Light-Based Technology Boosts Zooplankton to Aid Coral Survival

By Muhammad OsamaReviewed by Laura ThomsonFeb 17 2025

In an article recently published in the journal Limnology and Oceanography: Methods, researchers introduced the Underwater Zooplankton Enhancement Light Array (UZELA), a novel technology designed to increase zooplankton abundance and improve coral feeding, particularly during bleaching events. The goal was to address the urgent need for effective strategies to support coral reefs, which are important for marine ecosystems and coastal economies but face significant threats from climate change and human activities.

Importance of Coral Reefs

Coral reefs are important ecosystems that provide shoreline protection, marine habitats, and support for fisheries and tourism, with an estimated global economic value of nearly $10 trillion. However, they face severe threats from climate change, pollution, and overfishing, leading to rapid coral health and biodiversity decline. Coral bleaching, triggered by rising sea temperatures, disrupts the symbiotic relationship between corals and their algae, reducing energy intake and increasing reliance on external food sources like zooplankton.

About the Research: Assessing UZELA’s Effectiveness

In this paper, the authors developed UZELA, an autonomous, submersible light system that attracts zooplankton at night. By leveraging the natural phototactic behavior of zooplankton, UZELA increases local zooplankton concentrations, thereby enhancing coral feeding opportunities. This device operates on a single battery for up to six months, activating for one hour each night. This approach supports coral growth and resilience while broader efforts to mitigate local environmental stressors continue.

The researchers evaluated UZELA's effectiveness in increasing zooplankton abundance and enhancing feeding rates in two Hawaiian coral species, Porites compressa and Montipora capitata. They conducted a hybrid experiment combining tank and field methods to test four important hypotheses: including, (1) Zooplankton concentrations are higher over UZELA lights than in control areas, (2) Corals exposed to UZELA ingest more zooplankton, (3) UZELA has a stronger effect on feeding in heat-stressed corals, and (4) The response to UZELA differs between the two coral species.

The study involved temperature manipulation and feeding trials to assess UZELA's impact. Coral fragments were collected from reefs near the Hawai‘i Institute of Marine Biology and acclimated for two weeks under controlled conditions. Heat stress was induced in some specimens to simulate natural bleaching conditions. UZELA units were deployed in situ, while control setups lacked light intervention.

Zooplankton abundance was measured using filtration, and coral feeding rates were determined by counting ingested zooplankton within coral polyps. Environmental conditions were monitored with light sensors and temperature loggers, and gut content analysis provided insights into coral ingestion rates. This approach allowed authors to evaluate UZELA’s potential to enhance coral nutrition under normal and heat-stressed conditions.

Key Findings and Insights: Impacts on Both Species

The outcomes demonstrated that UZELA significantly increased zooplankton concentrations compared to control setups and natural reef environments. Zooplankton abundance was up to seven times higher over UZELA than in blank controls and four times higher in natural reef conditions. This increase was directly correlated with enhanced coral feeding rates, as corals exposed to UZELA ingested 10 to 50 times more zooplankton than those in control conditions, regardless of their bleaching status.

Notably, Montipora capitata exhibited a greater increase in feeding rates than Porites compressa, indicating species-specific responses to UZELA. Heat-stressed P. compressa also showed higher feeding rates than their non-bleached counterparts, suggesting that UZELA could provide key nutritional support during thermal stress. UZELA also influenced zooplankton community composition, increasing the presence of crab zoea, a preferred food source for corals. These results highlight UZELA’s potential as a key tool for supporting coral resilience in the face of climate change and environmental stressors, with possible benefits extending to other marine organisms that rely on similar food sources, like giant clams.

Practical Applications of UZELA Technology

This research has significant implications for coral conservation and restoration. UZELA can support coral nutrition by enhancing zooplankton availability and promoting growth and resilience against environmental stressors. This is particularly valuable for coral restoration projects, where the survival and health of transplanted corals are crucial.

UZELA’s ability to attract specific zooplankton species, such as crab zoea, a preferred coral food source, suggests its potential to optimize feeding strategies in coral nurseries and restoration sites. Integrating UZELA into broader coral management strategies could enhance reef ecosystem sustainability and mitigate the impacts of climate change.

Conclusion and Future Directions

In summary, UZELA represents a significant advancement in coral conservation by enhancing zooplankton abundance and boosting coral feeding rates. These findings suggest that this technology could improve coral resilience and support restoration efforts amid ongoing environmental challenges.

Future work should explore large-scale deployments of UZELA to assess its long-term effects on coral health and ecosystem dynamics across diverse reef environments. Optimizing illumination parameters could further enhance its effectiveness. As climate change threatens coral reefs, integrating UZELA into broader conservation strategies may provide a critical tool for sustaining and restoring these fragile ecosystems.

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