Aquiatic macrophytes in Doñana protected area (SW Spain).

INTRODUCTION A large portion of the Doñana protected area (Fig. 1) is composed of wetlands. In these ecosystems, aquatic macrophytes are responsible for most primary production and also play an important role in increasing ecosystem structures or recycling nutrients and elements. Aquatic macrophytes are, therefore, key elements in this paradigmatic natural area. Moreover, flora is one of the best natural sources of information regarding current and potential conservation in any natural place. The scarce number of studies on this conspicuous group of organisms is thus surprising. When the last Doñana Floristic Catalogue was published twenty-five years ago (Castoviejo et al., 1980), it was quite thorough at that time; however, the bulk of new floristic records since then have been aquatic plants (as shown in this Aquatic macrophytes in Doñana protected area (SW Spain): An overview P. García Murillo1, R. Fernández Zamudio1, S. Cirujano2& A. Sousa1 1Departamento de Biología Vegetal y Ecología. Facultad de Farmacia. Universidad de Sevilla. Apdo. 874. E-41080 Sevilla. Spain. pg[email protected], [email protected] & [email protected] 2Real Jardín Botánico, CSIC. Plaza de Murillo 2. E-28014-Madrid. Spain. [email protected] ABSTRACT A big portion of the Doñana protected areas corresponds to wetlands; in them aquatic macrophytes are the main primary producers and play also other important ecological functions. Nevertheless, they are inconspicuous organisms and their importance in these ecosystems does not seem to be well reflected in the bibliography about this natural area. This paper reviews the most significant information gathered about this group of organisms in this protected area, provides an updated catalogue of this group of plants, and offers some considerations related with this topic. Key words: Doñana, aquatic macrophytes, aquatic vegetation, SW Europe. RESUMEN Una gran parte de los espacios protegidos de Doñana corresponde a humedales, en ellos los macrófitos acuáticos son los principales productores primarios, realizando además otras importantes funciones ecológicas. Sin embargo, son organismos poco conspicuos y su importancia en estos ecosistemas no parece estar reflejada en las publicaciones existentes relativas a este espacio natural. Este artículo recopila la información más significativa sobre este grupo de organismos en este espacio protegido, proporciona el catálogo actualizado de este grupo de vegetales y ofrece algunas consideraciones relativas al tema. Palabras clave: Doñana, macrófitos acuáticos, vegetación acuática, SW Europa. Limnetica, 25(1-2): 71-80 (2006) The ecology of the Iberian inland waters: Homage to Ramon Margalef © Asociación Española de Limnología, Madrid. Spain. ISSN: 0213-8409 Figure 1. Location of Doñana protected areas. Localización de los espacios protegidos de Doñana. Limnetica 25(1-2)01 12/6/06 13:54 Página 71 paper). This indicates how little is known about aquatic plants in this area. This is coupled with the fact that some significant environmental events have occurred in this same time period, an increase in intensive agriculture in the area, increased tourism in bordering areas, overexploitation of ground waters, invasions of exotic species, global warming, etc. All of these issues point to the need to update the information related to the aquatic macrophytes in the Doñana protected area, which is the aim of this paper. FIRST STEP: CATALOGUING Unlike the cases of other places of great natural value in the southern Iberian Peninsula, such as the Sierra Nevada or Sierra de Grazalema, which were prospected by botanists during the nineteenth century or before, the first studies on Doñana´s flora appear much later in the mid-twentieth century. In 1945 C. Vicioso, an Aragonese botanist, published a list of taxa collected in the south part of the Huelva Province, but among these references there was no data on macrophytes. It was not until 1967, when references to aquatic macrophyte were found, that seven aquatic macrophytes were cited in an invertebrate catalogue (Mazaranov, 1967) for Guadalquivir Marshes (belonging to Doñana). Cabezudo later began the systematic study of flora in this preserved area, including 18 species of aquatic macrophytes in his studies (Cabezudo, 1974; 1975; 1978, and Galiano & Cabezudo, 1976). In 1981, some years later, the brilliant work of Castroviejo et al. (1980) completed the information compiled by Cabezudo, nearly completing the list of vascular plants in Doñana National Park. In subsequent years this Catalogue has changed very little, with the exception of aquatic plants that have contributed some important new records to the Doñana Catalogue: Althenia orientalis (García Murillo & Talavera, 1986), Callitriche lusitanica (Pizarro, 1990), Zannichellia obtusifolia (Talavera et al., 1986, Lemna trisulca, and Spirodella polyrhyza (García Murillo et al., 1991), etc. (Table. 1). In terms of the “other” plant groups included in aquatic macrophytes, i.e., Charophyta and Bryophyta, data on these are more scarce and inconsistent. The first records of Charophyta were noted by Corillion (1961), who included two of Doñana’s Charophyta species in his work on southern Spain and North Africa charophytes: Chara connivens and Nitella flexilis. Some years later, Comelles (1982) and Sánchez (1984) added two more taxa to the list: Tolypella hispanica and Chara fragifera, respectively. Almost one decade later García Murillo et al. (1993) added nine new records to Doñana’s charophyte catalogue. Finally, the most recent records are on Chara vulgaris var. oedophylla and Tolypella salina, referenced by Espinar et al. (1997). In the Bryophytes group, there are two papers on the Riella genus (Cirujano et al., 1988 and 1992); Riccia fluitans and Ricciocarpos natans were mentioned by Rivas Martínez et al. (1980) and Sphagnum inundatum by García Murillo et al. (1995). Table 1 shows the complete and current catalogue of Doñana’s submerged macrophytes. It includes 74 taxa (21 more than those related in 1993 by García Murillo et al.) of which 46 are Spermatophyta (62 %), 3 Pteridophyta (4 %), 6 Bryophyta (8 %) and 19 Chlorophyta (26 %). Besides, this table points to the first floristic record of each taxon. 72 García Murillo et al. Table 1. Catalogue of aquatic macrophytes of Doñana protected areas. Catálogo de los macrófitos acuáticos de los espacios protegidos de Doñana. TAXA* FIRST RECORD CHLOROPHYTA Characeae Chara aspera Deth. ex Willd. var. aspera García Murillo, Bernués & Montes, 1993 Characeae Chara canescens Desv. & Lois. García Murillo, Bernués & Montes, 1993 Characeae Chara connivens Salmz. ex A. Braun Corrillion, 1961 Limnetica 25(1-2)01 12/6/06 13:54 Página 72 Aquatic macrophytes in Doñana 73 Table 1. Continued. Continuación. CHLOROPHYTA Characeae Chara fragifera Durieu Sánchez, 1984 Characeae Chara fragilis Desv. Fernández Zamudio et al. (2006) Characeae Chara galioides DC. García Murillo, Bernués & Montes, 1993 Characeae Chara hispida L. Van Vierssen et al., 1982 Characeae Chara vulgaris L. var. vulgaris García Murillo, Bernués & Montes, 1993 Characeae Chara vulgaris L. var. contraria Fernández Zamudio et al. (2006) (A. Braun ex Kütz.) J. A. Moore Characeae Chara vulgaris L. var. oedophylla Espinar et al., 1997 (Feldman) R. D. Wood Characeae Chara vulgaris L. var. longibracteata (Kütz.) Fernández Zamudio et al. (2006) J. Groves & Bullock-Webster Characeae Lamprothamnium papulosum (Wallr.) J. Groves García Murillo, Bernués & Montes, 1993 Characeae Nitella flexilis (L.) C. Agardh Corrillion, 1961 Characeae Nitella hyalina (DC.) C. Agardh García Murillo, Bernués & Montes, 1993 Characeae Nitella tenuisissima (Desv.) Kütz. García Murillo, Bernués & Montes, 1993 Characeae Nitella translucens (Pers.) C. Agardh García Murillo, Bernués & Montes, 1993 Characeae Tollypella glomerata (Desv.) Leonh. García Murillo, Bernués & Montes, 1993 Characeae Tollypella hispanica Nordst. ex T.F. Allen Comelles, 1982 Characeae Tollypella salina Corillion Espinar et al., 1997 BRYOPHYTA Ricciaceae Riccia fluitans L. Rivas-Martínez et al., 1980 Ricciaceae Ricciocarpos natans L. Rivas-Martínez et al., 1980 Riellaceae Riella cossoniana Trabut Cirujano et al., 1992a Riellaceae Riella helicophylla (Bory & Mont.) Mont. Cirujano et al., 1988 Riellaceae Riella notarisii (Mont.) Mont. Cirujano et al., 1992a Sphagnaceae Sphagnum inundatum García Murillo et al., 1995 PTERIDOPHYTA Azollaceae Azolla filiculides Lam. Cobo et al., 2003 Isoetaceae Isoetes velatum A. Braun subsp. velatum Galiano & Cabezudo, 1976 Marsileaceae Marsilea strigosa Willd. Fernández Zamudio et al. (2006) SPERMATOPHYTA Apiaceae Apium inundatum L. Allier & Bresset, 1975 Apiaceae Oenanthe fistulosa **L. Cabezudo, 1975 Apiaceae Thorella verticillatinundata** (Thore) Briq. Cabezudo, 1974 Apiaceae Oenanthe globulosa** L. Cabezudo, 1975 Carum verticillatum** (L.) Koch Galiano & Cabezudo, 1976 Apiaceae Eryngium corniculatum** L. Cabezudo, 1974 Apiaceae Eryngium galiodes** Lam Cabezudo, 1978 Callitrichaceae Callitriche truncata Guss. subsp. occidentalis Castroviejo et al., 1980 (Rouy) Schotsman Callitrichaceae Callitriche lusitanica Schotsman Pizarro, 1990 Callitrichaceae Callitriche stagnalis Scop. García Murillo, Bernués & Montes, 1993 Callitrichaceae Callitriche brutia Petagna Castroviejo et al., 1980 Callitrichaceae Callitriche obtusangula Le Gall Fernández Zamudio et al. (2006) Ceratophyllaceae Ceratophyllum demersum L. Mazaranov, 1967 Cyperaceae Scirpus fluitans L. Rivas-Martínez et al., 1980 Limnetica 25(1-2)01 12/6/06 13:54 Página 73 SECOND STEP:AQUATIC MACROPHYTES AND ENVIRONMENTAL FACTORS At the end of the 1970s, González Bernáldez directed a series of studies on the relationship between the plants in Donaña and the environment (see García Novo, 1997). In this context, there was practically no mention of aquatic plants, with just one study found on the marsh’s vegetation (Allier & Bresset, 1977). In 1980, Rivas Martínez et al. published an excellent work on the vegetation in the Doñana National Park, in which they carried out a detailed phytosociological analysis of the different communities of plants in this protected natural area. Nevertheless, despite the superior quality of the research done, the informa74 García Murillo et al. Table 1. Continued. Continuación. SPERMATOPHYTA Elatinaceae Elatine alsinastrum L. Mazaranov, 1967 Elatinaceae Elatine macropoda Guss. Mazaranov, 1967 Elatinaceae Elatine hexandra (Lapierre) DC. Cabezudo, 1975 Halogaraceae Myriophyllum alterniflorum DC. Mazaranov, 1967 Halogaraceae Myriophyllum spicatum L. Van Vierssen et al., 1982 Hydrocharitaceae Hydrocharis morsus-ranae L. Cabezudo, 1978 Juncaceae Juncus heterophyllus Dufour Galiano & Cabezudo, 1976 Lemnaceae Lemna gibba L. Galiano & Cabezudo, 1976 Lemnaceae Lemna trisulca L. García Murillo et al., 1991 Lemnaceae Lemna minor L. Mazaranov, 1967 Lemnaceae Spirodella polyrhiza (L.) Schleiden García Murillo et al., 1991 Lemnaceae Wolffia arrhiza (L.) Horkel ex Wimmer García Murillo, 2000 Lentibulariaceae Utricularia exoleta R. Br. Castroviejo et al., 1980 Lentibulariaceae Utricularia australis R. Br. Cabezudo, 1975 Nymphaeaceae Nuphar luteum L. Castroviejo et al., 1980 Nymphaeaceae Nymphaea alba L. Castroviejo et al., 1980 Polygonaceae Polygonum amphibium L. Castroviejo et al., 1980 Potamogetonaceae Potamogeton natans L. Galiano & Cabezudo, 1976 Potamogetonaceae Potamogeton polygonifolius Pourret Castroviejo et al., 1980 Potamogetonaceae Potamogeton lucens L. Mazaranov, 1967 Potamogetonaceae Potamogeton trichoides Charm. & Schlecht. Cabezudo, 1978 Potamogetonaceae Potamogeton crispus L. Mazaranov, 1967 Potamogetonaceae Potamogeton pectinatus L. Mazaranov, 1967 Ranunculaceae Ranunculus tripartitus DC. Cabezudo, 1978 Ranunculaceae Ranunculus peltatus subsp baudotii Allier & Bresset, 1975 (Godron) Meikle ex C. D. K. Cook Ranunculaceae Ranunculus peltatus subsp saniculifolius Pizarro, 1993 (Viv.) C. D. K. Cook Ranunculaceae Ranunculus peltatus Schrank subsp fucoides Cirujano et al., 1992b (Freyn) Muñoz Garmendia Ruppiaceae Ruppia maritima L. var. maritima Cabezudo, 1978 Ruppiaceae Ruppia drepanensis Tineo Castroviejo et al., 1980 Zanichelliaceae Althenia orientalis (Tzvelev) García Murillo & Talavera, 1986 García Murillo & Talavera Zanichelliaceae Zannichelllia obtusifolia Talavera, Talavera et al., 1986 García & Smith Zosteraceae Zostera noltii Hornem Castroviejo et al., 1980 * Some taxa refereed to Doñana Protected Areas have been related with incorrect identifications (as Callitriche palustris L., Hippuris vulgaris L., Zannichellia palustris L. or Zannichellia peltata Bertol.) in other cases they correspond with synonyms (as Ranunculus baudotii Godron; Ruppia maritima subsp. drepanensis L.(Tin.) Maire & Weiller or Utricularia gibba L.). ** The juvenile form of these species show morphological, anatomical and physiological characters corresponding with aquatic macrophytes. Limnetica 25(1-2)01 12/6/06 13:54 Página 74 tion on aquatic plant communities was insufficient (as can be deduced from the chorological changes after 1980, included in Table 1). In the 90s, in response to researches by Montes on Donaña’s aquatic ecosystems, new data appeared on the ecology of aquatic plants in the area: data was published on their biomass (Duarte et al. 1990); the main factors (flooding time and salinity) controlling the distribution of these plants in Doñana’s wetlands were identified (Bernués, 1990; Duarte et al., 1990); and a study was done on the marsh’s seed bank (Grillas et al., 1993). Santamaría (Santamaría, 1995; Santamaría & Hootsmans, 1998; Santamaría et al., 1995; 1996), under the direction of Montes and with samples collected from Doñana, also carried out a series of studies on the autoecology of Ruppia drepanensis Tineo, one of the most abundant underwater macrophytes in the Doñana salt marsh. In this same period, Serrano & Toja (1995), working in sand lagoons of Doñana, related the presence of some aquatic macrophytes with other ecological parameters. And finally, more recent works by Espinar (2004) and Espinar et al. (2002) have contributed valuable information on the salt marsh aquatic macrophytes in relation to their environment and to communities of helophytes. Studies on Seed Dispersal At the turn of the century, and as a result of the multidisciplinary approach taken by the Doñana Biological Station to environmental processes and with the involvement of Santamaría, a series of studies appeared on the role of birds in the passive transport of organisms. To be sure, a large number of these studies focused on the dispersal of aquatic macrophyte seeds by aquatic birds (Charalambidou et al., 2003; Green et al., 2002; Figuerola & Green, 2002 and 2004; Figuerola et al., 2002; 2003 and 2005). These researches have been consolidated as a line of work, which is currently being carried out in the Doñana Biological Station under the direction of Green, with outstanding results. Likewise, Espinar et al. (2004) have recently published studies in this area. Aquatic Plants and Climate Change As stated in the introduction to this paper, a site’s flora is one of the best natural sources of information on that area. This fact is even more perceptible in aquatic plants since their reaction to environmental changes (due to their particular physiology) is much faster and precise. Based on this premise, recent studies carried out in the eastern part of Doñana National Park and in the park’s lagoons have shown how useful diachronic studies on the presence and distribution of aquatic plants can be in detecting climatic changes within relatively recent timeframes. The work of Sousa (2004) and Sousa & García Murillo (1998; 1999; 2003 and 2005) illustrate this fact and find an explanation for the processes of aridization and desiccation of the coastal wetlands of Huelva Province by linking these processes to the end of the Little Ice Age, using –among other things– the presence of certain species of aquatic plans, the distribution of vegetation in the wetlands, and their changes over time. THIRD STEP: REGARDING CONSERVATION The uniqueness of the diverse species of aquatic macrophytes found in south-western Europe has been pointed out by some authors (Cook, 1983; García Murillo, 2003; Montes & Martino, 1987); the majority of these taxa are located in the Doñana area. The work of Cirujano et al. (1992b) is noteworthy here in its ranking of Spanish wetlands based on the presence of certain species of macrophytes; the Doñana salt marsh was ranked second among all wetlands considered.1 In addition, in the late 1990s, the Andalusian Regional Environmental Agency (later, the Environmental Council) started a line of research aimed at identifying the biology of the plant species most at risk from a conservation standpoint. Aquatic macrophytes in Doñana 75 1In the work cited, the authors did not consider the Doñana lagoons or the changes in flora, which occurred after the work’s publication, which clearly would have significantly increased the ranking of this area. Limnetica 25(1-2)01 12/6/06 13:54 Página 75 The most salient outcomes of these studies were the “Andalusian Plant Species Red List (Decreto 104/1994; Ley 8/2003)” and two volumes compiling the most significant information on the species selected (Blanca et al., 1999-2000). In contrast to previous Spanish “Red Lists” (ICONA, 1987), this one included a significant number of aquatic species, as well as Althenia orientalis, Hydrocharis morsus-ranae, Utricularia exoleta, Wolffia arrhiza, Marsilea strigosa, and Thorella verticillatainundata (García Murillo, 2000; Silvestre, 2000), found in the Doñana area. This was followed, as proposed by the Ministry of Environment, by numerous studies intended to update the “Red List” (ICONA, 1987) nationally. These studies were compiled in the AFA Project (Bañares et al., 2003), including the red list and the most relevant data from the research done on the different species, although it was not possible to study some of the species listed. The AFA red list includes two aquatic macrophyte species found in Doñana (Utricularia exoleta and Hydrocharis morsus-ranae). The surveys and research carried out for the Red Lists generated numerous articles which highlighted the state of some species of aquatic macrophytes. Included among such articles were those of Cirujano et al. (1998) and García Murillo et al. (2000) on species found in the Doñana protected area. Exotic Organisms The early 1980s brought the detection of the first exotic organisms in Doñana (García Murillo et al., 2004b). The first of such invaders was the American crawfish (Procambarus clarckii) and its spectacular proliferation. The ability of P. clarckii to physically transform its environment and alter the availability of resources for other species in the aquatic ecosystems in which it was introduced, deeply concerned environmentalists and scientists. Its effect upon macrophyte communities was tremendous, given that they are its principal food source. After the initial period of crawfish expansion, numerous Doñana macrophyte communities were simply dwindling, with some species wiped out due to the activity of this animal (Bravo et al., 1993; Duarte et al., 1990; García Murillo et al., 1993). The numerous studies on P. clarkii, undertaken by the UAM (Universidad Autónoma of Madrid) research team headed by Montes, have emphasised the fact that it is now a key element in most of the aquatic ecosystems in Doñana and a significant control factor when it comes to aquatic macrophyte populations in this protected area (Bravo et al., 1993; Gutiérrez-Yurrita et al., 1998). Likewise, the Azolla filiculoides species –a floating pteridophyte native to the New World– began to appear in the Doñana marsh in the early part of the 21st century (Cobo et al., 2003 and García Murillo et al., 2004a). In just a couple of years, its presence has extended over nearly the entire marsh, forming carpets sometimes reaching 10cm thick, which can be clearly seen from the RBD (Doñana’s Biological Reserve) plane used for bird surveys. These carpets prevent the sun’s rays from reaching the water below, thereby making it impossible for submerged macrophytes (nearly all present in this area) to develop. They also increase eutrophyzation since they can fix nitrogen, and their respiratory activity consumes the oxygen in the water below (García Murillo et al. 2004a). Just as with the American red crawfish, the changes in the aquatic ecosystems of Doñana attributable to Azolla filiculoides may be dramatic. The attempts to control it have, to date, been futile (García Murillo et al., 2004b). Finally, in December of 2004, the tropical neophyte Pistia stratiotes was found in some irrigation canals located in the Doñana Park in the area of Sanlúcar de Barrameda covering 3Km of canals (García Murillo et al., 2005a). Thanks to the quick intervention of the Andalusian Regional Council on the Environment –faced with the risk posed by this new invasion to the Doñana protected areas– and the low temperatures in January 2005, the Pistia carpets were eliminated (García Murillo et al., 2005b). Nevertheless, the risk continues to exist since some of the Pistia plants sampled had flowers and seeds, and it is well-known that the seeds of this species can remain functional for long periods of time buried under the water. 76 García Murillo et al. Limnetica 25(1-2)01 12/6/06 13:54 Página 76 CONCLUSIONS In the time span since the publication of the last floristic catalogue on the Doñana area, numerous references whose primary or secondary objective is the study of Doñana’s aquatic macrophytes can be cited, although they are few in comparison to existing information on other in the same area. With regard to the catalogue on aquatic macrophytes, we believe it is completed except for the addition of new exotic plants whose effects encompass this natural area (Cobo et al., 2003), and the withdrawal of others –cited by 20th-century researchers– which have disappeared due to the deterioration in water quality and the pressure of the environment surrounding this protected natural area. The regional administration –and to a lesser extent the national one– has taken this situation into account, by including some of the aquatic macrophytes in its red list of species in danger of extinction. Nevertheless, the number of taxa which should be included in the list is greater (see Cobo et al., 2002). Moreover, the importance of this area for the conservation of aquatic macrophytes is evident since it contains numerous species of aquatic macrophytes, many of which are limited-area species (“endemic species”), relatively uncommon in aquatic plants. Along the same lines, a conflict has arisen in the area’s flora conservation-management, fully affecting the group of aquatic plants: many of the aquatic macrophyte species found in Doñana cover wide areas of distribution (in theory); however (in reality) these areas are largely fragmented, with similarly fragmented populations. These species should be included in the red lists, since their vulnerability is quite high, a fact which has been ignored by environmentalists when it comes to the (theoretical) distribution areas of these species. As studies are concerned on aquatic macrophytes and how they relate to environmental factors, while there are a number of quality studies on this subject, more work on the basic aspects of this relationship would be of value (e.g., how macrophytes relate to nutrients, factors determining macrophyte distribution, studies on succession, etc.). Finally, attention must be called to the deterioration of Doñana’s waters, the effects of which operate on two levels: 1. By causing the disappearance of so-called “difficult environment” specialist plants that had taken refuge in this natural setting (such as plants from bogs or oligotrophic wetlands) 2. By facilitating the invasion of exotic species, some of which have great potential for habitat modification and its consequences. 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