סמינר מחלקתי: השלכות שינויי אקלים על מבנה ותפקוד אגמים – הכנרת כמקרה מבחן

הסמינר השבועי של החוג ללימודי הסביבה 

יום שני, 20 במאי 2019, שעה 15:00-16:00

בניין הקפסולה, אודיטוריום (קומה 1-)

סמינר מחלקתי: השלכות שינויי אקלים על מבנה ותפקוד אגמים – הכנרת כמקרה מבחן

פרופ' אביטל גזית

בית הספר לסביבה ולמדעי כדור הארץ והפקולטה למדעי החיים, אוניברסיטת תל אביב

Impact of climate change on lakes' level and its cascading influence on ecosystem structure and function

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Avital Gasith

Porter School of the Environment and Earth Sciences, Faculty of Life Sciences
 

Seasonal imbalance between the yearly water input (inflow, direct precipitation) and output (outflow, evaporation) causes seasonal fluctuation of water level in lacustrine systems. The intensity of lake level fluctuation (LLF) is augmented by water abstraction for human use. Littoral zones are the lake areas that are directly affected by LLF. The bottom of littoral zones often vary with depth and location; changing from rocky formation (pebbles, cobbles, boulders) to fine particles (sand, clay). Changes of the littoral zone position with the rise and fall of the water, is followed by structural and biotic changes (species abundance, composition and interactions). Hydrologic impact of CC in lakes in semi-arid, mediterranean-climate regions can illustrate what might be expected elsewhere if CC continues. Impact of CC is manifested by consecutive drought years interrupted by wet years with intensification of extreme rainstorm events and augmentation of LLF.

For the past 40 years, Lake Kinneret, Israel (~170 km2) portrays a distinct hydrologic signal apparently an impact of CC. The role of CC vs the impact of water abstraction for human use as the key factor in the lowering of the lake level following drought years, is presently contested. At any rate, lowering of the lake level negatively influences fish reproduction by reducing rocky littoral habitats and increasing sandy ones, where shore vegetation rapidly develops (in the exposed shores). Rise of the lake level positively affect fish reproduction by increasing the availability of rocky habitats used by fish breeding in rocky habitats (e.g. the endemic cyprinid Acanthobrama teraesanctae) and by providing a new habitat of inundated vegetation. The latter is a favored as a breeding site by cichlid fishes (Amnunim). By modifying the annual and inter-annual intensity of LLF CC can significantly influence fish population size and have a cascading impact on the lakes’ food-web interactions.