Moon jellyfish, scientifically known as Aurelia aurita, are a common species of jellyfish. These invertebrates are easily identified by their translucent, bell-shaped bodies, which often feature four distinct horseshoe-shaped gonads visible through the bell. This article explores the natural habitats where these creatures live across their different life stages.
Global Presence
Moon jellyfish exhibit a broad global distribution, thriving in various ocean environments. They are found across the Atlantic, Pacific, and Indian Oceans, adapting to a wide range of marine conditions. Their presence extends from temperate to tropical waters, making them a common sight in many coastal regions.
These cnidarians can be encountered as far north as 70° latitude and as far south as 40° latitude. While abundant in oceanic expanses, they are less common in the coldest parts of the Arctic and Antarctic Oceans. Moon jellyfish frequently inhabit coastal areas, including bays, harbors, and estuaries.
Preferred Aquatic Environments
Moon jellyfish prefer coastal, shallow waters like shorelines, harbors, and estuaries. These environments offer abundant food sources, primarily zooplankton, which they capture with their short tentacles. The calmer conditions in these areas also provide protection from strong currents that could displace them.
Their widespread distribution is due to their tolerance for a range of environmental conditions. Moon jellyfish are euryhaline, meaning they can withstand varying salinity levels. While found in waters with salinity exceeding 23 parts per thousand (ppt), they have been observed in brackish environments with salinity as low as 3 ppt.
They are also eurythermal, surviving across a broad temperature spectrum, from approximately 6°C (43°F) to 31°C (88°F). Their optimal temperature range is between 9°C to 19°C (48-66°F). Moon jellyfish reside in the epipelagic zone, the sunlit upper layer of the ocean, where food is plentiful near the surface.
Life Stage Habitat Shifts
The habitat of moon jellyfish changes throughout their life cycle, which includes both sessile (attached) and free-swimming stages. The life cycle begins with planula larvae, which are free-swimming for a brief period before they settle. These larvae search for a suitable place to attach.
Once a larva finds a suitable spot, it transforms into a sessile polyp, a small, stalk-like structure attached to a hard substrate. These polyps anchor onto rocks, shells, and artificial structures like docks and shipwrecks in coastal waters. This attached stage allows them to remain in a stable location while they grow and reproduce asexually.
From these polyps, tiny, immature jellyfish called ephyrae are released into the water. These ephyrae develop into the free-swimming medusa stage, which inhabits the open water column. While medusae are mobile, they are not strong swimmers and largely drift with ocean currents, often remaining within the same coastal areas where their polyps reproduced.