Explore the vast range of titles available.

A significant change to the land cover in the Hula Valley was carried out during the 1950s: A swampy area densely covered by aquatic vegetation and the old shallow lake Hula were drained. The natural shallow lake and swamps land cover were converted into agricultural development land use in two stages: (1) Drainage that was accomplished in 1957; (2) Implementation of the renovated hydrological system structure, including the newly created shallow Lake Agmon-Hula (LAH), was completed in 2007. The long-term data record of the restored diversity of the submerged and emerged aquatic plant community, and its relation to water quality in the newly created shallow Lake Agmon-Hula LAH, was statistically evaluated. Internal interactions within the LAH ecosystem between aquatic plants and water quality, including nitrification, de-nitrification, sedimentation, photosynthetic intensity, and plant biomass and nutrient composition, were statistically evaluated. The plant community in LAH maintains a seasonal growth cycle of onset during late spring–summer and dieback accompanied by decomposed degradation during fall–early winter. The summer peak of aquatic plant biomass and consequent enhancement of photosynthetic intensity induces a pH increase during daytime and carbonate precipitation. Nevertheless, the ecosystem is aerobic and sulfate reduction and H2S concentration are negligible. The Hula reclamation project (HP) is aimed at the improvement of eco-tourism’s integration into management design. The vegetation research confirms habitat enrichment.

The natural ecosystem of the Hula Valley (Israel) comprising shallow old lake Hula, swamps and partly cultivated land was altered by drainage. The drained area was converted for agricultural development. The natural wetland–lake ecosystem was demolished. A reduction in biodiversity and a negative impact on the downstream Lake Kinneret water quality were predicted. Forty years later, a reclamation project was implemented aimed at renovation of the hydrological conditions, and agricultural development was improved. The recorded inventory of plants, birds and fish pre- and post-drainage and reclamation was comparatively evaluated resulting in an indication of Biodiversity Index (BDI) and Species Richness (SR) enhancement in the present. It is suggested that the resulting increase in ecological habitat varieties suitable for terrestrial, semi-aquatic and aquatic organisms enhanced the biodiversity. Nevertheless, it is not impossible that the newly created conditions which enhanced the biodiversity require a risk assessment to ensure the long-term sustainability of the integration of agriculture and nature.

A long-term (1933–2022) record of water level (WL) fluctuations in Lake Kinneret was reviewed. The dependence of the Kinneret WL management on climate change (flood–dryness alternate), dam and National Water Carrier (NWC) constructions constrained by water availability and domestic supply demands were indicated. A short-term range of maximal WL decline of 4–6 m and 4.6–6.5% of the total surface area of lake water shrinkage in Lake Kinneret was documented. Nevertheless, incomparably longer periods and higher amplitudes of WL decline accompanied by a dramatic shrinking of the water surface were documented in Lake Tchad, the Aral Sea and Lake Sivan (SAT). Therefore, the comparative results of WL decline in Lake Kinneret and in other lakes as SAT are not justified.

The objective of this study is re-evaluation of the long-term record of limnological parameters in Lake Kinneret (1970–2018) and its drainage basin (1940–2018) aimed at an indication of the possible impact of climate change on water quality in Lake Kinneret. The methodological approach is based on indication of significant changes, of temperature increase, decline in rainfall, causing a reduction in river discharges, and lake water inflows. These climatological changes were accompanied by a reduction in nitrogen and a slight increase in phosphorus in the lake Epilimnion. The outcome was Epilimnetic Nitrogen deficiency and Phosphorus sufficiency, which enhanced domination replacement of Peridinium spp. by Cyanobacterial. We concluded sequel suggested climate change affected water quality deterioration in Lake Kinneret.

Long-term records of Water Level Fluctuations (WLF) and nutrient dynamics in Lake Kinneret have indicated an independence between them. The winter’s high WLF with nutrient-rich conditions and the summer’s low WLF with nutrient-poor conditions are recurrent states. Are Water Level Fluctuations and Lake Kinneret’s pelagic water quality related directly or indirectly? Overall, the results found that WLF and nutrient dynamics in the pelagic zone of Lake Kinneret are not co-partners, but independent escorts. The common periodical (monthly) distribution of nutrient concentrations in the epilimnion of Lake Kinneret indicates that a 20 m deep epilimnion formed following a decline in water input, temperature, and evaporation elevation, resulting in the decline of WL. There was a seasonal correlation between summer’s natural conditions and pelagic nutrients’ deficiency. Low WL in summer is the result of natural subtropical climate conditions, whilst dry or high rainfall seasons induce water input modification and consequently, the WL decline of nutrient inputs and independent followers.

A comprehensive compilation of long-term data records about the dynamics of nutrient migration and availability in the Kinneret epilimnion was statistically evaluated. A replacement of Peridinium spp. domination by cyanobacteria in Lake Kinneret (Israel) was documented. Nitrogen outsourcing is a significant factor within the Kinneret ecosystem structure. Part of the Kinneret watershed, the Hula Valley, which was covered by a shallow lake and swampy wetlands was drained. The result was the conversion of the nitrogen supply, as ammonium and organic forms, into nitrate. Nevertheless, nutrients supplied from aquaculture (fish ponds) and raw sewage partly compensated for the ammonium deficiency. After sewage removal and fish pond restrictions (the early 1990s), the majority of nitrogen migration became nitrate, dependent on climate conditions (rainfall, river discharges). The preference for ammonium by the bloom-forming Peridinium spp. caused a reduction in the efficiency of nitrogen utilization and cyanobacteria replaced phytoplankton for domination.

The Hula Valley in northern Israel was partly covered by swamps and a shallow lake. The entire valley was drained and converted for agricultural cultivation. Later, an additional soil reclamation operation was implemented, including eco-tourism. From the early 1990s, winter migratory cranes have attracted visitors, thus supporting the hydrological management of the entire valley that protects the downstream Lake Kinneret. It was documented that these birds have a minor impact on phosphorus pollution, but severely damaged agricultural crops are protected by mild deportation and daily, short, periodical corn seed feeding.

The long-term record of ecological, limnological and climatological parameters that were documented in the Kinneret drainage basin was statistically evaluated. The dependent relations between environmental parameters and a change in climate conditions open a consequence dispute between three optional definitions: long-term instability, climate change impact and ecosystem resiliency. The Kinneret drainage basin during the Anthropocene era is marked by intensive anthropogenic involvement: Increase in population size, drainage of the wetlands and old lake Hula, agricultural development, enhancement of lake Kinneret utilization for water supply, hydrological management, fishery and recreation. Therefore, the impact of a combination of natural and anthropogenic environmental factors confounded each other, and the uniqueness of climate change is unclear.

Since the mid-1980s, significant changes in climate conditions have occurred, and trends of dryness in the Kinneret drainage basin have been documented, including a temperature increase and precipitation decline. The precipitation decline, and consequently the reduction in river discharge, resulted in a decrease in TP (total phosphorus) flux into Lake Kinneret. After the drainage of the Hula natural wetlands and old Lake Hula during the 1950s, the ecological characteristics of the Hula Valley were modified. Nutrient fluxes downstream into Lake Kinneret were therefore predicted. The impacts of climate conditions (precipitation and discharge) on TP (total phosphorus) outsourcing through erosive action are significant: higher and lower discharge enhances and reduces TP load, respectively. The total TP flushing range from the Hula Valley peat soil through the subterranean medium and where TP is directed are not precisely known but are probably outside Lake Kinneret. Most runoff water and mediated TP originates from bedrock through erosive action. Long-term records of TP concentrations in headwaters and potential resources in the Hula Valley confirmed the significant influence of climate conditions on the outsourcing of TP capacity. The impacts of agricultural development, external fertilizer loads and migratory cranes in the winter are probably insignificant.

Seasonal variations in the carbon isotope composition of components of the pelagic food web in Lake Kinneret were recorded and compared with those recorded for bulk plakton from the lake in the early 1970s. Individual planktonic components as well as bulk plakton were isotopically lightest shortly after overturn in January and heaviest in May, after the peak of the annual bloom of the dinoflagellate Peridinium gatunense. The range of $\\delta^13C$ values observed over an annual cycle and the annual and seasonal means varied considerably between taxa. Within the primary producers, P. gatunese (rage, -23.2 to -17.9%.) was significantly $^13C-enriched$ relative to concurrent nanoplankton (-27.4 to -19.0%.). Zooplankton $\\delta ^13 C$ showed indistinct taxon-specific differences but greater seasonal variation (-33.8 to -19.8%.) than any phytoplankton component examined. Adult fish exhibited smaller $\\delta ^13 C$ of variability than the planktonic components. End-memberisotope compositions confirmed the linkages nanoplankton \\rightarrow Zooplankton \\rightarrow Kinneret sardines, and Peridinium \\rightarrow Sarogherodont galilaeus. Likely grazing of zooplankton on isotopically heavy Perdiniopsis spp. in spring and on a yet undetected light component in winter were implicated. The data demonstrate that the $\\delta ^13 C$ bulk particulate organic matter samples provides only a simplified view of a complex picture of $\\delta ^13C$ dynamics within the pelagic food web of a freshwater system.