Species composition and community structure of phototrophic protists and cyanobacteria in phytoplankton of the Guinea-Bissau region, central-eastern Atlantic Ocean Текст научной статьи по специальности «Биологические науки»

Protistology 18 (2): 130-142 (2024) | doi:10.21685/1680-0826-2024-18-2-4 Pl'OtiStOlO&y

Original article

Species composition and community structure of phototrophic protists and cyanobacteria in phytoplankton of the Guinea-Bissau region, central-eastern Atlantic Ocean

Nikolai P. Diushkov1, Irena V. Telesh2* and Elena N. Naumenko3

1 Atlantic branch of the Russian Federal Research Institute of Fisheries and Oceanography "VNIRO"("AtlantNIRO"), Kaliningrad, Russia

2 Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia

3 Kaliningrad State Technical University (FSBEIHPE "KSTU"), Kaliningrad, Russia

| Submitted April 7, 2024 | Accepted May 21, 2024 |

Summary

The analysis of species composition and quantitative characteristics of phototrophic unicellular eukaryotes (protists) and prokaryotes (cyanobacteria) of phytoplankton communities in the Guinea-Bissau zone of the central-eastern Atlantic Ocean during the cold season of 2013 was carried out for the first time. In total, 189 phytoplankton species from seven taxonomic divisions were identified; the majority of permanent species was represented by dinoflagellates. Based on the results of multivariate statistical analysis, three phytoplankton communities were distinguished in the study region: neritic, secondary ecotone type, and distant neritic community. The highest phytoplankton biomass values were recorded in the neritic community in the shelf zone and were confined to freshened, nutrients-saturated upwelling waters. The average values of the phytoplankton abundance and biomass in the Guinea-Bissau coastal area corresponded to the mesotrophic conditions and were nearly thrice as high as in the Moroccan zone.

Key words: phytoplankton, community characteristics, spatial distribution, dinoflagellates, diatoms, cyanobacteria

Introduction

The waters off the coast of the Guinea-Bissau Exclusive Economic Zone (EEZ) in the central-eastern Atlantic Ocean are part of the largest up-welling ecosystem, the Canary Current (Ibe and

https://doi.org/10.21685/1680-0826-2024-18-2-4

© 2024 The Author(s)

Protistology © 2024 Protozoological Society Affiliated with RAS

Sherman, 2002). This area is a commercially important fishery region for many countries, including Russia. The Guinea-Bissau region covers the border zone between two large marine ecosystems. In some publications, the authors describe this area as the southern border of the large upwelling ecosystem of

Corresponding author: Irena V. Telesh. Zoological Institute of the Russian Academy of Sciences, Universitetskaya Emb. 1, 199034 St. Petersburg, Russia; Irena.Telesh@zin.ru

the Canary Current (Canary Current Large Marine Ecosystem, CCLME), extending from the Strait of Gibraltar (about 36°N and 5°W) south to the Bijagos Islands in the southern Guinea-Bissau (around 11°N and 16°W) (Valdes and Deniz-Gonzalez, 2015). Other authors associate the waters ofGuinea-Bissau (including the Bijagos Islands and a wide area ofthe adjacent continental shelf) as the northern part ofthe Guinea Current ecosystem extending from GuineaBissau 12°N in the north to Angola 6°S in the south (Honey and Elvin, 2013). However, in both cases, these are the waters of Guinea-Bissau that have completely unique hydrological conditions, created under the influence of the powerful runoff of continental waters carried out by large rivers such as the Zheba, Kashou, Corubal and Balana. In the Canary Upwelling and Guinea Current ecosystems, the hydrological regime is determined by the intensity of coastal upwelling, as well as the Canary and Guinea Currents, and has a pronounced seasonal variability (Productivity patterns..., 2010; Valdes and Deniz-Gonzalez, 2015). Highly productive areas (where phytoplankton develops abundantly) within the large ecosystems mentioned above are formed only in the regions of upwelling of deep-see waters, and their existence usually depends on the intensity and duration of upwelling as the main source of nutrients that are required for the phytoplankton development (Demarch, 2009). The formation of highly productive zones is also a seasonal event. However, the Guinea-Bissau zone remains highly productive throughout the year, since the bulk of the nutrients necessary for the growth of phytoplankton are carried out with the continental runoff. This is a unique feature of the area along the coast of West Africa, from Morocco to Angola.

Despite its uniqueness, there is only a limited number of publications on phytoplankton studies in this area. Most often, various sources do not consider the waters of Guinea-Bissau as a separate region but provide a description of this area (northern for the Guinea Current ecosystem and southern for the Canary Current ecosystem) within the framework of the analysis of those two major systems. Therefore, it is difficult to find a taxonomic description of the phytoplankton of Guinea-Bissau in the present-day literature. The bulk of modern phytoplankton studies usually contain characteristics of the algal quantitative distribution by relying only on available satellite mapping data (Fraga, 1974; Nixon and Thomas, 2001; Demarcq et al., 2003; Productivity patterns..., 2010; Valdes and Deniz-Gonzalez, 2015). This approach gives a general idea of the

Fig. 1. Location ofphytoplankton sampling stations (numbers 1—33) in the waters ofthe Guinea-Bissau EEZ in January 2013. Solid lines indicate isobaths (depths shown in meters).

spatial and seasonal distribution of phytoplankton and makes it possible to assess the productivity ofthe area, although without tackling the analysis of the phytoplankton species composition, identification of dominant groups and species, structure and distribution of communities. Thus, phytoplankton as the primary trophic link in the ecosystem of the Guinea-Bissau region has long remained practically unstudied, and the information on its species composition and structure of communities is scarce.

A research cruise was carried out in the winter of 2013 to evaluate the reserves of pelagic fish species and assess their habitats in the GuineaBissau EEZ. The aim of this study was to unveil the species composition of phototrophic protists and cyanobacteria, and disclose the structure of phytoplankton communities in the waters of the Guinea-Bissau EEZ.

Material and methods

The material for the study consists of a set of phytoplankton samples collected in the 59th voyage of the scientific research vessel "Atlantida" in the fishing area of the Guinea-Bissau EEZ from 9°58' to 12°00' N in January 2-10, 2013. The 33 sampling stations were located above the depths of 25-500 m at several parallel latitude-oriented sections spaced apart from each other at a distance of about 15 miles (Fig. 1). Altogether, 53 phytoplankton samples were collected from the water layers 0 m

(surface) and 25 m. Samples were taken with a Niskin-type bathometer (volume 1 L) installed at the oceanological complex Sea Bird Electronics.

The samples were preserved by Lugol's solution with the addition of glacial acetic acid and concentrated by the sedimentation method in the laboratory (Fedorov, 1979; Abakumov, 1983; Radchenko et al., 2010). Samples processing was performed in a Nageotte chamber with a volume of 0.01 mL using an Olympus CH-2 microscope with 400-1000x magnification. Species were identified using regional and general keys and atlases of marine and freshwater phytoplankton (Carmelo, 1997; Botes, 2001; AI-Kandari et al., 2009). Phytoplankton biomass was calculated using the geometric similarity method. Based on the contribution of the species to the total phytoplankton biomass, dominant species (>10%) and subdominants (5-10%) were distinguished (Abakumov, 1983; Radchenko et al., 2010).

For characterising the frequency of occurrence of the taxa, the following scale was used: permanent taxa - with occurrence at more than 50% of all stations, secondary - found at 25-50% of stations, sporadic - registered at less than 25% of stations (Bakanov, 2005). Shannon species diversity and Pielou evenness indices were calculated using the commonly accepted methods (Odum, 1986).

Statistical data were processed with standard methods in the Microsoft Office Excel, PRIMER® 6, and Surfer 10 software package.

Results

In the Guinea-Bissau EEZ, 189 phytoplankton species including autotrophic and mixotrophic protists and cyanobacteria from seven taxonomic divisions were identified (Table 1).

In terms of the number of species, diatoms (56%) and dinoflagellates (34%) predominated; a relatively small number of species represented the remaining divisions (Fig. 2). Only 13 species were found in more than a half of the studied water area and could be classified as permanent; the most common were Protodinium simplex (82%) and Scrippsiella acuminata (82%) (Table 2). Twenty-two phytoplankters were classified as secondary species occurring at 25-50% of the stations. Most algal species were found less frequently and were considered as sporadic in the study region.

In the shelf zone, in areas of desalination above the depths of less than 50 m, representatives of

I CYANOBACTERIA 1_3%

zjCHLOROPHYTA 4%

EUGLENOPHYTA

2%

HETEROKONTOPHYTA

56%

Fig. 2. l axonomic structure ot phytoplankton in the

waters of the Guinea-Bissau EEZ in January 2013.

freshwater blue-green algae (cyanobacteria) Anaba-ena oscillarioides and Chamaecalyx swirenkoi, as well as green algae Tetraedron minimum and Closterium gracile were registered. The overall phytoplankton abundance was 425 ± 88 x 103 cells/L, biomass 1.08 ± 0.38 mg/L.

The spatial distribution of phytoplankton was uneven; in the shelf area, abundance and biomass reached 2.1 million cells/L and 10.69 mg/L, respectively, and towards the open ocean their values decreased to 30x103 cells/L and 0.01 mg/L (Fig. 3).

Representatives of blue-green algae (55%) and diatoms (29%) predominated in numbers. High abundance values of over 2 million cells/L were recorded in the north of the region due to the massive development of the blue-greens from the genus Trichodesmium. The highest biomass was produced by the heterokont algae (86%). One species of diatoms was dominant, Trieres chinensis (19%). Subdominants were represented by four species of the Heterokontophyta: Rhizosolenia imb-ricata - 10%; Eupyxidicula turris - 9%; Meuniera membranacea — 8%; Lauderia annulata — 7%. The maximum biomass of phytoplankton recorded in the shelf zone was spatially confined to slightly desalinated (33.4 %o) and nutrients-saturated coastal waters with phosphate concentration up to 0.3 ^g/L.

Based on multivariate statistical analysis, three phytoplankton communities were distinguished in the Guinea-Bissau EEZ (Fig. 4, Table 3).

The first community was distributed above the depths of 20-100 m; it was extended along the coast and confined to shelf waters desalinated by the continental runoff (Fig. 5). It was characterised by the highest abundance and biomass of phytoplankton (Table 3). In terms of biomass, the community was dominated by the diatoms (T. chinensis, S. turris, M. membranacea, R.. imbricata) and L. annulata (Fig.

Table 1. Species composition of phytoplankton in the waters of Guinea-Bissau, central-eastern Atlantic Ocean. The synonymy of species was checked using the resource: https://www.algaebase.org.

Order Family Species

Phylum CYANOBACTERIA

Class Cyanophyceae

Nostocales Aphanizomenonaceae Anabaena oscillarioides Bory ex Bornet & Flahault 1886

Chroococcales Microcystaceae Aphanocapsa marina Hansgirg, 1890

Oscillatoriales Microcoleaceae Blennothrix glutinosa (Gomont ex Gomont) Anagnostidis & Komarek, 2001

Trichodesmium erythraeum Ehrenberg ex Gomont, 1892

Pleurocapsales Hyellaceae Chamaecalyx swirenkoi (Sirsov) Komarek & Anagnostidis, 1986

Phylum CHLOROPHYTA

Class Trebouxiophyceae

Trebouxiales Trebouxiaceae Asterochloris woessiae Skaloud & Peksa 2015

Chlorellales Chlorellaceae Closteriopsis longissima (Lemmermann) Lemmermann 1899

Chlorellales Chlorellaceae Golenkiniopsis longispina (Korshikov) Korshikov 1953

Class Chlorophyceae

Sphaeropleales Scenedesmaceae Desmodesmus spinosus (Chodat) E.Hegewald 2000

Sphaeropleales Selenastraceae Monoraphidium komarkovae Nygaard 1979

Sphaeropleales Hydrodictyaceae Tetraedron minimum (A.Braun) Hansgirg1889

Class Ulvophyceae

Ulvophyceae Ulvophyceae Blastophysa rhizopus Reinke 1889

Phylum CHAROPHYTA

Class Zygnematophyceae

Desmidiales Closteriaceae Closterium gracile Brebisson ex Ralfs 1848

Phylum EUGLENOPHYTA

Class Euglenophyceae

Euglenales Euglenaceae Euglena sp.

Euglenales Euglenaceae Trachelomonas volvocina (Ehrenberg) Ehrenberg 1834

Euglenales Euglenaceae Trachelomonas sp.

Phylum HETEROKONTOPHYTA

Class Bacillariophyceae

Achnanthales Achnanthaceae Achnanthes brevipes Agardh 1824

Achnanthes armillaris (O.F.Müller) Guiry 2019

Naviculales Amphipleuraceae Halamphora hyalina (Kützing) Rimet & R.Jahn 2018

Thalassiophysales Catenulaceae Amphora ovalis (Kützing) Kützing 1844

Rhaphoneidales Asterionellopsidaceae Asterionellopsis glacialis (Castracane) Round 1990

Grammatophoraceae Grammatophora marina (Lyngbye) Kützing 1844

Bacillariales Bacillariaceae Cylindrotheca closterium (Ehrenberg) Reimann & J.C.Lewin 1964

Hantzschia amphioxys (Ehrenberg) Grunow 1880

Nitzschia bicapitata Cleve 1901

Nitzschia longissima (Brebisson ex Kützing) Grunow 1862

Nitzschia rectilonga Takano 1983

Psammodictyon panduriforme (Gregory) Mann 1990

Pseudo-nitzschia subpacifica (Halse) Halse 1993

Pseudo-nitzschia australis Frenguelli 1939

Table 1. Continuation.

Bacillariales Bacillariaceae Pseudo-nitzschia delicatissima (Cleve) Heiden 1928

Pseudo-nitzschia heimii Manguin 1957

Pseudo-nitzschia multiseries (Hasle) Hasle 1995

Pseudo-nitzschia multistriata (H.Takano) H.Takano 1995

Pseudo-nitzschia pseudodelicatissima (Hasle) Hasle 1993

Pseudo-nitzschia pungens (Grunow ex Cleve) Hasle 1993

Pseudo-nitzschia seriata (Cleve) Peragallo 1899

Tryblionella compressa (Bailey) Poulin 1990

Naviculales Diploneidaceae Diploneis bombus (Ehrenberg) Ehrenberg 1853

Diploneis crabro (Ehrenberg) Ehrenberg 1854

Luticola ventricosa (Kützing) D.G.Mann 1990

Naviculaceae Navicula mollis (W.Smith) Cleve 1895

Plagiotropidaceae Meuniera membranacea (Cleve) P.C.Silva 1996

Pleurosigmataceae Pleurosigma directum Grunow 1880

Pleurosigma elongatum W.Smith 1852

Pleurosigma normanii Ralfs 1861

Hemiaulales Hemiaulaceae Neomoelleria cornuta (Cleve) S.Blanco & C.E.Wetzel 2016

Licmophorales Licmophoraceae Licmophora ehrenbergii (Kützing) Grunow 1867

Surirellales Surirellaceae Plagiodiscus martensianus Grunow & Eulenstein 1867

Striatella unipunctata (Lyngbye) C.Agardh 1832

Thalassionematales Thalassionemataceae Thalassionema javanicum (Grunow) G.R.Hasle apud G.R. Hasle & E.E. Syversten 1996

Thalassionema nitzschioides (Grunow) Mereschkowsky 1902

Thalassionema pseudonitzschioides (G.Schuette & H.Schrader) G.R.Hasle 1996

Shionodiscus oestrupii (Ostenfeld) A.J.Alverson, S.-H.Kang & E.C.Theriot 2006

Thalassionematales Thalassionematacea Thalassiothrix longissima Cleve & Grunow 1880

Class Dictyochophyceae

Dictyochales Dictyochaceae Dictyocha fibula Ehrenberg 1839

Octactis speculum (Ehrenberg) F.H.Chang, J.M.Grieve & .E.Sutherland 2017

Dictyocha crux Ehrenberg 1841

Stephanocha rotunda (Stöhr) K.McCartney & R.W.Jordan 2015

Class Mediophyceae

Anaulales Anaulaceae Terpsinoe musica Ehrenberg 1843

Eupodiscales Parodontellaceae Trieres chinensis (Greville) Ashworth & E.C.Theriot 2013

Odontellaceae Amphitetras antediluviana Ehrenberg 1840

Chaetocerotales Chaetocerotaceae Bacteriastrum elongatum Cleve 1897

Bacteriastrum furcatum Shadbolt 1853

Bacteriastrum hyalinum Lauder 1864

Chaetoceros affinis Lauder 1864

Chaetoceros convolutus Castracane 1886

Chaetoceros compressus Lauder 1864

Chaetoceros danicus Cleve 1889

Chaetoceros decipiens Cleve 1873

Chaetoceros densus (Cleve) Cleve 1899

Chaetoceros didymus Ehrenberg 1845

Table 1. Continuation.

Chaetoceros eibenii Grunow 1882

Chaetocerotaceae Chaetoceros peruvianus Brightwell 1856

Chaetocerotales Chaetoceros socialis Lauder 1864

Chaetoceros curvisetus Cleve 1889

Leptocylindraceae Leptocylindrus danicus Cleve 1889

Leptocylindrus minimus Gran 1915

Biddu lphia les Biddulphiaceae Biddulphia biddulphiana (J.E.Smith) Boyer 1900

Climacodium frauenfeldianum Grunow 1868

Lithodesmiales Lithodesmiaceae Ditylum brightwellii (West) Grunow 1885

Helicotheca tamesis (Shrubsole) Ricard 1987

Eucampia zodiacus Ehrenberg 1839

Hemiaulales Hemiaulaceae Hemiaulus hauckii Grunow ex Van Heurck 1882

Hemiaulus proteus Heiberg1963

Hemiaulus chinensis Greville 1865

Lauderiaceae Lauderia annulata Cleve 1873

Thalassiosirales Skeletonemataceae Skeletonema costatum (Greville) Cleve 1873

Thalassiosiraceae Shionodiscus oestrupii (Ostenfeld) A.J.Alverson, S.-H.Kang & E.C.Theriot 2006

Class Coscinodiscophyceae

Hemidiscaceae Actinocyclus octonarius Ehrenberg 1837

Coscinodiscales Coscinodiscaceae Coscinodiscus curvatulus Grunow 1878

Corethrales Corethraceae Corethron pennatum (Grunow) Ostenfeld 1909

Dactyliosolen fragilissimus (Bergon) Hasle 1996

Guinardia cylindrus (Cleve) Hasle 1996

Guinardia delicatula (Cleve) Hasle 1997

Guinardia flaccida (Castracane) Peragallo 1892

Guinardia striata (Stolterfoth) Hasle 1996

Dactyliosolen mediterraneus (H.Peragallo) H.Peragallo 1892

Neocalyptrella robusta (G.Norman ex Ralfs) Hernandez-Becerril & Meave 1997

Rhizosolenia acicularis B.G.Sundström 1986

Rhizosolenia antennata (Ehrenberg) Brown 1920

Rhizosoleniales Rhizosoleniaceae Rhizosolenia bergonii H.Peragallo 1892

Pseudosolenia calcar-avis (Schultze) B.G.Sundström 1986

Rhizosolenia curvata Zacharias 1905

Rhizosolenia hebetata f. semispina (Hensen) Gran 1905

Rhizosolenia hyalina Ostenfeld 1901

Rhizosolenia imbricata Brightwell 1858

Rhizosolenia polydactyla Castracane 1886

Rhizosolenia simplex G.Karsten 1905

Rhizosolenia styliformis T.Brightwell 1858

Sundstroemia setigera (Brightwell) Medlin 2021

Sundstroemia pungens (Cleve-Euler) Medlin, Lundholm, Boonprakob & Moestrup 2021

Hyalodiscaceae Hyalodiscus radiates (O'Meara) Grunow 1879

Melosirales Podosira stelligera (Bailey) Mann 1907

Grammatophoraceae Grammatophora marina (Lyngbye) Kützing 1844

Table 1. Continuation.

Paraliales Paraliaceae Paralia sulcata (Ehrenberg) Cleve 1873

Probosciales Probosciaceae Proboscia alata (Brightwell) Sundström 1986

Stellarimales Gossleriellaceae Gossleriella tropica Schütt 1893

Stephanopyxales Stephanopyxidaceae Eupyxidicula turris (Greville) S.Blanco & C.E.Wetzel 2016

Phylum DINOFLAGELLATA

Class Dinophyceae

Amphidiniales Amphidiniaceae Amphidinium sphenoides Wulff 1919

Gonyaulacales Pyrocystaceae Alexandrium catenella (Whedon & Kofoid) Balech 1985

Amphidomataceae Azadinium spinosum Elbrächter & Tillmann 2009

Ceratiaceae Tripos muelleri Bory 1826

Lingulodiniaceae Lingulodinium polyedra(F.Stein) J.D.Dodge 1989

Lingulodinium polyedra (F.Stein) J.D.Dodge 1989

Protoceratiaceae Protoceratium reticulatum (Claparede & Lachmann) Bütschli 1885

Pyrocystaceae Pyrocystis lunula (F.Schütt) F.Schütt 1896

Dinophysales Dinophysaceae Dinophysis acuminata Claparede & Lachmann 1859

Dinophysis acuta Ehrenberg 1839

Dinophysis caudata Kent 1881

Dinophysis fortii Pavillard 1924

Dinophysis infundibulum J.Schiller 1928

Dinophysis odiosa (Pavillard) Tai & Skogsberg 1934

Dinophysis rudgei G.Murray & Whitting 1899

Oxyphysaceae Phalacroma oxytoxoides (Kofoid) F.Gomez, P.Lopez-Garcia & D.Moreira 2011

Gymnodiniales Gymnodiniales Levanderina fissa (Levander) Moestrup, Hakanen, Gert Hansen, Daugbjerg & M.Ellegaard 2014

Dissodinium pseudocalani (Gonnert) Drebes ex Elbrachter & Drebes 1978

Lebouridinium glaucum (Lebour) F.Gómez, H.Takayam, D.Moreira & P.López-García 2016

Gymnodininaceae Gymnodinium catenatum H.W.Graham 1943

Gyrodiniaceae Gyrodinium spirale (Bergh) Kofoid & Swezy 1921

Kareniaceae Karenia mikimotoi (Miyake & Kominami ex Oda) Gert Hansen & Moestrup 2000

Gonyaulacales Gambierdiscoideae Gambierdiscus australes Chinain & M.A.Faust 1999

Gonyaulacaceae Gonyaulax spinifera (Claparede & Lachmann) Diesing 1866

Ceratiaceae Tripos lineatus (Ehrenberg) F.Gómez 2021

Tripos candelabrum (Ehrenberg) F.Gómez 2013

Tripos gracilis (Pavillard) F.Gómez 2013

Tripos furca (Ehrenberg) F.Gómez 2013

Tripos fusus (Ehrenberg) F.Gómez 2013

Tripos longipes (Bailey) F.Gómez 2021

Tripos macroceros (Ehrenberg) Hallegraeff & Huisman 2020

Tripos muelleri Bory 1826

Tripos pentagonus (Gourret) F.Gómez 2021

Tripos symmetricus (Pavillard) F.Gómez 2021

Tripos trichoceros (Ehrenberg) Gómez 2013

Table 1. Continuation.

Peridiniales Heterocapsaceae Heterocapsa circularisquama Horiguchi 1995

Ensiculiferaceae Pentapharsodinium dalei Indelicato & A.R.Loeblich 1986

Protoperidiniaceae Archaeperidinium minutum (Kofoid) Jorgensen 1912

Preperidinium meunieri (Pavillard) Elbrächter 1993

Protoperidinium areolatum (Peters) Balech 1974

Protoperidinium bipes (Paulsen) Balech 1974

Protoperidinium compressum (T.H.Abe) Balech 1974

Protoperidinium denticulatum (Gran & Braarud) Balech 1974

Protoperidinium depressum (Bailey) Balech 1974

Protoperidinium diabolus (Cleve) Balech 1974

Protoperidinium pellucidum Bergh 1882

Protoperidinium pentagonum (Gran) Balech 1974

Protoperidinium punctulatum (Paulsen) Balech 1974

Protoperidinium pyriforme (Paulsen) Balech 1974

Protoperidinium steinii (Jorgensen) Balech 1974

Protoperidinium tuba (J.Schiller) Balech 1974

Kryptoperidiniaceae Blixaea quinquecornis (T.H.Abe) Gottschling 2017

Prorocentrales Prorocentraceae Prorocentrum cordatum (Ostenfeld) J.D.Dodge 1976

Prorocentrum emarginatum Y.Fukuyo 1981

Prorocentrum gracile F.Schütt 1895

Prorocentrum lima (Ehrenberg) F.Stein 1878

Prorocentrum mexicanum Osorio-Tafall 1942

Prorocentrum micans Ehrenberg 1834

Prorocentrum rostratum F.Stein 1883

Prorocentrum triestinum J.Schiller 1918

Suessiales Suessiaceae Protodinium simplex Lohmann 1908

Thoracosphaerales Thoracosphaeraceae Scrippsiella acuminata (Ehrenberg) Retschmann, Elbrächter, Zinssmeister, S.Soehner, Kirsch, Kusber & Gottschling 2015

Torodiniales Torodiniaceae Torodinium robustum Kofoid & Swezy 1921

Phylum CRYPTISTA

Class Katablepharidophyceae

Katablepharidales Katablepharidaceae Leucocryptos marina (Braarud) Butcher 1967

6). The Shannon species diversity index was quite high and amounted to 3.0 bits/ind., the evenness index was 0.5.

The second community was distributed more seaward, along the entire coast, usually above the depths of 100—500 m, and only in the north of the studied area it reached shallow waters. It was confined to the waters of the coastal front developing as a result ofmixing ofthe South Atlantic Central Water Mass (SACWM) and the waters of the continental runoff (Fig. 5). The community was characterised by low phytoplankton numbers (574 ± 151 thousand cells/L) and biomass (0.59 ± 0.18 mg/L). Like in the first community, here

diatoms also dominated in biomass (62%), while the share of dinoflagellates brought with oceanic waters increased to 22% (Table 3). The community was dominated by diatoms Proboscia alata and blue-green algae Trichodesmium erythraeum, the subdominants were diatoms Guinardia striata (Fig. 6). Shannon and evenness indices were slightly higher if compared to those of the first community (Table 3).

The third phytoplankton community was distributed more seaward than the community II, above the depths exceeding 500 m and was confined to the warm and salty oceanic waters ofthe SACWM (Fig. 5). It had the lowest phytoplankton abun-

Fig. 3. Spatial distribution of phytoplankton abundance (A; thousand cells/L) and biomass (B; mg/L) in the waters of the Guinea-Bissau EEZ in winter of 2013.

dance and biomass compared to the other two communities (Table 3), as well as a low level of diatom dominance but a higher proportion of dinoflagellates. Diatoms Paralia sulcata were the dominants; the subdominants were both diatoms (Nitzschia longissima) and dinophytes (Tripos muel-leri, Tryblionella compressa, and Scrippsiella acumi-nata) (Fig. 6). The Shannon index was quite high and amounted to 3.04 bits/ind., the evenness index was 0.8.

Discussion

The species composition of planktonic photo-trophic protists and cyanobacteria in the coastal waters of the Guinea-Bissau is very rich and similar to other areas of the tropical Atlantic Ocean (Averina, 1968; Dandonneau, 1972; Roukhiyainen, 1979; Ventzel, 1982; Binet, 1983; Bezborodov et al., 1988; Semenova and Kudersky, 2002).

Like in other areas of the Canary Current, dia-

Table 2. Frequency of occurrence (%) of permanent phytoplankton species in the waters of the Guinea-Bissau EEZ in winter 2013.

№ Species Division Occurrence, %

1 Protodinium simplex Lohmann 1908 Dinoflagellata 82

2 Scrippsiella acuminata (Ehrenberg) retschmann, Elbrächter, Zinssmeister, S.Soehner, Kirsch, Kusber & Gottschling 2015 Dinoflagellata 82

3 Cylindrotheca closterium (Ehrenberg) Reimann & J.C.Lewin 1964 Heterokontophyta 79

4 Leucocryptos marina (Braarud) Butcher 1967 Cryptista 79

5 Amphidinium sphenoides Wulff 1919 Dinoflagellata 76

6 Lebouridinium glaucum (Lebour) F.Gomez, H.Takayam, D.Moreira & P.Lopez-Garcia 2016 Dinoflagellata 73

7 Nitzschia bicapitata Cleve 1901 Heterokontophyta 61

8 Chaetoceros curvisetus Cleve 1889 Heterokontophyta 58

9 Navicula mollis (W.Smith) Cleve 1895 Heterokontophyta 58

10 Pseudo-nitzschia pungens (Grunow ex Cleve) Hasle 1993 Heterokontophyta 58

11 Tryblionella compressa (Bailey) Poulin 1990 Dinoflagellata 58

12 Gyrodinium spirale (Bergh) Kofoid & Swezy 1921 Dinoflagellata 55

13 Torodinium robustum Kofoid & Swezy 1921 Dinoflagellata 55

Fig. 4. Dendrogram of a cluster analysis of the phytoplankton biomass data at different stations in the waters of the Guinea-Bissau EEZ.

toms and dinophytes dominated the phytoplankton in the EEZ waters of the Guinea-Bissau, which is typical oftropical oceanic waters (Bezborodov et al., 1988; Productivity patterns..., 2010).

The spatial distribution of phytoplankton, their abundance and biomass varied markedly in the ocean and coastal areas of the study region. A decrease in phytoplankton concentrations from coastal to oceanic waters is generally typical of the ocean ecosystems (Bezborodov et al., 1988). The mosaic distribution of phytoplankton was recorded in the relatively shallow part along the shelf and especially in the north of the area. This mosaic distribution of plankton is usually explained by the

Q-Community I Q - Community II Iff] - Community III

Fig. 5. Spatial distribution of phytoplankton communities in the waters of the Guinea-Bissau EEZ in winter 2013.

complex structure of waters (Bezborodov et al., 1988; Demarch, 2009; Productivity patterns..., 2010). In particular, in the well-studied areas close to Morocco and Mauritania, the formation of mosaic areas of high phytoplankton concentration was caused by coastal upwelling, which ensured the influx of nutrients from deep waters into the euphotic zone (Pavlov, 1968; Valdes and Deniz-Gonzalez, 2015). Off the coast of Guinea-Bissau, the reason for the mosaic structure of phytoplankton appears to be the influx of nutrients in warm shelfwaters due

Table 3. Key characteristics of the phytoplankton communities in the waters of the Guinea-Bissau EEZ in winter 2013.

Characteristics Community I Community II Community III

Number of taxa 126 127 73

Biomass, mg/L 4.19±1.50 0.59±0.18 0.07 ± 0.02

Abundance, thousand cells/L 603±88 574±151 65 ± 11

Shannon index, bits/ind. 2.96 3.04 3.04

Pielou Evenness Index 0.54 0.64 0.76

Relative biomass:

-Heterokontophyta, % 97.0 61.5 52.0

-Chlorophyta, % 0.2 0.1 0.4

-Cryptista, % 0.1 0.1 1.1

-Cyanobacteria, % 0.2 18.0 2.7

-Dinoflagellata, % 2.7 22.1 46.2

-Euglenophyta, % 0.1 1.1 1.4

Community

rira V w

Ceratium setaceum Nitzschia longissima Paralia sulcata i Prorocentrum compressum i Scrippsiella acuminata Others

al., 1993), the waters of the coastal ecosystem of Guinea-Bissau can be classified as mesotrophic, where the average phytoplankton biomass varies in the range of 0.6-2.0 mg/L.

Analysis of the coenotic organisation of phy-toplankton allowed distinguishing three communities. The first, the community of shelf desalinated waters, could be characterised by the highest values of phytoplankton abundance and biomass, low Shannon and Pielou indices. The second, the community of mixed waters, had lower phytoplankton numbers and biomass, the decreased proportion of large-celled diatoms and higher Shannon and Pielou indices. The third phytoplankton community, developing adjacent to the oceanic water masses, was characterised by low abundance and biomass, which values were more than four times lower than in the first community. In the third community, an increase in the proportion of dinoflagellates was recorded, which is a feature of the open ocean waters.

According to the theory of architectonic complexes proposed by K.V. Beklemishev (1969), the phytoplankton communities that we identified can be characterised as follows: community I -neritic (shelf desalinated waters), community II - secondary ecotone type (waters along the coastal front), and community III - distant neritic (waters of the Southern Atlantic Central Water Mass).

The results of this study show that phototrophic protists and cyanobacteria in phytoplankton communities play the role of biological indicators of the hydrological conditions in the coastal GuineaBissau waters. At the same time the variability of water masses with different characteristics largely determines the structure and composition of phytoplankton.

Fig. 6. Species structure of phytoplankton communities in the waters of the Guinea-Bissau EEZ in winter 2013.

to the continental runoff (Lidvanov et al., 2022).

In the waters of Guinea-Bissau, the concentration of phytoplankton was almost three times higher than in the Moroccan area, where its abundance and biomass in winter were 113.8 ± 1.34 thousand cells/L and 0.41 mg/L, respectively (Roukhiyainen, 1979; Semenova and Kudersky, 2002).

Based on the average phytoplankton biomass, the trophic status of waters can be assessed. According to the trophic classification (Oksiyuk et

Conclusions

The article for the first time describes in detail the taxonomic composition of planktonic phototrophic protists and cyanobacteria, community structure, and quantitative estimates of phytoplankton in the exclusive economic zone of Guinea-Bissau in the cold season. In the first half of January 2013, the phytoplankton was represented by 189 species belonging to seven main taxonomic divisions. The heterokont (56%) and dinophyte (34%) algae were characterised by the greatest species diversity. The most productive area was the shelf zone, where the numbers and biomass of phytoplankton averaged

555.1 thousand cells/L and 1.76 mg/L, respectively. Also in the shelf zone, the maximum values of the phytoplankton abundance and biomass were recorded (2.1 million cells/L and 10.69 mg/L, respectively), being most likely confined to desalinated waters enriched with nutrients. In the direction towards the open ocean, those characteristics decreased to 30 thousand cells/L and 0.01 mg/L. The main portion of phytoplankton biomass was created by the heterokont algae (86%). Based on the results of multivariate statistical analysis, three phytoplankton communities were distinguished in the study region: the neritic one, the community of secondary eco-tone type, and the distant neritic community. These community types corresponded to the classification of Beklemishev (1969) and differed in biotopic and cenotic structures. The average values of the phyto-plankton abundance and biomass near GuineaBissau corresponded to the mesotrophic class of waters and were almost three times higher than those for the Moroccan zone were. The data obtained are well consistent with the general concept about the high productivity of the waters of Guinea-Bissau compared with other regions of the central-eastern Atlantic Ocean.

Acknowledgements

The contribution of I.V. Telesh to this research was supported by the Russian Science Foundation project # 22-14-00056 (https://rscf.ru/ project/22-14-00056/).

References

Abakumov V.A. 1983. Guideline for methods of hydrobiological analysis of surface waters and bottom sediments. Gidrometeoizdat, Leningrad, pp. 78-111.

AI-Kandari M., AI-Yamani F.Y. and AI-Rifae K. 2009. Marine phytoplankton atlas of Kuwait's waters. Kuwait Institute for Scientific Research, Kuwait City.

Averina I.A. 1968. Phytoplankton of the Dakar and Takoradi Region in February-March 1961. Plankton of the Pacific Ocean. Nauka, Moscow, pp. 147-155.

Bakanov A.I. 2005. Quantitative assessment of dominance in ecological communities. Quantitative methods for ecology and hydrobiology. Samara Sci. Centre, Togliatti, pp. 37-67.

Beklemishev K.V. 1969. Ecology and biogeo-graphy of the pelagic zone. Nauka, Moscow.

Bezborodov A.A., Bulgakov N.P. and Burlakova Z.P. 1988. Tropical Atlantic. Region ofGuinea. Na-ukova Dumka, Kyiv.

Binet D. 1983. Phytoplancton et production primaire des regions cotieres a upwelling saisonniers dans le Golfe de Guinee. Trop. Oceanogr. 18: 331— 355.

Botes L. 2001. Phytoplankton identification catalogue. Saldanha Bay, South Africa. GloBallast Monograph Series 7. IMO, London.

Carmelo T. 1997. Identifying marine phytoplankton. Academic Press, London. https://doi. org/10.1016/b978-0-12-693018-4.x5000-9

Dandonneau Y. 1972. Study on phytoplankton on continental-shelf of Ivory coast. 2. Representation of water surface for description and reinterpretation of dynamic phenomena. Cahiers Orstom Oceanographie. 10 (3): 267-274.

Demarch H. 2009. Trends in primary production, sea surface temperature and wind in upwelling systems (1998-2007). Progress in Oceanography. 83 (1-4): 376-385. https://doi.org/10.1016/j. pocean.2009.07.022

Demarcq H., Barlow R. and Shillington F.A. 2003. Climatology and variability of sea surface temperature and surface chlorophyll in the Ben-guela and Agulhas ecosystems as observed by satellite imagery. African J. Mar. Sci. 25 (1): 363-372. https://doi.org/10.2989/18142320309504022

Fedorov V.D. 1979. On methods for studying phytoplankton and its activity. Publ. Moscow University, Moscow.

Fraga F. 1974. Distribution des masses d'eau dans l'upwelling de Mauritanie. Tethys. 6 (1-2): 5-10.

Honey K. and Elvin S. 2013. Towards ecosystem-based management ofthe Guinea current large marine ecosystem. United Nations Development Programme. https://www.undp.org/sites/g/files/ zskgke326/files/publications/GCLME%20Report %202013.pdf

Ibe C. and Sherman K. 2002. 3 The Gulf of Guinea large marine ecosystem project: Turning challenges into achievements. Large Marine Ecosystems. 11: 27-39. https://doi.org/10.1016/S1570-0461(02)80025-8

Lidvanov V.V., Shnar V.N. and Korolkova T.G. 2022. Mesozooplankton of coastal waters ofSenegal and Guinea-Bissau. J. Siberian Federal University, Ser. Biol. 15 (4): 529-551. doi: 10.17516/1997-1389 -0402

Nixon S. and Thomas A. 2001. On the size of the Peru upwelling ecosystem. Deep-sea research Part I: Oceanographic Research. 48: 2521-2528. https://doi.org/10.1016/s0967-0637(01)00023-1

Odum Yu. 1986. Ecology. Mir, Moscow.

Oksiyuk O.P., Zhukinsky V.N., Braginsky L.P. et al. 1993. Complex ecological classification of the quality of land surface waters. Hydrobiol. J. 29 (4): 62-76.

Pavlov V.Ya. 1968. On the distribution ofplank-ton in the Cap Blanc area. Oceanology. 8 (3): 479486.

Productivity patterns in the Guinea current large marine ecosystem with regard to its carrying capacity for living resources. 2010. GCLME Productivity demonstration project. https://iwlearn.net/resolve uid/13d055a37da64f99861b3761dc2dca2c

Radchenko I.G., Kapkov V.I. and Fedorov V.A. 2010. Practical guide to collecting and analysing samples of marine phytoplankton: Educational and methodological guidelines for university students of biological specialties. Mordvintsev, Moscow.

Roukhiyainen M.I. 1979. Phytoplankton off the Northwestern Coast of Africa. Sea Biology. 51: 59-65.

Semenova S.N. and Kudersky S.K. 2002. Features of the development of the phytocene off the Atlantic coast of the Kingdom of Morocco in the cold and warm seasons of 1994-1999. Fishery Biological Studies of AtlantNIRO in 2000-2001. Vol. 1. The Atlantic Ocean and the southeastern part of the Pacific Ocean. AtlantNIRO, Kaliningrad, pp. 72-85.

Valdes L. and Deniz-Gonzalez I. (Eds). 2015. Oceanographic and biological features in the Canary current large marine ecosystem. IOC Technical Series 115. IOC-UNESCO, Paris.

Ventzel M.V. 1982. Phytoplankton of the Region North of Cap Blanc. Oceanic Phytoplankton and Primary Production. Nauka, Moscow, pp. 72-83.