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Article

Vertical Migration and Habitat Preference of Planktonic Ostracods (Crustacea) in the Deep Adriatic Sea

by
Igor Brautović
,
Barbara Gangai Zovko
* and
Ivona Onofri
Institute for Marine and Coastal Research, University of Dubrovnik, 20000 Dubrovnik, Croatia
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(4), 256; https://doi.org/10.3390/d17040256
Submission received: 24 February 2025 / Revised: 27 March 2025 / Accepted: 27 March 2025 / Published: 4 April 2025
(This article belongs to the Section Marine Diversity)
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Abstract

:
The main objective of our study was to determine for the first time the daily vertical migration (DVM) of 15 planktonic ostracod taxa in the southern Adriatic Sea. We analysed the influence of environmental factors on the Weighted Mean Depth (WMD) of these species, considering differences between males, females and juveniles. Planktonic ostracods were collected during a research cruise in July 2003 at a depth of 1200 m. A total of 152 vertical hauls, divided into 19 sample series, were conducted from the surface to the seafloor at standard oceanographic depths at four times of day. The results showed that the species Archiconchoecia striata, Porroecia spinirostris and Conchoecia magna exhibited significant DVM and migrated daily between the surface and deeper waters. In contrast, the species Porroecia porrecta porrecta, Mikroconchoecia curta, Proceroecia procera, Proceroecia microprocera, Discoconchoecia elegans, Paraconchoecia spinifera and Metaconchoecia rotundata showed less movement. Species with subtle DVM were Porroecia porrecta adriatica, Mikroconchoecia echinulata, Proceroecia macroprocera, Paramollicia rhynchena and Loricoecia loricata, reflecting their adaptation to environmental factors such as hydrographic and biological conditions. Our analysis of WMD revealed noteworthy differences in the vertical distribution of ostracods, focussing on their diurnal migration patterns and depth preferences.
Keywords:
crustacean; zooplankton; WMD; DVM

1. Introduction

Planktonic ostracods are an important class of small bivalved crustaceans well represented in the world’s oceans; about 200 species are known from the family Halocyprididae [1]. In general, they are rare in coastal waters and in temperate latitudes. They are sparsely represented at depths down to 100 m, but in deeper waters they are often the second most abundant group after copepods [2]. However, their ecology in deep-sea habitats is poorly understood [3], and species identification is difficult as it is often based on subtle morphological differences. Nevertheless, these organisms are the subject of research due to their ecological importance in the Mediterranean [4,5,6,7,8,9,10,11]. Their sensitivity to environmental parameters such as salinity, temperature and water depth makes them valuable bioindicators of marine conditions. Early taxonomic work by researchers such as Masoli [8] and Breman [12] laid the foundation for understanding the biodiversity of ostracods in the Mediterranean. These studies identified numerous species and documented their spatial distribution. Salinity and temperature are key environmental factors, as emphasised by Horne and Boomer [13], that strongly influence the distribution of marine ostracods in the Mediterranean, including the southern Adriatic region. The Mediterranean Sea is predominantly characterised by oligotrophic conditions and well-stratified water masses [14], so diel vertical migrations can be crucial to access surface productivity during night hours.
In the Adriatic, planktonic ostracods were studied by Claus [15], who was the first to document their occurrence in the northern Adriatic. During the “Rudolf Virchow” expedition, which covered the entire Adriatic, Schweiger [16] identified four species and came to the conclusion that the abundance of ostracods in the Adriatic decreases from south to north. In later planktological research, ostracods were studied only sporadically [17,18,19,20]. The first detailed study of the ostracods of the Adriatic was carried out by Brautović [21]. The author confirmed the presence of already documented species and gave an overview of the spatial and seasonal distribution of planktonic ostracods in the southern Adriatic basin. All species belong to the order Myodocopida, with most species belonging to the family Halocyprididae, which live exclusively in marine plankton. He also found mesopelagic species at a 100-metre-deep station near the coast of Dubrovnik and explained this phenomenon with the influence of the eastern Mediterranean Intermediate Current. Brautović et al. [22] confirmed that the abundance and species richness of ostracods increase from the northern to the southern Adriatic.
Vertical migration within a 24 h cycle, known as diel vertical migration (DVM), is a phenomenon observed in various zooplankton taxa and is probably the most significant animal migration in terms of biomass on Earth [23]. Vertical migration plays a crucial role in the biological pump by transporting carbon and nitrogen to deeper ocean layers [24,25]. Migrating zooplankton feed near the surface and descend to depths where they defecate, respire and excrete. This behaviour is influenced by factors such as diel and seasonal patterns, as well as local physical conditions [26], providing benefits in feeding, predator avoidance and reproduction [27,28,29,30]. In the southern Adriatic, DVM has been investigated for jellyfish [31], siphonophores [32], larval stages of euphausiids [33] and copepods [26]. In this paper, for the first time, we report diel vertical migration of planktonic ostracods in the Adriatic Sea. This study contains data on pelagic ostracods collected over 96 h at an offshore station in the oligotrophic southern Adriatic Sea to find out how ostracods migrate through the day. Additionally, the composition of ostracods and ontogenetic differences in the vertical distribution of species were analysed, and the Weighted Mean Depth was calculated for all species found.
The study area, the southern Adriatic Sea, is a semi-circular basin with a depth of up to 1200 m (Figure 1), characterised by a shallow northern area and a deep southern basin. About 75% of the incoming water from the Strait of Otranto is retained in a cyclonic gyre that peaks in winter and spring and enriches the surface water with nutrients [34,35]. The open southern Adriatic is considered highly oligotrophic, with the southern basin being the most nutrient-poor zone [36]. Hydrographically, it has three layers: the epipelagic (0–200 m), which is influenced by land waters; the mesopelagic (200–600 m), which is characterised by saline Levantine waters; and the bathypelagic zone (>600 m), in which the North Adriatic Dense Water (NAdDW) forms under the influence of the bora wind [34,37]. The NAdDW influences the water circulation and contributes to the formation of the South Adriatic Dense Water (SAdDW) [38]. The dynamics of the basin are influenced by the exchange with the Ionian Sea via the Bimodal Oscillatory System [14].

2. Materials and Methods

The study of planktonic ostracods was conducted during an oceanographic expedition aboard the research vessel R/V Naše More from July 22 to 28. Sampling was carried out at a single station located in the southern Adriatic Sea (41°44′ N, 17°52′ E) at a maximum depth of 1200 m (Figure 1). This location is situated in the deepest part of the southern Adriatic, making it an ideal site for investigating planktonic ostracods, which are known to be most abundant at mesopelagic depths. Due to unfavourable weather conditions, sampling was temporarily suspended from midday on July 25 until the morning of July 27 (Table 1).
A total of nineteen sampling series, comprising 152 vertical hauls, were collected using a Nansen closing net (diameter: 113 cm, mesh size: 200 µm) across different depth intervals: 0–15 m (above the thermocline), 15–50 m, 50–100 m, 100–200 m, 200–400 m, 400–600 m, 600–800 m and 800–1200 m. Sampling was conducted at different times of the day—morning, noon, evening and night—to account for possible diel vertical migrations of planktonic ostracods. The average towing speed was maintained at 0.5 m/s. Following collection, the samples were preserved in a 2.5% formalin solution buffered with calcium carbonate (CaCO3) in seawater to ensure the structural integrity of the specimens and to prevent degradation. Planktonic ostracods were identified based on the taxonomic key devised by Angel [21], using an Olympus SZX 9 stereomicroscope and a Leica DMLB inverted microscope at magnifications of 100× and 400×. The abundance of ostracods was quantified and expressed as the number of individuals per 100 m3 (ind. 100 m−3). Environmental parameters, including temperature and salinity, were recorded twice daily using two CTD probes: the Idronaut 316 probe, which provides measurements down to 1200 m, and the SeaBird OC25 probe equipped with a Wetlabs FLUO sensor, used for measurements beyond a 200 m depth. Chlorophyll a concentrations were estimated from fluorescence data using software provided by Seabird. Planktonic ostracods within each depth layer were determined by abundance and relative abundance. The Weighted Mean Depth (WMD) of all species was calculated as follows:
W M D = ∑ ( n i z i d i ) / ∑ ( n i z i )
where di is the midpoint of the depth interval of sample i, zi is the thickness of the layer and ni is the number of ind. within each depth layer per 100 m−3. This methodology enables a precise assessment of the vertical distribution of planktonic ostracods and provides insights into their ecological distribution and dynamics.

3. Results

3.1. Hydrographical Conditions

The vertical temperature profile showed only minimal fluctuations throughout the study. Surface temperatures peaked at 27 °C, while temperatures below the thermocline (14 m) decreased until they reached an average of 15.27 ± 0.06 °C at 50 m (Figure 2). A gradual decrease in temperature continued from ~14 °C at 150 m to ~13 °C near the bottom.
Salinity remained relatively high throughout the water column, with values ranging from 38.23 at the surface to 38.95 at the thermocline and 38.64 in the bottom layer (Figure 2).
Chlorophyll concentrations were highest at a 74 m depth (1.26 mg m−3), with an overall average of 1.06 ± 0.12 mg m−3. Surface concentrations averaged 0.49 ± 0.10 mg m−3, while values within the thermocline were slightly higher (0.56 ± 0.02 mg m−3). Beyond 200 m, the chlorophyll levels gradually declined to 0.50 ± 0.02 mg m−3 (Figure 3).

3.2. Species Composition and Diel Vertical Migrations (DVMs)

During the survey, a total of 15 taxa of planktonic ostracods from the family Halocyprididae were identified, divided into 2 subfamilies, 10 genera and 2 subspecies. Only one species, Paraconchoecia oblonga G.W. Müller, 1906, which was previously mentioned in the Adriatic fauna [22], was not found in our study. Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15 show the DVM patterns of planktonic ostracods over several days in July 2003. These figures provide a visual representation of the distribution of species in different depth layers at different times of the day: evening, night, morning and midday.
Archiconchoecia striata (Figure 4) peaked at 82.86 ind. 100 m−3 on 22 July at 15–50 m in the evening. At this time, the population consisted mainly of juveniles (65.5%), with fewer females (20.7%) and males (13.8%).
The population density was also high the following night, but in the morning the highest density shifted to deeper waters (50–200 m), and at midday fewer adults were present at 100–200 m, while juveniles continued to stay in surface water (20 ind. 100 m−3 on 24 July). The midday distribution was broader (0–600 m) but with lower abundance. The species followed a typical diurnal migration cycle, ascending at night and descending during the day. This variability in distribution reflects responses to changing environmental conditions. The average Weighted Mean Depth (WMD) was 194.73 m, indicating deeper migration at night and shallower movement in the morning.
Porroecia spinirostris (Figure 5) reached a peak of 248.57 ind. 100 m−3 on the night of 23 July at a depth of 15–50 m, with 93.1% juveniles. The population shifted deeper by morning (50–100 m) and was more evenly distributed at midday.
The species showed a clear pattern of DVM, probably to avoid predators and to feed. The average WMD was 155.23 m, with a deeper distribution in the morning and a shallower one in the evening.
Porroecia porrecta porrecta (Figure 6) was rarely found in the daytime and evening samples on 23 and 24 July. It was more concentrated in the upper layers from 15 m to 200 m on 23 and 24 July. It peaked at 51.43 ind. 100 m−3 on 28 July at 15–50 m, with 61.1% juveniles. The DVM pattern for this species is limited in the upper 200 m. Their average WMD was 65.82 m, indicating the deepest distribution at midday and the shallowest in the evening.
Porroecia porrecta adriatica, a rarer subspecies, was detected in only 4 out of 18 samples, with a peak of 25.71 ind. 100 m−3 on 28 July at 15–50 m. The DVM pattern was sparse, with occurrences mainly at 50–200 m on 23 July and 0–15 m on 28 July. The average WMD was 136.29 m, with a deeper distribution in the morning and a shallower one at night.
Conchoecia magna (Figure 7) was never found in the surface layer (0–15 m) but throughout the water column and was more dispersed in the nocturnal samples. It reached a peak of 16 ind. 100 m−3 on 23 July at 50–100 m during the night, with 62.5% juveniles. The DVM pattern varied across days, with a maximum depth at the 400–600 m layer on 24 July and a declining abundance by 28 July. The WMD was 372.52 m, with the greatest distribution at midday.
Mikroconchoecia curta (Figure 8) showed a pronounced DVM with a shallow distribution at night and a deeper distribution during the day. The species peaked on 28 July with 26.67 ind. 100 m−3 in the surface layer and consisted mainly of juveniles. The average WMD was 202.43 m, being deepest in the evening and shallowest at midday.
Mikroconchoecia echinulata was rare, with most observations made in deeper waters (200–400 m), indicating a low population density and a limited DVM pattern. The species reached a peak of 4 ind. 100 m−3 at 200–400 m at midday on 23 July.
Proceroecia procera (Figure 9) exhibited DVM from the surface to 800 m. The species reached 106.5 ind. 100 m−3 at a 200–400 m depth on 23 July in the evening. The average WMD was 279.19 m, with the deepest distribution occurring at night and the shallowest in the morning.
Proceroecia macroprocera (Figure 10) showed a subtle DVM, migrating to deeper layers during midday, but no distinct migratory pattern. It was never found in the surface layer. This species peaked at 84.5 ind. 100 m−3 on 27 July at a 200–400 m depth during the night. The average WMD was 349.86 m, with a deeper distribution at midday.
Proceroecia microprocera (Figure 11) showed fluctuations in DVM, with the species mainly staying in deeper layers at night and shallower layers in the evening (never in the surface layer). This species peaked at 42 ind. 100 m−3 on 24 July at 200–400 m in the morning. The average WMD was 317.43 m.
Discoconchoecia elegans (Figure 12) made clear DVM with lower concentrations at night and in the morning, which shifted to lower depths at midday. It was never found in the surface layer. This species reached a peak of 29.5 ind. 100 m−3 at a depth of 200–400 m at midday on 23 July. The average WMD was 345.86 m.
Paraconchoecia spinifera (Figure 13) reached a peak value of 26.6 ind. 100 m−3 in the surface layer on 22 July in the evening and consisted exclusively of juveniles. This was the only finding of this species in the surface layer. This species showed DVM, with the observation that a part of the population always remains below a 200 m depth and a part migrates towards the surface. Their average WMD was 615.21 m, with a deeper midday distribution and a shallower evening concentration.
Paramollicia rhynchena (Figure 14) was the deepest-living ostracod observed, consistently found below 100 m. It peaked at 44.75 ind. 100 m−3 on 27 July at 600–800 m, showing minimal vertical migration. The species had the highest WMD (808.62 m) of all recorded taxa.
Loricoecia loricate showed a sparse DVM pattern with a low abundance and limited vertical migration, indicating a preference for mid-depth layers. It was detected in 55.6% of the samples, with a peak of 4 ind. 100 m−3 in 50–100 m on 23 and 27 July. The average WMD was 713.39 m.
Metaconchoecia rotundata (Figure 15) showed a clear DVM. This species peaked at 58 ind. 100 m−3 on 27 July during midday at a 600–800 m depth, with a WMD of 533.68 m, indicating a strategy of daytime descent and nighttime ascent.
Overall, the species exhibited varying degrees of vertical migration, with some confined to the upper 200 m (e.g., Porroecia porrecta porrecta), while others occupied greater depths (e.g., Paramollicia rhynchena). The WMD values provide insight into the ecological niches and migration behaviours of these ostracods within the water column.

3.3. Population Structure and Depth Distribution

The average population structure of the different species (Figure 16) shows the percentage composition of females, males and juveniles. This distribution represents the predominant reproductive and developmental stages within each species.
Several species, including Porroecia spinirostris, Mikroconchoecia curta, Paraconchoecia spinifera and Paramollicia rhynchena, had juveniles comprising over 80% of their populations, indicating high reproductive rates or significant recruitment of juveniles during the sampling period (Figure 16). In contrast, species like M. curta showed a more balanced sex ratio, indicating stable population structures in habitat preferences. C. magna and M. rotundata were dominated by females, possibly due to sex-specific survival advantages, characteristics of the mating system or environmental factors favouring females. Meanwhile, Porroecia porrecta porrecta and Porroecia porrecta adriatica showed a more even distribution across all life stages, suggesting homogeneous age structures or stable population dynamics. It is noteworthy that P. rhynchena had the highest proportion of juveniles (90.4%), while Metaconchoecia rotundata had the lowest proportion (47.46%). Females were most common in M. rotundata (28.76%), while P. rhynchena had the lowest proportion of females (5.92%). P. p. adriatica had the highest proportion of males (26.67%), while P. rhynchena had the lowest proportion (3.79%) (Figure 16).
The Weighted Mean Depth (WMD) (Figure 17) provides insights into vertical migration patterns and habitat preferences of the species across different times of the day (morning, midday, evening and night).
Several species, including Loricoecia loricate, Metaconchoecia rotundata and Conchoecia magna, showed pronounced vertical migrations and a marked increase in WMD in the evening and a sharp decrease at night, suggesting active diurnal migrations. Species such as Paramollicia rhynchena and Loricoecia loricata consistently reside in deeper waters, which is reflected in high WMD values, while Porroecia porrecta porrecta and Porroecia porrecta adriatica prefer shallower depths. Variability in WMD was particularly noticeable in C. magna and M. curta, likely reflecting responses to environmental factors or predation pressure. Paraconchoecia spinifera demonstrated the greatest depth variability, while most other species showed relatively stable depth distributions. These findings highlight the species’ vertical partitioning of the water column and provide insights into their ecological niches and behaviours. Overall, the figure shows how the different species partition the water column temporally and spatially and sheds light on their ecological niches and behaviours in the water column.

4. Discussion

This study provides valuable insights into the patterns of daily vertical migration (DVM) of ostracods in the southern Adriatic Sea. Of the 16 planktonic ostracods recorded in the Adriatic Sea [21], 15 species were identified in this study. The only species not recorded in our research is Paraconchoecia oblonga, previously recorded by Brautović [22]. Thus, the composition of the plankton was consistent with previous findings on the deep southern Adriatic [21] and indicates a stable ostracod community. This stability is likely maintained by the persistent cyclonic gyre, a well-established oceanographic feature in this region [39], which plays a crucial role in regulating the southern Adriatic ecosystem.
Although climatological analyses of the Adriatic indicate increasing salinity in all water layers, probably related to the exceptionally warm summer of 2003 and the influx of Levantine Intermediate Water [40,41], this had no effect on the stability of the plankton community. Therefore, we conclude that the environmental conditions observed throughout the study period indicate that the sampling was conducted in a stable hydrographic system [31,40].
The presence of migratory species in the samples was strongly influenced by the time of day, with almost all migratory species beginning their vertical movements around sunset and sunrise. The abundance patterns suggest that these species spend a considerable amount of time on vertical migrations, which is consistent with [42], whose authors observed similar behaviour. Species such as Archiconchoecia striata, Porroecia spinirostris, Mikroconchoecia curta and Conchoecia magna showed clear DVM patterns, migrating to the surface at night and descending during the day to avoid predators. This behaviour is in accordance with observations from the north-eastern Atlantic [43]. In contrast, Porroecia porrecta porrecta remained in the upper 200 m and showed stable depth preferences without pronounced migrations, which is consistent with studies from the North Atlantic [3,43]. Species with minimal DVM, such as Paramollicia rhynchena and Loricoecia loricata, have been found in deep-sea environments characterised by low predation pressure and specialised resources associated with mesopelagic niches that provide stable food availability [1].
Vertical migration strategies vary by species and region. Studies off the north-central coast of Chile have shown that although planktonic ostracods can perform extensive vertical migrations, they are most abundant at mid-latitudes between 200 and 300 m, similar to our results. This depth preference indicates a complex interplay between migratory behaviour and environmental factors such as hydrographic conditions and predators [44]. Comparisons between the southern Adriatic and other marine ecosystems are challenging due to the limited data available. However, in the subtropical eastern North Pacific, the body size of ostracods increased with depth, suggesting that larger individuals inhabit deeper layers as an adaptation to environmental conditions or predation pressure [45]. Our data support this hypothesis, as larger species such as Paramollicia rhynchena were found in the deepest layers of the Adriatic Sea and exhibited minimal DVM. These observations emphasise the role of environmental factors and ecological strategies in shaping the vertical distribution of ostracods. The DVM patterns of ostracods in the deep Adriatic are comparable to those observed in other zooplankton groups, such as siphonophores, jellyfish, euphausiid larvae and copepods, in the Adriatic, which also show DVM as a strategy to optimise feeding and minimise predation [26,31,32,46] (Table 2).
For example, species such as Porroecia spinirostris, Mikroconchoecia curta and Archiconchoecia striata ascended to surface waters at night, exhibiting a similar pattern to other zooplankton groups. However, the migration patterns of ostracods are more conservative than those of copepods, jellyfish and euphausiids, which have broader vertical distributions [33,47]. These differences in migration amplitudes reflect the ecological niches and predator–prey dynamics unique to each group [42,48].
This pattern of conservative vertical migration is evident in their depth preferences throughout the day, particularly in the southern Adriatic. During the day, of all the zooplankton groups, only two ostracod species, Archiconchoecia striata and Metaconchoecia rotundata, were found in the upper 100 metres (Table 2), while in the upper mesopelagic zone (100–400 m), ostracods such as Porroecia porrecta porrecta, Proceroecia procera, Proceroecia microprocera and Discoconchoecia elegans coexisted with calanoid copepods, jellyfish and siphonophores. In the lower mesopelagic zone (400–800 m), species such as Archiconchoecia striata, Porroecia spinirostris, Conchoecia magna, Mikroconchoecia curta, Paraconchoecia spinifera and Metaconchoecia rotundata were found alongside euphausiids, siphonophores and jellyfish. At night, the vertical migration patterns were more pronounced. Several ostracod species (C. magna, M. curta, P. spinifera and M. rotundata) moved to the surface, together with calanoid copepods, euphausiids, jellyfish and siphonophores, while others remained in the mesopelagic and bathypelagic zone. These depth preferences suggest that ostracods have more conservative vertical movements compared to other zooplankton groups, aligning with observations from the North Atlantic [43]. The variability of vertical migration amplitudes among zooplankton taxa reflects differences in ecological niches and predator–prey dynamics [42,48,49]. Ostracods serve as prey for various marine predators, including siphonophores [50], mesopelagic fish [51], euphausiids [52], jellyfish [53] and pelagic decapods [54]. These predator–prey interactions shape their vertical distribution and migratory behaviour.
The values for the Weighted Mean Depth showed species-specific depth preferences and migration amplitudes. Species such as Archiconchoecia striata, Porroecia spinirostris, Mikroconchoecia curta, Paraconchoecia spinifera and Metaconchoecia rotundata showed a pronounced DVM, ascending to shallower waters at night to feed and descending during the day to avoid predators [43]. In contrast, Paramollicia rhynchena preferred deeper, more stable habitats, which is consistent with observations that larger, deeper-dwelling species remain below 600 m [1]. These results emphasise the different survival strategies that ostracods use in response to environmental conditions, predators and resource availability [3].
The sex ratio provided information about the reproductive strategies and population dynamics. In most species, juveniles dominated the population, especially in Paraconchoecia spinifera, Mikroconchoecia curta, Porroecia spinirostris and Paramollicia rhynchena, indicating a high reproductive output and successful recruitment during the study period [3]. The highest proportion of juveniles of the aforementioned species is consistent with previous findings [5,22]. This pattern could be due to favourable environmental conditions, such as optimal temperature and food availability [55]. In contrast, species such as Archiconchoecia striata, Proceroecia microprocera and Metaconchoecia rotundata showed a balanced sex ratio, which was also comparable to that for the mentioned species in previous studies [5,22], indicating stable populations with similar survival pressures and reproductive success [48]. Some species, such as Mikroconchoecia echinulata, Proceroecia macroprocera and Loricoecia loricata, showed a female-biased sex ratio, suggesting that females of these species may have a reproductive advantage, better access to food or more effective avoidance of predators [48]. In addition, Porroecia porrecta adriatica and Porroecia porrecta porrecta showed a relatively even distribution of juveniles, males and females, suggesting that their population dynamics are balanced and that reproductive output is consistent across all life stages.
Overall, this study enhances our understanding of DVM patterns and ecological strategies of ostracods in the southern Adriatic. It also provides valuable insights into how environmental conditions, predator–prey interactions and reproductive dynamics influence their vertical distribution and migratory behaviour. Future studies comparing these results with other marine ecosystems will be crucial to further elucidate the complex interactions that influence ostracod communities worldwide.

5. Conclusions

This study provides a comprehensive analysis of the diel vertical migration and distribution patterns of planktonic ostracods in the Adriatic Sea, highlighting their ecological significance and adaptation strategies. Our results show that ostracods use different vertical distribution patterns to navigate their dynamic marine environment and thus contribute to the stability and functionality of pelagic ecosystems. Although the observed vertical migrations of ostracods are less pronounced than those of other zooplankton groups, they remain ecologically relevant. The variations in migration amplitudes and depths between taxa indicate a broad spectrum of ecological niches and adaptive mechanisms that improve ecosystem resilience. We consider these results representative for the southern Adriatic. However, sampling limitations should be taken into account when interpreting these results. Sampling limitations, such as dependence on favourable weather conditions and choice of net mesh size, can lead to biases such that smaller or elusive species may be under-represented, especially in deeper waters. Future research should aim to refine sampling techniques and extend temporal and spatial coverage to further elucidate the ecological role of ostracods in the Adriatic Sea.

Author Contributions

Conceptualisation, I.B. and B.G.Z.; Ideas, formulation of overarching research goals and aims, methodology, I.B. and I.O.; Design of methodology, validation, I.B. and B.G.Z.; Verification of the activity of the overall results research outputs, formal analysis, B.G.Z. and I.B.; Application of statistical, mathematical, computational, or other formal techniques to analyse or synthesise study data, investigation, I.B. and I.O.; Conducting the research and investigation process, specifically performing the experiments or data collection, resources, I.B.; Provision of study materials, laboratory samples, instrumentation, computing resources or other analysis tools, data curation, I.B.; Management activities to annotate (produce metadata), scrub data and maintain research data (including software code, where it was necessary, for interpreting the data) for initial use and later re-use, writing—original draft preparation, B.G.Z. and I.B.; Preparation, creation and presentation of the published work, specifically writing the initial draft (including substantive translation), writing—review and editing, B.G.Z. and I.O.; Preparation, creation and/or presentation of the published work by those from the original research group, including critical review, commentary, revision (at pre- or post-publication stages) and visualisation, I.B.; Project Administration, I.B.; Management and coordination responsibility for the research activity planning and execution, funding acquisition, I.B.; Acquisition of the financial support for the project leading to this publication. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Ministry of Science, Education and Sports of the Republic of Croatia, Research Project No. 275-0982705-3047.

Institutional Review Board Statement

Not applicable. We declare that we do not need ethical approval regarding our work on the marine zooplankton.

Data Availability Statement

Dataset available on request from the authors. The raw data supporting the conclusions of this article will be made available by the authors on request.

Acknowledgments

We acknowledge the support provided by the Ministry of Science, Education and Sports of the Republic of Croatia and the University of Dubrovnik (Croatia).

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
DVMDaily vertical migration
WMDWeighted Mean Depth
NAdDW North Adriatic Dense Water
SAdDWSouth Adriatic Dense Water

References

  1. Angel, M.V. Marine Planktonic Ostracods. In Synopses of the British Fauna; Kermack, D.M., Barnes, R.S.K., Crothers, J.H., Eds.; Linnean Society of London and The Estuarine and Coastal Sciences Association by the Field Studies Council: Shrewsbury, UK, 1993; Volume 48, pp. 1–239. [Google Scholar]
  2. Nigro, L.M.; Angel, M.V.; Blachowiak-Samolyk, K.; Hopcroft, R.R.; Bucklin, A. Identification, Discrimination, and Discovery of Species of Marine Planktonic Ostracods Using DNA Barcodes. PLoS ONE 2016, 11, e0146327. [Google Scholar] [CrossRef] [PubMed]
  3. Angel, M.V.; Blachowiak-Samolyk, K.; Drapun, I.; Castillo, R. Changes in the Composition of Planktonic Ostracod Populations across a Range of Latitudes in the North-East Atlantic. Prog. Oceanogr. 2007, 73, 60–78. [Google Scholar] [CrossRef]
  4. Ferrari, I.; McKenzie, K.G.; Benassi, G.; Sei, S.; Magnani, M.C. New Data on Planktonic Ostracoda from the Southern Waters (Thyrrhenian Sea and Ionian Sea). In Caratterizzazione Ambientale Marina del Sistema Eolie e dei Bacini di Cefalù e Gioia (EOCUMM95); Faranda, F.M., Povero, P., Eds.; G. Lang: Genova, Italy, 1996; pp. 255–296. [Google Scholar]
  5. Brautović, I.; Bojanić, N.; Batistić, M.; Carić, M. Annual Variability of Planktonic Ostracods (Crustacea) in the South Adriatic Sea. Mar. Ecol. 2006, 27, 124–132. [Google Scholar] [CrossRef]
  6. Bonaduce, G.; Ciampo, G.; Masoli, M. Distribution of Ostracoda in the Adriatic Sea. In Pubblicazioni Della Stazione Zoologica di Napoli; L.S. Olschki: Firenze, Italy, 1975; Volume 40, pp. 1–154. [Google Scholar]
  7. Kubanç, N. Diversity and Comparison of Ostracoda of South Marmara Sea. J. Black Sea/Mediterr. Environ. 2005, 11, 257–275. [Google Scholar]
  8. Masoli, M. Ostracodi Tirreniani di Maria Pia Di Alghero (Sassari). Bull. Soc. Sarda Sci. Nat. 1968, 3, 1–18. [Google Scholar]
  9. Oertli, H.J. Atlas des Ostracodes de France; Elf-Aquitaine: Paris, France, 1985; p. 9. [Google Scholar]
  10. Benassi, G.; Ferrari, I.; Rossi, V.; Sei, S.; Angel, M.V. Distribution and Taxonomy of Planktonic Ostracods of the Eolian Islands (Mediterranean Sea). In What About Ostracoda! Elf Exploration Production: Courbevoie, France, 1998; pp. 3–25. [Google Scholar]
  11. Perçin Paçal, F. The Ecology of the Ostracoda (Crustacea) Species Obtained from the Coasts of Iskenderun Bay (Eastern Mediterranean Sea). J. Black Sea/Mediterr. Environ. 2011, 17, 127–144. [Google Scholar]
  12. Breman, B. The Distribution of Ostracodes in the Bottom Sediments of the Adriatic Sea; Krips Repro: Meppel, The Netherlands, 1975; pp. 50–165. [Google Scholar]
  13. Horne, D.J.; Boomer, I. The Role of Ostracoda in Saltmarsh Meiofaunal Communities. In British Saltmarshes; Sherwood, B.R., Gardiner, B.G., Harris, T., Eds.; Cambridge University Press: Cambridge, UK, 2000; pp. 182–202. [Google Scholar]
  14. Civitarese, G.; Gačić, M.; Batistić, M.; Bensi, M.; Cardin, V.; Dulčić, J.; Garić, R.; Menna, M. The BiOS Mechanism: History, Theory, Implications. Prog. Oceanogr. 2023, 216, 103056. [Google Scholar] [CrossRef]
  15. Claus, C. Die Halocypriden des Atlantischen Oceans und Mittelmeeres; Alfred Holder: Wien, Austria, 1891; 82p. [Google Scholar]
  16. Schweiger, L. Adriatische Cladoceren und Plankton-Ostracoden. Sitzungsber. Akad. Wiss. Wien 1912, 121, 239–272. [Google Scholar]
  17. Gamulin, T. Prilog Poznavanju Zooplanktona Srednjedalmatinskog Otočnog Područja. Acta Adriat. 1948, 3, 1–38. [Google Scholar]
  18. Gooday, A.J.; Angel, M.V. Distribution of Planktonic Ostracoda (Halocyprididae) in the North Adriatic with the Description of a New Subspecies, Conchoecia porrecta adriatica. Crustaceana 1977, XX, 139–154. [Google Scholar]
  19. Hure, J. Distribution Annuelle Verticale du Zooplancton sur une Station de L’Adriatique Méridionale. Acta Adriat. 1955, 7, 1–72. [Google Scholar]
  20. Hure, J. Diurnal Migration and Seasonal Vertical Distribution of Zooplankton in the Deepest Sea. Acta Adriat. 1961, 9, 1–59. [Google Scholar]
  21. Brautović, I. Planktonic Ostracods of the South Adriatic Basin. In Proceedings of the 35th CIESM Congress, Dubrovnik, Croatia, 1–5 June 1998; pp. 384–385. [Google Scholar]
  22. Brautović, I.; Bojanić, N.; Vidjak, O.; Grbec, B.; Gangai Zovko, B. Composition and Distribution Patterns of Marine Planktonic Ostracods (Crustacea, Ostracoda) in the Adriatic Sea—A Historical Perspective. Acta Adriat. 2018, 59, 71–90. [Google Scholar] [CrossRef]
  23. Hays, G.C. A Review of the Adaptive Significance and Ecosystem Consequences of Zooplankton Diel Vertical Migrations. Hydrobiologia 2003, 503, 163–170. [Google Scholar] [CrossRef]
  24. Hays, G.; Harris, R.; Head, R. The Vertical Nitrogen Flux Caused by Zooplankton Diel Vertical Migration. Mar. Ecol. Prog. Ser. 1997, 160, 57–62. [Google Scholar] [CrossRef]
  25. Schnetzer, A.; Steinberg, D.K. Active Transport of Particulate Organic Carbon and Nitrogen by Vertically Migrating Zooplankton in the Sargasso Sea. Mar. Ecol. Prog. Ser. 2002, 234, 71–84. [Google Scholar] [CrossRef]
  26. Hure, M.; Batistić, M.; Garić, R. Copepod Diel Vertical Distribution in the Open Southern Adriatic Sea (NE Mediterranean) under Two Different Environmental Conditions. Water 2022, 14, 1901. [Google Scholar] [CrossRef]
  27. Conroy, J.A.; Steinberg, D.K.; Thibodeau, P.S.; Schofield, O. Zooplankton Diel Vertical Migration during Antarctic Summer. Deep Sea Res. Part I Oceanogr. Res. Pap. 2020, 162, 103324. [Google Scholar] [CrossRef]
  28. Frank, T.; Widder, E. Effects of a Decrease in Downwelling Irradiance on the Daytime Vertical Distribution Patterns of Zooplankton and Micronekton. Mar. Biol. 2002, 140, 1181–1193. [Google Scholar]
  29. Pearre, S. Eat and Run? The Hunger/Satiation Hypothesis in Vertical Migration: History, Evidence and Consequences. Biol. Rev. 2003, 78, 1–79. [Google Scholar] [CrossRef]
  30. Williamson, C.E.; Fischer, J.M.; Bollens, S.M.; Overholt, E.P.; Breckenridge, J.K. Toward a More Comprehensive Theory of Zooplankton Diel Vertical Migration: Integrating Ultraviolet Radiation and Water Transparency into the Biotic Paradigm. Limnol. Oceanogr. 2011, 56, 1603–1623. [Google Scholar] [CrossRef]
  31. Lučić, D.; Benović, A.; Morović, M.; Batistić, M.; Onofri, I. Diel Vertical Migration of Medusae in the Open Southern Adriatic Sea over a Short Time Period (July 2003). Mar. Ecol. 2009, 30, 16–32. [Google Scholar]
  32. Lučić, D.; Benović, A.; Batistić, M.; Morović, M.; Onofri, I.; Molinero, J.C.; Miloslavić, M. A Short-Term Investigation of Diel Vertical Migrations of the Calycophoran Siphonophora in the Open South Adriatic Sea (July 2003). Acta Adriat. 2011, 52, 159–172. [Google Scholar]
  33. Gangai, B.; Lučić, D.; Morović, M.; Brautović, I.; Miloslavić, M. Population Structure and Diel Vertical Migration of Euphausiid Larvae in the Open Southern Adriatic Sea (July 2003). Crustaceana 2012, 85, 659–684. [Google Scholar] [CrossRef]
  34. Gačić, M.; Civitarese, G.; Ursella, L. Spatial and Seasonal Variability of Water and Biochemical Fluxes in the Adriatic Sea. In The Eastern Mediterranean as a Laboratory Basin for the Assessment of Contrasting Ecosystems; Malanotte-Rizzoli, P., Eremeev, V.N., Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1999; pp. 335–357. [Google Scholar]
  35. Fonda-Umani, S. Pelagic Production and Biomass in the Adriatic Sea. Sci. Mar. 1996, 60, 65–77. [Google Scholar]
  36. Viličić, D. Fitoplankton u Ekološkom Sustavu Mora; Školska Knjiga: Zagreb, Croatia, 2003; 196p. [Google Scholar]
  37. Ivančan-Picek, B.; Tutiš, V. A Case Study of a Severe Adriatic Bora on 28 December 1992. Tellus 1996, 48A, 357–367. [Google Scholar] [CrossRef]
  38. Vilibić, I.; Supić, N. Dense Water Generation on the Shelf: The Case of the Adriatic Sea. Ocean Dyn. 2005, 55, 403–415. [Google Scholar]
  39. Gačić, M.; Civitarese, G.; Miserocchi, S.; Cardin, V.; Crise, A.; Mauri, E. The Open-Ocean Convection in the Southern Adriatic: A Controlling Mechanism of the Spring Phytoplankton Bloom. Cont. Shelf Res. 2002, 22, 1897–1908. [Google Scholar] [CrossRef]
  40. Morović, M.; Matić, F.; Grbec, B.; Dadić, V.; Ivanković, D. South Adriatic Phenomena Observable through VOS XBT and Other ADRICOSM Data. Acta Adriat. 2006, 47, 33–49. [Google Scholar]
  41. Grbec, B.; Morović, M.; Beg Paklar, G.; Kušpilić, G.; Matijević, S.; Matić, F.; Ninčević Gladan, Ž. The Relationship between Atmospheric Variability and Productivity in the Adriatic Sea Area. J. Mar. Biol. Assoc. 2009, 89, 1–10. [Google Scholar]
  42. Roe, H.S.J. Observations on the Diurnal Vertical Migrations of an Oceanic Animal Community. Mar. Biol. 1974, 28, 99–113. [Google Scholar]
  43. Angel, M.V.; Fasham, M.J.R. Analysis of the Vertical and Geographic Distribution of the Abundant Species of Planktonic Ostracods in the North-East Atlantic. J. Mar. Biol. Assoc. 1975, 55, 709–737. [Google Scholar] [CrossRef]
  44. Mujica, A.; Nava, M.L.; Leiva-Dietz, F. Planktonic Ostracods off the North-Central Coast of Chile. Latin Am. J. Aquat. Res. 2022, 50, 68–77. [Google Scholar]
  45. Liao, T.; Tan, Y.; Liu, H.; Yu, L.; Li, K. Vertical Distribution of Planktonic Ostracods (Halocyprididae) in the Northeastern and Central South China Sea: Significance of Large-Sized Species in Deep Waters. Fish. Oceanogr. 2022, 31, 497–509. [Google Scholar]
  46. Gangai Zovko, B.; Lučić, D.; Hure, M.; Onofri, I.; Pestorić, B. Composition and Diel Vertical Distribution of Euphausiid Larvae (Calyptopis Stage) in the Deep Southern Adriatic. Oceanologia 2018, 60, 128–138. [Google Scholar] [CrossRef]
  47. Tao, Z.; Xian, H.; Luan, Z.; Nan, F.; Wang, Y.; Sun, S. The Diel Vertical Distribution and Carbon Biomass of the Zooplankton Community in the Caroline Seamount Area of the Western Tropical Pacific Ocean. Sci. Rep. 2022, 12, 18908. [Google Scholar] [CrossRef] [PubMed]
  48. Angel, M.V.; Blachowiak-Samolyk, K.; Chavtur, V.G. An Atlas of Atlantic Planktonic Ostracoda. Available online: https://www.nhm.ac.uk/research-curation/scientific-resources/biodiversity/global-biodiversity/atlantic-ostracods/index.html (accessed on 1 July 2024).
  49. Nogueira Júnior, M.; Brandini, F.P.; Codina, J.C.U. Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora, and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight). PLoS ONE 2015, 10, e0144161. [Google Scholar]
  50. Damian-Serrano, A.; Hetherington, E.D.; Choy, C.A.; Haddock, S.H.D.; Lapides, A.; Dunn, C.W. Characterizing the Secret Diets of Siphonophores (Cnidaria: Hydrozoa) Using DNA Metabarcoding. PLoS ONE 2022, 17, e0267761. [Google Scholar] [CrossRef]
  51. Van der Reis, A.L.; O’Rorke, R.; Olivar, M.P.; Beckley, L.E.; Jeffs, A.G. Insight into the Diet of Early Stages of Mesopelagic Fishes in the Indian Ocean Using DNA Metabarcoding. Deep Sea Res. Part II Top. Stud. Oceanogr. 2024, 218, 105426. [Google Scholar] [CrossRef]
  52. Russell, F.S.; Yonge, C.M. Advances in Marine Biology; Academic Press: Cambridge, MA, USA, 1969; Volume 7. [Google Scholar]
  53. Zavolokin, A.; Glebov, I.; Kosenok, N. Distribution, Quantitative Composition, and Feeding of Jellyfish in the Western Bering Sea in Summer and Fall. Russ. J. Mar. Biol. 2008, 34, 461–467. [Google Scholar] [CrossRef]
  54. Podeswa, Y.; Pakhomov, E.A. Feeding Ecology of Pelagic Decapods in the North Pacific Subtropical Gyre: Implications for Active Carbon Transport. Arthropoda Sel. 2015, 24, 317–334. [Google Scholar]
  55. Zwair, H. Perspective Chapter: Ostracoda; IntechOpen: London, UK, 2023. [Google Scholar] [CrossRef]
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Figure 1. Location of investigation station in the South Adriatic.
Figure 1. Location of investigation station in the South Adriatic.
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Figure 2. Average vertical temperature and salinity profiles down to 1200 m from measurements during research in July 2003.
Figure 2. Average vertical temperature and salinity profiles down to 1200 m from measurements during research in July 2003.
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Figure 3. Chlorophyll concentrations down to 200 m from measurements during research in July 2003.
Figure 3. Chlorophyll concentrations down to 200 m from measurements during research in July 2003.
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Figure 4. DVM of Archiconchoecia striata in the South Adriatic, July 2003. Units between ticks along the x-axis represent 60 ind. 100 m−3; arrows represent sampling dates.
Figure 4. DVM of Archiconchoecia striata in the South Adriatic, July 2003. Units between ticks along the x-axis represent 60 ind. 100 m−3; arrows represent sampling dates.
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Figure 5. DVM of Porroecia spinirostris in the South Adriatic, July 2003. Units between ticks along the x-axis represent 220 ind. 100 m−3; arrows represent sampling dates.
Figure 5. DVM of Porroecia spinirostris in the South Adriatic, July 2003. Units between ticks along the x-axis represent 220 ind. 100 m−3; arrows represent sampling dates.
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Figure 6. DVM of Porroecia porrecta porrecta in the South Adriatic, July 2003. Units between ticks along the x-axis represent 50 ind. 100 m−3; arrows represent sampling dates.
Figure 6. DVM of Porroecia porrecta porrecta in the South Adriatic, July 2003. Units between ticks along the x-axis represent 50 ind. 100 m−3; arrows represent sampling dates.
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Figure 7. DVM of Conchoecia magna in the South Adriatic, July 2003. Units between ticks along the x-axis represent 20 ind. 100 m−3; arrows represent sampling dates.
Figure 7. DVM of Conchoecia magna in the South Adriatic, July 2003. Units between ticks along the x-axis represent 20 ind. 100 m−3; arrows represent sampling dates.
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Figure 8. DVM of Mikroconchoecia curta in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
Figure 8. DVM of Mikroconchoecia curta in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
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Figure 9. DVM of Proceroecia procera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 100 ind. 100 m−3; arrows represent sampling dates.
Figure 9. DVM of Proceroecia procera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 100 ind. 100 m−3; arrows represent sampling dates.
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Figure 10. DVM of Proceroecia macroprocera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 75 ind. 100 m−3; arrows represent sampling dates.
Figure 10. DVM of Proceroecia macroprocera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 75 ind. 100 m−3; arrows represent sampling dates.
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Figure 11. DVM of Proceroecia microprocera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 42 ind. 100 m−3; arrows represent sampling dates.
Figure 11. DVM of Proceroecia microprocera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 42 ind. 100 m−3; arrows represent sampling dates.
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Figure 12. DVM of Discoconchoecia elegans in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
Figure 12. DVM of Discoconchoecia elegans in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
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Figure 13. DVM of Paraconchoecia spinifera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
Figure 13. DVM of Paraconchoecia spinifera in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
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Figure 14. DVM of Paramollicia rhynchena in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
Figure 14. DVM of Paramollicia rhynchena in the South Adriatic, July 2003. Units between ticks along the x-axis represent 30 ind. 100 m−3; arrows represent sampling dates.
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Figure 15. DVM of Metaconchoecia rotundata in the South Adriatic, July 2003. Units between ticks along the x-axis represent ind. 100 m−3; arrows represent sampling dates.
Figure 15. DVM of Metaconchoecia rotundata in the South Adriatic, July 2003. Units between ticks along the x-axis represent ind. 100 m−3; arrows represent sampling dates.
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Figure 16. The average population structure of the different ostracod species.
Figure 16. The average population structure of the different ostracod species.
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Figure 17. Weighted Mean Depth (WMD) of ostracod species in the South Adriatic, from the shallowest to the deepest habitat preferences.
Figure 17. Weighted Mean Depth (WMD) of ostracod species in the South Adriatic, from the shallowest to the deepest habitat preferences.
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Table 1. Temporal arrangement of zooplankton sampling in the South Adriatic Sea in July 2003, according to sunrise and sunset times.
Table 1. Temporal arrangement of zooplankton sampling in the South Adriatic Sea in July 2003, according to sunrise and sunset times.
DateSampling Period (h)Sunrise/Sunset (h)
22 July19:25–22:5005:29/20:19
23 July01:42–02:45, 06:25–9:30, 12:20–14:30, 15:45–17:40, 20:05–22:0505:30/20:18
24 July00:25–04:00, 06:00–9:00, 14:40–15:00, 18:30–22:2005:31/20:17
25 July01:15–02:30, 06:05–08:1505:32/20:16
27 July23:50–03:25, 05:45–09:00, 13:45–16:0505:34/20:14
28 July00:15–03:10, 05:50–08:00, 13:30–16:1505:35/20:13
Table 2. Comparison of the depth distribution of ostracods with other zooplankton groups—copepods [26], euphausiids [46], jellyfish [31] and siphonophores [32]—in the South Adriatic.
Table 2. Comparison of the depth distribution of ostracods with other zooplankton groups—copepods [26], euphausiids [46], jellyfish [31] and siphonophores [32]—in the South Adriatic.
GroupNight Depth DistributionDay Depth Distribution
Copepods0–50 m (surface feeding)
50–200 m (mid-water)		50–200 m
200–600 m (deeper refuge)
Euphausiids0–50 m (surface feeding)
50–200 m (some species)		200–600 m (deeper refuge, some species)
Siphonophores0–50 m (surface feeding)
50–200 m (some species)		50–200 m (mid-water)
Jellyfish0–800 m (surface feeding)200–1200 (extensive migrators, deep-dwelling species)
Ostracods
(migratory)		0–50 m (juveniles near surface)
50–200 m (some species)		50–200 m (some species, more variable migration)
Ostracods
(non-migratory)		600–1200 m (non-migratory,
deep-dwelling species)		600–1200 m (non-migratory, deep-dwelling species)
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Brautović, I.; Gangai Zovko, B.; Onofri, I. Vertical Migration and Habitat Preference of Planktonic Ostracods (Crustacea) in the Deep Adriatic Sea. Diversity 2025, 17, 256. https://doi.org/10.3390/d17040256

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Brautović I, Gangai Zovko B, Onofri I. Vertical Migration and Habitat Preference of Planktonic Ostracods (Crustacea) in the Deep Adriatic Sea. Diversity. 2025; 17(4):256. https://doi.org/10.3390/d17040256

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Brautović, Igor, Barbara Gangai Zovko, and Ivona Onofri. 2025. "Vertical Migration and Habitat Preference of Planktonic Ostracods (Crustacea) in the Deep Adriatic Sea" Diversity 17, no. 4: 256. https://doi.org/10.3390/d17040256

APA Style

Brautović, I., Gangai Zovko, B., & Onofri, I. (2025). Vertical Migration and Habitat Preference of Planktonic Ostracods (Crustacea) in the Deep Adriatic Sea. Diversity, 17(4), 256. https://doi.org/10.3390/d17040256

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