The term jellyfish is taxonomically broad, referring to gelatinous plankton in the phyla Ctenophora (comb jellies) and Cnidaria (all other jellyfish). While jellyfish have been components of pristine marine ecosystems for millennia, recent worldwide increases in the abundance of some jellyfish have been associated with anthropogenic perturbations such as eutrophication (Arai 2001), overfishing (Lynam et al. 2006), climate warming (Mills 2001, Lynam et al. 2004, Purcell 2005), and coastal development (Richardson et al. 2009). Because many jellyfish have a complex life history that includes free-living sexual and asexual phases, populations can increase rapidly when environmental conditions change to favor them.

Jellyfish blooms can disrupt human activities such as fishing, recreational beach use, and power plant operations (Purcell et al. 2007, Richardson et al. 2009). Moreover, jellyfish blooms can substantially alter food webs (e.g., Ruzicka et al. 2007, Pauly et al. 2009) by decreasing energy flow to higher trophic levels (Richardson et al. 2009) and by altering community composition of lower trophic levels through selective feeding (Purcell et al. 2007). Notably, the high degree of diet overlap between jellyfish and forage fish such as herring (Purcell and Arai 2001, Brodeur et al. 2008) is thought to be a driver of observed increases in jellyfish abundances in systems where forage fish are removed (Lynam et al. 2006). After such removals, fish recovery can be impeded by jellyfish predation on eggs and juvenile phases of their fish competitors (Purcell and Arai 2001), effectively preventing the reestablishment of fish populations (Lynam et al. 2006). Chum salmon (Oncorhynchus keta) are one of the few reported predators of jellyfish that occur in Puget Sound (Purcell and Arai 2001, Rice 2007)


Source: Puget Sound Science Review

Moon jellyfish (Aurelia aurita). Photo by Hans Hillewaert, courtesy of USGS.



Recent worldwide increases in the abundance of some jellyfish have been associated with human-caused disturbances to the environment such as eutrophication, overfishing and climate warming.


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Eyes Over Puget Sound: Surface Conditions Report - October 26, 2020

After a relatively warm summer and fall, and La Niña forming in the tropics, stream flows in the Puget Sound region are now relatively normal. Summer in Puget Sound produced lots of algal and organic material in the water and on beaches, which by October have disappeared. Kelp beds look strong in northern Puget Sound and the Straits; and the harvest of the annual chum salmon run is in full swing in Hood Canal. Jellyfish aggregations are visible in Budd and Sinclair Inlets — and some of the jellyfish might conceal a beast of another kind within. Oil sheens on the water are currently numerous.

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Eyes Over Puget Sound: Surface Conditions Report - September 28, 2020

A warm and dry summer ended with a smoky September due to massive wildfires that were followed by strong rain. As a consequence, muddy river plumes in Puget Sound are very visible, especially near the Nooksack River. During summer, many wonderful citizen contributions documented the large formation of organic material in Central Sound and helped us cover the gap in EOPS flight from April-September. By September when we started flying again, a few bays still had red-brown blooms. Nevertheless, schools of fish are abundant, and jellyfish are sparse, which is good news. Meet our new ocean acidification experts.

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Eyes Over Puget Sound: Surface Conditions Report - October 30, 2019

After a dry early summer followed by more than expected rain, rivers mostly remained lower than in 2018. In October air temperatures dropped, but water temperatures remained warm enough for spawning anchovies in South and Central Sound and herring and salmon optimal growth in Whidbey Basin. By the end of October many red-brown blooms vanished, yet the waters of South Sound are still green, adorned with rafts of organic debris in many places. Read what happened the year before in the Puget Sound Marine Waters 2018 Overview.

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Eyes Over Puget Sound: Surface Conditions Report - September 12, 2019

This year, air temperatures were warmer than in previous years, and this pattern is predicted to continue. Precipitation was low and is now improving, yet river flows remain low. By August, Puget Sound surface water temperatures were 0.6 °C warmer across all regions; this could have shifted the timing of optimal temperatures for some marine organisms. In September, blooms are limited to inlets. Jellyfish are abundant in Sinclair Inlet, and anchovies reside in Eld Inlet. Macroalgae are still plentiful. Learn about the benefits of beach wrack and a DNA barcoding project supported by Ecology.

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Eyes Over Puget Sound: Surface Conditions Report - February 21, 2019

Although fall and winter were warm, February brought cold snowy weather and low river flows. Despite colder air temperatures, the productive season has already started in Hood Canal and Holmes Harbor. Puget Sound waters were warmer than expected through January, and the warmest waters were in Hood Canal, possibly creating a thermal refuge for cold-sensitive species such as anchovies. We saw lots of sea lions feasting on anchovies in Case Inlet, and we may have captured some herring spawning activity. Unusual for mid-winter, we saw jellyfish patches in Eld and Budd inlets. See the new publication about ocean acidification featuring twenty-five years of our marine monitoring data!