NAF-IOLR

In Lake Kinneret, the dinoflagellate (a single cell alga with two flagellates) Peridinium gatunense forms spring blooms of intensities comparable to those of red tides. A typical Peridinium bloom is characterized by distinct spatial heterogeneity (or patchiness) of the Peridinium population, as well as daily vertical migration of the population from near the surface during the day time to deeper water during the night. Horizontally, Peridinium population is typically distributed in patches scaling hundreds of meters to several kilometers, and is visible from shore as coffee-brown regions within the bluer surrounding water. Using remote sensing devices on board a satellite, the bloom of Peridinium in Lake Kinneret is visible and quantifiable. The Satellite-based Information System on Coastal Areas and Lakes (SISCAL), initiated and operated by Dr. Gideon Tibor (NIO-IOLR), was used to process the satellite images and distribution data obtained by the satellite. This data was then used to determine the relative distribution of chlorophyll in Lake Kinneret which is attributed to the developed population of Peridinium.

For many years, the spring blooms of Peridinium were considered an indicator of the stability of the lake ecosystem and the lake’s water quality. Dinoflagellates are important components of the marine food web. However, when these blooms occur in high numbers resulting in a red-tide-like phenomenon, they can have a detrimental effect on marine life and also introduce toxins into the animals that are meant for human consumption. In the past decade the seasonal blooms were substantially reduced: 2000, 2001, 2005, 2006 and 2008 were characterized by a substantially reduced spring population of Peridinium while in the years 2003, 2004 and 2007 a normal and in some cases very high density bloom occurred. KLL scientists pay great attention to these bloom events, the reasons for their discontinuity, and their biological characteristics.

The Peridinium bloom event of spring 2007 was studied by the KLL scientists during a comprehensive effort coordinated by IOLR scientist Dr. Assaf Sukenik. The team studied the spatial distribution and dynamic variations of Peridinium population in the northern area of Lake Kinneret for three consecutive days (day and night) during the last week of March 2007. The main goal of the study was to characterize the patchy nature of Peridinium blooms in the lake and to identify and quantify the physical and/or biological processes that control this patchy nature.

The large database collected during that extended expedition suggests quantitative relationships between the size of the Peridinium population and the amount of Jordan River water diluted in the lake due to flood events. Satellite images and earlier studies indicated that the Peridinium patches occur mainly in the northern part of the lake where Jordan River enters the lake. Therefore, this area was proposed as the site of population development and growth. Such a growth is supported by nutrients and chemical conditions provided by the river inflow. The distribution of the developed Peridinium population to other locations is facilitated as the population “tracks” the Jordan River plume in Lake Kinneret. Based on the unique database collected during this study, KLL scientists postulate that a bulk of water enriched with Peridinium population is disintegrated from the “hatching” and “nursing” area (Jordan River inlet area) and starts its migration in the lake in accordance with the existing waves, currents and streams.

The patch migration continues along the “Jordan River” trail in Lake Kinneret, from the north area, the site of the population emergence, along the northwest coast and to the lake center, in accordance with the results of a circulation simulation model of Lake Kinneret operated by Dr. Alon Rimer (KLL). Based on this model, KLL scientists speculate that a single Peridinium patch migrating in the lake is of different age or developmental stage then another patch.

This study demonstrated once again the capabilities of the Kinneret Limnological Laboratory to identify crucial aspects of the lake ecosystem and to study them in a cooperative effort to better understand trends and changes in the lake’s ecosystem.