Does the nutritional state of jellyfish vary with season along the Pacific Northwest Coast?
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Date
2021-06
Authors
Li, Ya Lin
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Cnidarian jellyfish are ubiquitous predators of pelagic communities, but little is known
about their phenology and how food availability affects their nutritional status. Starved medusae
tend to decrease somatic growth to allocate resources towards gonad development, thus a ratio of
gonad to bell size might help determine the nutritional state of hydromedusae. We hypothesized
that when food is scarce, C. gregaria and E. indicans will have larger gonads relative to their
body size. I conducted starvation experiments to directly test how bell diameter and gonad area
vary with food availability. The same two species of hydromedusae were also collected in a
period of low primary productivity (winter) and high primary productivity (summer) along the
North California Current System. ImageJ was used to analyze photos of the formalin-preserved
specimens to obtain morphological measurements and create a gonadal index (gonad area/bell
area). As the preservation method caused a loss in biomass of the collected medusae, we made a
correction factor to convert the measurements of the preserved organisms to live ones. The
medusae showcased slightly higher gonadal index in the medusae during winter than summer
indicating an increased effort towards reproduction when resources are depleted. Understanding
the links between oceanographic conditions and population dynamics of gelatinous predators
will allow us to better predict their effects on zooplankton community dynamics.
Description
27 pages
Keywords
Cnidarian jellyfish, hydromedusae, Pacific Northwest