ANNALES • Ser. hist. nat. • 12 • 2002 • 2
original scientific paper	UDC 502,72:574.5(262.3-17)
received: 2002-10-24
THE MEIOFAUNA OF TWO PROTECTED WETLANDS ON THE SLOVENE COAST: THE SKOCJAN INLET AND THE STRUNJAN LAGOON
Borut VRISER
Marine Biology Station, National Institute of Biology, Si-6330 Piran, Fomace 41
ABSTRACT
The paper presents ecological and me io fauna I comparisons between two extremely shallow intracoasta! formations along the Slovene part of the Adriatic Sea, i.e. the Skocjan Inlet in the Bay of Koper and the somewhat smaller Stjuza Lagoon near the sal!-pans of Strunjan. The Inlet is a highly degraded, isolated and stagnant neritic environment, affected with temporary summer anoxias, caused by algal decompositions of huge Ulva aggregations. The Lagoon is an undisturbed sea grass community- Lower meiotaunal diversity and abundances were observed in the Skocjan Inlet, though less as expected, with some mixed "thiobios" symptoms in its highly sulforeductedsurroundings.
Key words: meiofauna, Skocjan Inlet, Strunjan Lagoon, protected wetlands
MEIOFAUNA Di DUE ZONE UNIDE PROTETTE DELIA COSTA SLOVENA: VAL STAC-
NON E LA LAGUNA D! STRUCNANO
SINTESI
L'articolo presenta un confronto ecohgic.o e meiofaunistico tra due formazioni intracostali poco profonde; la 8aia di San Canziano (Val Stagnonj nella baia di Capodistria e la piü piccola laguna Sijuza vicino aile saline di Strugnano. La prima rappresenta un esempio di ambiente altamente degradato, i so lato e stagnante neritico, affetto da temporanee anossie estive caúsate dalla decomposizione di ingenti aggregati dell'atga Ulva. La laguna di Strugnano è invece una comurtith indisturbata di fanerógama marine. Diversité e abbondanza meiofaunisliche sone ri-suitate basse nella Baia di San Canziano, persino pi'u basse del previsto, con alcuni sintomi misti "thiobios" ne Ile vi-cinanze altamente so íforidotte.
Parole chiave: meiofauna, Baia di San Canziano, laguna di Strugnano, zone umide protette
2.36
AINNALES • Ser. hist. nat. ■ 12 • 2002 • 2
Borut VRISER: THE MEIOFAUNA OF TWO PROTECTED WETLANDS ON THE SLOVENE COAST- .. .. 203-210
iNTRODUCTiON
The research carried out so far into the meiofauna of lite Slovene sea has been focused mostly on the open waters of the Cult of Trieste and much less on its shallow margins, the only exception being the extensive exploration of meiobenthos in the Strunjan Lagoon at the end of the 1970s (Vriser, 1979, 1982). The shallow !a-goonar part of Koper Bay, however, has till recently been totally unresearched. It was only the sampling carried out a couple of years ago in the Skocjan Inlet (Cer-melj et ai, 2000) that enabled the origin of this paper, in which a comparison between the two very unique la-goonar environments, surrounded by land and officially protected, is presented. The contribution is not an integral, synchronously implemented study, but a comparative outline of this specific maritime environment at the level of meiobenthos. Here we were able to lean merely on the disposable, although for our particular purpose not always optimal ecological data. The Skocjan Inlet, which presently enjoys the status of a protected environment, will be in the future, after the planned deepening of its aquatory, certainly a subject of numerous investigations.
The study of lagoonar benthic associations and their appurtenant meiofauna, as an important pad of these systems, presently deals with, judging from the literature, particularly the following four topical segments.
In the foreground are largely investigations of bio-productional characteristics, faunistic structure (taxonomy) and diversity ecology of their associations. Since the complexity of the three stated spheres inseparably interact between each other, the mentioned research aspects can be usually found in joint, more complex publications, such as Couil (1969, 1970); den Hartog (1971); Sikora & Sikora (1982); Witte & Zijlstra (1984); ITeeger et a!. (1984); Armonies (1988); Bin Sun et a/. (1993); etc. The fourth and very special sphere of lagoonar studies constitute the research on specific putrescent and to the high concentrations of sulphuretted hydrogen adapted mejobenihic: associations of the extreme maritime environments, the so-called thiobioses (Reise & Ax, 1979, 1980; Powell et a/., 1980, 1983; Meyers et ai, 1988; Wetzel et at., \ 995).
The samplings in the Skocjan Inlet and its stagnant tributaries, which are heavily marked with decaying substrate, were carried out also in order to ascertain the possible "thiobiosity" of this environment.
ECOLOGICAL CONDITIONS
Due to the exceptional specificity of the study area, some more space is dedicated to its ecological outline than actually deserved by this preliminary meiobenthic delineation in view of the extent of the achieved results.
Position, depth configuration and hydrological regime of (he inlet and the Lagoon
The two systems, the one at Skocjan as well as the one at Strunjan, are not entirely natural formations but the result of various human activities carried out in the last few centuries in this shallow marine environment, enabled by the estuaries of the RiJana river in Koper Bay and of the Strunjan stream and its discharge area in Strunjan Bay.
The Skocjan Inlet originated with the linking of the former island of Koper with land through the complex of salt fields, and was finally cut off from the sea by the new Port of Koper, due to which it now communicates with the sea only through the narrow man-made canal. The extensive filling up of the Inlet in the last thirty years has made this once entirely marine environment extremely shallow (the depth of its central part does not exceed 30 cm), virtually cut it in half as far as its surface area is concerned and thus made life in it unbearable. Its only freshwater tributaries, the canals of the Rizarta river and the BadaSevica stream (Fig. 1), are scarce with water, while the smaller and presently more or less freshwater mere (with its own small spring) is only a part of the Inlet, cut off from the main body by the railway embankment. With its spillway past the Inlet, the Badasevica stream has been diverted directly into Koper Bay.
The Strunjan Lagoon (Fig. 2) is for some half a century abandoned fish farm of the- Venetian type. It is an artificial formation, with no direct freshwater inflow, originating from the time when the Strunjan salt-pan complex was formed. It is made up of the smaller discharge lagoon and of the larger main Stjuza Lagoon of the silted former fish-farming pond. The latter is up to half a meter deep and through the mouth of the discharge lagoon (and a series of smaller spillways between the two lagoons) hydrologically (intertidally) fairly effectively and mucli more directly linked with the sea than the Skocjan Inlet.
Temperature, salinity, and oxygen
Thermal conditions in both lagoons are, owing to their shallowness, very severe and seasonally change from one extreme to the other: in the winter between 5° and 10"C (they periodically freeze over), and between 24" and 27°C during the summer, while in other seasons they adapt to the atmospheric temperatures.
Salinity and oxygen content of the Skocjan Inlet's water body oscillate a great deal both temporally and spatially: from periodically almost freshwater conditions in the rainy seasons, via brackish level of salinity to quite high salinities in warmer periods (hypo - hypersaline environment). The salinity and oxygen measurements in the Inlet also showed some extreme spatial
ANNALES • Ser. hist. nat. • 12 2002 • 2
Borisi VKIŠF.R: THE MEIOFAUNA OF TWO PROTECTED WETLANDS ON THE SLOVENE COAST: ..... 203-210
Fig. 1: Study area with sampling stations in Škocjan Inlet
SI. J: Raziskovano območje z razporeditvijo vzorčeval-nth postaj v Škocjanskem zatoku.
changes due to the mixing of strong tidal flows: utterly comparable with the outer condition (in the Bay) along the inner mouth of the tidal canal, and severe along the mouth of the spillway canai of the Rižana river and the Badaševica stream (high salinities, around 40 psu, and consequently critically low, with hypoxic oxygen values - below 30 ppm).
Similar hypoxic and occasionally even anoxic conditions of the water oxygen often occur in late summer in the Inlet itself, although exclusively due to the massive decaying of the huge agglomerations of sea lettuce accumulated at the time of low water levels, saturated nitrites and high temperatures. For the time being, however, we have no detailed accompanying ecological data on the physical-chemical changes in this process, which may at times bring the system into the state of bi-otic collapse. The only permanent freshwater locality of the Inlet can be found in the already mentioned mere, where sea water cart be detected only at its bottom.
Salinity, oxygen content and thermal conditions in the Strunjan Lagoon are owing to the more direct as well as ample water exchange generally i ompletely comparable with those of Strunian Bay, in spite of ever present intertidally turbid oscillations in the I agoon.
Plankton
Phytoplankton density in the Inlet and in the Lagoon is high, in fact higher than in open waters, while its species diversity is much lower. Phytoplankton biomass in terms of chlorophyll a < oncerttration in the škocjan Inlet
Fig. 2: Study area with sampling station in the Strunjan Lagoon.
SI. 2: Raziskovano območje z vzorčevalno postajo v Strunjanski laguni.
generally surpasses the averages of the Gulf of Trieste (around 1.0 pg/l). Chlorophyll a concentrations oscillate a great deal both temporally and spatially, from the low 1.8 jjg/J in winter to the high 220 pg/l in spring IČermelj et at., 2000). Ihe measurements made in the Strunjan Lagoon have shown comparable, although slightly lower values. In the species-poor phytoplankton association, mjcroflagellates are predominant (70 - 90%) (Čermelj et at., 2000).
The zooplankion fauna, too, is poorer in view of its species than in open waters, with predominant naupli larvae and harpacticoid copepods of the benthic-semipelagic type. No great differences can be detected between the Inlet and the Lagoon-
Substrate
Substrate of the major part of the Inlet and the Lagoon is grey-coloured compact-fine argillaceous silt with a slight admixture of sand, with a thin (0.5 - 1 cm) yellowish brown layer of flocculent organic detritus. This is the main natural habitat of the researched, predominantly burrowing meiofauna, which with a branched out capillary system of oxygenated burrows also inhabits up to 5 cm deeper layers of otherwise anaerobic although unreduced unputrescent substrate.
The sediment in the mouth of the Badaševica stream and in the discharge canal of the Rižana river, however, is completely without aerobic surface layer, highly putrescent and thus badly degraded, of black coloured, with high decomposing organic detritus content. Sulfide
205
ANNALES • Ser. hist. nat. • 12 • 2002 • 2
Bonu VRISfcR: THE MEIOFAUNA OF TWO PROTECTED WETLANDS ON THE 5LOVLNE COAST: ..., 203-210
hydrogen remains permanently dissolved in pore water of this substrate in high measured concentrations (0.52.5 minol/l).
Maci ophytobenthos
Macrophytobenthos of the Skocjan Inlet is, owing to its exceptional shallowness, almost entirely limited to the free floating benthopleustophytous and acropleusto-phytous species, such as ijiva rigida (sea lettuce) and, to a smaller extent, Gigartina acicularis and Halopitys in-curvus. As a result of the increased evaporation, low water level and greater amount of nitrites during the summer, water lettuce spreads in the Inlet to such extent that it fills up the entire water volume and due to it and especially owing to its decaying disables the existence of the Cymoaocea sea meadow, which once commanded at that time much deeper Inlet.
The Strunjan Lagoon is overgrown with a normally developed sea meadow consisting predominantly of the species Cymodocea nodosa, and Zoster a noltii on its margins. Species diversity is usual for this phytoassocia-tion, for apart from the two above mentioned species, at least another 7 species are presenl there.
Macrofauna
Macrofauna of the Strunjan Lagoon consists of a very diverse association of characteristic species closely associated with the environment of seagrasses: numerous mollusc (bivalves, gastropods), benthic. crustaceans (mysids, amphipods, decapods, isopods), echinoderms (brittlestars, starfishes), and at least 20 species of poly-chaets.
In the ecologically degraded Skocjan Inlet, no comparable macrofauna association was noted, with the exception of few polychaets and bivalves.
MATERIAL AND METHODS
The first sampling was carried out on October 26°' 1999 at four localities of the Skocjan Inlet, i.e. in its centre (Station 1) and on its margins (Stations 2 - the mere on the other side of the railway embankment, 3 -the Rizana river channel, 4 - the bed of the Badasevica stream) (fig. 1), and at a single locality in the Strunjan Lagoon (Station 5) (fig. 2). The second sampling was carried out on March R,h 2000 in the central parts of the Inlet and the Lagoon only.
We took the substrate samples manually with corer and extracted the meiofauna from the surface area of 10 cm2 and the depth of 5 cm with the sieving-decantation technique in 2 fractions (50 - 125 ¡jm, 125 pm - 1 mrn) of Wieser (1960) and conserved it in 4% formalin with seawater.
The basic physical and chemical characteristics of the water column (temperature, salinity, dissolved oxygen, chlorophyll a) were determined with CTD fine-scale profiler (University of Western Australia, Centre for water research) while at somewhat shallower localities classical methods were partially applied as well. Numerous other analysis techniques for the ecological measurement of the substrate are presented in greater detail in the ecological study made by Čermelj ei a/. (2000).
RESULTS
Qualitative survey of the meiofauna of the Strunjan Lagoon, Skocjan Inlet and their affluents
The first preliminary qualitative analysis (presence of major taxonomic groups and their rough quantitative assessment) of 6 meiofauna samples was carried out in mid-October 1999. The survey showed two groups of samples (Tab. 1).
Tab. 1: Meiofauna of the Strunjan Lagoon and the Skocjan Inlet, together with its affluents, October 1999. Taxa are ranking according to decreasing abundance. Stations: I - Škocjan Inlet's centre, 2 - mere, 3 - Rižana river's discharge canal, 4 - Badasevica stream, and 5 -Strunjan Lagoon (reference sample). Legend: RR-very rare, R-rare, C-common, CC-very common, and £>-dominant.
Tab. J: Meiofavna Strunjanske lagune in Škocjanskega zatoka ter njegovih pritokov, oktober 1999. Taksoni so urejeni po standardnem zaporedju običajne pogostosti. Postaje: 1 - center zatoka, 2 - jezerce, 3 - prelivni kanal Rižane, 4 - Badaševica in 5 Strunjanska laguna (referenčni vzorec). Legenda: RR-zelo redka, R-rcdka, C-običajna, CC-zelo običajna in D-dominantna.
	Škocjan Inlet				Strunjan
	1	2	3	4	5 1
Nematoda	ce	C	RR	R	D
Harpacticoida	R		R		CC
Poiychaeta	CC	RR		RR	CC
Turbellaria	C	RR	RR	R	C
Gastropoda	RR				C
Bivalvia					R
[Kinorhyncha					RR
Acariña					RR
iHydroidea					RR
Ostracoda	D	RR	D	R	
Tanaidacea	R				
(sopo da	RR		R		
Amphipoda	R		R		R
2.36
ANNALES • Ser. hist. nat. - 12 • 2002 • 2
Bonn VRIiiER: THE MfclOFAUNA OF TWO PROTECTED WETLANDS ON THE SIOVENE COAST: .... 203-210
The meiofauna of the three marginal water bodies of the Škocjan Inlet (the Badaševic.n stream, the mere, and the Kižana river discharge canal) with distinct signs of ecologically degraded environment (large quantities of decaying black detritus in the sediment! was taxonomi-cally, and particularly quantitatively, very poor in comparison with the fauna of the Skocjan Inlet and the Strunjan Lagoon. The samples taken in the inlet and Lagoon showed a higher diversity and abundance of individuals.
A comparison between the inlet and the Lagoon, however, showed somewhat lower abundance iri the meiofauna of the Skocjan Inlet, particularly in respect of the Nematoda and Harpacticoida groups. The meio-fauna of the Strunjan Lagoon served as a reference for a less affected environment.
Quantitative survey of the meiofauna of the Strunjan Lagoon and the Skocjan Inlet
The analysis of the meiofauna's samples taken on March 81"' 2000 at two stations in the Skocjan Inlet and comparatively in the Strunjan Lagoon, showed a great difference between the two aquatories than the preliminary qualitative survey carried out in 1999 (Tab. 2).
Tab. 2: Meiofauna! structure and abundance (No. ind. /10 cm') of the Škocjan Inlet and the Strunjan Lagoon, March 2000. Taxa are ranking according to abundances.
Tab. 2: Struktura in abundanca (št. os./10 cm') meio-favne Škocjanskega zatoka in Strunjanske lagune, marec 2000. Taksoni so urejeni po zaporedju abun-danc.
In terms of diversity, and particularly as far as its quantity is concerned, the Skocjan Inlet's meiobenthos is much poorer than that in the Strunjan Lagoon. In the majority of the faunistic groups, the quantitative differ-
ences are also great. In otherwise numerous nematode (Nematoda), present in both environments, the abundances in the Skocjan Inlet were, by half as low than in the referential lagoonar environment, in Turbellaria four times lower. In harpacticoids (Harpacticoida) five times lower, and in polychaets (Poiychaeta) even seven times lower than at the referential station.
The only exception were ostracods (Ostracoda), which with their no less than six times greater abundance than the prevalent meiobenthic group of the Skocjan Inlet mark this specific, although undoubtedly degraded association.
DISCUSSION
In comparison with the Strunjan Lagoon, the assessed smaller diversity of the Skocjan Intel's meiofauna is not particularly explicit and is in fact based merely on the first observations. During the first (preliminary) survey of the Inlet, we did not manage to register no less than four groups: bivalves (Bivalvia), klnorhynchs (Kino-rhyncha), acarrns (Acarina) and colonies of hydroid polyps, which all happen to be common in the Strunjan Lagoon. Particularly symptomatic is the almost total absence of molluscs (bivalves and gastropods), which were hardly registered yet again during the second and much more thorough survey of the Skocjan Inlet. A further supplement to the assessment about a poorer diversity of the Inlet's meiofauna is represented by harpacticoid co-pepods (Harpacticoida), where representatives of only three genera were prevalent: Amphiascus, Rulbam-phiascus and Tisbe. Especially in the last two, some distinct indicators of eutrophic as well as organically polluted environments can be found (Marcotte & Couli, 1974; Vriser, I 936).
Much more distinct between the compared associations of both lagoonar environments are the quantitative differences, where the spans of higher abundances in the individuals of the Strunjan Lagoon are even several times greater in some of the groups. So far, much has been written about the meiofauna of the Strunjan Lagoon (VriSer, 1979, 1982). At this point let us underline that we are dealing with meiobenthos, closely associated on sea grasses, in which some stenovalent species are missing in many groups due to the severe oscillation of ecological factors (particularly temperatures and salinity). But: then again it is distinguished for its bioproductivity, which is higher than in the open sea, which is reflected in greater, especially summer abundances of its dominants. Otherwise it is more or less still comparable with the ordinary meiobenthos of the coastal sea meadows.
However, our assessment of the species diversity in meiobenthic associations in both environments can be unfortunately merely preliminary without a detailed study of the species diversity and a greater spatial covering of the sampling stations.
	Strunjan Lagoon (St. 5)				Škocjan Inlet (St. 1)			
taxa	a	b	c	mean	a	b	c	mean
Nematoda	541	692	837	690	403	307	343	351
Harpacticoida	139	289	341	256	38	36	69	48
Poiychaeta	08	201	93	121	75	12	21	36
Turbellaria	27	28	38	31	8	8	8	8
Gastropoda	-	1	-	0.3	-		1	0.3
Bivalvia	1	-	-	0.3	-	-	i	0.3
Kinorhyncha	-	2	4	2	1	-	-	0.3
Acarina	1	-	-	0.3	-	-	1	0.3
Hydroidea	75	2	-	26	-	-	-	-
Ostracoda	6	20	22	16	73	87	1.30	97
Amphipoda	3	-	1	1.3	-		1	0.3
AINNALES • Ser. hist. nat. ■ 12 • 2002 • 2
Boru! VRiŠER: THE MEIOFAUNA OF TWO PROTECTED WETLANDS ON THE SLOVENE COAST: ..., 203-210
There is no doubt ilia t ali the stated faunistic differences between the two compared environments result from the great ecological differences between them, particularly from the absence of the ruined sea meadow of the Škocjan Inlet and from the anoxic collapses in the summer. It is our impression that the great quantities of decomposing detritus of sea lettuce hvpoxicaliy (and in a later phase anoxically) cover and pollute the surface of the bottom to such extent that the meiofauna can survive, in the short run, only inside this already thinner (max. 1 cm thick) but still aerobic layer and in up to 5 cm deeper capillary network of burrows of the rneio-fauna's burrowing component. The latter is indeed capable of surviving (for up to few weeks) in the hypo-anoxic conditions of this kind as well, to which macro-benthos succumbs in a very short time (as confirmed by numerous foreign and domestic anoxia researchers, e.g. losefson & Widbom, 1988; Austin & Widbom, 1991; Vrišer & Malačič, 1992; Vrišer, 199.5; Moodley et a/., 1997), i.e. in the ecological conditions, when after a week or two the macrofauns has long been destroyed. We presume that e3rly in the autumn life conditions improve in the Inlet due to heavy rains and winds (when decomposing aggregations of algae are washed away), as shown by our October and March samplings. The colder half of the year most probably presents a more favourable ecological period for the fauna of the Škocjan Inlet.
The mentioned survey of processes is probably not utterly uniform even in the period of the most intense summer purification, bul is most likely mosaic: it is a mixture of hydrodinamically more stagnant (ecologically severed) and intertidally more intense (ecologically more favourable) localities with less polluted aggregations. For this purpose, a network of stations would be necessary.
On the other hand it has been noted that the registered faunistic differences between the compared Škocjan inlet and the Strunjan Lagoon are certainly smaller than the ecological differences, or smaller than expected in view of the latter. All this yet again confirms the meiofauna's well-known ecological resistance as well as its flexibility and "belated" response to the environment's unfavourable ecological extremes.
The Škocjan Inlet's benthic conditions couid be perhaps explained with the following working hypothesis. It is possible that the decisive role in the incurred meio-faunal differences in both compared environments is played by the very substrate endofraction of macroben-thos (over 1 mm large organisms living on the bottom, i.e. bivalves, nemerteans, polychaets, oligochaets), which in the critical summer hypoxia cannot survive in the long run and is therefore hard to be found any longer in the Škocjan Inlet. This directly means its loss or absence as well as a reduced presence of "temporary" meiofauna, i.e. juvenile stadia of the future macrofauna.
At the same time this indirectly means - due to the consequential loss of macrobenthic capillary network of oxygenated burrows as oxygen lacunas within the top 5cm - a fatal reduction of the disposable life niches for the remaining "permanent" meiofauna, which is reflected not only in the diversity of species but also in their abundance. In the meiofaunistic literature we have not found an ecosystem that would be ecologically fully comparable to the Škocjan inlet. Some authors (e.g. Con i I, 1969; Sikora & Sikora, 1982), on the other hand, are breaking down the biological processes of the surface layer in the substrate of the shallow lagoonar environments also in the direction of the above mentioned hypothesis.
The other objective of our research was to find an answer to the question, whether there exists, in the Škocjan Inlet and particularly on its margins, a specific and to sulphuretted hydrogen adapted meiobenthic association, the so-called "thiobioses". Certain sources have placed this (in the opinion of some researchers disputable) association in sulfide dependent chemocline which presumably have an ecologtc requirement for sulfide (Powell et al., 1983). Thiobios communities no longer needs the necessary oxygen for its survival (Reise & Ax, 1980; Meyers et al, 1988), in contrast to the normal meiobenthos, therefore, which is (at least in a long run, e.g. a few weeks) certainly still dependant on surface oxygen, also in deeper burrows within anaerobic substrate, even though below n depth of 10 cm.
Of the four investigated localities we can immediately exclude the Inlet itself, which does not fully meet the searched conditions (for the major part of the year its surface sediment is oxygenated), and the brackish mere protected from the decaying aggregations of the organic detritus by the railway embankment. The remaining two localities, i.e. the discharge canals of the Rižana river and the Badaševica stream, are, on the other hand, heavily stagnant and at the bottom burdened with the earlier on defined characteristics of decaying nature and, according to our measurements, with confirmed high sulphide concentrations. This environment is ecologically thus fairly congruent with "thioblosity", while our faunistic data show somewhat mixed picture and only partially correspond to the previously mentioned specialist sources that classify such associations. Similarity with them is shown mainly in the exceptionally sparse harpacticoid copepods (Harpacticoida) and polychaets (Polychaeta) of our samples - in such environments these groups are normally rare - but not in ostra-cods (Ostracoda), which are even predominant in the discharge canal of the Rižana river and the second most common group in the Škocjan Inlet. The very multitude of ostracods in our samples of this environment is a faunistic peculiarity, discordant with thiobiotic associations, and for the time being difficult to explain. The groups Turbellaria and Kinorhyncha, characteristic of
ANNALES • Ser. hist, nat. ■ 12 • 2002 ■ 2
ÖOHit VRI5CR: Tf if MEfOfAUNA OK TWO PROTECTED WETLANDS OH T H t SLOVENE COAST:.... 203-210
decaying environments, were also missing in the two canals.
At the moment, the present survey of these margins of the Skocjan Inlet does not enable us a final judgement, and an answer could only be given upon a more extensive research.
ACKNOWLEDGMENT
I would like to thank Mr. Tthomir Makovec for the preparation of drawings of the study area.
MEIOFAVNA DVEH ZAVAROVANIH MOKRIŠČ SLOVENSKE OBALE: ŠKOCJANSKEGA
ZATOKA IN STRUNJANSKE LAGUNE
Borut VRIŠiR
Morska biološka postaja, Nacionalni inštitut za biologijo, SI-6330 Piran, Fotnače41
POVZETEK
Primerjali 51110 meiofavno dveh plitvih, zaprtih priobalnih lagun, obe s statusom naravovarstveno zaščitenega območja. Škocjanski zatak. ki je danes skoraj že zasut preostanek nekdanjega estuarija reke Rižane, je primer skrajno degradiranega in hidrodinam/čno stagnantnega neritičnega okolja, močno obremenjenega z občasnimi poletnimi anoksijami. Morski travnik tu ni več ohranjen. Povzročajo jih razpadajoče agregacije morske solate U Iva lactuca. Ugotovili smo, da so združbe v Škocjanskem zatoku vrstno in količinsko siromašnejše od združb v Strunjanski laguni. Ugotovljene favn is lične razlike pa so bile vendarle manjše od pričakovanih in občutno manjše od ekoloških. Meiofavna dveh stranskih pritokov zatoka, močno zaznamovanih z gnijočim sedimentom, kaže nekaj delnih znakov specifičnih, na sulfidno okolje prilagojenih tiobioznih združb.
Ključne besede: meiofavna, Škocjanski zatok, Strunjanska laguna, zavarovana mokrišča
REFERENCES
Armonles, W. (1988): Active emergence of meiofauna from inteitidal sediment. Mar. Ecoi. Prog. Ser., 43, 151159.
Austin, M. C, & B. Widbom (1991): Changes in and slow recovery of a meiobenthic nematode assemblage following a hypoxic period in the Guiimar Fjord basin, Sweden. Mar. Bio!., 111, 139-145. Bin Sun, J., W. Fleeger & S. Carney (1993): Sediment microtopography and small-scale spatial distribution of meiofauna. J. Exp. Mar. Biol. Ecol., 167, 73-90. Coull, B. C. (1969): Hydrographic control of meiohen-thos in Bermuda. Repr. Limnology and Oceanography, 14(6), 953-957.
Coull, B. C. (1970): Shallow water meiobenthos of the Bermuda platform. Oecologia, 4, 325-357.
Čermeij, B.( P. Mozetič, O. Bajt, V. Turk, B. Vrišer, N. Kovač, L. Lipej & A. Vukovič (2000): Raziskave in monitoring Škocjanskega zatoka - pregled stanja kakovosti vode in sedimenta v vodni laguni znotraj rezervata in kakovosti vode Badaševice. Ekološka študija. Nacionalni inštitut za biologijo, Morska biološka postaja, Piran, 93 str.
den Hartog, C. (1971): The dynamic aspect in the ecology of sea-grass communities. Thalass. lugosi., 7(1), 101-112.
Fleeger, J. W., G. T. Chandler, G. R. Fitzhugh & f. E. Phillips (1984): Effects of tidal currents on meiofauna densities in vegetated salt marsh sediments. Mar. Ecol. Prog. Ser., 19, 49-53.
Josefsan, A. B« & B. Widbom (1988): Differential response of benthic macrofauna and meiofauna to hypoxia in the Gullmar Fjord basin. Mar. Biol., 100, 31-40.
209
ANNALES • Ser. hist nat. • 12 • 2002 ■ 2
Borut VRBER: THE MiMOFAUNA Of TWO PROTECTED WETLANDS ON THE SLOVENE COAST:..., 103-210
Marcotte, P.. M. & B, C. Coull (1974): Pollution, diversity and meiobenthic communities in the North Adriatic (Bay of Piran, Yugoslavia). Vie Milieu, 24 (2, ser. B), 281-300.
Meyers, M. B., E, N. Powell & H. Fossing (1988):
Movement of oxybiotic and thiobiotic meiofauna in response to changes in pore-water oxygen and sulfide gradients around macro infauna! tubes. Mar. Biol., 98, 395-414,
Moodley, Lv G. J. van der Zwaan, P. M. J. Herman, L. Kempers & P. van Breuget (1997): Differential response of benthic meiofauna to anoxia with special reference to Foraminifera (Protista: Sarcodina). Mar. Ecol- Prog. Ser., 158, 151-163.
Powell, E- N., M. A. Crenshaw & R. M. Rieger (1980):
Adaptations to sultide-system meiofauna. Endproducts of sulfide detoxification in three Turbellarians and a Gastrotrich. Mar. Lcol. Prog. Ser., 2, 169-177. Powell, E. N., T. J. Bright, A. Woods & S. Gittings (1983): Meiofauna arid the thiobios in the East Flower Garden brine seep. Mar, Biol., 73, 269-283. Reise, K. & P. Ax (1979): A meiofaunal "thiobios" limited to the anaerobic sulfide system of marine sands does not exist. Mar. Biol., 54, 225-237. Reise, K. & P. Ax (1980): Statement on the thiobios-hypothesis. Mar. Biol., 58, 31-32. Sikora, W. B. & J. P. Sikora (1982): Ecological implications of the vertical distribution of meiofauna in salt marsh sediments. In: Kennedy, V. S, (ed.); fcstuarine Comparisons. Academic Press, New York, 269-282.
Vrišer, B. (1979): Modifikacije meiofavrie v umetno poluirauerri lagunamem ekosistemu. Biol, vestn., 27, 7586.
Vrišer, B. (1982): Strukturne in bioprodukcijske značilnosti meiofavne v čistem in umetno onesnaženem okolju Strunjanske lagune. Acta Adriat., 23(1/2), .3.39353.
Vrišer, B, (1986): Vpliv organskega onesnaženja na meiofavno priobalnih glinastih muijev Koprskega zaliva. Biol. vestn., 34,93-104.
Vrišer, B. (1995): Meiofauna! investigations and anoxia in the centra! pait of the Gulf of Trieste (Northern Adriatic). Rapp. Comm. int. MerMedit., 34, p. 48. Vrišer, B. & V. Malačič (1992): Hypoxic bottom water and meiofauna in the Gulf of Trieste. Rapp. Comm. int. Mer Medit., 33, p. 356.
Wetzel, M. A., P. Jensen & O, Giere (1995): Oxy-gen/suifide regime and nematode fauna associated with Arenicola marina burrows: new insights in the thiobios case. Mar. Biol., 124,301-312.
Wieser, W. (1960): Benthic studies in Buzzards Say. II. The meiofauna. Limnol. Oceanogr., 5, 121-137. Witte, J. t. }. & J. J. Zi j Istra (1984): The meiofauna of a tidal flat in the western part of the Wadden Sea and its role in the benthic ecosystem. Mar. ficoi. Prog. Ser.,14, 129-138.
210