UC Santa Cruz

The generalized bio-optical transition from oligotrophic blue to mesotrophic green waters has enabled remote measurement of oceanic ecosystems under conditions in which the optically relevant water mass constituents covary with the primary phytoplankton photopigment, chlorophyll a (Chla). This assumption, known as case-1, is generally incorrect within coastal and inland water bodies, where external factors, such as riverine discharge and sediment resuspension, also modify the concentrations of organic and inorganic constituents beyond the ranges anticipated for natural oceanic ecosystems. New approaches to characterize aquatic ecosystems without relying on case-1 criteria are proposed here using measurements of apparent and inherent optical properties. The methods applied in this work include bio-optical modeling and analyses of in situ, airborne, and satellite radiometric measurements of oceanic, coastal, and inland water ecosystems. Key findings are that: satellite phytoplankton datasets underestimate phytoplankton biomass in coastal ocean regions when default atmospheric correction methods are applied (Chapter 1); the expansion of spectral range for above-water radiometric measurements improves the accuracy of colored dissolved organic matter algorithms (Chapter 2); and hyperspectral beam-attenuation meters can accurately predict Chla without relying on empirical relationships between organic and inorganic particle populations (Chapter 3). The bio-optical advances presented here improve measurement capabilities for optically complex waters and are relevant to global (i.e., oceanic, coastal, and inland) water bodies. Finally, this work supports the perspective that bio-optical approaches should be consistent with electromagnetic theory or other fundamental principles - rather than requiring a partition between waters that satisfy versus fail empirical open ocean criteria - to incorporate a greater diversity of global aquatic ecosystems.