Shifting Salinity, Shifting Species: Understanding Invertebrate Biodiversity at Keʻehi, Oʻahu, Hawaiʻi

Abstract

Coastal ecosystems are influenced both by natural processes such as freshwater input and sedimentation, and human activities including urban runoff and shoreline modification. Salinity is a key abiotic factor that affects the distribution and diversity of invertebrate communities, which are essential to ecosystem health. This study examines the relationship between salinity and coral reef invertebrate species diversity at two culturally significant sites, Mauliola and Mokauea, in Keʻehi, Oʻahu, Hawaiʻi, both of which are central to Native Hawaiian-led restoration efforts. Quadrat sampling was used to assess invertebrate abundance and diversity across multiple locations at each site. Mauliola, having experienced more intensive dredging and proximity to urbanized stream inputs, was expected to exhibit greater salinity variation and reduced species diversity compared to Mokauea. It was hypothesized that more stable salinity conditions would support higher and more balanced invertebrate diversity. Results indicated that average salinity levels were similar between the two sites and exhibited moderate species diversity. Due to this similarity in mean salinity, the hypothesis could not be directly tested. The absence of a strong correlation between mean salinity and species diversity suggests that other factors, such as nutrient availability, sedimentation, or interspecies interactions may play a more significant role in structuring these communities. These findings contribute to a broader understanding of abiotic influences on biodiversity in Hawaiian coastal ecosystems and underscore the value of ecological monitoring integrated with cultural stewardship. Identifying areas with resilient biodiversity can inform restoration strategies that align with mālama ʻāina values and support environmental and cultural resilience.