ESPINOSA-LEAL AND LAVANIEGOS: SEASONAL VARIABILITY OF PELAGIC AMPHIPODS OFF BAJA CALIFORNIA DURING LA NIÑA 2011 AND COMPARISON WITH A “NEUTRAL YEAR” (2005) CalCOFI Rep., Vol. 57, 2016 SEASONAL VARIABILITY OF PELAGIC AMPHIPODS OFF BAJA CALIFORNIA DURING LA NIÑA 2011 AND COMPARISON WITH A “NEUTRAL YEAR” (2005) LADY LILIANA ESPINOSA-LEAL LADY LILIANA ESPINOSA-LEAL BERTHA E. LAVANIEGOS Departamento de Oceanografía Facultad de Departamento de Oceanografía Biológica Ciencias Naturales y Oceanográficas CICESE Universidad de Concepción Carretera Ensenada-Tijuana No. 3918 Barrio Universitario s/n, Concepción Zona Playitas. Apdo. Postal 360 Casilla 160-C, Concepción, Chile 22860 Ensenada, Baja California, México ABSTRACT INTRODUCTION We describe the seasonal variation of hyperiid Hyperiid amphipods are marine pelagic crustaceans. amphipods in oceanic waters between Punta Eugenia The ecology of hyperiids is better known in temperate and Punta Abreojos, Baja California, during 2011, a and polar regions due to their importance in food webs cool year due to the influence of La Niña. Mean sea (Dalpadado et al. 2001; Armstrong et al. 2005; Collins surface temperature in the study area was similar from et al. 2008). They have been found in stomach con- January to July (16˚–17˚C) but cooler than usual, with tents of fishes and vertebrates from tropical and sub- anomalies of –1 to –3˚C in the context of 1997–2013. tropical regions (Repelin 1978; Satoh 2004; Mostarda Further, SST increased 3˚C in October, restoring the et al. 2007). Amphipods exhibit symbiotic or parasit- typical temperature during this month (21˚C). Verti- oid relationships with gelatinous organisms such as salps, cal salinity profiles were also similar during January, ctenophores, siphonophores, and medusae (Laval 1980). April, and July, showing the influence of subarctic Amphipod species have been used as indicator organisms water in the upper layer (33.3–33.7 psu), while in because they are diverse and respond rapidly to climate October a range of higher values (33.5–33.8 psu) was events like El Niño and La Niña (Gasca et al. 2012), to observed due to the influence of subtropical water. We decadal changes (Lavaniegos and Ohman 1999), and to recorded 63 hyperiid amphipod species in 2011, the the influence of mesoscale circulation (Gasca 2004; Gasca lowest number in January and the highest in October and Suarez-Morales 2004; Lavaniegos and Hereu 2009). (17 and 54, respectively). Despite seasonal changes in Few studies describing species composition in tropical diversity, few species (Eupronoe minuta, Primno brevi- regions have addressed the effects of climate variability. dens, Lestrigonus schizogeneios, and Simorhynchotus anten- Gasca et al. (2012) analyzed the seasonal and interannual narius) were the most abundant throughout the year. variability of hyperiids off the Jalisco coast during 1995– The exception was the warm-water species Lestrigonus 98. They observed a seasonal pattern, with one period bengalensis, which was the second most abundant in influenced by cool water from the California Current October, indicating the influence of subtropical oce- (February–June) and another period influenced by warm anic water. Similarity analysis showed similar com- water from the North Equatorial Countercurrent (July– munities for spring and summer, while winter and December). Species richness and evenness were higher autumn were very dissimilar from each other and dif- in the first, whereas Hyperioides sibaginis and Lestrigonus fered from the spring–summer cluster. However, the bengalensis dominated in the second. These species were species with highest contribution to similarity were particularly abundant during El Niño 1997–98. Further, the same (E. minuta, L. schizogeneios, and P. brevidens) Valencia et al. (2013) compared amphipod assemblages in but with different proportions. A matrix of environ- Panama Bay during the wet and dry seasons of 2007–08. mental variables was correlated with the amphipod The most abundant species were also H. sibaginis and L. similarity matrix through a BIOENV analysis. The bengalensis, with less diversity in the neritic zone during best combination of environmental variables (ρS = the rainy season. 0.644) was the 10 m depth temperature, 10 m depth Another eastern Pacific region analyzed for seasonal salinity, mixed layer depth, stratification in the upper variability in hyperiid abundance is the California Cur- 100 m, and zooplankton volume (this last used as a rent (CC). Studies have been conducted in the Santa proxy for host availability). Finally, when the commu- Barbara Channel (Brusca 1967a,b), off the Oregon nity structure was compared with data from a previous coast (Lorz and Pearcy 1975), and off Baja California amphipod study (2005), we found that species com- (Lavaniegos and Hereu 2009). These studies showed a position was very similar, but seasonal differences in mainly oceanic distribution and increasing abundance the abundance of 30 of the 52 common species per- during the course of the year. Brusca (1967a) performed sist possibly due to the effects of La Niña. stratified sampling between summer 1962 and spring 132 ESPINOSA-LEAL AND LAVANIEGOS: SEASONAL VARIABILITY OF PELAGIC AMPHIPODS OFF BAJA CALIFORNIA DURING LA NIÑA 2011 AND COMPARISON WITH A “NEUTRAL YEAR” (2005) CalCOFI Rep., Vol. 57, 2016 1963 that suggested vertical migration for Streetsia chal- water is modified as a result of solar warming and mix- lengeri, Lestrigonus schizogeneios, and Primno brevidens (the ing with subtropical water (Lynn and Simpson 1987). latter two reported as Hyperia bengalensis and Primno There is high mesoscale activity such as fronts, eddies, macropa). Lorz and Pearcy (1975) did not find evidence and squirts (Soto-Mardones et al. 2004; Jerónimo and of vertical migration off Oregon over a longer period Gómez-Valdés 2007). (1963–67) though only two strata were sampled (0–150 The study area is located in the subtropical sector of y 150–450 m). They observed some interannual variabil- the CCS between Punta Eugenia and Punta Abreojos ity, which was associated with a warm year in 1963, some (fig. 1). Punta Eugenia is considered the highest coastal species (Hyperia medusarum, Hyperoche medusarum, Paraph- prominence of the CCS and a zone of oceanographic ronima gracilis, S. challengeri, and Tryphana malmi) present- transition (Durazo and Baumgartner 2002; Jerónimo and ing higher abundances in the offshore region. Gómez-Valdés 2006), with upwelling occurring year The most recent study on seasonal variation in the round (Zaytsev et al. 2003; Torres and Gómez-Valdés CC covered an extended area off north and central Baja 2015). The equatorward flow prevails to the south of California in 2005, and found minimum abundance of Punta Eugenia though the influence of the equatorial total amphipods in January and maximum in October current system is perceived, mainly the North Equato- (Lavaniegos and Hereu 2009). Similarity analysis showed rial Countercurrent, which flows eastward to the coasts a group associated with the main flow of the CC (Vibilia of Central America and gains strength from August to armata, Lestrigonus schizogeneios, Eupronoe minuta, and January (Kessler 2006). This promotes the entrance of Primno brevidens), and faunistic identity for some meso- subtropical water off southern Baja California, slightly scale structures. Based on that study, the objective of the increasing surface salinity. present research is to characterize the seasonal variation in hyperiid amphipod abundance during 2011 and elu- Sampling and Taxonomic Analysis cidate the influence of La Niña 2010–12. The selected Zooplankton samples were taken during four IME- study area, between Punta Eugenia and Punta Abreojos COCAL cruises performed in 2011 (fig. 1). The sam- (fig. 1), has high presence of tropical species and is more pling dates for the selected study were January 1–2, April vulnerable to cooling. 22–25, July 14–17, and October 17–19. Oblique tows The 2010–12 La Niña event was intense and pro- were performed at 0–200 m depth using a bongo net of longed in the Pacific Ocean. It started in July 2010, 500 μm mesh width and 71 cm mouth diameter. Filtered enhanced at the end of 2010 (Nam et al. 2011; Boening water volume was recorded with a flowmeter in front of et al. 2012; Feng et al. 2013), and subsequently decreased the net. The zooplankton samples were preserved with in June–July 2011, though a second pulse occurred from 4% formaldehyde buffered with sodium borate (Smith late 2011 to mid-2012 (Hu et al. 2014). In the California and Richardson 1977). Hydrocasts were made with a Current System (CCS), intense upwelling was recorded Seabird CTD in the upper 1000 m to obtain tempera- in summer 2010, with negative temperature anoma- ture and salinity data. lies (1˚–2˚C) and low oxygen levels at some locations Thirty-five samples were analyzed for hyperiid amphi- (Nam et al. 2011). SST anomalies off Baja California pods. Two coastal shelf stations (bottom <200 m depth) reached more negative values during La Niña 2010–12 where amphipods were scarce were excluded (fig. 1). than during La Niña 1999–2000, particularly in October All amphipods in the sample were counted and identi- 2010 and January 2011 (Bjorkstedt et al. 2011). Chloro- fied to species using the taxonomic keys given by Bow- phyll concentration presented positive anomalies and the man (1973), Brusca (1981), and Vinogradov et al. (1996). zooplankton contained abundant medusae year round (Bjorkstedt et al. 2012; Lavaniegos et al. 2015). Data Analysis Similarity of amphipod communities was analyzed METHODS using the Bray-Curtis index for the complete abun- dance database (35 samples x 63 species). We prepared Study Area a dendrogram based on the similarity matrix using the The CCS is one of the large marine eastern bound- group average. Statistical significance of clusters was ary upwelling ecosystems, and presents high variability established with the SIMPROF test (PRIMER v.6; at different time scales. The strength of the current and Clarke and Warwick 2001).