DOI: 10.5061/dryad.cz8w9gj7q
title: Two decades of change in sea star abundance at a subtidal site in Puget Sound, Washington

description: Long-term datasets can reveal otherwise undetectable ecological trends,
 illuminating the historical context of contemporary ecosystem states. We
 used two decades (1997–2019) of scientific trawling data from a subtidal,
 benthic site in Puget Sound, Washington, USA to test for gradual trends
 and sudden shifts in total sea star abundance across 11 species. We
 specifically assessed whether this community responded to the sea star
 wasting disease (SSWD) epizootic, which began in 2013. We sampled at
 depths of 10, 25, 50 and 70 m near Port Madison, WA, and obtained
 long-term water temperature data. To account for species-level differences
 in SSWD susceptibility, we divided our sea star abundance data into two
 categories, depending on the extent to which the species is susceptible to
 SSWD, then conducted parallel analyses for high-susceptibility and
 moderate-susceptibility species. The abundance of high-susceptibility sea
 stars declined in 2014 across depths. In contrast, the abundance of
 moderate-susceptibility species trended downward throughout the years at
 the deepest depths – 50 and 70 m – and suddenly declined in 2006 across
 depths. Water temperature was positively correlated with the abundance of
 moderate-susceptibility species, and uncorrelated with high-susceptibility
 sea star abundance. The reported emergence of SSWD in Washington State in
 the summer of 2014 provides a plausible explanation for the subsequent
 decline in abundance of high-susceptibility species. However, no long-term
 stressors or mortality events affecting sea stars were reported in
 Washington State prior to these years, leaving the declines we observed in
 moderate-susceptibility species preceding the 2013–2015 SSWD epizootic
 unexplained. These results suggest that the subtidal sea star community in
 Port Madison is dynamic, and emphasizes the value of long-term datasets
 for evaluating patterns of change.
description: In each year from 1997 to 2019 (except for 1998), we chartered a
 vessel equipped with a Southern California Coastal Waters Research Program
 (SCCWRP) otter trawl net for an annual research cruise near Port Madison,
 a bay on the west side of Puget Sound, WA. The vessel, which ran each year
 for two days in mid-May, towed the SCCWRP net along the bottom in set
 trawling locations corresponding to four depths: 10, 25, 50 and 70 m. Each
 year, five trawls took place at each depth, corresponding to discrete time
 periods: early morning (~6:00–8:00), morning (~10:00–12:00), afternoon
 (~15:00–17:00), evening (~20:00–22:00), and night (~1:00–3:00). Each trawl
 sampled benthic habitat for ~5 min over 370 m. Following each trawl, all
 sea stars caught were identified to species, counted, recorded, and
 released. This data was ultimately used to test for gradual trends and
 sudden shifts in total sea star abundance during the study period
 (1997–2019). We also obtained data on water temperature collected from
 1999–2017 by the Washington State Department of Ecology at a site ~9 km
 southeast of our trawling sites (47.66001°, –122.4417°) to assess the
 effect of temperature on sea star catch over time. See below for a
 description of each data file pertaining to the analyses conducted by
 Casendino et al. (2023).  List of data files
 included:  
 invertebrates_dataset.csv
 invertebrates_dataset_1997.csv
 trawling_dataset.csv
 trawling_dataset_1999.csv
 WADeptEcology_CTD.csv 
 <strong>invertebrates_dataset.csv</strong> –
 documents invertebrates caught in sampling bottom trawls in Puget Sound,
 WA, from 1999 to 2019. Includes trawl information such as year, date,
 time, and depth. Categorizes invertebrates by informal group (e.g., crab,
 sea star, or shrimp), common name (e.g., vermillion star, sand star, or
 spiny red star), genus species (e.g., <em>Pycnopodia</em>
 <em>helianthoides</em>) and the number caught during a
 particular trawl. <strong>invertebrates_dataset_1997.csv</strong> – documents invertebrates caught in sampling bottom trawls in Puget Sound, WA, in 1997. The row labelled “TRAWL” includes labels to indicate trawl time, where numbers 1, 2, 3, 4, and 5 correspond to afternoon, evening, night, early morning, and morning trawls. Depth is also listed. Sea stars collected during trawls are listed under the “echinoderms” heading by scientific name, and corresponding columns show how many individuals were caught during particular trawls. <strong>trawling_dataset.csv</strong> – includes trawling information from 2000 to 2019. The column labelled “Station Name” includes basic information such as the type of trawl employed and depth sampled, and “Date” includes the day, month and year of each trawl. The exact time and depth of the start and end of each trawl tow are also listed, as well as the Mean Lower Low Water depth. Coordinates of the start and end of trawl tows are listed in degrees decimal minutes form, as well as the distance, speed and direction of each trawl. <strong>trawling_dataset_1999.csv</strong> – reports trawling data from 1989 to 2000, including the same information presented in Dataset_trawlmaster.csv. From 1995 onwards, spatial coordinates are listed in degrees decimal minutes form. <strong>WADeptEcology_CTD.csv</strong> – reports environmental data (including temperature data) collected by the Washington State Department of Ecology from 1999 to 2017 at a site in Puget Sound ~9 km southeast of our trawling sites.