Potential impacts of nonalgal materials on water-leaving sun induced chlorophyll fluorescence signals in coastal waters

David McKee, Alex Cunningham, David Wright, Lorraine Hay

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

It has been suggested that Sun induced chlorophyll fluorescence (SICF) signals could be used to estimate phytoplankton chlorophyll concentration and to investigate algal physiology from space. However, water-leaving SICF is also a product of the ambient light field. In coastal waters both algal and nonalgal materials affect the underwater light field. In this study we examine the independent impacts of varying loads of mineral suspended solids (MSS) and colored dissolved organic materials (CDOM) on water-leaving SICF signals using Hydrolight radiative transfer simulations. We show that SICF signals in coastal waters are strongly influenced by nonalgal materials. Increasing concentrations of CDOM and minerals can reduce the water-leaving SICF per unit chlorophyll by over 50% for the concentration ranges explored here (CDOM = 0 to 1 m−1 at 440 nm, MSS=0 to 10 g m−3). The moderate-resolution imaging spectroradiometer (MODIS) fluorescence line height algorithm is shown to be relatively unaffected by increasing CDOM, but performance is significantly degraded by mineral concentrations greater than 5 g m−3 owing to increased background radiance levels. The combination of these two effects means that caution is required for the interpretation of SICF signals from coastal waters.
Original languageEnglish
Pages (from-to)7720-7729
Number of pages10
JournalApplied Optics
Volume46
Issue number31
DOIs
Publication statusPublished - 2007

Keywords

  • nonalgal material
  • sun induced chlorophyll fluorescence signals
  • coastal waters

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