Satellite detection of dinoflagellate blooms off California by UV reflectance ratios

Abstract

As harmful algae blooms are increasing in frequency and magnitude, one goal of a new generation of higher spectral resolution satellite missions is to improve the potential of satellite optical data to monitor these events. A satellite-based algorithm proposed over two decades ago was used for the first time to monitor the extent and temporal evolution of a massive bloom of the dinoflagellate Lingulodinium polyedra off Southern California during April and May 2020. The algorithm uses ultraviolet (UV) data that have only recently become available from the single ocean color sensor on the Japanese GCOM-C satellite. Dinoflagellates contain high concentrations of mycosporine-like amino acids and release colored dissolved organic matter, both of which absorb strongly in the UV part of the spectrum. Ratios <1 of remote sensing reflectance of the UV band at 380 nm to that of the blue band at 443 nm were used as an indicator of the dinoflagellate bloom. The satellite data indicated that an observed, long, and narrow nearshore band of elevated chlorophyll-a (Chl-a) concentrations, extending from northern Baja to Santa Monica Bay, was dominated by L. polyedra. In other high Chl-a regions, the ratios were >1, consistent with historical observations showing a sharp transition from dinoflagellate- to diatom-dominated waters in these areas. UV bands are thus potentially useful in the remote sensing of phytoplankton blooms but are currently available only from a single ocean color sensor. As several new satellites such as the NASA Plankton, Aerosol, Cloud, and marine Ecosystem mission will include UV bands, new algorithms using these bands are needed to enable better monitoring of blooms, especially potentially harmful algal blooms, across large spatiotemporal scales.

The distribution of mycosporine-like amino acids in phytoplankton across a Southern Ocean transect

“…Given the relationship between diatoms, porphyra-334, and silica present at the polar front, porphyra-334 may serve as an alternate proxy for the location of the PF zone. Kahru et al (2021) demonstrated the ability to differentiate neighboring algal blooms of differing taxonomic composition via the remote detection of UVR spectral bands, likely due to the presence of MAAs. However, this differentiation was hypothesized to be based on the presence of the MAA palythene, which has a peak absorption at 360 nm in the long-wavelength UVA region.…”

“…Indeed, observed variability in MAA production as a function of season (i.e., summer peak) and depth (surface maximum) suggest a tight coupling between the magnitude of UVR forcing and physiological response in phytoplankton and other marine organisms (Morrison and Nelson, 2004;Nuñez-Pons et al, 2018 and references therein), while the inability of certain species to produce MAAs imply that UVR may act as a forcing on phytoplankton community composition (Ha et al, 2018;Nuñez-Pons et al, 2018). In the future, absorption of UVR by MAAs may enhance satellite taxonomic characterization via remote sensing of UVR spectral bands (Kahru and Mitchell, 1998;Kahru et al, 2021). Recently, Kahru et al (2021) demonstrated that remote detection using UVR spectral bands was able to differentiate neighboring algal blooms of differing taxonomic composition, likely due to the presence of MAAs.…”

“…In the future, absorption of UVR by MAAs may enhance satellite taxonomic characterization via remote sensing of UVR spectral bands (Kahru and Mitchell, 1998;Kahru et al, 2021). Recently, Kahru et al (2021) demonstrated that remote detection using UVR spectral bands was able to differentiate neighboring algal blooms of differing taxonomic composition, likely due to the presence of MAAs. Various studies have been conducted to assess phytoplankton MAA composition in coastal marine and freshwater systems and in laboratory cultures (Whitehead and Vernet, 2000;Llewellyn and Harbour, 2003;Carreto et al, 2018), yet little is known about the abundance and composition of MAAs throughout the world's oceans, as few studies have been conducted on large spatial scales.…”

Chlorophyll-a and Sea Surface Temperature Changes in Relation to Paralytic Shellfish Toxin Production off the East Coast of Tasmania, Australia

“…The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) project will help with large-scale detection, collecting high-resolution data in the ultraviolet spectral band, recently shown to distinguish blooms of the dinoflagellate Lingulodinium polyedra. Other products including chl-a, net primary production, phytoplankton pigment concentrations, and spectral phytoplankton absorption coefficients will help measure biomass and decipher phytoplankton groups and species from one another [32,33]. The PACE satellite may be able to distinguish the spectral signature of Alexandrium around Tasmania, helping to detect and monitor the spatial extent [32].…”

Underway Hyperspectral Bio-Optical Assessments of Phytoplankton Size Classes in the River-Influenced Northern Gulf of Mexico

“…Contamination by reflected light off ship structures or possibly associated with foam or wave facets may have also been a factor. While our application of the phytoplankton size class algorithm would be expected to be relatively insensitive to uncertainties in wavelengths at 412 nm or less, accurate estimates of Rrs in this wavelength range could nonetheless be very useful for certain applications such as characterizing properties of organic matter [41] and possibly certain phytoplankton classes [42]. Further investigation of the sources of variability in UV Rrs is warranted.…”