Wyniki wyszukiwania - BazTech

1

Research into leeways in the regions of the Świnoujście– Szczecin fairway on the Szczecin Lagoon

Kijewska Monika, Kasyk Lech, Pleskacz Krzysztof

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2019

|

nr 59 (131)

62--71

EN

The paper analyzes the influence of air mass movement on moving (the leeway) surface water in the Świnoujście–Szczecin fairway region on the Szczecin Lagoon. The Szczecin Lagoon includes waters of the Odra River estuary (Poland’s second largest river) and the southern Baltic Sea. To calculate the leeway parameters, a relevant surface drifter was outlined and constructed. The data on the leeway of the drifter was obtained from in-situ experiments conducted on the Szczecin Lagoon in the summer of 2018. In turn, the air mass movement data was recorded at meteorological stations in Trzebież and Świnoujście. A statistical analysis of the leeway parameters of the drifter was also presented. Distributions of the leeway and wind speeds in the Świnoujście–Szczecin fairway regions were established. Moreover, linear regressions between the leeway and wind parameters were performed by decomposing the leeway into its downwind and crosswind components for each 10-minute sample. It is worth highlighting that relationships between these components of the leeway and wind parameters were studied for weak, medium, and stronger winds. This research may be useful for increasing navigation safety in the Świnoujście–Szczecin fairway regions on the Szczecin Lagoon.

2

Comparative analysis of the data on the surface currents and wind parameters generated by numerical models on the Szczecin Lagoon area

Kijewska M., Pleskacz K., Kasyk L.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

|

2018

|

Vol. 12, no. 4

729--737

EN

This study focuses on the investigation of available surface currents and wind parameters for employing them in order to predict the survivor movement in the Szczecin Lagoon waters. For this purpose, the surface currents and wind parameters were generated by selected numerical models and the wind parameters were also measured with the telemetry devices. In this paper, the PM3D hydrodynamic model and the NEMS, ECMWF, GFS weather forecast models have been investigated. The measurements of the wind parameters, recorded at the Brama Torowa I and Trzebież stations, were also analyzed. As part of the research, an expert method was used to evaluate the surface currents parameters. In turn, the method based on comparing the forecasted wind parameters with the measured wind parameters was applied in order to assess uncertainties of these parameters. The comparative analyses of the data on the surface currents and wind parameters have been done and probabilistic models for uncertainties of these forecasted parameters have been formulated. Additionally, relations between the surface currents speeds and the wind speeds, in the case when their directions were consistent, have been also discovered.

3

Condition and population structure of the round goby (Neogobius melanostomus Pallas, 1811) in Szczecin Lagoon in 2010–2014

Czerniejewski P., Brysiewicz A.

Journal of Water and Land Development

|

2018

|

no. 37

49--55

EN

The round goby (Neogobius melanostomus Pallas, 1811) is one of the most invasive fish species in the world, including Poland. 300 fish of this species were collected in the waters of Szczecin lagoon between 2010 and 2014 and examination of the size, sex and age structures of the population and of the condition of the fish was performed. Total length and standard length of all the collected fish amounted to 149.2 mm (±42.21) and 128.1 mm (±38.65), respectively. The age structure of the fish consisted of nine generations, with clear prevalence of the fish aged 3+ and 4+. Mean values of condition factors for the whole fish sample amounted to 0.20 (±0.02). However, no statistically significant differences in particular years were observed (ANOVA, p > 0.05), but the condition of the fish between 2010 and 2011 was slightly higher than between 2013 and 2014. The obtained results indicate that the Szczecin Lagoon environment provides this species with favourable living conditions and it can be stipulated that the quantity of individuals of this fish species will increase.

PL

Babka bycza (Neogobius melanostomus Pallas) jest jednym z najbardziej inwazyjnych gatunków ryb na świecie, w tym również w Polsce. W latach 2010–2014 z wód Zalewu Szczecińskiego pozyskano 300 os. tego gatunku i wykonano badania struktury wielkościowej, płci i wieku populacji oraz kondycji odłowionych ryb. Średnia długość całkowita ciała (TL) oraz długość ciała (SL) wszystkich złowionych ryb wyniosła odpowiednio 149,2 mm (± 42,21) i 128,1 mm (±38,65). Struktura wieku złowionych ryb składała się z 9 roczników, z wyraźną dominacją ryb w wieku 3+ i 4+. Wartości średnie współczynników kondycji dla całej próby ryb wyniosły 0,20 (±0,02), przy czym nie zanotowano różnic istotnych statystycznie w poszczególnych latach (ANOVA, p > 0,05), jakkolwiek kondycja ryb w latach 2010–2011 była nieznacznie lepsza niż w latach 2013–2014. Uzyskane wyniki wskazują, że środowisko Zalewu Szczecińskiego zapewnia osobnikom tego gatunku odpowiednie warunki do życia i można sądzić, iż liczebność osobników tego gatunku będzie się zwiększała.

4

Diversity of social and environmental problems in the Szczecin Lagoon region

Osóch Barbara

Geography and Tourism

|

2017

|

Vol. 5, No. 2

123--131

EN

Szczecin Lagoon and the surrounding lands are diverse in terms of physiography and the extent of resource use. A multitude of these factors causes inevitable conflicts related to the management of this limited space. The conflict of interest usually concerns the issues related to environmental aspects of the Lagoon and human activity. These problems are often caused by the infrastructure providing access to the port of Szczecin, urbanization of floodplains, construction of quays, water pollution, economic activity, i.e. fishing, seasonal mass tourism, reed harvesting. Natural processes have been subjected to strong human impact, resulting in the disappearance of the poorest forest communities, plant species of nature conservation value, decline of animal populations associated with the extensive use of wetlands as well as brackish and dry habitats. Selected components of the geographical space of the basin were evaluated from the perspective of experience, emotions, needs and habits of its users – sailors. The objective of the research was to identify the problems of the aforementioned social groups in the Szczecin Lagoon, as well as to discuss the conflicts related to sailing in the waters of both the Small and Great Lagoon. The conducted analyses are based on the assumption that one and the same place may be a source of different types of experience for people. The perception and valorisation of the space by its users is the result of several factors, e.g. shared personal experience gained in similar material, social and cultural conditions.

5

The quagga mussel (Dreissena rostriformis bugensis Andrusov, 1897) – another Ponto-Caspian dreissenid bivalve in the southern Baltic catchment: the first record from the Szczecin Lagoon

Woźniczka A., Wawrzyniak-Wydrowska B., Radziejewska T., Skrzypacz A.

Oceanologia

|

2016

|

No. 58 (2)

154--159

EN

In 2014, a non-indigenous dreissenid bivalve, the quagga mussel (Dreissena rostriformis bugensis Andrusov, 1897) was for the first time recorded in the Szczecin Lagoon. This was also the first record of the species in the Baltic Sea catchment. The quagga mussel was found to accompany the zebra mussel (Dreissena polymorpha), a non-indigenous bivalve already firmly established in the Lagoon. As indicated by the new immigrant's estimated abundance (4000.0 ± 355.44 ind. M-2) and the zebra mussel to quagga mussel abundance ratio (about 60:40), the immigration of D. rostriformis bugensis to the Lagoon can be regarded as successful. The quagga mussel has already formed a strong and reproducing population which co-occurs with that of the zebra mussel in the area.

6

Nasuwy tafli lodowych na brzegi polskich zalewów przybrzeżnych

Girjatowicz J. P.

Inżynieria Morska i Geotechnika

|

2015

|

nr 2

86—90

PL

Przykłady nasuwów tafli lodowych na brzeg i badanie ich form na Zalewach Wiślanym i Szczecińskim. Hydrologiczno-meteorologiczne przyczyny nasuwania się lodu na brzeg. Wnioski.

EN

Examples of ice sheets onshore thrusting and its forms were explored in the Vistula and Szczecin Lagoons. Hydrometeorological conditions of ice onshore thrusting. Conclusions.

7

Projekt usprawnienia wspomagania monitoringu wód w obszarze Ujścia Odry i Zalewu Szczecińskiego z zastosowaniem technologii informatycznych

Siemianowski L.

Problemy Nauk Stosowanych

|

2014

|

T. 2

35--44

PL

Wstęp i cel: W pracy zaprezentowano koncepcję usprawnienia wspomagania monitoringu jakości wód w obszarze ujścia Odry. Wyszczególniono występujące zagrożenia zanieczyszczeniami ze źródeł komunalnych, przemysłowych oraz ze strony transportu morskiego na torze wodnym Szczecin-Świnoujście. Scharakteryzowano elementy państwowego monitoringu środowiska na Zalewie Szczecińskim prowadzonego we współpracy ze stroną niemiecką. Zobrazowano przepływ danych i informacji z przekazywaniem do światowej bazy danych ONZ-owskiego systemu GEMS WATER Programme. Materiał i metody: Metody syntezy i analizy projektowania systemu Wyniki: Koncepcja usprawnienia ochrony wód z zastosowaniem automatycznej stacji pomiarowo- kontrolnej z transmitowaniem odczytów za pośrednictwem telefonii komórkowej i Internetu. Wniosek: Rozwiązanie pozwoli na znaczące zwiększenie częstości pomiarów, wczesne ostrzeganie (np. przy wycieku ze statku) łatwość sterowania i komunikacji drogą radiową i obniżenie kosztów monitoringu.

EN

Introduction and aim: The project of improving the water monitoring system at Odra estuary was presented. The water contamination risk from urban and industrial sewage sources and possible leakage from shipping transport at fairwater Szczecin-Świnoujście was pointed. The features of Polish state environmental monitoring system on Szczecin Lagoon performed with German cooperation were specified. The informational flows of environmental data and reports with transferring to world database of UNEP GEMS/Water Programme were depicted. Material and methods: Analysis and synthesis during system project developing. Results: The concept of improvement of water quality monitoring system on Szczecin Lagoon in Odra estuary with usage of automatic environmental measurement station was proposed. Conclusion: The solution should supply growth of measurements of water quality parameters and perform early warning function (e.g. during leakage from ship). The radio-wave control and data transmission may determine lower costs of environmental monitoring system.

8

Transgraniczny wymiar sieci Natura 2000 a rozwój zrównoważony obszaru Zalewu Szczecińskiego

Malkowski A.

Zeszyty Naukowe. Problemy Transportu i Logistyki / Uniwersytet Szczeciński

|

2011

|

Nr 15

57-70

EN

The article discusses the functioning of the Natura 2000 networking programme within the area of Szczecin Lagoon. This region is part of an important European ecological network. Its character can be utilized for the purposes of social and economic development. To this effect, the local community must be involved in the process of building the foundations for the area’s sustainable development. The Natura 2000 network creates new challenges for the traditional model of commercial utilization of the Lagoon.

9

Natura 2000 a rybołówstwo Zalewu Szczecińskiego

Malkowska A.

Zeszyty Naukowe. Problemy Transportu i Logistyki / Uniwersytet Szczeciński

|

2011

|

Nr 15

41-56

EN

The article presents Szczecin Lagoon’s spatial, legal and natural conditions from the fisheries’ point of view, and provides a description of the Lagoon communes. Emphasis is put on the Natura 2000 network, which encompasses the area studied. An attempt is made to assess the effect of the Natura 2000 networking programme on the functioning of Szczecin Lagoon fisheries.

10

New and "visiting" fish species collected off the western coast of Poland (Baltic Sea) in 2007-2008 with a description of their parasite fauna

Więcaszek B., Sobecka E., Dudko S., Keszka S.

Oceanologia

|

2011

|

No. 53 (1)

163-179

EN

The first occurrence of striped red mullet Mullus surmuletus in the Pomeranian Bay (in 2007) and the occurrence of three very rarely noted species (tub gurnard Chelidonichthys lucerna, Atlantic horse mackerel Trachurus trachurus, thicklip grey mullet Chelon labrosus) collected in 2007-2008 in the Pomeranian Bay, Szczecin Lagoon and Lake Dąbie are reported. Their expansion is probably due to increased sea temperatures resulting from climate change, as well as the inflow of saline water. The "visitors" hosted eight pathogens from four taxonomic groups: Protozoa, Nematoda, Acanthocephala and Mollusca. Nematodes, the most numerous ones, were found in three host species. All the parasite species were new for the hosts examined; only the larvae of the acanthocephalan Corynosoma strumosum had already been recorded in one of the hosts (Chelidonichthys lucerna). The stomachs of almost all the fish examined were empty, but the species composition of the parasite fauna found showed that the fish must have ingested some food in the Pomeranian Bay.

11

Why should the Odra River mouth area not be regarded as an estuary? A geologist’s point of view

Osadczuk A., Musielak S., Borówka R.K.

Oceanological and Hydrobiological Studies

|

2007

|

Vol. 36, No.2

87-99

EN

The authors find no arguments that would justify application of the term “estuary” to the area of the Odra River discharge into the Baltic Sea. The physiography, geology, and hydrology of the Odra river mouth show that the area possesses many more characteristics typical of flow-through coastal lagoons than those of estuaries. Of key importance in this respect is the Szczecin Lagoon, an extensive, shallow water body separated from the open sea by a barrier intersected by three narrow and long straits. The lagoonal nature of the area is demonstrated also by its geological history.

12

Body weight, condition, and carapace width and length in the Chinese mitten crab (Eriocheir sinensis H. Milne-Edwards, 1853) collected from the Szczecin Lagoon (NW Poland) in spring and autumn 2001

Czerniejewski P., Wawrzyniak W.

Oceanologia

|

2006

|

No. 48 (2)

275-285

EN

A newcomer to the Baltic Sea, the Chinese mitten crab is especially abundant in the Szczecin Lagoon (NW Poland), where it was first reported in 1927. Body weight, and carapace width and length, were studied in 647 individuals collected with fyke nets in the Szczecin Lagoon from 30 March-18 April 2001 and from 5-21 November 2001. 51.01 of the 543 autumn specimens were males, but only 30.97% of the 113 spring specimens were males. Body weight varied from 45.1 to 306.5 g, carapace length from 41.07 to 81.02 mm and carapace width from 46.68 to 88.85 mm. The autumn crabs were significantly heavier than the spring specimens.

13

Chemism of the Szczecin Lagoon and taxonomic structure of cladocera subdivision in 2004

Tyluś K., Chojnacki J.C., Bartoszewska A.

Chemia i Inżynieria Ekologiczna

|

2006

|

Vol. 13, nr 8

819-823

EN

The total area of the Szczecin Lagoon waters along with the straits (with Dąbie Lake and Odra waters) amounts to 910 km2, and its capacity to 3.16 km3. In order to conduct qualitative-quantitative tests of zooplankton against the background of hydrochemical conditions, five permanent water sampling stations were estabilished. The samples for physico-chemical analyses and biological material of the Szczecin Lagoon waters were collected in the spring, summer, autumn and winter of 2004 from five research stations. Hydrochemical analyses comprised: nitrogen and phosphorus forms, dissolved oxygen, percentage of oxygen water saturation, chloride ions, water pH and water temperature, and biological tests comprised qualitative and quantitative analysis of zooplankton.

PL

Całkowita powierzchnia wód Zalewu Szczecińskiego wraz z cieśninami (z jez. Dąbie i wód Odry) wynosi 910 km2, a objętość 3,16 km3. W celu przeprowadzenia badań jakościowo-ilościowych zooplank-tonu na tle warunków hydrochemicznych ustalono pięć stałych stacji pobierania próbek. Próbki do analiz fizyczno-chemicznych i materiał biologiczny wód Zalewu Szczecińskiego pobierano w sezonach: wiosna, lato, jesień i zima 2004 r. z pięciu stanowisk badawczych. Badania hydrochemiczne obejmowały między innymi: formy azotu i fosforu, tlen rozpuszczony, procentowe nasycenie wody tlenem, jony chlorkowe, pH i temperaturę wody a badania biologiczne analizę jakościową i ilościową zooplanktonu.

14

Phytoplankton of the Szczecin Lagoon (the Great Lagoon)

Luścińska M

Oceanological and Hydrobiological Studies

|

2005

|

Vol. 34, No.1

3--29

EN

The 315 species of plankton algae in the Szczecin Lagoon consist mainly of freshwater algae flora. Only a few of them are characteristic for brackish waters. Diatoms and coccal green algae are represented by the highest number of species, whereas the blue-green algae are less heterogeneous. The results of studies were compared with data obtained in the 1950s, 1960s, and 1970s, and, despite fluctuations in the number of species, the contribution structure of particular systematic phytoplankton groups was remarkably similar.

15

Selected heavy metals in bones of small mammals inhabiting the Szczecin Lagoon shores

Miłek E., Musielak D.

Chemia i Inżynieria Ekologiczna

|

2005

|

Vol. 12, nr 12

1395-1400

EN

Contents of selected heavy metals (Pb, Co, and Cd) in bones of small mammals of the families Soricidae, Arvicolidae, and Muridae were determined. The mammals were collected from areas designated as Natura 2000 sites on the Szczecin Lagoon (north-west Poland) as well as from some other sites, including those in major towns. The bones assayed were isolated from pellets of the bam owl Tyto alba (Scop., 1769) and common kestrel Falco tinnunculus (L., 1758). Heavy metal contents were determined with atomic absorption spectrophotometry. The data evidence considerable differences in lead, cadmium, and copper contents between samples collected from various sites.

PL

W niniejszej pracy badano zawartość wybranych metali ciężkich (Pb, Cu i Cd) w układzie kostnym drobnych ssaków z rodzin Soricidae, Arvicolidae i Muridae. Badane próby pochodziły z obszarów wchodzących w skład Natura 2000, położonych nad Zalewem Szczecińskim (północno-zachodnia Polska), a także z kilku innych stanowisk, między innymi z większych aglomeracji miejskich. Materiał kostny pozyskano ze zrzutek sowy płomykówki Tyto alba (Scop., 1769), oraz sokoła pustułki Falco tinnuculus (L., 1758). Stężenie pierwiastków zostało oznaczone przy użyciu spektofotometrii absorbcji atomowej. Wyniki badań wykazały znaczące różnice w zawartości ołowiu, kadmu i miedzi w próbach z poszczególnych stanowisk.

16

Nitrogen and phosphorus form s in Szczecin Lago on in 2003

Chojnacki J.C., Tyluś K.

Chemia i Inżynieria Ekologiczna

|

2005

|

Vol. 12, nr 8

785-789

EN

The Szczecin Lagoon water was sampled with a Ruttner water bottle from the near-surface and near-bottom layers in spring, summer and autumn 2003 from the following 5 sites: Iński Nurt, Roztoka Odrzańska, Mielizna Wolińska, shipping route to Karsibór, and in the vicinity of a buoy marking the exit/entrance to the Trzebież harbour. Laboratory analyses involved assays of all forms of mineral nitrogen, phosphates, and total phosphorus. Results of chemical analyses showed a natural seasonal variability in the parameters assayed, the variability being related to biological activity. Throughout the period of study, mean contents of ammonia nitrogen and phosphates were higher in the near-bottom than in the near-surface layer. Contents of total nitrogen, of the remaining mineral forms of nitrogen as well as those of total phosphorus changed seasonally, in synchrony with their uptake during months of enhanced algal development.

PL

Zalew Szczeciński stanowi część estuarium Odry. Jego powierzchnia wynosi 687 km2, średnia głębokość 3,8 m a objętość wód wynoszących 2,58 km3. Próby z Zalewu Szczecińskiego pobierane były czerpaczem Ruttnera z warstwy przypowierzchniowej i przydennej w sezonach wiosna, lato i jesień 2003 z 5 stanowisk badawczych, następnie w laboratorium wykonano oznaczenia hydrochemiczne wszystkich form azotu mineralnego, fosforanów, fosforu całkowitego, tlen rozpuszczony, procentowe nasycenie wody tlenem. Wyniki analiz chemicznych wykazały naturalna zmienność sezonową wartości oznaczonych wskaźników związanych z działalnością życiową organizmów.

17

Palaeoenvironmental changes in the area of the Szczecin Lagoon (the south western Baltic Sea) as recorded from diatoms

Witkowski A., Latałowa M., Borówka R., Gregorowicz P., Bąk M., Osadczuk A., Święta J., Lutyńska M., Wawrzyniak-Wydrowska B., Woziński R.

Studia Quaternaria

|

2004

|

Vol. 21

153-165

EN

Analyses of diatom assemblages were performed in sediment cores from the Szczecin Lagoon area, as a part of a multidisciplinary research including seismoacoustic profiling and different types of palaeoecological and geological analyses: palynological, macrofossil, malacological, lithological, geochemical and sedimentological. Changes in the composition of a large spectrum of species of the local fauna and flora allowed the reconstruction of environmental conditions during the Late Glacial and Holocene in the Szczecin Lagoon. Succession of the diatom communities is the main topic of the present paper. In the Late Glacial sediments, the diatom flora was scarce and occurred only in core 42/99. In other cores, diatom assemblages characteristic for three phases of the Holocene development (limnic-swampy, marine/brackish-water and lagoonary) of the Szczecin Lagoon were distinguished. The Late Glacial (Older-Dryas (?), Allerod and Younger Dryas) record is incomplete and the flora is predominantly represented by Actinocyclus normanii, Aulacoseira spp, Cocconeis placentula, and Fragilaria brevistriata. The oldest Holocene sediments of the limnic-swampy type, are characterised by freshwater and halophilous diatoms (e.g. Fragilaria brevistriata, Cocconeis placentula and Stephanodiscus hantzschii). In the overlying marine sediments, only occasionally brackish-water taxa (e.g. Planothidium delicatulum, Cocconeis hauniensis) were observed. In the uppermost deposits formed in lagoonary conditions freshwater, halophilous and brackish-water species dominated (e.g. Aulacoseira granulata, Cavinula scutelloides and Epithemia turgida).

18

Studies on the formation and disintegration of grounded ice hummocks in sheltered areas of the southern Baltic coast

Girjatowicz J.P.

Oceanological Studies

|

2001

|

Vol. 30, No. 3-4

3-16

EN

Certain ice-related processes and phenomena associated with formation and disintegration of grounded ice hummocks in sheltered areas are discussed. The descriptions and discussion are based on the author's research carried out over many years in the southern Baltic coastal lagoons. The first part of the paper focuses on the hummocking process which may be invoked to explain the formation of high (up to 10 m above the water level) hummocks. Conditions necessary for hummocking are described and the areas and seasons during which hummocks occur are indicated. In the second part of the paper, the rate at which the hummock height is being reduced during: 1. windless weather with below-zero air temperature, and 2. windy weather (strong wave action) and above-zero air temperature, is discussed. The formation of the so-called ice depression around a hummock is described as well. In the concluding part, attention is being paid to destructive effects of ice in the area affected by hummocking

19

Nutrient status in the Szczecin Lagoon - past, present and future prospects

Pastuszak M., Wielgat M., Sitek S.

Oceanological Studies

|

2001

|

Vol. 30, No. 1-2

59-86

EN

Nutrient concentrations and their annual/interannual variability in the Szczecin Lagoon are shaped by variable riverine water/nutrient discharges and bio-geochemical processes in the Lagoon which modify the dissolved/suspended matter introduced. On an interannual scale, nitrate and phosphate concentrations in the Lagoon in 1969-97 displayed quite considerable variability, with maxima of NO3 coinciding with minima of PO4 concentrations. Both NO3 concentrations in the Lagoon and total nitrogen loads showed a strong positive correlation with the water volumes discharged (r = 0.73 and 0.82, respectively). This dependence was much weaker and negative for PO4 (r = - 0.51), and weak and positive for total phosphorus loads (r = 0.35). It would appear, therefore, that in the catchment area of the Oder River, nitrogen sources are mainly diffuse, while phosphorus is derived from point sources. There was a considerable predominance of nitrates in the inorganic nitrogen pool, but the presence of ammonium in large concentrations in winter and summer was also evident. Among the inorganic nutrient species, nitrates exhibited the highest transformation rate into organically bound forms (over 60%) while passing through the Lagoon. The mechanisms responsible for the nutrient transformation patterns in the Lagoon - temperature, in particular - are discussed in the paper. Phytoplankton production in the Lagoon appeared to be phosphorus-limited in spring and nitrogen-limited in summer.

20

How do currents influence the settlement of Zebra Mussels (Dreissena polymorpha) in the Szczecin Lagoon?

Fenske Ch.

Archives of Hydro-Engineering and Environmental Mechanics

|

2001

|

Vol. 48, nr 3

17-32

EN

Unlike most freshwater bivalves, zebra mussels (Dreissena polymorpha PALLAS) have free swimming larvae and are thus dependent on water currents to guarantee the spreading of their offspring. Although planktonic, the larvae are able to carry out some directed movements. This paper presents investigations carried out in the Szczecin Lagoon, testing the settlement of larvae on different materials at three sites. Zebra mussel larvae preferred the central part of the lagoon for settlement and favoured horizontal over vertical orientation. The rank order referring to number of settled mussels was net > wood > stones > mussel shells > PVc. Water current velocity in the crucial phase was usually very low (<10 cm/s), i.e. not above the limit for settlement. Therefore, other parameters must be involved as well. Two factors are discussed in particular: 1) salinity, and 2) sensory capacities of larvae, linked to the question of their capability of choosing where they settle.