The marine flora of the Cap Blanc peninsula: its distribution and affinities

Botanical Journal of the Linnean Society, 75: 99-1 18. With 4 figures

July 1977

The marine flora of the Cap Blanc peninsula: its distribution and affinities G. W. LAWSON

School o f Plant Biology, University College of North Wales, Bangor

AND

D. M. JOHN

Department of Botany, University o f Ghana, Legon, Ghana

Accepted for publication November 1976

The shores of the Cap Blanc peninsula, along which runs the border between Mauritania and Western Sahara (former Spanish Sahara), were studied in November 1975. Littoral zonation is described and an annotated list is presented of the 188 species of algae now known from Mauritania and Western Sahara together with a further 23 species identified only to genus. In this present study 88 species of algae (excluding Cyanophyceae) were determined resulting in an increase of 67% and 37% respectively for the previously known marine floras of Western Sahara and Mauritania. Of 97 marine algae known from specific localities on the Cap Blanc peninsula, only 21 are common to both its eastern and western sides. Several tropical species reach their northern limit on the eastern side of the peninsula and many warm-temperate species reach their southernmost limit on the western side. Thus the Cap Blanc peninsula appears to represent a boundary between the warm temperate seaweed flora of North West Africa and the subtropical transition flora of Mauritania and Shegal to the south.

KEY WORDS :-marine algae-distribution.

CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . 100 Physical features of the environment . . . . . . . . . . . . . . . 101 Patterns of littoral zonation . . . . . . . . . . . . . . . . . 103

Baie de I’Etiole (site 1) . . . . . . . . . . . . . . . . . 103 Pointe de 1’Etiole to Pointe des Maures (site 2) . . . . . . . . . . 104 Lagoon (site 3) . . . . . . . . . . . . . . . . . . . 105 Nouadhibou (site 4) . . . . . . . . . . . . . . . . . 105 Cansado (site 5) . . . . . . . . . . . . . . . . . . . 105 Cap Blanc-east side (site 6) . . . . . . . . . . . . . . . 106 Cap Blanc-west side (site 7) . . . . . . . . . . . . . . . 106 La Giierra (site 8) . . . . . . . . . . . . . . . . . . 107 General features of zonation . . . . . . . . . . . . . . . 107

Discussion . . . . . . . . . . . . . . . . . . . . . . 108 Annotated species list . . . . . . . . . . . . . . . . . . . 110 Acknowledgements . . . . . . . . . . . . . . . . . . . . 116 References . . . . . . . . . . . . . . . . . . . . . . 116

99

100 G. W. LAWSON AND D. M. JOHN

INTRODUCTION

The Cap Blanc peninsula, on the coast of West Africa, occupies a position of some considerable interest for marine biogeography. To the north, stretching for over 1000 km and lying partly within and partly outside the tropics, is the inhospitable coastline of former Spanish Sahara. Morocco and Mauritania took over the administration of this Spanish colony in 1976 and since then the country has been known as Western Sahara. Marine algal records from this country are very few and an assessment of the exact number of species is complicated by the fact that the northern boundary of Western Sahara has been subject to a number of political changes in recent times. Since most of what collecting has been done has taken place in the northern region, records for seaweeds from ‘Spanish Sahara’ and ‘Rio de Oro’ in the literature, where no specific localities are given, have to be assessed according to the date of publication. In the brief account by Primo (1953) it is clear that the algal vegetation of the northern region around Cape Juby (which became part of Morocco in 1958) bears a strong resemblance to the coast of North-west Africa and South-west Europe in having large kelp beds of Saccorhiza polyschides and Laminaria ochroleuca along with fucoids including Fucus spiralis and Bifurcaria bifurcata. Such plants are characteristic of the colder northern waters but it should be noted that Primo also records some warmer water species, for example, Sargnssum vulgare. The most southerly point he studied was apparently around Dakhla (formerlv Villa Cisneros) which lies just outside the tropics. He reported a single instance of a holdfast of Saccorhiza polyschides found fixed to a rock so it is clear that the bulk of the Laminariaceae drop out somewhere between Cape Juby and Dakhla. The Western Saharan side of the Cap Blanc peninsula apparently has not been the subject of earlier investiga- tions although Hariot’s Mauritanian records (Hariot, 191 1) are from the Baie de 1’Ouest which straddles the border between the two countries. Feldmann (1951) also records Ecklonia muratii from ‘L’Aguerguer’ which is about 50 km north of the tip of Cap Blanc and hence in Western Sahara.

To the south of the Cap Blanc peninsula, as Sourie (1954a) has pointed out, the coastline consists almost entirely of beaches and dunes and is largely unsuitable for algal attachment for about 750 km until the village of Yof is reached at the north-western extremity of the Cap Vert peninsula. The marine flora of the Cap Vert peninsula is one of the better-known in West Africa following the work of Bodard (1966; 1968), Dangeard (1952), Sourie (1954a, 1954b), and Trochain (1940). It appears to represent a transition zone between the northern warm temperate province and the tropical Gulf of Guinea region where some species such as Ecklonia muratii, Plocamium raplzelisianum and Corallina mediterranea reach their southern limit. Where many of the Gulf of Guinea species reach their northern limit is not always clear. One of the objects of the present survey was to find out the extent t o which the tropical element reaches northern Mauritania and the degree to which the Cap Blanc peninsula can also be regarded as a transition zone.

The Cap Blanc peninsula partly encloses on its eastern side the Baie du LCvrier, one of the largest bays along the west coast of Africa. This shallow bay is protected to some extent from cold upwelling water and from heavy wave-action by the peninsula. Sea surface temperatures in the bay are therefore

MARINE FLORA OF THE CAP BLANC PENINSULA 101

always higher than those on the Atlantic side of the peninsula (see Fig. 2). It is clear that conditions for marine life are somewhat different on the two sides of the peninsula (see below) and it is to be expected that these will be reflected in floristic differences.

A total of 11 5 species of marine algae has been recorded in papers dealing with Mauritania. The great majority are from Cap Blanc itself and most of these are from the eastern side, although Hariot (1911) records 19 species from 'Baie de l'Ouest' which is on the western side of the peninsula. Dangeard's records (Dangeard, 1952) are apparently from the eastern side and Sourie's (Sourie, 1954a) are from the east and also the southern tip of Cap Blanc. Only a few algae are reported from areas outside the peninsula, such as at Cap St Anne (Hariot, 1911).

PHYSICAL FEATURES OF THE ENVIRONMENT

The Cap Blanc peninsula, which runs roughly north-northeast to south- southwest for about 60 km (Fig. l ) , terminates in a plateau edged by tall and precipitous cliffs of ill-consolidated quaternary marine deposits. P.ock falls have taken place where the sea has undercut these friable sandstone cliffs and the resulting breaks often afford the only access to the littoral zone for large stretches of shoreline. These high cliffs give way northward to sandy beaches and low rocky outcrops which are interspersed between areas of low cliff. On the eastern side of the peninsula the littoral rocks extend intermittently for almost half of its length reaching as far as the Baie de 1'Etiole. This bay consists of a shallow basin opening to the sea by a tidal creek. In the vicinity of the Raie de l'Etiole, and particularly to the north of it, are a number of very shallow lagoons in contact with the sea only at high waters of spring tides.

Cap Blanc lies within the subtropical arid zone having a very low rainfall and air humidity, and large daily and yearly fluctuations in air temperature. The rainfall is insignificant and only 10 days per annum on average have 0.1 mm or more. Relative humidity at noon for any month of the year never averages more than 65%. The highest mean daily air temperatures are to be found in October (30"C), and the lowest in December and January (25°C) when the dry, north-easterly Harmattan wind blows for much of the time from the desert. During the early part of the year this wind gradually veers to the west so that by July it blows predominantly from the north-west and during the same period the relative humidity a t midday rises from about 55% in January to 65% in July. Towards the end of the year the wind direction becomes more northerly and the relative humidity begins once more to decline. There are considerable daily fluctuations in air temperature with the average daily range for the year being from 10" t o 15" C.

This part of the West African coast is bathed by the cold Canary current whose general set is south-westward, i.e., almost parallel t o the coast. The seasonal change in the temperature of the surface water in the vicinity of Cap Blanc (Fig. 2) shows that the highest temperatures are attained between July and October (>21" C). A rapid fall in sea temperature takes place in November with the minimum seasonal temperature being found from November to about May (1 6" to 19" C). The low sea temperatures are due to the combined effect of the Canary current and to the upwelling of colder under-surface water which


lorn

17‘00 8 20040

1P50 1 1

Figure 1. Map of the Cap Blanc peninsula showing the eight sites visited. A and B are stations at which sea water temperature was measured (see Fig. 2). Insert indicates the position of the Cap Blanc peninsula in relation to the rest of the North West African coast. Sites: 1, Baie de 1’Etiole; 2, Pointe de 1’Etiole t o Pointe des Maures; 3, Lagoon; 4, Nouadhibou; 5 , Cansado; 6, Cap Blanc-east side; 7, Cap Blanc-west side; 8, La Giierra.

occurs along the West African coast and is, in fact, most marked near Cap Blanc.

The hydrological conditions on the eastern and western side of the Cap Blanc peninsula are dissimilar. The shallow Baie du LCvrier on the eastern side of the peninsula is less than 10 m deep over most of its area and never more than 20 m. In this bay the seg surface temperatures are always about a degree or two higher than those on the western side of the peninsula (Fig. 2). The

MARINE FLORA O F THE CAP BLANC PENINSULA

24

22 0

Ed 2o

18

16

103

r

-

-

-

- I ' I I I I I 1 I 1 I I 1

J F M A M J JI A S 0 N D Months

Figure 2. Mean monthly sea water temperature (surface) recorded a t a station within the Baie du Lkvrier (A) and one to the west of Cap Blanc (B) during 1967 (see Fig. 1).

salinity is also somewhat greater (37 t o 38"/,,) t o the east of the peninsula as a result of increased evaporation and the slow replacement of water in the bay. Higher surface temperatures and salinities suggest that the Baie du Lkvrier is less influenced by the upwelling of deeper water than areas t o the west of Cap Blanc.

The Baie du Lkvrier side of the Cap Blanc peninsula is relatively protected whilst the western side is exposed to considerable wave-action. The amplitude of the tides is comparatively small and each tide is somewhat higher on the eastern side of the peninsula. The tidal data for ports on each side of the Cap Blanc peninsula are given below in metres above Chart Datum: -

MHWS MHWN MLWS MLWN

La Ciierra, Western Sahara ( 20" 50', 17" 06') 1.43 1.00 0.18 0.61

Nouadhibou, Mauritania (20°55', 17'02') 2.22 1.74 0.49 0.97

PATTERNS O F LITTORAL ZONATION

The localities at which descriptions and collections were made are shown on

The main features of algal distribution at each side of these localities using the map of the Cap Blanc peninsula (Fig. 1 ).

the terminology of littoral zonation of Lewis (1961) is given below.

Baie de I'Etiole (site 1)

This, the most northerly of the localites visited, is situated in a very sheltered position on the Baie du LCvrier side of the Cap Blanc peninsula. The Baie de 1'Etiole is largely filled with salt marsh and entering it from the south and turning westwards into the bay is a tidal creek. The main mud flat in the centre

104 G . W. LAWSON AND D. M. JOHN

of the bay appeared to be rather homogeneous and to be dominated by Spartina maritima (Curtis) Fernald which reached down to the waters edge on the scoured north bank of the creek but a rather distinct zonation was observed on the gently sloping southern bank. The uppermost part of this bank, in a position inundated only occasionally by high tides, bore a number of halophytes notably Salicornia fruticosa (L.) L. and Sesuvium portulacastrum (L.) L. Below this was a rather bare area containing shallow pools in which occurred either Enteromorpha clathrata alone or Chaetomorpha brachygona accompanied by Rhizoclonium implexum. Further down the slope occurred Spartina maritima and a belt, terminating at about the level of low water neaps, of the small sea grass Halodule wrightii Ascherson, the limp leaves of which rest on the surface of the muddy or sandy substratum at low water. Occasional patches of Enteromorpha intestinalis subsp. intestinalis and Rhizoclonium africanum were found amongst the Halodule.

Fine brown filaments of Feldmannia irregularis grew on shells at the bottom of this belt of rather bare mud but below and reaching into the sublittoral was a vigorous growth of another and larger sea grass Cymodocea nodosa (Ucria) Ascheron which bore many epiphytes including Dictyota bartayresii, D. dichotoma, Cevamium gracillimum var. byssoideum, Erythrotrichia carnea, and fragments of a Cladophora species. Towards the mouth of the creek the sea grass community gradually petered out and gave way to a mud flat covered by shells and stones on which grew a number of small algae including Bachelotia antillarum, Gelidium pusillum var. pulvinatum and Rhizoclonium implexum.

A notable feature of this sheltered bay was the absence of mangrove vegetation, the northern limit of which is just to the north of St Louis in SCnCgal about 570 km t o the south of Cap Blanc (Trochain, 1940).

Pointe de I’Etiole to Pointe des Maures (site 2)

On the southern border of the Baie de l’Etiole, where it enters the sea, there is a low cliff about 3 m high rising above the mud flats already described. The upper metre or so of cliff was rather bare although on similar rocks in a somewhat more wave-exposed position further south the blue-green alga Entophysalis deusta was found at this level. The next half metre or so of cliff was sparsely covered by barnacles and the snail Littorina cingulifera Dunker followed by another half metre of a much denser development of barnacles with the larger snail Monodonta colubrina and Gelidium pusillum in cracks. The lowermost metre of cliff was the region where the algae grew in most abundance. Here, there was a relatively thick growth of Gelidium pusillum mixed with some Bachelotia antillarum and occasional strands of Rhizoclonium implexum. The most common alga on the small rocks littering the platform at the base of the cliff was Gigartina acicularis.

The rock platform was gently sloping and in the shallow sublittoral was a rich and varied community of seaweeds. The rather patchy nature of this community was indicated by the presence of darker areas of vegetation and lighter ones of sand seen below the water surface when viewed from the cliffs above. This sublittoral community was dominated by Spyridia hypnoides and species of Cystoseira including C. tamariscifolia. Sargassum vulgare was present but not abundant and in some of the patches the marine grass Cymodocea


nodosa was a common constituent. Forming an undergrowth beneath these larger plants were many smaller species among which were the following: Amphiroa fragilissima, Champia parvula, Cladophora prolifera, Derbesia furcellata, Gelidiopsis variabilis, Gigartina acicularis, Jania rubens, Laurencia obtusa, Ophiocladus simpliciuscula, Padina vickersiae, Plocamium raphlesianum, and Pt erosipho nia pennata.

On the larger algae epiphytes were abundant and included Centroceras clavulatum, Dictyota dichotoma, D, ciliolata, Colpomenia sinuosa, Herpo- siphonia tenella (including variety secunda), Hypnea musciformis, Hetero- siphonia wurdemannii, Laurencia obtusa, and several species of Ceramium including C. stricturn. Probable constituents of this sublittoral community found unattached in the drift were Codium tomentosum and Padina tetrastro- ma tica.

Lagoon (site 3) At a locality close to Nouadhibou, just north of the airport, was a very large,

but shallow, lagoon believed to be open to the sea only periodically at spring tides. The floor of this lagoon was almost completely covered by thick mats of the blue-green algae Microcoleus lyngbyaceus and Schizothrix calcicola. The southern shore of this lagoon was littered with the dried mats of these blue-green algae, blown ashore by the Harmattan wind at the time of our visit (November).

Nouadhibou (site 4 )

At Nouadhibou the sandy beach was liberally strewn with wrecks, both iron and wooden, and these formed the main substratum for algal attachment. Frequently a rather narrow belt of Enteromorpha intestinalis subsp. intestinalis was present in the upper midlittoral along with barnacles. Below this was a wider band dominated by blue-green algae. At the lowest levels just above the sand, mussels were common and mixed with them was a low turf of algae including Gelidium pusillurn var. pulvinatum, Giffordia mitchelliae, Feldmannia irregularis, Herposip ho nia ten ella, Ery t h ro trich ia earn ea, Go n io trich u m alsidii, Acrochaetium seriatum, and a species of Cladophora.

Cansado (site 5 )

Cansado Point is formed of a low sandstone cliff jutting out into the Baie du Lkvrier at the southern end of Cansado bay. The south side of this point near the Cansado Hotel was fairly sheltered and perhaps polluted with sewage, whereas the eastern and northern parts of the point received more wave-action and were less polluted. In sheltered parts of the littoral fringe the rocks were apparently populated solely by Littorina cingulifera, L. neritoides L. and a species of Monodonta, but with some wave-exposure these snails were accompanied by Entophysalis deusta. Flat shelves of rock at this level receiving spray but, not draining easily, were covered by a thick coating of the blue-green algae Schizothrix calcicola and Microcoleus lyngbyaceus. The eulittoral zone could be divided into three fairly distinct subzones-an upper subzone with a


thick covering of barnacles, a middle subzone dominated by an algal turf consisting of Gelidium pusillum and Caulacanthus ustulatus accompanied by patches of Enteromorpha jlexuosa subsp. jlrxuosa and Ulva lactuca, and a lower subzone of mussels with Ralfsia expansa, Feldmannia irregularis, and Corallina berterii. Near sewage outfalls a low felt of such blue-algae as Microcoleus lyngbyaceus locally covered the lower part of the eulittoral zone. Fragments of Cymodocea nodosa and Codium decorticatum bearing epiphytic Herposiphonia tenella, Entocladia viridis, and species of Polysiphonia and Enteromorpha, were present in the drift and it is likely that the offshore sublittoral community was similar to that described for the area between Pointe de 1’Etiole and Pointe des Maures.

Cap Blanc-east side (site 6 )

Access to the shore in the vicinity of Cap Blanc is difficult and only one locality was visited on its eastern side. I t lay about 3 km to the north of the Cape at a point where the cliff was broken and where massive boulders had fallen into the sea. The rocks were only moderately exposed to wave-action. Here the littoral fringe was dominated by Littorina cingulijera and L. neritoides with a species of Monodonta present in the lower part of this zone. With some shade a blackening of the rock surface caused by Entophysalis deusta occurred. The upper limit of the eulittoral zone was defined by a good development of barnacles accompanied by Patella intermedia Jeffrey and P. safiana Lamark. In the lower part of the barnacle zone was a very low, red algal turf of intermixed Gelidium pusillum var, pulvinatu m and Caulacan th us ustulatus. Hilden brandia canariensis was found in deep rock crevices, and on more sheltered rocks lacking barnacles a blackish-green gelatinous layer of Entophysalis deusta had developed.

Cap Blanc- west side (site 7) About 1.5 km north of the tip of Cap Blanc, the high cliffs give way to a

sandy beach with sandstone outcrops. Observations were made in this, the most wave-exposed shore studied. Here the Entophysalis deusta crust was thick and formed a wide belt whose upper limit was up to 5 m above the sandy beach. Littorina punctata and L. neritoides penetrated about half way up this belt and extended below it over a rather bare region containing small plants of a Porphyra species and other algae such as the blue-green algae Calothrix crustacea and Entophysalis deusta, especially where there was some shade under rock overhangs. Further down the shore was a fairly well-developed but patchy algal belt dominated by green algae such as UIva lactuca, U. fasciata and Enteromorpha prolifera subsp. prolifera, but also including Gifforida mitchelliae and Porphyra species. Barnacles were poorly developed but some large limpets were present. Finally just above the level of the sand was a narrow belt of Gelidium pusillum. On nearby flatter rocks of the lower midlittoral, which projected above the sandy beach, was a very varied community of often intricately intertwined algae which included Bryopsis corymbosa, Callith- amnion granulatum, Champia parvula, Codium decorticatum, Corallina berterii, Gelidium crinale, Gigartina acicularis, G. pistillata, Gracilaria verrucosa,


Gymnogongrus patens, Hypoglossurn woodwardii, Laurencia pinnatifida, Ophiocladus sirnpliciuscula, Plocamium cartilagineum, Polysiphonia denudata, P. macrocarpa, Pterosiphonia pennata and Rhodymenia pseudopalmata. Graci- laria foliifera mixed with goose barnacles often formed a dense covering on more vertical rocks. Although the sandy beach did not permit the development of a sublittoral fringe the presence of Ecklonia muratii in the drift indicated that a sublittoral community was present in somewhat deeper water.

La Guerra (site 8) Rocky outcrops on the sandy beach in the bay at La Guerra, just north of

the police station, were examined. These rocks received some shelter from the rocky point lying to the west of the bay and are described as only moderately exposed to wave-action. The uppermost algae at this locality were species of blue-green algae such as Calothrix crustacea and Entophysalis deusta which were on flat rocks and at the same level as small snails. Immediately below these blue-greens was a belt of Ulva rigida with some Laurencia pinnatifida and Gelidium pusillurn. Finally, on a very gently sloping rocky platform of the lower eulittoral was a mixed carpet of the following algae: Ceramium rubrum, Corallina berterii, Gelidium crinale, G. sesyuipedale, Gigartina acicularis, G. teedii, Gracilaria foliifera, G. verrucosa, G-vmnogongrus patens, Hypnea rnusciformis, H. spinella, Erythroglossum schousboei, Ophiocladus sirnpliciuscula, Plocamium cartilagineum, Pterosiphonia pennata, Rhody menia pseudopalmata and Spatoglossum schroederi. Attached plants of Ecklonia rnuratii and Codium decorticatum, indicating a sublittoral fringe, were found at the extreme outer limit of the rocky platform. Both of these species were richly covered by epiphytes, Giffordia rallsiae and Griffithsia species on the former and Ceramium rubrum, Erythrocladia irregularis, Erythrotrichia boryana, Colaconema humilis and Polysiphonia denudata on the latter.

General features of zonation

The littoral fringe was characteristically populated by littorinids and, where there was sufficient spray or shade to allow it to survive, by a blackish crust of the blue-green alga Entophysalis deusta. We did not find any species of the characteristic Bostrychia-Murrayella-Lophosiphonia community found on rocks in the littoral fringe in many other parts of the West African coast. This may possibly be attributed to the fact that prevailing climatic conditions cause extreme desiccation of algae, expecially in the higher zones on the shore during periods of low water.

The eulittoral zone could generally be divided into two subzones, an upper subzone dominated by barnacles and a lower subzone dominated by algae. The barnacle subzone was generally poor in algae but in sheltered parts contained Enteromorpha spp., Gelidium pusillurn, especially in cracks in the rocks, and in more exposed parts a few plants of Porphyra. In wave-sheltered places the lower subzone was covered by a short turf of red algae, mostly of Gelidium pusillurn, but mixed with Caulacanthus ustulatus where there was somewhat increased wave-action, and including other species such as Gigartina acicularis, Bachelotia antillarum and Ulva lactuca at the lower levels. In some places the

108 C. W. LAWSON AND D. M. J O H N

lower subzone itself could be considered as consisting of two subordinate zones with mussels and Corallina berterii characterizing the lower of these. On more wave-exposed shores the lower eulittoral subzone consisted of a very varied community of small species of algae in which no dominant species could be discerned.

The sublittoral fringe was dominated by Sy,yridia, Cjjstoseira and Cymo- docea in sheltered situations but included an undergrowth of such genera as Padina and Amphiuoa. In more wave-exposed places the characteristic components of the community included Ecklonia, Codium and Gracilaria. Sea urchins, usually a common constituent of this zone, particularly in wave- exposed situations, were very infrequent.

DISCUSSION

One of the results of this survey has been t o almost double (from 39 to 6 5 ) the previously known marine algal flora identified to species of former Spanish Sahara. For Mauritania, the algal flora of which was somewhat better-known, the increase is less spectacular but 43 species, including drift plants collected at Nouakchott, have been recorded for the first time, providing a total of 158 species of marine algae now known from that country. The check-list of algal species recorded for the combined coastlines of Mauritania and Western Sahara is now 180 (excluding Cyanophyceae) whilst at least a further 23 plants are identified only to genus.

One of the most striking features of the algal vegetation of the Cap Rlanc peninsula was the very considerable differences found between its eastern and western sides. These include differences both in the structure as well as the composition of the communities found on the two sides. Ninety-seven algae are known from the Cap Blanc peninsula from specific localities; this figure is based on our own records and those given in works such as those of Hariot (1911), Sourie (1954a) and Dangeard (1952). Of this total, 35 species were found exclusively on the west side, 41 were restricted to the eastern side, and only 21 were common to both sides. Two factors are probably chiefly responsible for these differences. On the one hand the western coast is directly exposed to the action of the Atlantic waves whereas the eastern coast faces into the sheltered Baie du Ltvrier. On the other hand the western coastal waters are subjected to the direct effect of cold upwelling whereas in the Baie du Ltvrier these effects are to some degree moderated and the shallow nature of the bay allows insolation to raise the temperature of the water above that of the open sea (see Fig. 2). Probablv the temperature effect is more important than wave-exposure in determining the presence or absence of algae on the two sides of the Cap Blanc peninsula since many of the algal species found on the western side, for instance, are ones which are known only further north o n the coast of North-west Africa and beyond (Fig. 3). This applies to such species as Gigartina pistillata, Gymnogongrus patens and Llictyopteris membranacea. There is also a large percentage of species on the west side (23%) which extend southwards only as far as Stntgal. These include such plants as Hypoglossum woodwardii and Gelidium sesquipedale. The Gulf of Guinea element is little represented (3%) on the western side of the peninsula. On the eastern side, by way of contrast, many species (17%) such as Padina tetrastromatica, Dictyota

MARINE FLORA O F THE CAP BLANC PENINSULA

North of Cap Gulf

Western Blanc S8negal of

Sahara peninsula Guinea

109

I 1

d West

0 side 0 East side

Figure 3. A diagrammatic representation of the proportionate distribution along the West African coast of the algal species found on the eastern and on the western side of the Cap Blanc peninsula. The percentage contribution is indicated b y the widths of the bands.

bartayresii and Solieria tenera, are characteristically found to the south and in the Gulf of Guinea and apparently reach their northernmost limit in the Baie du Ltvrier.

The relations between the algal floras of the two sides of Cap Blanc and their affinities with other regions of West Africa are summarized in Fig. 4. I t appears that about half of the Cap Blanc flora is widely distributed along the West

North Cap Gulf

Western Blanc Senegal of

Sahara peninsula Guinea

I I

Figure 4. A diagrammatic representation of the proportionate distribution along the West African coast of the algal species in the marine flora of the Cap Blanc peninsula. The percentage contribution is indicated by the wiaths of the bands.


African coast, but about 38% of the species are totally absent from the Gulf of Guinea. Less than 10% of the algal flora consists of plants known from the Gulf of Guinea which find their northern limit at Cap Blanc. There is a small element (3%) of algae endemic to the coasts of Mauritania and Stntgal, this includes Cystoseira mauritanica and Rhizenteron saxatile. Cap Blanc represents the southern limit for a number of species (21%) whilst Stntgal is the limit for a further 16.5%.

The study of Sourie (1954a) has shown the transitional nature of the marine algal flora and fauna of the Cap Vert peninsula. Although many northern species find their southern limit in Stntgal and many southern species their northern limit, there is nevertheless a considerable overlap with warm and cooler water species occurring side by side. Our work demonstrates that this transition zone of SknCgal extends through Mauritania t o the Cap Blanc peninsula. Here the few surviving Gulf of Guinea species which penetrate north as far as the Baie du Ltvrier finally disappear on the western side of the peninsula, whilst a great many northern species do not extend any further south than the tip of Cap Blanc. Thus the Cap Blanc peninsula can be regarded as the true boundary between the warm temperate marine algal flora of North West Africa and the sub-tropical transition zone of Mauritania and Senegal to the south. This view receives independent confirmation from the work of Postels (1 968) who, taking into account oceanographic conditions alone, considers Cap Blanc to be the boundary between two oceanographic regions of West Africa. One to the north is characterized by colder water throughout the year and the other region to the south is where the water is seasonally warmed and cooled.

ANNOTATED SPECIES LIST

The following list includes all earlier records of algae specifically mentioned as occurring in Western Sahara (assuming. territorial limits prior to 1958) and Mauritania in addition to our own collections from the Cap Rlanc peninsula. Sites at which collections and observations have been made are referred to by number only, following the name and authority. A few plants collected in the drift at Nouakchott are also included.

Baie de 1’Etiole 1 Cansado 5 Pointe de 1’Etiole- Cap Blanc-east side 6 Pointe des Maures 2 Cap Blanc-west side 7 Lagoon 3 La Giierra 8 Nouadhibou 4 Nouakchott 9

All specimens are deposited in the Ghana Herbarium (GC) at the Department of Botany of the University of Ghana, Legon, Ghana.

Chlorophyceae Bryopsis corymbosa J . Ag. 7 Bryopsis plumosa (Huds.) C. Ag. 7

Mauritania: Gayral (1966). Very small plants growing among other algae and having a roughly triangular outline to the

frond are assigned to this species. The main branches were more robust (up to 5 0 0 p m in diam.) than is usual for this species.

Mauritania: Seoane-Camba (1960). Caulerpa crassifolia (C. Ag.) J. Ag.

MARINE FLORA O F THE CAP BLANC PENINSULA 111

Caulerpa cupressoides (West ex Vahl) C. Ag. Mauritania: Feldmann (1951).

Caulerpa taxifolia (Vahl) C. Ag. Mauritania: Feldmann (1951).

Chaetomorpha brachygona Harv. 1 Mauritania: Dangeard (1952), Feldmann (1 9 38a), Trochain (1 940).

7 Western Sahara: Primo (1953) as Chaeto- morpha aerea.

Cladophora fascicularis (Mert.) Kiitz. Mauritania: Feldmann (1946). See Lawson & Price (1969) for comments on the status of this taxon.

Cladophora prolifera (Roth) Kutz. 2 Cladophora spp. 2 3

Mauritania: Sourie (1954a). A number of unidentifiable fragments of species of this genus were found in several of our collections.

Codium decorticatum (Woodw.) Howe 5,7,8 Mauritania: Hariot (1911), Schmidt & Gerloff (1957) as C. elongatum. Western Sahara: Primo (1953) as C. elongatum.

Codium tomentosum Stackh. 2 Mauritania: Gayral (1966), Hariot (1911), Schmidt & Gerloff (1957).

Mauritania: Sourie (1954a). Derbesia furcellata (Zanard.) Ardiss 2

Our Mauritanian material appears to correspond in branching and dimensions to the plants described and figured as Pseudochlorodesmus furcellata (Zanard.) Bdrg. for the Canary Islands by Bdrgesen (1925, figs 30-34). It should be noted that Sourie (1954a) mentions a new species of Derbesiu found in Mauritania, Senkgal and neigh-

Chaetomorpha linum (0. F. Mull.) Kiitz.

Codium spp.

bouring islands, which was to have been described by J. Feldmann under the name D. souriei. As far as we can ascertain, no description has yet appeared in print.

Enteromorpha clathrata (Roth) Grev. 1 Enteromorpha flexuosa (Wulf ex Roth) J.

Enteromorpha intestinalis (L.) Link subsp.

Western Sahara: Primo (1953) as E. compressa. subsp. intestinalis 1,4,7

Enteromorpha prolifera (0. F. Miill.) J . Ag. subsp. prolifera J . Ag. 437

Enteromorpha spp. 1,4,5,7,8 Small fragments attributable to this genus were found in many of our collections.

Phaeophila viridis (Reinke) Burrows 5 Epiphytic on fragments of a Codium found in the drift.

Mauritania: Sourie (1954a).

Ag. subsp. flexuosa 475

compressa Silva & Burrows

Rhizenteron saxatile Dang.

Rhizoclonium africanum Kutz. 1 Rhizoclonium implexum (Dillw.) Kiitz 1 ,2 Siphonocladus tropicus (Crouan frat.) J. Ag.

Mauritania: Feldmann (1946, 1951). Struvea anastomosans (Harv.) Piccone &

Mauritania: Steentoft (1967) with doubt. Ulva fasciata Delile 7

Mauritania: Steentoft (1967). Ulva lactuca L. 597

Mauritania: Hariot (1911), Schmidt & Gerloff (1957), Steentoft (1967). Western Sghara: Primo (1953).

Grunow

Ulva rigida C. Ag. 8 Ulva spp. 4,7


Phaeophy ceae

Bachelotia antillarum (Grun.) Gerloff 2,s Bifurcaria bifurcata Ross

Western Sahara: Primo (1953), Sourie (1954a) as B. tuberculata.

2,s Mauritania: Lawson (1966), Sourie (1954a); Dickie (1874) as Asperococcus sinuosus.

Mauritania: ArdrC (1970). Gayral (1966), Roberts (1967), Sauvageau (1912); Hariot (1911), Roberts (1967), Sauvageau (1912) as C. fibrosa. Western Sahara: Sourie (1954a) as C. fibrosa.

Mauritania: Hariot (1911) with doubt, Sauvageau (1912, 1920), Schmidt & Gerloff (1957) as C. discors. Western Sahara: Sourie (1954a) as C. abrotani- folia.

Colpomenia sinuosa (Roth) Derb. & Sol.

Cystoseira baccata (S. G. Gmel.) Silva

Cystoseira foeniculacea ( L.) Grev.

Cystoseira humilis Kutz. var. humilis

Cystoseira mauritanica Sauv. Mauritania: Ardrk (1970) as C. humilis.

Mauritania: Dangeard (1937, 1938, 1949, 1952), Hariot (1911), Sauvageau (1912), Schmidt & Gerloff (1957); Sauvageau (1920) as C. tingitana.

Mauritania: Gayral (1966).

Mauritania: Dangeard (1938, 1949, 1952), Seoane-Camba (1960) as C. granulata.

Mauritania: Ardre (1970), Gayral (1966), Roberts (1970); pdrgesen (1926), Hariot (1911), Sauvageau (1912, 1913), Schmidt & Gerloff (1957) as C. ericoides. Western Sahara: Sourie (1954a) as C. ericoides.

Cystoseira myriophylloides Sauv. 9

Cystoseira nodlcaulis (With.) Roberts

Cystoseira tamariscifolia (Huds.) Papenf. 192


Cystoseira spp. 1,9 Mauritania: Lawson (1966), Michanek (1971, 1975), Nizamuddin (1970), Sourie (1954a), Southward (19 58), Stephenson & Stephenson (1972). Western Sahara: Feldmann (1951). Primo (1953).

This plant was found only in the drift a t Nouakchott and this appears to be the most northerly record of its distribution in West Africa.

Mauritania: ArdrP (1970), Gayral (1966), Seoane-Camba (1 960).

Western Sahara: Kodriques (1960) as D. barta yresiana. We attach some doubt to our determination as the Mauritanian plants showed less divergent branching than is usually found in this species.

2 Western Sahara. Rodriques (1960) as D. ciliata.

Mauritania: Feldmann (1951).

Mauritania: ArdrP (1970), Gayral (1966).

Mauritania: Lawson (1966), Sourie (1954a), Southward (1958).

Mauritania: Ardrk (1970), Gayral (1966).

Mauritania: Schmidt & Gerloff (1957) as E. radiata; Hariot (1911) as E. radiata var. exasperata.

Ecklonia muratii J. Feldm. 7 , s Mauritania: Bodard & Mollion (1974), Dangeard (1952, 1958), Feldmann (1937. 1951)’ Lawson (1966), Michanek (1971,19751, Sourie (1954a, 1954b), Stephenson & Stephenson (1972). Western Sahara: Feldmann (1937, 1946, 1951), Lawson (1966), Sourie (1954a).

Ecklonia sp. Mauritania: Southward ( 1 9 5 8).

Ectocarpus siliculosus (Dillw.) Lyngb. Mauritania: Hariot (1911), Schmidt & Gerloff (1957).

Feldmannia irregularis (Kutz.) Hamel 2,4,5 Fucus spiralis L.

Western Sahara: Feldmann (19 S l ) , Michanek (1971, 1975), Primo (1953); Sourie (1954a) as F. platycarpus.

Fucus spp. Western Sahara: Michanek (1971, 1975), Primo (1953).

Mauritania: Schmidt & Gerloff (1957); Hariot (1911), Schmidt & Gerloff (1957) as Ectocarpus granulosus.

Ciffordia mitchelliae (Haw.) Hamel 497 Ciffordia rallsiae (Vickers) W . R. Taylor 8

The plants from Western Sahara closely correspond to this species although the somewhat

Dictopteris delicatula Lamour. 9

Dictopteris membranacea (Stackh.) Batt

Dictyota bartayresii Lamour. 1

Dictyota citiolata Sonder ex Kutz.

Dictyota crenulata J . Ag.

Dictyota dichotoma (Huds.) Lamour. 132

Dictyota spp.

Dilophus spiralis (Mont.) Hamel

Ecklonia biruncinata (Bory) Papenf.

Ciffordia granulosa (Sm.) Hamel

tapering plurilocular sporangia were smaller than the dimensions normally given for it, ranging from 50-70pm in length and about 20 prn in diameter.

Laminaria ochroleuca Pyl. Mauritania: Michanek (1975). Western Sahara: ArdrP (1970), Boney (1965), Feldrnann (1955), Michanek (1971, 1975), Primo (1953).

Mauritania: Sourie (1954a). Western Sahara: Primo (1953), Sourie (1954a).

Leathesia difformis (L.) Aresch. Mauritania: Ardrk (1970) , Gayral (1966).

Levringea atlantica (J. Feldm.) Kylin Mauritania: Gayral (1960); Feldmann (1938b) as Myriogloea atlantica. Western Sahara: Dangeard (1952), Feldmann (1946, 1951), Gayral (1960). Kylin (1940); Feldmann (1938b) as Myriogloea atlantica; Levring (1 9 39) as Myriogloia atlantica.

Mauritania: Sourie (1954a) as Pocockiella variega ta. Western Sahara: Rodriques (1960) as Pocockiella variegata.

Padina pavonia (L.) Lamour. Mauritania: ArdrP (1970), Bodard & Mollion (1974), Gayral (1966), Hariot (1911) , Schmidt & Gerloff (1957).

Padina tetrastromatica Hauck 2 Drift specimens of this species were unusual in that older parts of the fronds had concentric rows of flattened fusiform leaf-like structures, up t o about 1 mm long and about one quarter as broad, growing in the position normally occupied by sporangia. They appeared to arise from superficial cells of the thallus and the fact that they could easily be detached suggests the possibility that they may function as vegetative propagules.

Padina vickersiae Hoyt 2,9 Padina sp.

Mauritania: Lawson (1966), Sourie (1954a). Phyllaria reniformis (Lamour.) Rostafinski ex

Laminaria spp.

Lobophora vanegata (Lamour.) Womersley

Born. Western Sahara: Feldmann (1951).

Pilayella littoralis (L.) Kjellm. Mauritania: Gayral (1966).

Mauritania: Sourie (1954a). Saccorhiza polyschides (Lightf.) Batt.

Mauritania: Michanek (1975). Western Sahara: ArdrP (1970), Boney (1965), Gayral (1966), Michanek (1971, 1975), Norton (1970); Primo (1953), Feldmann (1951) as S. bulbosa.

Mauritania: Hariot (1911) as S. linifolium.

Mauritania: Hariot (1911), Hoppe (1969), Levring (1969), Seoane-Camba (1960), Steentoft (1967). Western Sahara: Primo (1953).

Ralfsia expansa (J. Ag.) J . Ag. 5

Sargassum acinarium (L.) C . Ag.

Sargassum vulgare C. Ag. 2,9

MARINE FLORA O F THE CAP BLANC PENINSULA 1 1 3

Sargassum sp. Sphacelaria furcigera Kiitz. 9 Mauritania: Seoane-Camba (1960), Southward (1958). Mauritania: ArdrC (1970), Gayral (1966).

8,9 Lawson (1966), Sourie (1954a). Stephenson & Stephenson (1972).

Taonia atomaria (Woodw.) J. Ag.

Spatoglossum schroederi (C. Ag.) Kiitz. Spatoglossum solieri (Chauv. ex Mont.) Kiitz.

Mauritania: Bodard & Mollion (1974).

Rhodoph yceae Acrosorium uncinatum (Turn.) Kylin

Mauritania: Seoane-Camba (1960), Trochain (1940). Western Sahara: Ardrt (1970), Gayral (1966).

Amphiroa annulata Lemoine 2 Amphiroa fragilissima (L.) Lamour. 2 Amphiroa subcylindrica Dawson 2

This species has not previously been reported outside the Pacific region.

Apoglossum ruscifolium (Turn.) J. Ag. Western Sahara: Ardrt (1970), Gayral (1966).

Audouinella purpurea (Lightf.) Woelkerling Mauritania: Dixon & Irivine (1977).

Audouinella secundata (Lyngb.) Dixon Mauritania: Dixon & lrvine (1977).

AoudouineIla seriatum (BBrg.) Lawson & John, comb. nov. (Achrochaetium seriatum Borg.) 4 In making this new combination we have followed Dixon (Parke & Dixon, 1976) who has placed several genera of acrochaetoid algae occurring in the British Isles into a single genus Audouinella. He argues that there seems no logical reason for delineating genera in this closely interrelated group in which the circum- scription of species is often confused.

Audouinella virgatula (Harv.) Dixon Mauritania: Dixon & Irvine (1977).

Bostrychia binderi Harv. 4 A single fragment found entangled with filaments of Enteromorpha.

Mauritania: Dixon & Irvine (1977), Gayral (1966), Hariot (1911).

Mauritania: Ardrk (1970), Dixon & Irvine (1977), Gayral (1966).

Mauritania: Halos (1965) as Aglaothamnion decompositum.

According to J. H. Price (in litt., 25.5.76) this material collected from the west side of Cap Blanc may be an undescribed species.

Caulacanthus ustulatus (Mert.) Kutz. 5,6,7 Mauritania: Lawson (1966), Sourie (1954a).

Centroceras clavulatum (C. Ag.) Mont. 2 Mauritania: Lawson (1966), Sourie (1954a), Stephenson & Stephenson (1972).

Ceramium diaphanum (Lightf.) Roth Mauritania: ArdrC (1970), Gayral (1966).

Ceramium gracillimum (Kiitz.) Griff. & Harv. variety byssoideum (Harv.) Mazoyer 1,2,8,9

8 This species has not previously been reported further south than Morocco on the West African coast.

Calliblepharis ciliata (Huds.) Kutz.

Calliblepharis jubata (Good. & Woodw.) Kiitz.

Calliihamnion decompositum J. Ag.

Callithamnion sp. 7

Ceramium rubrum (Huds.) C . Ag.

8

Ceramium strictum Harv. 2 Ceramium spp. 7-8

Mauritania: Sourie (1954a). Champia parvula (C. Ag.) Harv. 2,7,8 Chondria dasyphylla C. Ag.

Chondria scintillans G . Feldm.

Chondria tenuissima (Good. & Woodw.) C. Ag.

Chondria spp.

Chondrus crispus Stackh.

Choreonema thuretii (Born.) Schmitz

Colaconema humilis (Rosenv.) Woelkerling 8 Corallina berteri Mont. 5,7,8 Corallina mediterranea Aresch.

Mauritania: Ardrb (1970), Gayral (1966), Hariot (1911). Western Sahara: Primo (1953).

Corallina officinalis L. Mauritania: ArdrC (1970), Gayral (1966).

Corallina sp, Mauritania: Sourie (1954a).

Cryptonemia seminervis (C. Ag.) J. Ag. Mauritania: Bodard (1971), Hariot (1911).

Cryptopleura ramosa (Huds.) Kylin ex Newton Western Sahara: ArdrC (1970). Gayral (1966).

Dermatolithon cystoseirae (Hauck) Huvk Mauritania: Huvk (1962). Lemoine (1965, 1966); Ardrk (1970) as D. cystoseirae var. saxicola; Hamel & Lemoine (1953) as D. papillosum.

Mauritania: Lemoine (pers. comm.) .

Mauritania: Seoane-Camba (1960).

Mauritania: Ardrk (1970), Feldmann (1964).

Western Sahara: Ardrb (1970), Gayral (1966).


Mauritania: Hariot (191 1).

Mauritania: Hariot (1911).

Dermatolithon polydonum Fosl.

Erythrocladia irregularis Rosenv. 8 Erythroglossum schousboei J. Ag. 8 Erythrotrichia boryana (Mont.) Berth. 7.8 Erythrotrichia carnea (Dillw.) J. Ag. 1 3 Fosliella farinosa (Lamour.) Howe 9

Mauritania: John & Lawson (1972); Hariot (1911) as Melobesia farinosa.

Mauritania: Ardrk (1970), Gayral (1966). 2,9

Mauritania, Feldmann (1951), Steentoft (1967).

Western Sahara: Ardre (1970), GayraI (1966); Michanek (1971, 1975). Primo (1953) as G. attenuatum.

Western Sahara: Michanek (1971, 1975), Primo (1953) as G. spinulosum.

Gastroclonium ovatum (Huds.) Papenf.

Celidiopsis variabilis (J. Ag.) Schmitz

Gelidium Iatifolium (Grev.) Born. & Thur.

Gelidium microdon Kiitz.


Gelidium pusillum (Stackh.) Le Jol. 4,8 Mauritania: Sourie (1954a) with doubt; Hariot (1911), Schmidt & Gerloff (1957), Steentoft (1967) as G. crinale. Western Sahara: Primo (1953) as G. crinale.

2,4,7,8 Mauritania: Dangeard (1951, 1952) as G. rep tans. We concur with BQrgesen (1943) in considering Gelidium reptans to be no more than a variety of G. pusillum even though it has been given specific rank by some others.

8 Mauritania: Ardrk (1970), Dangeard (1952), Dixon & Irvine (1977), Gayral (1966), Hariot (1911), Schmidt & Gerloff (1957). Western Sahara: Michanek (1971, 1975), Primo (1953).

Gelidium spp. Mauritania: Sourie (1954a). Western Sahara: Michanek (1971, 1975), Primo (1953).

Gigartina acicularis (Wulf.) Lamour. 2,7,8 Mauritania: Ardrk (1970), Gayral (1966), Hariot (1911), Schmidt & Gerloff (1957), Sourie (1954a).

7 Mauritania: Ardre (1970), Hariot (1911), Schmidt & Gerloff (1957), Sourie (1954a). Western Sahara: ArdrC (1970).

Gigartina stellata (Stackh.) Batt. Mauritania: Dizerbo (1974). Western Sahara: ArdrC (1970), Gayral (1966).

Gigartina teedii (Roth) Lamour. 8 Mauritania: Lawson (1966), Sourie (1954a) with doubt.

var. pulvinatum (C. Ag.) J. Feldm.

Gefidium sesquipedale (Clem.) Born. & Thur.

Gigartina‘pistillata (S. G. Gmel.) S t a c b .

Goniotrichum alsidii (Zanard.) Howe 4 Gracilaria armata (C. Ag.) J. Ag.

Mauritania: Hariot (1911). Gracilaria bursa-pastoris (S. G. Gmel.) Silva

Mauritania: Hariot (1911) as G. compressa. Gracilaria foliifera (Forssk.) BQrg. 7 3

Mauritania: Lawson (1966), Michanek (1971, 1975), Sourie (1954a); Hariot (1911) as G. multipartita.

Gracilaria verrucosa (Huds.) Papenf. 7 3 Mauritania: ArdrC (1970), Steentoft (1967); Hariot ( 19 11 ) as G. confervoides. Western Sahara: Ardrk (1970). Gayral (1966); Primo (1953) as G. confervoides.

Mauritania: Southward (1958). Western Sahara: Michanek (1971, 1975). Primo (1953).

Grateloupia doryphora (Mont.) Howe Mauritania: Sourie (1954a) as G. lanceola.

Grateloupia filicina (Lamour.) C. Ag. Mauritania: ArdrC (1970), Gayral (1966).

Griffithsia sp. 8 The specimens from Western Sahara had branches consisting of large, obovoid to harrel- shaped cells and closely correspond in vegetative structure to Griffithsia schousboei and G. opuntioides. It is not possible to attribute our specimens to either of these species as all the

8

Gracilaria spp.

plants were sterile and they are separated on the position of the spermatangial sori.

Mauritania: Dixon & lrvine (1977); ArdrC (1970). Gayral (1966), Hariot (1911). Schmidt & Gerloff (1957) as G. norvegicus.

Gymnogongrus griffithsiae (Turn.) Mart. Mauritania: Dixon & Irvine (1977), Hariot (1911), Schmidt & Gerloff (1957).

Gymnogongrus patens (Good. & Woodw.) J . A.g7,8 Mauritania: Gayral (1966).

Haliptylon squamatum (L.) Johansen, L. Irvine &

Western Sahara: Ardrk (1970), Gayral (1966) as Corallina squamata.

2

Mauritania: Ardrk (1970), Gayral (1966); Hariot (1911) as H. pinastroides.

Halurus equisitifolius (Lightf.) Kiitz. Mauritania: ArdrC (1970), Gayral (1966), Sourie (1954a).

2,4,5

Gymnogongrus crenulatus (Turn.) J. Ag.

Webster

Haliptylon subulata (Ellis & Soland.) Johansen Halopitys incurvus (Huds.) Batt. 9

Herposiphonia tenella (C. Ag.) Ambronn

Heterosiphonia plumosa (Ellis) Batt.

Heterosiphonia wurdemanni (Baily ex Harv.)

var. subsecunda Hollenberg 2

Western Sahara: Ardre (1970), Gayral (1966).

Fa1 ke nb . 9

Hildenbrandia canariensis BQrg. 6 Mauritania: ArdrC (1970). The plants reported under this name formed thick, reddish-violet crusts which superficially resemble a Peyssonnelia. I t differs from H. prototypus by its thick crust, very immersed conceptacles, and the tetrasporangia divided by almost parallel walls.

Hypnea cervicornis J. Ag. Mauritania. Bodard (1968).

Hypnea flagelliformb Grev. ex J. Ag. Mauritania: Bodard (1968).

Hypnea musciformis (Wulf.) Lamour. 2,7,8,9 Mauritania: Bodard (1968), Hariot (1911), Hoppe (1969), Seoane-Camba (1960), Steentoft (1967).

Hypnea spinella (C. Ag.) Kiitz. 8 Hypnea unilateralis Dang.

Mauritania: Bodard (1968). Western Sahara: Bodard (1968).

Mauritania: Bodard (1968) as “Hypnea sp. (aff. ceramioides)”.

Western Sahara: ArdrC (1970), Gayral (1966), Seoane-Camba (1960).

Jania adhaerens Lamour. 2 Jania longifurca Zanard.

Mauritania: Feldmann (1939), Hariot (1911), Seoane-Camba (1965).

Jania rubens (L.) Lamour. 2 Mauritania: Ardri (1970), Gayral (1966). Hariot (1911).

Mauritania: Seoane-Camba (1960) with doubt.

var. laxa BQrg. 2

Hypnea sp

Hypoglossum woodwardii Kiitz.

Laurencia flexuosa J. Ag.

MARINE FLORA O F THE

Laurencia obtusa (Huds.) Lamour. 2 Mauritania: Hariot (1911).

Laurencia pinnatifida (Huds.) Lamour. 7.8 Mauritania: Ardre (1970), Dangeard (1952), Gayral (1966), Hariot (1911), Lawson (1966), Sourie (1954a), Steentoft (1967).

Mauritania: Stephenson & Stephenson (1972).

Mauritania: Lemoine (1963) as Lithothamnium bisporum.

Mauritania: Hariot (1911) as Melobesia corallinae.

Lithophyllum haucki (Rothplatz) Lemoine Mauritania: Feldmann (1939).

Lithophyllum incrustans Phil. Mauritania: Adey & Adey (1973), Ardrh (1970), Feldmann (1939), Gayral (1966), Hamel & Lemoine (1953), Hariot (1911), Seoane-Camba (1965). Western Sahara: Adey & Adey (1973).

Lithophyllum lobatum Lemoine Mauritania: Lemoine (1963).

Lithophyllum tortuosum (Esper) Huve Mauritania: Sourie (1954a).

Lithoporella conjuncta (Fosl.) Fosl. Mauritania: De Toni (1924), Foslie (1909), Foslie & Printz (1929); Lemoine (1963) as L. melo besioides.

Lithothamnium fruticulosum (Kiitz.) Fosl. Mauritania: Lemoine (1963).

Lithothamnia sp. Western Sahara: Primo (1953).

Lomentaria articulata (Huds.) Lyngb. Western Sahara: ArdrC (1970), Gayral (1966).

Lomentaria bayleyana (Harv.) Farlow Mauritania: Seoane-Camba (1960).

Melobesia membranacea (Esper) Lamour. Mauritania: Hariot (191 1) as Lithothamnion membranaceum.

Mauritania: Bdrgesen (1929), De Toni (1924), Foslie (1907), Foslie & Printz (1929), Lemoine (1963) as Lithothamnium ectocarpon.

Mesophyllum lichenoides (L.) Lemoine Mauritania: Ardrb (1 970). Western Sahara: Gayral (1966).

Mesophyllum solutum (Fosl.) Lemoine Mauritania: Lemoine (1963); Hariot (1911) as Lithothamnion solutum.

Nemalion helminthoides (Vell.) Batt. Western Sahara: Primo (1953).

Neogoniolithon mamillosum (Hauck) Setch. &

Mauritania: De Toni (1924) as Goniolithon mamillosum form microcarpa.

Ophidocladus simpliciuscula (Crouan frat.) Falkenb. 2,733

Cap Blanc represents a new southern limit for this species.

Phymatolithon calcareum (Pall.) Adey & McKibbin Mauritania: Bdrgesen (1929), Lemoine (1928) as Lithothamnion calcareum.

9

Laurencia spp.

Leptophytum bisporum (Fosl.) Adey

Lithophyllum corallinae (Crouan frat.) Heydr.

Mesophyllum ectocarpon (Fosl.) Adey

Mason

Platysiphonia miniata ( C . Ag.) Bdrg.

CAP BLANC PENINSULA 115

Plocamium cartilagineum (L.) Dixon 7,s Mauritania: ArdrC (1970), Gayral (1966), Hariot (1911) as P. coccineum.

Plocamium raphelisianum Dang. 223 Pterosiphonia pennata (C. Ag.) Falkenb. R hodymenia corallicola Ardiss.

2,7,8

Mauritania: Hoppe (1969), Seoane-Camba (1 960).

Rhodymenia pseudopalmata (Lamour.) Silva 7,8 Mauritania: Hariot (191 1) as R . palmetta.

9 Mauritania: ArdrC (1970). Gayral (1966), Seoane-Camba (1960).


Mauritania: Feldmann (1951), Hariot (1911) as Agardhieila tenera.

7,8 Mauritania: Seoane-Camba (1960) as P. variega ta. Some doubt attaches to this identification since the Cap Blanc plants grew o n open wave- exposed shores whereas this species is usually reported from sheltered and more brackish water localities. The plants referred to this species had 6 pericentral cells surrounding a very small axial cell and cortication developing towards the base of the larger branches. The segments near the base of the branches were up to 450pm in diameter, narrowing towards the apex of the branches and were generally shorter than broad. Cystocarps borne on the upper branches were sessile or o n a 1-celled stalk, obovate and from 3 S(t400 p m in diameter.

Polysiphonia macrocarpa Harv. Z7-8 On a number of occasions a sterile 4 pericentral-celled plant was found which has tentatively been placed under this species.

Polysiphonia spp. 5,7,8 Small unidentifiable fragments probably refer- rable to this genus have been found in a number of collections.

Porphyra sp- 7 This small Porphyra had fronds oblong in outline, plicate, and with a dentate margin. In section the fronds were about 40 p m thick with two layers of cells, each cell was about 16 pm in height and 10pm in diameter in surface view.

Mauritania: Lemoine (1963) as Lithophyllum a fricanum.

Mauritania: Bdrgesen (1929), Edelstein (1964), Feldmann (1939), Gayral (1958); Hariot (1911) as Lithophyllum expansum form exigua.

Pterocladia capillacea ( S . G. Gmel.) Born. & Thur. Mauritania: Feldmann (1939), Lawson (1966), Sourie (1954a). Western Sahara: Ardrc? (1970), Gayral (1966).

Mauritania: Ardrh (1970), Gayral (1966).

Rytipholea tinctoria (Clem.) C. Ag.

Solieria chordalis (C. Ag.) J. Ag.

Solieria tenera (1. Ag.) Wynne & W. R. Taylor

Polysiphonia denudata (Dillw.) Grev. ex Harv.

Povolithon africanum (Fosl.) Fosl.

Pseudolithophyllum expansum (Phil.) Lemoine

Pterosiphonia complanata (Clem.) Falkenb.


Spyridia filamentosa (Wulf.) HaN.

Spyndia hypnoides (Bory ex Belanger) Papenf. 2,9

Mauritania: Feldmann (1938), Steentoft (1967) with doubt as S. aculeata; Dangeard (1952) as S. aculeata variety hypnoides.


Cyanophy ceae

Entophysalis conferta (Kutz.) Dr. & D. 5 Schizothrix arenaria (Berk.) Gom. 5

Microcoleus lyngbyaceus (Kutz.) Crouan frat. ex Schizothnx tenerrima (Gom.) Dr. 4

Calothrix crustacea Thur. ex Born. & Flah. 4 ,5 ,7 ,8

Entophysalis deusta (Menegh.) Dr. & D. 2,4,5,6,7,8

Gorn. 3,4,5,7,8

Porphyrosiphon notarisii (Menegh.) Kutz. ex Gom.4

Schizothrix calcicola (C. Ag.) Gom. ex Gom. 3,5,6,8

ACKNOWLEDGEMENTS

The field work for this study was supported by a UNESCO grant. Thanks are due to Monsieur Paul Piesson, Laboratoire de Geologie, Louvain-La-Neuve, Belgium and Herr. Hans Moln, Voest-Alpine, Nouadhibou, Mauritania, for their assistance in the field; to Sy Moussa Arouna, Le Directeur, Laboratoire des Ptches, Nouadhibou, for providing us with unpublished data; to Dr F. Drouet and Mr E. Anderson, Academy of Natural Sciences of Philadelphia, U.S.A., to Dr Helen Blackler, Department of Botany, University of St Andrews, Scotland, and to Dr H. W. Johansen, Department of Biology, Clark University, Massachusetts, U.S.A., for assistance in identifying specimens; to Mr J . H. Price, Botany Department, British Museum (Natural History), London, for invaluable assistance with the literature; and t o Professor G. C. Clerk, Head of the Botany Department, University of Ghana, Legon, for allowing us facilities in his Department.

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The marine flora of the Cap Blanc peninsula: its distribution and affinities

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