University of Haifa: 2021 Mediterranean Oil Spill Harmed Far More Marine Species Than Was Apparent from the Coastline
The model developed by the researchers estimated that, in the area where pollution concentrations were highest, up to 75.4 percent of species living in the upper water layers may have been exposed to levels of toxic substances associated with harmful and even lethal effects. A new study conducted at the University of Haifa following the Mediterranean oil spill found that in the area where pollution concentrations were highest, up to 75.4 percent of the principal species living in the upper water layers were exposed to concentrations of toxic petroleum-derived substances associated with harmful and even lethal effects. The study examined the “Tar in the Storm” event, which affected Israel’s Mediterranean coastline in February 2021, and for the first time combined a model estimating the sensitivity of marine species to the toxic substances in oil with a model reconstructing how the oil slick spread through the sea during the event. “When a pollution event is assessed solely on the basis of animals found dead or covered in tar, a large part of the potential damage to the marine ecosystem may be overlooked. Small species and early life stages can be harmed below the water’s surface without leaving any immediate or visible evidence,” said Dr. Igal Berenshtein of the Leon H. Charney School of Marine Science at the University of Haifa, one of the study’s authors.
During February 2021, Israel’s entire Mediterranean coastline, stretching approximately 190 kilometers, was contaminated by oil and tar originating from a spill that occurred outside Israel’s territorial waters. Although the event is considered one of the most severe marine pollution incidents ever to occur in the region, until now there has been no comprehensive assessment of the risk posed to the different species in the marine ecosystem. In the present study, doctoral student Omri Lapidot and Dr Berenshtein, head of the Marine Ecology and Environmental Health Laboratory in the Department of Marine Biology at the University of Haifa, together with a team of researchers from the Leon H. Charney School of Marine Sciences at the University of Haifa, the Israel Oceanographic and Limnological Research, the Israel Meteorological Service, the University of Miami, and Tel Aviv University, set out to examine how the risk posed to different marine species during an oil pollution event can be assessed, even when there is no direct information on the sensitivity of every species to the toxic substances in oil.
To this end, the researchers developed a new model that estimates the sensitivity of marine species to polycyclic aromatic hydrocarbons (PAHs), a group of toxic compounds found in crude oil, even when no direct toxicity data are available for those species. The model bases its estimates on data from biologically related species, while taking into account each species’ life stage and its position in the food chain. To construct their model, the researchers compiled toxicity data collected from the scientific literature and from a database created following the Deepwater Horizon oil spill disaster in the Gulf of Mexico. After evaluating the model’s performance, they combined it with a simulation that reconstructed the movement of the oil over an 18-day period based on data on ocean currents, winds, temperature, and salinity.
The study’s findings show that the model developed by the researchers was able to estimate the concentrations at which approximately 88 percent of the species included in the analysis would be affected by the toxic substances. In the area where pollution concentrations were highest, approximately 75 percent of all the species examined (46 species) were exposed to pollution levels associated with harmful and even lethal effects. At the highest concentration examined, the model revealed potential for harm to 28 of the 31 fish species, 10 of the 11 species of planktonic crustaceans, and all five gastropod species included in the analysis. The study also found that as the distance from the main pollution zone increased and the concentrations of toxic substances declined, the proportion of affected species decreased accordingly. The researchers emphasize that this is a model-based risk assessment rather than a direct measurement of mortality. “The advantage of the model lies in its ability to identify in advance where the most severe ecological damage is expected to occur and which species are at risk. It makes it possible to move from a general assessment of the spread of an oil slick to a targeted assessment of the risks facing the species living in each area. Such information can help authorities quickly decide where to carry out sampling, where to deploy monitoring teams, and how to prioritize response actions during future pollution events,” said doctoral student Omri Lapidot.
Published in the journal Marine Pollution Bulletin
