Distribution Of Zooplankton Research Articles

Daily vertical distribution of zooplankton in two oligo-mesotrophic north Patagonian lakes (39° S, Chile).

The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet radiation and/or fish predation. However there is no information on this topic in Chilean North Patagonian lakes up to date. Therefore, this study deals with a first characterization of plankton crustacean daily vertical migration in two temperate, oligotrophic lakes (Villarrica and Panguipulli lakes, 39°S) in Southern Chile. Zooplankton were collected at different depths intervals (0-10m, 10-20 m, 20-30m, 30-40m) at early morning, middle day, evening and night in the studied site. The results revealed that zooplankton species (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus, and Tropocyclops prasinus) are abundant in surface zones at night, early morning and evening, whereas at middle day the zooplankton abundances are high at deep zones. The results agree with observations for Argentinean and North American lakes where these daily migration patterns in crustacean zooplankton species were reported due mainly natural ultraviolet radiation exposure, whereas for northern hemisphere lakes the vertical migration is due to combined effect of natural ultraviolet radiation and fish predation exposure.

Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019

Acoustic technology, as an important investigation method for fishery resources, has been widely used in zooplankton surveys. Since the Kuroshio–Oyashio confluence region has an extensive distribution of zooplankton, describing and analyzing the characteristic of the zooplankton sound scattering layer (SSL) in this area is essential for marine ecology research. To understand its spatial–temporal distribution, acoustic data of the Kuroshio–Oyashio confluence region at the Northwest Pacific Ocean, obtained by a Simrad EK80 broadband scientific echosounder in 2019, were used on board the research vessel (RV) Songhang. After noise removal, the volume backscattering strength (SV) was measured to plot the broadband scattering spectrogram of each water layer and to exhibit zooplankton distribution. The results show that the main sound scattering within 0–200 m originate from the zooplankton, and the SV of each layer increases with the rise of the transducer frequency. The magnitude of SV was closely synchronized with the solar altitude angle, which gets smaller when the angle is positive, then larger when the angle is negative. It means that the SSL has a diel vertical migration (DVM) behavior with the variation of solar height. Meanwhile, scattering strength was positively correlated with temperature in the vertical direction and showed a maximum of −54.31 dB at 20–40 m under the influence of the thermocline. The Kuroshio and Oyashio currents had an obvious influence on the scattering strengths in this study, indicating a low value when next to the Oyashio side and a high value on the Kuroshio side. The scattering strength near the warm vortex center was higher than that at the vortex edge. The results of this study could provide references for a long-term study on ecological environment variation and its impacts on zooplankton distribution.

Environmental effects on Calanus finmarchicus abundance and depth distribution in the Barents Sea

Abstract The vertical migrations performed by zooplankton at daily and seasonal scales are important for marine ecosystem dynamics and biogeochemical cycles. We analysed associations between seasonal variation in abundance and depth distribution of the copepod Calanus finmarchicus and temperature and predation pressure from visual (capelin and herring) and non-visual (ctenophores) predators, using data from a > 30-year survey in the southwestern Barents Sea. Calanus finmarchicus abundances were significantly reduced in upper waters with increased capelin biomass, possibly due to a combination of predation mortality and active avoidance of the upper layer. The weighted mean depth of Calanus finmarchicus tended to become shallower, and abundances in deeper layers lower, with a high probability of ctenophore occurrence, possibly due to a predation effect at depth. Temperature influenced the seasonal timing of Calanus finmarchicus, but appeared less important for depth distribution. This study illustrates how climate-driven changes in the physical and biological environment can influence the seasonal and vertical distribution of zooplankton, which has major implications for the flow of energy and nutrients in marine ecosystems.

Comprehensive Insight into Lake Nasser Environment: Water Quality and Biotic Communities—A Case Study before Operating the Renaissance Dam

This study focused on the monitoring and assessment of aquatic ecosystem functioning based on the abiotic and biotic features of Lake Nasser in the post-flood and pre-flood periods as the last ones before water storing behind the Grand Ethiopian Renaissance Dam. The physicochemical parameters, distribution and structure of biotic communities, including bacteria, phytoplankton, zooplankton, macrophytes, epiphytes and fish were analyzed at 15 sites. The values of most parameters (primarily temperature, total suspended solids, pH, orthophosphates, carbonates, sulphates and some cations) were higher in the pre-flood period, whereas higher values of conductivity, total dissolved solids, total solids, nitrites, nitrates, chemical oxygen demand, bicarbonates and chlorophyll a were recorded in the post-flood period. Cyanobacteria-dominated phytoplankton and total coliform bacteria were more abundant in the pre-flood period, and especially at sites 10–15, whereas higher abundances of zooplankton were recorded in the post-flood period. All these changes in parameters were significantly differentiated, and only the concentrations of dissolved oxygen, biochemical oxygen demand, ammonium and silicates were at similar level in both periods. The study also indicated that environmental factors had affected the macrophyte distribution and the adaptation of the invasive species Myriophyllum spicatum to thrive under different environmental factors in the lake. Besides, macrophytes provided the habitat to other aquatic organisms, especially epiphytes, and also helped maintaining the good water quality, nutrient cycling and stabilizing rivers’ and lakes’ banks. Generally, these conditions were rather favorable for biological processes and fish production.

Zooplankton and meiobenthos diversity at the intertidal sandy shores of Jizan and Farasan coastal areas of Red Sea.

Distinctive studies were conducted for the identification of meiobenthos and zooplankton at Farasan Islands and Jizan sandy shores. The present work compares the meiobenthos and zooplankton communities at Alhsas sandy shore at Farasan Islands and As-Suways sandy shore at Jizan. Population density, species richness and Shannon-Weiner diversity index were determined for meiobenthos and zooplankton inhabiting both the studied sites. Water criteria; surface water temperature, pH and conductivity were determined for each investigated site. Eleven zooplankton species were defined at Alhsas sandy shore Farasan, nine species were identified at the littoral zone at As-Suways sandy shore, Jizan. Ten meiobenthos species were defined at Alhsas site, Farasan. Only eight meiobenthos species were defined at the intertidal zone of As-Suways site, Jizan. The results were discussed to highlight the effect of water criteria on the spatial distribution of zooplankton and meiobenthos at the investigated sites.

Distribution of zooplankton in Lake Aslikul (South Urals, Russian Federation)

Fauna of aquatic invertebrates from various biotopes of the mineralized Lake Aslikul of the Asly-Kul natural park was studied. Lake Aslikul is the largest body of water in the Republic of Bashkortostan, one of the largest lakes in the Middle Volga region. Crustaceans dominated (67%) in the zooplankton in terms of the number of species. Typical eurythermal species such as Keratella quadrata (Müller, 1786), Eudiaptomus gracilis (Sars, 1863), and E. graciloides (Lilljeborg, 1888) were recorded in the zooplankton, that thrived throughout the summer and autumn. Typical brackish-water species were encountered, for example, Hemidiaptomus ignatovi Sars, 1903. A specific community of zooplankters was formed in different biotopes of the lake: Daphnia galeata and Bosmina (E.) cf longispina (Leydig, 1860) were found in the pelagial; Pleuroxus aduncus (Jurne, 1820) and Eucyclops macruroides (Lilljborg, 1901) in macrophyte beds. The species inhabiting the deep-water part of the water body may be considered as indicators of oligo- and mesotrophic waters (Diaphanasoma brachyurum (Lievin, 1848), Bosmina (Eubosmina) cf. longispina Ley dig, 1860, and Bilpalpus hudsoni (Imhof, 1891)). Two rotifer species Rotaria rotatoria (Pallas, 1766) and Lecane (s. Str.) luna (Müller, 1776) were found only in macrophyte beds indicating mesotrophic conditions. In June and September 2010, the abundance of zooplankton throughout the entire lake varied from 1200 to 196 (on average, 484.3 ± 166.4) thousand individuals/m³, and the biomass from 13.6 to 0.9 (on average, 8.5 ± 2.5) g/m³. Crustaceans (78%) have also made the main contribution to the formation of quantitative indicators of zooplankton in various biotopes of the lake.

Effects of a Submesoscale Oceanographic Filament on Zooplankton Dynamics in the Arctic Marginal Ice Zone

Submesoscale structures, characterized by intense vertical and horizontal velocities, potentially play a crucial role in oceanographic dynamics and pelagic fluxes. Due to their small spatial scale and short temporal persistence, conditions for in situ measurements are challenging and thus the role of such structures for zooplankton distribution is still unclear. During RV Polarstern expedition PS107 to Arctic Fram Strait in July/August 2017, a submesoscale filament was detected, which initiated an ad hoc oceanographic and biological sampling campaign. To determine zooplankton taxonomic composition, horizontal and vertical distribution, abundance and biomass, vertical MultiNet hauls (depth intervals: 300–200–100–50–10–0 m) were taken at four stations across the filament. Zooplankton data were evaluated in context with the physical-oceanographic observations of the filament to assess submesoscale physical-biological interactions. Our data show that submesoscale features considerably impact zooplankton dynamics. While structuring the pelagial with distinct zooplankton communities in a vertical as well as horizontal dimension, they accumulate abundance and biomass of epipelagic species at the site of convergence. Further, high-velocity jets associated with such dynamics are possibly of major importance for species allocation and biological connectivity, accelerating for instance processes such as the ‘Atlantification’ of the Arctic. Thus, submesoscale features affect the surrounding ecosystem in multiple ways with consequences for higher trophic levels and biogeochemical cycles.

Springtime renewal of zooplankton populations in the Chukchi Sea

Although considerable work has been done in the Chukchi Sea during summer, much less has been done during other seasons. This has limited our ability to fully understand seasonal cycles and transformations of the Chukchi Sea zooplankton, particularly the key copepod species Calanus glacialis. Abundance and distributions of large zooplankton and of all life stages of C. glacialis in the northeastern Chukchi Sea during May-June 2014 are described. Three main zooplankton communities are identified; “arctic oceanic” along the Chukchi slope associated with off-shelf water masses; Chukchi Sea “overwintering” associated with cold winter water in the northern part of the study area; and Chukchi Sea “spring” associated with early season summer water in the southern portion of the study area. The overwintering and spring communities were distinguished by the near total absence of younger copepodid (CI-CIII) C. glacialis stages and meroplankton in the overwintering community while older (CV-adult) C. glacialis, amphipods, and chaetognaths were present in both. The distributions of the communities followed the major circulation pathways in the northeastern Chukchi Sea. Water and plankton flooding in from the northern Bering Sea was filling the Chukchi Sea and replenishing the zooplankton communities as the remnants of the overwintering community was being advected northwards and into the Canadian Basin. A conceptual model of the seasonal evolution of C. glacialis populations in the Chukchi Sea, based on the interaction of C. glacialis phenology and advective drivers, enfolds both these spring observations and summer observations from numerous previous studies. Because the flushing time of the Chukchi Sea is shorter than the C. glacialis generation time, the copepod is unable to establish an endemic population in the Chukchi Sea, hence the population there must be renewed annually from the northern Bering Sea.

ОСОБЕННОСТИ СТРУКТУРЫ И ДИНАМИКИ ЗООПЛАНКТОНА ОЗЕРА НЕРО (ЯРОСЛАВСКАЯ ОБЛАСТЬ) В ПЕРИОД ПОТЕПЛЕНИЯ КЛИМАТА

Data on the abundance, biomass, and composition of the dominant complex of zooplankton in the shallow hypertrophic lake Nero (Yaroslavl region) from 2007 to 2017 are present. The spatiotemporal distribution of zooplankton is analyze. The high zooplankton species richness is characteristic of Lake Nero (>100 species in the general list and up to 22–27 species in the sample). 2007 to 2011, a low amount of zooplankton was noted (<37.9 thous. ind./m3 and 0.15 g/m3), with a relatively high proportion of copepods (up to 83%). Since 2012, the abundance of planktonic animals has increased (313 thous. ind./m3 and 1.20 g/m3). In 2007–2017 the composition of dominants remained close to that in previous years; small crustaceans (Bosmina longirostris, Chydorus sphaericus, Mesocyclops leuckarti), rotifers (genera Asplanchna, Brachionus, Keratella, Trichocerca and Anuraeopsis) dominated the zooplankton community. Rotifer-dominated communities (with a high abundance of thermophilic Brachionus diversicornis) formed during abnormally warm summers. Two species groups are determined: the first dominates in spring, early summer, and autumn, and the second in the second half of summer. The high abundance of zooplankton (>5 mil. ind./m3 and 10 g/m3) is in the thickets of macrophytes, which is 8–9 times higher than in the open littoral and pelagic zones. In the western littoral zone, the low abundance of zooplankton (<1 g/m3) may be associated with local pollution, high concentration of chlorophyll a, high phytoplankton biomass, represented by low food cyanobacteria. The center part and the adjacent open littoral zone differed in composition and abundance of dominant species from the southern bays occupied by macrophytes. The trophic status of the lake ecosystem in terms of zooplankton is hypertrophic since the 1980s. The abundance, composition and structure of the community in the long-term aspect are stable with interannual fluctuations common for a high-trophic shallow lake.

Multi‐scale biodiversity analyses identify the importance of continental watersheds in shaping lake zooplankton biogeography

AbstractAimWe examined variation in crustacean zooplankton composition and diversity across Canada, the most lake‐rich country in the world. In addition to α‐diversity patterns, we explore mechanisms behind β‐diversity spatial variation, using taxonomic and functional metrics. Our goal was to explore geographical gradients and related mechanisms shaping zooplankton distribution across different spatial scales.LocationCanada.TaxonCrustacean zooplankton.MethodsPelagic zooplankton was sampled in and characterized for 624 lakes across Canada, spanning 12 ecozones (defined by climatic, vegetation and geological differences) or 6 continental drainage basins as part of the NSERC Canadian Lake Pulse Network project. We compared taxon and trait distributions, as well as spatial (longitudinal and latitudinal) patterns of community composition and diversity. We computed taxonomic and functional spatial β‐diversity indices, decomposing these into taxon replacement and richness differences. Finally, species (or traits) and lake uniqueness (contributions) to β‐diversity (SCBD and LCBD) were estimated by ecozone and continental basin.ResultsIn all, 90 crustacean zooplankton species were identified across the country. Differences in zooplankton taxonomic and functional composition were more distinct when considered by continental basin than by ecozone. α‐diversity varied greatly across space, with greatest diversity in eastern Canada. β‐diversity was greatest when based on taxonomy and was driven by richness differences across all spatial and biodiversity dimensions.Main conclusionsStructuring factors influencing zooplankton taxon and trait assemblages vary across spatial scales, being more important at the broadest scale considering continental hydrodynamics. Our results point to the combined effects of physical barriers to longitudinal dispersal and climate change in shaping zooplankton taxonomic and functional biogeography across Canadian lakes.

Composition, density and spatial distribution of zooplankton on wet season (June-August) in Inner Ambon Bay

Inner Ambon Bay is part of Ambon Bay, it is semi closed area and is a small pelagic fish fishing ground, especially anchovy. The anchovy is zooplankton predator therefore existence of anchovy is affected by abundance of zooplankton. The aim of the research are to know composition, density and spatial distribution of the zooplankton during wet season (June to August). Data of zooplankton composition were obtained from sampling by using plankton net at 10 observation stations, meanwhile, data of densities were collected using scientific hydroacoustic system, BioSonic DTX, on six parallel transect lines and one cross-parallel transect line. Geostatistical analyses technique was used to describe horizontal distributions of zooplankton and vertical distributions were plot in the graphs. The result shows that zooplankton community dominated by Copepod and meroplankton. Highest density was found on August (9393/m2 ), while lowest density was on June (903 ind./m2 ). Vertical distribution of zooplankton shows that highest density was found near surface and decrease to deeper water coloumn. On the horizontal distribution, lower densities (0 – 400 ind./m2 ) occupy wider space, they evenly distributed in western, middle (north to south) and east, on the contrary, higher densities (3000- 5000 ind./m2 ) occupy smaller space i.e in the south-west, south and east to north-east of Inner Ambon Bay

Dense mesopelagic sound scattering layer and vertical segregation of pelagic organisms at the Arctic-Atlantic gateway during the midnight sun

Changes in vertical and spatial distributions of zooplankton and small pelagic fish impact the biological carbon pump and the distribution of larger piscivorous fish and marine mammal species. However, their distribution and abundance remain poorly documented at high latitudes because of the difficulties inherent to sampling relatively fast-moving organisms in ice-covered waters. This study documents the under-ice distribution of epipelagic and mesopelagic organisms at the Arctic-Atlantic gateway in spring, during the midnight sun period, using ice-tethered and ship-based echosounders. An epipelagic surface scattering layer composed of copepods consistently occupied the top 60 m and was associated with cold polar surface water (mean temperature of −1.5 °C). A mesopelagic deep scattering layer (DSL), partly composed of fish, persisted between 280 m and 600 m and was associated with modified Atlantic water. Backscattering strength within the DSL was higher than previously reported in the Arctic and north Atlantic, and increased by two orders of magnitude over the continental slope where one of the Atlantic water pathways enters the Arctic Ocean. Mesopelagic organisms did not perform diel vertical migrations. The consistent segregation between copepods at the surface and their predators at mesopelagic depths suggests limited predator–prey interactions during the midnight sun period, even under the ice cover. Predation on copepods by mesopelagic organisms, including fish, could thus be limited to very pulsed events during the seasonal vertical migration of copepods to and from overwintering depths. This suggests that the arctic mesopelagic food web may be decoupled from secondary production in the epipelagic layer throughout most of the year.

Zooplankton β diversity dynamics and metacommunity structure depend on spatial and temporal scales in a Neotropical floodplain

Abstract Both β diversity and metacommunity structure vary in time and space. It is necessary to examine different scales, especially in the face of extreme hydrological conditions. We investigated seasonal variation in β diversity and Elements of Metacommunity Structure [EMS] of zooplankton during four years (two years of prolonged drought and two years with extreme flood events) and at two spatial scales (sub‐basins and floodplain; smaller and larger spatial scale, respectively). We sampled 29 lakes quarterly during four years in the Upper Paraná River floodplain, Brazil. We estimated the replacement component of β diversity using the Jaccard dissimilarity index. We also used EMS to determine the metacommunity pattern of zooplankton distribution in each period and spatial scale. The flood peak observed in the snapshot sampling drove the homogenization of zooplanktonic assemblages. However, β diversity was not reduced in the two years with extreme flood events compared to the period of prolonged drought at either of the spatial scales (floodplain and sub‐basins), except for a single sub‐basin. This finding shows the importance of longer‐term ecological studies to better capture the dynamics of the zooplanktonic metacommunity. Regardless of the hydrological period and spatial scale zooplanktonic metacommunity structure remained practically constant throughout the four years, with a predominance of species range turnover (Clementsian). At the smallest spatial scale (sub‐basins), we found quasi‐structural patterns (quasi‐Clementsian and quasi‐Gleasonian). The predominance of the Clementsian pattern suggests that the associations of zooplankton species in the floodplain responded similarly to the environmental gradient and that the responses differed among species groups. Over time, the smaller spatial scale (sub‐basin) better represents the dynamics of β diversity than the larger spatial scale (floodplain), and better represents the structure of the zooplankton metacommunity. However, we emphasize the need for further studies to consider different biological groups and larger spatial scale over time to maximize the understanding of aquatic metacommunities dynamics. ​

Composition, density and spatial distribution of zooplankton on 1st transition season (March to May) in Inner Ambon Bay Waters, Indonesia

Inner Ambon Bay is part of Ambon Bay that covered an area about 11.03 km2. It is semi-closed and become a small pelagic fish fishing ground, especially anchovy. The anchovy is a zooplankton predator, hence, the abundance of anchovy is dependent on the abundance of zooplankton. The research aims to analyze the composition, density, and spatial distribution of the zooplankton during the 1st transition season (March to May). Data of zooplankton composition were attained from sampling by using plankton net at ten observation stations, meanwhile, data of densities were obtained using a scientific hydroacoustic system on six parallel transect lines and one cross-parallel transect line. The study shows that the zooplankton community is dominated by Copepod and meroplankton. The highest density was found in March, while the lowest density was in April. Vertical distribution of zooplankton shows that the highest density was found near the surface (0-4 m) and decrease to a deeper water column. On the horizontal distribution, lower densities (0 – 400 ind./m2) occupy a wider area, they are evenly distributed in western, middle, and eastern, in the contrary, higher densities (3,000-4,000 ind./m2) occupy smaller space viz. in the southwest and east of Inner Ambon Bay.

Effects of terrestrial inputs and seawater intrusion on zooplankton community structure in Daya Bay, South China Sea

Daya Bay is a eutrophic coastal region with dynamic physico-chemical conditions influenced by terrestrial inputs and seawater intrusion. Zooplankton is a crucial trophic intermediary for energy transfer and fishery resources. In this study, we assessed the distribution and composition of zooplankton in Daya Bay during summer and winter of 2015. We found that zooplankton diversity was the lowest and dominated by small copepods (Acartia spp. and Paracalanus spp.) and gelatinous Oikopleura spp. under terrestrial inputs in the Dan'ao River estuary and Aotou barbour. The highest zooplankton diversity was observed at the bay mouth that influenced by salty intruded seawater, and the dominant oceanic species (such as Euchaeta concinna and Subeucalanus subcrassus invaded into the top of the bay in winter. The dominant species in the estuary shift from Penilia avirostris to Acartia spp. compared with historical researches, indicating the effect of human activities on the succession of dominant species.

Zooplankton and profundal macroinvertebrate responses to hypolimnetic oxygenation in North Twin Lake, Washington

Cross BK, Taylor TN, Moore BC, Lanouette BP. 2021. Zooplankton and profundal macroinvertebrate responses to hypolimnetic oxygenation in North Twin Lake, Washington. Lake Reserv Manage. 37:275–288. Hypolimnetic oxygenation (HO) has been used to address lake eutrophication and fish habitat limitations, but details on zooplankton and profundal macroinvertebrate community responses are required to fully understand the trophic linkages and impacts. Compared to adjacent South Twin Lake (an unoxygenated reference), zooplankton and profundal macroinvertebrate densities and distributions were altered by HO in North Twin Lake. Overall, temporal trends in zooplankton density were similar between lakes despite oxygenation, suggesting annual and seasonal influences remained a primary factor affecting their density trends. During the day, Chaoborus density was significantly greater in the water column of unoxygenated South Twin Lake compared to oxygenated North Twin Lake (P < 0.0001) as the oxygenated hypolimnion no longer provided refuge from fish predation. Daphnia and copepod densities were greater in North Twin Lake during oxygenation compared to South Twin Lake (P = 0.0011 and P = 0.0005), which may reflect increases in zooplankton habitat availability and reduced predation from Chaoborus in response to HO. With higher levels of dissolved oxygen near the sediment–water interface in North Twin Lake, larval Chaoborus and chironomid densities in the benthic sediments were significantly higher compared to South Twin Lake (P < 0.0001 in both cases). Vertical distribution of zooplankton likely reflected some balance between habitat availability, energetic costs, and predation risk. Lakes with different fish species assemblages may not respond similarly, so managers should reflect on lake similarities between North Twin Lake and systems they manage to understand potential effects of HO and how those effects align with management objectives.

The distribution of zooplankton and the influencing environmental factors in the South Yellow Sea in the summer

Zooplankton were sampled using large plankton net (LPN) (mesh size: 505 μm) and medium plankton net (MPN) (160 μm) in the summer of 2008. 96 and 87 zooplankton species were identified in LPN and MPN, respectively; Calanus sinicus, Aidanosagitta crassa, and Oithona plumifera were common dominant species between the two nets; other dominant species in MPN, such as O. similis, were rare in LPN. The average abundance was 228.99 ± 130.06 ind./m3 and 2835.05 ± 3356.37 ind./m3 in LPN and MPN, respectively. The average biomass was 194.56 ± 130.06 mg/m3 and 216.45 ± 131.89 mg/m3. The diversity indices were also higher in MPN. Correlation analysis indicated that the abundance was negatively correlated with sea bottom temperature, which meant that zooplankton species tended to be clustered in the Yellow Sea Cold Water Mass. The diversity indices were negatively correlated with salinity, which indicated that diversity was higher in sea areas that were affected by Changjiang River Diluted Water.

Distribution of rorquals and Atlantic cod in relation to their prey in the Norwegian high Arctic

Recent warming in the Barents Sea has led to changes in the spatial distribution of both zooplankton and fish, with boreal communities expanding northwards. A similar northward expansion has been observed in several rorqual species that migrate into northern waters to take advantage of high summer productivity, hence feeding opportunities. Based on ecosystem surveys conducted during August–September in 2014–2017, we investigated the spatial associations among the three rorqual species of blue, fin, and common minke whales, the predatory fish Atlantic cod, and their main prey groups (zooplankton, 0-group fish, Atlantic cod, and capelin) in Arctic Ocean waters to the west and north of Svalbard. During the surveys, whale sightings were recorded by dedicated whale observers on the bridge of the vessel, whereas the distribution and abundance of cod and prey species were assessed using trawling and acoustic methods. Based on existing knowledge on the dive habits of these rorquals, we divided our analyses into two depth regions: the upper 200 m of the water column and waters below 200 m. Since humpback whales were absent in the area in 2016 and 2017, they were not included in the subsequent analyses of spatial association. No association or spatial overlap between fin and blue whales and any of the prey species investigated was found, while associations and overlaps were found between minke whales and zooplankton/0-group fish in the upper 200 m and between minke whales and Atlantic cod at depths below 200 m. A prey detection range of more than 10 km was suggested for minke whales in the upper water layers.

The distributional pattern of zooplankton community in beratan lake, bali

Zooplankton is an important component in water ecosystem that has a distribution in spatial and time scale. The distribution and diversity of zooplankton as one biological indicator of quality of the water way. This study was aimed at looking at the description of the distributional pattern and the abundance of zooplankton and Beratan Lake. Five sampling stations were determines based on the deeps of the lake using the field survey method, i.e., LB 1, LB 2, LB 3, LB 4 and LB 5. The zooplankton sample was taken from each stations by using Chaoborus net NXX 10 (the eye of the net size was 132 µ, then the zooplankton was preserved with 4% formalin solution. After being identified, there was five species, 4 Cladocera species and 8 rotifera species. The highest of abundance for copepod group was Thermocyclops. Diaphanosoma was Cladocera group which was mostly found. Conochilus unicornis was the most dominant rotifer.

Distribution of Ichthyoplankton in Relation to Specifics of Hydrological Regime off the Crimean coast (the Black Sea) in the Spring–Summer Season 2017

The paper presents characteristics of the species composition, spatial distribution, and trophic interactions of ichthyoplankton and zooplankton in the spring–summer period 2017 dependent on intensity of the warming-up of the upper sea layer against the background of transition in a system of the surface currents from the winter-to summer-type of the circulation. In April–May, successful spawning of temperate-water fish species was prolonged due to low values of the sea surface temperature (8–9°С) on the shelf of Crimean Peninsula between Kerch Strait and the cape Sarych. The maximum abundance of Sprattus sprattus eggs was 162.8 egg/m2 and larvae –116 ind/m2. Warm-water species occurred only in the western sector from Herakleian Peninsula to the Cape Tarkhankut, where the water temperature was at its maximum and peaked at 14–15°С. In June–July the delayed summer hydrological season hampered the warming-up of the upper quasi-homogenous layer, which thickness varied from 1–5 to 10–15 m. Notwithstanding the large number of species in the ichthyoplankton, maximum abundance did not exceed 50 egg/m2 and 14 ind/m2 for larvae. The proportion of larvae of temperate-water fish species averaged 32% and reached 40% in deep water areas. Juvenile stages of copepods of the cold-water complex were dominant in the larval fish diet both in the spring and summer seasons.