Gathering, consumption and antioxidant potential of culturally significant seaweeds on O'ahu Island, Hawai'i

Gathering wild plants provides multiple benefits to indigenous cultures along physical, spiritual and psychological dimensions. Wild-gathered seaweeds (limu) are a prominent component of Native Hawaiian diet and culture, but have been under-studied for their nutritional benefits and cultural use. In order to investigate the contemporary levels of wild seaweed gathering and consumption, the factors influencing the prevalence of gathering, and to explore potential disease-preventative benefits wild seaweeds provide, this study uses a combination of ethnographic, pharmacological and ecological approaches to address the following questions: (1) How common is wild seaweed gathering and consumption among youth on O'ahu today?, (2) Which demographic and familial characteristics predict gathering?, (3) What is the perception of change among gatherers in the abundance of wild seaweeds over time?, (4) How does the antioxidant capacity of wild seaweeds differ from that of cultivated seaweeds consumed on O'ahu?, and (5) How may eutrophication influence the antioxidant values of wild seaweeds? Levels of gathering and consumption were assessed with surveys of public high school juniors and seniors as well as through semi-structured interviews with adult limu gatherers. Antioxidant activity was assessed with laboratory assays. One-fifth of surveyed students had gathered wild seaweeds and one-third had consumed them, with a larger proportion of gathering and consumption among Native Hawaiian students. Familial gathering was the strongest predictor of student gathering, with Hawaiian ethnicity being a stronger predictor among male students compared to female students. As opposed to pre-Contact Hawaii, more male than female Hawaiian students reported gathering wild seaweeds. There was a consistent perception of decline in abundance of wild seaweeds among limu gatherers with harvest by non-traditional means and pollution as the most commonly cited reasons for this decline. Wild seaweeds provided higher levels of antioxidants than cultivated seaweeds, and eutrophication was correlated with a decline in antioxidant power. Taken together, these results demonstrate that traditional gathering practice has persisted and adapted through time despite urbanization, commercialization and environmental degradation and also that wild seaweeds likely provide a greater level of a particular disease-preventative property than their cultivated counterparts, with nitrogen loading potentially decreasing this benefit. This suggests that conservation of nearshore environments to promote native seaweeds would also support Native Hawaiian cultural practice and health and that promoting traditional gathering protocol would support more sustainable harvest.