North Pacific Anadromous Fish Commission

Technical Report 18

Table of Contents

Dynamics of Phytoplankton Biomass in the Gulf of Alaska Derived from Sentinel 3 OLCI Imagery

Vishnu Perumthuruthil Suseelan and Maycira Costa

Abstract Excerpt:
Oceanic phytoplankton are responsible for half of the world’s primary production (Field et al. 1998; Chassot et al. 2010), constitute 90% of the ocean’s primary productivity, and are highly diverse in size, shape, and bio- geochemical function (Chassot et al. 2010). However, in the iron-poor open ocean waters of the Gulf of Alaska (GoA), phytoplankton biomass is generally very low (< 0.5 mg/m3) throughout the year, with weak seasonal or interannual variability (Evans and Parslow 1985; Vinogradov et al. 1997; Brickley and Thomas 2004; Childers et al. 2005; Peña and Varela 2007). For example, Vinogradov et al. (1997) evaluated the phytoplankton standing stock from 1978 to 1986 for the Pacific Ocean using the Coastal Zone Color Scanner (CZCS) and reported no significant interannual variability. Banse and English (1999) observed that annual mean Chlorophyll-a (Chl-a) concentration derived from the CZCS sensor showed no significant seasonal variation for the Subarctic Pacific. More recently, Westberry et al. (2016) has shown that Chl-a in the Northeast Subarctic Pacific remains invariant throughout the year. Thus this region is considered a high-nutrient low-chlorophyll region (HNLC) where iron is the primary limiting factor for the phytoplankton production (Miller et al. 1991; Brickley and Thomas 2004; Childers et al. 2005; Aguilar-Islas et al. 2016). Despite that, the Subarctic North Pacific primarily supports Pacific salmon (Oncorhynchus spp.) originating from Canada, the United States, Russia, Japan, and Korea (Beamish 2017). Pacific salmon spend a minimum of 50% of their life in coastal and open ocean waters as foragers; however, very little is known about their distribution patterns in the open ocean (Groot and Margolis 1991; Beamish 2017). Furthermore, studies have shown that Pacific salmon in the Subarctic North Pacific face unprecedented effects from changing climate (Abdul-Aziz et al. 2011; Healey 2011; Irvine and Fukuwaka 2011; Ruggerone and Irvine 2018). Thus, it is essential to understand how climate variability in the North Pacific Ocean and the associated changes in the physical and biological environment influence the abundance, distribution, migration, growth, and survival of Pacific salmon.

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Suseelan, V.P., and M. Costa.  2022.  Dynamics of phytoplankton biomass in the Gulf of Alaska derived from Sentinel 3 OLCI imagery.  N. Pac. Anadr. Fish Comm. Tech. Rep. 18: 25–32.