there is no consistently assigned taxonomic name for this taxon yet. Image material obtained for this study was from both Lugol’s-fixed and live material: The characteristics of this distinctive taxon as described below, meant that this diverse material was still usable for documenting the presence of this taxon. All photographic material was taken at a magnification of × 200 and different camera set ups including e.g. Zeiss Axiocam Hrc (Helgoland Roads) and a Leica DFC-450C and Olympus DP25 at L4 and E1). All material used for this study has been archived online in the planktonnet database (http://planktonnet.awi.de//index.php?thematicid=2086). The map of species distribution spread was generated using QGIS 3 (QGIS Development Team 2018, https://qgis.org/en/site/).

Results

Distribution data

The earliest record documented by image material was from a cruise in the English Channel in 1992, where live material was taken by the Dutch monitoring agency within the framework of research on Harmful algal blooms (HAB) (Rademaker and Koeman 1992). The cells were provisionally identified as Campylodiscus, and their typical movement was noted. In 2001, the taxon was spotted again on the monitoring stations along the Dutch coast, and since then, routinely monitored within the Dutch monitoring network (Veen et al. 2015).

In the following years particularly after 2012 this unclassified taxon has been reported by a number of time series stations in the English Channel, southern North Sea and the Dutch Wadden Sea. In September 2015 it was observed at Station L4 in the western English Channel as well as on Polarstern Cruise PS95 (in October and November 2015) at station PS095–001 in the eastern English Channel and PS95–002 in the Celtic Sea. The latter was the only record outside the North Sea or English Channel. (Fig. 1, Table 1). In July 2016 it was also detected at a site near the mouth of the River Elbe (Station Elbe 6 of the Helgoland transect surveys). Further records have since been confirmed from Helgoland Roads and other coastal stations in the German Bight (data for 2017 and 2018 not shown).
Fig. 1
Fig. 1

Map of observational records of the unknown taxon named colloquially ‘the pringle‘, due to its morphology. The occurrence records are colour-coded to show the years in which the organism was observed. Data up to 2016 were included

Table 1

Table detailing occurrences and basic environmental factors at the time of occurrence

 

Date

Station

Latitude

Longitude

2001

13.08.2001

VLISSGBISSVH

51.413

3.566

14.09.2001

HUIBGOT

53.560

6.661

24.09.2001

HAMMOT

51.676

3.849

24.10.2001

GOERE6

51.870

3.872

24.10.2001

WALCRN2

51.549

3.410

24.10.2001

WALCRN70

51.957

2.678

15.11.2001

WALCRN70

51.957

2.678

2002

05.07.2002

GROOTGND

53.305

7.157

15.07.2002

ZUIDOLWOT

53.450

6.514

16.07.2002

HANSWGL

51.437

4.014

16.07.2002

ROTTMPT3

53.566

6.563

16.07.2002

VLISSGBISSVH

51.413

3.566

22.07.2002

HUIBGOT

53.560

6.661

30.07.2002

VLISSGBISSVH

51.413

3.566

01.08.2002

HAMMOT

51.676

3.849

01.08.2002

ZUIDOLWOT

53.450

6.514

02.08.2002

GROOTGND

53.305

7.157

02.08.2002

HUIBGOT

53.560

6.661

13.08.2002

ZUIDOLWOT

53.450

6.514

14.08.2002

HANSWGL

51.437

4.014

14.08.2002

VLISSGBISSVH

51.413

3.566

02.09.2002

ZUIDOLWOT

53.450

6.514

03.09.2002

HUIBGOT

53.560

6.661

18.09.2002

HUIBGOT

53.560

6.661

08.10.2002

HANSWGL

51.437

4.014

18.11.2002

WALCRN70

51.957

2.678

2003

12.03.2003

DANTZGT

53.402

5.727

14.03.2003

GROOTGND

53.305

7.157

11.06.2003

LODSGT

51.516

4.127

16.06.2003

HANSWGL

51.437

4.014

10.07.2003

GROOTGND

53.305

7.157

10.07.2003

HUIBGOT

53.560

6.661

14.07.2003

VLISSGBISSVH

51.413

3.566

03.10.2003

GROOTGND

53.305

7.157

15.12.2003

SCHAARVODDL

51.351

4.251

2004

15.06.2004

WISSKKE

51.602

3.721

06.07.2004

WISSKKE

51.602

3.721

27.07.2004

HUIBGOT

53.560

6.661

28.07.2004

HANSWGL

51.437

4.014

03.08.2004

HAMMOT

51.676

3.849

10.08.2004

HANSWGL

51.437

4.014

25.08.2004

VLISSGBISSVH

51.413

3.566

01.09.2004

HAMMOT

51.676

3.849

01.09.2004

WISSKKE

51.602

3.721

07.09.2004

HANSWGL

51.437

4.014

07.09.2004

VLISSGBISSVH

51.413

3.566

09.09.2004

HUIBGOT

53.560

6.661

14.09.2004

HAMMOT

51.676

3.849

22.09.2004

HANSWGL

51.437

4.014

28.09.2004

HAMMOT

51.676

3.849

28.09.2004

LODSGT

51.516

4.127

28.09.2004

ROTTMPT70

54.118

6.213

28.09.2004

WISSKKE

51.602

3.721

29.09.2004

TERSLG10

53.461

5.100

30.09.2004

WALCRN70

51.957

2.678

07.10.2004

HANSWGL

51.437

4.014

07.10.2004

VLISSGBISSVH

51.413

3.566

12.10.2004

LODSGT

51.516

4.127

12.10.2004

WISSKKE

51.602

3.721

16.11.2004

NOORDWK70

52.586

3.530

2005

27.01.2005

TERSLG10

53.461

5.100

16.08.2005

GROOTGND

53.305

7.157

24.08.2005

HANSWGL

51.437

4.014

27.10.2005

TERSLG100

54.150

4.341

15.11.2005

WALCRN70

51.957

2.678

22.11.2005

TERSLG100

54.150

4.341

13.12.2005

WALCRN70

51.957

2.678

2006

05.07.2006

ZUIDOLWOT

53.450

6.514

06.07.2006

HUIBGOT

53.560

6.661

10.07.2006

VLISSGBISSVH

51.413

3.566

20.07.2006

NOORDWK20

52.342

4.174

26.07.2006

MARSDND

52.983

4.750

17.08.2006

GROOTGND

53.305

7.157

04.09.2006

VLISSGBISSVH

51.413

3.566

18.09.2006

HUIBGOT

53.560

6.661

20.09.2006

HANSWGL

51.437

4.014

20.09.2006

VLISSGBISSVH

51.413

3.566

26.09.2006

WISSKKE

51.602

3.721

03.10.2006

HANSWGL

51.437

4.014

03.10.2006

VLISSGBISSVH

51.413

3.566

11.10.2006

NOORDWK2

52.261

4.405

23.10.2006

LODSGT

51.516

4.127

2007

12.06.2007

BOCHTVWTM

53.3357

6.9439

26.06.2007

HANSWGL

51.437

4.014

27.06.2007

NOORDWK10

52.302

4.301

11.07.2007

HANSWGL

51.437

4.014

11.07.2007

VLISSGBISSVH

51.413

3.566

12.07.2007

BOCHTVWTM

53.3357

6.9439

25.07.2007

GROOTGND

53.305

7.157

25.07.2007

HUIBGOT

53.560

6.661

14.08.2007

DANTZGT

53.402

5.727

21.08.2007

ZUIDOLWOT

53.450

6.514

22.08.2007

BOCHTVWTM

53.3357

6.9439

27.08.2007

DANTZGT

53.402

5.727

13.09.2007

WALCRN2

51.549

3.410

19.09.2007

HANSWGL

51.437

4.014

20.09.2007

ZUIDOLWOT

53.450

6.514

26.09.2007

BOCHTVWTM

53.3357

6.9439

02.10.2007

HANSWGL

51.437

4.014

02.10.2007

VLISSGBISSVH

51.413

3.566

16.10.2007

HANSWGL

51.437

4.014

24.10.2007

TERSLG100

54.150

4.341

24.10.2007

TERSLG135

54.416

4.040

2008

17.03.2008

GROOTGND

53.305

7.157

07.07.2008

SCHAARVODDL

51.351

4.251

09.07.2008

HANSWGL

51.437

4.014

17.07.2008

WALCRN2

51.549

3.410

17.07.2008

WALCRN20

51.659

3.219

21.07.2008

VLISSGBISSVH

51.413

3.566

28.07.2008

ZIJPE

51.646

4.097

31.07.2008

DANTZGT

53.402

5.727

01.08.2008

HUIBGOT

53.560

6.661

05.08.2008

VLISSGBISSVH

51.413

3.566

13.08.2008

HAMMOT

51.676

3.849

13.08.2008

WISSKKE

51.602

3.721

20.08.2008

NOORDWK10

52.302

4.301

21.08.2008

GOERE2

51.8469

3.9155

21.08.2008

GOERE6

51.870

3.872

21.08.2008

WALCRN2

51.549

3.410

27.08.2008

LODSGT

51.516

4.127

29.08.2008

HUIBGOT

53.560

6.661

01.09.2008

VLISSGBISSVH

51.413

3.566

01.09.2008

ZUIDOLWOT

53.450

6.514

09.09.2008

HAMMOT

51.676

3.849

09.09.2008

LODSGT

51.516

4.127

09.09.2008

WISSKKE

51.602

3.721

15.09.2008

VLISSGBISSVH

51.413

3.566

17.09.2008

TERSLG50

53.768

4.766

17.09.2008

WALCRN2

51.549

3.410

28.09.2008

HUIBGOT

53.560

6.661

13.10.2008

VLISSGBISSVH

51.413

3.566

17.11.2008

WALCRN70

51.957

2.678

10.12.2008

TERSLG100

54.150

4.341

12.12.2008

WALCRN70

51.957

2.678

2009

02.06.2009

DANTZGT

53.402

5.727

08.06.2009

HANSWGL

51.437

4.014

23.06.2009

HANSWGL

51.437

4.014

23.06.2009

VLISSGBISSVH

51.413

3.566

02.07.2009

ZUIDOLWOT

53.450

6.514

03.07.2009

GROOTGND

53.305

7.157

06.07.2009

HANSWGL

51.437

4.014

06.07.2009

VLISSGBISSVH

51.413

3.566

17.07.2009

BOCHTVWTM

53.3357

6.9439

17.07.2009

GROOTGND

53.305

7.157

20.07.2009

HANSWGL

51.437

4.014

03.08.2009

HANSWGL

51.437

4.014

03.08.2009

VLISSGBISSVH

51.413

3.566

17.08.2009

VLISSGBISSVH

51.413

3.566

18.08.2009

BOCHTVWTM

53.3357

6.9439

31.08.2009

HANSWGL

51.437

4.014

31.08.2009

VLISSGBISSVH

51.413

3.566

02.09.2009

ROTTMPT70

54.118

6.213

15.09.2009

HANSWGL

51.437

4.014

16.09.2009

WALCRN2

51.549

3.410

22.09.2009

HAMMOT

51.676

3.849

22.09.2009

WISSKKE

51.602

3.721

23.09.2009

TERSLG10

53.461

5.100

14.10.2009

HANSWGL

51.437

4.014

14.10.2009

VLISSGBISSVH

51.413

3.566

14.10.2009

WALCRN20

51.659

3.219

15.10.2009

WALCRN70

51.957

2.678

20.10.2009

HUIBGOT

53.560

6.661

28.10.2009

TERSLG100

54.150

4.341

09.11.2009

NOORDWK2

52.261

4.405

10.11.2009

TERSLG100

54.150

4.341

11.11.2009

NOORDWK10

52.302

4.301

11.11.2009

WALCRN20

51.659

3.219

11.11.2009

WALCRN70

51.957

2.678

12.11.2009

GOERE6

51.870

3.872

12.11.2009

WALCRN2

51.549

3.410

17.11.2009

WISSKKE

51.602

3.721

21.11.2009

MARSDND

52.983

4.750

07.12.2009

NOORDWK70

52.586

3.530

08.12.2009

TERSLG10

53.461

5.100

09.12.2009

GOERE6

51.870

3.872

09.12.2009

WALCRN70

51.957

2.678

17.12.2009

BOOMKDP

53.380

5.167

2010

15.01.2010

DANTZGT

53.402

5.727

21.06.2010

HUIBGOT

53.560

6.661

07.07.2010

BOCHTVWTM

53.3357

6.9439

08.07.2010

HANSWGL

51.437

4.014

13.07.2010

ROTTMPT3

53.566

6.563

21.07.2010

HANSWGL

51.437

4.014

21.07.2010

VLISSGBISSVH

51.413

3.566

03.08.2010

GROOTGND

53.305

7.157

18.08.2010

BOCHTVWTM

53.3357

6.9439

18.08.2010

GROOTGND

53.305

7.157

18.08.2010

HANSWGL

51.437

4.014

18.08.2010

HUIBGOT

53.560

6.661

18.08.2010

VLISSGBISSVH

51.413

3.566

25.08.2010

WALCRN2

51.549

3.410

02.09.2010

HANSWGL

51.437

4.014

02.09.2010

VLISSGBISSVH

51.413

3.566

06.09.2010

HUIBGOT

53.560

6.661

15.09.2010

HANSWGL

51.437

4.014

15.09.2010

VLISSGBISSVH

51.413

3.566

17.09.2010

BOCHTVWTM

53.3357

6.9439

22.09.2010

ROTTMPT70

54.118

6.213

11.10.2010

HANSWGL

51.437

4.014

11.10.2010

HUIBGOT

53.560

6.661

11.10.2010

ROTTMPT3

53.566

6.563

11.10.2010

VLISSGBISSVH

51.413

3.566

13.10.2010

WALCRN70

51.957

2.678

17.11.2010

NOORDWK70

52.586

3.530

17.11.2010

WALCRN70

51.957

2.678

18.11.2010

GOERE2

51.8469

3.9155

18.11.2010

GOERE6

51.870

3.872

23.11.2010

TERSLG50

53.768

4.766

07.12.2010

VLISSGBISSVH

51.413

3.566

2011

27.04.2011

HANSWGL

51.437

4.014

09.06.2011

HANSWGL

51.437

4.014

16.06.2011

VLISSGBISSVH

51.413

3.566

22.06.2011

HANSWGL

51.437

4.014

27.06.2011

BOCHTVWTM

53.3357

6.9439

04.07.2011

HANSWGL

51.437

4.014

04.07.2011

VLISSGBISSVH

51.413

3.566

11.07.2011

BOCHTVWTM

53.3357

6.9439

11.07.2011

HUIBGOT

53.560

6.661

12.07.2011

ROTTMPT3

53.566

6.563

18.07.2011

HANSWGL

51.437

4.014

25.07.2011

BOCHTVWTM

53.3357

6.9439

25.07.2011

GROOTGND

53.305

7.157

25.07.2011

HUIBGOT

53.560

6.661

01.08.2011

HANSWGL

51.437

4.014

01.08.2011

VLISSGBISSVH

51.413

3.566

08.08.2011

BOCHTVWTM

53.3357

6.9439

10.08.2011

WISSKKE

51.602

3.721

16.08.2011

HANSWGL

51.437

4.014

23.08.2011

BOCHTVWTM

53.3357

6.9439

29.08.2011

HANSWGL

51.437

4.014

06.09.2011

BOCHTVWTM

53.3357

6.9439

13.09.2011

HANSWGL

51.437

4.014

13.09.2011

VLISSGBISSVH

51.413

3.566

14.09.2011

GOERE2

51.8469

3.9155

14.09.2011

GOERE6

51.870

3.872

14.09.2011

WALCRN2

51.549

3.410

15.09.2011

NOORDWK2

52.261

4.405

20.09.2011

TERSLG50

53.768

4.766

13.10.2011

SCHAARVODDL

51.351

4.251

07.11.2011

SCHAARVODDL

51.351

4.251

2012

23.04.2012

HANSWGL

51.437

4.014

07.05.2012

VLISSGBISSVH

51.413

3.566

04.06.2012

HANSWGL

51.437

4.014

02.07.2012

HANSWGL

51.437

4.014

11.07.2012

ZIJPE

51.646

4.097

16.07.2012

HANSWGL

51.437

4.014

24.07.2012

WISSKKE

51.602

3.721

29.07.2012

Sylt Roads

55.030

8.460

30.07.2012

BOCHTVWTM

53.3357

6.9439

30.07.2012

HANSWGL

51.437

4.014

30.07.2012

VLISSGBISSVH

51.413

3.566

27.08.2012

NOORDWK2

52.261

4.405

28.08.2012

HANSWGL

51.437

4.014

11.09.2012

BOCHTVWTM

53.3357

6.9439

13.09.2012

HANSWGL

51.437

4.014

13.09.2012

VLISSGBISSVH

51.413

3.566

11.10.2012

HANSWGL

51.437

4.014

11.10.2012

VLISSGBISSVH

51.413

3.566

18.10.2012

NOORDWK10

52.302

4.301

25.10.2012

Sylt Roads

55.030

8.460

2013

20.06.2013

BOCHTVWTM

53.3357

6.9439

25.06.2013

DREISR

51.715

3.999

17.07.2013

BOCHTVWTM

53.3357

6.9439

17.07.2013

HANSWGL

51.437

4.014

31.07.2013

BOCHTVWTM

53.3357

6.9439

31.07.2013

HANSWGL

51.437

4.014

31.07.2013

VLISSGBISSVH

51.413

3.566

14.08.2013

BOCHTVWTM

53.3357

6.9439

14.08.2013

GROOTGND

53.305

7.157

14.08.2013

HUIBGOT

53.560

6.661

15.08.2013

WALCRN2

51.549

3.410

30.08.2013

BOCHTVWTM

53.3357

6.9439

30.08.2013

GROOTGND

53.305

7.157

12.09.2013

VLISSGBISSVH

51.413

3.566

13.09.2013

BOCHTVWTM

53.3357

6.9439

13.09.2013

HUIBGOT

53.560

6.661

2014

26.02.2014

GROOTGND

53.305

7.157

18.03.2014

WALCRN70

51.957

2.678

12.05.2014

BOCHTVWTM

53.3357

6.9439

18.06.2014

HANSWGL

51.437

4.014

07.07.2014

BOCHTVWTM

53.3357

6.9439

15.07.2014

HANSWGL

51.437

4.014

15.07.2014

VLISSGBISSVH

51.413

3.566

22.07.2014

HUIBGOT

53.560

6.661

28.07.2014

HANSWGL

51.437

4.014

28.07.2014

VLISSGBISSVH

51.413

3.566

05.08.2014

HUIBGOT

53.560

6.661

11.08.2014

HANSWGL

51.437

4.014

11.08.2014

VLISSGBISSVH

51.413

3.566

13.08.2014

SCHOUWN10

51.720

3.494

25.08.2014

HANSWGL

51.437

4.014

25.08.2014

VLISSGBISSVH

51.413

3.566

05.09.2014

GROOTGND

53.305

7.157

08.09.2014

HANSWGL

51.437

4.014

08.09.2014

VLISSGBISSVH

51.413

3.566

16.09.2014

WISSKKE

51.602

3.721

18.09.2014

HUIBGOT

53.560

6.661

05.12.2014

Sizewell

52.215

1.627

05.12.2014

Sizewell

52.215

1.627

05.12.2014

Sizewell

52.215

1.634

 

03.05.2015

Helgoland Roads

54.180

7.900

2015

27.05.2015

Sizewell

52.213

1.634

26.07.2015

Sizewell

52.218

1.632

26.07.2015

Sizewell

52.219

1.636

23.09.2015

Sizewell

52.217

1.630

23.09.2015

Sizewell

52.222

1.630

23.09.2015

Sizewell

52.221

1.629

23.09.2015

Sizewell

52.220

1.669

23.09.2015

Sizewell

52.266

1.635

22.10.2015

Sizewell

52.217

1.668

22.10.2015

Sizewell

52.211

1.635

22.10.2015

Sizewell

52.267

1.639

31.10.2015

PS95 Stn 001

50.569

0.311

01.11.2015

PS95 Stn 002

49.035

−5.990

23.11.2015

Sizewell

52.219

1.668

23.11.2015

Sizewell

52.222

1.629

23.11.2015

Sizewell

52.220

1.667

23.11.2015

Sizewell

52.268

1.641

29.11.2015

L4

50.250

−4.210

2016

05.01.2016

L4

50.250

−4.210

13.01.2016

L4

50.250

−4.210

20.01.2016

E1

50.030

−4.360

02.02.2016

L4

50.250

−4.210

18.02.2016

E1

50.030

−4.360

29.02.2016

L4

50.250

−4.210

07.03.2016

L4

50.250

−4.210

07.07.2016

Elbe 6 (F)

53.982

8.405

25.10.2016

E1

50.030

−4.360

01.11.2016

Helgoland Roads

54.180

7.900

01.11.2016

L4

50.250

−4.210

02.11.2016

Helgoland Roads

54.180

7.900

07.11.2016

Helgoland Roads

54.180

7.900

08.11.2016

Helgoland Roads

54.180

7.900

14.11.2016

Helgoland Roads

54.180

7.900

17.11.2016

Helgoland Roads

54.180

7.900

18.11.2016

Helgoland Roads

54.180

7.900

05.12.2016

L4

50.250

−4.210

06.12.2016

E1

50.030

−4.360

12.12.2016

L4

50.250

−4.210

19.12.2016

L4

50.250

−4.210

Earlier anecdotal reports also exist for Helgoland and the Waddensea Station Sylt in northern Germany. However, as these were not documented in sufficient detail (e.g. with image material) they have not been included in the present communication. To our knowledge, this distinctive taxon has not yet been found in the Northern North Sea (e.g. the Scottish Coastal Observatory), Central North Sea or the Baltic (E. Bresnan and M. Johansen pers. comm).

Taxon description

Cells appear variable in symmetry (depending on the orientation of the cell) from oval to wedge-shaped or undulating. They are also clearly pigmented. The nucleus is round and located centrally within the cell. Cells contain several large plate-like chloroplasts, often showing typical squarish inclusion bodies. Cells are motile, with undulating movements and rotation along their long axis. Movement is slow and a flagellum has not been observed. Single or paired cells can occur ‘naked‘ or within what appears to be a mucous envelope. The enveloped stage is also motile, moving inside the mucous envelopes. Particularly the enveloped forms can easily be discerned from photographs and in different fixation methods (compare for instance Fig. 2a (live) and g or h which are Lugol’s fixed).
Fig. 2
Fig. 2

Examples of image material for the ‘pringle’ from different locations: a-b: Helgoland Roads, c: Helgoland transect station Elbe 6, d-f: Station L4 in the English Channel; g-h: PS95 Stn 1, i. Goeree 6, j-l: Lugol-fixed cells from Sizewell (CEFAS), m-n: Sylt Roads. Images a, b, d, e, I, m and n were obtained from live samples; images f, j, k, were obtained from Lugol’s-fixed samples, image c refers to a Formalin-fixed specimen. Images c, f, g, j, k and l show cells encased in a mucilage envelope Image credits: a-c, g-h.: A. Kraberg, d-f: C. Widdicombe, j-l: R. Beckett, i. R. van Wezel, m,n: J. Rick

Taxon identity

The identity of the organism requires clarification. Although clearly motile, flagella have never been observed in cells of any of our samples and the taxon has therefore been referred to as a diatom. Cleaned specimen seem to confirm this view. A genus with a similar paraboloid symmetry is Campylodiscus, but this organism is generally much more heavily ornamented and most species are much larger than the taxon investigated here. Moreover, Campylodiscus is also often considered as a freshwater species (although it can also be found in coastal waters). Upon recording this species for the first time in samples from Dutch monitoring stations in the Southern North Sea, Lugol’s-preserved cells were critically examined using oil immersion microscopy. Fine striation was observed on the surface of the cell, and a central nodule with reinforced structures appearing to be striae is just discernible along the raphe (Fig. 3). Based on those characteristics, and due to the likeness to the drawing in Tomas (1997), this entity was therefore recorded as Membraneis challengeri (Grunow) Paddock in the Dutch data. The taxon has also been regarded similar to Tropidoneis confusa (=Plagiolemma confusum, (Hendey) Paddock) as described by Hendey, 1964.
Fig. 3
Fig. 3

Two cleaned valves mounted in Zrax resin, images 20×/0.7 brightfield microscopy, sample was obtained from the Western Scheldt, July 13th 2015, cell length 42 μm, image source: R. van Wezel

However, the symmetry of the organism does not fit the description of either the symmetry of the basionym of Membraneis challengeri, Navicula challengeri, which is long and straight, nor the shape of Tropidoneis confusa. Finally, neither formal description mentions motility or the mucous envelopes in which cells are frequently found, both in live and preserved samples. During the submission process a new diatom species (Plagiolemma distortum) has been formally described that appears to fit the morphology of the taxon dealt with here (Nezan et al. 2018) and mentioned the mode of locomotion seen in our ‘unidentified’ organism. This type of locomotion appears to be non-typical for most other diatom species for which, a gliding motion along a substrate is more common. However, some diatoms also rotate during the process of forward motion (Cohn and Weitzell Jr. 1996; Edgar and Pickett-Heaps 1983).

Discussion

The identity of this taxon remains unclear. The entity has characteristics that link it to Membraneis challengeri but the motility, its symmetry and its mucous envelope are not found in descriptions of the above taxon, or any of its relatives within the Plagiotropidaceae such as Ephemera but fit with the newly described Plagiolemma distortum (Nezan et al. 2018).

In any case the cells are distinct enough to verify the occurrence of the taxon at a given station as long as good image records are also available so that a reliable distribution record can be assembled. The records collated for this study so far indicate a distribution that is restricted to the Southern North Sea and English Channel (based on 342 records) with occasional records from the Celtic Sea to the west of the English Channel. Through communication within the ICES expert group WGPME it was also confirmed that neither time series in the Baltic or the Coastal Scottish observatory have yet detected this species (M. Johansen, E. Bresnan pers. comm).

Considering only the years 2015 and 2016 (the best documented years in terms of the availability of image material) it would be tempting to consider this taxon as an Atlantic species that is advected into the North Sea only occasionally. For benthic neophytes reaching the island of Helgoland the English Channel was also suggested as an important immigration pathway by Franke and Gutow (2004) (see also: (Minchin et al. 2013)). In contrast, the earlier records would indicate a more coastal/brackish preference and therefore different direction of extending its range (see particularly data from the Dutch Delta and Wadden Sea, a site close to the Elbe estuary (Site Elbe 6 in Table 1) and recently also in the harbour of Antwerp. This is also supported by the fact that during the periods of occurrence other benthic or ptychopelagic species (the latter defined as species that have a predominantly benthic mode of life but can appear in the plankton e.g. after extreme weather events) were also often present including Paralia sulcata, Actinocyclus and Odontella species, (data not shown but see Fig. 1d). Assuming that the taxon considered here is indeed Plagiolemma distortum, this would also fit with the observations by Nezan et al. (2018) who considered this taxon as potentially benthic or epilithic. But clearly, more sustained observations with a good spatial coverage, appropriate image metadata and preferentially sequence data, are necessary to reveal in more detail the taxonomic position and ecology of this enigmatic species.

Conclusion

The number of actual distributional records is still very small, spread over a number of years and more data are therefore required to confirm the origin and main direction of spread of this taxon from the North Atlantic into the North Sea via the English Channel (or vice versa extended its range from more brackish habitats into the open sea). It is also unclear whether first records were really first records or mark the point where an unidentified cell was first recorded as a distinct taxon in a given time series. Importantly, beginning to chart the progress of this species was possible because of the large number of available high-quality records documented with image material. Adhering to a strict protocol for recording new or unidentified taxa photographically and with appropriate taxonomic and biogeographic meta data is therefore strongly recommended for any time series programme routinely determining phytoplankton abundance (Zingone et al. 2015) both to increase the taxonomic consistency and resolution within time series but also to facilitate more detailed comparisons between data sets.

Abbreviations

AWI: 

Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research

GIS: 

Geographic information system

HAB: 

Harmful algal blooms

ICES: 

International Council for the exploration of the seas

NERC: 

UK Natural Environment Research Council

TWN: 

Taxon management the Netherlands

WGPME: 

Working group on phytoplankton and microbial ecology

Declarations

Acknowledgements

AK was funded by the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research. CW and PR were funded under the UK’s Natural Environment Research Council (NERC) National Capability programme. We also acknowledge the International Council for the Exploration of the Seas (ICES) for supporting the Working group on Phytoplankton and Microbial Ecology (WGPME). The manuscript was planned and its first version written during the annual WGPME meeting in Reikjavik 2017. We thank Silvia Peters at the Biologische Anstalt Helgoland (AWI), Malte Elbrächter and Hanne Halliger at the Waddenseastation Sylt and all the past and present analysts of the time-series stations referred to in this study. We further thank Dr. Dario Fiorentino of the Helmholtz Institute for Functional Marine Biodiversity (HIFMB) for the production of the distribution map. We also thank two anonymous reviewers for their valuable comments.

Funding

UK Natural Environment Research Council (NERC) National Capability programme.

Availability of data and materials

Image material is published in the open access data base Planktonnet (http://planktonnet.awi.de). The geolocations are already freely available. No other data were used.

Authors’ contributions

The manuscript arose from discussions between AK and CW. AK wrote the first draft. All authors contributed image material from their time series station and contributed to the discussion of the identity of the taxon. Final editing was done by AK with contributions from RW, RB and CW. All authors read and approved the final manuscript.

Ethics approval and consent to participate

NA

Consent for publication

All authors have given consent to publishing the MS.

Competing interests

The authors declare that they have no competing interests.

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Authors’ Affiliations

(1)
Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Biologische Anstalt Helgoland, Kurpromenade 201, 27498 Helgoland, Germany
(2)
Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth, PL1 3DH, UK
(3)
Centre for the Environment, Fisheries and Aquaculture Science, Lowestoft, UK
(4)
Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Wattenmeerstation Sylt, Hafenstraße 43, 25992 List/Sylt, Germany
(5)
Rijkswaterstaat, Ministry of Infrastructure and Watermanagement, Lelystad, The Netherlands

References

  1. Cohn SA, Weitzell RE Jr. Ecological considerations of diatom motility. I. Characterization of motility and adhesion in four diatom species. J Anim Ecol. 1996;32 https://doi.org/10.1111/j.0022-3646.1996.00928.x.
  2. Edgar LA, Pickett-Heaps JD. The mechanisms of diatom locomotion. I. An ultrastructural study of the motility apparatus. Proceedings of the Royal Society London. 1983;218:331–43.View ArticleGoogle Scholar
  3. Franke H-D, Gutow L. Long-term changes in the macrozoobenthos around the rocky island of Helgoland (German bight, North Sea). Helgol Mar Res. 2004;58:303–10.View ArticleGoogle Scholar
  4. Hoppenrath M. A revised checklist of planktonic diatoms and dinoflagellates from Helgoland (North Sea, German bight). Helgol Mar Res. 2004;58:243–51.View ArticleGoogle Scholar
  5. Minchin D, Cook EJ, Clark PF. Alien species in British brackish and marine waters. Aquat Invasions. 2013;8:3–19.View ArticleGoogle Scholar
  6. Nezan E, Bilien G, Boulben S, Mertens KN, Chomerat N (2018) Desription and phylogenetic position of Plagiolemma distortum sp. nov., a new raphid diatom (Bacillariophyceae) from French coastal waters Diatom Research https://www.tandfonline.com/doi/full/10.1080/0269249X.2018.1468359
  7. Rademaker M, Koeman R (1992) Determinatie fytoplankton in het Nederlandse deel van de Noordzee en het kanaal project algenbloei 1992. 23pp. Bureau Tripos, Amsterdam.Google Scholar
  8. Veen A, Hof CHJ, Kouwets FAC, Berkhout T (2015) Rijkswaterstaat Waterdienst, Informatiehuis Water [Taxa Watermanagement the Netherlands (TWN)] http://ipt.nlbif.nl/ipt/resource?r=checklist-twn, consulted: 14.5.2018.
  9. Widdicombe C,E, Eloire D, Harbour D, Harris RP, Somerfield PJ. Long-term phytoplankton community dynamics in the western English Channel. J Plankton Res. 2010;32:643–55.View ArticleGoogle Scholar
  10. Wiltshire KH, Kraberg A, Bartsch I, Boersma M, Franke HD, Freund J, Gebühr C, Gerdts G, Stockmann K, Wichels A (2010) Helgoland Roads: 45 years of change in the North Sea Estuaries and Coasts https://doi.org/10.1007/s12237-009-9228-y.
  11. Zingone A, Harrison PJ, Kraberg AC, Lehtinen S, McQuatters-Gollop A, O'Brien T, Sun J, Jakobsen HH. Increasing the quality, comprability and accessibility of phytoplankton species composition time-series data. Estuar Coast Shelf Sci. 2015;162:151–60.View ArticleGoogle Scholar

Copyright

© The Author(s) 2018

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