The benthic community of each study site is photographed using a Fujifilm Finepix XP130 16.4-Megapixel underwater camera and a PVC photoquadrat frame (18.2cm x 27.0cm). Using a modified CRAMP rapid assessment protocol[17]; Within each site (A, B, and C) five evenly spaced onshore-offshore 10-m transects are photographed at each meter. Images representing 458.8cm2 are analyzed for percent cover of abiotic substrate and benthic fauna using image J software, 25 points per image are analyzed for percent cover using a point intercept method. Herbarium samples are collected for species identification. Species richness, Shannon diversity index, and Simpson index are calculated for each transect.
Invasive species, such as Gracilaria salicornia can thrive in conditions of polluted SGD. This invasive species has a high tolerance for low salinity, which allows it to thrive under SGD conditions by taking advantage of excess nutrients from pollution. This species is so weedy that it can outcompete native species, even it's native relative, Gracilaria coronopifolia, the prized edible limu manauea.
Native species like this Laurencia nidifica are likely to have adapted to natural SGD conditions. Under natural conditions, conditions of SGD influence on the nearshore ecosystem would have led native species to adapt to SGD conditions. It appears that our native species are often unable to outcompete invasive species under conditions of polluted SGD, in combination with other factors such as overfishing.
These SGD seeps are a natural characteristic of Hawaii's shorelines. Yet, when humans influence the watershed and the quanity and/or quality of water reaching these seeps, the seeps can become polluted. Polluted seeps contribute to algal blooms and declines in coral cover and fish abundance.
This project visualizes benthic habitat data from Wailupe, a SGD influenced site on the south shore of Oahu. This data examines the effects of SGD on the inshore reef community in comparison to the offshore reef community, which is not influenced by SGD.