Improving harmful algal bloom predictions in the Middle East – submesoscale physics disrupt food and water security
Short description
In the Arabian Sea, the monsoons and strong winds impart a lot of energy into the ocean, creating fast and dynamic ocean currents. These currents interact with the complex seabed morphology of steep cliffs and canyons, and sometimes lead to transport of deep water to the shallows. Uniquely, deep waters in the region are very low in oxygen, leading to harmful algal blooms when they are brought near the surface and in-shore.
We use remotely controlled submarine robots to observe the ocean for months at a time, collecting a huge array of measurements to understand the pathways between climate, ocean circulation, biogeochemistry and harmful algal blooms in the Arabian Sea. These robots map currents and ocean properties in high-definition, in 3-D and over time, so that we can understand and therefore better predict how the ocean functions.
Project background
The Middle East and the Arabian Sea are home to rich and diverse marine ecosystems. Countries in the region such as Oman, Iran, Yemen and Pakistan are heavily dependent on their coastline for tourism, aquaculture, fisheries, both small-scale and industrial, and freshwater supply through desalination for consumption and agriculture. The area is also vulnerable to recurring harmful algal blooms, HABs, that plague vast coastlines, clog desalination plants and cause extensive fish deaths, further straining food and water supplies for the entire Middle East.
The main cause of algal blooms is well explained. A large and sudden increase in nutrients, either from pollutants or from deep water, in sunlit surface waters, triggers the growth of phytoplankton in rapid succession. What is more difficult to understand is where, when, how and why these algal blooms turn into harmful algal blooms. This occurs either when algae produce toxic substances (toxins) or when flowering is so intense that it results in large amounts of dead organic material that absorbs oxygen in the water during decomposition.
Methods
Several national and international projects have developed methods for early warning of harmful algal blooms in an attempt to limit its effects. However, these methods have difficulty predicting algal blooms in shallow coastal regions where their impact is also most severe. We believe that this is because the physical ocean processes that control harmful algal blooms occur on much smaller scales in shallow coastal regions (0.1-10 km, hours-days) and are therefore much more difficult to model. Processes that occur on these small scales are particularly difficult to observe and understand. Research vessels can monitor with high resolution, but campaigns are short-lived, they last for a maximum of a few weeks and often miss these short-lived occurrences.
To address this knowledge gap, the project will use a combination of fixed sea moorings and new autonomous underwater vehicles (ocean gliders) to obtain high-resolution observations of small-scale physical processes and the ecosystem response over a year on the Oman coast. These gliders take a measurement every second as they glide up and down the ocean. The instruments create three-dimensional maps of ocean properties with vertical resolutions of centimeters and horizontal resolutions of hundreds of meters. These groundbreaking instruments can remain at sea for several months, much longer than a research vessel, while transmitting data in real time via satellite. The gliders measure temperature, salt, oxygen, plankton, nutrients and ocean currents.
Project goals
We will identify how physical processes control the transport of algal blooms to high-risk areas and which physical, chemical and biological processes can be used to best predict the occurrence of toxic algal blooms. By monitoring the ecosystem for a whole year, we will observe several occurrences of harmful algal blooms and understand the variation behind which processes trigger them and their negative impact.
Through this project, we also strive to build resources in collaboration with the Omani Ministry of Agriculture and Fisheries and Sultan Qaboos University, and to promote alignment with the new Omani National Action Plan for Harmful Algae Blooms. We will run workshops to promote the use of the ground-breaking smart autonomous instrumentation used in this project. It is our ambition that this project will promote a healthier and cleaner sea, as well as increase both food and water safety in the region. We hope that this project can serve as a promotion for future collaborations in the Middle East.