We propose a model for the structure formation of jellyfish swimming based on active Brownian par... more We propose a model for the structure formation of jellyfish swimming based on active Brownian particles. We address the phenomena of counter-current swimming, avoidance of turbulent flow regions and foraging. We motivate corresponding mechanisms from observations of jellyfish swarming reported in the literature and incorporate them into the generic modelling framework. The model characteristics is tested in three paradigmatic flow environments.
Submarine groundwater discharge (SGD) has been shown to be an important source of nutrients in co... more Submarine groundwater discharge (SGD) has been shown to be an important source of nutrients in coastal environments, especially nitrogen and silica, and thereby relive nutrient limitation to phytoplankton. Here, we followed autotrophic microbial biomass, activity, and community composition at a site strongly influenced by SGD and a nearby nutrients-poor reference site at the oligotrophic Israeli shallow rocky coast [southeastern Mediterranean Sea (SEMS)] between 2011 and 2019. The surface water at the SGD-affected area had significantly higher NO3 + NO2 (∼10-fold) and Si(OH)4 (∼2-fold) levels compared to the reference site, while no significant differences were observed for PO4 or NH4. This resulted in a significant increase in algae biomass (∼3.5-fold), which was attributed to elevated Synechococcus (∼3.5-fold) and picoeukaryotes (∼2-fold) at the SGD-affected site, and in elevated primary production rates (∼2.5-fold). Contrary to most SGD-affected coastal areas, diatoms biomass rem...
Accumulation of nanoplastics (NPs) in the environment has raised concerns about their impact on h... more Accumulation of nanoplastics (NPs) in the environment has raised concerns about their impact on human health and the biosphere. This study sheds light on the mechanism whereby NPs are captured by mucus extracted from the jellyfish Aurelia sp. The efficacy of the mucus to capture polystyrene and acrylic NPs (~100 nm) from spiked wastewater treatment plant (WWTP) effluent was systematically evaluated and benchmarked against mucus from other organisms and conventional WWTP coagulants. The mucus effect on capture kinetics and destabilization of NPs of different polymer compositions, sizes and concentrations was quantified by means of fluorescent NPs, dynamic light scattering and zeta potential measurements and visualized by scanning electron microscopy. Addition of Aurelia sp. mucus led to a rapid (<10 min) and significant removal of NPs (60-90%) from a stable suspension. The jellyfish mucus outperformed all other mucus types (0-37%) and coagulants (0-32% for ferric chloride; 23-40% for poly aluminum chlorohydrate), highlighting the potential for jellyfish mucus or mucus components to be utilized as an improved bio-flocculant. Further insight is provided by carbohydrate composition analysis and protein disruption tests. Total protein disruption resulted in a complete loss of the mucus capacity to capture NPs, whereas breaking the disulfide bonds and unfolding the proteins resulted in improved capture capacity. The results indicate a mucus-particle interaction consisting of adsorption-bridging and "mesh" filtration (capture).
Aquaponics is an emerging industry promoted as a sustainable agricultural practice. Economic sust... more Aquaponics is an emerging industry promoted as a sustainable agricultural practice. Economic sustainability of aquaponics is challenging, partly because some of the benefits are external to the grower, necessitating public intervention to support the industry. We used life cycle assessment to estimate the environmental impact of a proposed aquaponic system and applied a set of economic valuation methods to assess the costs of identified impact factors. We found that the system, planned to produce 60,000 ornamental fish and 108,000 lettuce heads per year would impact the environment with a cost of 10,700 EUR annually, about half the environmental cost of separate production of the same produce. Most of the external cost can be attributed to the industrial processes that prepare products used for aquaponic production. Although this method provides only a rough estimate of actual system impact, it can potentially be used to assess the cost-effectiveness of aquaponics from an environmental perspective.
Jellyfish (JF) swarms impact human wellbeing and marine ecosystems. Their global proliferation is... more Jellyfish (JF) swarms impact human wellbeing and marine ecosystems. Their global proliferation is a matter of concern and scientific debate, and the multitude of factors affecting (and affected by) their density and distribution merits long-term monitoring of their populations. Here we present an eight-year time series for Rhopilema nomadica, the most prominent JF species swarming the Eastern Mediterranean Sea. Reports were submitted by the public and within it a group of trained participants via an internet website between June 2011 and June 2019. Data collected included species, size, location, ranked amount and stinging. Swarms of R. nomadica prevailed in July and ended in August but were also prominent in winter from January to March. Both observations deviate from past swarming patterns described in the late 1980s, when summer swarms persevered until October and winter swarms were not documented. Climate change (increasing water temperature) and the westwards up-current spread ...
Seasonal sea surface microplastic distribution was recorded at 17 sites along the Israeli Mediter... more Seasonal sea surface microplastic distribution was recorded at 17 sites along the Israeli Mediterranean coast. Microplastics (0.3-5mm) were found in all samples, with a mean abundance of 7.68±2.38particles/m(3) or 1,518,340particles/km(2). Some areas had higher abundances of microplastics than others, although differences were neither consistent nor statistically significant. In some cases microplastic particles were found floating in large patches. One of these patches contained an extraordinary number of plastic particles; 324particles/m(3) or 64,812,600particles/km(2). Microplastic abundances in Israeli coastal waters are disturbingly high; mean values were 1-2 orders of magnitude higher than abundances reported in other parts of the world. Light-colored (white or transparent) fragments were by far more abundant than all other microplastic colors and types. The results of this study underline the need for action to reduce the flux of plastics to the marine environment.
We propose a model for the structure formation of jellyfish swimming based on active Brownian par... more We propose a model for the structure formation of jellyfish swimming based on active Brownian particles. We address the phenomena of counter-current swimming, avoidance of turbulent flow regions and foraging. We motivate corresponding mechanisms from observations of jellyfish swarming reported in the literature and incorporate them into the generic modelling framework. The model characteristics is tested in three paradigmatic flow environments.
Submarine groundwater discharge (SGD) has been shown to be an important source of nutrients in co... more Submarine groundwater discharge (SGD) has been shown to be an important source of nutrients in coastal environments, especially nitrogen and silica, and thereby relive nutrient limitation to phytoplankton. Here, we followed autotrophic microbial biomass, activity, and community composition at a site strongly influenced by SGD and a nearby nutrients-poor reference site at the oligotrophic Israeli shallow rocky coast [southeastern Mediterranean Sea (SEMS)] between 2011 and 2019. The surface water at the SGD-affected area had significantly higher NO3 + NO2 (∼10-fold) and Si(OH)4 (∼2-fold) levels compared to the reference site, while no significant differences were observed for PO4 or NH4. This resulted in a significant increase in algae biomass (∼3.5-fold), which was attributed to elevated Synechococcus (∼3.5-fold) and picoeukaryotes (∼2-fold) at the SGD-affected site, and in elevated primary production rates (∼2.5-fold). Contrary to most SGD-affected coastal areas, diatoms biomass rem...
Accumulation of nanoplastics (NPs) in the environment has raised concerns about their impact on h... more Accumulation of nanoplastics (NPs) in the environment has raised concerns about their impact on human health and the biosphere. This study sheds light on the mechanism whereby NPs are captured by mucus extracted from the jellyfish Aurelia sp. The efficacy of the mucus to capture polystyrene and acrylic NPs (~100 nm) from spiked wastewater treatment plant (WWTP) effluent was systematically evaluated and benchmarked against mucus from other organisms and conventional WWTP coagulants. The mucus effect on capture kinetics and destabilization of NPs of different polymer compositions, sizes and concentrations was quantified by means of fluorescent NPs, dynamic light scattering and zeta potential measurements and visualized by scanning electron microscopy. Addition of Aurelia sp. mucus led to a rapid (<10 min) and significant removal of NPs (60-90%) from a stable suspension. The jellyfish mucus outperformed all other mucus types (0-37%) and coagulants (0-32% for ferric chloride; 23-40% for poly aluminum chlorohydrate), highlighting the potential for jellyfish mucus or mucus components to be utilized as an improved bio-flocculant. Further insight is provided by carbohydrate composition analysis and protein disruption tests. Total protein disruption resulted in a complete loss of the mucus capacity to capture NPs, whereas breaking the disulfide bonds and unfolding the proteins resulted in improved capture capacity. The results indicate a mucus-particle interaction consisting of adsorption-bridging and "mesh" filtration (capture).
Aquaponics is an emerging industry promoted as a sustainable agricultural practice. Economic sust... more Aquaponics is an emerging industry promoted as a sustainable agricultural practice. Economic sustainability of aquaponics is challenging, partly because some of the benefits are external to the grower, necessitating public intervention to support the industry. We used life cycle assessment to estimate the environmental impact of a proposed aquaponic system and applied a set of economic valuation methods to assess the costs of identified impact factors. We found that the system, planned to produce 60,000 ornamental fish and 108,000 lettuce heads per year would impact the environment with a cost of 10,700 EUR annually, about half the environmental cost of separate production of the same produce. Most of the external cost can be attributed to the industrial processes that prepare products used for aquaponic production. Although this method provides only a rough estimate of actual system impact, it can potentially be used to assess the cost-effectiveness of aquaponics from an environmental perspective.
Jellyfish (JF) swarms impact human wellbeing and marine ecosystems. Their global proliferation is... more Jellyfish (JF) swarms impact human wellbeing and marine ecosystems. Their global proliferation is a matter of concern and scientific debate, and the multitude of factors affecting (and affected by) their density and distribution merits long-term monitoring of their populations. Here we present an eight-year time series for Rhopilema nomadica, the most prominent JF species swarming the Eastern Mediterranean Sea. Reports were submitted by the public and within it a group of trained participants via an internet website between June 2011 and June 2019. Data collected included species, size, location, ranked amount and stinging. Swarms of R. nomadica prevailed in July and ended in August but were also prominent in winter from January to March. Both observations deviate from past swarming patterns described in the late 1980s, when summer swarms persevered until October and winter swarms were not documented. Climate change (increasing water temperature) and the westwards up-current spread ...
Seasonal sea surface microplastic distribution was recorded at 17 sites along the Israeli Mediter... more Seasonal sea surface microplastic distribution was recorded at 17 sites along the Israeli Mediterranean coast. Microplastics (0.3-5mm) were found in all samples, with a mean abundance of 7.68±2.38particles/m(3) or 1,518,340particles/km(2). Some areas had higher abundances of microplastics than others, although differences were neither consistent nor statistically significant. In some cases microplastic particles were found floating in large patches. One of these patches contained an extraordinary number of plastic particles; 324particles/m(3) or 64,812,600particles/km(2). Microplastic abundances in Israeli coastal waters are disturbingly high; mean values were 1-2 orders of magnitude higher than abundances reported in other parts of the world. Light-colored (white or transparent) fragments were by far more abundant than all other microplastic colors and types. The results of this study underline the need for action to reduce the flux of plastics to the marine environment.
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Papers by Dror Angel