Warming of subtropical coastal waters accelerates Mnemiopsis leidyi growth and alters timing of spring ctenophore blooms

Abstract

Shifts in the size, frequency, or timing of gelatinous zooplankton blooms in response to climate variability and climate change have become a concern in many coastal marine ecosystems worldwide. When abundant, gelatinous zooplankton can induce trophic cascades as well as alter energy flows to upper-level consumers. To quantify the role water temperature plays in regulating bloom development of the ctenophore Mnemiopsis leidyi in subtropical coastal waters, we experimentally determined the effects of increases in temperature and rates of warming on growth rate (mg C d-1). Conditions were representative of those occurring during late winter and early spring (January to April) in the northern Gulf of Mexico. M. leidyi growth rates increased exponentially with temperature (9, 13, 16, and 22°C) and rates of warming (+1, +2, and +3°C wk-1). A biologically important temperature threshold (15.0°C, delineating negative and positive growth) as a proxy measure for bloom initiation was applied to a time-series of sea surface temperature (1975 to 2013) from Mobile Bay (Alabama, USA) and indicated climate-related warming of northern Gulf of Mexico has likely advanced the timing of the spring M. leidyi bloom over the past 39 yr. Results have implications for ecosystem-based approaches to fisheries management since larger ctenophore blooms, occurring earlier in the year, would be expected to intensify potential competitive and predatory interactions between M. leidyi, zooplankton, and planktivorous juvenile fish utilizing nearshore waters as nursery habitat during the late winter and early spring. © Inter-Research 2014.