Distribution Of Zooplankton Research Articles

Loss of pelagic fish and zooplankton density associated with subglacial upwelling in high Arctic estuaries may be mitigated by benthic habitat expansion following tidewater glacier retreat

Glacier fronts are hotspots of pelagic productivity due to upwelling of nutrient-rich water. As tidewater glaciers retreat into land, this subglacial circulation will disappear and sedimentation from terrestrial runoff will increase, leading to a decrease in pelagic productivity with a decline in the abundance of fish and zooplankton. We used Billefjorden, a high Arctic fjord with a glacier recently transitioned from sea- to land-terminating as a case study to identify spatial differences and small-scale environmental drivers of density and vertical distribution of fish and zooplankton along a gradient of glacier retreat (directly in front of the land-terminating glacier front, a river bay with terrestrial input from land-terminating glaciers further inland and a location with minimal glacial input). We developed a sustainable and efficient protocol to safely sample the glacier front and shallow coastal areas using hydroacoustics and a remote autonomous vehicle combined with oceanographic measurements and baited remote cameras. Over two years, pelagic density was lowest at the now land-terminating glacier front and highest at the site with lowest terrestrial input. Temperature, depth and turbidity explained less than 8% of the variation each.

Winter distribution of zooplankton and ichthyoplankton assemblages in the North Sea and the English Channel.

Although zooplankton were extensively studied in the North Sea, knowledge about winter zooplankton assemblages is still scarce, despite potential influence of zooplankton overwintering stocks on seasonal plankton succession and productivity. Furthermore, several economically and ecologically important fish species reproduce during winter contributing to the zooplankton community as passive members (eggs) or predators (larvae). To elucidate on winter zooplankton distribution, abundance and composition in the Southern North Sea and Eastern English Channel, we defined assemblages based on mesozoo- and ichthyoplankton data sampled between January and February 2008 using fuzzy-clustering and indicator species. Mesozoo- and ichthyoplankton (eggs+larvae) were integrated in a common analysis by using a spatial grid adapted to the datasets and defined by means of a geostatistical method developed in agronomics. Potential environmental drivers of assemblage distribution were evaluated by means of GLMM and comparison with data from 2022 facilitated insight about the inter-annual representativeness of the assemblages. Five zooplankton assemblages were found varying with regard to total zooplankton abundance, dominant and indicator taxa. Spatial variability of abiotic (dissolved nutrients, salinity, depth, temperature, organic matter in suspension, chlorophyll a), biotic variables (phyto- and microplankton composition), water masses and fish spawning grounds were revealed as potential drivers of assemblage distribution. Assemblages off the Rhine-Scheldt estuary and in the German Bight harbored the biggest zooplankton overwintering stocks that might influence the grazing pressure on phytoplankton spring production. Assemblages off the Rhine-Scheldt estuary and covering the English Channel and the Southern Bight were found to be of high importance for herring and plaice larvae. Although further analyses suggested inter-annual representativeness of the assemblages found (2008 vs 2022), the assessment of further years would be necessary to account for potential inter-annual variability. Future studies could profit from the assessment of microzooplankton facilitating insight in fish larvae feeding potential and zooplankton overwintering strategies.

Latitudinal variation in zooplankton over the Emperor Seamounts (34°–44° N, 170°–171° E) during the summer of 2019

During a research expedition to the Northwest Pacific between July 13 and August 11, 2019, we collected oceanic zooplankton samples over the Emperor Seamounts (Koko, Jingu, Nintoku, and Suiko guyots). We analyzed the horizontal and vertical distributions of abundance and biomass and also the structure of the zooplankton in the highly productive but poorly studied ocean waters between 34° and 44° N. The zooplankton was represented by four genera of amphipods, seven genera of pteropods, 39 genera of copepods, and larvae of benthic invertebrates and fish. The abundance and biomass of zooplankton increased towards higher latitudes along the series Koko < Jingu < Nintoku < Suiko guyots. The highest index of diversity was recorded over the Koko and Jingu guyots; the highest species richness occurred over the Jingu and Nintoku guyots. Small-sized copepods, appendicularians, chaetognaths, euphausiids, and fish eggs and larvae concentrated in the epipelagic; large copepods and ostracods concentrated in the mesopelagic. We identified three types of zooplankton assemblages: a Subtropical assemblage between 34°–35° N characterized by tropical/subtropical forms; a Transition assemblage characterized by subtropical, subarctic, and widespread species between 38°–41° N; and a Subarctic assemblage characterized by subarctic and widespread species between 43°–44° N. The spatial distribution of zooplankton was a function of environmental variables such as surface salinity, temperature at 200-m, and, to a certain extent, by surface Chl-a concentrations.

Spatial and seasonal variation in zooplankton dynamics in Parangipettai coastal waters Southeast coast of India

The distribution and composition of zooplankton are influenced by a combination of physico-chemical and biological processes, which in turn have effects on the entire ecosystem. In this study, the influence of environmental factors on zooplankton diversity in mangrove-estuarine coastal waters of Parangipettai, southeast coast of India, was investigated. Water samples were collected for a period of four years from January 2014 to December 2017. Totally, 145 species of zooplankton were recorded with highest belonging to the Arthropoda (63.21%) followed by Protozoa (10.53%), Cnidaria (7.95%), Urochordata (6.03%), Chordata (2.92%), Chaetognatha (2.62%), Mollusca (2.42%), Echinodermata (1.14%), Annelida (1.05%), Brachiopoda (1.01%), Ctenophora (0.57%) and Phoronida (0.55%). The findings of cluster, MDS, Factor analysis and CCA showed that variations in nutrient concentration may significantly alter the biotic community of zooplankton species. Furthermore, site score confirmed the effect of environmental conditions on zooplankton distribution. The result of TRIX showed the dry seasons are classified as scarcely eutrophied whereas wet seasons as moderately eutrophied. The findings of this study offer enhanced insight into how physico-chemical factors interact and vary over space and time, which is crucial for evaluating the effects of climate change on ecosystem services mediated by zooplankton.

Zooplankton vertical stratification in the East-pacific and Indian sectors of the Southern Ocean

IntroductionIn the Southern Ocean, the large-scale distribution of zooplankton, including their abundance and community composition from the epipelagic to the upper bathypelagic layers, remains poorly understood. This gap in knowledge limits our comprehension of their ecological and biogeochemical roles.MethodsTo better understand their community structure, depth-stratified zooplankton samples were collected from 0 to 1500 m during four summers in the East-Pacific and Indian sectors of the Southern Ocean. In addition, analysis of environmental drivers including temperature, salinity, dissolved oxygen, and chlorophyll a concentration, as well as water masses was conducted.ResultsOur study indicates that zooplankton diversity may be similar between the two sectors, while zooplankton abundance was higher in the East-Pacific sector during different sampling months and years. Moreover, zooplankton abundance decreased with depth in both sectors. Based on cluster analysis, zooplankton communities were generally divided by either the epipelagic or the deeper layers’ communities. In both sectors, the epipelagic layer was dominated by cyclopoid copepods, such as Oithona similis and Oncaea curvata, as well as calanoid copepods including Calanoides acutus, Rhincalanus gigas, and Ctenocalanus citer, while copepods and other taxa including Chaetognatha, Amphipoda, and Ostracoda, were important contributors to the deep layer communities.DiscussionOur analysis revealed that water masses, combined with their physical characteristics such as specific temperature and salinity ranges and depth, along with biological factors such as chlorophyll a concentration, might be the most important drivers for structuring zooplankton communities from epipelagic to upper bathypelagic layer.

Hydro-morphology and water quality jointly shape the structure and network stability of the plankton community in multi-tributary river basins

Revealing the spatial variation in phytoplankton and zooplankton communities, along with their responses to water flow, climate, and water quality from headwaters to downstream, is crucial for grasping their evolutionary dynamics and crafting ecological preservation strategies. Here, the spatial distribution, assembly processes, and stability changes of phytoplankton and zooplankton in the tributaries from headwaters to downstream reaches of the Danjiang River and the upper Hanjiang River (China) were analyzed using environmental DNA (eDNA) technology. Geographic factors accounted for over 60% of the variation in the distribution of phytoplankton and zooplankton, although environmental factors also played a significant role. From upstream to downstream, the proportion of phytoplankton Bacillariophyta decreased from 37.12% to 33.07% in March and from 27.68% to 25.36% in August. Euglenophyta decreased from 1.04% to 0.53% in March and 10.48% to 2.16% in August. The proportion of zooplankton Ciliophora increased from 67.17% to 85.04%, while Amoebozoa decreased by approximately 9.83% in August. Phytoplankton and zooplankton richness initially increased, then declined from upstream to downstream. The assembly of zooplankton and phytoplankton communities was mainly driven by deterministic processes, with values ranging from 0.2 to 0.5. Furthermore, the upstream community showed a stronger dominance of deterministic processes, while the mainstream community exhibited weaker determinism than the tributaries. In both March and August, zooplankton were more influenced by deterministic processes than phytoplankton. From upstream to downstream, the stability and complexity of phytoplankton and zooplankton networks decreased, significantly influenced by river width, flow velocity, agricultural land proportion, and nutrient concentration. Maintaining diverse phytoplankton was crucial for sustaining zooplankton diversity and ensuring network stability. Furthermore, the growth duration of phytoplankton and zooplankton was influenced by the spatial distribution of sampling points in the river, contributing to complex interactions with environmental factors. The complexity of these interactions necessitates careful consideration in future studies on spatial patterns in riverine plankton communities.

In situ observations of zooplankton show changes in abundance and swimming speed in response to hypoxia and acidification

AbstractZooplankton exhibit diverse swimming behaviors to reposition themselves in the water column, feed, find mates, and avoid predation. Environmental stressors that modify behavior can have cascading effects on population distributions and predator–prey interactions. Understanding zooplankton population dynamics is challenging, largely because traditional methods for quantifying zooplankton distributions are costly, limited in scope, and require extended analysis by trained analysts. We developed a novel methodology that combined remotely deployed camera systems, machine learning‐based identification of zooplankton, and video‐based tracking technology to quantify copepod and amphipod in situ swimming behavior in Hood Canal, WA, USA, a seasonally hypoxic and acidified fjord. Behavioral analysis showed copepods of all sizes swam on average 24% slower in stressful (hypoxic and acidified) waters relative to non‐stressful waters. Copepods exhibited less frequent escape responses in stressful waters, with a 68% decrease in the amount of time spent “jumping” for copepods 1–2 mm in length. Interestingly, abundances of small copepods increased in stressful waters, with 56% more 1–2 mm long copepods in stressful vs. non‐stressful conditions. In contrast, amphipods' average “darting” speeds did not differ between environmental conditions, but the abundance of amphipods significantly decreased in stressful waters relative to non‐stressful waters, suggesting avoidance of stressful conditions. Changes in swimming behavior are informative metrics in understanding ecosystem impacts of environmental stress because swimming speed has individual, population, and community‐level implications. Our results suggest that, among copepods, in situ behaviors may be useful proxies in monitoring the impacts of climate change on coastal ecosystems.

Effects of amphibian genetic diversity on ecological communities.

The amount of genetic diversity within a population can affect ecological processes at population, community, and ecosystem levels. However, the magnitude, consistency, and scope of these effects are largely unknown. To investigate these issues, we conducted two experiments manipulating the amount of genetic diversity and environmental factors in larval amphibians. The first experiment manipulated wood frog genetic diversity, the presence or absence of caged predators, and competition from leopard frogs to test whether these factors affected survival, growth, and morphology of wood frogs and leopard frogs. The second experiment manipulated wood frog genetic diversity, the presence or absence of uncaged predators, and resource abundance to test whether these factors affected wood frog traits (survival, morphology, growth, development, and behavior) and other components of the ecological community (zooplankton abundance, phytoplankton, periphyton, and bacterial community structure). Genetic diversity did not affect wood frog survival, growth, and development in either experiment. However, genetic diversity did affect the mean morphology of wood frog tadpoles in the first experiment and the abundance and distribution of zooplankton in the second experiment. It did not affect phytoplankton abundance, periphyton abundance, or bacterial community structure. While effect sizes (Cohen's d) of genetic diversity were approximately half those of environment treatments, the greatest effect sizes were for interaction effects between genetic diversity and environment. Our results indicate that genetic diversity can have a large effect on ecological processes, but the direction of those effects is highly dependent upon environmental conditions, and not easily predicted from simple measures of traits.

Dispersal and connectivity modelling simulations for invertebrate larvae passing through the Strait of Gibraltar

Abstract The link between the northeastern Atlantic and Mediterranean Sea created by the Strait of Gibraltar and the adjacent Iberian and Moroccan coasts marks remarkable transition areas between distinct environments that harbour a diverse mixture of species. The area is interesting regarding marine connectivity and the transport of pelagic invertebrate larvae, crucial knowledge to manage over-exploited populations, and minimize the impacts of climate change and anthropogenic activities. Biophysical models were developed, combining oceanic and particle-tracking Lagrangian simulations with in situ zooplankton distribution data. The conditions driving the larval exchange between the sub-basins and the connectivity throughout the region were explored, using crustacean decapod larvae as biological references. The potential exchange between both sub-basins was confirmed, although specific larval traits revealed contrasting scenarios. The simulations showed that slope-dwelling and mesopelagic larvae have advantage when crossing from the Alboran into the Atlantic, in comparison with shelf-dwelling and epipelagic larvae. Transport pathways and retention areas were identified, and passive drifts were shown to increase the dispersal range of the simulations. The spatial origin of the larval release, larval duration, vertical distribution, and the interaction of larvae with the oceanic features are presented as the main factors impacting the effective larval input into the Atlantic or Mediterranean basins.

Biodiversity and functioning of mesozooplankton in a changing Ross Sea

Literature on Ross Sea zooplankton is limited, although it is the most productive system and has the highest biomass of phytoplankton in the Southern Ocean. Energy transfer within the food web and response of continental shelf food web to climate change depend on the knowledge of the density and distribution of zooplankton. We evaluated its density, composition, spatial distribution and their potential relations with environmental factors and specific water mass presence. Particular attention was given to copepods. Mesozooplankton samples were collected between 14 January and February 11, 2017 from 14 stations in the western Ross Sea and Terra Nova Bay, while other micronekton samplings were completed at 6 stations. Results highlighted three pools of stations: one inside Terra Nova Bay with the highest densities, one on the platform with lower mean density, and the third represented by a N–S transept at 175°E with the lowest mean density. This partitioning of the region fit with the grouping of stations according to a ternary plot based on the different percentages of water masses in each station and reflected the similarity of zooplankton. The presence of specific water masses and their contribution in the upper 200 m influences zooplankton biodiversity and density. A phylogenetic tree of the zooplankton was constructed to analyse the distance among the observed taxa. The area located near the coast exhibited the highest degree of phylogenetic overdispersion. In coastal waters, typical copepod species constituted the main part of the neritic zooplankton of Terra Nova Bay and Ross Sea. Oithona similis was the most abundant species both in coastal and offshore sectors, followed by pteropods, polychaetes and euphausiids.

Seasonal and Spatial Distribution of Zooplankton Communities with Relation to some Physico-Chemical Parameters in the South East Coast of Bangladesh

Seasonal and spatial distribution of zooplankton communities in relation with some physico-chemical parameters in the south eastern coastal waters of Bangladesh was carried out from January 2016 to November 2016. Zooplankton samples were collected from seven different selected stations covering various ecosystems, viz.: Riverine (Bhola, Barishal &amp; Chandpur), Offshore Island water (Sandwip &amp; Hatia) and Nearshore (Cox’s bazar &amp; Naf River) regions. In total 33 genera were recorded during sampling periods and the highest abundance of zooplankton were recorded at Naf River (331.318 ind/m3) and the lowest at Chandpur (22.6414ind/m3) during post-monsoon. In pre-monsoon the highest abundance was recorded at Sandwip (31.49435ind/m3) and the lowest at Bhola (8.239854ind/m3). During monsoon the highest abundance was recorded at Cox’s Bazar (51.64085ind/m3) and the lowest at Barishal (4.389972ind/m3). A total of 24, 22 and 32 individuals (genera) of zooplankton identified during monsoon, pre-monsoon and post-monsoon respectively from all sampling stations. Calanoida, Cyclopoida, Fish larvae, Lucifer and Shrimp Zoea were common in every sampling station. Dictoyptera was the only species found in marine water. The statistical analysis of water quality parameters as temperature, pH, salinity, transparency, DO, TDS and TSS indicated the substantial relationship with seasonal and spatial distribution, diversity and abundance of zooplankton. Diversity index also indicated seasonal and spatial variation of zooplankton communities in the south eastern coastal waters of Bangladesh. The Chittagong Univ. J. B. Sci.,Vol. 10(1 &amp;2):95-119, 2020

Salinity fronts shape spatial patterns in Zooplankton distribution in Hangzhou Bay

Salinity fronts shape spatial patterns in Zooplankton distribution in Hangzhou Bay

Seasonal Zooplankton Distribution and Species Composition in the Eastern Sea of Marmara

Seasonal Zooplankton Distribution and Species Composition in the Eastern Sea of Marmara

Pan‐Arctic distribution modeling reveals climate‐change‐driven poleward shifts of major gelatinous zooplankton species

AbstractAnthropogenic activities, including climate change, are hypothesized to cause increases in gelatinous zooplankton population sizes and blooms. In the most rapidly changing ecosystem, the Arctic Ocean, this hypothesis has not yet been verified, and gelatinous zooplankton is commonly excluded from large‐scale modeling studies. Our modeling study is based on an extensive biogeographic dataset, aggregating from four open‐source databases (Ocean Biodiversity Information System, Global Biodiversity Information Facility, Jellyfish Database Initiative, and PANGAEA). It includes data on eight of the most reported gelatinous zooplankton taxa of the pan‐Arctic region (Aglantha digitale, Sminthea arctica, Periphylla periphylla, Cyanea capillata, Oikopleura vanhoeffeni, Fritillaria borealis, Mertensia ovum, and Beroe spp.). By coupling three‐dimensional species distribution models with oceanographic components from the Max Planck Institute Earth System Model (MPI‐ESM1.2), run for historical (1950–2014) and future (2050–2099) periods under the shared socioeconomic pathway SSP370 scenario forcing, we identified species with expanding or contracting habitat ranges in response to climate change. Our projections indicated a general tendency for gelatinous zooplankton distributions to shift, with varying degrees of suitable habitat expansion (largest for the scyphozoan C. capillata ~ +180%) or contraction (largest for the hydrozoan Sm. arctica ~ −15%). Seven of the eight species modeled, which—similar to the majority of gelatinous taxa occurring in the Arctic Ocean—predominantly represented arcto‐boreal and boreal taxa, are projected to shift to northern latitudes. Hence, profound impacts on the Arctic marine environment and associated ecosystem services can be expected.

Spatio-temporal distribution of zooplankton and physico-chemistry in some rivers of the agricultural area of Awae (Centre Region-Cameroon)

Spatio-temporal distribution of zooplankton and physico-chemistry in some rivers of the agricultural area of Awae (Centre Region-Cameroon)

Distribution and Abundance of Zooplankton in Anthropogenic-Impacted Stream, Nsit-Ibom, Nigeria

This study aimed to investigate the distribution and abundance of zooplankton in Mbiokporo stream Nsit-Ibom Local Government Area, Akwa Ibom State, Nigeria. Samples were collected and analyzed using standard methods. The result revealed that there were 9 zooplankton taxonomic groups (namely: Arachnida, Bdelloidae, Branchiopoda, Chromadorae, Euglenoidea, Hexanauplia, Insecta, Polychaeta, Tubulinea), comprising 12 species and 91 individuals. The most abundant zooplankton species was Temora longicornis with the highest number of species across all the stations 24 &gt; 19 &gt; 7 for station 1, station 2, and station 3 respectively. Branchiopoda had the highest number of species (4) and highest species composition (33.33%), while Hexanauplia recorded the highest individual abundance (54.95%). The relative abundance of zooplankton phyla was as follows: (Hexanauplia, 54.95 %) &gt; (Branchiopoda, 13.19 %) &gt; (Bdelloidae, 8.79) % &gt; (Chromadorae, 7.69 %) &gt; (Polychaeta and Arachnida, 5.49 % each) &gt; (Insecta, 2.20 %) &gt; (Tubulinea, 1.10 %) respectively. Indices of species dominance were as follows: station 1 &gt; station 2 &gt; station 3, with the following values 0.4349 &gt; 0.4235 &gt; 0.2397 each. Meanwhile, the highest species evenness was in station 3 (0.7887), followed by station 2 (0.5495), while the lowest was in station 1 (0.486). Margalef’s species diversity was slightly higher in station 1 (1.649) than in station 3 (1.618) while the lowest was in station 2 (1.456). The equitability index among stations was as follows: 3 (0.8675) &gt; station 2 (0.6659) &gt; station 1 (0.6292). However, this result revealed that ongoing anthropogenic activities along the stream may resulted in the deterioration of the stream thereby leading low species composition of zooplankton as observed in this study.

Effect of Environmental Variables on Zooplankton in Various Habitats of the Nile River

The present study investigated the effect of environmental variables on the abundance and distribution of zooplankton in different habitats along the Nile River in Shattura Village. Zooplankton samples were collected from three distinct sites along the Nile River in Shattura Village, each exhibiting different environmental characteristics: Site 1 with vegetation, site 2 lacking vegetation, and site 3 being a drain canal. The study spanned from spring 2020 to winter 2021, during which the physico-chemical parameters of the water were analyzed. Rotifera constituted the majority of the zooplankton (54.73%), followed by Cladocera (20.59%), Copepoda (13.1%), and Ostracoda (8.9%). Among the 52 identified zooplankton species, Rotifera comprised 18 species, Cladocera 13 species, Copepoda 10 species, and Ostracoda 11 species. Site 1 exhibited the highest zooplankton density (44.08%), attributed to the presence of vegetation, followed by site 3 (37.18%), influenced by agricultural drains, and site 2 had the lowest density (18.73%). Zooplankton abundance peaked in summer and declined in winter. Notably, Rotifera abundance increased in populated sites (site 3), whereas other zooplankton groups thrived in less populated areas. Correlation analyses revealed positive associations between Rotifera and Cladocera with electric conductivity, total dissolved solids (TDS), chloride (Cl), calcium (Ca), and sulfate (SO4). Conversely, Copepoda showed positive correlations with water transparency, pH, dissolved oxygen, and biological oxygen demand (BOD). Overall, seasonal variations significantly impacted the zooplankton community, with Rotifera dominating and Ostracoda being the least abundant. High values of the Shannon–Weaver diversity index, richness, and evenness suggested ample food resources and favorable growth conditions. Transparency, conductivity, pH, dissolved oxygen, and BOD were identified as the key influencing parameters on zooplankton abundance. Additionally, vegetation and agricultural drains strongly influenced total zooplankton levels.

Işıklı Gölü (Çivril-Denizli/Türkiye) zooplankton dağılımı ve kompozisyonunun trofik durum değerlendirmesi ile araştırılması

In this study, the zooplankton distribution and composition of Işıklı Lake, located in the Inner West Anatolia region of Türkiye, were examined monthly between 2003-2005. Zooplankton samples were collected with Hydro-Bios plankton net (55 µm) at the surface and fixed in formaldehyde (4 %). Physiological parameters such as surface water temperature, pH, dissolved oxygen, and conductivity were also measured. Also, the frequency index (F %) and the Brachionus / Trichocerca (QB/T) were determined to assess the trophic composition of Lake Işıklı. A total of 49 species have been identified. Rotifera (55 %), Cladocera (27 %) and Copepoda (18%) were represented by the species. The maximum species was found in May 2004 (21 species), while the minimum was found in October 2003 (5 species). Asplanchna priodonta, Keratella cochlearis, Keratella tecta, Polyarthra dolichoptera, Synchaeta pectinata, Bosmina longirostris and Chydorus sphaericus are common species in the lake. The water temperature varied between 3.9-24.6 °C; pH ranged from 8.1 to 8.8; the electrical conductivity ranged from 341 µS/cm to 434 µS/cm; the dissolved oxygen values changed from 5.8 mg/L to 11.1 mg/L. According to the frequency index (F %), the most dominant species are B. longirostris (74 %), K. cochlearis (62 %), A. priodonta (54 %), and C. sphaericus (51 %). A total of 20 species are reported for the first time from the region. Newly reported species from the lake were: the rotifers, A. priodonta, Brachionus angularis, Brachionus calyciflorus, Colurella colurus, Keratella quadrata, Lecane clostrocerca, Lecane ludwigi, Lecane luna, Lecane lunaris, Lecane ohioensis, Lecane quadridentata, Lecane sp., Mytilina mucronata, Notholca acuminata, Notholca squamula, Trichotria tetractis, the cladocerans Acroperus harpae, Daphnia cucullata, and the copepods Eucyclops macrurus and Megacyclops gigas. Considering the Brachionus / Trichocerca (QB/T) ratio according to the Sládeček (1983) index, the lake showed mesotrophic features.

Seasonal evaluation of heavy metals and zooplankton distribution and their co-relationship in the Rosetta branch area of the Nile Delta in Egypt

The River Nile is the artery of Egypt, as it presents more than 96% of the municipal, industrial, and irrigation necessities of Egypt. This study was dedicated to providing data about the effect of pollution at six stations on the River Nile at the Rosetta branch during the period from August 2019 to April 2020, using heavy metals analysis and zooplankton as biological indicators. It was found that the average of heavy metals concentration follows the descending order Al > Fe > Mn > Zn > Ni > Co. Most of the heavy metals recorded its highest values at El-Rahawy station. Zooplankton community was represented by 32 species in addition to 4 Meroplanktons. Five groups of zooplankton were recorded, viz. Rotifera (1717 org./L), Protozoa (552 org./L), Cladocera (54 org./L), Nematoda (46 org./L), and other Meroplankton (44 org./L), dominated by Rotifera followed by Protozoa, Cladocera, Nematoda, and other Meroplanktons contributing 71%, 23%, 2%, 2%, and 2%, respectively. The highest average density of total zooplankton was recorded during spring while the lowest was recorded during summer. The highest similarity of (79.12%) was observed between (Site 1) and (Site 5). Almost all diversity indices were conducted and showed its highest values in site 6. The principal component analysis conducted between heavy metals, and zooplankton showed a significant negative correlation was shown for the dominant zooplankton with the heavy metals except with cobalt. Nematoda and the rotifer Brachionus angularis recorded a positive correlation with heavy metals except cobalt.

Automated zooplankton detection from in situ imagery for forward scattering predictions

Ocean midwaters—the vast region between the sunlit surface layers and seafloor—comprise the largest habitat on Earth but are among the least understood marine environments. This project aims to combine concurrently collected imaging and acoustic measurements in the epi and mesopelagic environment to interpret zooplankton scattering from mixed assemblages and determine in situ zooplankton distributions within their local environments. We have trained a machine learning model for the automated detection of 13 zooplankton functional groups from a 1000m rated towed shadowgraph imaging system. The zooplankton detection model currently achieves 80% F1 scores on our validation image set and was trained using adversarial methods. We have derived biometric measurements from the zooplankton image data necessary to generate forward scattering predictions. We compare the distributions of scattering layers detected acoustically with zooplankton distributions from the imagery. We will compare forward scattering predictions derived from sparse geometric representations of the zooplankton and full 3D model volumes using the distance transform of the zooplankton images. This work will further enable the use of optical techniques for midwater surveys and the interpretation of acoustic scattering returns from mixed zooplankton populations.