Diatoms from lentic and lotic systems in Antioquia , Chocó and Santander Departments in Colombia

In the tropical and subtropical regions, there is a large number of species which has not been yet described. The high possibility of extinction makes their inventory a priority. In this paper, 23 diatoms taxa from Andean lotic systems and lentic waterbodies localized in the Departments of Antioquia, Santander and Chocó, Colombia, are analyzed with light and scanning electron microscopy. Each taxon is described and information about environmental characteristic of the sites where they were collected and distribution in Colombia is given. The studied taxa belong to the orders Thalassiosirales (1), Aulacoseirales (1), Fragilariales (4), Cymbellales (7), Achnanthales (2), Naviculales (7), and Thalassiophysales (1). Fifteen of them are recorded for the first time in Colombia and Encyonema jemtlandicum in South America. A comparison with the diatom flora of the Colombian Amazonia showed that there were only three taxa in common to these two equatorial regions probably due to the influence of altitudinal gradient. Rev. Biol. Trop. 56 (3): 1159-1178. Epub 2008 September 30.

In the tropical and subtropical regions, there is a large number of species which has not been yet described.The high possibility of extinction makes their inventory a priority.Although most diatoms researchers work with the assumption that freshwater diatoms are widespread, the cosmopolitan paradigm is, however, in conflict with observations (Kociolek and Spaulding 2000).These authors pointed out that regional studies, in which a concerted effort to determine species with a consistent taxonomy, provide a way to examine cosmopolitism.They also mention several examples of morphological detailed studies which demonstrated that taxa may be misidentified or erroneously described as having disjoint distribution.
The information about the Diatom flora of South America is incomplete and needs a careful revision on the basis of modern tools.The most recent and general analyses of this flora were held by Metzeltin andLange-Bertalot (1998, 2007) in tropical areas and by Rumrich et al. (2000) in the Andes from venezuela to Tierra del Fuego.Metzeltin and Lange-Bertalot (1998) pointed out that in warm or cold regions of South America there is a great number of species that are cosmopolitan or typical of temperate climatic zones, while in the tropical regions the flora is completely different, with exception of the areas with a high anthropogenic influence, and that many endemic taxa were found.The observations of Rumrich et al. (2000) confirm these ideas with exception of many endemic taxa of high altitudes.These approaches are interesting as a start point of modern floristic studies in South America, but regional studies are still necessary for testing them because these analyses were based in a limited number of samples in relation to the dimensions of the studied area.
Colombia is an interesting country from a biogeographic point of view.The geographical situation favors the existence of a great variety of geomorphologic and climatic situations in small areas as a consequence of high altitudinal gradients.In this country, although there are numerous records of diatom taxa in ecological studies about periphitic communities (Moreno 1989, Donato et al. 1996, Montoya 1998), in paleoecological investigations (Lozano et al. 1999), and studies about phytoplankton ecology (Ramírez and Machado 1982, Ramírez 1994, Ramírez and Díaz 1994, Asprilla et al. 1998, Plata 2000, Ramírez et al. 2000, among many others), the knowledge about morphology and taxonomy of freshwaters diatoms is scarce.There are some publications about the Colombian Amazonia (Sala et al. 1999(Sala et al. , 2002a, b) , b) and descriptions of few species collected in high mountains (Lange-Bertalot and Moser 1994, Lange-Bertalot et al. 1996, Metzeltin and Lange-Bertalot 1998, 2007, Rumrich et al. 2000).
Ninety diatom taxa were identified in a preliminary study held in lentic and lotic systems from Antioquia and Chocó Departments, while 116 taxa were recorded in lotic systems of Santander Department.Approximately 30 % of these taxa could not be assigned to recognized taxonomic entities being probably new for science.The aim of this paper is to describe those taxa common to these three systems, and to give information about the conditions in which they were collected and about their distribution in Colombia.
La Vega Stream: la vega is a small lotic system located between 790 and 1 250 masl in the middle portion of the Nus River Basin (catchment area: 6.7 km 2 ), Municipality of San José del Nus (6°27' N-6°29'30" N and 74°49'30" W-74°52' W), Department of Antioquia.The studied material was collected in three sampling sites: Piedras Stream, Guaico Stream and La vega Stream between August 2001 and April 2002.Two samplings were made during the rainy season (November 2001, April 2002) and two in the dry one (August 2001 andFebruary 2002).The area is subject to tree felling and extensive cattle raising, with advanced erosion processes; the riparian vegetation is composed by grasses and short shrubs (hernández-Atilano et al. 2005).Code samples: LPC10001, April 2002;LPC10002, February 2002;LPC10003, April 2002;LPC10004, April 2002;LPC10005, November 2001;and LPC10006, November 2002.El Carmen de Viboral Municipality: this municipality (6°05'09'' N, 75°20'19'' W) is located on the Central Mountain Range of Los Andes to the west of the Department of Antioquia, has an extension of 448 km 2 , an altitude oscillating between 800 and 3 340 masl.Its annual mean temperature is 17 ºC and an annual mean precipitation oscillating between 2 150 and 2 235 mm.In accordance to Espinal (1992) the Life Zone of this municipality is bh-MB (bosque húmedo-Montano Bajo).In this locality was sampled an artificial small lake, located at 6º4'51.6''N, 75º20'7.8"W. This lake has an elongated form, moderate slopes, a mean depth of 0.55 m, a maximum depth of 2.80 m and its principal source is La Cuchilla spring.It is colonized by the floating macrophyte Nymphoides sp.(Montoya 2005).Code sample: LPC10011, November 2003.
Piedras Blancas Stream: it is a small stream located in the Park of the same name.Its basin is located between 2 200 and 2 600 masl on the Central Mountain Range of Los Andes, to the west of El valle de Aburrá in the Department of Antioquia.It is an oblongousshaped basin, with a dendritic drainage pattern, with an annual mean precipitation of 1 815 mm, an annual mean temperature of 14.7 ºC, a maximum of 20 ºC and a minimum value of 5 ºC (Empresas Públicas de Medellín 1988).It has two rainy periods (April-May and September-November).
In the basin there are two life zones −bh-MB (bosque húmedo Montano Bajo) and bmh-MB (bosque muy húmedo Montano Bajo)-with natural vegetation, plantations of pines, cypress, eucalyptus and others; a part used for pastures, cultures and tree nursery, among other use (Espinal 1992).Code sample: LPC10012, July 2003.
Tumaradó Swamp (7º30' N and 77º30' W): shallow waterbody (approximate 2-5 m depths) with black-type waters and a high content of humic substances incoming from the surrounding riparian wood.This swamp is located at the Parque Nacional Natural Los Katíos (PNNK), northwestern part of Colombia (7°30' N, 77°30' W) in the border with Panamá at the zone of intertropical convergence.PNNK comprises 720 km 2 belonging to the municipalities of Turbo (Department of Antioquia), Riosucio and Unguía (Department of Chocó) in the phytogeographic Province of Chocó.The dominant biome is the Tropical Rainy Forest.The park is located at an altitude varying between 2 and 650 masl with an annual precipitation varying from 2 000 to 3 500 mm and a mean annual temperature of 27 °C.Code samples: LPC10007, May 2000; LPC10008, May 2000; LPC10009, May 2000 and LPC10010, May 2000.
Lebrija River Basin: this river has a catchment area of 3 727 km 2 , formed by 8 sub-basins and 25 micro-basins.The altitudinal gradient comprises from 300 to 3 800 masl with mean temperatures of 30 °C to 6 °C and mean annual precipitation between 2 065 and 660 mm respectively, with two rainy periods (March-May and September-November) and two dry periods (December-February and June-August) (CDMB 2004).In the framework of study held to evaluate water quality of the basin, samples were collected in 25 sites, for this paper we choose those samples with greater species richness.These were collected at eight rivers, upstream and downstream of the polluted places and after the confluence of the rivers.Codes and some general characteristics of these places are given below.
El Methods: Epiliton samples at La vega Stream were collected between August 2001 and April 2002 at three sampling places, brushing a total area of 900 cm 2 .At the Lebrija River Basin they were collected during May and July 2000 by brushing the surfaces of a variable number of substrates delimited with a 25 cm 2 acrylic frame.At every place was also obtained information about water temperature, conductivity and dissolved oxygen.Fishes stomach contents samples from Tumaradó Swamps were obtained from Prochilodus magdalenae (Bocachico).
Samples were fixed with 10 % Lugol or 6-8 % formalin and were treated to eliminate organic matter following the method described in CEN/TC 230 (2002).Samples for light microscopy (LM) were mounted in Naphrax and for scanning electron microscopy (SEM) on glass stubs and then coated with gold-palladium in a Jeol FINE CoAT IoN SPUTTER JFC-1100.observations were carried out with a Wild M20 LM and a Jeol JSM-T100 SEM at the Servicio de Microscopía Electrónica del Museo de La Plata.
The descriptions are accompanied with information about the physical and chemical data of the sites were the materials were collected.Information about distribution in Colombia is based in Imani (2003) and papers published afterwards.
Uncleaned and cleaned subsamples and permanent slides are deposited at the Laboratorio de Limnología del Instituto de Biología de la Universidad de Antioquia (Medellín, Colombia), the Colección Limnológica del Museo de historia Natural de la Universidad Industrial de Santander (UIS) and at the herbario of Departamento Científico Ficología, Museo de Ciencias Naturales de La Plata, Argentina (LPC).
Distribution in Colombia: this cosmopolitan species was mentioned in Alta Montaña Province (Donato, 2001).
Distribution in Colombia: this cosmopolitan species is recorded for the first time.
Distribution in Colombia: this cosmopolitan species was reported in Colombia at Provincias Andina, Tierras Bajas and Amazonia.
Bas.: Stauroneis bacillum Grunow valve linear to linear-lanceolate with rounded ends.Axial area narrow at the first third of the valve, widening to the valve center.Central area reaching both margins.Striae parallel to slightly radiate, irregular in length; areolae difficult to see even with SEM.Raphe filiform arched; external proximal ends dilated and slightly curved to the same side; terminal fissures curved in the same direction (opposite to the proximal ends).Length: 23-27 µm, width: 5.5-7.0 µm; striae: 17-23 in 10 µm.
Distribution in Colombia: this cosmopolitan species is recorded for the first time.
Distribution in Colombia: this cosmopolitan variety was mentioned in the Provincia de Alta Montaña.
Cells drum shaped, solitary.valve face with two differentiated areas, the central one tangentially undulated, with irregular areolae that do not penetrate the siliceous wall and the external one with areolae arranged in multiseriate fascicles and internal chambers.Fultoportulae with three satellite pores, 1-2 eccentric and the others in a marginal ring located at every interfascicle a little below the valve face/ mantle junction.one rimoportula placed in the same position of the fultoportulae ring.valve mantle with strong spines placed at the valve face/ mantle junction and others small with variable distribution.Diameter: 10-18 µm; fascicles: 6-8 in 10 µm.
Distribution in Colombia: this species, mentioned in the literature as cosmopolitan, was recorded in the Provincia Andina and in the Provincia Costera.
valves semilanceolate with subrostrate ends, dorsal margin strongly convex and ventral margin straight or slightly convex.Axial area narrow; central area slightly differentiated, with one stigma located at the end of the ventral median striae.Raphe complex, externally it is strongly undulated with proximal and distant ends curved to the dorsal side.Internally, the raphe is arched to the dorsal side of the valve, without intermissio and conspicuous helictoglossae.Striae uniseriate, radiate.Length: 40-48 µm; width: 12-14 µm; dorsal striae: 7-10 in 10 µm at the center and 9-12 in 10 µm at the poles; ventral striae: 8-10 in 10 µm at the center and 9-12 in 10 µm at the poles; areolae: 25 -26 in 10 µm.
Distribution in Colombia: this cosmopolitan species is registered for the first time in the country.

Encyonema jemtlandicum
valves semilanceolate, dorsal margin convex, and ventral margin slightly tumid, apices acute not differentiated.Axial area narrow, slightly dilated at the central area.Raphe complex, externally the raphe branches are strongly sinuous, with proximal ends dilated and curved to the dorsal side and terminal ends curved to the ventral side and internally straight with proximal ends curved to the dorsal side in straight angles and terminal ones not reaching the poles.Dorsal striae radiate and ventral striae parallel at the center and convergent at the poles; interstriae wide.Length: 34-35 µm, width: 7.5 µm; dorsal striae: 10 in 10 µm; ventral striae: 11 in 10 µm; areolae: 33 in 10 µm.
Distribution in Colombia: this taxon has been reported by Krammer (1997) only for Döda fallet; Abisko, Schwedisch-Lappland.In Colombia it is registered for the first time.
Observations: the studied material coincides with the specimens described in Krammer (1997: 166, Fig. 35 The studied material differs from the var.jentlandicum in the narrower interstriae, the dorsal areolae near the raphe more distant than the others, and the external proximal ends less dilated.Length: 35 µm, width: 8 µm; dorsal striae: 11 in 10 µm (center), 12 in 10 µm Distribution in Colombia: this species, only reported at the Andes of venezuela and Chile, is mentioned for the first time in the country.
Observations: The studied materials are similar in valve outline and dimensions to the material showed in Krammer (1997): 166, Fig. 14 but as in the literature there are not details of the fine morphology it is difficult to identify it without doubts.Eolimna subminuscula (Manguin) Lange-Bertalot (Fig. 17A, B, 18) G. Moser, Lange-Bertalot et Metzeltin 1998, Bibl. Diat. 38, p. 154.Bas.: Navicula subminuscula Manguin valves lanceolate with subrostrate or subacute ends.Axial area linear, moderately wide.Central area variable, absent in some specimens and asymmetric due to the shortening of the median striae.Striae uniseriate composed of circular areolae, radiate at the poles and parallel at the center.Raphe filiform slightly arcuate, external proximal ends, dilated in small pores, gently curved to the same side and opposite to the distal hooked endings; internal proximal raphe ends slightly curved in the same direction and terminal ones with small helictoglossae.Length: 9.0-10.5 µm, width: 4.0-4.5 µm; striae: 16-22 in 10 µm; areolae: 31-38 in 10 µm.
Distribution in Colombia: this species, mentioned in the literature as cosmopolitan, is recorded in Colombia for the first time.
Distribution in Colombia: this taxon is recorded in Colombia for the first time.
Observations: although the analyzed specimens belong to sites ecologically heterogeneous, they present little morphological variation.The valve outline, dimension, type of raphe and typo of striae evidences that the studied material belongs to the genus Eolimna but it could not be assigned to any species of the genus.It coincides in valve outline, dimensions and striae density with the specimens illustrated in Simonsen (1987) as the holotype of N. tantula hustedt (Plate 275, Fig. 20 a 26), but the general appearance of these materials differ from the specimens illustrated by hustedt (in Schmidt et al. 1934, Taf. 394-400) and in hustedt (1962) under this name.Simonsen (1987) pointed out that N. tantula was reported without description in hustedt (1934) and then described in hustedt (1937) as Stauroneis fonticola.Also, this author recommends consulting hustedt (1962).our material do not coincide with any of the specimens illustrated by hustedt in the above mentioned publications and are similar to Stauroneis fonticola in valve outline, morphometric data and the striae in the central area but differ in the presence of the conspicuous stauro.our material also differs from the specimens described in Krammer and Lange-Bertalot (1986, pl. 76, Fig. 39-47) who pointed out that N. tantula is synonym of Navicula minima Grunow and that their Fig.47 corresponds to the holotype of N. tantula.Comparing our materials with others in the literature we found that they are similar in valve morphology and morphometric data to those collected in Ecuador and illustrated as Eolimna (nov.?) spec.and Eolimna aff.minima (Grunow) Lange-Bertalot by Rumrich et al. (2000, Pl. 71, Fig. 5-8 and 4, 9 and 10 respectively) and to the specimens illustrated as E. sp.aff.minima in Monnier et al. (2003).on the basis of all above mentioned we believe that before proposing any new taxon or new combination it is necessary a comparative study with electron microscope of all the materials studied by hustedt as N. tantula and S. fonticola and type material of N. minima.
Fragilaria capucina Desmazieres (Fig. 22) Desmazieres 1825: Plant.Cryp.Fr., Fasc. 10 N° 453 valves linear to linear-elliptical with rounded to capitate ends.Axial area widening to the central part of the valve; central area asymmetric reaching one of the valve sides, inflated in some specimens.Striae uniseriate, parallel and slightly radiate to the poles.Rimoportulae eccentric, placed at one pole near the last stria.
Observations: Williams and Round (1987) consider that Fragilaria vaucheriae (Kützing) Petersen is a different species and not a variety of F. capucina.Nevertheless in the studied populations we found a continious variation of the central area, some specimens with one side inflated and others without inflation.As they do not differ in the other characters we consider that all of them belong to F. capucina.This material resembles those described in Argentina (Sala, 1996) in the absence of marginal spines.

Frustulia vulgaris (Thwaites)
De Toni (Fig. 20 Distribution in Colombia: this cosmopolitan species was recorded in Tierras Bajas. Observations: the studied material coincides with the description of the species given in Lange-Bertalot (2001).
Distribution in Colombia: this cosmopolitan species is recorded for the first time in Colombia.
Distribution in Colombia: this species was recorded in the Provincia de Alta Montaña.

Gomphonema lagenula
Kützing (Fig. 25  stria.A stigma, placed at the central nodule at the end of the long central stria, has an external round opening and is internally elongated.Striae, uniseriate, slightly radiate at the center and radiate at the poles; areolae with c-shaped foramina.Raphe with external fissures slightly undulated, dilated proximal ends and distal ends bent to the same side; internally the raphe fissures are straight, with hooked proximal ends and conspicuous helictoglossae.Length: 24-31 µm; width: 4-7.5 µm; striae: 9-12 in 10 µm at the center, 10-15 in 10 µm at the head pole; areolae: 30-39 in 10 µm.
Distribution in Colombia: this cosmopolitan species is recorded for the first time in the country.
Distribution in Colombia: this cosmopolitan species is recorded for the first time in the country.
Distribution in Colombia: this taxon, recorded for the first time in Colombia, was only found in Chile (Rumrich et al., 2000).
Distribution in Colombia: this species was registered in the Provincias Andina and Alta Montaña.Observations: the striae density of the studied specimens coincides with those described in Germain (1981) and differs from those in Patrick and Reimer (1966).
Distribution in Colombia: this pantropical species was reported in the Provincia Costera.
Observations: our material coincides in the ultrastructure with the material described in Williams (1986).According to Compère (2001) this species should be transferreded to the genus Ulnaria (Kützing) Compère but as our specimens differ in valve outline from the lectotype illustrated in Lange-Bertalot (1980), we pospone this proposal of transference until the type material is analysed with electron microscopy.
From the species analised in this paper A. montana, C. aff. bacillum, C. affinis, E. aff. jemtlandicum var. venezolana, E. subminuscula, Eolimna sp. aff. N. tantula, F. capucina, G. decussis, G. clavatum, G. lagenula, G. pumilum, G. punae and U. lanceolata are reported for the first time in Colombia and E. jemtlandicum is here reported for the first time in South America.A. granulata, C. meneghiniana and U. ulna have a wide distribution in the country while C. placentula var.euglypta was recorded only in the Provincia de Alta Montaña, S. pupula in Río Medellín, F. vulgaris in Tierras Bajas and S. goulardi in Provincia Costera.The majority of the reports were obtained from ecological studies so it is difficult to corroborate or reject the distribution of these taxa in the country.We compared our results with the taxonomic analysis held in the Colombian Amazonia with SEM (Sala et al. 1999(Sala et al. , 2002a(Sala et al. , 2002b)).This comparison shows that although both areas are in the equatorial region, only A. granulata, C. meneghiniana and D. confervacea were represented at these areas.This difference in the diatom floras of low and highlands at the Ecuador and Tropics reflect the influence of altitude in climatic characteristics.our observations are coincident with those of Metzeltin and Lange-Bertalot (1998) and Rumrich et al. (2000) when studying the South American diatom flora.
on the other hand, the great majority of the analyzed taxa are mentioned in the literature as cosmopolitan with the exception of U. lanceolata and S. goulardi that have a pantropical distribution and Encyonema aff.jemtlandicum var.venezolana and G. punae found only in South America.
The comparison of the fine valve morphology of the studied materials and their descriptions in the literature, even in the case of taxa described in temperate or cold regions, showed that there are not important differences with the exception of C. aff.bacillum, E. jemtlandicum aff.var.venezolana and Eolimna sp.aff.N. tantula that need more detailed analyses.

ACKNoWLEDGMENTS
To the Institute of Biología of Universidad de Antioquia, to Colciencias, and to Red Latinomericana de Botánica (RLB) for the fellowships given to the second and third authors respectively.

Oro River after the urban discharge of Piedecuesta: 840
Striae biseriate, parallel, slightly radiate at the poles; sunken in the internal side of the valve.Areolae circular and small, arranged in quincunx.one rimoportula at each pole with a prominent internal labium diagonally positioned.Apical pore fields well developed.