Project Synopsis: The Ecological Effects of Desalination Brine

I wonder, how many of you reading this had ever considered drinking seawater? When I was a kid playing at the beach in summer times, my parents always told me not to drink the seawater; It would make me sick. In many parts of the world, ex. Denmark where I grew up, drinking water comes from the ground as groundwater, from rain, lakes, rives, aquifers or other terrestrial sources - not from the salty Ocean.
However, in other parts of the world, groundwater is extremely scarce and rain almost non-existing. How does people get drinking water in these regions? Well, one way is actually to drink the Ocean. Of cause not literally taking a glass down to the beach and pour in some water - but take the seawater and treat it; remove the salt; desalinate it.
The Ocean covers more than 70% of our globe and consists of almost 90% of all accessible water. Using this massive water resource for drinking water seems almost too logical.


Desalination of seawater is a widely used source of potable water in arid and semi-arid regions, like the Arabian Peninsula, Israel, parts of the Mediterranean region and now in drought-stricken California too.

The process of desalination can be described very simplified: Seawater is pumped into a desalination plants where, by various methods, the salt is removed and the water cleaned to make fresh drinking water. Many desalination plants are using reverse-osmosis to remove the salt from the water. In this method, pressure is applied to push the water through a semi-permeable membrane creating two products: fresh water and a high-salinity brine. The brine, along with various chemicals used for treatment and cleaning at the plant, is then discharge back into the ocean, very often in close proximity to shorelines and beaches.

Schematic diagram of the SWRO process

Despite the growing popularity of seawater reverse osmosis (SWRO) plants and the overall global interest in seawater desalination, very little is know about the consequences of discharging brine into coastal communities.

The addition of very saline water in a confined coastal area could cause changes in the biochemistry and biology potentially leading to changes in the trophic levels, coastal pollution or recreational disruption.


I study the effects of such brine in coastal areas. My main focus is the ecological effects on ocean organisms and I hope to be able to identify what happens in the coastal zone when discharging brine, which constituents in the brine is effecting organisms and the boundary limits and thereby help to increase the sustainability of seawater desalination.

During my time in Israel I will conduct two biological experiments, that hopefully will enlighten how different organisms will respond to brine discharge.

Phytoplankton growth

Firstly, I will look at how phytoplankton will respond in their growth, primary production and the structure of the community, eg. what species of phytoplankton is growing.
Phytoplankton make up the very bottom of the food chain, and changes in their growth and community could cause changes up through the higher trophic levels. Certain conditions can also favor certain phytoplankton species causing periodical blooms of plankton that can, depending on the species, be harmful for both fish, marine mammals and anthropogenic activities.
To test the effects of brine on phytoplankton, I will have to grow them under conditions I control and in a confined space I can access.
The method of choice is to add different treatments to bottles of seawater. The seawater will be collected directly from the ocean surface and will contain a random selection of the local phytoplankton community. The bottles containing seawater will then be treated different ways:

The first bottle will serve as control and have nothing added to the seawater. This bottle is the reference point. The second bottle will have added 1% brine, which will represent the lower margin of what can be assumed to be mixed in the coastal water. The third bottle will have 10% brine, which is representing a maximum concentration of brine. And a fourth bottle will contain some of the known chemicals and metals discharged along with the brine.
Over a period of 5 days the bottled and treated seawater will be monitored and by the end it will be possible to map out how the phytoplankton grew in the four different conditions.

Four bottles containing seawater and each a different treatment.

Coral health and growth

Secondly: I will be looking at coral health and growth in brine.
Corals are, to many, pristine ocean creatures and some of the most diverse and lively reefs are located in the Red Sea - many in close proximity to desalination discharge.
Coral reefs are crucial habitats, shelters and feeding grounds for enormous amounts of fish and seacreatues and are recreational havens for scuba divers and snorklers providing and important economic factor for the countries with coastal coral reefs.
The health and well-being of coral reefs are therefore important in many aspects.
In a similar manner as with the plankton, I will grow corals under specific conditions and monitor them. To do this, small fragments of corals has to be collected from the ocean. The fragments are collected from specific coral nurseries, that are artificial reefs in the ocean, where corals are grown with the specific purpose of using them in science experiments. This enables scientists to do research on corals without disturbing actual reefs.

For the corals a control and a 10% brine treatment will be monitored. Because of the much slower growth, this experiment will be running for a minimum of 4 weeks. Each week a coral fragment will be collected and it will be analyzed for its growth and for the growth of the symbiotic algae living within it.

Schematic of an aquarium with coral fragments growing in it

I am excited to get started on these experiments and see what will happen when, under controlled conditions, local species are introduced to a higher salinity.

Stay tuned the next two months for updates and pictures of the bottle incubations and aquariums full of corals!