ABSTRACT
The present paper reports 8 species of the dinoflagellate genera Ornithocercus Stein, Podolampas Stein and Pyrocystis Murray from the Grand-Lahou lagoon complex. For Ornithocercus and Podolampas genera, dichotomous key for identification of species is presented. Diagnostic descriptions, illustrations and geographic distribution are provided for all taxa. Most species were neritic or neritic-oceanic and tropical or sub-tropical in nature which is indicative of the area of study. New distribution records (Podolampas elegans Schütt and Pyrocystis robusta Kofoid) for the Côte d’Ivoire part of the Gulf of Guinea originated mainly from an oceanographic station (Station 2: Grau of Lahou) situated further from the coastline.
Key words: Côte d’Ivoire, dinoflagellates, Grand-Lahou lagoon complex.
Dinophyceae commonly called dinoflagellates constitute a very important group of marine phytoplankton. It’s comprised of various species in terms of habitat and nutrient uptake. These species contribute to primary production in oceans and include diverse tropical species reported in many waters worldwide (Kim et al., 2013).
Significant works on the taxonomy and ecology of marine Dinophyceae have been carried out in many countries like: Japan, Germany, U. S. A., Eastern Africa etc (Sournia, 1967). In Côte d’Ivoire, there have been few studies on phytoplankton taxonomy, species composition and distribution including the dinoflagellate genera Ornithocercus Stein, Podolampas Stein and Pyrocystis Murray (Reyssac, 1970; Dandonneau, 1971; Dufourand Durand, 1982; Couté and Iltis, 1985; Dufour, 1994; Komoé et al., 2014).
Unfortunately no thorough systematic studies have been carried out along the Côte d’Ivoire seaboard. Taking into account the above lack of information, the following work was carried out on the Grand-Lahou lagoon complex water near the Atlantic Ocean. The main objective of this study is to provide a taxonomic and floristic account of species from genera Ornithocercus, Podolampas and Pyrocystis occurring in Grand-Lahou lagoon complex water.
Grand Lahou lagoon (5°, 07-5°, 14 N, 4°-5°, 25W, 190 km2, mean depth of ca. 3 m) spreads on about 50 km along the Gulf of Guinea coastline (Lecolle, 1971). It comprises of four basins (Lae, 1982) (Figure 1). The Tadio lagoon (90 km2, 2-3 m in maximum depth) is the large stone. It undergoes the influence of a small forest river (Boubo) having two floods in May-July and October-November, the former one being the most important.
The Niouzoumou lagoon (15 km2, 3 m in maximum depth) is a narrow basin parallel to the coastline. It is enclosed and sheltered on the superior strand of a 3,000 ha coconut agro-industrial plantation. The Mackey lagoon (28 km2), the shallowest basin (2 m in maximum depth) joins the Tadio and Tagba lagoons. The Tagba lagoon (57 km2) located at the eastern extremity has an average depth of 3 m, but its depth can reach 8 m at the level and near the channel. It communicates directly with the sea by the only outlet of the complex, the Grand-Lahou channel, and receives water inputs of the Bandama river during the unique floods occurring in October-November (N’doua et al., 2009).
The phytoplankton samples for taxonomy studies were collected during the period from July 2004 through June 2006 with 20 µm mesh plankton net by vertical tows in the centre of the stream at every sampling station (Table 1). Samples were transferred into plastic vessel (40 ml) and fixed with 40% formalin buffered with borax to a final concentration of 5% (Throndsen, 1978).
Observations were carried out using an Olympus CX31 microscope, equipped with a digital camera. The identification and distribution of the species were based on the research done by Abé (1967a, 1967b), Saifullah et al. (2008), Okolodkov (2010) and others.
The pH values varied between 6.63 and 9.23; surface temperature varied between 17.25 and 30.43°C and the conductivity between 0.5 and 41.64 mS cm-1. The surface salinity varied between 0. 25 and 26.95‰. Nitrates and phosphates values varied from 0.31 to 17.94 mg L-1 and from 0.07 mg L-1 to 2.24 mg L-1, respectively.
Taxonomic remarks: The different species observed are described alphabetically. Rule scale bars in illustrations represent 20 μm. New taxa to the algal flora of Côte d’Ivoire are designated with one asterisk (*).
Genus Ornithocercus Stein
Key to the identified species of genus Ornithocercus Stein
1. Left sulcal list quadrate shaped………O. quadratus
1. Left sulcal list not quadrate shaped…….2
2. Left sulcal list with 3 lobes…………….O. magnificus
2. Left sulcal list with more than 3 lobes:
3. All ribs ending at lobes………………..O. steinii
3. All ribs not ending at lobes……………O. thumii
Ornithocercus quadratus Schütt (Figure 2a)
References: Taylor et al. (2008, pp. 410-411), Figure 2d; Okolodkov (2010, p. 38, pl.4 Figure 9).
Description: Cells bodies are large, suboval, slightly deeper than long, with the epitheca markedly displaced to the ventral side. Cingulum is dorsally excavated and distinctly wider than ventrally.
Size: 45 x 37 µm (Station 2).
Distribution: Oceanic; warm temperate to tropical waters; worldwide distribution.
Ornithocerus magnificus Stein (Figure 2b)
References: Okolodkov (2010), p. 46, pl.5 (Figures 1 to 3).
Description: Cells bodies are relatively small, subcircular in lateral view, slightly asymmetrical in relation to the longitudinal axis, directed from the posterior dorsal end to anterior ventral end. The girdle list is very large with a spreading anterior skirt-like wing. The sulcal list is supported by radial ribs. The girdle list characterizes a convex and concave outline compared to other Ornithocercus species. Well known as a tropical planktonic species indicator.
Size: Length 88-100 μm (Station 2).
Distribution: Oceanic; cosmopolitan in warm temperate to tropical waters.
Ornithocercus steinii Schütt (Figure 2c)
References: Okolodkov (2010, p 46, pl.5 Figure 4).
Description: Girdle list is supported by rigid ribs. Sulcal list has several radial ribs with round outline.
Size: Length 116-166 μm, width 111-123 μm. Stations 2, 10
Distribution: Oceanic; cosmopolitan in warm temperate to tropical waters.
Ornithocercus thumii (Schmidt) Kofoid and Skogsberg (Figure 2d and e)
References: Okolodkov (2010, p. 46, pl.5 Figure 6).
Description: Girdle list spreads anteriorly like a skirt and the sulcus is supported by ribs with regular intervals. The outline of sulcal list is distinctively divided into three parts. The left dorsal hypothecal plate is, on the contrary, much simpler in its structure as illustrated in Figure 2e, in which the anterior ventral hypothecal plate is lost, leaving a corresponding broad but shallow dent at the anteroventral portion of the thecal plate.
Size of cell body: 48 x 40 μm, width 50 μm (Station 2).
Distribution: Neritic/oceanic species; tropical species; worldwide distribution
Genus Podolampas Stein
Key to the identified species of genus Podolampas Stein
1. Antapicalspines almost equal --------------------------------------------------------------P. bipes
1. Antapical spines not almost equal:
2. Spines with wings and wings connected-----------------------------------------------P. elegans
2. Spines are winged and not connected------------------------------------------------------------------------- P. palmipes
Podolampas bipes Stein (Figure 3a)
References: Taylor (1987, pp 58-59), Figure 2.16d; Sadaf and Muhammad (2014), p 95 (Figure 3a).
Description: The genus is characterized by the presence of a distinct apical horn ending in an apical pore and is generally pyriform in shape bearing two antapical spines. Cell looks like a slightly depressed chestnut. Epitheca is triangular, ending in two equal antapical spines. Hypotheca is half spherical form, with two left and right wing-like structures with sharp and strong spines at the antapical end.
Size: Length 100-115 μm, width 95 μm. Station 2.
Distribution: Oceanic; warm temperate to tropical waters; worldwide distribution.
*Podolampas elegans Schütt (Figure 3b)
References: Schiller (1937, p. 475, Figure 546).
The species is characterized by a bilaterally bulged midbody, the elongated conical apical horn and a low but uninterrupted antapical wing. This antapical wing consists of two median side-wings of the two antapical appendages which distinctly diverge distally and have rather a greater length as compared to the body length. More divergent, right antapical spine appears shorter than left.
Size: Length 80-100 μm, width 55-80 μm (Stations 2 and 10).
Distribution: Oceanic; subtropical to tropical waters; worldwide distribution.
Podolampas palmipes Stein (Figure 3c)
References: Sadaf and Muhammad 2014, p 95, Figure 3C1, C2
Description: Cell pyriform, narrow, ending in two unequal antapical spines. The epitheca is drawn out into a long, slender neck. The right-hand spine is much shorter than the left antapical spine.
Size: Length 60 μm, width 20 μm (Station 2).
Distribution: Oceanic; warm temperate to tropical waters; worldwide distribution.
*Pyrocystis robusta Kofoid (Figure 3d)
References: Sadaf and Saifullah (2009), p 3214, Figure 5.
Description: This species is lunate in form with jelly-like cyst body. Cytoplasm is located in the center of the cyst. Similar to P. lunula but relatively small.
Size: Length 90-125 µm. Station 2.
Distribution: Oceanic; warm temperate to tropical waters; worldwide distribution.
In addition to the species illustrated in the present study, Reyssac (1970) reported Ornithocerus magnificus Stein, Ornithocercus quadratus Schütt, Ornithocercus steinii Schütt, Ornithocercus thumii, Podolampas bipes Stein and Podolampas palmipes Stein from the Atlantic Ocean water (in total, 158 species of the order Dinophysiales).
Dandonneau (1971) mentioned 18 Dinophysiales species including Ornithocerus magnificus Stein, Ornithocercus quadratus Schütt, Ornithocercus steinii Schütt and Podolampas palmipes Stein. Couté and Iltis (1985) reported Ornithocerus magnificus Stein from Ebrié lagoon. It should be noted that systematic studies on the lagoon and marine environments are rare in Côte d’Ivoire.
The genus Podolampas is a pear shaped cell with an apical horn and 1 or 2 antapical spines (Burns and Mitchell, 1982). Podolampas bipes (Figure 3a) is recognized by relatively strong antapical spines with accessory lists which have smooth margins. Podolampas palmipes is relatively more slender than P. bipes and P. elegans. Dinoflagellates occur preferably in the tropical water (Taylor, 1987), hence a greater proportion of the species in the study area were tropical or subtropical in nature. Most species described in the present study were inventoried during the long dry season (December to March), during which period, the marine waters invade the lagoon waters and during the short dry season (August).
Indeed, August is the period of upwelling in the ocean, so we are witnessing has a nutrient recovery that cause algal blooms. The intrusion of seawater in the lagoon complex would explain the presence of species in the samples taken.
Most of the works cited in the present study are related to ecological studies except for Couté and Iltis (1985) who conducted systematic studies. The new records (Podolampas elegans Schütt and Pyrocystis robusta Kofoid) for the Côte d’Ivoire part of the Gulf of Guinea originated mainly from an oceanographic station (Station 2: Grau of Lahou) situated further from the coastline.
Authors did not declare any conflict of interest.
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