Time and Tide
While life on land is determined by the sun, in the realm of the oceans, the moon is the undisputed ruler of the rhythms of life. On a large scale as well as at a small one, the moon acts as a pacemaker. Its gravitational forces are the main cause of the rise and fall of the tides, together with the gravitation of the sun and the rotation of the Earth. Many organisms of the intertidal zones have adapted their biorhythms to the tidal cycles and the challenges of an environment that seems to change between sea and dry land. But creatures of the open waters are also ruled by the moon; their reproduction cycles, like the mass-spawning of the bristle worm Platynereis dumerilii, are synchronized with the moon. A light receptor protein called L-Cryptochrome enables them to distinguish between sun and moonlight, and even to recognize each of the moon phases. But the effects of marine lunar cycles might extend far beyond that and affect terrestrial life as well, as methane deposits below the Arctic oceans were found to be influenced by the tides. Methane is a gas that plays a crucial role in climate change. Researchers from the University of Tromsø, Norway, found that the release of methane into the atmosphere is reduced during high tides due to rising pressure. This might be a good sign—it suggests, as least, that the rising sea-levels in the warming oceans could help contain the greenhouse gas.
Sources: Naylor, E., Chronobiology of Marine Organisms, Cambridge, 2010.
Poehn, Birgit et al., “A Cryptochrome adopts distinct moon- and sunlight states and functions as sun- versus moonlight interpreter in monthly oscillator entrainment”, Nature Communications, vol. 13, issue. 5220, (2022).
Sultan, N. et al., “Impact of tides and sea-level on deep-sea Arctic methane emissions”, Nature Communications, vol. 11, issue. 5087, (2020).