Salinization-Desalinization (SDS) Processes—A Linkage between Hula Valley and Lake Kinneret Ecosystem Management

The salinization process resulted in agricultural damage in the Hula Valley and water quality deterioration in Lake Kinneret. Therefore, salinization-desalinization (SDS) processes have been emphasized in the last two decades. Global and regional extreme climatological events and water scarcity strengthen the link between Hula Valley and Lake Kinneret management design. A bond between optimizing Hula agricultural maintenance and Kinneret water quality protection is conclusively suggested. Saline contribution originated from the southern Hula Valley region to the underground and surface water is higher than from the northern organic soil. The impact of eastern water Intrusion from the Golan Heights as surface waters, river discharge and underground seepage into the Hula Valley represent north-south gradient enhancement. Salinized surface water contribution from the Hula Valley to Lake Kinneret is unwanted because presently Kinneret desalinization management policy is critically required. The present salinization of surface and underground water in the Hula Valley indicates the upper limit suitable for agricultural crop optimization and the decline of salinity is crucial. Enhancement of the portion of Jordan water within the total balance in the valley is beneficial for Hula agricultural crops but serves as a disadvantage to Kinneret desalinization implementation. Therefore, the enhancement of lake water exchange is recommended.

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.

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.

The Ecology of <i>Keratella cochlearis</i>in Lake Kinneret (Israel)

A long term record of rotifers in Lake Kinneret (Israel) indicated that Keratella cochlearis is the most common zooplankter in it. Population dynamics parameters (“egg/female ratio” procedure) were combined with limnological data to analyze temporal fluctuations of K. cochlearis in the Kinneret ecosystem. Lake Kinneret is characterized by mesooligotrophic conditions. During the winter-spring period, when the lake is completely mixed and at low temperatures, water and nutrient inputs are maximal. The lake is stratified in the summer, with an oligotrophic epilimnion;at high temperatures, nutrient and water inputs are minimal. Since the early 1990’s, a decline in rainfall and water inputs and a reduction in Peridinium, coinciding with an ascending level of blue greens, were documented. K. cochlearis is affected by the water input regime, temperature, nutrient concentrations and the phytoplankton composition. The densities of individuals and egg bearing females are low in the summer and fall, and high during the late winter-spring, with E/F values being the highest during January-April. Population dynamics parameters were respectively similar. Regressions of densities of individuals and egg bearing females vs time (years) revealed a prominent long term decline.

Tilapia Stock Suppression by the Great Cormorant (<i>Phalacrocorax carbo</i>) in Lake Kinneret, Israel

The Great Cormorant (Phalcrocorax carbo sinensis) is a well-known fish predator and migratory bird. The bird is a wintering visitor in Israel from the end of October through March. During 1950-1990, the Cormorant used to stay mostly in northern Israel, in the Hula Valley, preying on fish in Lake Kinneret as well as fishponds and adjacent reservoirs. Flocks of Cormorants were deported from northern Israel to eastern and central country regions, causing severe damage to aquaculture. A second operative deportation was carried out and the birds migrated to Lake Kinneret. A survey of their feeding habits was done by The National Nature and Parks Conservation Authority. The outcome information was compiled with international data and assembled towards a conclusive summary of potential causative damage to Lake Kinneret Fishery and Ecosystem structure. Consequences are described and recommendations made.

湖水含盐量和Cu^(2+)浓度变化对Kinneret湖浮游植物的影响

通过人为改变湖水中的Cu2 + 浓度和含盐量的方法 ,Cu2 + 浓度和含盐量变化对Kinneret湖水中浮游植物可能造成的影响进行了分析。结果表明 ,湖水Cu2 + 浓度增加会抑制Kinneret湖水中藻类等浮游植物的生长 ,这对改善湖水水质来说是非常有利的 ,但高的Cu2 + 浓度对农作物生长和人类健康是有害的。在另一方面 ,对含盐量较低的约旦河水来说 ,适当增加Cu2 + 浓度则有利于藻类的生长。Kinneret湖中浮游植物的年平均生物量随湖水含盐量的下降而有增加的趋势 ,特别是当含盐量低于 2 0 0 μg/L左右时 ,浮游植物中蓝藻占的比例会升高 ,这对作为饮用水资原的Kinneret湖水来说是不利的。由此可见 ,适当控制和维持Kinneret湖水Cu2 + 浓度和含盐量对湖水水质保护具有重要的意义。

人为因素导致的盐度变化对Kinneret湖水细菌种群的影响

由于Ｋｉｎｎｅｒｅｔ湖周围的诸多盐泉被人为地导入其下游的约旦河，使得Ｋｉｎｎｅｒｅｔ湖水的盐度逐渐下降，这对作为主要工农业用水和饮用水资源的Ｋｉｎｎｅｒｅｔ湖来说是非常有价值的。然而，对湖水中的细菌来说则可能产生不同的影响。作者通过实验研究发现，湖水盐度的变化导致细菌种群的改变，从而使我们观察到盐度与细菌之间的关系。这些结果表明：盐度变化对湖水水质保护对策和将来一段时间内湖水管理政策的制定都具有重要的意义。

多甲藻对不同光照强度的反应:色素沉着及暗光适应的可能性(英文)

在ＨＰＬＣ色素分析的基础上，研究了多甲藻对不同光照强度（１６．６—２５０μ·Ｅｍ－２ｓ－１） 的反应。类胡萝卡素中最重要的多甲藻素和硅甲藻黄素占叶黄素总量的９０％。随光照强度的 逐步增加，多甲藻细胞中叶绿素ａ含量呈现明显的下降趋势。结果表明硅甲藻黄素和β胡萝卜 素具有光保护作用：１）当多甲藻暴露于较强光下时，硅甲藻黄素／叶绿素ａ之比呈现出明显增 加的趋势。β胡萝卜素／叶绿素ａ之比也显现出明显的增加趋势。２）β胡萝卜素／叶绿素ａ之比 在有光条件下比在完全黑暗条件下要高；３）硅甲藻黄素／叶绿素ａ之比在高辐照度、低辐照 度，及由高到低、由低到高辐照度处理时，显示出组间差异。由此可推出色素代谢可能的途径 及其湖沼学意义。