Natural variations in estuarine fish, fish odor, and zooplankton photobehavior

ABSTRACT

Fish odor induces predator avoidance behaviors in zooplankton, like vertical migration, by making zooplankton more responsive to light. Odor cues that alter behavior in marine crustacean zooplankton in the laboratory include sulfated glycosaminoglycans (sGAGs) derived from fish body mucus. Few studies quantify these cues in estuarine/marine environments or assess whether laboratory studies reflect natural scenarios. We collected fish and water samples weekly in Broadkill River, Delaware, USA. We used field-collected water in colorimetric assays to determine the concentration of sGAG-equivalent molecules and in behavioral assays with a zooplankton model, brine shrimp (Artemia spp.) nauplii, which only descend in response to downwelling light after fish odor exposure. Fish quantity was positively related to sGAG-equivalents and zooplankton photosensitivity, indicated by descent responses at lower light levels and across a broad intensity range. Our results support that fish odor concentrations used in previous laboratory assays are consistent with levels found in an estuary.

KEYWORDS:

• Zooplankton
• fish
• kairomones
• diel vertical migration
• chemical ecology

Acknowledgments

We thank Dr. Daniel Rittschof, Dr. Mark Warner, Dr. Timothy Targett, and three anonymous reviewers for their thoughtful comments on the manuscript, as well as Adam Wickline, Heather Cronin, Haley Glos, Katie Pell, Elise Lankiewicz, Ann Williamson, Andrew Joesoef, Hayley De Marchis, and Nathan Tillotson for their help with animal collection. This work was supported in part by awards from the University of Delaware Research Foundation (award no. 12A00755) to J.H.C., Marian R. Okie, Joanne Currier Daiber and the Delaware Environmental Institute Fellowships to C.L.C., C.S.A was supported as an REU fellow through National Science Foundation Grant No. OCE-1003919, and P.I.D. was supported through the University of Delaware Summer Scholars Program.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

The supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Division of Ocean Sciences [OCE-1003919]; University of Delaware Summer Scholars Program; Marian R. Okie Fellowship; University of Delaware Research Foundation [12A00755]; Joanne Currier Daiber Fellowship; Delaware Environmental Institute.