Vertical pelagic habitat of euphausiid species assemblages in the Gulf of California. (May 2017)

• Record Type: Journal Article
• Authors: Ambriz-Arreola, Israel; Gómez-Gutiérrez, Jaime; Franco-Gordo, María del Carmen; Palomares-García, Ricardo J.; Sánchez-Velasco, Laura; Robinson, Carlos J.; Seibel, Brad A.
• Is Part Of: Deep sea research. Volume 123(2017)
• Page Start: 75
• Page End: 89
• Publication Date: 2017-05
• Subjects: Euphausiacea -- Krill -- Species assemblage -- Euphausia gibboides -- Daily vertical migration -- Mexico; Oceanography -- Periodicals; Océanographie -- Périodiques; 551.4605
• DOI: 10.1016/j.dsr.2017.03.008
• Languages: English
• ISSNs: 0967-0637

Abstract

Abstract: We describe the seasonal changes in the horizontal and vertical distribution and abundance of euphausiid species associated with seven physical and 61 biological variables in the Gulf of California (24–31°N). Euphausiid community structure was explored in the epipelagic habitat (<200 m) in January, July, and October 2007 and in epipelagic to bathypelagic habitats (<1400 m depth) in May 2015. Twelve euphausiid species comprising two distinct regional assemblages were identified. Nyctiphanes simplex and Nematoscelis difficilis were the most abundant species (>90%) in all cruises carried out in the 26–31°N region and Euphausia distinguenda in the 24–26°N region (mostly in October >90%). We confirmed that Euphausia gibboides and Nematobrachion flexipes inhabit the mesopelagic habitat, adapted to <1 ml O2 l –1 environmental condition. Although Euphausia lamelligera and N. simplex populations were concentrated in well-oxygenated water (>3 ml O2 l –1 ) near the surface (<50 m), they were also detected in low densities in the hypoxic mesopelagic habitat (250–800 m), but only at oxygen levels less than 0.09 ml O2 l –1 . Stylocheiron affine and Stylocheiron carinatum were numerous well below the seasonal thermocline (100–350 m). Nematoscelis difficilis and N. simplex extended into the hypoxic mesopelagic habitat, but at low densities. Multivariate analyses showed six seasonal and regional krill assemblages, which are characterized by different species (Similarity percentage analysis). Canonical Correspondence Analysis show that, of 68 variables, three abiotic factors (temperature, dissolved oxygen, and OMZ depth) and eight biotic factors (accessory pigments; zeaxanthin and 19'-hexanoyloxyfucoxanthin, and the abundance of six copepod species; Candacia pectinata, Canthocalanus pauper, Centropages furcatus, Rhincalanus nasutus, Scolecithrix danae, and Temora discaudata ), were the most influential variables associated with the vertical distribution and abundance of euphausiids. Krill‒copepod (predator–prey) relationships may be important determinants of daily and seasonal vertical distribution patterns. We conclude that the euphausiid vertical habitat reaches down to 900 m depth (with historical records of six species collected between 1000 and 2280 m) but with lower diversity and abundance in the mesopelagic and bathypelagic habitats than in the epipelagic habitat. Highlights: We quantified krill abundance in mesopelagic-bathypelagic habitats of the Gulf of California. Euphausiids diversity and abundance peak <200 strata during the night and spread out below hypoxic layers during the day. It is confirmed Euphausia gibboides and Nematobrachion flexipes inhabit the mesopelagic habitat of the Gulf of California. Gamma diversity of euphausiids in the Gulf of California is 12 species.