Who painted the beaches of Eilat pink?

In April 2023 and 2024, mass die-offs of planktonic amphipods occurred in the Gulf of Eilat. Researchers have found that this was the effect of seasonal circular currents called eddies.

Anyone who visited Eilat in the past two years, in March and April, was surprised to discover beaches covered in pink. Upon closer inspection, millions of tiny pink creatures with big eyes could be seen on the beaches. New research, conducted in the laboratory of Prof. Tamar Guy-Haim Seas and Lakes of Israel Research and Ben-Gurion University, in collaboration with Dr. Bracha Prestei from the Inter-University Institute for Marine Sciences in Eilat, discovered that these pink creatures are planktonic crustaceans from the amphipod order. Amphipods are characterized by a laterally flattened body and therefore appear to swim on their sides, hence their name. The pink color in some amphipods is due to the presence of carotenoid pigments, which they acquire from their food. To identify the species of amphipod, the researchers used integrative taxonomy that combines morphological identification and genetic testing. To understand the possible reasons for the mass mortality and their washing ashore, year after year and in the same season, the researchers examined the various environmental characteristics.

"Like a detective mystery, we came up with a number of hypotheses," says Prof. Guy-Haim. "Many cetaceans have a unique reproductive strategy called semelparity. Reproduction occurs only once during the life cycle, after which the females die, usually simultaneously." To examine whether this was the cause of mortality, the researchers examined the sex ratio in the dead cetaceans. "We found an almost equal ratio between males and females, and also individuals of different sizes, so we could rule out semelparity."

Climate change, especially the warming of sea water during "heat waves," short periods in which sea temperatures rise abnormally, can cause mass mortality of marine animals. Such mortality of reef fish in Eilat Recorded in the summer of 2017 when the water temperature rose by more than 4 degrees in two and a half days. Guy-Haim and her research partners examined the seawater temperature during and before the mass mortality events of the sea urchins and found no abnormal values. "Sometimes environmental stresses lead to increased exposure to parasites and other pathogens. This has been found in reef fish andLong-spined sea urchin "In Eilat," adds Guy-Haim. "We found no evidence to support this hypothesis either."

To find a solution to the mystery, the scientific literature was meticulously scanned. Indeed, in an old article, the researchers found a report of a similar mortality event of these sea urchins in March 1977, when they covered the shores of the city of Aqaba en masse. This discovery indicates that this phenomenon may be cyclical and linked to seasonal natural processes in the northern Gulf of Eilat. Previous studies in the Gulf have shown that during these months there is activity of eddies, circular currents that can transport water from the depths to the surface (upwelling) or vice versa (downwelling) in a motion similar to the rotation of a screw. In the Northern Hemisphere, cyclonic eddies move counterclockwise and cause water to rise from the depths of the sea. Cyclonic eddies in the northern Gulf of Eilat, which are active mainly between November and April, are characterized by a flow ten times faster than normal surface currents. "We hypothesize that the cetaceans were caught in a cyclonic mixer in the northern part of the bay and washed ashore," explains Prof. Guy-Haim. "In Hawaii, a mass death of cetaceans of the same species was recorded with the appearance of a cyclonic mixer. This is currently the main hypothesis, but the connection between the current regime and such phenomena in the Gulf of Eilat and other seas around the world must be further investigated." Cetaceans and other planktonic organisms play an important role in the marine food web. They are a favorite food for fish, waterfowl, and even whales.  

More of the topic in Hayadan:

• The coral reef in Eilat is in a very sad state
• Artificial reefs protect the coral reefs in Eilat
• The climate crisis and declining precipitation in the Eastern Mediterranean
• Talk about the climate in wartime
• Extreme rain events and their effect on mortality - new conclusions from a global study