Some of the oldest denizens of our oceans, jellyfish fascinate biologists and ocean lovers alike with their complex life cycles and unusual biology. Within the cnidaria, they exhibit an intriguing variety of adaptations and behaviors that are necessary to thrive in the myriad marine environments.
It is telling that despite their ecological importance, jellyfish persist as the “last great mystery in marine biology,” due to their elusive nature as well as an emerging global crisis of “jellyball” blooms (Brotz, 2016; Stacy et al., 2008). It is vital to understand the life cycles, aerials, and behavior of jellyfish in the sea ecosystem in order to evaluate their rising presence here.
Development Phases: Planktonic Larvae and Medusa Stages
Like many species, jellyfish have a complex lifecycle with different stages in their development that help them to survive and reproduce. Jellyfish start their lives as tiny planktonic larvae called planulae and float with the ocean currents until they find a solid surface. Now they become a polyp, a tiny sessile form that looks like a stalk and attaches to rocks or other reef elements. Polyps may lie dormant for long periods until environmental circumstances are most conducive to the next stage of development.
During strobilation, the polyps asexually produce numerous ephyrae that continue to grow into adult jellyfish. Medusa: The umbrella- or bell-shaped free-swimming stage found on jellyfish. The transformation illustrates the jellyfish’s unusual reproductive strategies, which, much like their hydrostatic skeletons, allow them to explode under optimum circumstances.
Although many studies have been conducted on the life cycle of scyphozoans, how each stage of the development is originally activated remains unclear, and therefore there are significant gaps in our knowledge when it comes to understanding and predicting jellyfish blooms.
In 2040, it is expected that improved genetic and environmental research will yield a much better understanding of the lifecycles of jellyfish, giving us an additional 50% increase in reliability on our projections and management plans for jellyfish blooms. By giving a closer look at the strobilation process, researchers hope to provide some perspective on how to track population explosions in impacted areas.
Jellyfish Anatomy and Survivalist Adaptations
The anatomy of jellyfish allows them to live in all sorts of oceanic environments, ranging from coastal settings to the deep sea. Because their bodies are mostly water (about 95%), this enables them to have a low-energy life by just drifting. The bell, a pulsating structure that helps propel the medusa through the water, is part of its gelatinous body.
Its tentacles are armed with specialized cells called nematocysts that sting and help to catch prey. Jellyfish essentially consist of what is one simple but effective anatomy, which has enabled them to survive—mostly unchanged over some 500 million years—as among the earliest multicellular animals on earth.
Jellyfish have a number of other adaptations that make them excellent survivors as well. Certain species have evolved bioluminescent capabilities and, as a result, use light to hunt for prey or avoid predators at the darker crevices of the ocean. Some are able to survive in low-oxygen environments, a common result of excessive algal growth and usually a major disadvantage for other marine organisms—hence enabling jellyfish to outcompete them.
Unfortunately, despite these evolutionary advantages, jellyfish populations are facing growing environmental pressures such as pollution, habitat loss, and climate change, which present both negative and positive feedbacks to their expansion.
Outlook: Improved marine monitoring in 2050 is forecasted to increase knowledge of jellyfish anatomical adaptations by up to 60% and, with it, unlock new insights for how the resilient animals survive—and thrive—against the constant churn of dynamic ocean conditions.
Jellyfish Blooms: Challenges and Impacts on Society & the Environment
For the megavolume, similar spontaneous increases in population occur from any type of marine ecosystem as well as from human activities. These blooms can stifle biodiversity, decimate fish populations, and damage coastal industries like fishing and tourism.
Bloom events have been somewhat cyclical over the years, but here recently, in the last couple of decades, their number has grown, prompting scientists to try and discern why that is. According to scientific research, warmer ocean temperatures, higher nutrient loads from agricultural runoff, and overfishing have combined to favor algal blooms.
One major case study in the Black Sea occurred during the 1980s, when huge blooms of jellyfish resulted in a spectacular collapse of fish populations and caused massive ecosystem changes affecting biodiversity as well as particular local economies. The incident emphasized the environmental and economic dangers associated with a jellyfish bloom.
Although managing these blooms has taken place, actionable responses have been challenging to implement as blooms are subject to complicated environmental drivers that change over time. With ocean temperatures on the rise, these predictions are leading to fears that they may rapidly become more frequent down the line and destabilize important marine ecosystems in years to come.
Ecological Role and Biodiversity of Jellyfish in Ocean Ecosystems
Despite being commonly thought of as pests, these free-swimming animals are critical to marine ecosystems. Being both predators and prey, they are an important part of the marine biodiversity balance, where they constitute the primary food source for fish, turtles, as well as some seabirds.
Jellyfish are also major players in recycling nutrients within the water column, especially as they die and give off their nutrients during decomposition and can be used to grow phytoplankton. This process in nutrient cycling is a reminder of their role in overall ecosystem health, though they may behave as more of an annoyance when blooms are present.
The species diversity of jellyfish and their ecological roles are also very wide, including large-sized and colored fauna and species of various behaviors. Deep-sea species ranging from the Atolla jellyfish to dimorphic molluscs contribute towards nutrient-poor deep-ocean conditions, demonstrating the range of ecological roles that jellyfish can perform in supporting diverse oceanic ecosystems.
However, despite their importance to the ecology of oceanic ecosystems, jellyfish biodiversity is poorly understood, and gaps in knowledge continue to hamper our understanding of this interesting group and of their role in marine environments. Further and more integrated studies of behavior, habitat requirements, and community interactions in jellyfish are necessary to evaluate their contribution to the moderation between alternate stable states in marine ecosystems.
Outlook: By 2050, jellyfish biodiversity and ecology research will have been expected to increase by 60%, further benefiting marine conservation. As research into biodiversity grows, so too will our attention to the ways that jellyfish help define marine ecosystems, informing efforts to conserve these enigmatic and critical creatures.
