Lunar periodicity in the shell flux of planktonic foraminifera in the Gulf of Mexico

[摘要] Synchronised reproduction offers clear benefits to planktonic foraminifera –an important group of marine calcifiers – as it increases the chances ofsuccessful gamete fusion. Such synchrony requires tuning to an internal orexternal clock. Evidence exists for lunar reproductive cycles in somespecies, but its recognition in shell flux time series has proven difficult,raising questions about reproductive strategies. Using spectral analysis ofa 4-year time series (mostly at weekly resolution) from the northern Gulf ofMexico, we show that the shell flux of Globorotalia menardii, Globigerinellasiphonifera, Orbulina universa, Globigerinoides sacculifer, Globigerinoidesruber (both pink and whitevarieties),Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, Globigerinellacalida and Globigerinita glutinata is characterised by lunar periodicity. However, thelunar rhythm is not present in all size fractions of each species and tendsto be more dominant in the flux of larger shells, consistent withreproduction being more prevalent in larger specimens. Lunar periodicity issuperimposed on longer term/seasonal changes in the shell fluxes, butaccounts for a significant part of the variance in the fluxes. The amplitudeof the lunar cycle increases roughly proportional with the magnitude of theflux, demonstrating that most of the population is indeed affected bylunar-phased synchronisation. In most species peak fluxes occurpredominantly around, or just after, full moon. Only G. siphonifera and G. calida show a contrastingpattern with peaks concentrated around new moon. Although the exact cause ofthe synchronisation remains elusive, our data considerably increase thenumber of species for which lunar synchronised reproduction is reported andsuggest that such reproductive behaviour is common in many species ofplanktonic foraminifera.

[学科分类] 地球化学与岩石