Ilia S Ostrovsky

Israel Oceanographic and Limnological Research Institute (IOLR) · Yigal Allon Kinneret Limnological Laboratory (KLL)

1. Parabolic (power) growth is characteristic of many aquatic poikilothermic animals for certain stages of their development. The parabolic pattern describing growth in weight (or length) under constant ambient conditions can be expressed in the following general form: where Y is growth rate (or specific growth rate), X is animal size, and Ω and τ...

Spatial and temporal heterogeneity in sedimentation of particulate organic material (POM) was studied in a large subtropical lake, and its export from the upper mixed layer was quantified. Sedimentation fluxes were measured over 4 yr with traps deployed in pelagic and littoral areas, the benthic boundary layer (BBL), and the lake interior. Analysis...

Introduction Changes in the watershed and their long-term impacts on Lake Kinneret Long-term lake salinity changes Long-term lake stratification changes Long-term changes to phytoplankton The invasion of nitrogen-fixing cyanobacteria (Nostocales) Winter populations of toxic Microcystis Long-term variation of chlorophyll and primary production Long-...

Fish are at the top of aquatic food webs impacting on other biota. Removal of fish by fishing, or stocking the lake with desired fish species has the potential to modify fish populations (their size/age structure, abundance and biomass) and various other ecosystem components and thus affect water quality. Analysis of long-term data on the catches o...

Harmful cyanobacterial blooms pose a serious environmental threat to freshwater lakes and reservoirs. Investigating the dynamics of toxic bloom-forming cyanobacterial genus Microcystis is a challenging task due to its huge spatiotemporal heterogeneity. The hydroacoustic technology allows for rapid scanning of the water column synoptically and has a...

Harmful algal blooms in freshwater reservoirs became a steady phenomenon in recent decades, so instruments for monitoring water quality in real time are of high importance. Modern satellite remote sensing is a powerful technique for mapping large areas but cannot provide depth-resolved data on algal concentrations. As an alternative to satellite te...

Remote characterization and parameterization of gassy sediments have significant environmental importance for quantifying the global methane budget and assessing its impact on climate change. Acoustic techniques that have been developed hold advantages over direct sediment sampling (e.g., using pressurized and frozen cores), as they permit comparat...

Cyanobacteria are notorious for producing harmful algal blooms that present an ever-increasing serious threat to aquatic ecosystems worldwide, impacting the quality of drinking water and disrupting the recreational use of many water bodies. Remote sensing techniques for the detection and quantification of cyanobacterial blooms are required to monit...

The spatiotemporal variability of low- and mid-frequency sound field in the presence of an internal Kelvin wave (IKW) is studied theoretically and in an experiment in the Sea of Galilee, Israel. Measurements of the sound field were carried out using a vertical line array (VLA) of ten hydrophones with 3 m spacing, deployed in the lake’s the deepest...

Cyanobacterial harmful algal blooms (HABs) are increasing in a growing number of aquatic ecosystems around the world due to eutrophication and climatic change over the past few decades. Quantitative monitoring of HABs remains a challenge because their distributions are spatially heterogeneous and temporally variable. Most of the standard biological...

50 days' free access before August 07, 2021 https://authors.elsevier.com/c/1dGJs_V0xP0EGg ............................................................................................................... Outbreaks of cyanobacterial harmful algal blooms present a serious threat to ecosystem safety and human well-being. Removal of toxic cyanobacterial...

In-situ identification of fish species using acoustic methods is a key issue for fisheries research and ecological applications. We propose a novel approach to fish discrimination based on the relationship between target strength frequency response (TS(f)) and vertical swim velocity (VSV), as a proxy of fish body orientation. The measurements were...

1. A deep chlorophyll maximum (DCM) is often seen in stratified freshwater bodies at the interface between an anaerobic layer and an oxic layer. A DCM of the green sulfur bacterium Chlorobium phaeobacteroides was previously reported as a dense population in the oxygen devoid layer of a monomictic stratified lake, Lake Kinneret, Israel. 2. In this m...

• A deep chlorophyll maximum (DCM) is often seen in stratified freshwater bodies at the interface between an anaerobic layer and an oxic layer. A DCM of the green sulfur bacterium Chlorobium phaeobacteroides was previously reported as a dense population in the oxygen devoid layer of a monomictic stratified lake, Lake Kinneret, Israel. • In this mul...

Lakes are 'hotspots' for greenhouse gas (GHG) emissions, primarily carbon dioxide (CO 2) and methane (CH 4). Understanding the processes regulating GHG emissions from lakes, and their temporal variability, is essential for more accurately quantifying the role of lakes in global GHG cycles. In this study, we identified the processes that affect CO 2...

This paper provides estimates of greenhouse gas emissions from a eutrophic monomictic New Zealand lake, Okaro. Monthly monitoring of dissolved CO2 and CH4 concentrations in the lake is used to estimate greenhouse gas emissions at annual time scales. The combination of field research and process-based mathematical modelling in this manuscript provid...

Lakes are ‘hotspots’ for greenhouse gas (GHG) emissions, primarily carbon dioxide (CO2) and methane (CH4). Understanding the processes regulating GHG emissions from lakes, and their temporal variability, is essential for more accurately quantifying the role of lakes in global GHG cycles. In this study, we identified the processes that affect CO2 an...

https://link.springer.com/content/pdf/10.1007/s00367-019-00612-z?utm_source=toc&utm_medium=email&utm_campaign=toc_367_40_4&utm_content=etoc_springer_20200724 ............................................................................... In freshwater lakes, ebullition is an important pathway for biogenic methane (CH4) to escape from sediment and r...

Organic-rich aquatic sediments are a significant source of methane to the atmosphere. In situ remote quantifications of gas content in shallow sediment is a complex task due to its large spatiotemporal heterogeneity. The spatial and multiannual changes of free gas (methane) content (Θ) in shallow sediments were studied in deep subtropical Lake Kinn...

Globally, our knowledge on lake fisheries is still limited despite their importance to food security and livelihoods. Here we show that fish catches can respond either positively or negatively to climate and land-use changes, by analyzing time-series data (1970–2014) for 31 lakes across five continents. We find that effects of a climate or land-use...

How much of the greenhouse gas methane is transported from the seafloor to the atmosphere is unclear. Here, we present data describing an extensive ebullition event that occurred in Eckernförde Bay, a shallow gas-hosting coastal inlet in the Baltic Sea, in the fall of 2014. A weak storm induced hydrostatic pressure fluctuations that in turn stimula...

Nitrogen availability is one of the key factors affecting the dynamics of non-diazotrophic cyanobacterial blooms in eutrophic lakes. While previous studies mainly focused on the promoting effect of nitrogen on the growth of cyanobacteria, this study aimed to investigate the role of nitrogen availability in the downward transport of biomass and its...

Microcystis blooms are a global problem adversely affecting the quality of freshwater in lakes and reservoirs. Surface scum (0–1 m) forms as a result of vertical migration by buoyant Microcystis colonies. Accurate forecasting of bloom and scum development is essential for establishing a reliable alert system and requires understanding the role that...

Large national programs in the United States and several Asian countries have defined and characterised their marine methane hydrate occurrences in some detail, but European hydrate occurrence has received less attention. The European Union-funded project “Marine gas hydrate – an indigenous resource of natural gas for Europe” (MIGRATE) aimed to det...

The spatiotemporal variability of low-and mid-frequency sound field in the presence of internal Kelvin waves (IKWs) was studied in Lake Kinneret (Israel). Experimental measurements of the sound field were carried out using a vertical line array (VLA) consisting of ten hydrophones with 3 m spacing. The VLA was deployed in the deepest (37 m) part of...

Aquatic ecosystems with organic‐rich sediments are a globally significant source of methane to the atmosphere. In shallow waters, ebullition is often a dominant emission pathway of methane. Current knowledge on the processes controlling gas bubble formation and persistence in aquatic sediments is limited. An important prerequisite for accurate quan...

The spatiotemporal variability of low- and mid-frequency sound field in the presence of internal Kelvin waves (IKWs) was studied in the Sea of Galilee. Experimental measurements of the sound field were carried out using a vertical line array (VLA) consisting of ten hydrophones with 3 m spacing. The VLA was deployed in the deepest (37 m) part of the...

Long-term continuous observations of water currents were carried in January 2017-January 2018 with two Acoustic Doppler Current Profilers deployed at the bottom of the Lake Kinneret at 10 and 20 m depth. Results of data analysis are in agreement with suggested existence of coherent mesoscale cyclonic rotation covering the central part of the lake [...

Toxic cyanobacterium Microcystis affects the functioning of aquatic ecosystems and water quality. New remote sensing approaches need to be developed for in situ study of Microcystis bloom development. The aims of our work were to display the advantages of hydroacoustic techniques for in situ studying the gas-containing cyanobacterium Microcystis sp...

Method of estimation of gassy layer parameters in sediment (sound speed and thickness) on the base of measurement of angular and frequency dependencies reflection coefficient of wideband signals is presented. Experiments were carried out in Lake Kinneret (Israel), which is characterized by remarkable organic content in sediment producing methane bu...

Method of upper gassy sediment layer characterization is proposed, based on measurements of angular and frequency dependencies of reflection coefficient, using wideband signals. Experiments were carried out in Lake Kinneret (Israel) with maximal depth ∼ 40 m, where the sediment contains gassy layer. Direct observations of gas void fractions in froz...

Echo intensity data and water current profiles were measured in Lake Kinneret (Israel) with an Acoustic Doppler Current Profiler (ADCP) moored at station H (10 m) and F (20 m) from January to March 2017, i.e. during the winter holomixis and period of winter-spring transient stratification. The collected information allow us to follow the dynamics o...

Toxic cyanobacterial blooms disrupt the functioning of aquatic ecosystems and water use. The main difficulty in monitoring stems from the heterogenic spatial distribution of cyanobacteria. We detected that gas-containing Microcystis colonies are strong acoustic backscatterers at ultrasound frequencies and can be quantified with an echo sounder and...

We analyzed the processes affecting the methane (CH 4) budget in Lake Kinneret, a deep subtropical lake, using a suite of three models: (1) a bubble model to determine the fate of CH 4 bubbles released from the sediment ; (2) the one-dimensional physical lake model Simstrat to calculate the mixing dynamics; and (3) a bio-geochemical model implement...

The spatial distribution of gaseous methane in the top part of the sediment of Lake Kinneret (the Sea of Galilee), Israel is quantified using a novel acoustical methodology. Measurements were carried out with low-frequency sound pulses (200 Hz – 2 kHz) for different depths of the lake along the offshore transects. The methodology is based on the co...

Objective. The hybrid evolutionary algorithm (HEA) has been designed: 1) to represent and forecast multivariate relationships between environmental conditions and population densities by inferential (IF-THEN-ELSE) models, and 2) to quantify 'tipping points' for population outbreaks by IF-conditions (Figure 1). During the course of hundreds of itera...

A series of field experiments were conducted to estimate the effective acoustical properties of the bottom in Lake Kinneret (Israel). A wideband sound source (300 Hz to 2 kHz) was positioned at different ranges (1 m to 6 km) from a single hydrophone. Both local and long-range measurements of the sound field were carried out. All the acoustic data d...

Recent technological developments have increased the number of variables being monitored in lakes and reservoirs using automatic high frequency monitoring (AHFM). However, design of AHFM systems and posterior data handling and interpretation are currently being developed on a site-by-site and issue-by-issue basis with minimal standardization of pro...

Sedimentation is a major process for removal of particulate material and important determinant accounting for the stability of aquatic ecosystems. The fluxes of particulate material are affected by numerous physical, chemical, and biological processes. The resulting patterns of particle deposition to bottom se-diments depend on lake thermal and che...

Large quantities of methane are stored in hydrates and permafrost within shallow marine sediments in the Arctic Ocean. These reservoirs are highly sensitive to climate warming, but the fate of methane released from sediments is uncertain. Here, we review the principal physical and biogeochemical processes that regulate methane fluxes across the sea...

Internal Kelvin waves (IKWs) initiated by rotation of the Earth are one of the main hydrodynamic phenomena in large stratified lakes where baroclinic Rossby radius of deformation is smaller than the horizontal scale of the lake. IKWs can be identified using the spectra of internal waves, where in the presence of IKWs, the inertial frequency is at m...

Lakes play an important role in processing carbon derived from terrestrial ecosystem which in turn accumulate greenhouse gases, namely CO2 and CH4, resulting from biological processes. These accumulated gases are potentially being emitted during lake’s overturn. Nonetheless, rates and balances are still unclear and therefore it limits our forecast...

Ebullition (bubbling) is an important mechanism for the transfer of methane (CH4) from shallow waters to the atmosphere. Due to their stochastic nature, however, ebullition fluxes are difficult to accurately resolve. Hydroacoustic surveys have the potential to significantly improve the spatiotemporal observation of emission fluxes, but knowledge of...

The chapter summarizes current knowledge on fish biology in Lake Kinneret. Nineteen native fish species belonging to six families populate the lake. Three of these species are endemic to the lake and four other species are endemic to the Jordan Valley system. Eight alien species are found in the lake. Four of them are breeding in nature, three can’...

Sedimentation is a major process for removal of particulate material from the water column and important determinant accounting for the stability of aquatic ecosystems. Gross sedimentation rates (GSR) in Lake Kinneret (Israel), regularly monitored from 1999 up-to-date with sedimentation traps, showed salient temporal and spatial variability. In the...

This paper reviews the current knowledge of the heterotrophic and anoxygenic photosynthetic bacteria in Lake Kinneret. Morphological and phylogenetic diversity of bacteria and archaea as well as data from routine total bacterial cell counts are summarized. From 2001 to 2011, there was a definite, significant trend to lower the annual average cell c...

In Lake Kinneret, the majority of photosyntetically produced organic carbon (OC) is cycled through the microbial loop. Taken together, bacterial production (BP) and bacterial respiration (BR), i.e., bacterial carbon demand (BCD), accounted for about 65 % of gross primary production (GPP), measured biweekly and averaging 2.3 g C m-2day-1during the l...

The composition of particulate organic matter (OM) and photosynthetic pigments (signature of specific algal groups) in sedimentation trap were studied in a deep lake. The export of particulate OM and algal material from the upper productive stratum reflects the seasonal succession of algal community and also depend on physical conditions in the lak...