DOI: 10.5061/dryad.pzgmsbcjx
title: Spatio-temporal persistence of zooplankton communities in the Gulf of Alaska

description: Spatial structuring of mid-trophic level forage communities in the Gulf of
 Alaska (GoA) is poorly understood, even though it has clear implications
 for the health of fisheries and marine wildlife populations. Here, we test
 the hypothesis that summertime (May-August) mesozooplankton communities
 are spatially-persistent across years of varying ocean conditions,
 including during the marine heatwave of 2014-2016.  We use
 spatial ordinations and hierarchical clustering of Continuous Plankton
 Recorder (CPR) sampling over 17 years (2000-2016) to (1) characterize
 typical zooplankton communities in different regions of the GoA, and (2)
 investigate spatial structuring relative to variation in ocean
 temperatures and circulation. Five regional communities were identified,
 each representing distinct variation in the abundance of 18 primary
 zooplankton taxa: a distinct cluster of coastal taxa on the continental
 shelf north of Vancouver Island; a second cluster in the western GoA
 associated with strong currents and cold water east of Unimak Pass; a
 shelf break cluster rich in euphausiids found at both the eastern and
 western margins of the GoA; a broad offshore cluster of abundant pelagic
 zooplankton in the southern GoA gyre associated with stable temperature
 and current conditions; and a final offshore cluster exhibiting low
 zooplankton abundance concentrated along the northeastern arm of the
 subarctic gyre where ocean conditions are dominated by eddy activity. When
 comparing years of anomalous warm and cold sea surface temperatures, we
 observed change in the spatial structure in coastal communities, but
 little change (i.e., spatial persistence) in the northwestern GoA basin.
 Whereas previous studies have shown within-region variability in
 zooplankton communities in response to ocean climate, we highlight both
 consistency and change in  regional communities, with interannual
 variability in shelf communities and persistence in community structure
 offshore. These results suggest greater variability in coastal food webs
 than in the central portion of the GoA, which may be important to energy
 exchange from lower to upper trophic levels in the mesoscale biomes of
 this ecosystem.
description: Zooplankton data: taxonomic data for each zooplankton
 taxa identified from Gulf of Alaska CPR transects (2000-2016) was
 spatially summarized within each year into 2 by 2 degree spatial bins
 (Dataset A: "Zooplankton_by_Year.csv"; Bins are numbered 1-41).
 For analysis, data for each taxa was then averaged across all years
 (Dataset B: "Zooplankton_Community_AllYears.csv") and for warm
 vs. cold years (Dataset C:
 "Zooplankton_Community_WarmColdYears.csv"). Hierchical
 Clustering of Principal Components and other analyses were conducted on
 Dataset B to determine the baseline community composition analysis, and on
 Dataset C to determine community patterns during warm years (2004, 2005,
 2015-2017) vs. cold years (2007, 2008, 2010-2012).
 Oceanographic data was downloaded as described in the
 methods: SST data were obtained
 from the NOAA Optimal Interpolation SST, a combined and corrected
 interpolation of data from different platforms (satellites, ships,
 buoys) with a
 daily resolution of 1/4° [30] Ocean surface current data are from
 the Ocean Surface
 Currents Analysis Real-time (OSCAR, version 1) data set
 [31,32]. OSCAR currents, representing the
 geostrophic and ageostrophic flow at 15 m depth, were calculated from
 satellite sea surface height gradients, ocean vector winds, and SST data
 every 5-days on a 1/3° global grid.  Bathymetric data was obtained from
 ETOPO1 dataset, with a 1 arc-minute resolution (doi: 10.7289/V5C8276M).
description: Zooplankton_Community_AllYears.csv: Taxonomic data from CPR
 transects collected from 2012-2016 summarized into 2 by 2 degree lat/long
 cells. Columns include 18 taxa, Lat, Long, Bin ID.
 Zooplankton_Community_WarmColdYears.csv: Taxonomic data from CPR
 transects by year summarized into 2 by 2 degree lat/long cells and
 organized by Temperature Assignment.  Columns include 18 taxa, Lat, Long,
 Bin ID, Temperature. Zooplankton_by_Year.csv: Taxonomic
 data for 18 different taxa listed by Year and Bin.  This sheet was used to
 make the previous two spread sheets used for analysis.