This activity guides the analysis of a published scientific figure from a study that investigated whether periwinkle snails contribute to salt marsh die-offs.

Periwinkle snails graze on Spartina cordgrass, an important salt marsh plant. When cordgrasses are stressed during droughts, snail grazing intensifies, causing them to die off in localized areas, which forms bare patches called mudflats. Over time, snails move to areas with healthier grass, creating a “snail front.” The figure shows the density of periwinkle snails and biomass of cordgrass in a Georgia salt marsh at three time points: at the beginning of the study (top), after 6 months (middle), and after 12 months (bottom). The “Educator Materials” document includes a captioned figure, background information, graph interpretation, and discussion questions. The “Student Handout” includes a captioned figure and background information.