Fig 1.
Gulf of Ulloa and offshore region showing the sampling grid (symbols) and bathymetry (m, shaded blues). Stations sampled varied by cruise (see S1 Table). The 200 m isobath separates coastal from oceanic stations (round and triangle symbols, respectively). Red solid line indicates the transect used in vertical profiles. Numbers are transect-lines and stations in decimals are indicated for Line 130. Topographic chart from GEBCO (https://www.gebco.net/data_and_products/gridded_bathymetry_data/gebco_2019/gebco_2019_info.html).
Table 1.
IMECOCAL cruises with dates and number of zooplankton samples used in taxonomic identification.
Cruise dates correspond to the area considered in the present study (see Fig 1).
Fig 2.
Temperature (a–g) and salinity (h–n) in the upper 200 m along the line 130 during the summers of 2002–2008.
Fig 3.
Climatic context during 2002–2008.
Pacific basin conditions as indicated by the Oceanic El Niño Index (ONI) from region 3.4 (a), and surface temperature anomalies in the study region (b). Letter S indicate the summer.
Fig 4.
Distribution of hyperiid amphipods.
Total amphipods distribution in the Gulf of Ulloa and offshore region during the annual cycle 2005 (a) and the summers of 2002–2008 (b). Red dashed line indicates the onshore/offshore station divide.
Fig 5.
Abundance of hyperiid amphipods.
Mean (± 95% confidence interval) of total hyperiids in the oceanic region off southern Baja California (a, c) and the Gulf of Ulloa (b, d), during the annual cycle 2005 (a–b) and the summers of 2002–2008 (c–d). Data transformed with log10[x+1]. The summer long-term mean is indicated by the dashed line; numeric values express geometric means.
Fig 6.
Patterns of interannual variability.
Mean (± 95% confidence interval) in species groups showing an increase in 2007 (a), decreasing in 2003 (b), or increasing in 2004 (c).
Table 2.
Interannual comparisons of hyperiid species.
Abundances of dominant, common, and sparse species compared across years using the Kruskal-Wallis test.
Fig 7.
Clustering of sampling stations based on abundances of 75 species. Clusters formed at a distance linkage of 15 (cutoff line in red) designed by letters (A, B, C), and subgroups by numbers. In the x-axis the sampling stations are shown with symbols in color indicating the year.
Fig 8.
Geographic distribution of clusters.
Clusters defined in Fig 7 are shown and sea surface contours (°C) were added as a reference to climatic conditions. Uncolored triangles pertain to cluster B (no subgroup), and black points indicate stations without amphipods.
Fig 9.
Species contribution in clusters.
Stacked geometric means (a) and contribution to similarity (b) of main species in clusters defined in Fig 7. The selected species are a combination of the four with highest similarity in each cluster.
Fig 10.
Species composition in September 2007.
Stacked geometric means of the main species in the coastal shelf and offshore region.
Fig 11.
Gelatinous zooplankton in the offshore region and coastal shelf.
Mean (± 95% confidence interval) of cnidarian and ctenophores (a), and tunicates (b).
Table 3.
Interannual comparisons of gelatinous groups.
Abundance of gelatinous groups compared with the Kruskal-Wallis test.
Table 4.
Correlation between hyperiids and potential gelatinous hosts.
Spearman correlation between abundances of hyperiid amphipod species and gelatinous zooplankton groups.