POSTER Session 4

CONCENTRATION THRESHOLDS FOR THE DETECTION OF MULTIPLE ZOOPLANKTON GROUPS FROM OCEAN COLOR SIGNALS

Zooplankton are keystone organisms that provide a critical link between primary production and higher order predators in the marine food web, as well as facilitating the sequestration of carbon within the ocean. There is considerable interest in the detection of zooplankton swarms from satellite ocean color signals. In this study, spectral absorption properties of key surface-aggregating zooplankton have been measured using a Point Source Integrating Cavity Absorption Meter. These absorption spectra were used to model the impact of each group on remote sensing reflectance signals and determine a concentration threshold that would generate a distinguishable signal from ocean color data. Results indicate that the spectral shape of absorption did not vary considerably between species, with most organisms showing a peak at around 480 nm, characteristic of the pigment astaxanthin. However, detection thresholds vary significantly between groups, with larger organisms such as northern krill requiring far lower concentrations than the smaller copepod species. From this, a full spectral matching method can be developed using a standard Case-2 model, where anomaly associated with astaxanthin rich species is distinguished. With knowledge of in situ populations, specialized bio-optical models containing target zooplankton species can be applied to the anomalous pixels, providing optical closure and producing order of magnitude concentration estimates. This method produced concentration estimates of surface swarms of the copepod Calanus finmarchicus in the northern Norwegian Sea and the Gulf of Maine. We also present the first evidence of ability to observe swarms of the Southern Ocean krill species Euphausia superba from space.

Cait McCarry, University of Strathclyde, United Kingdom, [email protected], https://orcid.org/0000-0001-9051-3907

David McKee, University of Strathclyde, United Kingdom, [email protected]

Sünnje Basedow, Arctic University of Norway (UiT), Norway, [email protected]

Emlyn Davies, SINTEF Ocean, Norway, [email protected]

Kim Last, Scottish Association for Marine Sciences, United Kingdom, [email protected]

Catherine Mitchell, Bigelow Laboratory for Ocean Sciences, USA, [email protected]

Rebekah Shunmugapandi, Bigelow Laboratory for Ocean Sciences, USA, [email protected]

Vengamanaidu Modepalli, Marine Biological Association, United Kingdom, [email protected]

Claire Waluda, British Antarctic Survey, United Kingdom, [email protected]

Simeon Hill, British Antarctic Survey, United Kingdom, [email protected]

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