Algological Studies 124 71-83 Stuttgart, July 2007

Ecology of benthic diatoms from LakeMacro Prespa (Macedonia)

ZLATKO LEVKOV , SAUL BiANCO2^, SVETISLAV KRSTICI ,TEOFIL NAKOV and Luc EciOR3

11nstitute of Biology, Faculty of Natural Sciences, Skopje,Republic of Macedonia.2Area de Ecologi'a, Universidad de Leon, Leon, SpainsRublic Research Center- Gabriel Lippmann, Department Environment andAgro-biotechnologies, Belvaux, Grand-Duchy of Luxembourg

With 4 figures and 2 tables

Abstract: Lake Prespa belongs to the group of ancient lakes. By subterranean channels itis connected with Lake Ohrid. In the past two decades, Lake Prespa has been character-ized by a decrease of its water level and an increased cultural and natural eutrophication.In this period, very few ecological studies were performed, based mainly on compositionand biomass of the phytoplankton community. From June 2002 to May 2003 analyses of18 physical and chemical parameters and composition of benthic diatoms were per-formed on 12 sampling sites of Lake Macro Prespa. About 300 diatom taxa were identi-fied in the lake. Relative abundances were calculated by counting 200 diatom valves, and143 diatom taxa had abundances of more than 1 % in at least one sampling site. Deepbenthic communities were dominated by Cyclotella ocellata and Diploneis mauleri,while in the littoral region these communities were dominated by small Navicula sensulato species. For statistical analyses, the 17 most abundant diatom taxa (> 1 % in totalabundance) were used. Contrarily to the expectations, TP had a negligible influence ondiatom community structure. The main environmental factors controlling species distri-bution and abundances were ammonium and metallic cations (Cu, Mn, K) and, secondar-ily, dissolved oxygen and Secchi depth, as inferred from both correlation and multivariate(CCA) analysis.

Key words: benthic diatoms, Lake Prespa, ecology

Introduction

Some recent studies have focused on different aspects of the biology of algae inancient lakes throughout the world (e.g. Lake El'Gygytgyn, CHEREPANOVA &BRIGHAM-GRETTE 2001; Lake Tanganyika, COCQUYT 1998; Lake Biwa, GENKAL2003). Algal floras in these environments are characterized by high levels of di-

1864-1318/07/0124-071 $•©2007 E. Schweizerbart'scheVerlagsbuchhandlung, D-70176 Stuttgart

72 Z. LEVKOV et al.

versity and endemism (EDLUND et al. 2003). Concerning diatom communities,taxonomic and biogeographical particularities have been more focused on,while ecological aspects are relatively less known. Within European fresh-waters, one of these ecosystems is Lake Prespa (Macedonia). It belongs to agroup of ancient lakes located in a tectonic valley between Mountains Galicicaand Baba at 853 m a. s. 1. Analyses of short cores from Mikri Prespa (STEVENSON& FLOWER 1991) showed that the eutrophication levels have slightly changed inthe second half of the 20th century. The high abundance of Cyclotella ocellataPANTOCSEK throughout the core suggests that this lake is little affected by in-creased nutrient loadings. Studies on Lake Prespa diatoms confirm the domi-nance of C. ocellata in plankton and benthos (MiTicn & NAUMOVSKI 2000, LEV-KOV 2005). However, few studies on plankton assemblages have been carriedout (KOZAROV 1959, 1960), while investigations on benthic diatoms were ori-ented mainly on taxonomy and distribution (HUSTEDT 1945, LEVKOV et al. 2003,LEVKOV 2005). Former taxonomical studies showed the presence of several rareand endemic taxa (LEVKOV et al. 2006a, b), but data for their ecological prefer-ences are still lacking. This article is the first attempt to determine the ecologicalcharacteristics of the most dominant benthic diatom taxa in Lake Prespa.

Material and methods

1. Study site.

Lake Prespa is located in a tectonic valley between Mountains Galicica andBaba at 853 m a.s.l. The total surface area is 274 km2, and the maximal depth is54.2 m, with a total catchment area of 1095.22 km2 (CHAVKALOVSKI 1997). Itsbottom is mainly covered with organic sediment that enables intensive macro-phyte development during the summer period. There is no natural surface wateroutlet, and large amounts of water are discharged through underground channelsinto Lake Ohrid, under the Galicica Mountains and Suva Planina (ANOVSKJ et al.2001). Waters are calcium-rich and their pH is slightly alkaline.

The dry period that started in 1986, along with the intensive evaporation andusage of lake waters, resulted in a decrease of the water level by 7.8 m comparedto the maximal level (CHAVKALOVSKI 2000). More than half of these losses(57.8 %) were due to natural processes, while the rest was lost through the usefor different human purposes, mainly irrigation and water supplies. According toANOVSKJ et al. (2001), three possible natural factors are usually involved in de-creasing the water level (i) tectonic falling of the lake bottom; (ii) widening ofunderground channels connecting the two lakes and (iii) influence of meteoro-logical parameters. Such a decrease of the water level in the early nineties leadto changes in water quality. According to NAUMOVSKI et al. (1997), the waters ofLake Prespa in that period varied between oligotrophic and mesotrophic, whileSHUMKA (1994) found an oxygen depletion during summer. More recent investi-

Ecology of benthic diatoms from Lake Macro Prespa (Macedonia) 73

Fig 1. Map of the study area showing the 12 sampling sites (black dots) on Lake MacroPrespa.

gations (LEVKOV 2005) showed that Lake Prespa is eutrophic during summer,with blooms of blue-green algae. According to GRUPCE (1997), about half of thephosphorus input in the lake (542.36 tons P2O$ per year) has an anthropogenicorigin. The most important sources of phosphorus in Lake Prespa are untreatedcommunal wastewater and fertilizers used in the region (TRPESKI et al. 2000).

2. Methodology

Water samples from Lake Prespa were collected between June 2002 and May2003 at 12 sampling sites (Fig. 1) located between 50 and 200 m from the shore,depending on bottom topography. Temperature, pH, dissolved oxygen concen-tration, and Secchi depth were measured directly in the field with appropriateequipment. Samples for chemical analyses were conserved in HgCh and trans-

74 Z. LEVKOV et al.

ported in a refrigerator at 4° C. Chemical analyses were performed following theprocedures of APHA (1985), MOORE & CHAPMAN (1986) and FISKE & SUBBAR-ROW (1925). Average values and standard deviation of measured physico-chemi-cal parameters are given in Table 1.

Benthic diatoms were collected with a Van Veen bottom sampler on variousdepths. In most of the cases samples were taken from a depth between 2 m and4 m, except for the pelagial zone where samples from 18m were collected. Priorto fixation with 4% formalin, live samples were observed (LEVKOV et al. 2006b).Diatom slides were prepared by acid digestion (KRAMMER & LANGE-BERTALOT1986) and mounted in Naphrax®. The slides are deposited in the Diatom Collec-tion at the Institute of Biology (DCIBS), Faculty of Natural Sciences, Skopje.Relative abundances were calculated by counting 200 diatom valves (BATE &NEWALL 1998).

Only the 17 diatom taxa that reached > 1 % of relative abundance in thewhole dataset were used in multivariate analyses. Diatom abundances were arc-sine square root transformed and the environmental variables, except pH, werelog-transformed due to their skewed distributions. Differences in diatom abun-dances and physico-chemical variables between samples were studied by meansof ANOVA. Detrended Correspondence Analysis (DCA) was carried out to ex-plore the relationships between diatom taxa and sampling stations and months.Canonical Correspondence Analysis (CCA) was used to relate the diatom as-semblages to environmental factors. All ordinations were run using the com-puter program CANOCO version 4.1 (TER BRAAK & SMILAUER 2002).

Results

A total of 297 diatom taxa were identified in Lake Prespa, and 143 of them hadabundances higher than 1 % in at least one sample. The greatest difference in di-atom composition between the eastern and the western coast was observed in thelittoral zone. The bottom of the west coast (from Stenje village to Perovo vil-lage) was covered with organic sediment. The dominant diatom species Cavi-nula scutelloides (W. SMITH) LANGE-BERTALOT, Navicula rotunda HUSTEDT,N. subrotundata HUSTEDT, Amphora pediculus (KuTZlNG) GRUNOW, and charac-teristic species of the two genera Aneumastus and Sellaphora were frequent inthe benthic communities. Additionally, this part of the lake shore consists of cal-careous rocks (limestone), while the eastern part is mainly formed by silicates.The eastern coast (D. Dupeni village to Pretor) is mostly covered by sand or amixture of sand and organic sediment. In this region, several Navicula sensustricto species are sub-dominant (LEVKOV 2005). It is supposed that the distribu-tion of these species is influenced by the substrate. Few species, so far knownonly for the Lake Prespa, could be found on both sides. Diatom assemblages atlarger depths were dominated by taxa of the C. ocellata complex, as well as byspecies with heavily silicified valves as Diploneis mauleri (BRUN) CLEVE,

Table I . Measured physico-chemical parameters in Lake Prespa. Average values (June-May) ± 1 s.d.

Parameter

pHO2 (mg/L)

1.13Sccchi depth

(cm)NO., (mg/L)N02 (mg/L)NH< (mg/L)N- org. (mg/L)Total N (mg/L)Total P (Mg/L)

SO4 (mg/L)

Na (mg/L)K (mg/L)Ca (mg/L)

Mg (mg/L)Cu (Mg/L)

Fe (Mg/L)

Tl-Stenje

8.36 + 0.429.78+ 1.15

266.25± 110.15

3.32 + 3.780.04 + 0.060.18 + 0.141.66 ±0.951.84 + 1.00

16.49+ 13.0729.48+ 8.04

5.06 ±1.211.20 ±0.44

37.93+ 17.28

6.54 ±3.102.65 ± 0.78

3.53+ 1.4757.51

± 30.57

T2-Oteshevo

8.34 + 0.399.69 + 0.92

259.17± 133.52

2.76 + 2.460.04 + 0.070.17 + 0.112.00+1.052.17 ±1.09

14.65+ 8.4027.37±7.85

4.95 + 1.661.31 ±0.55

37.86+ 17.43

7.77 + 2.342.78 ±1.82

3.98±2.2458.82

+ 32.52

T3-Sirhan

8.33 + 0.559.68 + 1.05

261.25±138.86

2.79 + 2.260.04 + 0.070.22 + 0.111.55 ± 1.211.77 ±1.23

12.05±6.0529.93

+ 14.444.93 ±1.701.13 ±0.57

27.97±15.19

6.27 ± 2.952.49+ 1.10

4.62±3.1548.87

± 19.90

T4-Perovo

8.29 + 0.369.55 + 0.93

284.00+ 140.44

2.68 + 2.370.03 + 0.030.27 + 0.211.74+1.242.01 + 1.31

12.03±9.3126.94+ 8.81

4.87 ±1.521.00 + 0.48

37.19± 17.72

6.12 + 3.233.16 ±1.22

4.61±4.2748.35

+ 26.52

T5-Asamati

8.25 + 0.369.63 + 1.33

308.33± 122.89

4.38 + 5.290.04 + 0.050.25 + 0.141.29 ±1.081.53 ±1.03

15.24±8.7832.86±8.22

5.43 ± 2.331.25 ±0.66

52.27± 14.36

6.56 ±2.322.69 + 0.98

2.72±1.0948.46

± 33.73

T6-Pretor

8.29 + 0.419.81 + 1.16

302.92+ 128.11

3.77 + 3.030.03 + 0.040.23 + 0.161.99 ±1.622.22 ±1.58

16.77± 16.0727.93+ 9.77

5.33 ±0.811.24 ±0.40

39.82±21.79

7.15 + 2.683.19± 1.49

10.05±20.1953.75

+ 40.50

T7-Pelagial

8.35+0.419.72 + 1.10

275.00+ 123.97

3.12 + 2.570.04 + 0.050.16 + 0.091.46 + 0.671.69 + 0.91

11.71±7.9330.94±8.12

5.32 ±0.711.22 + 0.31

36.00+ 19.11

7.52 ±1.952.60+1.02

3.73+ 2.2944.43

±31.09

T8- T9- T10-Konjsko Golem Dolno

Grad Dupeni

8.34 + 0.42 8.36 + 0.44 8.41+0.529.86 + 1.38 10.00 + 1.33 9.77 + 1.24

285.00 291.67 280.42+ 115.55 ±138.90 ±133.27

3.31+2.46 2.89 + 3.18 3.64 + 3.820.03 + 0.04 0.02 + 0.02 0.04 + 0.060.30 + 0.24 0.18 + 0.15 0.22 + 0.161.57 ±1.01 1.37 + 0.89 2.10±1.301.70 + 1.07 1.54 ±0.99 2.14+1.24

9.72 10.89 15.55+ 9.08 ± 9.05 ± 17.6529.44 29.55 34.36+ 8.79 + 8.54 + 14.69

5.19 ±1.22 5.31+0.69 4.89+1.751.18 ±0.19 1.07 + 0.37 1.58 + 1.87

39.09 43.33 40.58±16.48 ±15.75 +18.13

7.43 ±1.92 7.50 ±1.68 7.67 + 2.732.35 + 0.88 2.33 ±0.68 2.62 ±1.02

3.52 3.39 12.58±2.13 ±1.75 ±30.8846.69 43.98 37.23

±33.92 +22.68 ±15.70

Tll-Nakolec

8.35 + 0.559.74+ 1.25

273.50+ 127.24

3.44 + 3.410.03 + 0.040.21+0.141.90 + 1.072.07 + 1.06

9.60±6.0931.07±6.56

5.14 + 0.991.28 ±0.73

37.64± 19.06

6.97 ±2.172.73 + 1.37

14.37±29.5335.14

+ 13.82

T12-Krani

8.32 + 0.4410.01 +

301.83± 136.41

3.34 + 2.690.04 + 0.040.28 + 0.261.88 + 1.192.12+1.28

12.74+ 10.4230.29+ 7.45

5.55 + 0.681.19 ±0.28

36.23±17.15

7.41 ± 1.812.68 ± 0.83

3.73+ 2.6349.19

±38.01

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76 Z. LEVKOV et al.

PNEX

APED

NROT

NSROT ACCB

cscu 12PBAL

11

10

CJUR

GDEC* *COCE *NSUAPSBR

3 NVCAL

.O

NPTR

NPRENKRS* i

Fig. 2. DCA ordination biplot between relative abundance of 17 diatom taxa and12 sampling sites.

Campylodiscus noricus EHRENBERG, Cymatopleura elliptica (BREBISSON)W. SMITH and Navicula hastata JURILJ.

DCA ordination biplots show the distribution of the main diatom taxa accord-ing to their different relative abundances between sampling stations (Fig. 2) andmonths (Fig. 3). No general trend can be inferred from the species/stationsgraphic (Fig. 2). ANOVA analysis showed no significant differences betweenthe values of the physico-chemical variables measured in the different samplingstations (F = 0.87, p = 0.88); however, significant differences were found in di-atom abundances for 14 out of 17 taxa analyzed, thus suggesting the presence ofan additional, unmeasured variable responsible for such differences. A trend to-wards seasonal distribution of points can be found in the species/months biplot(Fig. 3). Species such as Nitzschia subacicularis HUSTEDT, Cyclotella sp. 1 orDiploneis mauleri seem to be associated to winter-spring months, while Navi-cula rotunda, N. subrotundata and Pseudostaurosira brevistriata (GRUNOW)D. M. WILLIAMS et ROUND are plotted associated with summer samples (June,July).

Statistically significant differences were found between the abundances ofeight diatom taxa and 14 physico-chemical variables regarding month of sam-pling CCA biplot (Fig. 4) shows graphically the relationships between diatomassemblages and environmental factors. The eigenvalues of the first two axes

Ecology of benthic diatoms from Lake Macro Prespa (Macedonia) 77

May

DMAU•

NSUA«CJUR Dec

« OMar

OFeb

NVCAL

NPRE

GDEC

NPTR*Oct

PBALPNEX

! CSCU

COCE

NKR?

NovAug

Sep

ACCB.

NROT

NSROTJul

Jun

PSBR

•APED

Fig. 3. DCA ordination biplot between relative abundance of 17 diatom taxa and12 months (from June 2002 to May 2003).

are 0.046 and 0.022, explaining only 6.1 % and 3.0 % of the cumulative varianceof the species dataset, respectively. The sum of all canonical eigenvalues was0.131; however, Monte Carlo permutation tests of significance for the first andalso for all canonical axes (199 unrestricted permutations) were significant(p<0.05). The diatom-environment correlations for CCA axes 1 (0.550) and 2(0.484) were also significant, indicating a relatively strong relation between di-atoms and the measured environmental variables.

According to the CCA results (Fig. 4), physico-chemical variables were themain factors controlling diatom ecology in Lake Prespa. The main variables in-fluencing species distribution and abundances were ammonium and metalliccations (Cu, Mn, K); the secondary variables were, in turn, dissolved oxygen andSecchi depth. Strong colinearity was found within some of the variable sets (e.g.Cu-K-Mn, Mg-SCvC^). The concentration of Cu was significantly correlated tothe relative abundance of 10 out of 17 diatom taxa analyzed, and also affectedspecies diversity (Shannon's index, Pearson's R = 0.2, p = 0.01). Except for NFLtconcentration, variables related to water trophic status ([P], [N], [Norg]) seem tohave a negligible effect on benthic diatom abundances in Prespa Lake. Phospho-rus concentration was only correlated negatively to the abundance of Nitzschiasubacicularis (Pearson's R = 0.2, p = 0.02). The minimal environmental variableset explaining significantly (p <0.05) the variance in the diatom data was identi-fied using the forward-selection option of CCA. Four variables were extracted:concentrations of NH4 (p = 0.005), Fe (p = 0.04), O2 (p = 0.04) and Cu (p = 0.05).

78 Z. LEVKOV et al.

Fig. 4. CCA biplot. Relationships between diatom assemblages and environmental fac-tors.

Discussion

Benthic communities in the Lake Prespa were characterized by a high diversity,which is in accordance with other studies carried out in ancient lakes (MEISTER1913, SKVORTZOW 1936, HUSTEDT 1945, JURILJ 1954, COCQUYT 1998). The di-versity is generally higher in littoral than in sublittoral or deep zones of theselakes, presumably due to higher ecological diversity in shallow zones (MARTENS1997).

One of the most abundant species in bottom samples of Lake Prespa is Cy-dotella ocellata. It was observed in almost all samples from different depths(0.5-18 m). Observations of live material show that the cells even at largerdepths still possess plastids (typical discoid plastids in large number). Similarfindings were recorded by JURILJ (1954) for C.fottii HUSTEDT, which is the dom-inant diatom species in the plankton of Lake Ohrid. According to JURILJ (1954),C. fottii was still capable of photosynthesis at the depth of 40-50 m, where thelight intensity was lower than 1 %.

Another important feature is that in our samples, the population of Cyclotellaocellata was characterized by large-sized vegetative cells, with diameters of

Ecology of benthic diatoms from Lake Macro Prespa (Macedonia) 79

Table 2. Correlation matrix between main benthic diatom species abundances and se-lected chemical variables in Lake Prespa. Pearson's R values shown, p-values in italics.Significant correlations (p < 0.05) in bold. Ha = Shannon's diversity a.

ACCB

APED

CSCU

CJUR

COCE

DMAU

GDEC

NKRS

NPTR

NPRE

NROT

NSROT

NVCAL

NSUA

PBAL

PNEX

PSBR

Ha

[TP]

0,070,410,100,23

-0,010,890,020,81

-0,050,58

-0,020,79

-0,050,550,040,620,080,37-0,140,77

-0,080,330,110,79-0,020,83-0,200,020,000,97

-0,070,42

-0,020,810,000,95

[TN]

-0,060,460,110,20

-0,080,32-0,090,520,080,36

-0,020,84

-0,030,750,070,440,090,270,130,720,040,660,170,050,050,59

-0,210,010,210,010,160,060,160,050,160,06

[K]

0,080,330,200,02-0,030,74

-0,210,01

-0,130,72

-0,190,030,090,270,030,72

-0,010,94

-0,020,78-0,020,550,090,290,080,52-0,230,010,100,240,220,010,130,140,090,28

[Cu]

0,150,070,190,020,140,09

-0,190,03

-0,200,02

-0,200,020,120,770,070,450,170,050,050,560,110,180,210,010,120,76-0,280,000,250,000,200,020,200,020,210,01

Secchi depth

-0,040,67

-0,010,57

-0,060,470,040,670,050,560,130,72-0,110,20

-0,090,50

-0,140,09

-0,140,09

-0,060,47

-0,100,25

-0,080,550,220,01-0,220,01-0,250,00

-0,070,40-0,150,05

6-36 urn. These cells have a morphology and ul(restructure similar to other pop-ulations, except for a larger valve size. Similar valve sizes in C. ocellata wereobserved in Hovsgol, Mongolia (EDLUND et al. 2003). According to EDLUND &STOERMER (1991) species with larger valve sizes can be found in oligotrophicconditions, compared to those in waters under anthropogenic influence. Thiscould be a result of several main factors such as (i) oligotrophy of these lakes;

80 2. LEVKOV et al.

(ii) larger gametangial and initial cell cardinal point size and (iii) evolutionaryprocesses (EDLUND et al. 2003). Thus, species with smaller valve sizes could bethe result of increased nutrient concentration in lakes, because they are morecompetitive in using nutrients (STOERMER et al. 1989).

Despite the recent anthropogenic introduction of large amounts of phospho-rus in the Lake Prespa, this element seems to be stabilized in the bottom sedi-ments, since the water remained oligotrophic throughout the present study(maximal concentration: 65.3 ug.H). This situation contrasts with the eu-trophic conditions observed in former years (LEVKOV, obs. pers.). For that rea-son, phosphorus does not seem to have affected substantially the abundances ofthe studied diatom taxa. Meanwhile, statistical analyses showed that the fre-quency of several species correlated significantly with the concentrations ofNH4 and Cu. Ammonium and copper are known to be main toxicants for fresh-water diatoms (STEEMANN NIELSEN & WIUM-ANDERSEN 1971, HURLIMANN &SCHANZ 1993), but their range of tolerance is very wide (RuGGiu et al. 1998) andthe concentrations found in our survey (maximal concentrations: 0.9 and8.25 ug.H respectively) did not reach the critical values reported in the litera-ture. Hence, diatom species in the present study seem to have increased or de-creased in relative abundance according to their respective autoecological op-tima regarding these pollutants. SNYDER et al. (2002) found that relatively highconcentrations of ammonium are related to an increased diatom diversity, as itwas found in the present work (Table 2).

In conclusion, the pattern of high diatom diversity generally reported for an-cient lakes is also true in Lake Prespa. Our results support the hypothesis thatchemical variables are the main factors controlling the composition of the ben-thic diatom communities in this ecosystem. Additionally, it can be said that, un-der low trophic conditions, other parameters, such as the low concentrations ofpotential pollutants, can be responsible for the differential abundances of diatomtaxa. Further studies will help in determining the causes of the dissimilaritiesfound between sampling stations.

Acknowledgements

Authors are grateful to A. Oliveira for her assistance in English improvements.

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Manuscript received May 19, 2006, accepted February 6, 2007.

Authors' addresses:ZLATKO LEVKLOV,SVETISLAV KRSTIC,TEOFIL NAKOVInstitute of Biology,Faculty of Natural Sciences,Gazi Baba bb.,1000 Skopje,Republic of MacedoniaE-mail: zlevkov@iunona.pmf.ukim.edu.mkSaul Blanco,Area de Ecologia,Universidad de Leon,E-24071 Leon,Spain.Saul Blanco,Luc Ector,Public Research Center- Gabriel LippmannDepartment Environment and Agro-biotechnologies (EVA),41 rue du Brill,L-4422 Belvaux,Grand-Duchy of Luxembourg

Ecology of benthic diatoms from Lake Macro Prespa (Macedonia) 83

List of acronymsACCB - Achnanthes devei var. balcanica HUSTEDTAPED - Amphora pediculus (KOTZINO) GRUNOWCSCU - Cavinula scutelloides (W. SMITH) LANGE-BERTALOTCJUR - Cyclotella sp. 1.COCE - Cyclotella ocellata PANTOCSEKDMAU - Diploneis mauled (BRUN) CLEVEGDEC - Geissleria decussis (0STRUP) LANGE-BERTALOT ET METZELTINNKRS- Navicula krsticii LEVKOVNPTR - Navicula petwvskae LEVKOV et KRSTICNPRE - Navicula prespanensis LEVKOV et METZELTINNROT - Navicula rotunda HUSTEDTNSROT - Navicula subwtundata HUSTEDTNVCAL - Navicula viridulacalcis LANGE-BERTALOTNSUA - Nitzschia subacicularis HUSTEDTPB AL - Placoneis balcanica (HUSTEDT) LANGE-BERTALOT, METZELTIN et LEVKOVPNEX - Placoneis neoexigua LANGE-BERTALOT et MIHOPSBR - Pseudostaurosira brevistriata (GRUNOW) D.M. WILLIAMS et ROUND