View in Vital Signs- Thriving Species and Food Web
- Zooplankton
- Indicator
- Zooplankton Index
- Vital Sign Indicator
- Index Value (index value)
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No targets are currently set for this indicator.
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BethElLee Herrmann
- Contributing Partners
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- Last Updated
- 6/5/2024 2:24:27 PM
The Zooplankton Index is a concise way of visualizing the variability of biomass for select taxonomic groups in Northern Washington and Puget Sound regions. This indicator shows the change in annual average biomass of each zooplankton group, calculated from z-scores. Z-scores depict how far the biomass differs from the annual mean. Values closer to zero are near average, while values farther from zero show a greater difference above or below the average in any particular year. While these values do not indicate “good” or “bad” outcomes for zooplankton, they are useful in determining the degree of change these communities encounter over time.
Zooplankton Index reported as z-scores from 2014-2023 for five taxa groups in two regions, Northern Washington (NWA) and Puget Sound (PS). Colors indicate whether the annual average biomass was 1-3 standard deviations (SD) above (positive) or below (negative) the mean. Values are relative to the calculated mean of each region and taxon.
The Zooplankton Index is a concise way of visualizing the variability of biomass for select taxonomic groups in Northern Washington and Puget Sound regions. While these values do not indicate “good” or “bad” outcomes for zooplankton, they are useful in determining the degree of change these communities encounter over spatio-temporal scales.
- In Northern Washington (NWA) waters, total zooplankton biomass (all zooplankton) was well above average in 2015 and 2019, and moderately below average in 2023.
- In Puget Sound (PS), total biomass was high in 2015 and 2017, and moderately high in 2019. Conversely, 2020 and 2021 were low biomass years in Puget Sound with 2018 and 2022-2023 being near average.
- Small crustaceans were well above average in 2019 in NWA and in 2017 in PS.
- Small and large crustaceans generally showed similar patterns to “All Zooplankton,” of which they were the main contributors.
- Large crustaceans were markedly higher than the annual mean in 2015 in both regions, in 2019 in NWA, and 2016 in PS.
- Gelatinous zooplankton biomass was highest in 2014 for both regions, yet dramatically declined during and after the 2015-2016 Pacific marine heatwave.
- Crab larvae were remarkably high in 2017 in both regions.
- Monitoring Program
Puget Sound Zooplankton Monitoring Program
- Data Source
The Puget Sound Zooplankton Monitoring Program (started as the Salish Sea Marine Survival Project in 2014) provides an extensive, ongoing dataset documenting metrics of zooplankton from 15 stations in the southern Salish Sea throughout Northern Washington (NWA) and Puget Sound (PS) (Figure 1). The data included in these Indicators are compiled from 200-µm mesh vertical net tows, which are collected bi-weekly all year round, with lower frequency in the winter. The nets are towed through the full water column, from within 5 m from the bottom, or to a maximum of 200 m, to the surface. Samples are preserved in 5% formalin and are processed by expert taxonomists at the University of Washington, with certain taxa identified to species level. Data are then statistically analyzed to develop indicators of environmental variability.
Please see the Zooplankton Vital Sign Indicators Annual Report for more about methods and the King County Zooplankton Monitoring Annual Report for more details about the broader monitoring program
- Critical Definitions
Taxa of interest
All Zooplankton (total zooplankton biomass) includes all taxa collected, except for Noctiluca (dinoflagellates), eggs, copepod nauplii, and any unidentifiable organisms, as these are extremely small and inconsistently caught in the nets or damaged beyond recognition.
Crustaceans compose the majority of zooplankton biomass in the Salish Sea. This broad taxonomic group consists of several major taxa (copepods, amphipods, krill, shrimp, crabs, etc.), and is separated into size classes (large crustaceans >2.5 mm and small crustaceans <2.5 mm) relevant to forage fish and juvenile salmon diets, including Chinook and coho salmon.
Gelatinous zooplankton consist of cnidarians (e.g., jellyfish and siphonophores) and ctenophores (e.g., comb jellies). These soft invertebrates may have indirect, yet important, linkages to water quality and ecosystem health, and are important prey for pink and chum salmon.
Crab larvae are of high interest in fisheries management, especially several cancrid species, including Dungeness crab (Metacarcinus magister).
Targets are not defined for these indicators. When evaluating trends in the indicators, it is important to note that high biomass of any group would indicate high prey availability for their predators. However, because there is a complex food web in the Salish Sea where sustained predation will decrease biomass, low biomass does not necessarily indicate that the system is in an unhealthier state than when biomass is high.
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Many factors, such as increased ocean-estuary exchange, higher nutrients, and higher temperatures may have affected zooplankton growth, reproduction, and timing during the marine heatwave in 2015-2016, with lingering effects through 2017. The PS residents, which complete their entire life cycles in PS, would be especially affected by these local environmental changes; many of these are smaller crustacean species.
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Populations of larger, oceanic copepod species (mainly seen in NWA) are primarily advected in from the ocean. Therefore, their changes reflect changes in species composition in the coastal populations and changes in the volumes and timing of advection into the Salish Sea, rather than local environmental changes.
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No datasets uploaded.
- Reporting Instructions
No Subcategories for this Puget Sound Indicator.