Predictability of Ecological Changes in Lake Kinneret

Several ecological key factors were indicated in the Lake Kinneret ecosystem during 1969-2000: Elevation of the biomass of non-pyrrhophyte-phytoplankton, chlorophyta, cyanobacteria, and diatoms; decline of Peridinium maximal from 215 - 240 to 175 - 200 ranges (g/m 2 ); decline of zooplankton (herbivore and predator) relative to phytoplankton biomass (g/m 2 ); lower loads of Nitrogen and slightly also phosphorus in the river Jordan discharge; decline of precipitations and lake water level; significant decline of epilimnetic nitrogen and minor changes of phosphorus concentrations initiated decline of N/P mass ratio to the establishment of a significant change of the ecosystem to be modified from P to N limitation. What could be other than essential outcome of future prediction that results of 20 years (1969-2000) of routine and comprehensive monitor carried out in Lake Kinneret initiated? The Lake Kinneret ecosystem dynamics after 2000 justified retroactive post-factum earlier conclusion of appropriate predictability.


Introduction
During the last 80 years the Lake Kinneret and its drainage basin have undergone significant changes. Some of those changes are natural and others are anthropogenic. The present ecosystem structure is not similar to that one that was investigated and practically operated during 20 years earlier. Ecological modifications did not come abruptly but gradually instead. It is the natural characterization of ecological systems to be changed gradually and therefore their recognition is not commonly strictly defined. The rational of this paper is making a renovated insight into an earlier  recognized trait of Lake Kin-neret ecosystem structure as background for the consideration of the up-to-date (>2000's) alterations. Gradual ecosystem changes do not always appear abruptly and therefore the recognition of a change as a long-term modification requires longer duration. A critical question is therefore: would it be possible to recognize earlier ecosystem significant alteration as a start of a long-term case. The usage of old  data through re-evaluation access was considered here to justify an outcome of predicted conclusion about on-going trends of ecological changes.
As of 2010, when desalinization program was implemented (650 10 6 m 3 /y; mcm/y), Lake Kinneret, was the national major source for domestic water supply. The Kinneret ecosystem has undergone man-made and natural modifi- decline of nitrogen loads in the Jordan River; decline of the epilimnetic N/P mass ratio, followed by enhancement of cyanobacteria. The Kinneret ecosystem shifted from P to N limitation. The decline of water level is due to both natural droughts and surplus pumping. Decline in nitrogen in the Kinneret epilimnion was probably due to both the reduction of river discharges (droughts) and a lower N contribution from the drainage basin, as a result of anthropogenic activities. The Hula old Lake and swamps in the vicinity were drained and land was converted to agricultural development; most of the sewage (human and fishpond effluents) was eliminated from the lake; conclusively, the change in the Kinneret ecosystem structure by shifting from P to N limitation was affected by both the anthropogenic and natural processes. Those changes implemented from 1933 and onwards [1].

Material and Methods
The chemical data of nutrient concentrations in the Jordan River, the computed Jordan River loads, and Discharges, as well, as the Epilimnetic nutrient concen-

Results
Jordan Discharge and Lake Epilimnion  In order to indicate temporal changes of nutrient concentrations (ppm) the period of 1970-2000 was divided into two periodical groups (Table 1): 1970-1984 and 1985-2000. The two periods were comparatively (ANOVA Test) (p < 0.05) analyzed against each other. In Table 2

Rain Gauge
In Table 3, the annual rain gauges of 1940-2018 were grouped in 4 periods. Table 3 indicate precipitation decline since 1970. The obvious outcome of the precipitation decline is the annual Jordan River discharge (10 6 m 3 /y; mcm/y) also decreased (see above) and consequently the Lake Kinneret Water Level (WL) as presented in Table 4. Table 4  The change of Lake Kinneret ecosystem structure during 1969-2000 is presented in the following three tables: Table 5-Zooplankton; Table 6-Phytoplankton; and  Table 7-Chemistry.  Tables 5-7 represent the temporal changes of zooplankton (Copepoda, Cladocera, Rotifera) wet biomass (g/m 2 ) ( Table 5) and Numerical densities (No./L) ( Table 7) and Phytoplankton (Chlorophyta, Cyanobacteria, Diatoms, Peridinium.

Results in
Non-Pyrrhophytes (g/m 2 ), Chlorophyll (mg/m 2 ), Primary Production (gC/m 2 /day) in Lake Kinneret comparatively (ANOVA; p < 0.05) in two periods: 1970-1984 and 1985-2000. Results in Table 5 indicate sharp decline of the biomass of Copepoda, herbivores and predators later than 1984 whilst the decline of Cladocera was moderate and no significant change of the Rotifer's biomass.
Results in Table 6 indicate significant increase of the biomass of Cyanophyta, Diatoms and Chlorophyta. The periodical averages of the biomass of Peridinium was not significantly changed between the two periods whilst Maximal measures were varied between 215 -240 and 175 -200 g(ww)/m 2 during the earlier and later periods respectively. Taking into account that algal Primary Production is dominantly affecting DO concentration (upper 10 meters), the influence of increased biomass of Non-Pyrrhophyta is pronounced.
The Epilimnetic loads (tons/Epilimnion) were comparatively tested (ANOVA; p < 0.05) in two periods: 1969-1984 and 1985-2000 (Table 8).     Table 8             in the Kinneret Epilimnion as related to enhancement of water inflow and inversely with TN concentration, is presented in Figure 2, i.e. the higher is the water input the higher is the Epilimnetic TN concentration and the lower is the TP concentration. Moreover, the higher is the inflow the higher is the TN/TP mass ratio. Figure 3 represents the decline of Epilimnetic loads of PTD and SRP dur-

Discussion
The management and design of Lake Kinneret, deserves a wide range of acceptance willing and agreement, between the public's ambition and formal authorized managers, legislators, and scientists within a formulated scope of a "golden pass" aimed at bridging between public demands and ecological rules. If scientific information is insufficient, a worldwide replacement principle known as Open Journal of Ecology cyanobacterial dominance unfortunately was not predicted. On the contrary, the scientific response was even a negative objection. Cyanobacterial burst was denied accompanied by false alarm blame but in summer 1994 the N 2 fixers bloomed [5]- [15]. Zofia et al. [16] concluded that the best explanation for variations among lakes in the rate of cyanobacteria enhancement was due to nutrient (P, N) concentrations [14] [15] [16] [17] [18]. The Kinneret case represents how evaluated prediction of scientific data might prevent the replacement of "Carefulness Prevention" principle by submission of solid scientific conclusion for managers implementation [19].
The construction of the National Water Carrier (NWC) (1950's) gave Lake Kinneret the status of the major national resource for domestic supply. Recently document was composed and submitted [19]. The document initiated a public "noise" due to predicted an abrupt development of Eutrophication in Lake Kinneret with enhanced conditions of anoxia within 3 -4 years. A thorough evaluation of the available data record classified these predictions as wrong and the publicized outcry deceased. This is an example of a case where unpredictable conclusion was wrongly predicted as a result of lack of information.
Accelerated rates of qualitative and quantitative degradation of fresh waters are a global case. Nevertheless the level of success of potential cope capability of pollution reduction is highly dependent on data quality and temporal cover [20] [21] [22] [23] which require appropriate economic and social background. Reasonable certainty of prediction depends much on functional properties of lakes in general and especially Kinneret, the only natural body of freshwater in Israel.
Considering Kinneret water quality degradation the most common contaminants are organic and inorganic pollutants. Commonly, if loading of pollutants has been reduced appreciably renewal rate relies upon dilution effect of the contaminants. Nevertheless significant trait is due not only to quantity aspect but also to the compositional level. Reduction of Nitrogen without relatively P decline might be a case of quality degradation, as in the Kinneret case. The anth- The prominent modification within the ecosystem structure was Phytoplankton species composition as affected by nutrient availabilities. Therefore, renewal of water quality is mostly due to nutrients supply and to a lesser extent to hydrological properties such as residence time and salts budget (salinity). Diversion of major external nutrient loadings was found to be adequate to restore the Eutrophic Lake Washington in Seattle [23] [24]. The optimal implementation aimed at reduction of nutrient availability is known [22] as Nutrient removal by ranges (g/m 2 ); decline of Zooplankton (herbivore and predator) relative to phytoplankton biomass (g/m 2 ); lower loads of Nitrogen and slightly also Phosphorus in the river Jordan discharge; decline of regional precipitations and consequently lake water level; significant decline of Epilimnetic Nitrogen and minor changes of Phosphorus concentrations initiated decline of N/P mass ratio suitable for the establishment of a significant change of the ecosystem to be modified from P to N limitation and outbreaks of Cyanobacteria. Retroactive post-factum data evaluation (this paper) of the Lake Kinneret ecosystem dynamics justified earlier predictive conclusion.
Istvanovics [25] discussed the importance of P cycle and the role of limitation in shallow lake. Nitrogen plentiful conditions during 1970-1990 in lake Kinneret created limitation status of P. Nevertheless decline of Nitrogen resources accompanied by slight elevation of Phosphorus resources during late 1980's and the 1990's formed the decline of Peridinium and the enhancement of Cyanobacteria. Nitrogen limitation is vital to a lesser extent to Cyanobacteri as a result of their capability of Nitrogen fixation. For Peridinium Nitrogen is a significant demand i.e. limiting factor. The term "Nutrient Limitation" in nature include more than one consumer and several game players (organisms) [25]. The present paper is focused at the Kinneret ecosystem which includes the following "game players": N and P nutrients, and three algal groups: Pridinium, Non-Pyrrhophyes (Chlorophyta, Diatoms), and Cyanobacteria. The Nitrogen sources for the Peridinium, Chlorophytes and Diatoms are external (drainage basin) and for the Cyanobacteria-also Nitrogen fixation. The Phosphorus origin for the Peridinium growth and reproduction is in the bottom sediments and is therefore not limited. This P is transferred into the Epilimnion through Peridinium Cysts mediation and later, from the Peridinium vegetative bloom crash, together with deposited dust storm as bio-available substrate for Non-Phrrhophyte algal growth and reproduction. As soon as the external Nitrogen supply was sufficient (1969-mid 1980's and occasionally later as a result of heavy floods) Peridinium was dominant and the limiting nutrient was Phosphorus. From late 1980's and onwards external supply on Nitrogen declined and a sequence of changes started: Cyanobacteria enhancement, Peridinium decline and nanno-phytoplankton (Chlorophyta, Diatoms) enrichment: The Nitrogen became the nutritional limiting factor. The essence of this paper is: Does those ecosystem changes were possible to be predicted 20 year earlier, at the beginning of the 2000's? Conclusively the answer is YES! So what? What could be beneficial for Lake Kinneret if kind of approach would come earlier by 20 years. Ivanovitcs [25] demonstrate the case of Lake Balaton where surplus of external P loads during 10 years created Eutrophication in the lake, followed by 10 years of external P loads reduction which initiated 10 years of recovered Lake Balaton. The limnological literature includes numerous of cases of ecological deterioration, pollution or even Eutrophication case evaluations. Those evaluated cases were resulted by various conditions such as nutrient/pollutant surplus inputs, overfishing, invasion or introduction of exotic species, industrialization, de-forestation, air pollution anthropogenic intervention or inappropriate hydrological lake managements and others. But preconditioned prediction cases are rare. Appropriate evaluation of the Lake Kinneret ecosystem 20 years ago could probably prevent later complete or partial water quality deterioration.

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.