The Goldilocks effect: the role of temperature in influencing dinoflagellate growth

Coral reef ecosystems, often referred to as the 'rainforests of the sea,' are vibrant ecosystems formed by millions of living coral polyps. Despite covering less than 1% of the ocean floor, coral reefs deliver vital benefits, including shoreline protection, nutrient cycling, fisheries support, and economic benefits through tourism. However, human activities have led to widespread damage to coral reefs and compromised the resilience and health of these critical ecosystems. This educational activity focuses on an important community of benthic microalgae in the dinoflagellate genus Gambierdiscus, which inhabits the surfaces of macroalgae and seaweed in tropical and subtropical coral reef ecosystems. Certain Gambierdiscus species produce neurotoxins called ciguatoxins (CTX), which can accumulate in food webs when reef fish inadvertently eat these dinoflagellates while grazing on larger algae. Eating contaminated fish can cause the human poisoning syndrome known as ciguatera, which has significant impacts to human health, fisheries, and tourism. This classroom activity focuses on research about the geographic expansion of Gambierdiscus into higher latitudes due to climate-driven ocean warming. Laboratory experiments were conducted to understand the impact of seawater temperature on Gambierdiscus growth, and how ocean warming may affect the geographic distribution and prevalence of these dinoflagellates and ciguatera. The activity provides students with an opportunity to analyze and interpret real growth data collected from these experiments, and the thought questions prompt students to consider the complex interactions within coral reef ecosystems and their responses to environmental changes. Modifications for the blind and low vision are specified, enhancing inclusivity in science education. Together, the data exercises and discussion promote understanding of how ocean warming due to human activities can affect growth and survival of some organisms and impact biological diversity and biogeography.