The effect of thermal pollution on benthic foraminiferal assemblages in the Mediterranean shoreface adjacent to Hadera power plant (Israel) Ruthie Nina Arieli a , Ahuva Almogi-Labin b,⇑ , Sigal Abramovich a , Barak Herut c a Department of Geological and Environmental Sciences, Ben Gurion University, Israel b Geological Survey of Israel, Israel c Israel Oceanographic and Limnological Research, Israel article info Keywords: Thermal pollution SST Living benthic foraminifera Species richness East Mediterranean abstract The thermal pollution patch of Hadera power plant was used as a natural laboratory to evaluate the potential long-term effects of rise in Eastern Mediterranean SST on living benthic foraminifera. Their sen- sitivity to environmental changes makes foraminifera ideal for this study. Ten monthly sampling cam- paigns were performed in four stations located along a temperature gradient up to 10 °C from the discharge site of heated seawater to a control station. The SST along this transect varied between 25/ 18 °C in winter and 36/31 °C in summer. A significant negative correlation was found between SST in all stations and benthic foraminiferal abundance, species richness and diversity. The total foraminiferal abundance and species richness was particularly low at the thermally polluted stations especially during summer when SST exceeded 30 °C, but also throughout the entire year. This indicates that thermal pol- lution has a detrimental effect on benthic foraminifera, irrelevant to the natural seasonal changes in SST. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Over the past several decades public and scientific awareness to global warming has increased significantly. As of today, it is widely accepted that the upper 300 m of the world’s oceans are showing a clear multi-decadal warming signal attributed to increased global temperatures (e.g. Lyman et al., 2010; Trenberth, 2010). A cur- rently accepted forecast for the next two decades is that ocean temperatures will rise at a rate of 0.2 °C per decade (IPCC Report, 2007). As a result, many studies have examined the potential del- eterious effect of global warming on the natural environments in general and on marine environments in particular. Over the past 44 years an increase of 1.28 °C has been recorded in the Mediterra- nean Sea, most of which occurred since the eighties (Stips et al., 2006). The current rate of warming in the Mediterranean Sea, based on satellite data from 1990 to 2006, is 0.067 °C per year (Del Rio Vera et al., 2006). This rate is slightly more than double the current forecast for global warming which stands at 0.028 °C/ year (Stips et al., 2006). Temperature is a major factor in the metabolism of living organ- isms. It controls chemical reactions which affect the synthesis of enzymes which in turn determine the general state of the organ- ism, including growth rates and reproductive success. Temperature also determines the geographical distribution of most organisms. The rise in the Mediterranean Sea water temperature due to global warming may give a distinct advantage to tropical invasive species originating from the Indo-Pacific, the Red Sea, and the Atlantic, over the native fauna (Galil and Zenetos, 2002; Sabatés and Lloret, 2006; Bianchi, 2007). In fact, since the opening of the Suez Canal in 1869, a large scale one-way migration began from the Red Sea to the Mediterranean (Por, 1978, 2009, 2010). Several species of ben- thic foraminifera also took part in this ‘‘Lessepsian Migration’’ as shown in several recent publications (Langer and Hottinger, 2000; Hyams et al., 2002; Hyams-Kaphzan et al., 2008; Langer, 2008). Foraminifera are thought to be the most diverse group of micro- scopic organisms with a calcareous shell alive today (Sen Gupta, 1999) and they are also prime candidates for studying the effect of anthropogenic pollution on the marine biota. As unicellular organisms with a short reproductive cycle and fast growing rates, they show a quick response to changes in environmental condi- tions and serve as extremely sensitive indicators of changes in nutrient abundance, salinity, irradiation, oxygen concentration, anthropogenic contaminations as well as temperature fluctuations (e.g. Alve, 1995; Jorissen et al., 1995; Alvarez Zarikian et al., 2000; Saraswat et al., 2004). Most benthic foraminiferal species, espe- cially the larger ones, have minimum thresholds for reproduction (Murray, 2006; Langer and Hottinger, 2000). Bradshaw (1961) showed in laboratory experiments that the upper growth temper- ature limit for the investigated species of benthic foraminifera is 35 °C and the maximum lethal temperature is 45 °C. The main factors that determine the abundance of benthic foraminifera in 0025-326X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2011.02.036 ⇑ Corresponding author. Tel.: +972 2 5314232; fax: +972 2 5380688. E-mail address: almogi@gsi.gov.il (A. Almogi-Labin). Marine Pollution Bulletin 62 (2011) 1002–1012 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul