Evidence for coincidence of meiofauna spatial heterogeneity with eutrophication processes in a shallow-water mediterranean bay

Estuarine, Coastal and Shelf Science (1992) 35, 1-16

E v i d e n c e for C o i n c i d e n c e o f M e i o f a u n a Spatial Heterogeneity with Eutrophication P r o c e s s e s in a S h a l l o w - W a t e r Mediterranean bay

C r u z P a l a c i n a, J o s e p - M a r i a

Gill ~ and Daniel Martin b

°Instituto de Ciencias del Mar ( C S I C ) , Paseo Nacional s/n, 08039 Barcelona, Spain and bCentro de Estudios Avanzados de Blanes ( C S I C ) , Cami de Santa Bdrbara, 17300 Blanes, Spain Received 20 May 1991 and in revised form 12 November 1991

Keywords: nematoda; meiobenthos; eutrophication; population; density and variations; Mediterranean Coast Substantial influxes of continental runoff from rice paddies flow into Alfacs Bay in the Ebro River delta (Western Mediterranean) at the beginning of summer. The runoff carries with it considerable amounts of silt and organic matter, which are deposited initially in the northern part of the bay. The eutrophication process studied in July 1987 coincided with high spatial heterogeneity of meiofaunal populations in the bay. The level of differentiation of nematode assemblages in the area over a distance of only 5 km was similar to that found in much larger coastal areas. In addition, the eutrophication processes in the bay appeared to cause high meiofaunal concentrations, in particular of nematodes, which, as consumers of benthic diatoms and bacteria, play a major role in the turnover of a large portion of the energy generated.

Introduction Recent geological changes in the Western Mediterranean have given rise to important alterations in coastal circulation and in the general pattern of the coastline, with the formation of two large deltas at the mouths of the Rhone and Ebro Rivers and a series of coastal brackish-water lakes and lagoons. These areas receive the major inflow of river runoff, and hence act as systems for exchange between the land and the sea. Terrestrial runoff represents one of the most important eutrophication processes in the Mediterranean. Such areas as the bays associated with the large deltas are, owing to eutrophication processes, among the few productive locations in a sea that has traditionally been regarded as oligotrophic in macroscopic terms (Margalef, 1985). This high level of productivity has resulted in a level of exploitation by man such that both the time and the intensity of the influx of river water into the bays are now regulated. T h e initial effect of the anthropogenic factor on benthic populations has been to bring about changes in species composition and density and a higher degree of heterogeneity (Gray, 1991). Coastal bays like those associated with the Ebro River delta (along the northeastern coast of the Iberian Peninsula) are markedly marine in nature, given the small tides in the 0272-7714/92/070001 + 16 $03.00/0

© 1992AcademicPress Limited

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Mediterranean Sea. In addition, the pattern of rainfall in this marine region causes the outflow of inland waters to take place at definite times of year, namely, late spring and early summer, or mid-autumn. M u c h of the river water from the terrestrial runoff is diverted into extensive rice-growing regions before it is allowed to flow out into the bay. When the outflows do occur, they tend to be of short duration and high intensity, and they give rise to large-scale eutrophication processes that affect the benthic populations inhabiting the bays (Pratet al., 1988; Mallo et al., submitted). T h e benthos in these areas is dominated by macro- and meiofauna that dwell on or in the surface layers of sediment. T h e terrestrial runoff transports large amounts of organic matter and thereby heightens environmental stress. Warwick (1988) pointed out that in such situations the meiofauna responds more successfully than the macrofauna to changes in environmental conditions brought about by the action of man. Nematodes are the most abundant meiofaunal organisms in shallow waters like those of coastal bays (McIntyre, 1969). Unlike coastal lagoons, bays and sheltered areas have been the focus of little attention in the Mediterranean, especially with regard to the impact of eutrophication processes on benthic populations. Some workers have discussed the spatial distribution patterns of the meiobenthos in these bays and have noted that it is, broadly speaking, determined by sediment composition and by the degree of exchange and mixing of sea water in the bays with the inflow of fresh water from rivers (e.g. Friglos & Zenetos, 1988; Nicolaidou & Papadopoulou, 1989; Palacin et al., 1991). T h e present study examined the effects of large influxes of river water as carriers of substantial amounts of anthropogenic materials associated with eutrophication processes on the meiofaunal populations, specifically nematodes, in a coastal bay in the Ebro River delta (Figure 1). Terrestrial runoff in the area occurs after the spring rains and contains large quantities of organic matter picked up as the water flows through rice paddies before entering the bay. T h e working hypothesis was that the influence of the river runoff on the nematode populations was so important that it gave rise, in a small area, to a level of spatial heterogeneity comparable to those observable in m u c h larger coastal areas.

Material and m e t h o d s This study was carried out in Alfacs Bay, which is located in the Ebro River delta (Western Mediterranean 40°33'-40°38'N, 0°32'-0°44'E). Sampling was carried out during July 1987 at a total of 23 stations that covered the entire bay, which has a m a x i m u m depth of 6 m (Figure 1). T e m p e r a t u r e and salinity were measured using a calibrated sensor M a r k X (Master Instruments) on the surface of the sediment, after which core samples were taken immediately. T h e meiofaunal samples consisted of cores 12.5 cm 2 in diameter extracted from the bottom sediment to a depth of 8 cm, and the organisms present were removed from the sediment in a Boisseau elutriator (Boisseau, 1957) by filtration through a 55 p m mesh. T h e nematodes separated from each sample were dehydrated and m o u n t e d in glycerine for microscopic examination. Additional cores were taken at each station for measurement of physical and biological parameters. T o calculate the percentage of organic matter present, samples were heated at 60 °C for 24 h and then calcined in an oven at 500 °C for 3 h, following Greiser and Faubel (1988). T h e total bacterial count was obtained by analysing two separate fractions: counts of heterotrophic bacteria were made on petri plates of marine broth ( D I F C O 0791-01); counts of denitrifying bacteria were effected in test tubes according to the method of

Coincidence of meiofauna spatial heterogeneity with eutrophication processes

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Tietjen (1982). T h e redox potential was measured directly in field at the sediment surface using an Orion Research model S500C-ORP platinum electrode. Granulometric analysis was carried out by first treating the core samples with 20% H202 to eliminate the organic matter and then analysing the fines fraction (~<50 pm) in a Sedigraph model 5000D particle size analyser (Gir6 & Maldonado, 1985). Statistical analysis was based on cluster analysis using Czekanovski metrics and the U P G M A aggregation algorithm with the aid of an analysis package developed by D r J. Lleonart of the Instituto de Ciencias del Mar in Barcelona. Nematode biomass was estimated by extrapolation using the formula for calculating nematode body size published by

4

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Andrassy (1956); specific weight was taken as 1.3 and the ratio of wet weight to dry weight 0-3, both values from Wieser (1960).

Results

During the s u m m e r the channels that flow into the bay are opened, allowing terrestrial runoff to flow into the bay, particularly along the north shore. As might be expected, salinity values were lower in the vicinity of the channel mouths (Figure 2). In the rest of the bay, salinity values attained levels similar to marine values, because of the intrusion of a wedge of sea water into the centre of the bay. T h u s , strong salinity gradients, also due in part to high s u m m e r evaporation rates, were recorded along the northern platform of the bay (see also C a m p & Delgado, 1987). Heating of the surfacemost water layer caused temperatures to be higher along the shore and over the platform than in the central basin, where temperature values were similar to those in the sea outside the bay (Figure 2). T h e proportion of fine particles in the sediment was related to the salinity pattern (Figure 2). T h e terrestrial runoffalong the north shore gave rise to a high proportion of silt and clay in that area, though the highest values were recorded in the central basin, where the silt settles. In contrast, the proportion of fines was very low along the south shore, which had basically sandy bottoms (Figure 2). T h e trends in the spatial distribution of organic matter and redox potential followed the same pattern as that described above for the proportion of fines. T h e highest proportion of organic matter and lowest redox potential of sediment were recorded along the north shore, where terrestrial runoffflowed into the bay. On the clean sandy bottoms along the south-southeast shore, the surface sediments are not reduced and little organic matter is present (Figure 2). T h e highest bacterial concentrations occurred directly opposite the mouths of the channels, attaining values greater than 150 x 106 cells per g-1 of sediment at certain stations. In contrast, the concentration values along the south-southeast shore were often 100 times smaller (Figure 2). Cluster analysis pointed up the assemblages of stations that shared more or less c o m m o n environmental features (Gray & Pearson, 1982). T h e analysis defined two assemblages on the basis of environmental parameter values. One grouped all the stations affected by terrestrial runoff, where eutrophication processes were detected in the bay (Figure 3). T h e other assemblage consisted of nearly all the stations off the south-southeast shore, more marine-like in nature and for the most part unaffected by eutrophication processes. T h e former assemblage included a subassemblage composed of the stations in the central basin, where silt deposits from the terrestrial runoff accumulate and where the highest values were recorded for certain environmental parameters (Table 1). T h e highest density values for meiofaunal organisms were found off the southsoutheast shore of the bay, the lowest density values in the central basin and off the northwest shore near the channel mouths (Figure 4). Mean density was 704.1 individuals per 10 cm 2, with a m a x i m u m density of 1628.8 individuals per 10 cm 2 and a m i n i m u m density of 129.6 individuals per 10 cm 2. T h e pattern of nematode distribution was the same as that exhibited by the meiofauna as a whole, since nematodes accounted for over 75% (in number) ofmeiofaunal individuals throughout the bay. Mean nematode density was 403.5 individuals per 10 cm 2, with a m a x i m u m density of 1003.2 individuals per 10 cm 2 and a m i n i m u m density of 32 individuals per 10 cm z.

Coincidence of meiofauna spatial heterogeneity with eutrophication processes

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In all, 115 nematode species were collected (see Appendix). T h e most abundant species throughout the bay included Sabatieria pulchra, Richtersia vincxae, Paracanthonchus mediterraneus, and Spirinia parasitifera. Species diversity was higher off the southsoutheast shores than offthe north shore and in the rest of the bay (Figure 4). On the other hand, nematode biomass was rather higher off the north shore than off the south shore of the bay and was highest towards the northeast, at stations affected wholly or partially by terrestrial runoff, where the species, like Metoncholaimus albidus, presented large individual sizes. Cluster analysis performed on the nematode species pointed up the existence of three assemblages of stations that followed a pattern very similar to that for the assemblages based on environmental factors (Figure 5): a north-shore assemblage in which nematode density and biomass were highest; a south-shore assemblage with a high n u m b e r of species but lower biomass; and a third assemblage in the basin or centre of the bay characterized by both low density and low biomass. T a b l e 2 sets out the characteristic species in each of these assemblages. Species belonging to the Families Comesomatidae, Linhomoeidae, Xyalidae, and, to a lesser extent, Desmodoridae dominated in the assemblage off the north shore, where the bottom was sandy mud. Epigrowth feeders were the most representative feeding group, though non-selective deposit feeders were also common. Desmodoridae, Selachinematidae, and Chromadoridae predominated in the assemblage off the south shore, where the bottom was basically sandy. While epigrowth feeders were also abundant in this assemblage, numerous representatives of omnivorous predators and non-selective deposit feeders were also present. Lastly, Comesomatidae, Xyalidae, and Axonolaimidae were dominant in the assemblage of stations located in the basin, where the bottom sediment was muddy. Epigrowth feeders were the predominant feeding group, though selective deposit feeders were also well-represented. Figure 6 graphically illustrates the most salient characteristics of the species in each of these three assemblages.

Discussion T h e spatial distribution pattern of environmental factors in the bay delimited a n o r t h south zonation pattern aligned with the runoffinputs. T h e same pattern was observable in the nematode assemblages, in which a further group of species associated with the central basin was also distinguishable. Although the bottom sediment in the central portion of the bay is rather m u d d y , it is unlikely that the sedimentation processes are the result of recent inputs from runoff. T h e y are probably the result of a more gradual settling carried on over a longer period. In fact, all the stations in the basin exhibited a high proportion of silt and clay, whereas the distribution of these same materials was m u c h more irregular off the north shore. Environmental conditions such as hydrodynamics and salinity presumably were most stable in the central basin, where nematode populations were dominated by species belonging to the Family Comesomatidae, which are c o m m o n on the infralittoral m u d d y bottoms of the Mediterranean (Boucher, 1972). Most of the species in this zone were small in size, and while epigrowth feeders were most prevalent, large numbers of non-selective deposit feeders were also present. In fact, the situation observed in the central basin of Alfacs Bay is reminiscent of an intermediate situation in an estuary. For instance, Warwick and Gee (1984) described the middle zone of the T a m a r estuary in southwestern

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Figure 3. Cluster analysis based on environmental variables and location of the resulting assemblages in the bay.

TABLE 1. Minimum and maximum values for environmental factors in each of the assemblages identified by cluster analysis North + Central % silt and clay % organic matter Redox potential Temperature Salinity Depth

4/94-23 0.73/7.37 - 73.4/- 290.5 23/29 '3 20/36 0.50/6

Central 65-01/94.23 0.73/7.37 - 73.4/- 280.5 23/27.2 20/36 0.50/6

South 0-01/2.5 0.57/0.89 16.5/- 200 23/29-5 29/37 0-50/3

England as the site populated by a climax community that had its origin in the more stable environmental conditions prevailing there. T h e north shore of Alfacs Bay presents high environmental instability in the sense described by Warwick and Gee (1984) for an estuary, caused by the influx of river water. In the summer, the time of year when this study was carried out, runoff was abundant and brought with it large deposits of organic matter and nutrients f r o m nearby rice paddies. T h e result of the ensuing eutrophication process was similar to the situation observed in the u p p e r portion of an estuary, with lower diversity but increased nematode biomass owing to dense populations of certain large opportunistic species like M . albidus. In fact, according to van D a m e et al. (1980) for the Western Scheldt estuary in Holland, a sharp decrease in diversity and a proliferation of opportunistic species is indicative of marked changes in salinity. Where sediments are m o r e evenly distributed, species aggregation is patchier, a distribution pattern typical of environments rich in microhabitats as a result of high environmental instability (Wieser, 1960). In any event, this part of the bay, covered by reduced, m u d d y sediments, is populated by a nematode c o m m u n i t y very similar to those found on shallow-water bottoms elsewhere in the Mediterranean (Boucher, 1972). T h e presence of such species as T. longicaudata, S. parasitifera, and P. mediterraneus would seem to indicate such a similarity between the bottoms despite the particular large-scale anthropogenic alterations in this section of the bay.

Coincidence of meiofauna spatial heterogeneity with eutrophication processes

9

6

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Figure 4. Distribution of meiofaunal and nematode densities (number of individuals 10 c m -2) in the sediment (top 8 cm), nematode biomass (l~g dry weight 10 cm 2), and nematode diversity (Shannon-Wiener index) in Alfacs Bay.

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Figure 5. Cluster analysis based on nematode species and location of the three resulting assemblages in the bay.

O f f the south shore o f Alfacs Bay, which is located outside the major influence o f the continental r u n o f f o n the n o r t h shore, the b o t t o m s consist o f sandy sediments inhabited by a n e m a t o d e c o m m u n i t y typical o f fine sand, with high diversity and very few d o m i n a n t species (Tietjen, 1977). T h e larger n u m b e r o f species and broader size s p e c t r u m were analogous to the situation in the m o r e m a r i n e e n v i r o n m e n t o f an estuary (Warwick and Gee, 1984). F u r t h e r m o r e , the presence o f certain species, particularly those of the genus

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TABLE2, Characteristic nematode species in each of the nematode assemblages identified by cluster analysis, giving the frequencyand mean number of individuals per 10 cm2

Species N1 Sabatieria pulchra Paracomesoma dubium Spirina pa rasitifera Terschellingia longicaudata Stylotheristus mutilus Metoncholaimus albidus Paracomesoma longispiculum Paracanthonchus mediterraneus N2 Dorylaimopsis mediterranea Paracomesoma longispiculum Sabatieria praedatrix Paramonohystera pilosa Parodontophora quadristicha N3 Richtersia vincxae Paracanthonchus mediterraneus Chromaspirina chabaudi Nannolaimoides decoratus Chromaspirina papilllcaudata Pomponerna complexa Desmodora ovigera Spirinia parasitifera

Mean number of individuals

Frequency (°o)

70.0 59.0 42-7 25.6 22-6 17.1 15.1 14.8

85.7 85.7 71.4 100.0 42.8 28.5 28,5 42"8

14.8 11-0 8"3 3.8 2.5

100.0 33.3 66"6 66.6 83.3

56.4 45"5 29.4 23-0 22.1 20-6 16.7 14.8

77.7 88"8 77.7 88.8 77.7 33.3 44,4 88.8

Richtesia and others of the genera Chromaspirina, Desmodora, and Spirinia, makes the bottoms in this part of the bay comparable to the fine sandy bottoms both at the mouths of estuaries and on the continental shelf (Ward, 1973). This is not an area of high environmental instability, since it is relatively unaffected by hydrodynamic processes, as is confirmed by the absence of species of the Families Dracomatidae and Epsilonematidae (Williems et at., 1982). T h e presence of numerous species with striated cuticles, and of a variety of feeding groups including non-selective deposit feeders and omnivorous predators in addition to epigrowth feeders is a reflection of the type of habitat in this part of the bay. An important feature of this kind of habitat is a level of environmental stability that makes it possible for more conservative populations to develop. T h e presence of apparently endemic (only known from this area) species in such communities (Heip et al., 1985), which in the case of Alfacs Bay came to somewhat more than 10% of the total number of species in the hay (Palacin, 1990), is one example of this. T h e spatial distribution of nematode species and families and the patterns of species diversity and feeding types in relation to environmental features was typical of those in marine habitats (Heip et al., 1985). However, the zonation and spatial heterogeneity, brought about by the input of continental runoff, and observed at small scale in this bay was no more than 5 krn wide and comparable to the patterns observed on a larger scale in different coastal areas, e.g., Catalonia (Western Mediterranean) (Ros et al., 1990), the N e w York Bight (Tietjen, 1980), and Northumberland (Warwick & Buchanan, 1970). M u d d y bottoms in sheltered areas like Alfacs Bay are rich in meiofauna and, in particular, are home to dense populations of nematodes (e.g. van D a m m e et al., 1980).

Coincidence of meiofauna spatial heterogeneity with eutrophication processes

11

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Figure 6. Graphicrepresentationof the most characteristicspeciesin eachof the three nematode assemblages in Alfacs Bay. S.p. Sabatieria pulchra; P.m. Paracanthonchus mediterraneus; S.pa. Spirina parasitifera; T.1. Terschellingia longicaudata; S.m. Styloteristus mutilus; M.a. Metoncholaimus al&'dus; P.1. Paracomesoma tongispiculum; P.d. Paracomesoma dubium; D.m. Dorylaimopsis mediterranea; S.pr. Sabatieria praedatrix; P.p. Paramonohystera pilosa; P.q. Parodontophora quadristicha; R.v. Richtersia vincxae; C.ch. Ghromaspirina chabandi; N.d. Nannolaimoides decoratus; C.p. Chromaspirina papillosa; P.c. Pomponema complexa; D.C.o. Desmodora ( Croconema) ovigera.

Nematode densities recorded in the bay were in fact rather higher than those in many other coastal areas (Heip et al., 1985). T h e densities in the northern part of the bay were strongly affected by the changes generated by the continental runoff. Species diversity in the northern section of the bay was also altered, yet biomass was unaffected, because of the development of monospecific populations of large species. This phenomenon constitutes evidence of the capacity of nematodes to respond to changes taking place in the bottom sediment as a consequence of anthropogenically induced perturbations, a sensitivity many times higher than that of other components of the meiofauna (Herman et al., 1985). Unlike the meiofauna, macrofaunal biomass were substantially low in the northern part of the bay during July 1989 (Palacin et al., 1991; Martin, 1991). Survival of the macrofauna in the face of perturbations in the environment has generally been reported to be much lower than that of the meiofauna (e.g., Whitlatch, 1980; Warwick et al., 1990). It follows that meiofaunal biomass values are not good indicators of environmental perturbations and that the scope of the changes taking place in a benthic community will instead be reflected by the species composition of such meiofaunal communities and by differences among the various assemblages. Organic enrichment is a well-known cause of changes in the species composition of benthic communities (Gray et al., 1990). Moreover, such changes in community composition are a direct effect of eutrophication (Gray, 1991), which is also manifested by increased density and biomass values for populations of certain species, particularly opportunistic species.

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An interesting feature associated with nematode density in Alfacs Bay was that increased abundance was related to a decrease in the density of benthic diatoms (Delgado, 1989) and bacteria (Mallo, 1989) in the area, particularly in the northern part of the bay. Nematodes, especially epigrowth feeders, are consumers of diatoms and bacteria, and nematode density increases with the availability of these organisms (Admiraal et al., 1983). T h u s , the diatom densities recorded in the area in June by Delgado (1989), which were m u c h lower than would otherwise be expected in the light of the eutrophication processes taking place in the bay at the beginning of summer, may have been the result of predation by the meiofauna, and by nematodes in particular. A major share of the energy generated directly by the eutrophication process may in this way be processed by the meiofauna. T h i s would be in consonance with the biological model put forward by Officer et al. (1982) in connection with the impact of benthic filter feeders on the community in San Francisco Bay. Filter feeders process a major proportion of the energy generated by the normal eutrophication processes in San Francisco Bay. T h u s , as in the discussion of coastal areas of land-sea exchange published by Margalef (1985), Alfacs Bay may act as a buffer system between the inland water and marine systems thanks to the action of organisms like those making up the meiofauna, which may retain a large share of the energy inputs into the system from continental runoff. In conclusion, the eutrophication process brought about by substantial continental runoffflowing into Alfacs Bay at the beginning of s u m m e r took place at the same time as a high level of spatial heterogeneity was detected in the meiofauna inhabiting the bay. This high heterogeneity was reflected by the existence, on a small scale (bay of only 5 km wide), of three separate assemblages similar to those observable in m u c h larger coastal areas. T h e northern section of the bay was most affected by the influx of inland waters, which gave rise to a community with low diversity but high biomass levels. In contrast, the southern section of the bay was hardly affected and presented a community like those typical on fine sandy coastal bottoms. Finally, the central basin was populated by a mature community adapted to the prevailing conditions of gradual but ongoing sedimentation. Despite the fact that there is no evidence of spatial distribution ofmeiofauna before the period studied herein, we hypothesize that this unusual meiofaunal heterogeneity pattern is closely related with eutrophication processes which occur during s u m m e r in this bay.

Acknowledgements T h i s work was supported by C I C Y T grant, contract n u m b e r A C 16.84.

References Admiraal, W., Bouwman, L. A., Hoekstra, L. & Romeyn, K. 1983 Qualitative and quantitative interactions between microphytobenthos and hervivorous meiofauna on a brackish intertidal mudflat. Internationale Revue der gesamten Hydrobiologie 68, 175-191: Andrassy, I. 1956Die Rauminhalts mad Gewichtbestimmung der Fadenwurmer (Nematoda). Acta Zoologica Academia Sciemiarum Hungarica 2, 1-15. Boisseau, J. P. 1957 Technique pour l'&tudequantitative de la faune interstitielle des sables. Comptes rendus de la Societd des saves de Paris, Section Sdences 117-119. Boucher, G. 1972 Distribution quantitative et qualitative des N~matodes d'une station de vase c6ti6re de Banyuls-sur-Mer. Gahiers de Biologie Marine 13, 457-474. Camp, J. & Delgado, M. 1987 Hidrografia de las bahias del Delta del Ebro. Investigaci6n pesquera 51, 351-369. Delgado, M. 1989 Abundance and distribution of microphytobenthos in the bays of Ebro Delta (Spain). Estuarine, Coastal and Shelf Science 29, 183-194.

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C. Palacin et al.

14

Warwick, R. M., Plat't, H. M., Clarke, K. R., Agard, J. & Gobin, J. 1990 Analysis of macrobenthic and meiobenthic community structure in relation to pollution and disturbance in Hamilton, Bermuda. Journal of Experimental Marine Biology and Ecology 138, 119-142. Whitlatch, R. B. 1980 Patterns of resource of utilization and coexistence in marine intertidal deposit-feeding communities. Journal of Marine Research 38, 743-765. Wieser, W. 1960 Benthic studies in Buzzards Bay. II. The meiofauna. Limnology and Oceanography 5, 121-137. Williems, K. A., Vincx, M., Cleaeys, D., Vanosmael, C. & Heip, C. 1982 Meiogbenthos of a sublittoral sandbank in the southern bight of the North Sea. Journal of the Marine Biological Association of United Kingdom 62, 535-548. APPENDIX 1. Species listing indicating the density (10 cm 2) of each species in each of the three assemblages, namely, northern (N1), central (N2) and southern (N3) N1

N2

N3

0

0

4'27

2-74 0 0"46

0 0 0

0 0'18 0'71

0.23 0.23

0 0

0,18 4.09

0.23 0 0 0-23 3"66 0

0 0 0-27 0 0 0-27

0'36 1"07 0 0"36 0 0

27-66 0 0 0.91 0'23 15"01 0 0

0 0 0 0 1 '60 1"87 0 0

0 0'89 0"36 1"78 0 9"78 1'42 0'53

Eurystomina sp. 1 Eurystomina sp. 2 Pareurystomina acaminata (De Man 1889) Gerlach 1952 Pareurystomina sp. 1 Pareurystomina sp. 2 Symplocostoma sp.

0-23 0 0 0 0"46 0

0 0 0-80 0 0 0

0 0'36 0 0"18 0 0"18

Family Rhabdodemaniidae Rhabdodemania gracilis (Diflevsen 1918)

0

1"87

0

2'29

0

1-83

0

2'31 0"01 3'56 0"18 0"36 0 9"42 1"24

Order Enoplia Family Thoracostomopsidae

Mesacanthion macrospiculum Palacin 1990 Family Anticomidae

Anticoma acuminata (Eberth 1863) Bastian 1965 Anticoma litoris Chitwood 1936 Anticomopsis longicaudata (Chitwood 1951)Wieser 1953 Family Ironidae

Thalassironus britannicus De Man 1889 Thalassironus sp. Family Oxystominidae

Halalaimus ( Halalaimus) cirrhatus Gerlach 1953 Halalaimus ( Nualaimus ) papillifer Gerlach 1956 Halalaimis ( Halalaimus ) sp. Oxystomina sp. Wieseria sp. Oxystominidae n. i. Family Oncholaimidae

Metoncholaimus albidus (Bastian 1865) Filipjev 1918 Oncholaimellus mediterraneus (S.-Steldaoven 1942) Oncholaimellus sp. Oncholaimus campylocercoides De Coninck & S.-Stekhoven 1942 Prooncholaimus megastoma (Eberth 1863) Micoletzky 1924 Viscosia cob&"Filipjev 1918 Viscosiafiliforrnis (Kreis 1934) Viscosia sp. Family Enchelidiidae

Order Chromadorida Family Chromadoridea

Chromadorella problematica Boucher 1976 Chromadorina germanica (Butschli 1974) Wieser 1954 Chromadorina metulata Aissa & Vitiello 1977 Ghromadorina sp. l Chromadorita sp.2 Prochromadorella neapolitana (De Man 1876) Micoletzky 1924 Prochromadorella septempapillata Platt 1973 Spilophorella euxina Filipjev 1918

4"11 0 0 1"14 1.14 13'71

0"53 0 0 2'40 0-27 5-60