Predicting distribution of microphytobenthos abundance on a reef platform by combining in situ underwater spectrometry and pigment analysis

Abstract

An approach is presented to predict microphytobenthos (MPB) abundance at Heron Reef, Australia using a regression model between chlorophyll-a (chl-a) concentration and field measured spectral reflectance integrated to the blue spectral band of the Worldview-2 (WV-2) sensor. In situ underwater spectral reflectance was measured from benthic sediments and co-located sediment cores were collected to estimate their chl-a concentration. Chl-a features were visually identified in spectral reflectance curves by derivative analysis. Pigment composition analysis of benthic sediments enabled the presence of a relatively homogeneous and living MPB community to be inferred. Field spectral reflectance and chl-a concentration showed a negative correlation in blue and red wavelengths. Regression models between field spectral reflectance resampled to the WV-2 sensor’s bandwidths and chl-a concentration showed the highest coefficient of determination in the blue spectral band of the sensor. This ‘blue band’ model can be further applied to individual pixels of WV-2 images to produce spatially explicit and continuous maps of chl-a concentration, and hence MPB abundance, in Heron Reef.