Climate change and its many repercussions are complex yet important topics where early exposure would clearly benefit students' education. Evidence suggests that using curriculum grounded in real world phenomena enhances both student engagement and conceptual learning. In 2018, four graduate students at the University of Washington developed a week long curriculum for 6-8th grade students focused on a local phenomenon, harmful algal blooms (HABs). The curriculum invites students to investigate the local and global impacts of HABs through presentations, worksheets, videos, readings, and hands-on laboratory activities. The curriculum was implemented and evaluated in four 50-minute class periods at a Seattle middle school, with approximately 125 6th and 7th grade students participating. The lessons integrated concepts from general biology and chemistry in a marine context and were designed in accordance with the Next Generation Science Standards. Over several days, students built a conceptual model of why HABs occur and evaluated the impacts of climate change on blooms from a socio-ecological perspective. Given the opportunity to ground this complex issue in a concrete and relevant phenomena, the students deduced how the climate relates to fishery closures through algae growth and toxin production. We assessed student learning by evaluating the conceptual models they produced before and after the curriculum and through self-assessment surveys. We also revised the lesson plans based on feedback from the participating teachers before making the curriculum publicly available through the University of Washington Program on Climate Change.