The combined and individual effects of elevated salinity and temperature on foraminiferal growth.

The desalination process includes the discharge of brine into the sea and locally increases the salinity, which may affect the ecosystem. In many cases, desalination plants are associated with power plants that cause additional anomalies in temperature. In this study, we used benthic foraminifera, known to be sensitive marine proxies as a model system to evaluate the impact of desalination (both with and without the association of power plants) on the local ecosystems. We examine three desalination plants along the Israeli coast. In each, we compared the foraminiferal populations near the discharge (outfall station) and in a control station. The results highlight that the most robust responses were observed when the brine was discharged along with warm water from the nearby power plants. Additionally, changes in the abundance of specific species indicate their sensitivity to the brine. For example, agglutinants with organic cement were present in high numbers at the control stations, while at the outfall they were almost entirely absent. Next, we examined the thermal and salinity tolerance of two types of local symbiont bearing foraminifera that are characterized by different shell type and algal symbionts: Penropolis spp. and Amphistegina lobifera. We evaluated the response of these species by measuring the foraminiferal growth. Specimens of these species were exposed to 4 salinities (39, 42, 45 and 49). These treatments represent the values of the control and outfall stations and addition to extreme salinity. Each salinity treatment performed at two temperatures 25ºC-35ºC. Preliminary results show that both species exhibit resilient to extreme salinities with reduced growth only at the highest salinity. No lethal response was observed in this extreme salinity. These observations demonstrate that symbiont bearing foraminifera are pre-adapted to conditions of extreme salinity.