SCI. MAR., 66 (Suppl 3): SCIENTIA MARINA 2002 Marine benthic algae of Namibia* JORDI RULL LLUCH Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s/n. 08028 Barcelona. Spain. E-mail: [email protected] SUMMARY: The first comprehensive study of the marine algal flora of Namibia including descriptions and illustrations of most species is presented. The main objective of this work is to report a flora that, until now, has scarcely been studied. The work compiles all the available information on the marine benthic flora of Namibia and provides new data about it compo- sition and biogeography, as well as detailed descriptions and remarks of most of its species. The samples on which this study is based were collected between 1986 and 1989 in the eulittoral and the upper sublittoral zones of the north half of the Namibian coast. According to the present data, the marine benthic flora of Namibia comprises 196 taxa (147 Rhodophyceae, 20 Phaeophyceae, 15 Ulvophyceae, 6 Cladophorophyceae and 8 Bryopsidophyceae), 21 of which has not been recorded from this coasts. This temperate flora is mainly characterized by a low number of species, a low proportion of Phaeophyceae and a high degree of endemism. Concerning the species number, the flora is quite poor due to both the scarce availability of colonizable substratum and the low diversity of habitats. On the other hand, the low proportion of Phaeophyceae is the reason for which the R/P and (R+C)/P ratios take disproportionately high values and so they are not useful in this geo- graphical area. As regards the degree of endemism, the marine benthic flora of Namibia includes quite a high number of taxa endemic to southern Africa (55 taxa; 28.1% of the flora); 25 of these 55 taxa (12.8% of the flora) are endemic to the biogeographic Benguela Marine Province and only Acrosorium cincinnatum is endemic to the Namibian coasts. Key words: Namibia, marine algae, morphology and anatomy, distribution, biogeography, taxonomy, check-list. RESUMEN: ALGAS BENTÓNICAS MARINAS DE NAMIBIA. – Este trabajo recoge toda la información existente hasta el momen- to sobre la flora bentónica marina de Namibia y proporciona nuevos datos sobre su composición y biogeografía, además de descripciones detalladas y valoraciones críticas de muchas de sus especies. El trabajo se ha realizado a partir de muestras florísticas recolectadas entre los años 1986 y 1989 en las zonas eulitoral y sublitoral superior de la costa de la mitad norte del país, entre Walvis Bay y la desembocadura del río Kunene. Según los datos actuales, la flora bentónica marina de Nami- bia está representada por 196 táxones (147 Rhodophyceae, 20 Phaeophyceae, 15 Ulvophyceae, 6 Cladophorophyceae y 8 Bryopsidophyceae), 21 de los cuales no habían sido citados hasta el momento de las costas de este país. Se trata de una flora de carácter templado que se caracteriza principalmente por el bajo número de especies, la escasa proporción de feofíceas y el elevado grado de endemismo. En cuanto al número de especies, la flora de Namibia es relativamente pobre, debido a la escasa disponibilidad de substrato colonizable y a la baja diversidad de hábitats. Por otra parte, la baja proporción de feofí- ceas hace que los índices R/P y (R+C)/P adopten valores desproporcionadamente elevados, lo que hace que no sean aplica- bles en esta área geográfica. Por lo que se refiere al grado de endemismo, la proporción de táxones endémicos del sur de Africa es bastante elevada (55 táxones; 28.1% de la flora); de estos 55 táxones endémicos, 25 (el 12.8% de la flora) lo son de la Provincia Marina de Benguela y únicamente Acrosorium cincinnatum es endémico de las costas de Namibia. Palabras clave: Namibia, algas marinas, morfología y anatomía, distribución, biogeografía, taxonomía, check-list. INTRODUCTION between the mouth of the rivers Kunene (17º16’S) and Orange (28º30’S). Along this coast the cold Namibia is a country with approximately 1500 Benguela current and the descending warm waters km of coast that stretches in a north-south direction from Angola converge. In addition, the effect of the Benguela current, together with the prevailing *Received October 18, 2001. Accepted September 6, 2002. winds, originate a coastal upwelling system of deep MARINE BENTHIC ALGAE OF NAMIBIA 5 water, cold and nutrient rich, which maintains a gen- It may seem an anachronism to produce a work eral high production during most of the year. The of these characteristics at a time when new tech- combination of both these factors confers to the nologies direct botany to the study of the phyloge- Namibian coast certain ecological features which netic relations between the species, which leads one are particularly interesting. They are mainly respon- to reconsider their taxonomic classification, or to the sible for the temperate climate of this zone, which is implementation of systematic revision of certain included in a tropical area, with its corresponding groups. However, we think this work is justified by biogeographical effects. Although the Namibian the fact that most of the species of Namibian marine coast exhibits such attractive ecological and biogeo- flora are not accurately documented. This often graphical conditions, this zone has been scarcely obliged us to resort to the original descriptions or to studied, at least regarding its marine benthic flora. the classical works. This is mainly due to the inhospitable and inaccessi- ble characteristics of this coast, given that along Historical background much of the coast the desert dunes stretch to the sea. Since the Institut de Ciències del Mar of In spite of its ecological and biogeographical Barcelona had a research project to study the fish- interest, the coasts of Namibia have been scarcely eries of the Austral Africa, we thought it would be studied from the point of view of the marine benthic interesting to start a study in parallel of the marine algae, at least until the 1990s. Until then, the works benthic flora of Namibia. At first, the main purpose that studied exclusively the marine algae of Namib- of this work was to record information about the ia were few and generally very old, such as the ones marine flora of Namibia and consequently to con- by Foslie (1893), Pilger (1908) and Dinter (1919- tribute to filling the gap in the general knowledge of 1928). Among the more recent ones, it is worth men- the flora of the Atlantic African coasts, which was tioning the one by Wynne (1986) and the one by well-known for the countries above Namibia (Law- Rotmann (1987). Wynne (1986) produces a com- son and John, 1987) but less so for the South African mented and illustrated catalogue of the species col- coasts, whence the scattered information was com- lected near Swakopmund during a short stay at that piled into a catalogue by Seagrief (1984). site. Rotmann (1987), in contrast, comments on the Shortly after our last collecting campaign, Law- exploitation of Gracilaria verrucosa at Lüderitz Bay son et al. (1990) gathered the sparse information and studies its farming possibilities in this geo- about the marine benthic flora of Namibia (mainly graphical area. It is also important to point out that unpublished and originating from a campaign car- during this period (in 1957) there was a field excur- ried out in 1957) in a paper which includes a cata- sion organized by Professor W.E. Isaac, of the logue of the flora, as well as a description of the Department of Botany of the University of Cape zonation in two coastal areas and data about the Town, to collect seaweeds from the Namibian biogeography. This led us to modify the main pur- coasts. However, it is also noteworthy that the results pose of our work in order to highlight the descrip- from this campaign were not published until 1990, in tion of the species, which was not covered in the a work about the marine algal flora of Namibia work of Lawson et al. (1990) and, until recently, (Lawson et al., 1990). During this period, several neither in most studies about South African flora, papers refer to these data citing them as Simons with which that of Namibia shares a great number (1973, unpublished list) and Lawson and Isaac of species. (1982, unpublished manuscript). Although works This work is not meant to be an exhaustive study that specifically study the marine flora of Namibia of the marine benthic flora of Namibia, but aims to are scant, it is also true that information about lay the foundations for carrying out such a work in marine algae of this country can be found in mainly the future. In contrast, it is meant to offer a compi- faunal works or in studies that focus on South lation of all the information available up to this African marine algae, or from other geographic moment about this subject and to contribute to the areas, as well as in ecological or biogeographical knowledge of the marine benthic flora of Namibia. works. Among the studies about fauna it is worth In this way, we supply new data about its composi- mentioning those by Penrith and Kensley (1970a and tion and biogeography, as well as detailed descrip- b) that study the zones of Lüderitz and Rocky Point tions and critical remarks about many of the species respectively, and the one by Kensley and Penrith that form it. (1980) that studies the zone comprised between 6 J. RULL LLUCH False Cape Frio and the Kunene river mouth. In on the morphology of Laminaria schinzii (Molloy these works the authors describe the vertical distrib- and Bolton, 1996a) or on the growth of Gracilaria ution of algae and animals based on transects from gracilis (Molloy and Bolton, 1996b).