Original article

Ecological notes on the species of Phacus Dujardin(Euglenophyta) from the central region of Portugal

Mário Jorge Pereira a,*, Ulisses M.M. Azeiteiro b

a Departamento de Biologia, Universidade de Aveiro, 3810-193 Aveiro, Portugalb Universidade Aberta, Rua do Ameal, 752, 4200-055 Porto, Portugal

Abstract

Twenty-one species, belonging to the genus Phacus, were identified during the study of samples from the central region of Portugalcollected in lentic systems. The abundance of each taxon was determined. Water samples were taken for determination, by means of standardmethods, of physicochemical parameters (water temperature, pH, organic matter (K2Cr2O7), conductivity, alkalinity, nitrogen as N(NH4

+),N(NO2

–) and N(NO3–), orthophosphate P(PO4

3–) and metals in a total of 35 parameters). Some species were found more frequently, namelyPhacus agilis Skuja, Ph. aenigmaticus Drez., Ph. caudatus Hübn., Ph. gigas Da Cunha, Ph. triqueter (Ehr.) Duj., Ph. longicauda (Ehr.) Duj.and Ph. tortus (Lemm.) Skv. Eighteen taxa were found in the sampling sites characterized by the following variation intervals of theenvironmental parameters: water temperature: 11.4–21.6 °C; pH: 6.2–7.5; dichromate oxidability: 10–59 mg l–1; conductivity: 145–779 µScm–1; nitrogen as NO3

–: n.d.–2.852 mg l–1; orthophosphate: n.d.–0.892 mg l–1; chloride: 14.2–109.3 mg l–1; sodium: 10.3–47.5 mg l–1 andtotal iron: 135–6446 µg l–1. In this work, information concerning the environmental conditions that preceded the occurrence of these speciesas well as results of the cytological and morphologic studies (with bright field microscopy as a resource) is presented and discussed.

© 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

Keywords: Phacus; Phytoplankton; Ecology; Water quality

1. Introduction

The genus Phacus includes free swimming unicellularorganisms, constituted by a euglenoid cell devoid of metabo-lism, usually backventrally flattened and possessing a rigidstriated pellicle, with a longitudinal or helicoidal arrange-ment. The cell more or less flattened (Phacus lismorensis,Phacus longicauda) could be straight or incurved (Phacushelikoides, Phacus tortus), sometimes presenting accentu-ated excavations (Phacus platyaulax) and could still presenta straight or incurved tail and cells with appreciable dimen-sions. In the anterior pole, at the sub-apical position, is theopening of the ampulla from where emerges a flagellum,which is responsible for the movement of the cell. Theampulla opens distally in a dilatation designated by a reser-voir, a bulbiform zone whose dimensions vary with the spe-cies, at the base of which two flagella are implanted. In thetransition zone reservoir/canal and external to this is aneyespot which is rectangular or has a more or less varied and

reddish form. At the base of the reservoir or near it, theeyespot coalesces a vacuole that forms in its proximity.

In the cytoplasm of the cell, several chloroplasts can befound, usually discoid and regularly disposed for practicallyall the outlying portions of the cell. The main reserve sub-stance is the paramylon, observable in several forms, fre-quently being small cylindrical sticks with round boards, butalso as rings with diverse configurations and dimensions (Ph.platyaulax, Phacus gigas), bobbins (Ph. longicauda), ortricks in the form of the cell in which they are contained(Phacus trypanon). The nucleus, with granular content, oc-cupies a median or sub-median position.

Most of the species of Phacus are euplanktonics, occur-ring together with species of other genes of Euglenophyta(Euglena, Lepocinclis and Trachelomonas) (Weik, 1967).The genus Euglena possesses species which can be found infreshwater in aerobioses or anaerobioses conditions. Somespecies are exposed to ultraviolet radiation or intense light;others seek expositions with an intermediate illuminationand turn away from either very intense light or of low inten-sities. The temperature can oscillate between 5 and 40 °C andit can be found at different levels of pH (Lackey, 1968). The

* Corresponding author.E-mail address: mverde@bio.ua.pt (M.J. Pereira).

Acta Oecologica 24 (2003) S33–S48

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dimensions, weight, content in nucleic acids and proteins aresubstantially altered by the pH in which Euglena gracilisgrows (Cook, 1981). The species of Euglena are usually-anaerobic facultative, with the ability to occur in placeshaving an abundance of sulphides. The places where speciesbelonging to the genes Euglena, Phacus and Trachelomonasare found can be rich in faeces and urine, easily developedand in high abundance. They also easily use, as an organicsubstratum, acetic and butyric acids, through the species ofEuglena, still requires, the vitamins of B complex for itsgrowth (Lackey, 1968). The lack of Fe, Mn and Mg not onlyalters the morphology of the cells of Euglena gracilis, butalso reduces the cellular multiplication (Hilt et al., 1987).Cook (1968) made a revision about the nutrition of Euglena,pointing out the beneficial effect of sulphur in sulphate way,phosphorous, vitamin B1, vitamin B12, of iron and zinc on itsgrowth. He also refers to the use of nitrates, ammonia andsome amino acids as a source of nitrogen. The carbon sourcesare very diverse, including carbohydrates, alcohols and car-boxylic acids.

In this work, information concerning the environmentalconditions that preceded the occurrence of several species ofPhacus as well as results of the cytological and morphologic

studies (with bright field microscopy as a resource) are pre-sented and discussed.

2. Materials and methods

2.1. Sampling sites

Twenty stations were selected (Fig. 1), distributed over theRivers Caima (Vale de Cambra—40°50.12 N 08°23.82 W,Barbeito—40°50.11 N 08°24.23 W), Antuã (Vila daLoureiro—40°46.87 N 08°30.56 W, Estarreja—40°45.00 N08°34.12 W), Vouga (Lamas do Vouga—40°38.53 N08°27.91 W, Segadães—40°36.68 N 08°30.92 W), Águeda(Águeda—40°34.40 N 08°27.04 W, Óis daRibeira—40°35.20 N 08°30.10 W), Levira (VilaVerde—40°30.80 N 08°30.83 W, Perrães—40°32.99 N08°29.82 W) and Cértima (Vale Estêvão—40°27.85 N08°27.60 W, S. João de Azenha— 40°29.84 N 08°27.42 W,Perrães—40°33.20 N 08°29.70 W), the remaining ones dis-tributed over the riversides: Ribeira da Horta (Eixo—40°37.60 N 08°33.23 W), Ribeira do Pano(Vessada—40°39.61 N 08°35.11 W, Ponte do

Fig. 1. Map with indication of the sampling places in the Caima River: (1) Vale de Cambra, (2) Barbeito; Antuã River: (3) Vila da Loureiro, (4) Estarreja; LeviraRiver: (5) Vila Verde, (6) Perrães; Cértima River: (7) Vale Estêvão, (8) São João de Azenha, (9) Perrães, (10) Espinhel, (11) Requeixo; Águeda River: (12)Águeda, (13) Óis da Ribeira; Vouga River: (14) Lamas do Vouga, (15) Segadães; (16) Canal of Segadães; (17) Canal of Frossos; Ribeira da Horta: (18) Eixo;Ribeira do Pano: (19) Vessada, (20) Ponte do Pano.

S34 M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

Pano—40°35.20 N 08°30.10 W), canals (Frossos—40°39.97 N 08°33.02 W and Segadães—40°36.62 N08°30.88 W) and a zone belonging to the Cértima River, butwith lagunar characteristics as in the case of Pateira deFermentelos, and also with two sampling points, one situatedin Espinhel (40°34.11 N 08°29.93 W) and another in Re-queixo (40°35.58 N 08°31.48 W) before the confluence withthe Águeda River.

2.2. Environmental parameters

Several parameters were measured: temperature (air andwater), pH, oxygen (dissolved and percentage of saturation),conductivity, mineralization, alkalinity (carbonate and bicar-bonate), BOD5, CQO (dichromate and permanganate), phos-phates, silica, ammonium, nitrites, nitrates, chlorides, Ca,Mg, Na, K, Fe, Zn, Cu, Mn (totals), in agreement withreference methods (Geerberg et al., 1992; Hall and Lucas,1981; Rodier, 1971).

2.3. Microscopical studies

The phytoplankton was collected with a net of nylonhaving a mesh-size of 25 µm. The collected material wassubdivided into two samples: one to be used for immediatestudy and the other for later studies. The latter one was fixedin the place of its crop with a formaldehyde solution to obtaina final concentration of 5%. Epiphytic, epipsamic, and epil-itic microalgae were also selected and conserved in the sameconditions.

The taxonomic study was carried out by making use of amicroscope of light base Leitz Biomed. The samples in-tended for the quantification of the abundance of differenttaxa present in the phytoplankton were cropped in a 1 l glassbottle and immediately fixed in a saturated mixtureiodine/iodide of potassium (lugol) 1 ml of this fixer wasadded for each 100 ml of the sample. After preparing theappropriate concentration, usually 50x, it was quantified us-ing Sedgwick-Rafter chambers, a microscope and by makinguse of the abundance quotations method (Frontier, 1969;Leitão, 1984) or by using the method described by Lund et al.(1958). Under the present conditions, the method of abun-dance quotations was used, while for not many abundantspecies, the method of Lund et al. (1958) was used. Insituations where there is a difficulty in the identification ofthe taxa, the inverted microscope is used as a resource (LeitzLabovert FS). For the identification of the taxa, several floraswere used (Asaul, 1975; Huber-Pestalozzi, 1955; Popova,1966; Popova and Safonova, 1976; Starmach, 1983).

2.4. Statistical treatment

With the results obtained for the 20 sampling sites andfrom the 26 samples cropped in each one, tables ofpresence/absence and respective abundance were con-structed. Using the same results, the averages for stationgrouped into nine periods were calculated.

The physical-chemical data and the abundance (x cel l–1)converted into ln (x+1) of different taxa (Gauch Jr., 1982)with a frequency equal or greater than five in a total of 2 yearsin the crop period, were treated by canonical correspondenceanalysis (CCA) using the computer program CANOCO, ver-sion 3.1 (Ter Braak, 1990). The set of environmental vari-ables, which best explain the species data was searched usingthe option “forward selection of environmental variables”.The statistical significance of the amount of variance addedby each variable was tested by the Monte Carlo permutationtest, using 19 permutations (P = 0.05). Only significantvariables were included. The environmental variables thatexplained better the occurrence of taxa were researchedusing the option “progressive selection of environmentalvariables”. The contribution of the variance of each variablewas tested using the test of permutations of Monte Carlo,using 19 permutations (P ≤ 0.05). Only the significant vari-ables were included.

The medium values for each selected parameter, as well asthe respective amplitude, were obtained using the followingformulas presented by Birks et al. (1990):

uk = �i = 1

n

yik xi/�i = 1

n

yik

tk = ��i = 1

n

yik� xi − uk �2/�

i = 1

n

yik�1/2

ûk is the optimum value to estimate for each taxon.yik is the abundance of each taxon k in sample i.xi is the value of the parameter in sample i.tk is the tolerance of each taxon for the parameter in cause.

2.5. Saprobic system

The formula proposed by Zelinka and Marvan (1961 inSládecek, 1973) was used to evaluate the qualityof the waterin different periods of sampling, with the help of algologicalinventory and respective abundance. For this the followingsaprobic valences proposed by Sládecek (1973) and Slá-decek and Perman (1978) for the different taxa were alsoused.Zelinka and Marvan

X = �i − 1

n

hi gi xi/�i − 1

n

hi gi

X is the saprobic level of the limnossaprobic zone, n is thenumber of taxa present in the sample, h is the absoluteabundance of the taxon, g is the indicative value of the taxonand x is the saprobic valency of the taxon at each level(Sládecek, 1973).

3. Results and discussion

Twenty-one species, belonging to the genus Phacus, wereidentified from the samples collected from the central regionof Portugal in lentic systems. The abundance of each taxonwas determined in 520 collected samples. Water samples

S35M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

were taken for the determination, by means of standardmethods, of physicochemical parameters (water tempera-ture, pH, organic matter (K2Cr2O7), conductivity, alkalinity,nitrogen as NH4

+, NO2– and NO3

–, phosphorus as orthophos-phate (PO4

3–) and metals in a total of 35 parameters).Some species were found with particular frequency,

namely, Phacus agilis Skuja, Ph. aenigmaticus Drez., Ph.caudatus Hübn., Ph. gigas Da Cunha, Ph. triqueter (Ehr.)Duj., Ph. longicauda (Ehr.) Duj. and Ph. tortus (Lemm.)Skv. All 21 taxa were found with major frequency and abun-dance in the sampling sites and were characterized by thefollowing variation intervals of the environmental param-eters: water temperature (11.4–21.6 °C), pH (6.2–7.5)dichromate oxidability (10–59 mg l–1), conductivity(145–779 µS cm–1), nitrogen as NO3

– (n.d.–2.852 mg l–1),orthophosphate (n.d.–0.892 mg l–1), chloride (14.2–109.3 mg l–1), sodium (10.3–47.5 mg l–1) and total iron (135–6446 µg l–1).

3.1. Environmental parameters

The physical-chemical parameters of the water revealedan expected variation of increment in spring and summer anddecrease in winter (Table 1). The nutrients showed an inversepattern. The environmental conditions showed the influenceof climate; in addition, the chemical composition of therocks, the nature of the substratum and the anthropogenicsubstances originating from industrial activities contributed alot to the organic matter content in the aquatic ecosystems.

3.2. Species ecology

As a result of the CCA, it was possible to project Fig. 2, inwhich the environmental variables and the taxa are repre-sented. The taxa are particularly distributed along quadrantstwo and three, along the negative segment of axis 1 and withthe association explained by water temperature, pH, conduc-tivity, organic matter, chloride (2a choice), sodium, potas-sium, iron and manganese totals and, to a lesser extent, silica.In quadrant 1 are distributed the associated forms of phos-phates, nitrites, nitrates, in contrast to the water temperatureand median to high values of pH, conductivity and alkalinity.Distributed along the positive segment of axis 1 and inquadrant four, are the associated taxa, mainly in spring,autumn and winter in a large amount of oxygenated water,with low mineralization, conductivity, pH, alkalinity, organicmatter, sodium, potassium and iron.

The species also distributed themselves particularly alongquadrants two and three. Euglenophyta are mainly distrib-uted along these quadrants, associated with medium to highvalues of water temperature, pH, organic matter, chloride,sodium, potassium, iron and manganese. In quadrants twoand three, it is possible to identify several species of Phacus,quadrant two: Ph. agilis, Ph. lismorensis, Ph. orbicularis,Ph. pleuronectes, Ph. triqueter; quadrant three: Ph. gigas,Ph. longicauda, Ph. tortus, Ph. trypanon. Ph. acuminatus,

Ph. aenigmaticus, Ph. caudatus, Ph. pyrum are distributedalong quadrant 1.

3.2.1. Phacus acuminatus Stokes var. variabilisLemmermann, 1899

Used code: PHAC, Fig. 6.The oval cells, lightly asymmetrical in relation to the

longitudinal axis and having a short tail acuminate, possess alength that varies between 28.5 and 29.3 µm, a width between21.5 and 22.1 µm and a thickness between 7.8 and 8.8 µm.This material presents dimensions that enchase within thosepresented by Weik (1967) for type (22–36 × 17–24 µm), aswell as those by Tell and Conforti (1986) and Németh (1997)(25–30 × 18–27 µm). Tell and Conforti (1986), for the varietyPh. acuminatus var. variabilis, 22.5 × 19.0 µm, values infe-rior to those found in our material.

This form was gathered in Cértima River (Vale Estêvão, S.João de Azenha, Perrães, Espinhel, Requeixo), Águeda River(Águeda, Óis da Ribeira), Antuã River (Vila da Loureiro,Estarreja), Levira River (Vila Verde, Perrães), Vouga River

Table 1Measured parameters and amplitudes of values found

Parameters Units AmplitudeWater temperature °C 5.7–30.0pH Sörensen Scale 5.4–8.4Conductivity µS cm–1 48.2–1392.5Mineralization mg l–1 58.2–1056.3Dissolved oxygen mg l–1 0.1–16.2Oxygen, percentage of saturation at 25 °C 1.1–168.4Oxidability to the KMnO4 mg l–1 n.d.–15.9Oxidability to the K2Cr2O7 mg l–1 n.d.–93BOD5 mg l–1 n.d.–53.1Alkalinity mg l–1 2.0–334.9Carbonates mg l–1 1.8–277.5Nitrogen (NH4

+) mg l–1 0.03–4.61Nitrogen (NO2

–) mg l–1 n.d.–0.492Nitrogen (NO3

–) mg l–1 n.d.–7.096Silica (SiO2) mg l–1 0.17–11.50Phosphorus (PO4

3–) mg l–1 n.d.–7.750Chloride (Cl–) mg l–1 6.0–238.0Calcium (Ca2+) mg l–1 2.0–256.0Magnesium (Mg2+) mg l–1 n.d.–52.2Sodium (Na+) mg l–1 2.6–136.6Potassium (K+) mg l–1 0.21–160.35Dissolved iron µg l–1 7–5000Dissolved manganese µg l–1 2–2045Dissolved aluminium µg l–1 n.d.–729Dissolved zinc µg l–1 n.d.–1624Dissolved nickel µg l–1 n.d.–54Dissolved copper µg l–1 n.d.–55Dissolved lead µg l–1 n.d.–705Total iron µg l–1 26–12240Total manganese µg l–1 3–4371Total aluminium µg l–1 39–9312Total zinc µg l–1 n.d.–2203Total nickel µg l–1 n.d.–67Total copper µg l–1 n.d.–138Total lead µg l–1 n.d.–3369

n.d., not detected.

S36 M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

(Lamas do Vouga, Segadães), canals of Segadães and Frossosand also in ribeira da Horta (Eixo) and Ribeira do Pano(Vessada, Ponte do Pano) (Fig. 1). It occurred predominantlyin the following conditions, with values for the studied pa-rameters and respective variation as: water temperature: 16.9± 3.2 °C (8.6–21.7); pH: 6.9 ± 0.5 (6.2-7.4); conductivity:483.7 ± 284.4 µS cm–1; bicarbonate: 129.8 ± 90.7 mg l–1;organic matter (KMnO4): 4.1 ± 2.8 mg l–1; organic matter(K2Cr2O7): 26 ± 16 mg l–1; orthophosphate: 0.446 ± 0.446mg l–1; silica: 4.06 ± 1.83 mg l–1; ammonium nitrogen: 0.77± 0.68 mg l–1; nitric nitrogen: 0.044 ± 0.044 mg l–1; nitrogenin nitrates way: 0.998 ± 0.998 mg l–1; chlorides: 45.5 ± 25.5

mg l–1; calcium: 57.1 ± 51.8 mg l–1; magnesium: 13.3 ± 10.4mg l–1; sodium: 27.0 ± 12.0 mg l–1; potassium: 4.09 ± 2.85mg l–1; total iron: 1682 ± 1652 µg l–1; total manganese: 248 ±220 µg l–1; total aluminium: 490 ± 448 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of xenossaprobics to a-mesossaprobics oc-curring predominantly in b-mesossaprobic environments.

3.2.2. Phacus aenigmaticus Drez epolski, 1925Used code: PHAE, Fig. 8.Dimensions: length, 30.4–31.3 µm; width, 7.8–9.6 µm;

thickness, 7.0 µm. The cells attenuated in a tail possess three

Fig. 2. Biplot of freshwater algae taxa and environmental variables in planes 1–2 of CCA. The arrows represent selected variables. µ scale, species; c scale,environmental variables; %, percentage variance of species data; k, eigenvalue. The more clear and entire squares correspond to Euglenophyta.

S37M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

large chloroplasts with disposition in each of the angles of thecell. Some forms reveal the presence of a haplopyrenoid ineach of the plasts. The flagellum presents a length similar tothat of the cell. This material presents dimensions slightlysuperior to the ones presented by Weik (1967) (17–24 ×10–13 µm), still indicating the spiral of the pellicle from theright to the left and several discoid chloroplasts appearingonly as one and having large size. Our materials appearsimilar to the variety model presented by Pochmann (1942)(22–32 × 9–15 µm), Huber-Pestalozzi (1955) (22–32 × 9–15µm), Tell and Conforti (1986) (22–32 × 9–15 µm) andNémeth (1997) (22–30 × 9–19 µm) particularly in terms ofdimensions. Wołowski (1998) mentions the species ofPh. striatus Francé (Syn.: Ph. aenigmatica Drez epolski1921/1922), having dimensions that are only slightly inferior

to this material (24.5–27.0 × 8.2 µm). The cell similar to Ph.aenigmaticus presents several chloroplasts. Also, Huber-Pestalozzi (1955) mentions the species Ph. striatus Francé,with lesser dimensions (20–24 × 4–9 µm).

This form was gathered in Cértima River (S. João daAzenha, Perrães, Espinhel, Requeixo), Águeda River (Óis daRibeira), Caima River (Vale de Cambra, Barbeito), AntuãRiver (Vila da Loureiro, Estarreja), Levira River (Vila Verde,Perrães), Vouga River (Lamas do Vouga, Segadães), in vala inSegadães, vala de Frossos, Ribeira da Horta (Eixo) andRibeira do Pano (Vessada, Ponte do Pano) (Fig. 1).

It occurred predominantly in the following conditionswith values for the studied parameters and respective varia-tion as: water temperature: 15.1 ± 3.7 °C (7.8–25.0 °C); pH:6.7 ± 0.5; 5.7–7.8); conductivity: 360.0 ± 215.2 µS cm–1;bicarbonate: 78.4 ± 65.1 mg l–1; organic matter (KMnO4):4.3 ± 2.7 mg l–1; organic matter (K2Cr2O7): 29 ± 15 mg l–1;orthophosphate: 0.228 ± 0.228 mg l–1; silica: 3.94 ± 1.61 mgl–1; ammonium nitrogen: 0.86 ± 0.77 mg l–1; nitric nitrogen:0.026 ± 0.026 mg l–1; nitrogen in nitrates way: 0.823 ± 0.823mg l–1; chlorides: 44.5 ± 30.3 mg l–1; calcium: 30.1 ± 26.1mg l–1; magnesium: 8.1 ± 7.5 mg l–1; sodium: 28.0 ± 17.7 mgl–1; potassium: 4.32 ± 2.70 mg l–1; total iron: 1752 ± 1352 µgl–1; total manganese: 266 ± 212 µg l–1; total aluminium: 431± 389 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of oligossaprobics to polissaprobics occur-ring predominantly in b-mesossaprobic environments.

3.2.3. Phacus agilis Skuja var. okobojiensis Allerge &Jahn, 1943

Used code: PHAG, Fig. 5The acuminated cells possess two big parietal chloroplasts

and small paramylon grains dispersed by the cytoplasm,besides two paramylon caps, perforated and parietal. Theaxial nucleus occupies a sub-median position. It was notpossible to observer the striation of the pellicle. This materialpresents dimensions (length, 13.8–16.4 µm; width,10.0–11.5 µm; thickness, 8.8 µm) coincident with those pre-sented by Huber-Pestalozzi (1955) (12–23 × 9–13 µm) andTell and Conforti (1986) (12.0–23.0 × 9.5–11.0 µm).Wołowski (1998) gives a representation similar to ours, with-out striation and indicating only the level of species. Hismaterial presents a variation between 15.1 and 18.3 × 9.2 µm.The description given by Skuja (1976) with respect to thespecies is similar either in terms of dimensions (13–17 ×8–11 µm) or morphology, if we exclude the slight striation inthe material referred by us here.

This form was gathered in Cértima River (Vale Estêvão, S.João da Azenha, Perrães, Espinhel, Requeixo), Águeda River(Águeda, Óis da Ribeira), Caima River (Barbeito), AntuãRiver (Vila da Loureiro, Estarreja), Levira River (Vila Verde,Perrães), in canals of Segadães and Frossos, Ribeira da Horta(Eixo) and Ribeira do Pano (Vessada, Ponte do Pano).

It occurred predominantly in the following conditionswith the values for the studied parameters and respective

Fig. 3. Phacus stokesii Lemmermann.

Fig. 4. Phacus skujai Skvortzow.

Fig. 5. Phacus agilis Skuja var. okobojiensis Allerge & Jahn.

S38 M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

variations as: water temperature: 15.9 ± 4.0 °C (7.7–25.0);pH: 6.8 ± 0.5; 5.7–7.8); conductivity: 456.2 ± 202.1 µS cm–1;bicarbonate: 106.1 ± 67.7 mg l–1; organic matter (KMnO4):5.0 ± 2.9 mg l–1; organic matter (K2Cr2O7): 34 ± 17 mg l–1;orthophosphate: 0.205 ± 0.205 mg l–1; silica: 3.96 ±1.74 mg l–1; ammonium nitrogen: 0.86 ± 0.77 mg l–1; nitricnitrogen: 0.025 ± 0.025 mg l–1; nitrogen in nitrates way:0.968 ± 0.968 mg l–1; chlorides: 54.9 ± 31.6 mg l–1; calcium:44.4 ± 31.6 mg l–1; magnesium: 11.8 ± 8.7 mg l–1; sodium:30.6 ± 13.1 mg l–1; potassium: 4.97 ± 2.94 mg l–1; total iron:2293 ± 1832 µg l–1; total manganese: 298 ± 208 µg l–1; totalaluminium: 450 ± 408 µg l–1. Wołowski (1998) indicates pHvalues (6.8–7.5) for its occurrence that practically coincidewith those mentioned in this work. This taxon was found inplaces characterized by the presence of a range ofb-mesossaprobics to a-mesossaprobics occurring predomi-nantly in b-mesossaprobic to a-mesossaprobic environ-ments.

3.2.4. Phacus caudatus Hübner, 1886Used code: PHCA, Fig. 7.

Dimensions: length, 33.1–36.2 µm; width, 16.0–21.2 µm;thickness, 10.6–11.8 µm, tail, 4.0 µm. The cells possess ashort and straight tail.

This material presents dimensions that are enchasingthemselves within those presented by Huber-Pestalozzi(1955) (31–50 × 15–25 µm), Weik (1967) (27–46 × 14–22µm), by Tell and Conforti (1986) (31–50 × 15–25 µm) and byWołowski (1998) (31.1–41.1 × 17.5–21.7 µm).

This form was gathered in sampling sites of Cértima River(Vale Estêvão, S. João de Azenha, Perrães, Espinhel, Re-queixo), Antuã River (Vila da Loureiro), Levira River (VilaVerde, Perrães), Vouga River (Lamas do Vouga, Segadães),canals of Segadães and Frossos, and also in Ribeira da Horta(Eixo) and Ribeira do Pano (Vessada, Ponte do Pano).

It occurred predominantly in following conditions withthe values for the studied parameters: water temperature:15.7 ± 3.5 °C (7.7–21.9 °C); pH: 6.9 ± 0.5 (5.7–7.4); conduc-tivity: 513.3 ± 251.7 µS cm–1; bicarbonate: 122.7 ± 82.0 mgl–1; organic matter (KMnO4): 3.9 ± 2.3 mg l–1; organic matter(K2Cr2O7): 27 ± 14 mg l–1; orthophosphate: 0.438 ± 0.438mg l–1; silica: 4.16 ± 1.44 mg l–1; ammonium nitrogen: 0.80± 0.71 mg l–1; nitric nitrogen: 0.043 ± 0.043 mg l–1; nitrogenin nitrates way: 1.238 ± 1.238 mg l–1; chlorides: 44.6 ± 17.9mg l–1; calcium: 54.5 ± 43.3 mg l–1; magnesium: 13.1 ± 9.9mg l–1; sodium: 30.4 ± 13.2 mg l–1; potassium: 3.86 ± 2.33mg l–1; total iron: 1624 ± 1451 µg l–1; total manganese: 275 ±241 µg l–1; total aluminium: 401 ± 359 µg l–1. Wołowski(1998) indicates pH values (7.0–7.7) for this species thatparticularly coincide with those referred to in this work.

This taxon was found in places characterized by the pres-ence of a range of oligossaprobics to a-mesossaprobics oc-curring predominantly in a-mesossaprobic environments.

3.2.5. Phacus gigas Da Cunha, 1913Used code: PHGI, Fig. 12.

Fig. 6. Phacus acuminatus Stokes var. variabilis Lemmermann.

Fig. 7. Phacus caudatus Hübner.

S39M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

Dimensions: length, 125.3–134.3 µm; width, 82.0–88.6µm; tail, 28.6–28.7 µm. The cells possess a longitudinalstriation that accompanies the cells’ contour. Several discoidplasts present a regular distribution in the whole cell. Acircular ring of paramylon frequentlyoccupies a median posi-tion in the cell, other rings, smaller and in large amounts, aredispersed by the cell, particularly in its inferior half. Thismaterial presents dimensions slightly superior to those givenby Huber-Pestalozzi (1955) (100 × 70 µm, tail 20 µm) andTell and Conforti (1986) (100–115 × 70–80 µm, tail,20–23 µm).

This form is relatively frequent in Cértima River, insteadof Espinhel and Requeixo, Levira River (Perrães), VougaRiver (Lamas do Vouga), canal of Segadães and Frossos and

Ribeira da Horta and Ribeira do Pano (Vessada, Ponte doPano), and in frequent conditions coincident with the follow-ing values for the studied parameters and respective varia-tions: water temperature: 18.1 ± 3.5 °C (12.4–25.0 °C); pH:6.9 ± 0.3 (5.9–7.5); conductivity: 460.4 ± 95.6 µS cm–1;bicarbonate: 148.1 ± 49.1 mg l–1; organic matter (KMnO4):5.7 ± 1.7 mg l–1; organic matter (K2Cr2O7): 34 ± 11 mg l–1;orthophosphate: 0.085 ± 0.051 mg l–1; silica: 5.92 ± 2.93 mgl–1; ammonium nitrogen: 0.84 ± 0.75 mg l–1; nitric nitrogen:0.009 ± 0.008 mg l–1; nitrogen in nitrates way: 0.287 ± 0.287mg l–1; chlorides: 58.7 ± 31.2 mg l–1; calcium: 49.0 ± 9.3 mgl–1; magnesium: 11.7 ± 5.7 mg l–1; sodium: 32.3 ± 11.5 mgl–1; potassium: 5.65 ± 1.73 mg l–1; total iron: 3884 ± 2562 µgl–1; total manganese: 523 ± 239 µg l–1; total aluminium: 327± 265 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to a-mesossaprobicsoccurring predominantly in b-mesossaprobic environments.

3.2.6. Phacus helikoides Pochmann, 1942Used code: PHHE, Fig. 19.

Dimensions: length, 105.0–149.5 µm; width, 45.0–52.0 µm.

Weik (1967) presents material with dimensions with avariation in length which is more restricted than that found inour material (125–126 × 48–50 µm); the material referred byWołowski (1998) being inferior either in length (81.5–94.0µm), or in width (33.5–38.0 µm). Our material is slightlysuperior in terms of length to that referred by Huber-Pestalozzi (1955) (70–120 × 30–54 µm). This form wasgathered in Pateira de Fermentelos (Cértima River) and inRibeira da Horta and Ribeira do Pano, in conditions charac-

Fig. 8. Phacus aenigmaticus Drez epolski.

Fig. 9. Phacus raciborskii Drez epolski.

S40 M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

terized by the presence of a range b-mesossaprobics toa-mesossaprobics.

3.2.7. Phacus horridus Pochmann, 1942Used code: PHHO, Fig. 11.

Dimensions: length, 35.6 µm; width, 22.2 µm; thickness,11.3–15.2 µm, tail, 6–5 µm. The material has inferior dimen-sions to those described by Tell and Conforti (1986) and tothose of Argentina (47–57 × 30–36 µm), but is superior tothose mentioned by Huber-Pestalozzi (1955) (30 × 22 µm).

This form was gathered in Cértima River (Espinhel, Re-queixo), Águeda River (Óis da Ribeira), Vouga River (Lamasdo Vouga), in the canal of Segadães and Ribeira da Horta andin Ribeira do Pano (Vessada, Ponte do Pano), in situationscharacterized by the presence of a range of b-mesossaprobicsto a-mesossaprobics occurring predominantly inb-mesossaprobic environments.

3.2.8. Phacus lismorensis Playfair, 1921Used code: PHLI, Fig. 16.Dimensions: length, 55.0–142.9 µm; width, 27.0–40.0

µm; thickness, 15.0 µm; tail, 39.5–57.1 µm. The cells possessa long, straight or oblique tail. The cell possesses a longitu-dinal striation, several discoid plasts and several paramylondiscoid grains one of them being prominent, flattened, centraland ventral. This material presents characteristics, as well asdimensions, that enchase, at least in part, within those pre-sented by Weik (1967) (128–145 × 38–56 µm; tail, 60–79µm). The values presented by Huber-Pestalozzi (1955)(85–100 × 30 µm; tail, 35–40 µm) are inferior limits com-pared to the values represented here. This form was gatheredin Rivers Cértima (Perrães, Espinhel), Levira (Perrães), andin the canal of Frossos and Ribeira da Horta (Fig. 1). Itoccurred predominantly in the following conditions: watertemperature: 16.4 ± 2.9 °C (12.7–20.0 °C); pH: 6.9 ± 0.4(6.4–6.7); conductivity: 565.2 ± 122.5 µS cm–1; bicarbonate:138.3 ± 52.9 mg l–1; organic matter (KMnO4): 4.6 ± 2.2 mgl–1; organic matter (K2Cr2O7): 31 ± 16 mg l–1; orthophos-phate: 0.108 ± 0.073 mg l–1; silica: 3.47 ± 1.45 mg l–1;ammonium nitrogen: 0.81 ± 0.72 mg l–1; nitric nitrogen:0.020 ± 0.018 mg l–1; nitrogen in nitrates way: 1.212 ± 1.057mg l–1; chlorides: 61.1 ± 30.0 mg l–1; calcium: 53.9 ± 19.7mg l–1; magnesium: 16.2 ± 9.8 mg l–1; sodium: 30.1 ± 9.2 mgl–1; potassium: 4.62 ± 2.16 mg l–1; total iron: 2056 ± 1734 µgl–1; total manganese: 287 ± 173 µg l–1; total aluminium: 324± 282 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to a-mesossaprobicsoccurring predominantly in a-mesossaprobic environments.

3.2.9. Phacus longicauda (Ehrenberg) Dujardin, 1841Used code: PHLO, Fig. 17.Dimensions: length, 141.8–157.5 µm; width, 52.4–64.3

µm; thickness, 34.1 µm; tail, 58.8–62.9 µm. The cells possessa long, straight tail. The cell possesses a longitudinal striationthat accompanies the cells’ contour. A bobbin of paramylonoccupies a central position, possessing, in its posterior por-tion, the accommodated nucleus. Weik (1967) presents mate-rial with dimensions (122–179 × 47–63 µm; tail, 54–96 µm),as well as characteristics that enchase within those presentedin this work. The materials referred by Skuja (1976) (90–160× 40–62 µm), Huber-Pestalozzi (1955) (85–190 × 40–70 µm)and Tell and Conforti (1986) for the variety model (85–160 ×40–70 µm) coincide with our material in its superior limits.The variety model given by Wołowski (1998) possesses infe-rior dimensions (81.0–97.0 × 22.0–41.0 µm) compared to the

Fig. 10. Phacus platyaulax Pochmann.

S41M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

material studied by us. The pH values (7.5–8.0) presented areslightly superior.

This form was gathered in Rivers Caima (Vale de Cam-bra), Levira (Perrães), Cértima (Perrães, Espinhel, Re-queixo), in the canal of Frossos and Ribeira da Horta andRibeira do Pano in Ponte do Pano, predominantly in thefollowing conditions: water temperature: 18.1 ± 3.5 °C(7.7–25.0 °C); pH: 7.1 ± 0.4 (5.7–7.4); conductivity: 494.1 ±108.8 µS cm–1; bicarbonate: 136.6 ± 40.5 mg l–1; organicmatter (KMnO4): 5.5 ± 3.6 mg l–1; organic matter (K2Cr2O7):37 ± 21 mg l–1; orthophosphate: 0.107 ± 0.074 mg l–1; silica:3.84 ± 1.06 mg l–1; ammonium nitrogen: 0.85 ± 0.76 mg l–1;nitric nitrogen: 0.019 ± 0.019 mg l–1; nitrogen in nitrates

way: 0.741 ± 0.741 mg l–1; chlorides: 68.1 ± 41.2 mg l–1;calcium: 47.9 ± 15.8 mg l–1; magnesium: 16.3 ± 8.9 mg l–1;sodium: 34.0 ± 10.6 mg l–1; potassium: 5.54 ± 3.56 mg l–1;total iron: 1521 ± 1445 µg l–1; total manganese: 302 ± 197 µgl–1; total aluminium: 354 ± 264 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of oligossaprobics to a-mesossaprobics oc-curring predominantly in b-mesossaprobic environments.

3.2.10. Phacus orbicularis Hübner, 1886Used code: PHOR, Fig. 13.

The cells are practically circular, with a length of63.0–71.7 µm; width, 45.2–47.8 µm; thickness, 11.3–19.6µm, tail, 12.2–15.2 µm. The cells possess a longitudinalstriation that accompanies the cells’ contour. Several discoidplasts present a regular distribution in the whole cell. Acircular ring of paramylon occupies a median position in thecell, other smaller ones and those in small amount are dis-persed by the cell. The axial nucleus occupies a sub-medianposition, below the central ring of paramylon.

This material presents dimensions that enchase withinthose referred by Huber-Pestalozzi (1955) (50–100 × 30–60µm), as well as characteristics, that enchase within thosereferred by Weik (1967) (45–74 × 30–50 µm; tail, 7–17 µm),Tell and Conforti (1986) (32–100 × 22–60 µm, tail, 19–25µm) and Wołowski (1998) (46.0–67.5 × 19.5–46.5 µm) forPh. orbicularis fo. orbicularis. This taxon was found inseveral sampling sites in rivers Cértima (Vale Estêvão, Per-rães, Requeixo), Águeda (Óis da Ribeira), Levira (Perrães),Vouga (Lamas do Vouga), in the canal of Segadães andFrossos, Ribeira da Horta and in Ribeira do Pano (Vessada,Ponte do Pano).

It occurred predominantly in the following conditionswith the values for the studied parameters and respectivevariation as: water temperature: 16.2 ± 3.6 °C (7.7–25.0 °C);pH: 6.7 ± 0.5 (5.7–7.5); conductivity: 452.9 ± 113.3 µS cm–1;bicarbonate: 106.4 ± 59.5 mg l–1; organic matter (KMnO4):

Fig. 11. Phacus horridus Pochmann.

Fig. 12. Phacus gigas Da Cunha.

S42 M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

6.6 ± 2.9 mg l–1; organic matter (K2Cr2O7): 41 ± 13 mg l–1;orthophosphate: 0.101 ± 0.101 mg l–1; silica: 3.91 ± 1.89 mgl–1; ammonium nitrogen: 1.02 ± 0.93 mg l–1; nitric nitrogen:0.016 ± 0.016 mg l–1; nitrogen in nitrates way: 0.526 ± 0.526mg l–1; chlorides: 67.6 ± 32.1 mg l–1; calcium: 39.4 ± 16.5mg l–1; magnesium: 11.2 ± 4.6 mg l–1; sodium: 34.9 ± 11.3mg l–1; potassium: 6.57 ± 2.86 mg l–1; total iron: 2744 ± 1464µg l–1; total manganese: 439 ± 436 µg l–1; total aluminium:584 ± 542 µg l–1. Wołowski (1998) attributes the occurrenceof Ph. orbicularis fo. orbicularis to pH values between 6.6and 7.6, which are values that practically coincide with thesuperior limit in the species found by us.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to a-mesossaprobicsoccurring predominantly in b-mesossaprobic environments.

3.2.11. Phacus platyaulax Pochmann, 1942Used code: PHPL, Fig. 10.Dimensions: length, 36.2–38.9 µm; width, 26.2–31.5 µm;

thickness, 12.0–19.6 µm. The cells possess a short and in-curved tail. The cell possesses several discoid plasts and twoellipsoid and perforated paramylon grains, prominent, with alateral position in the cell. In our material, the dimensionsenchase themselves within that described by Tell and Con-forti (1986) (30–38 × 22–28 µm), the gamut of amplitudepresented by Pochmann (1942) and Huber-Pestalozzi (1955)(36–38 × 27–28 µm) being slightly less.

This form was gathered in Rivers Cértima (Vale Estêvão,S. João de Azenha, Perrães, Espinhel, Requeixo), Caima(Barbeito), Levira (Perrães), in the canal of Segadães andFrossos and in Ribeira da Horta and Ribeira do Pano (Ves-sada, Ponte do Pano).

It occurred predominantly in following conditions withthe values for the studied parameters and respective variationas: water temperature: 16.1 ± 3.8 °C (9.0–25.0 °C); pH: 6.8 ±0.5 (5.7–7.5); conductivity: 513.0 ± 185.2 µS cm–1; bicar-bonate: 120.2 ± 70.8 mg l–1; organic matter (KMnO4): 5.9 ±2.7 mg l–1; organic matter (K2Cr2O7): 40 ± 15 mg l–1;orthophosphate: 0.186 ± 0.186 mg l–1; silica: 3.78 ± 1.69 mgl–1; ammonium nitrogen: 1.23 ± 1.01 mg l–1; nitric nitrogen:0.021 ± 0.021 mg l–1; nitrogen in nitrates way: 0.416 ± 0.416mg l–1; chlorides: 68.2 ± 34.1 mg l–1; calcium: 47.2 ± 28.6mg l–1; magnesium: 13.0 ± 8.1 mg l–1; sodium: 35.0 ± 10.5mg l–1; potassium: 5.90 ± 2.71 mg l–1; total iron: 2399 ± 1503µg l–1; total manganese: 318 ± 229 µg l–1; total aluminium:527 ± 485 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to a-mesossaprobicsoccurring predominantly in a-mesossaprobic environments.

3.2.12. Phacus pleuronectes (O.F. Mueller) Dujardin, 1841Used code: PHPE, Fig. 14.Dimensions: length, 46.1 µm; width, 31.3 µm; thickness;

tail, 5.5 µm. Very similar in form to Ph. orbicularis, butsmaller and presenting ovoid cells and the anterior pole isattenuated. The cell presents several paramylon discs, par-ticularly dispersed in the anterior portion of the cell. One ofthe grains occupies an approximately central position andpossesses large dimensions. Several and discoid chloroplastsoccupy the anterior portion of the cell. This material presentsdimensions that enchase within those presented by Huber-Pestalozzi (1955) (40–80 × 30–50 µm), Weik (1967) (33–58× 25–42 µm; tail, 5–10 µm) and in terms of the descriptionand inferior limits of dimensions (40–100 × 29–70 µm; tail,5–7 µm) presented by Tell and Conforti (1986) in the varietymodel. The variety model described by Wołowski (1998) isslightly lesser in terms of dimensions (24.0–44.7 × 17.5–34.0 µm) than the forms found in our material.

Fig. 13. Phacus orbicularis Hübner.

Fig. 14. Phacus pleuronectes (O.F. Mueller) Dujardin.

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Species sampled in Levira River (Perrães), Cértima River(Perrães, Espinhel, Requeixo) and in the canal of Segadães.

3.2.13. Phacus pyrum (Ehrenberg) Stein, 1878Used code: PHPY, Fig. 21.Dimensions: length, 40.6 µm; width, 17.5 µm; thickness,

16.3 µm; tail, 13.9 µm. The cells possess two lateral caps of

paramylon besides small discoid rings dispersed by the cyto-plasm. For this species, Huber-Pestalozzi (1955) mentionsdimension of 30–55 × (7?)–21 µm and Wołowski (1998)mentions the following dimensions: 28.3–51.0 × 12.0–21.1µm. Németh (1997) refers to this species treaty as a varietymodel, using the same values as those of Pochmann (1942),which are presented by Huber-Pestalozzi (1955). This authorstill associates this species, at variety level, Phacus rudiculaand Phacus trypanon, with the same dimensions referred byPochmann (1942) and Huber-Pestalozzi (1955).

This form was gathered in Rivers Cértima (Vale Estêvão,S. João de Azenha, Perrães, Espinhel, Requeixo), Águeda(Águeda, Óis da Ribeira), Antuã (Estarreja), Levira (VilaVerde, Perrães), Vouga (Lamas do Vouga) and in the canal ofSegadães and Frossos, and Ribeira da Horta and Ribeira doPano (Vessada, Ponte do Pano).

It occurred predominantly in the following conditionswith the values for the studied parameters and respectivevariation: water temperature: 15.6 ± 3.2 °C (11.2–21.4 °C);pH: 6.8 ± 0.6 (5.7–7.8); conductivity: 510.0 ± 268.9 µS cm–1;bicarbonate: 115.4 ± 89.6 mg l–1; organic matter (KMnO4):4.2 ± 2.8 mg l–1; organic matter (K2Cr2O7): 28 ± 15 mg l–1;orthophosphate: 0.384 ± 0.384 mg l–1; silica: 3.92 ± 1.31 mgl–1; ammonium nitrogen: 0.74 ± 0.65 mg l–1; nitric nitrogen:0.032 ± 0.032 mg l–1; nitrogen in nitrates way: 0.891 ± 0.891mg l–1; chlorides: 47.7 ± 25.5 mg l–1; calcium: 54.0 ± 47.0mg l–1; magnesium: 12.8 ± 9.3 mg l–1; sodium: 29.6 ± 14.3mg l–1; potassium: 4.23 ± 2.76 mg l–1; total iron: 1378 ± 1282µg l–1; total manganese: 255 ± 218 µg l–1; total aluminium:520 ± 478 µg l–1. Wołowski (1998) mentions pH valuesbetween 6.8 and 8.9 for its occurrence.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to a-mesossaprobicsoccurring predominantly in b-mesossaprobic toa-mesossaprobic environments.

3.2.14. Phacus raciborskii Drez epolski, 1925Used code: PHRA, Fig. 9.Dimensions: length, 40.0–53.1 µm; width, 11.9–15.6 µm.

The material have superior dimensions to those provided byPochmann (1942) and Huber-Pestalozzi (1955) (35 × 10–12µm), being situated in the superior limit of those given byWołowski (1998): 34.0–41.0 × 10.5–16.5 µm. This authorstill refers to its occurrence at pH between 6.8 and 8.4.

This form was gathered in Cértima River (Perrães, Espin-hel, Requeixo), the canal of Segadães and Ribeira do Pano(Ponte do Pano), in places characterized by the presence of arange of b-mesossaprobics to a-mesossaprobics occurringpredominantly in a-mesossaprobic environments.

3.2.15. Phacus rudicula (Playfair) Pochmann, 1942Used code: PHRU, Fig. 22.Dimensions: length, 46.9–53.1 µm; width, 15.0–22.5 µm;

thickness, 11.3–18.8 µm; tail, 17.5–18.8 µm. The cells pos-sess two lateral paramylon caps besides small discoid ringsdispersed by the cytoplasm. The pellicle appears spiralled, to

Fig. 15. Phacus triqueter (Ehrenberg) Dujardin.

Fig. 16. Phacus lismorensis Playfair.

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the right, with 6–8 grooves. Huber-Pestalozzi (1955) men-tions the same values as those of Pochmann (1942) for thisspecies (24–35 × 15–26 µm; tail, 14–18 µm).

This taxon was gathered from Rivers Cértima (S. João deAzenha, Perrães, Espinhel, Requeixo), Águeda (Águeda, Óisda Ribeira), Caima (Barbeito), Antuã (Estarreja), Levira(Perrães), Vouga (Lamas do Vouga, Segadães), the canal ofSegadães and Frossos and Ribeira da Horta and in Ribeira doPano (Vessada, Ponte do Pano).

It occurred predominantly in following conditions withthe values for the studied parameters and respective varia-tions: water temperature: 15.0 ± 3.2 °C (7.7–22.0 °C); pH:6.6 ± 0.5 (5.7–7.4); conductivity: 391.8 ± 189.8 µS cm–1;bicarbonate: 73.0 ± 53.2 mg l–1; organic matter (KMnO4):5.3 ± 3.0 mg l–1; organic matter (K2Cr2O7): 32 ± 15 mg l–1;orthophosphate: 0.131 ± 0.131 mg l–1; silica: 3.77 ± 1.19 mgl–1; ammonium nitrogen: 0.69 ± 0.60 mg l–1; nitric nitrogen:0.022 ± 0.022 mg l–1; nitrogen in nitrates way: 0.825 ± 0.825mg l–1; chlorides: 48.8 ± 28.5 mg l–1; calcium: 32.9 ± 22.2mg l–1; magnesium: 8.6 ± 5.9 mg l–1; sodium: 28.0 ± 11.9 mgl–1; potassium: 5.28 ± 3.02 mg l–1; total iron: 2150 ± 1396 µgl–1; total manganese: 246 ± 205 µg l–1; total aluminium: 530± 488 µg l–1. This taxon was found in places characterized bythe presence of a range of oligossaprobics toa-mesossaprobics occurring predominantly inb-mesossaprobic environments.

3.2.16. Phacus similis Christen, 1962

Used code: PHSI.The taxon was collected in several places: rivers Caima

(Barbeito), Antuã (Estarreja), Levira in Perrães, Cértima(Perrães, Espinhel, Requeixo), Águeda (Óis da Ribeira),Vouga (Lamas do Vouga, Segadães), in the canal of Segadãesand Frossos and in Ribeira da Horta and Ribeira do Pano(Vessada, Ponte do Pano). The values for the studied param-eters and respective variations are as follow: water tempera-ture: 14.4 ± 3.2 °C (7.7–21.0 °C); pH: 6.5 ± 0.4 (5.7–7.0);conductivity: 386.2 ± 192.9 µS cm–1; bicarbonate: 72.7 ±53.4 mg l–1; organic matter (KMnO4): 6.2 ± 3.3 mg l–1;organic matter (K2Cr2O7): 39 ± 16 mg l–1; orthophosphate:0.152 ± 0.152 mg l–1; silica: 3.79 ± 1.16 mg l–1; ammoniumnitrogen: 0.98 ± 0.89 mg l–1; nitric nitrogen: 0.022 ± 0.022mg l–1; nitrogen in nitrates way: 0.419 ± 0.419 mg l–1;chlorides: 59.0 ± 37.4 mg l–1; calcium: 30.4 ± 17.3 mg l–1;magnesium: 8.4 ± 6.5 mg l–1; sodium: 31.1 ± 15.3 mg l–1;potassium: 6.16 ± 3.27 mg l–1; total iron: 2306 ± 1554 µg l–1;total manganese: 193 ± 159 µg l–1; total aluminium: 374 ±330 µg l–1. Wołowski (1998) indicates pH values of 6.8–7.0in environment which were found to be coincident with oursuperior limit.

This taxon was found in places characterized by the pres-ence of a range of oligossaprobics to polissaprobics occur-ring predominantly in b-mesossaprobic environments.

3.2.17. Phacus skujai Skvortzow, 1928Used code: PHSK, Fig. 4.Fig. 17. Phacus longicauda (Ehrenberg) Dujardin.

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Dimensions: length, (15.0) 17.5–24.0 µm; width, 7.5–12.5µm; thickness, 5.6–6.3 µm. It is a form consisting of anobliquely truncated pole and a posterior pole acuminate thatpossesses a section approximately elliptical with a medianconcave re-entrant. The longitudinal section appears convexin the ventral face and concave in the anterior portion up tothe middle of the cell, then appears convex up to the attenu-ation that delimits the beginning of the posterior pole acumi-nation. Their cells possess a red and elongated eyespot,several discoid plasts (>16) of about 3 µm diameter. Thecytoplasm shows one or two paramylon rings with a smalland circular perforation. The reservoir, spherical and sub-apical allows the flagellum of about half of the cell length toexit. This material presents dimensions similar to those pre-sented by Pochmann (1942) (13–33 × 5–11 × 3–4 µm),Huber-Pestalozzi (1955) (13–33 × 5–11 µm), Weik (1967)(22 × 11 µm) and Tell and Conforti (1986) (13–30 × 5–17µm). The paramylon discs are not oblong, as mentioned byWeik (1967) but are discoid. The form was gathered in CaimaRiver (Barbeito), Antuã River (Vila da Loureiro, Estarreja),Levira River (Vila Verde, Perrães), Cértima River (Vale Es-têvão, S. João de Azenha, Perrães, Espinhel, Requeixo),Águeda River (Óis da Ribeira), Vouga River (Lamas doVouga, Segadães), in the canal of Segadães and Frossos andalso in Ribeira da Horta and Ribeira do Pano (Vessada, Pontedo Pano).

The values for the studied parameters and respectivevariations are as follows: water temperature: 15.7 ± 3.3 °C(9.0–22.0 °C); pH: 6.9 ± 0.5 (5.7–7.8); conductivity: 512.5 ±

196.2 µS cm–1; bicarbonate: 117.4 ± 68.1 mg l–1; organicmatter (KMnO4): 4.5 ± 3.1 mg l–1; organic matter (K2Cr2O7):31 ± 19 mg l–1; orthophosphate: 0.286 ± 0.286 mg l–1; silica:3.84 ± 1.37 mg l–1; ammonium nitrogen: 0.78 ± 0.69 mg l–1;nitric nitrogen: 0.038 ± 0.038 mg l–1; nitrogen in nitratesway: 1.426 ± 1.426 mg l–1; chlorides: 54.0 ± 32.4 mg l–1;calcium: 52.3 ± 37.8 mg l–1; magnesium: 12.1 ± 7.3 mg l–1;sodium: 32.2 ± 15.3 mg l–1; potassium: 4.53 ± 3.11 mg l–1;total iron: 1491 ± 1356 µg l–1; total manganese: 248 ± 237 µgl–1; total aluminium: 426 ± 373 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to polissaprobics occur-ring predominantly in b-mesossaprobic environments.

3.2.18. Phacus stokesii Lemmermann, 1901Used code: PHSE, Fig. 3.Dimensions: length, 41.8 µm; width, 30.6 µm. Pochmann

(1942) mentions a length of 13–20 µm and a width of12–15 µm. Huber-Pestalozzi (1955) mentions a length of46–48 µm and a width of 39.0–41.6 µm. Wołowski (1998)mentions the following dimensions for this species:36.5–40.0 × 33.5–36.0 µm and a pH value of 8.3 for itsoccurrence. This material enchases itself within the dimen-sions given by Németh (1997) for Ph. stokesii f. stokesii(37.2–48 × 30–41.6 µm) and within those referred byWołowski (1998) as an inferior limit and those of Huber-

Fig. 18. Phacus tortus (Lemmermann) Skvortzow.

Fig. 19. Phacus helikoides Pochmann.

S46 M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

Pestalozzi (1955) as a superior limit for species. It is a speciesidentified from samples of Pateira de Fermentelos in Espin-hel (Fig. 1).

3.2.19. Phacus tortus (Lemmermann) Skvortzow, 1928Used code: PHTO, Fig. 18.Dimensions: length, 111.3 µm; width, 53.1 µm; tail,

50.0 µm. The cells possess a long and straight tail. Ourmaterial coincides with the superior limit of the interval ofdimensions given by Huber-Pestalozzi (1955) (80–112 ×38–52 µm), whereas the dimension of the material of Weik(1967) (63–100 × 26–48 µm; tail, 25–38 µm) are slightlyinferior to ours.

The taxon gathered in Rivers Caima (Barbeito), Antuã(Estarreja), Levira (Perrães), Cértima (S. João de Azenha,Perrães, Espinhel, Requeixo), Vouga (Lamas do Vouga), inthe canal of Segadães and Frossos and also in Ribeira daHorta and Ribeira do Pano (Vessada, Ponte do Pano).

The values for the studied parameters and respectivevariations are as follow: water temperature: 17.4 ± 3.6 °C(7.7–25.0 °C); pH: 6.7 ± 0.5 (5.7–7.8); conductivity: 412.6 ±139.6 µS cm–1; bicarbonate: 104.0 ± 62.6 mg l–1; organicmatter (KMnO4): 6.7 ± 3.7 mg l–1; organic matter (K2Cr2O7):40 ± 18 mg l–1; orthophosphate: 0.082 ± 0.082 mg l–1; silica:4.26 ± 2.15 mg l–1; ammonium nitrogen: 0.93 ± 0.84 mg l–1;nitric nitrogen: 0.013 ± 0.013 mg l–1; nitrogen in nitratesway: 0.374 ± 0.374 mg l–1; chlorides: 63.5 ± 33.1 mg l–1;calcium: 40.5 ± 26.7 mg l–1; magnesium: 11.1 ± 7.1 mg l–1;sodium: 34.2 ± 12.7 mg l–1; potassium: 6.73 ± 3.69 mg l–1;total iron: 2933 ± 2151 µg l–1; total manganese: 422 ± 405 µgl–1; total aluminium: 594 ± 552 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to polissaprobics occur-ring predominantly in a-mesossaprobic environments.

3.2.20. Phacus triqueter (Ehrenberg) Dujardin, 1841Used code: PHTR, Fig. 15.

Dimensions: length, 73.3 µm; width, 44.3 µm; thickness,17.6 µm; tail, 11.9 µm. This material presents dimensions, aswell as characteristics, that enchase within those presentedby Weik (1967) (52–82 × 35–51 µm; tail, 7–14 µm), beingslightly superior to those of Skuja (1976) (37–50 × 30–35µm), Huber-Pestalozzi (1955) (37–68 × 30–45 µm), Tell andConforti (1986) (37–68 × 30–45 µm; tail, 7–8 µm) andclearly superior to those of Wołowski (1998) (40.0 ×24.0–27.0 µm).

The form was gathered in Cértima River (Vale Estêvão, S.João de Azenha, Perrães, Espinhel, Requeixo), Águeda River(Óis da Ribeira), Antuã River (Estarreja), Levira River (Per-rães) and in the canal of Segadães and Frossos and Ribeira daHorta and Ribeira do Pano (Ponte do Pano). The values forthe studied parameters and respective variations are as fol-low: water temperature: 17.9 ± 3.7 °C (10.6–25.0 °C); pH:6.9 ± 0.4 (6.1–7.4); conductivity: 460.3 ± 178.2 µS cm–1;bicarbonate: 124.2 ± 73.9 mg l–1; organic matter (KMnO4):5.0 ± 2.9 mg l–1; organic matter (K2Cr2O7): 34 ± 16 mg l–1;orthophosphate: 0.268 ± 0.268 mg l–1; silica: 4.35 ± 2.03 mgl–1; ammonium nitrogen: 0.86 ± 0.77 mg l–1; nitric nitrogen:0.042 ± 0.042 mg l–1; nitrogen in nitrates way: 0.693 ± 0.693mg l–1; chlorides: 52.8 ± 25.0 mg l–1; calcium: 52.0 ± 45.2mg l–1; magnesium: 14.1 ± 10.5 mg l–1; sodium: 32.0 ± 11.4mg l–1; potassium: 5.04 ± 2.86 mg l–1; total iron: 2344 ± 2175µg l–1; total manganese: 364 ± 293 µg l–1; total aluminium:578 ± 536 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to a-mesossaprobicsoccurring predominantly in b-mesossaprobic environments.

Fig. 20. Phacus trypanon Pochmann.

Fig. 21. Phacus pyrum (Ehrenberg) Stein.

Fig. 22. Phacus rudicula (Playf.) Pochmann.In all the figures of Phacus, the scale bars represent 10 µm.

S47M.J. Pereira, U.M.M. Azeiteiro / Acta Oecologica 24 (2003) S33–S48

3.2.21. Phacus trypanon Pochmann, 1942Used code: PHTY, Fig. 20.Dimensions: length, 41.7–43.9 µm; width, 17.8–21.7 µm;

tail, 15.2–18.3 µm. The cells possess two lateral paramyloncaps besides small discoid rings dispersed by the cytoplasm.Huber-Pestalozzi (1955) (28–30 × 17–18 µm) and Weik(1967) present material with dimensions inferior (31–32 ×13–14 µm; tail, 12–14 µm) to ours, presenting 7–8 groovesand two paramylon parietal caps. It seems similar to Ph.pseudonordstedtii (Pochmann, 1942), this being the lastovate and appearing more flattened. Ph. trypanon is orbicu-lar, and symmetric in the anterior pole. Wołowski (1998)mentioned the following dimensions for this species:23.0–30.5 × 11.5–14.5 µm and a pH value of 7.5 for itsoccurrence. This taxon was collected in several places, rivers,canals and swamps (Cértima River—Vale Estêvão, Perrães,Espinhel, Requeixo; Águeda River—Óis da Ribeira; LeviraRiver—Vila Verde, Perrães; canal of Segadães; canal of Fros-sos; Ribeira da Horta; Ribeira do Pano—Vessada, Ponte doPano) (Fig. 1). It occurred predominantly in following con-ditions with the values for the studied parameters and respec-tive variation as: water temperature: 16.5 ± 3.8 °C (11.2–25.0°C); pH: 6.6 ± 0.5 (5.7–7.5); conductivity: 420.0 ± 156.9 µScm–1; bicarbonate: 92.2 ± 57.2 mg l–1; organic matter(KMnO4): 5.7 ± 3.0 mg l–1; organic matter (K2Cr2O7): 36 ±16 mg l–1; orthophosphate: 0.102 ± 0.102 mg l–1; silica: 4.02± 1.76 mg l–1; ammonium nitrogen: 1.03 ± 0.96 mg l–1; nitricnitrogen: 0.018 ± 0.018 mg l–1; nitrogen in nitrates way:0.384 ± 0.384 mg l–1; chlorides: 62.6 ± 36.3 mg l–1; calcium:35.5 ± 19.9 mg l–1; magnesium: 9.4 ± 5.3 mg l–1; sodium:33.0 ± 14.0 mg l–1; potassium: 5.69 ± 2.97 mg l–1; total iron:2819 ± 1812 µg l–1; total manganese: 336 ± 282 µg l–1; totalaluminium: 575 ± 533 µg l–1.

This taxon was found in places characterized by the pres-ence of a range of b-mesossaprobics to a-mesossaprobicsoccurring predominantly in a-mesossaprobic environments.

4. Conclusion

The 21 taxa were found in the sampling sites character-ized by the following variation intervals of the environmentalparameters: water temperature 11.4–21.6 °C; pH: 6.2–7.5;dichromate oxidability: 10–59 mg l–1; conductivity: 145–779µS cm–1, nitrogen as NO3

–: n.d.–2.852 mg l–1; orthophos-phate: n.d.–0.892 mg l–1; chloride: 14.2–109.3 mg l–1; so-dium 10.3–47.5 mg l–1 and total iron: 135-6446 µg l–1. In thefuture, other parameters should be studied in order to obtain abetter insight into the distribution and biology of the genus.

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