Nitrogen and Phosphorus Removal from Lake Kinneret Inputs

The Hula Valley was drained in 1957. The land use was modified from natural wetland and old shallow lake ecosystems to agricultural development. About half of the drained land area was utilized for aquaculture. Population size was enhanced and the diary was developed intensively resulting in the enhancement of domestic and husbandry sewage production that increased as well. The natural intact Hula Valley-Lake Kinneret ecosystem was heavily anthropogenically interrupted: The Hula was drained and Kinneret became a national source for domestic water supply. Some aspects of the environmental and water quality protection policy of the system are presented. The causation and operational management implications for the reduction of Nitrogen and Phosphorus migration from the Hula Valley are discussed. Drastic (81%) restriction of aquaculture accompanied by sewage totally removed achieved a reasonable improvement in pollution control which was also supported by the Hula Project. The implications of anthropogenic intervention in the process of environmental management design are presented.

The Impact of Hula Project (1993-2018) on Nutrient Migrations

During the 1950s the Hula wetlands and old lake were drained and the land converted utilization to agriculture and ecotourism. As a result of the drainage, the Peat Soil was exposed to atmospheric oxygen. The geochemical environment was modified from reductive to oxidative and the Nitrogen in it was converted from Ammonium to Nitrate. Intensive migration of Nitrate from the Hula Valley induced a national concern of water quality deterioration in the lake which was dissipated when Nitrogen deficiency was developed in Lake Kinneret. Forty years after drainage the ecosystem structure was renovated (Hula Project, HP) aimed at agricultural management and nutrient migration reduction. The paper examines through evaluation of the ecological data record (1993-2018) the impact of hydrological changes, attributed to the HP implementation on nutrient dynamics within surface waters in the Hula Valley. It is suggested that soil moisture elevation by irrigation in summer reduced Phosphorus and enhanced Nitrate concentrations.

The Peat-Organic-Soil in the Hula Valley

The main soil type, principle contributor of nutrients and available agricultural land in the Hula Valley is the organic Peat. Nevertheless, the relative contribution of Phosphorus from the Hula Valley to the Lake Kinneret inputs is lower than regional outsourcing. The Nitrogenic matter, mostly Nitrate migration from the Peat soil is significant. The implementation of efficient development is the key factor of Hula Land use. The financial beneficial success of the Hula land use is therefore dependent of Peat soil properties. The porosity of the Peat Soil is high and preferential pathway volume is low and Hydraulic Conductivity is therefore low. Consequently, the Mobile Spray Irrigation line was found as most suitable for cultivation in Peat Soil. Enhancement of Summer irrigation creating moisture elevation reduces Phosphorus migration from Peat Soil and is therefore recommended and recently implemented.

Chemical, Hydrological and Climatological Properties of Lake Agmon, Hula Valley (Israel), (1994-2006)

The first decade of monitoring program in Lake Agmon (Hula Valley, Northern Israel) is summarized. The presented part of the program include: water discharges, physico-chemical (pH, EC, Temperature) and chemical parameters (TP, TN, TDN, TDP, NO3, NH4, SO4, TDS, TSS,). It was found that Nitrogen concentrations decline from north to south and the opposite for Phosphorus. Resulting of re-suspension by wind direction of western-southern-eastern and averaged maximal velocities of 9 - 10 m/s is suggested. De-nitrification and particles sedimentation emphasize Lake Agmon as a sink for Nitrogen. Sulfate-Carbonates association and the production of precipitated Gypsum (CaSO4) highlight the sink property of Lake Agmon. Nevertheless Sulfate removal by the Lake Agmon hydrological system is significant.

The Impact of Available Nitrogen Deficiency on Long-Term Changes in the Lake Kinneret Ecosystem

Lake Kinneret Ecosystem structure has undergone significant modification since early 1990s. Scientists have indicated several causative factors for those long-term changes. The sharp decline of Peridinium and the upset of Cyanobacteria are the major changes. Several options were suggested as the reason for those changes. Among others are the followings: high amplitude of water level fluctuations, global warming, fisheries management, salts diversion, onset and offset of beach vegetation, anthropogenic operations in the drainage basin, allelopathic trait of algal competition, etc. It was suggested that the reduction of ammonia supply from the Hula Valley resulted in the conversion of the land from lake and swamps covered to agriculture followed by elimination of treated domestic sewage and fishponds effluents enhanced deficiency of available N in Lake Kinneret. This paper evaluates the impact of available Nitrogen decline which enhanced Kinneret ecosystem modifications.

Competitive Consumption of the Lake Kinneret (Israel) Plankton by <i>Hypophthalmichthys molitrix</i>and <i>Sarotherodon galilaeus</i>

An outdoor tank experiment was carried out for the assessing of the impacts of Sarotherodon galilaeus (Galilee Saint Peter’s Fish;Cichlidae) (SG) and Hypophthalmichthys molitriox (Silver Carp;Cyprinidae) (SC) on Lake Kinneret (Israel) plankton. In order to evaluate the interaction effect, the experiments were of replicated 2 × 2 factorial design: TG × SC. A lot of interaction effects were indicated showing that the effects of the two fishes were not independent and potentially competitors. SG suppressed most crustaceans and rotifers while increasing gross and net primary production and chlorophyll concentration. SC had less intense effects on zooplankton than SG. Although SC suppressed most crustaceans and rotifers, it had less interaction effects than SG. SC had no statistically significant effects on phytoplankton production or chlorophyll concentration. It is suggested that these experiments indicate that although the plankton community impacts of SG and SC do differ, both fishes utilize similar food resources in Lake Kinneret. Fingerlings of SG and SC are planted in Lake Kinneret annually aimed at the improvement of fishermen’s income and prevention of water quality deterioration. SC is known as efficient consumer of Microcystis. It is therefore recommended to limit SC introduction to periods when Microcystis is abundant.

The Impact of Turbidity on Zooplankton Densities in Lake Kinneret (Israel)

Spatial survey of zooplankton community composition within the upper 10 m layer in Lake Kinneret was carried out. Samples were collected by plankton net (63 μ mesh size) and counted organisms were sorted by 2 groups: 1) Large-including Copepodite and adult Cyclopoid copepods and Cladocerans;2) Small nauplii and rotifers. It was found that in the northern part of the lake where turbidity is high, the density of small organisms is relatively lower, and in other parts of the lake where water is less turbid, large organisms are relatively less abundant. Speculative assumption about the impact of fish feeding behavior on that is presented.

Ecophysiology of Lake Kinneret (Israel) Zooplankton

A summary of a long-term research of Lake Kinneret zooplankton distribution is presented. During 1969-2002 several prominent changes have been recorded in the Kinneret ecosystem. This paper is an attempt aimed at analyzing the impact of these ecological changes on the zooplankton communities. The impacts of Phytoplankton, Bacteria, Protozoa, Temperature, Nutrient composition and fish predation on zooplankton dynamics are analyzed. It was found that periodical fluctuations of zooplankton density were mostly affected by fish predation as well as by temperature increase and food availability. Ecological conditions in Lake Kinneret have been modified since early 1990’s and the new conditions were consequently accompanied by zooplankton Homeostatic response. Moreover, as a result of the ecological changes fish intensified their pressure on zoo-plankton. The flexibility of food resource preference by zooplankton enabled its existence but fish predation predominantly controlled their density.

The Impact of Nitrogen and Phosphorus Dynamics on the Kinneret Phytoplankton: II: Chlorophyta, Cyanophyta, Diatoms and Peridinium

Lake Kinneret long-term data of the epilimnetic concentrations (ppm) and loads (tones) of the total Nitrogen (TN), total Phosphorus (TP), total inorganic Nitrogen (TIN), total Dissolved Phosphorus (TDP), Phytoplankton groups’ biomass, water level (WL) and Jordan River Discharge were analyzed. Previously collected data compiled aimed at an insight into the causative background for the modification of Phytoplankton community change. The study was carried out by searching for relations between algal groups’ densities and nutrient conditions in the Epilimnion by the use of statistical methods (Simple and Fractional Polynomial Regressions). The study is aimed at analyzing the relations between algal biomass and nutrient contents. It was found that Nitrogen decline and slight increase of phosphorus were followed by Peridinium (Photo 1)?decline and biomass increase of non-peridinium algae. It is suggested that nitrogen supply for algal growth is mostly from external sources, and the reduction of nitrogen in the epilimnion was caused by external removal. Contrary to nitrogen, phosphorus sourcing is only partly external (dust deposition, drainage basin) and mostly internal through double channels: Microbial mineralization of bottom sediments and Peridinium cysts mediation. The resulted complexity of the Kinneret ecosystem structure is nitrogen limitation, and enhancement of Non-peridinium algal growth, mostly Cyanobacteria.

The Impact of Nitrogen and Phosphorus Dynamics on the Kinneret Phytoplankton: I: Cyanophytes-Peridinium Alternate

During 1970-2001, several ecological changes were documented in the Lake Kinneret Ecosystem: Decline of total Nitrogen (TN) and increase of total Phosphorus (TP) loads with a corresponding decline of TN/TP ratio. The phytoplankton assemblages indicated consequence Increase of Cyanobacteria accompanied by elevation of the biomass of Chlorophyta and Diatoms. The Kinneret ecosystem functioning represented two superimposed events: the decline of TN enhanced Cyanobacteria and elevation of TP that was reflected by an increase of Chloropytes and Diatoms. Removal of Nitrogen was achieved but P load remained high enough to enhance Chlorophyta and Diatoms. Consequently, a top priority of future management perspective should be reduction of Phosphorus inputs.

Fish-Zooplankton—A Predator-Prey Relations as a Key Factor for the Design of Zooplankton Distribution Sampling Program in Lake Kinneret, Israel

Long-term data record of Kinneret Epilimnetic Zooplankton biomass distribution and fish stock assessment was analyzed. The objective is aimed at defining the representativeness of the present sampling stations distribution for the measure of the entire Lake Kinneret zooplankton biomass. Previous studies documented the preeminence of temperature and fish predation impacts on zooplankton density: water temperature through growth rate trait and fish predation. Acoustic surveys indicated that fish shoals are mostly inhabiting the Peripheral region and much less the central part of the Kinneret pelagial. Due to fish zooplanktivory, densities of planktonic crustacean in the Pelagial periphery presented by 5 - 7 sampling stations are low. Nevertheless, large central lake area with higher densities of zooplankton biomass is presented by only one station. Therefore, stations average is incorrect as is total lake measure. The average result as indicated presently as total zooplankton biomass in lake Kinneret is, therefore, underestimated. Two optional corrective suggestions are concluded: 1) Additional sampling stations in the central part of the Pelagial region;2) Usage of station value of aerial coefficient (promoter).

Land-Use, Albedo and Air Temperature Changes in the Hula Valley (Israel) during 1946-2008

Long-Term (1946-2008) record of 35,580 measurements of daily mean air temperatures in three meteorological stations (Dan, Dafna, Kfar Blum) in the Hula Valley, within the drainage basin of Lake Kinneret (Israel) was statistically evaluated. Temperature decline after the drainage of the old Lake Hula and adjacent wetlands (1958) and increase from the mid 1980’s, after the implementation of the Hula Project aimed at continuous land green cover were verified. It was suggested that those regional climate changes were due to the change of Albedo levels: lower when land was water covered and higher after regional drainage followed by a decline when vegetation cover became intensive and continuous. Decline of Albedo levels led to higher air temperature and vice versa.

On The Biology of Tilapia zillii (Gervais1848) in Lake Kinneret (Israel)

Fish (mostly Tilapia zillii), (TZ), mass mortality in Lake Kinneret initiated a study of the biology of TZ in Lake Kinneret. The study included several aspects: spawning and nesting behavior, feeding habits, the status of TZ in the Kinneret fishery and temperature tolerance. The merit of TZ to commercial landing fishery is negligible, but this specimen is one of the most common fishes in the lake. Several environmental factors are considered as promoters of the epilimnetic temperature decline: Jordan water inputs in winter season as a heat source parameter. ENSO (EL-NI&#209O/Southern Oscillation) acts as a cooling enhancement factor. Supportive data on the impact of ENSO were found in two terrestrial agricultural monitors in the northern and southern parts of the drainage basin. Gut content analysis of young fingerlings and an adult TZ specimen, indicated the significant contribution of benthic sources which are common in the shallows. The great adaptive capabilities of breeding TZ with various bottom habitats are demonstrated.

Population Dynamics of Cyclopoid Copepods in Lake Kinneret (Israel)

Reports on the Kinneret zooplankton in general and particularly on copepods are dealing recently with numerical densities of feeding habit classes. Nevertheless, for the evaluation of the integrated role of copepod assemblages in the entire lake ecosystem, their life cycle stages fluctuations are essential. It was not done in previous reports. Therefore, long term analysis of the cyclopoid copepods life stages dynamics in Lake Kinneret was carried out. Due to information availability, two complementary methods of density concentrations were evaluated for two consecutive data sets: 1) 1969-1985 numerical (No/L) documentation of life cycle stages of nauplii (I - III and III - V), copepodites (I, II, III, IV, V) and adults;2) 1969-2002 monthly averages of wet biomass density (g/m2) of zooplankton major groups combined with metabolic rates. nauplii densities represent June-August peaks and older stages spring decline and high levels during summer-early winter. Polynomial Regressions between Numerical annual averages of predator and Herbivore stages as well as young vs. older life stages indicate significant relations. During winter-spring season, temperatures are optimal for cyclopoid growth as a result of the high efficiency of metabolic activity and the low pressure of fish predation. The high rate of metabolism and intensive fish predation in summer enhance low densities of adult cyclopoids.

The Impact of EL-NINO/Southern Oscillation (ENSO) on Fishery and Water Quality in Lake Kinneret (Israel)

A correlation between fishery and extreme winter conditions in Lake Kinneret was indicated: po pulations of Bleak fishes were enhanced and those of Sarotherodon galilaeus (SG) declined. The aim of the present study is to confirm the relation of those correlations to EL-NINO/Southern Oscillation and its impact on Kinneret fishery. The study is based on long-term data records of the Kinneret Epilimnetic temperatures, water level increase, precipitation and air temperatures in the drainage basin, together with a record of EL NINO/Southern Oscillation (ENSO) events. Results suggest a confirmation of the impact of ENSO events on lake population size of Bleaks and SG. It is likely that the influence of ENSO on the two key fish species in the Lake is contradictory: enhancement of reproduction of the winter spawner Bleaks and reduction of population recruitment of the early summer spawner, Sarotherodon galilaeus. It is likely that winter extreme in Kinneret region is a consequence of ENSO event and therefore negatively affecting Kinneret water quality.

Limnological Changes in the Lake Kinneret (Israel) Ecosystem: The Beginning and Its Significance

The Lake Kinneret (Israel) ecosystem has undergone limnological changes. The trend of changes started in the mid 1990’s. The deviation from the previously known as stable long-term structure of the ecosystem included, among others, phytoplankton community structure, nutrient dynamics, zooplankton densities, water temperature increase, water level decline, and fishery management. This study is aimed at identifying ecosystem stability by focusing on three major compartments of the ecosystem: Total Dissolved Solids (TSS), Plankton (Phyto and Zoo), and Detritus (TSS minus plankton). It is suggested that although significant temporary changes of biotic and abiotic parameters were recorded and despite the existence of the normal seasonal fluctuations, the major compartments’ structural relations were not modified. The objective of the study is to analyze the process initiation of the modification trend. Previous studies and reports were focused on descriptive evaluation of the modified parameters. The expected outcome is a comprehensive evaluation of the modification process. Consequently, resulted prediction might be a tool for managers to improve management design.

A Review on Modeling of Kinneret Salinity with Practical Recommendations

Two models have been developed for the evaluation and prediction of salinity changes (chloride concentration;ppm;[Cl]) in Lake Kinneret. They are: 1) RM, which is based on the Salt balance and hydrological budget of the lake;2) GM which is based on the geo-hydrological regional properties of Kinneret’s geological structure. The concept of both is partly different: RM is correlating reduction of runoffs to salinity elevation and GM relates salt flux to the aquifer yield and the impact of lake water level is neglected. Long term statistical analyses justify support to GM, excluding conditions of heavy floods. This paper is a combination of a supplemental extended temporal study and a models review. Practical conclusions on Kinneret hydrological management within a frame of constrains aimed at prevention of salinity and eutrophication increase are presented.

Regulated Fishery Is Beneficial for the Sustainability of Fish Population in Lake Kinneret (Israel)

Analysis of long-term data-sets of limnological and ichthyological features of the Lake Kinneret ecosystem structure revealed evidence that the decline of fish landings during 2007-2008 was not an unpredicted crisis and included only Tilapias, and mostly S. galilaeus. Several factors were found to be responsible for the decline and recovery afterwards: decline of stocking, enhancement of population size of food competitors (Bleaks), the use of smaller mesh size of fishing nets, increase of predation pressure by Cormorants, the burst of Viral Disease, natural cyclic oscillation of ENSO event and its higher frequencies and intensities during the 2000’s. Therefore, recommendations aimed at ceased fishing are not justified and fishery continuation is correct: renewal of Bleaks fishing effort, improvement of fishing legislations, enforcement and management of fish stocking, and efficient implementation of Cormorants deportation.

Experimental Study in Out-Door Tanks of N and P Uptake by the Aquatic Communities of Lake Kinneret

Two trials (1st Trial-46 and 2nd Trial-64 hrs duration) experiment in 8 out-door tanks (5 m3) were carried out with similar design: 4 fish densities (0, 1, 5, and 10), 2 densities of zooplankton (high and low) and 4 increasing levels of P and N concentrations of nutrient enrichments. The consecutive changes of N and P concentrations were measured at 3 (Trial 1) and 4 (Trial 2) time intervals. It was found that nutrient uptake of the entire community, which is the differences between initial and final concentrations, was mostly affected by the initial enrichment. The ecological implications are discussed.

Climate Change, Regional Water Balance and Land Use Policy, in the Watershed of Lake Kinneret (Israel)

Long term data record (1944-2018) of climatological conditions in the Lake Kinneret and its watershed ecosystems was statistically evaluated and the impact of Anthropogenic operations was included as well. Precipitation input source is obviously uncontrolled natural component whilst the other three regional water outflows pathways are under anthropogenic control: Evapo-transpiration (ET), Runoff and underground flows. Indications for climate change expressed as air warming with consequences on regional (watershed and the lake) water resources and consumption capacities policy in the drainage basin and in the Lake are discussed. The decline of air temperature from 1940 to 1970s is probably due to a change in the Albedo effect. After the decline air temperature was twisted towards elevation. Climate change caused a decline in rainfall, followed by a reduction of Jordan and other river discharges and underground flows, accompanied by a decline of WL. With respect to climate change, water allocation for agricultural consumption was shrunk.