Planktonic and benthic microalgal community composition as indicators of terrestrial influence on a fringing reef in Ishigaki Island, Southwest Japan.

摘要: Abstract Microalgal-based indicators were used to assess terrestrial influence on Shiraho coral reef of Ishigaki Island (Okinawa, Japan). A typhoon occurred 4–5 August 2005 and sampling made three occasions thereafter (6, 8, 11 August). Pre-typhoon was conducted 26 July. The typhoon-enhanced discharges increased nutrient levels (e.g. average NO 3 - -N: 0.088 mg/L pre-typhoon 0.817 mg/L post-typhoon). This elevated chlorophyll-a concentrations by four times shifted phytoplankton composition (spectral class-based) from an initial dominance diatoms green microalgae the bluegreen (cyanobacteria) cryptophytes. Cyanobacteria later more than 200% accounted for as much 80% total chl-a (∼0.29 μg/L), possibly assisted favorable availability. In outer waters, predominated whereas cyanobacteria cryptophytes nearly undetectable. Due detrital decomposition river discharge, CDOM higher in inner reef. Benthic relatively abundant areas close mouth coastal agricultural fields. At these locations, due discharge potentially significant groundwater discharge. Thus, benthic can serve reefs.