Western Basin Research Articles

Models of helium enrichment in helium-rich gas reservoirs of petroliferous basins in China

Owing to the characteristics of chemical inertness, low molecular weight, low boiling point, strong permeability and high heat conductivity, helium is extensively used in the fields of aerospace, low-temperature superconductivity, medicine and high tech, and it is a kind of irreplaceable strategic rare resource. So far, however, less research has been conducted on the enrichment of helium in natural gas reservoirs. To solve this problem, this paper discusses the classification standard of helium-rich gas reservoirs. Based on this, the origin, source and enrichment process of helium in typical helium-rich gas reservoirs are studied, highlighting the contribution of main helium sources to helium-rich gas reservoirs. In addition, helium enrichment models of helium-rich gas reservoir in petroliferous basins are established. And the following research results are obtained. First, 6 helium enrichment models of two categories (crust-source helium enrichment and crust-mantle mixing helium enrichment) are established for different petroliferous basins in China. Second, helium-rich gas reservoirs are characterized by using the multiple helium supply and diverse helium enrichment model. And no matter what enrichment model it is, the contribution of the main helium source to gas reservoirs is indispensable. Third, the helium in the gas reservoirs of central and western basins is mainly crust-source helium, and its enrichment models include ancient formation water moving upward along the fault to dilute helium, helium enrichment in the process of natural gas migration along ancient reservoirs, and helium enrichment of shale gas. Fourth, the helium in the helium-rich gas reservoirs of eastern basins is of crust-mantle mixing origin and its enrichment models are mainly hydrocarbon gas based, carbon dioxide based and nitrogen based. In conclusion, the establishment of the helium enrichment models of helium-rich gas reservoirs in petroliferous basins provides reference and guidance for studying helium enrichment laws and main controlling factors and is of great significance to the evaluation of favorable helium exploration areas.

The Fate and Bioavailability of Resuspended Phosphorus in Lake Erie's Western Basin

The Fate and Bioavailability of Resuspended Phosphorus in Lake Erie's Western Basin

Nutrient management in Lake Erie: Evaluating stakeholder values, attitudes, and policy preferences

Harmful algal blooms (HABs) have impaired Lake Erie’s western basin water quality since the 1960s. Though scientists agree that eutrophication is a key driver of HABs in Lake Erie, the role of nitrogen is still the subject of debate. The problem is twofold: (1) uncertainty in the specific causes of HABs can lead to inappropriate management solutions, and (2) managing a cross-boundary watershed requires collaboration and agreement on apt solutions from multiple stakeholders as well as many U.S. states and Canadian provinces. In our study, we interviewed 29 stakeholders actively involved in western Lake Erie’s watershed. We analyzed the stakeholders’ values, attitudes, and policy preferences to understand their differences, similarities, and their effects on management decisions. We found that stakeholders agree on the urgency of the problem and the necessity for increased nutrient management in Lake Erie’s western basin. Furthermore, we found that stakeholders can be represented as distinct clusters based on their values, and these value-based clusters are associated with different policy preferences. The different opinions and preferences of these value clusters span across stakeholder sectors and may affect efforts toward policy change. Stakeholders often question the feasibility and effectiveness of existing policies and policy plans. The findings shed new light on the relationship between stakeholder type and environmental values, attitudes, and policy preferences. Collaboration on HABs in Lake Erie will require open lines of communication both to improve policy and to cultivate trust among the multiple parties in this diverse watershed.

Influence of multiple islands on the hysteresis and dynamics of a western boundary current perturbed by a mesoscale eddy at a gap

The hysteresis of a western boundary current (WBC) flowing across a gap and the dynamics of the mesoscale eddy–WBC interaction with the presence of two islands in the gap are studied using a 1.5-layer ocean model. The hysteresis of the WBC suggests that the two islands in the gap facilitate the WBC to intrude into the western basin by shedding eddies compared with the no-island case, but they promote the WBC to leap across the gap compared with the one-island case. The mesoscale eddies from the east of the gap can induce the critical-state WBC shifting from penetration to leap and vice versa. The dynamics revealed by the vorticity balance analysis shows that the increased (decreased) meridional advection of the WBC perturbed by the eddy forces the WBC to leap across (intrude into the western basin through) the gap. We also present the parameter space of the critical strength of the eddy with variable north–south locations inducing the critical WBC transition. For the WBC critical from the eddy-shedding to leaping regime, the regime shift is most sensitive to the anticyclonic eddy from the gap center and to the cyclonic eddy from the southern gap. It is least sensitive to the eddy downstream of the WBC. For the WBC critical from the leaping to eddy-shedding regime, the regime shift is most sensitive to the anticyclonic eddy upstream of the WBC and to the cyclonic eddy from the southern gap. The least sensitive eddy is from the northern gap.

Humpback whale (Megaptera novaeangliae) occurrence in the Mediterranean Sea

Humpback whales were considered extremely rare in the Mediterranean Sea until recently. Only two confirmed records were known from a period of more than 100 years and both were from the western basin. However, nine new observations spread across both Mediterranean basins have been recorded since 1990. This increase in numbers and range during a relatively short period of time seems to be a new, growing trend, suggesting that the occurrence of humpback whales in the Mediterranean Sea is no longer accidental, but occasional. It coincides with the recovery of some stocks of the expanding North Atlantic population after their depletion during a long period of whaling. The true reason behind increased humpback whale entries in the Mediterranean Sea and their exact origin cannot be known until new occurrences are properly photo-identified and sampled genetically.

Differential hydrocarbon generation and evolution of typical terrestrial gas-prone source rocks: An example from the Kuqa foreland basin, NW China

Terrestrial gas-prone source rocks are significant for hydrocarbon gas accumulations especially in central and western basins in China. The Kuqa foreland basin in the northern margin of the Tarim Basin, NW China is rich in natural gas with recent discoveries of several large to giant gas-producing fields (e.g., the Kela-2, Dibei, Dabei-1, and Zhongqiu-1 gas fields, etc.) and a proven 3 P gas reserve of over one trillion cubic meters (TCM). This proliferous petroleum province is powered by an effective and diverse gas-prone source rock series in the basin comprising mudstone, carbonaceous mudstone, and coal seams. To date, little systematic research work has been done on the petroleum generation potential of the source rocks. This has seriously restricted the assessment of petroleum resources and further exploration in the frontier areas of the basin. A sealed gold tube pyrolysis approach was employed to simulate the oil and gas generation and cracking yields for the aforementioned three types of source rock. Compared with typical Type I and II1 kerogens, the three types of source rocks in the Kuqa foreland basin are characterized by (1) far less hydrocarbon yield (150 mg/g TOC) with comparatively larger amounts of CO2 (310 mg/g TOC), (2) a limited capacity and narrower window (0.5%–1.08% Ro) for oil generation, and (3) a much earlier secondary cracking for bulk oil to light oil and gases (>0.86% Ro for mudstone and >1.08% Ro for both carbonaceous mudstone and coal). All the source rocks are gas-prone, and significant amount of gas can still be generated during an over-mature stage. The kinetic parameters obtained allow us to model hydrocarbon generation in the Kuqa foreland basin more realistically. It is concluded that (1) two episodes of hydrocarbon generation occurred with hydrocarbon gases being mainly generated during the later stage (12–3 Ma); and (2) the depocenter of the basin is capable of supplying massive high-mature gases as late as in the Quaternary, which is crucial for the formation of giant gas fields. The findings provide new insight on the reconstruction of oil and gas accumulation processes and further hydrocarbon exploration in the basin.

Genomics reveals the role of admixture in the evolution of structure among sperm whale populations within the Mediterranean Sea.

In oceanic ecosystems, the nature of barriers to gene flow and the processes by which populations may become isolated are different from the terrestrial environment, and less well understood. In this study we investigate a highly mobile species (the sperm whale, Physeter macrocephalus) that is genetically differentiated between an open North Atlantic population and the populations in the Mediterranean Sea. We apply high-resolution single nucleotide polymorphism (SNP) analysis to study the nature of barriers to gene flow in this system, assessing the putative boundary into the Mediterranean (Strait of Gibraltar and Alboran Sea region), and including novel analyses on structuring among sperm whale populations within the Mediterranean basin. Our data support a recent founding of the Mediterranean population, around the time of the last glacial maximum, and show concerted historical demographic profiles in both the Atlantic and the Mediterranean. In each region there is evidence for a population decline around the time of the founder event. The largest decline was seen within the Mediterranean Sea where effective population size is substantially lower (especially in the eastern basin). While differentiation is strongest at the Atlantic/Mediterranean boundary, there is also weaker but significant differentiation between the eastern and western basins of the Mediterranean Sea. We propose, however, that the mechanisms are different. While post-founding gene flow was reduced between the Mediterranean and Atlantic populations, within the Mediterranean an important factor differentiating the basins is probably a greater degree of admixture between the western basin and the North Atlantic and some level of isolation between the western and eastern Mediterranean basins. Subdivision within the Mediterranean Sea exacerbates conservation concerns and will require consideration of what distinct impacts may affect populations in the two basins.

Trends in Lake Erie zooplankton biomass and community structure during a 25-year period of rapid environmental change

Zooplankton play a key role in aquatic ecosystems, providing potential top-down control on phytoplankton and linking primary production to higher trophic levels. Thus, knowledge of zooplankton dynamics is fundamental to any assessment of the impacts of human driven rapid environmental change on lakes. Lake Erie has undergone eutrophication since the 1990s, resulting in summer harmful cyanobacterial blooms, dominated by Microcystis aeruginosa, since approximately 2003 in the western basin (WB) and 2008 in the central basin (CB). The effect of eutrophication on zooplankton in Lake Erie is unclear; few studies have characterized trends in zooplankton biomass and community structure during this period of rapid change. We used the Lake Erie Plankton Abundance Study (LEPAS) zooplankton dataset to analyze interannual trends in the dynamics of eight major zooplankton groups in the WB and CB during 1995–2020. In both basins, we found directional change in zooplankton biomass and community structure. These directional trends in zooplankton biomass overlaid approximate five-year cycles in nearly all taxa, potentially linked to the El Niño Southern Oscillation. Eutrophication was associated with an increase in the summer biomass of total zooplankton, calanoids, and large cladocerans but surprisingly, not cyclopoids, rotifers or small cladocerans. The surprisingly positive or neutral effect of eutrophication and M. aeruginosa on zooplankton biomass may be due to a combination of bottom-up (e.g. concurrent increases in more edible algae) and top-down (e.g. changes in planktivory) forces.

DISTRIBUTION OF INVADER <i>MNEMIOPSIS LEIDYI</i> (CTENOPHORA) IN EARLY STAGES OF DEVELOPMENT IN THE SOUTH-EASTERN BALTIC SEA IN AUTUMN 2021

The embryos within the egg envelope (eggs) and cydippid stage larvae of alien species of ctenophore Mnemiopsis leidyi were recorded in the South-Eastern Baltic Sea (within the economic zone of the Russian Federation) in the autumn of 2021. The adults of Mnemiopsis leidyi were not found. The data on the occurrence and distribution of ctenophore in the early stages of development in the SEB were given. The ctenophore eggs were recorded in the open part of the SEB at the stations with the depths of 65-115 m in the intermediate layer and below the upper boundary of the halocline. A large number of eggs (51-57 ind./m3) were observed on the north-eastern slope of the Gdansk Deep. The area of occurrence of ctenophore eggs in 2021 increased compared to the data of 2010-2015. The significant correlation between the eggs abundance and the water salinity and temperature was not revealed. Using the NEMO 4.0 numerical model, the path of advective water penetration into the study area from the western basins of the Baltic Sea, which probably introduced the ctenophore eggs, was traced.

Influence of spatial and temporal variation on establishing stable isotope baselines of δ15N, δ13C, and δ34S in a large freshwater lake

Abstract It is essential to establish a baseline in studies using stable isotopes to interpret trophic relationships across ecosystems and through time. Studies in freshwater ecosystems struggle to quantify baseline stable isotopes due to difficulties collecting representative samples, particularly from pelagic habitats. We assessed temporal and spatial variation in δ13C, δ15N, and δ34S in a commonly used pelagic baseline, seston (n = 156), in Lake Erie to understand mechanisms that correlate with baseline stable isotope dynamics in large lakes. Seston contains a wide range of material which can confound stable isotope interpretation, and we examined the utility of element content and ratios to account for variation in sample source. Seston was collected in each of the three basins of Lake Erie from May to October in 2017–2019 at nearshore (<10 m depth) and offshore (>10 m depth) sites. General linear models were conducted on each stable isotope (δ15N, δ13C, and δ34S) and sample composition (variables: %N, %C, %S, C:N, C:S, and N:S) to assess how basin, month, and collection year influenced seston stable isotopes and composition. Sample composition (variables: %N, %C, %S, C:N, C:S, and N:S), which is rarely reported for organisms in stable isotope studies, was constant throughout the sample period with no temporal or spatial trends except for small variations in %C, C:N, C:S, and N:S. This indicated that the temporal and spatial trends observed within the stable isotopes were related to seasonal changes in system processes and plankton community dynamics, with few or minimal changes in the amount of detrital and inorganic material within seston. Values and trends of δ15N, δ13C, and δ34S in seston were comparable to those measured previously in Lake Erie and other Laurentian Great Lakes. All three isotopes increased from May to October of each sample year and varied spatially, δ15N was higher, δ34S was lower, and δ13C was the same in the west basin compared to the central and eastern basins of Lake Erie, which did not differ. These trends probably reflect seasonal changes in plankton community composition and nutrient cycling throughout the lake and are potentially linked to the presence of Microcystis blooms in the western basin during the late summer and autumn. Seston turns over quickly, as shown by the rapid changes in stable isotope values throughout the study, which confounds the investigation of stable isotopes in upper trophic levels, and especially in organisms that have slower tissue turnover and move throughout the lake seasonally. Additionally, the variable composition of seston (e.g., % C, % N, % S, C:N, C:S, N:S) necessitates analysing sample composition to determine the degree of abiotic (e.g., detritus, sediment, particulate organic matter) and biotic (e.g., phytoplankton, zooplankton) content in it.

Drivers of Marine CO2‐Carbonate Chemistry in the Northern Antarctic Peninsula

AbstractThe Bransfield Strait is a climate change hotspot at the tip of the northern Antarctic Peninsula (NAP). The region is marked by a mixture of relatively warm waters from the Bellingshausen Sea with cold shelf waters from the Weddell Sea. Additionally, its deep central basin (>800 m) preserves seawater properties from the north‐western Weddell Sea continental shelf. This study assessed long‐term changes in carbonate chemistry in the Bransfield Strait and found that the hydrographic setting (i.e., a mixture between modified‐Circumpolar Deep Water with Dense Shelf Water [DSW]) drives temporal variability of carbonate parameters. The western basin has experienced decreases in pH (seawater scale) over the last three decades (1996–2019), varying from −0.003 to −0.017 pH units yr−1, while Ωar decreased from −0.01 to −0.07 yr−1 throughout the water column. The central basin was characterized by a high contribution of DSW with high carbon dioxide (CO2) content and the decomposition of organic matter produced and transported into its deep layer. With lower variability for all carbonate system variables, the eastern basin was likely regulated by internal mixing. Overall, the entire strait is almost reaching a CO2‐saturated condition, highlighting how sensitive subpolar regions are to the effects of human‐induced climate change.

Stability & Change in a Freshwater Ecosystem

A report by the U.S. Environmental Protection Agency found 46% of rivers and streams and 21% of lakes are in poor biological condition (EPA, 2017). In this 5E standards-based inquiry lesson, students actively engage with the natural phenomena of algal blooms through the introduction of the harmful algal bloom (HAB) that occurred in Lake Erie’s western basin in the summer of 2011. Students make sense of relationships within aquatic ecosystems, using microcosms (miniature ecosystems) containing phytoplankton and zooplankton, and then communicate their findings through a scientific manuscript. This lesson engages students in the three-dimensional learning identified in the Next Generation Science Standards (NGSS) under the standard of HS-LS2, Ecosystems: Interactions, Energy, and Dynamics. More specifically, students address the expectation of HS-LS2-6 when they make sense of how the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, while changing conditions may result in new ecosystems. This long-term scientific investigation also provides students with opportunities to make sense of aspects of the nature of science, while increasing their science content knowledge and understanding of the practices of science. Evaluation of student work occurs at all stages of the lesson.

Spatio-temporal characteristics and driving factors of the meteorological drought across China based on CMIP6

Abstract The characteristics of meteorological drought in different river basins in China have clear spatio-temporal differences and the difference between watersheds is also reflected in the influence mechanism of meteorological drought. This study investigated the meteorological drought risk under different future emission scenarios, based on the Coupled Model Intercomparison Project 6 (CMIP6). Furthermore, we explored the influence of precipitation and temperature on meteorological drought in different basins of China in the future. Meanwhile, the uncertainty associated with CMIP6 in different watersheds is also considered. In the future, the frequency of meteorological drought events mainly shows a decreasing trend, but the drought intensity and duration increase. In China, the rate of probability change in drought's intensity was greater than drought duration and the probability distribution of drought characteristics is significantly different between the historical and the future periods. Under the low and medium emission scenarios (SSP126 and SSP245), the Joint Recurrence Period of future drought intensity and duration increases and the Recurrence Period decreases in the western and north-eastern basins. Precipitation plays a major role in the meteorological drought, especially in the northeast and southeast basins of China.

Commercial sharks under scrutiny: Baseline genetic distinctiveness supports structured populations of small-spotted catsharks in the Mediterranean Sea

The present study, based on microsatellite markers, describes a population genetic analysis of the small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758), representing one of the most abundant and commonly caught cartilaginous fishes in the Mediterranean Sea and adjacent areas. The analyses were performed to unravel the genetic features (variability, connectivity, sex-biased dispersal) of their relative geographic populations, both at the small (around the coast of Sardinia, Western Mediterranean Sea) and at a larger spatial scale (pan-Mediterranean level and between the Atlantic Ocean and the Mediterranean Sea). Individual clustering, multivariate and variance analyses rejected the hypothesis of genetic homogeneity, with significant genetic differences mainly within the Mediterranean between the Western and Eastern basins, as well as between the Mediterranean and the NE Atlantic Ocean. In detail, our results seem to confirm that the Strait of Gibraltar could not represent a complete barrier to the exchange of individuals of small-spotted catshark between the Atlantic Ocean and the Mediterranean Sea. In the latter area, a complex genetic structuring for S. canicula was found. Apart from differences among the Western, Eastern and Adriatic sites, within the Western basin the small-spotted catsharks around Sardinian waters are strongly differentiated from all others (both from the eastern Tyrrhenian Sea and southernmost part of the Algerian basin) and are demographically stable. Several possible mechanisms, both biological and abiotic (e.g., migratory behavior, waterfronts, and oceanographic discontinuities), are discussed here to explain their peculiar characteristics. Overall, the genetic data presented, both at the local and regional level, could represent a baseline information, useful for the temporal monitoring of populations, and to assess the effects of present or future fishing/management/conservation measures.

Cetaceans in the Mediterranean Sea: Encounter Rate, Dominant Species, and Diversity Hotspots

We investigated the presence and diversity of cetaceans in the Mediterranean Sea, analysing the data collected by 32 different research units, over a period of 15 years (2004–2018), and shared on the common web-GIS platform named Intercet. We used the encounter rate, the species prevalence, and the Shannon diversity index as parameters for data analysis. The results show that cetacean diversity, in the context of the Mediterranean basin, is generally quite low when compared with the eastern Atlantic, as few species, namely the striped dolphin, the bottlenose dolphin, the fin whale, and the sperm whale, dominate over all the others. However, some areas, such as the Alboran Sea or the north-western Mediterranean Sea, which includes the Pelagos Sanctuary (the Specially Protected Area of Mediterranean Interest located in the northern portion of the western basin), show higher levels of diversity and should be considered hotspots to be preserved. Primary production and seabed profile seem to be the two main drivers influencing the presence and distribution of cetaceans, with the highest levels of diversity observed in areas characterized by high levels of primary production and high bathymetric variability and gradient. This collective work underlines the importance of data sharing to deepen our knowledge on marine fauna at the scale of the whole Mediterranean Sea and encourages greater efforts in the networking process, also to accomplish the requirements of the Marine Strategy Framework Directive, with particular reference to Descriptor 1: biological diversity is maintained.

Transcriptionally active nitrogen fixation and biosynthesis of diverse secondary metabolites by Dolichospermum and Aphanizomenon-like Cyanobacteria in western Lake Erie Microcystis blooms

Cyanobacterial harmful algal blooms (cyanoHABs) in the western basin of Lake Erie are dominated by microcystin producing Microcystis spp., but other cyanobacterial taxa that coexist in these communities may play important roles in production of toxins and shaping bloom dynamics and community function. In this study, we used metagenomic and metatranscriptomic data from the 2014 western Lake Erie cyanoHAB to explore the genetic diversity and biosynthetic potential of cyanobacteria belonging to the Anabaena, Dolichospermum, Aphanizomenon (ADA) clade. We reconstructed two near-complete metagenome-assembled genomes from two distinct ADA clade species, each containing biosynthetic gene clusters that encode novel and known secondary metabolites, including those with toxic and/or known taste and odor properties, that were transcriptionally active. However, neither ADA metagenome-assembled genome contained genes encoding guanitoxins, anatoxins, or saxitoxins, which are known to be produced by ADA. The ADA cyanobacteria accounted for most of the metagenomic and metatranscriptomic reads from nitrogen fixation genes, suggesting they were the dominant N-fixers at the times and stations sampled. Despite their relatively low abundance, our results highlight the possibility that ADA taxa could influence the water quality and ecology of Microcystis blooms, although the extent of these impacts remains to be quantified.

On periodic growth and shrinkage of glaciers in the Warwan sub-basin, western Himalaya, between 1990 and 2020

Knowledge about glacier extent, dynamics, and characteristics are important for climate change attribution and prediction. Understanding on long-term dynamics and glacier inventory is crucial, particularly for the melt-dominated and latitudinally-diverse western Himalayan glacier basins. In this study, a temporal inventory is prepared for Warwan-sub basin (WSB), utilizing satellite imageries since the 1993 (Landsat TM: 1993; ETM+: 2001, 2008; OLI: 2020) and elevation model (SRTM DEM: 2000). The base inventory was generated for the year 2001 and systematically adjusted to the glacier situations in 1993, 2008, and 2020. Results indicate that in the year 2001, WSB in the western Himalaya included 84 glaciers (> 0.02 km2) covering an area of 187.9 ± 5.8 km2. The mapping (2001) further revealed a supraglacial debris cover of 15% of the glacierized area (28.2 ± 0.9 km2). Overall, the debris cover increased by 6% between 1993 and 2020. Temporal analyses clearly suggest a period of gain in the glacierized area (2001-2008) interspersed by the two phases of decline (1993-2001 and 2008-2020). Results specify a stronger decline in the glacierized area during 1993 to 2001 (197.03 ± 6.1 to 187.9 ± 5.8 km2) than between 2008 and 2020 (188.4 ± 5.9 to 182.8 ± 5.66 km2). Remarkably, the glacierized area increased from 187.9 ± 5.8 to 188.4 ± 5.8 km2 during 2001 to 2008. In view of widespread recession of regional glaciers, the gain in the area between 2001 and 2008 represents a peculiar characteristic of WSB that needs further detailed investigation. Further analyses suggest that low-altitude, east-facing, debris-free, steep-sloped, and small glaciers experienced greater loss in the area than large, debris-covered, north-facing, gently sloped, and high-altitude glaciers. Overall, the study at the sub-basin scale reveals inherent glacier dynamics with periodic increase and decrease in the glacierized area and a notable influence of non-climatic factors in regulating spatial heterogeneity and the rate of glacier changes.

Rising seawater temperatures affect the fitness of Rhopilema nomadica polyps and podocysts and the expansion of this medusa into the western Mediterranean

Since first reported in the eastern Mediterranean in the 1970s, the swarm-forming scyphomedusa, Rhopilema nomadica, has been continuously expanding westward. We examined the effect of temperature on the benthic stages of this jellyfish (polyps, podocysts, and strobilae) to assess whether it can survive and reproduce in the western Mediterranean temperature regime (12.2-26.2°C). In the first experiment, polyps and podocysts were maintained at 4 constant temperatures (12, 18, 24, and 30°C) for 55 d. In the second experiment, temperatures were gradually reduced over 14 d, kept constant for 18 d, and then gradually brought back to 25°C. High temperatures proved beneficial to polyp survival and asexual reproduction, yet in some cases, polyps were able to survive temperatures as low as 12°C. Strobilation occurred at temperatures between 22 and 30°C. Podocyst production, excystment, and strobilation all take place following a temperature increase, and excystment of podocysts occurs mainly during the first 2 wk following podocyst production. We propose that the role of podocysts in R. nomadica is mainly to increase the current season’s polyp population, contributing to swarm formation rather than as a means to maintain polyp populations during harsh environmental conditions. Since polyps are able to survive winter temperatures in the western basin (12°C) and reproduce by podocysts and strobilation during summer temperatures (24°C), thermal constraints will probably not restrict the expansion of R. nomadica into the western Mediterranean. Expected future climate change conditions will increase the performance and range expansion of this species.

Spatio-temporal connectivity of the aquatic microbiome associated with cyanobacterial blooms along a Great Lake riverine-lacustrine continuum.

Lake Erie is subject to recurring events of cyanobacterial harmful algal blooms (cHABs), but measures of nutrients and total phytoplankton biomass seem to be poor predictors of cHABs when taken individually. A more integrated approach at the watershed scale may improve our understanding of the conditions that lead to bloom formation, such as assessing the physico-chemical and biological factors that influence the lake microbial community, as well as identifying the linkages between Lake Erie and the surrounding watershed. Within the scope of the Government of Canada's Genomics Research and Development Initiative (GRDI) Ecobiomics project, we used high-throughput sequencing of the 16S rRNA gene to characterize the spatio-temporal variability of the aquatic microbiome in the Thames River-Lake St. Clair-Detroit River-Lake Erie aquatic corridor. We found that the aquatic microbiome was structured along the flow path and influenced mainly by higher nutrient concentrations in the Thames River, and higher temperature and pH downstream in Lake St. Clair and Lake Erie. The same dominant bacterial phyla were detected along the water continuum, changing only in relative abundance. At finer taxonomical level, however, there was a clear shift in the cyanobacterial community, with Planktothrix dominating in the Thames River and Microcystis and Synechococcus in Lake St. Clair and Lake Erie. Mantel correlations highlighted the importance of geographic distance in shaping the microbial community structure. The fact that a high proportion of microbial sequences found in the Western Basin of Lake Erie were also identified in the Thames River, indicated a high degree of connectivity and dispersal within the system, where mass effect induced by passive transport play an important role in microbial community assembly. Nevertheless, some cyanobacterial amplicon sequence variants (ASVs) related to Microcystis, representing less than 0.1% of relative abundance in the upstream Thames River, became dominant in Lake St. Clair and Erie, suggesting selection of those ASVs based on the lake conditions. Their extremely low relative abundances in the Thames suggest additional sources are likely to contribute to the rapid development of summer and fall blooms in the Western Basin of Lake Erie. Collectively, these results, which can be applied to other watersheds, improve our understanding of the factors influencing aquatic microbial community assembly and provide new perspectives on how to better understand the occurrence of cHABs in Lake Erie and elsewhere.

Hydrodynamic and circulation pattern in Lake Burullus, Egypt

To improve the water quality of Lake Burullus, Delft3D FM hydrodynamic model was applied to simulate the flow and transport models in the Lake. Both the in situ field data and the Lake up-to-date geomorphology were used to get a clear-cut figure. Four different scenarios were applied. The most appropriate solution was obtained from the fourth scenario that suggested constructing a new channel at the northwestern corner of the Lake connecting it to the open Mediterranean Sea and clearing some existing islands and reeds to enhance the free movement of the water among the entire Lake, especially in the western basin.