Effects of ultraviolet radiation on the growth, reproduction and survival of the lobate ctenophore Mnemiopsis leidyi in Chesapeake Bay

Solar ultraviolet radiation (UVR) is an environmental stressor that can have a variety of negative effects on aquatic organisms including slowed growth, changes in reproduction and increased mortality. The ctenophore Mnemiopsis leidyi is a highly transparent organism that has not been shown to actively avoid ultraviolet radiation or possess photoprotective compounds and may therefore be vulnerable to deleterious effects of UVR. Results of this study indicate that summertime UVR exposure equivalent to average UVR conditions within the top 0.5 m of the water column of the Rhode River, Maryland, USA, can cause mortality and reduced size of M. leidyi. Exposures tested did not, however, affect egg production beyond that attributable to UVR effects on mortality. Experiments indicated a sharp threshold for the tolerance of M. leidyi to biologically effective UVR exposure. A biological weighting function (BWF) was experimentally determined to describe the spectral dependence of UV induced mortality. The BWF was similar to those previously reported for mesozooplankton. M. leidyi is an important component of many ecosystems; thus, changes in its population size and abundance have the potential to significantly affect coastal and estuarine food webs, and oyster, fish and sea nettle populations, in systems like Chesapeake Bay. Future scenarios of decreased eutrophication and runoff that result in reduced dissolved organic matter and particulates, will likely lead to increased amounts and penetration of UVR in coastal and estuarine systems and could increase deleterious effects of UVR on M. leidyi.

► Examined effects of UVR on ctenophore growth, reproduction and survival.
► Near-surface levels of UVR in Chesapeake Bay negatively affects ctenophore size.
► Mnemiopsis leidyi has a sharp tolerance threshold to UVR.
► Determined a biological weighting function to describe spectral sensitivity.