Checklist of tropical algae of Togo in the Guinean Gulf of West-Africa

The phytoplankton is an important part of the biodiversity and one of the bases of food networks of freshwater, brackish and marine environments. This study is carried out to record the algae flora (microalgae and macroalgae) in Togo regarding the floristic diversities. The results show that 795 species of microalgae have been recorded in Togo belonging to 134 families, nineteen groups among which the most important in terms of number of species are the Bacillariophyceae (26%), Cyanophyceae (17%), Chorophyceae (16%), Conjugatophyceae (12%) and Euglenophyceae (11%). The microalgae of Togo belong to 7 Divisions which are respectively Chromophyta (39%), Chlorophyta (32%), Cyanophyta (17%), Euglenophyta (11%), and Rodophyta (1%). More than 250 genera were recorded and the most represented genera are Navicula, Nitzschia, Scenedesmus, Trachelomonas, Closterium, Cosmarium, Oscillatoria, Phacus, Pinnularia, Staurastrum, Strombomonas, Lyngbya that cover 31% of microalga of Togo. For the macroalgae, 37 taxons were collected in total. Three Divisions of the macroalgae notably the Chlorophyta, Pheophyta and Rhodophyta are the most represented. The dominant species are from the Chlorophyta Division. These studies are still ongoing to improve the knowledge about the biodiversity of the aquatic environments algae in Togo.


INTRODUCTION
The phytoplankton constitutes the primary production in the watercourses and oceans (Field et al., 1998;Behrenfeld et al., 2001).It also constitutes an important part of the biodiversity and one of the bases of food networks of freshwater, brackish and marine environments (Tourte et al., 2005).
In Togo, the researches conducted on plants covered a large portion of Angiosperms.But the researches on the phytoplankton and the algae in particular are relatively recent (Atanlé et al., 2013;Radji et al., 2013).Very season and one rainy season notably along the Oti River and its affluents (Koumongou, Kara and Mô), the Mono River and its affluents (Ogou, Anié, Amou and Khra) and (ii) aquatic ecosystems of hydrologic regime influenced by the sub-equatorial climate with two rainy seasons that alternate with two dry seasons.It takes into account the Haho stream, the Zio stream and its main tributary the Lili; (2) Lentic environment: it's about lakes, lagoons and ponds in the South of Togo.Some of these watercourses are brackish and others are freshwaters.It includes also the Atlantic Ocean.Indeed, Togo is endowed with a coastine that stretches from West to East over a width 50 km, between the 6°01 and 6°05 latitudes Nord and the 0°70 and 1°40 longitudes East.The coastline is mainly sandy and has been subject for some years now to so severe marine erosion (Blivi, 1993).The offshore environment covers an area of 371 km.It is made up of a relatively flat and deep narrow continental table.It is 23 km wide and 100 m isobathic.The ocean bottoms are essentially sandy and sandy silt.Meanwhile there are many beach sandstone submarine levellings between 350 and 500 m from the coast.Togo has a special feature of beach-rock which is a geological formation made up of ancient corral reefs, today striped naked by the coastal erosion.This dead corral reef almost parallel at the shore is present on the sandy bottom in correspondance with 52 to 56 m isobathic over about 15 to 17 km along the coast.Beyong and up to the plateau fall, a large number of reef heads can be noticed.In the Gulf of Guinea, the sea surface temperature varies normally between 25 and 29°C but can fall down to 20°C during the upwelling of cold water (Segniagbeto and Van Waerebeek, 2010).The Guinean current is the main current in the Gulf of Guinea.It is supplied by the northern equatorial off Liberia and flows toward the East alongside the coast of Ghana, Togo, Bénin and Nigeria.The Gulf of Guinea concave topography deviate the Current of Guinea towards West that results into the South Equatorial Current.Upwellings of water rich of nutriments occur in the months of July and September as well as in January.The Gulf of Guinea tides originate from the South West.This concerns semi-diurnal tides with two irregularities.The tides height ranges from 1 to 3.5 rn (during the storm).The macroalgae have been harvested in this environment.These aquatic ecosystems are distributed into the 3 main watershed catchment basins of Togo notably the Volta basin, the Mono basin and the Lac Togo basin.

Data collection
The data collection took into account all the seasons of the year 2013 and covered all the aquatic ecosystems of Togo.For each site of water sample collection, the geographic coordinates are taken with the Global Positioning System (GPS) and positioned on the watershed catchment basin map of Togo thanks to MapInfo Professional software (Figure 1).Two different data collection approaches were used.For the microalgae, the samplings are conducted at 20 cm of the water surface for the surface waters (less than 50 cm depth).For the deep areas (>50 cm), the samplings are conducted at three levels (surface, mid-depth and depth) using an integrated water sampler bottle (Druart and Rimet, 2008).In all 135 water samples were collected nationwide in pillbox of 250 ml.After sampling, the phytoplankton was immediately fixed by an 1% concentrated lugol's solution which gives a light brown colour to the sample (Throndsen, 1978) and enables to better preserve the structure of the algae cells (Druart et al., 2005).The samples are kept in a cool place and in darkness up to the Palynology and Algology laboratory of the Faculty of Science of the University of Lomé.Each sample is left to rest for 24 h mnimum to enable the sedimentation of the algae (Nielsen, 1933).Water was later on sampled on top of the algae residue through siphonage.The concentrated algae water residue was conserved in the pillbox.For the identification of the phytoplankton, a water drop is sampled thanks to a Pasteur pipette.This drop is deposited in between slides then observed with the photon microscope adaped to a light room and a camera connected to a computer.The observation is repeated 3 times for the same site in order to establish the algae composition of each site, that is, 405 observations.The observations are done according to vertical scannings.The pictures are taken with 10X and 40X objectives.As for Diatomeae, the identification level and taxonomy is hard, thus, oil immersion and 100X objectives were used.From the observations and the pictures, the identification of the species is done thanks to the works of Lauterborn (1915), Skuja (1956), Grönblad et al. (1958), Coute and Rousselin (1975), Komarèk and Anagnostidis (1995), Sournia (1968), Compere (1991), of Krammer and Lange-Bertalot (1986-2000), of Bourrelly (1968Bourrelly ( , 1970Bourrelly ( , 1972Bourrelly ( , 1990)), and of Lavoie et al. (2008).For the macroalgae, the collections concern essentially the seaweeds.For this effect sampling are considered Photo 1. Seaweeds cropping up on the beach-rock in low normal tides.over the coastline.The samples are taken during low tide on the hard substrata on foot in the encroachment zones and other hard substrata of the coastline by diving.The fishermen's nets once back from sea are scrutinized to find algae brought in.Moreover, more systematic harvest was conducted on the beach-rock, after obtaining from the captaincy of the Port Authority of Lomé pieces of information about the daily schedule of the low tides during which a larger part of the beach-rock shows on the surface (Photo 1).The algae are placed in vials filled with seawater to be identified in laboratory.The identification is carried out at the laboratory through direct the observation by means of microscope for the very little size specimen.After theidentification, the specimens are kept at the Herbarium of the University of Lomé after a stay in the 4% formol.The classification of the algae per division, group, order and family being too complex and varied from one source to the other, the base list used in this article relied on AlgaeBase (Guiry and Guiry, 2014).

Macroalgae richness in Togo
In total 37 taxa were collected and 27 from them were identified to the genera or to the species (Table 4, Photo  3).Three Divisions of macroalgae notably Chlorophyta, Phaeophyta and Rhodophyta are the most represented in term of number of species.The Chlorophyta (green algae) dominates with 9 species.

DISCUSSION
This study is the most important to have carried out a relatively exhaustive analysis on the richness of the algae in Togo.On about 1,100 genera and 14,000 species spread in the world (Iltis, 1980), 795 species of microalgae are grouped in 282 genera and 37 macroalgae in about 20 genera were identified, in other words, a contribution of about 2.3% of the world algae flora.This richness is very high compared to the precedent studies during which many authors tried to collect phytoplankton species in Togo.Indeed, during the research works in the freshwater ecosystems (lakes and lagoons) of Southern Togo, Edorh et al. (2008), Léné (2004), Bandje (2010), Gnofam (2010), Issifou (2012) and Radji et al. (2013) indexed a specific algae richness of about 200 taxa of microalgae.These authors showed that in these areas, the Chromophyta with the species such as Cyclotella bodanica Eulenstein ex Grunow, C.  Kützing, Synechococcus aquatilis Sauv., are the dominant groups.The current study shows that considering the whole territory, it is still the same groups of Chromophyta (39%), of Chlorophyta (32%) and of Cyanophyta (17%) that dominate, confirming therefore the observations of these authors.Only these three groups represent 88% of the algae in Togo.The same observations are made by Iltis (1980) that confirm that the tropical algae flora is made up of a high proportion of representatives from the three groups.
With regard to the Togolese marine macroalgae, the only serious existing reference nowaday is Bandje (2004) that had identified 14 species of macroalgae of which 9 species fixed to the beach-rocks of the Togolese coast.This marine flora is far from reflecting the reality, making always unknown the marine flora of Togo.The current algae flora and the one indicated by Bandjé ( 2004) are far from the results of the first inventory of Colocoloff (1980).This author reported the presence of 170 species distributed in 37 families.The most represented genera are Gracilaria (12 species), Ceramium (8 species), Gelidiopsis (7 species), Hypnea (7 species), Laurencia (7 species), Caulerpa (4 species), Chaetomorpha (4 species), Cladophora (4 species), Codium (5 species), Gracilariopsis (4 species).These results from Colocoloff (1980) show that the Togolese marine environment is characterized by a diversified algae flora and that the studies are only at their beginning.The Sargassum genus is very abundant on the whole Togolese coast.Moreover, the analysis of the Togolese algae flora also shows that the Chromophyta occupy a great proportion (39%) on the whole algae flora in Togo.This situation is not a particularity for Togo.Many other studies showed in different aquatic ecosystems that it is the Chromophyta (generally the Diatomeae) that dominate the algae flora (Cetto et al., 2004;Felisberto and Rodrigues, 2005;Fonseca et al., 2008).These authors explain this dominance by the fact that the Diatomophyceae occupy a great number of species and is also higher in density; which make them great competitors of nutrients in the aquatic habitats (Vermaat, 2005).Then the Diatomophyceae are equipped with morphological structures that make them efficient in terms of space conquest in aquatic environment (Feng et al., 2011).From all the evidence, the algae flora of Togo is very rich and diversified but has been partially studied.Compared to Niger, the algae flora identified has 547 species dominated by the Cyanophyceae, the Diatomophyceae and the Euchlorophyceae (Saadou, 1998).In Senegal, the inventory of the algae has started just as in Togo, indicating 133 genera and about 83 species (Compère, 1991).This author remarked that the freshwater and brackish algae are more numerous as well as the microscopic algae must have had a special attention to complete the inventory.In many other countries in the sub-region, research works are conducted on the phytoplankton but the contrast remains the same; they are generally fragmented to have sufficient information among others on the biogeographical distribution over a continent.Globally it is demonstrated that the microalgae are cosmopolite with more than 60% met in diverse regions of the world while the species typically tropical represent about 40% (Iltis, 1980;Zongo et al., 2008).
It should also be mentioned that in the processing of the algae flora of Togo, some cases of potentially toxic algae were mentioned (Edorh et al., 2008;Bandje, 2010;Issifou, 2012).It is about Anabaena spp., Merismopedia spp., Microcystis aeruginosa (Kützing) Kützing, Nitzschia bilobata W.Smith, and Oscillatoria rubescens De Cand.These ones must be subject to a particular attention in the future works to analyse the level of nuisance for many of the rural populations depending on surface waters which are the privilege habitats of these algae.

Conclusion
It results from this study that in Togo, the knowledge about the biodiversity of the algae from the aquatic environments in Togo is advancing.In all 795 species of microalga belong to 82 genera, 134 families and 5 branches are the most dominant in Togo.Moreover, 37 taxa of macroalgae belonging to 3 Divisions notably the Chlorophyta, Pheophyta and Rhodophyta have been collected up to now.This first stage is necessary to further assume the studies on the distribution, the valorization of the phytoplankter biomass and the search for solution vis-à-vis the nuisance of the toxic species present in the surface waters used by the rural populations.The future research works must therefore be oriented towards this purpose.

ANNEXES
Checklist of Togolese Microalgae.

Division/Group
Family Species I-Chlorophyta
Photo 3. Some specimen of macroalgae of Togo.

Table 1 .
Most represented genera of microalgae in Togo.

Group/Genera Family Representatives in the genera % compared to the total number of genera Number of species I-Bacillariophyceae
Some specimen of microalgae in Togo.

Table 2 .
Richness of microalgae families in Togo.Synurophyceae and Ulvophyceae contain respectively 1% of the algae flora.The Nephrophyceae, Rhodophyceae, Raphydophyceae and Stylonematophyceae are also a group that are present in Togo but in a low proportion (Table

Table 3 .
Most represented groups of microalgae in Togo in term of species.

/Group Representatives in the group % compared to the total number of Divisions Number of species I-Chromophyta
Figure 2. Distribution of the microalgae Division in Togo.