The polluting effects of the fish farms in the Gulf of Eilat persist a decade later
This article was written for NoCamels by ZAVIT – Science and Environment in Israel
Known for its rich ecosystem and resilient network of coral reefs, the Gulf of Eilat has been at the center of many scientists, government employees and public activists as it faces a variety of man-made threats – like many sites. ecological values ââof global value. .
In recent weeks, several environmental organizations led by the Society for the Protection of Nature have pressured the Israeli government to immediately suspend an oil transport deal between Israel-controlled Europe-Asia Pipeline Co. and the Israeli government. Med-Red Land Bridge, based in the United Arab Emirates. Ltd. In its current form, the agreement involves the transport of crude oil via tankers from the Persian Gulf to the Gulf of Eilat where it will be routed to Ashkelon for easier and cheaper access to European markets across the Mediterranean Sea.
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Not only would such a move put Israel’s unique coral reef system in the Gulf of Eilat and Mediterranean coastal ecosystems in Israel at risk of irreversible damage from an oil leak or spill, it could also put the facilities out of service. desalination, a decision the country cannot afford to make due to its chronic water scarcity. As a result, residents, scientists and environmental organizations have all spoken out against the deal, warning of the dangers.
However, this is not the first time that the region has been threatened. In the first decade of the 21st century, the country’s once-active mariculture fish farms turned the waters of Eilat upside down due to the build-up of organic matter on the seabed from food waste and fish droppings. Known as eutrophication, this process effectively altered water quality and prevented sunlight from reaching benthic photosynthetic organisms like Zooxanthellae algae in coral tissue, causing them to gradually deteriorate. And because the Gulf’s current flow and water renewal rate are lower than ocean currents, local pollution may have had a more lasting and stronger impact.
“The consensus in today’s research is that it is better for marine pollution to disperse and dilute on the high seas than for acute local pollution to develop,” says Dr Shai Oron, postdoctoral researcher at Department of Geophysical Sciences of the University of Haifa and the Interuniversity Institute of Eilat.
After more than a decades-long struggle, environmental organizations and expert scientists finally succeeded in eliminating fish farms in 2008. But a new Israeli study found that a number of pollutants, including copper, phosphorus and zinc, are still present in much higher amounts. than expected in the area where the cages were located ten years after their removal.
A decade later, pollutants from fish farms are still there
The new study was conducted by researchers at the University of Haifa, the Israel Oceanographic and Limnological Research (IOLR) Institute in Haifa and the University of Western Australia with help from the Israel National Monitoring Program in the Gulf of Eilat. The research method was based on collecting skeletons of foraminifers, microscopic marine organisms known to assimilate chemical elements from available seawater into their skeletons, which essentially “record” environmental conditions over time, allowing researchers to sample the environment and the bioavailable pollutants through them.
âThis is the first time this method has been used to tell us about the chemical state of fish cages,â says Dr. Oron, who led the study.
Collected between 2009-2014 and 2018, the results were sampled at the site where the fish farms were located and were compared to those collected at an ecologically and environmentally similar monitoring site about three kilometers from the former location of the cages.
âImmediately after the cages were removed, we started checking the status of the foraminifera population, but it was not until about a year after the cages were removed that we were able to find live foraminifers at the site. During the first year, damage to all the biodiversity under the cages could be identified, âexplains Dr Oron. In fact, according to the study, benthic ecosystems were so severely damaged by the organic enrichment of the fish cages that no living foraminifera were observed within 80 meters of the cages for several months after their removal.
According to Oron, the original purpose of the study was not to detect contaminants at all. “We tried to examine the skeletons of foraminifers collected from the site over different years to detect rainwater flowing from the shore to the sea, but suddenly we saw the pollutants in amounts not typical of the region. . “
The results of the study indicate that the concentrations of various harmful substances were higher in the areas where the fish farms were located compared to the control site. While zinc (Zn) returned to normal levels just three years after its removal, copper (Cu) levels were found to be four times higher at the cage site compared to the control site, even in 2018 – a whole decade after the fish were withdrawn. firm. Although phosphorus (P) levels at the cage site were found to have declined significantly after 2011, the researchers found that the levels had actually increased over the years since then due to the gradual release of bottom sediment. that accumulated while the fish cages were still active.
But where do these substances come from? According to Dr. Oron and his research team, there are two likely sources; the first being manufactured fish feed, which typically contains a variety of elements including P, Zn and Cu. The second source is the anti-fouling paints and dyes that have been used in the infrastructure of fish cages and the nets themselves to prevent algae from clinging to submerged surfaces. These substances were probably released in soluble or particulate form, flaking or blowing off over time.
Fortunately, researchers estimate that the contamination spread to a distance of about 200 meters from the original locations of the fish cages, but that the pollutant concentrations did not cover the entire seabed of the coast. north of Eilat Bay, suggesting that the effects are local.
Too much phosphorus is toxic
A number of other studies have found direct links between the high concentrations of substances identified by new Israeli research and damage to living organisms in the marine environment. Metals such as Cu and Zn occur naturally in the marine environment in minimal amounts, and they play an important role in the proper functioning of biological systems. However, when their concentrations increase several times more than natural values ââand are exposed to plants and wildlife, it can interfere with their development, physiology and potentially lead to increased mortality.
Copper, for example, is one of the most toxic elements for marine organisms, and higher levels can cause irreversible damage to various species such as fish and invertebrates, which are 10 to 100 times more sensitive than the mammals. Additionally, another recent study conducted in the Gulf of Eilat found that excess copper in seawater can impair the resistance of corals to heat stress events, which inevitably leads to fatal bleaching. This is of particular concern as the coral networks in the Gulf of Eilat are known to be the most resilient reef system to climate change compared to other reef systems like the Great Barrier Reef.
At high concentrations, phosphorus is no different because it is the main driver of eutrophication.
âPhosphorus is a nutrient found in small amounts in a marine environment where coral reefs thrive, such as that of the Gulf of Eilat,â says Dr. Oron. “High levels of phosphorus disrupt the ecological balance of these systems and allow the algae that feed on them to flourish, causing sunlight to block and damaging coral reefs and other living things in the environment. “
Consider the consequences fish farms
The results provided by the skeletons of Foraminifera were not the only evidence of contaminants in the water found in the study. According to measurements of the pollutants in the sediments themselves from samples taken two years and five years after the removal of the cages, the copper concentrations within forty meters of the old cage were at levels considered harmful according to US Oceanic and Atmospheric Administration (NOAA) criteria but acceptable to the Israeli Ministry of Environmental Protection.
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Likewise, the phosphorus concentration in the previous cage locations was nearly eight times higher than standard levels.
âThe data can give us an idea of ââwhat would have happened if the cages had not been removed. There are currently people who wish to bring back commercial fish farming systems to the Eilat Bay area, but they must take into account that such movements have important long-term consequences, âconcludes Dr Oron.