Interdisciplinary service development to provide monitoring and early warnings of harmful algae blooms in the Costa Rican Pacific.

Since 2012 red tides have been increasing in frequency and intensity along the Pacific coast of Costa Rica with substantial impact in eco-tourism, mariculture, and the environment. In 2022, only in Papagayo Peninsula, a coastal eco-tourism hotspot, a total economic loss of $1 million was estimated due to severe red tides happening in the Gulf of Papagayo. Additionally, corals, fish, and marine marketable products died, and shellfish consumption was banned, negatively affecting sales and livelihoods of mariculture producers and fishermen.  These red tide events happening in 2022, triggered the MAReS project (Monitoring Algae blooms using Remote Sensing), a two-year pilot project funded by the Dutch government’s Partners for Water program.

The consortium that launched the MAReS project was formed through an interdisciplinary approach, driven by the goal of mitigating the impacts of red tides on ecosystems and the productive activities dependent on marine and coastal resources. MAReS aims to develop a near-real-time geospatial monitoring service to support timely management and mitigation of red tides in the Costa Rican Pacific, especially in protected areas. This service uses optical satellite data such as the sea watercolor, sea water temperature, and chlorophyll-a, which is calibrated and validated with local measurements, then processed into maps and early red tide alerts, providing key information on the intensity and location of red tides. Combining satellite data with in-situ measurements enhances the accuracy of detection and alert systems. Local measurements include optical monitoring equipment, laboratory water analysis of chlorophyll-a, phytoplankton and citizen observations of watercolor.

MAReS seeks to improve information on the location and intensity of red tides so that: (a) governments can warn against unsafe areas for shellfish collection and consumption to prevent poisoning; (b) environmental organizations can protect marine species; (c) eco-tourism operators know where to conduct activities like diving or sport fishing; (d) the fishing industry can identify optimal areas, avoiding unnecessary fuel costs; (e) mariculture operations can relocate or harvest early; and (f) insurers can offer index-based risk insurance.

The main MAReS results are: over 10,000 km² of the sea monitored with remote sensing technology for potential red tides occurrence in the Pacific Ocean, Costa Rica; over 100 km² of the sea sampled for potential red tides occurrence in the Papagayo Gulf,; installation and operation of an optical monitoring station to monitor the occurrence of red tides in Culebra Bay; in situ monitoring of physic- chemical and biological parameters, phytoplankton characterization and business model development based on annual subscriptions. MAReS provides accurate and timely information on the location and intensity of red tides and changes in water quality, enabling governments, eco-tourism operators, and the fishing industry to make informed decisions and mitigate the negative impacts of this phenomenon. Through interdisciplinary and transdisciplinary efforts, the MAReS project represents a unique and innovative approach. From an interdisciplinary perspective, this project is invaluable as it engages communities dependent on marine resources. Understanding the occurrence and detection of red tides is essential for early warning mechanisms for these communities, productive activities and environmental preservation.