In the frame of the INTERREG III CISM project, sediment cores were collected at 2 stations in the Gulf of Vlorë to study the plankton resting stage assemblages. A total of 87 morphotypes were identified and produced by Dinophyta, Ciliophora, Rotifera, and Crustacea. In 22 cases, the cyst belonged to a species absent from the plankton of the same period. The most abundant resting stages were those produced by
Resting stages produced by plankton organisms in temperate seas accumulate in the bottom sediments of confined coastal areas [
The scarcity of literature on whole resting stage communities encouraged us to describe situations in various parts of the Mediterranean, in order to obtain a rich data set useful for building models and in experimental situations. Here a detailed description of the structure of the marine “seed bank” produced by plankton in the Bay of Vlorë is reported.
The present study also focuses on an Albanian bay that has not been extensively studied from the marine biodiversity point of view. The data from the benthos are compared with analyses of the phytoplankton and microzooplankton [
Moscatello et al. [
An oceanographic campaign was carried out in the Bay of Vlorë from 17th to 23rd of January 2008 aboard the oceanographic vessel “Universitatis”. This survey was conducted as part of the PIC Interreg III Italy, Albania Project for providing technical assistance for the management of an International Centre of Marine Sciences (CISM) in Albania. The sampling period of the present study (January 2008) coincided with that of Moscatello et al. [
In order to investigate the presence and distribution of resting stages produced by plankton species in the area, 2 stations were chosen, representing 2 different types of environment: a deep zone (station 40, depth: 54 m), with sediments of terrigenous mud dominated by
Map of study area showing location of two sampling stations (40, 45) in Bay of Vlorë (Albania).
Samples of bottom sediments were collected in three replicates (named 40 a, b, c and 45 a, b, c) using a Van Veen grab with upper windows that allowed the collection of undisturbed sediment cores. At each station, 2 different PVC corers (h: 30 cm, inner ⃠ 4 and 8 cm) were used in order to obtain 2 different sets of samples. The smaller core was processed to obtain cysts of protists; the larger core was processed to obtain resting eggs of metazoans. This differentiation was necessary because metazoan resting stages are less abundant, so a greater amount of sediment is required. Moreover, their walls are only organic, allowing the adoption of a centrifugation method coupled with filtration to obtain a “clean” sample from a relatively large quantity of sediment. In contrast, protistan cysts are more abundant and have different types of walls (calcareous, siliceous, organic), which complicates the procedure when the whole cyst bank is studied. Thus, the most fruitful method of separating cysts from sediment is filtration through meshes of different sizes.
After extraction, sediment cores were immediately subdivided into 1 cm thick layers, until the 15th cm from the sediment surface. The thickness of 15 cm was chosen because in previous studies we noted that abundances diminished significantly at depths of more than 7–10 cm below the sediment surface [
In the laboratory the small-core samples were treated using a sieving technique consisting of the following steps. The entire sample is homogenized and then subsampled, obtaining 3–5 mL of wet sediment which is passed through a 20 The retained fraction is ultrasonified for 1 min and again passed through a series of sieves (125, 75, and 20
No chemicals were used to disaggregate sediment particles, in order to avoid the dissolution of calcareous and siliceous cyst walls.
Qualitative and quantitative analyses were carried out under an inverted microscope (Zeiss Axiovert S100 equipped with a Nikon Coolpix 990 digital camera) at 200 and 320 magnifications. Both full (i.e., probably viable) and empty (i.e., probably germinated) cysts were considered. At least 1/5 of the finer fraction and all of the >75
All the resting stage morphotypes were identified on the basis of published descriptions, ([
Identification was performed to the lowest possible taxonomic level. As a rule, modern, biological names were used. The paleontological name is reported only for morphotypes whose active stage was not known.
A fixed aliquot (
For the analysis of the large-core samples the Onbè [
For each sample a fixed quantity of wet sediment was treated (
Only full (i.e., probably viable) resting eggs were counted and quantitative data for each
To achieve germination, all putative viable cysts of protists isolated from the sediment were individually positioned in Nunclon microwells (Nalge Nunc International, Roskilde, Denmark) containing
For the 1st cm of the cores, data on resting stage abundance from the 2 sampling stations were obtained by merging the data from the 3 replicates of the 2 sets of samples (those for protistan cysts and metazoan resting eggs). For samples below the first cm, only the 45–200
The PRIMER “DIVERSE” function (Primer-E Ltd, Plymouth, UK) was used to calculate the taxonomic richness (
The relationships between the samples collected at the 2 stations were analyzed by means of nonmetric multidimensional scaling (nMDS) with superimposed hierarchical clustering with a cutoff at 60% similarity (for surface sediments) and 70% (for the sediment core as a whole), while the SIMPER routine was used to identify relative dissimilarity and the
The statistical significance of the differences between the 2 stations was calculated by means of a 2-way crossed analysis of similarities (ANOSIM) on the Bray-Curtis similarity matrix based on the stratigraphy.
All univariate and multivariate analyses were performed using PRIMER v.6 (Primer-E Ltd, Plymouth, UK).
Resting stages were found at all levels of the 15 cm sediment core columns from the 2 investigated sites in the Gulf of Vlorë.
Merging the data from the 2 sets of samples (20–125
List of resting stage (cyst) morphotypes recovered from sediments of Bay of Vlorë (Albania).
Taxon | St.40 | St.45 | ||
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Dinoflagellates | ||||
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⚫ | ⚫ | ○ | |
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⚫ | |||
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⚫ | ○ | ⚫ | ○ |
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⚫ | ○ | ⚫ | ○ |
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⚫ | ○ | ⚫ | ○ |
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⚫ | ⚫ | ||
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⚫ | ○ | ⚫ | |
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⚫ | ○ | ⚫ | ○ |
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⚫ | ○ | ⚫ | ○ |
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⚫ | |||
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⚫ | ⚫ | ||
Ciliates | ||||
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⚫ | |||
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⚫ | |||
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⚫ | |||
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⚫ | ⚫ | ||
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⚫ | ⚫ | ||
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Rotifers | ||||
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⚫ | |||
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⚫ | ○ | ||
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⚫ | |||
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⚫ | |||
Crustaceans Cladocerans | ||||
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⚫ | ⚫ | ||
Crustaceans Copepods | ||||
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⚫ | |||
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⚫ | ○ | ⚫ | ○ |
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⚫ | ⚫ | ○ | |
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⚫ | ○ | ⚫ | |
Unidentified | ||||
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⚫ | |||
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⚫ | |||
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⚫ |
⚫: cysts observed as full (i.e., probably viable). ○: cysts observed as germinated (i.e., empty).
Moreover, analysis of the empty forms found among the 20–125
A total of 36 cyst types were identified as
Identification was frequently impossible due to the presence of previously unreported resting stage morphologies. In such cases, germination experiments allowed the cysts to be attributed to a high level
Photographs of Ciliophora cyst, with two opposite papulae (a). Its empty shell (hatch occurs from one of two papulae) (b). Germinated active stage,
The analysis of surface sediments (the 1st cm of the cores), that is, those most affected by cyst deposition and resuspension/germination, revealed sharp differences between the 2 analysed stations. In total, 36 different resting stage morphotypes were observed in this first layer (Table
Abundance (cysts g−1 dw) of probably viable resting stages (cysts) observed in surface sediments of two stations in Bay of Vlorë (Albania). Values from three replicates are reported.
40a | 40b | 40c | 45a | 45b | 45c | |
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20.1 | 18.3 | 35.1 | 0.0 | 0.0 | 0.0 |
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0.0 | 0.0 | 11.7 | 0.0 | 0.0 | 0.0 |
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20.1 | 0.0 | 0.0 | 0.0 | 0.0 | 59.6 |
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20.1 | 9.2 | 0.0 | 0.0 | 22.2 | 0.0 |
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40.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
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40.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
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0.0 | 0.0 | 11.7 | 0.0 | 0.0 | 0.0 |
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20.1 | 0.0 | 0.0 | 0.0 | 11.1 | 0.0 |
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40.2 | 18.3 | 23.4 | 0.0 | 11.1 | 0.0 |
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0.0 | 9.2 | 0.0 | 0.0 | 0.0 | 0.0 |
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0.0 | 0.0 | 11.7 | 0.0 | 11.1 | 0.0 |
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0.0 | 9.2 | 0.0 | 0.0 | 0.0 | 0.0 |
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40.2 | 18.3 | 46.8 | 0.0 | 0.0 | 0.0 |
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0.0 | 9.2 | 11.7 | 0.0 | 11.1 | 0.0 |
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181.0 | 73.3 | 105.4 | 173.1 | 111.1 | 238.4 |
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80.5 | 64.2 | 58.5 | 230.8 | 0.0 | 0.0 |
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20.1 | 0.0 | 11.7 | 0.0 | 11.1 | 0.0 |
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0.0 | 9.2 | 0.0 | 0.0 | 0.0 | 0.0 |
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0.0 | 0.0 | 11.7 | 0.0 | 11.1 | 0.0 |
Dinophyta sp. 2 | 0.0 | 0.0 | 23.4 | 0.0 | 0.0 | 0.0 |
Dinophyta sp. 17 | 0.0 | 18.3 | 0.0 | 0.0 | 0.0 | 0.0 |
Dinophyta sp. 26 | 0.0 | 18.3 | 0.0 | 0.0 | 0.0 | 0.0 |
Dinophyta sp. 33 | 0.0 | 0.0 | 0.0 | 0.0 | 11.1 | 0.0 |
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1.0 | 0.0 | 0.9 | 0.6 | 0.3 | 0.5 |
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0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
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0.1 | 0.0 | 0.1 | 0.0 | 0.0 | 0.0 |
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0.0 | 0.0 | 0.0 | 0.0 | 11.1 | 0.0 |
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0.0 | 0.0 | 0.0 | 0.0 | 0.1 | 0.1 |
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0.1 | 0.0 | 0.1 | 0.0 | 0.0 | 0.0 |
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0.2 | 0.0 | 0.1 | 0.3 | 0.0 | 0.1 |
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0.3 | 0.2 | 0.0 | 0.2 | 0.0 | 0.1 |
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0.0 | 0.0 | 0.1 | 0.0 | 0.0 | 0.0 |
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1.0 | 0.3 | 0.7 | 1.5 | 0.3 | 0.8 |
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0.1 | 0.0 | 0.1 | 0.0 | 0.0 | 0.0 |
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0.3 | 0.2 | 0.0 | 0.2 | 0.1 | 0.2 |
Cyst type 1 | 0.0 | 0.0 | 0.0 | 57.7 | 0.0 | 0.0 |
Abundance and diversity indices calculated for resting stages in surface sediments at two stations investigated in Bay of Vlorë.
Abundance |
Total density |
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Station 40 |
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Station 45 |
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Abundance: average ± standard deviation from three replicates. Total density: sum of cyst abundances observed in three replicates from each station.
Results of SIMPER analysis for resting stages from surface sediments at stations 40 and 45 in Bay of Vlorë.
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Av. Abund | Av. Sim | Sim/SD | Contrib% | Cum.% |
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Station 40 | |||||
Average similarity: 56.81 | |||||
| |||||
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119.92 | 21.61 | 7.45 | 38.05 | 38.05 |
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67.73 | 15.81 | 6.14 | 27.83 | 65.87 |
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35.13 | 6.44 | 2.78 | 11.34 | 77.21 |
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27.33 | 5.18 | 8.96 | 9.13 | 86.34 |
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24.53 | 4.94 | 7.24 | 8.69 | 95.03 |
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Station 45 | |||||
Average similarity: 40.37 | |||||
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174.21 | 40.03 | 5.87 | 99.16 | 99.16 |
Stations 40 and 45
Average dissimilarity = 58.20.
The most abundant cyst morphotypes in the surface layers were calcareous cysts produced by species of the Calciodinellaceae family (Dinophyta). At station 40, five cyst morphotypes of this family accounted for 95% of total abundance, while at station 45, 99% was accounted for by just one cyst morphotype,
The nMDS ordination (Figure
nMDS plot of surface sediment samples collected at stations 40 and 45 in Bay of Vlorë. Hierarchical clustering superimposed with cutoff at 60% similarity.
At both the investigated stations, a general decrease in total abundances was observed with depth along the sediment columns. At station 40, higher total abundance and diversity values than station 45 were registered (Figure
Resting stage abundance (average
In the nMDS ordination (Figure
nMDS plot of samples from each cm of sediment cores collected at stations 40 and 45 in Bay of Vlorë. Hierarchical clustering superimposed with cutoff at 70% similarity.
The assemblage structure of the two stations differed significantly at all layers (ANOSIM
Results of SIMPER analysis for resting stages in sediment cores collected at stations 40 and 45 in Bay of Vlorë.
|
Av. Abund | Av. Sim | Sim/SD | Contrib% | Cum.% |
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Station 40 | |||||
Average similarity: 44.16 | |||||
| |||||
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1.77 | 8.77 | 0.86 | 19.86 | 19.86 |
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2.10 | 7.00 | 1.31 | 15.86 | 35.72 |
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1.56 | 6.21 | 1.22 | 14.06 | 49.78 |
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1.47 | 5.31 | 1.10 | 12.02 | 61.81 |
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1.14 | 4.47 | 0.98 | 10.13 | 71.93 |
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0.96 | 2.90 | 0.81 | 6.56 | 78.49 |
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0.78 | 1.47 | 0.55 | 3.32 | 81.81 |
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0.73 | 1.43 | 0.51 | 3.23 | 85.04 |
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0.57 | 0.95 | 0.36 | 2.14 | 87.18 |
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0.54 | 0.71 | 0.34 | 1.60 | 88.79 |
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0.44 | 0.69 | 0.33 | 1.57 | 90.36 |
| |||||
Station 45 | |||||
Average similarity: 52.61 | |||||
| |||||
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1.88 | 12.13 | 2.08 | 23.05 | 23.05 |
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1.73 | 10.91 | 1.59 | 20.74 | 43.79 |
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1.43 | 6.73 | 1.12 | 12.80 | 56.59 |
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1.12 | 6.05 | 0.92 | 11.51 | 68.10 |
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1.20 | 6.05 | 1.02 | 11.50 | 79.60 |
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0.84 | 2.73 | 0.63 | 5.19 | 84.79 |
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0.75 | 2.57 | 0.58 | 4.89 | 89.67 |
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0.74 | 2.39 | 0.59 | 4.54 | 94.22 |
Groups 40 and 45.
Average dissimilarity = 58.63.
All putatively viable (i.e., full) protistan cyst types observed were isolated and incubated under controlled conditions to obtain germination. Successful germination generally allowed us to confirm the cyst-based identification, but in some cases it enabled us to go beyond this and discriminate between cysts sharing similar morphology. For example,
Cysts ascribed to the paleontological
An unknown ciliate cyst, with a papula at both extremities, produced an active stage identifiable as belonging to the
The total number of resting stage morphotypes recognized in the present study is particularly high compared with other studies in the Mediterranean. None of these studies gave a number higher than the one reported here, despite being based on a larger geographical area (the whole North Adriatic, in [
As a consequence of its richness, the reported list adds 42 morphotypes to the Albanian list and 13 alternative morphotypes to already known
The discovery of differences in the benthic species assemblage with respect to the plankton is partially due to the use in cyst studies of a terminology derived from paleontological studies which has yet to be standardised with reference to modern terminology. However, it is evident that the active stages in the water column assemblage of the Bay of Vlorë [
The rotifer
While the case of
Also worthy of attention is the observation of a Ciliophora cyst with two papulae on opposite sides (Figure
A study of plankton composition was carried out in the same site during the same scientific cruise (January 2008) as the present study [
It was not possible to correlate cyst abundance along the sediment column with age of deposition, which would require dating of the sediment layers. In any case, our results showed that the total abundance of cysts in the upper layers was up to 10 times greater than in lower ones. The sharp decrease in abundance below the 5th cm of depth, at least at station 40, does, however, suggest that an event occurred at a certain moment in the history of the plankton in the Bay of Vlorë, a suggestion that clearly requires further study. Indeed, due to its position, station 40 is a candidate for studies of the history of cyst production (and their arrival in the sediment). Located in a depression on the seabed, the depth of St. 40 (−54 m) probably favours the sedimentation of fine particles and the depletion of oxygen content, and the deposition and accumulation of sinking resting stages can thus be considered undisturbed. In addition, the observed fall in diversity from lower to upper layers could be correlated with the growth of cultural eutrophication (i.e., urban development), as proposed for Tokyo Bay and Daja Bay [
This situation at St. 45 (depth 28 m) is not completely identical. It is near the slope of a detritus cone where materials from river Vjosa accumulate and marine currents possibly act at a different rate from those acting on St. 40.
Incubation of encysted forms under controlled conditions to obtain germination is a useful tool for confirming the identification made by observation of the cyst. In some cases, different species produce very similar cysts, especially when the morphology is very simple, that is, spherical, without processes or wall structures. In the present study, we observed many Dinophyta cysts with the same basic morphology, that is, round body and smooth brown wall with no apparent signs of paratabulation or spines or processes. Their germination allowed us to classify this basic type into at least 6 species. Round brown cysts are typical of
Conversely, analysis of cysts may allow us to identify species whose active stages are indistinguishable, at least by optical microscope. This is the case in the present study for the
Worthy of special attention here is the recovery during the present study of Dinophyta cysts whose active stages have yet to be identified. As cysts, they are still classified with a paleontological name in accordance with their description from Pleistocene to Pliocene sediment strata in the Mediterranean [
The authors declare that there is no financial interest or conflict of interests involved.
The present study was funded by CoNISMa in the framework of the INTERREG III Italy, Albania Programme, CISM Project (Technical Assistance for Establishing and Management of an International Center for Marine Studies in Albania). The authors thank the crew of the Research Vessel Universitatis (CoNISMa) for the valuable field assistance, Professor Sami Souissi (Université de Lille, France) who took care of the paper editing, and two anonymous referees who were extremely helpful in the improvement of the paper.