Partial diel vertical migration in an omnivorous macroinvertebrate, Mysis diluviana

Abstract

Partial migration, whereby only a portion of a population migrates, has just recently received attention in aquatic systems. Partial diel vertical migration (DVM) has received even less attention but could significantly influence our understanding of trophic interactions and nutrient movement in open water systems. Recent work in the Baltic Sea shows differences in isotope composition between benthic and pelagic Mysis salemaai sampled at night, suggesting that partial DVM may be fixed at the individual level. Historic observations of North American M. diluviana suggest partial DVM in this species, but this behavior has largely been ignored in the literature. We used length, occurrence of gravid females, and body d 13 C, d 15 N, d 34 S, and C:N ratio as markers to test for differences among adult M. diluviana collected from benthic and pelagic habitats at night in Lake Champlain, USA. We found differences in body length and occurrence of gravid females between pelagic-and benthic-caught M. diluviana and differences in C:N between pelagic-and benthiccaught non-gravid individuals, consistent with life stage and body condition hypotheses for partial migration. Partial DVM of M. diluviana could have significant impacts on population assessments which could bias food web models used in basic research and management.

An underwater video system to assess abundance and behavior of epibenthic Mysis

“…A nonmigrating benthic portion of Mysis that remains on or near the bottom of deep lakes, and thus unavailable to pelagic gear at night when Mysis populations are sampled, could present complications for sampling programs and mass‐balance food web models, especially if the nonmigrants represent a large proportion of the population biomass or a disproportionate fraction of particular life‐stages (e.g., adult females; Euclide et al ; O'Malley et al ). Our results confirm the presence of Mysis in close contact with the sediment surface throughout the night each month from spring to autumn, confirming that Mysis partial DVM is common in Lake Champlain (Euclide et al ; O'Malley et al ). Our results also suggest that Mysis densities may be much higher on benthic habitats than previously estimated using benthic sleds.…”

“…Partial migration is a result of individual variability in migratory behavior, where not all individuals in a population migrate (Chapman et al ). Partial DVM has been the term used to describe invertebrates that demonstrate variability in their DVM behavior within a population (Frost and Bollens ; Euclide et al ). Consequently, population estimates of meroplanktonic species that exhibit partial DVM need to account for both migrant and nonmigrant individuals.…”

“…The system provides opportunities to continuously assess abundances and behavior and study diel differences in partial migratory populations. We applied our video system to Mysis diluviana (hereafter Mysis ) in Lake Champlain, where only a single mysid species exists and exhibits partial DVM (Euclide et al ; O'Malley et al ). The efficacy of measuring benthic Mysis with continuous video was evaluated by comparing density estimates generated from video data to those from concurrent benthic sled tows day and night, and point sampling with a smaller portable camera.…”

Benthic habitat is an integral part of freshwater Mysis ecology

“…To understand mysid migration, we need to consider external and internal conditions (Nathan et al, 2008) unclear. Several early studies proposed such alternative behaviours (Morgan, 1980;Rybock, 1978), and more recent studies using stable isotopes and genetics have found suggestive but mixed results (Euclide et al, 2017;Ogonowski et al, 2013). Another possibility is the presence of personality traits that influence, or at least reflect, differences in movement, including migration (Chapman et al, 2011;Mettke-Hofmann, Ebert, Schmidt, Steiger, & Stieb, 2005;Nilsson, Nilsson, Alerstam, & Backman, 2010;Sih & Watters, 2005 Sommer et al, 2012) and benthic resources, and observations from Lake Ontario (Johannsson et al, 2001).…”

“…Recent studies, however, indicate that Mysis exhibit partial DVM, whereby a portion of the population does not ascend but remains on bottom at night (Euclide, Hansson, & Stockwell, 2017;Ogonowski, Duberg, Hansson, & Gorokhova, 2013;O'Malley, Dillon, Paddock, Hansson, & Stockwell, 2018;.…”