Sea butterflies (Thecosomata) belong to the suborder of marine snails, known as shelled pteropods. These creatures are characterised by their muscular feet that enable them to swim in water instead of gliding on solid surfaces. As holoplanktonic organisms, they spend their entire lifecycle in the water column.
Found across all oceans, sea butterflies are particularly diverse and populous in colder waters. They bear bilateral symmetry and a coiled or uncoiled shell which varies in shapes and sizes. Remarkably transparent yet fragile, these shells are highly susceptible to being dissolved by ocean acidification.
Each sea butterfly is equipped with a pair of wing-like lobes or parapodia for propulsion and a head with eyes, tentacles, and a mouth with a long proboscis, aiding in capturing prey. Given their reduced or absent gill, they rely on their body surface for gas exchange.
The Importance of Sea Butterflies
Sea butterflies serve as a significant food source for numerous fish, seabirds, whales, and other marine animals. Beyond this, they play a critical role in transporting carbon from the ocean’s surface to its depths via their shells and fecal pellets.
Climate Change and Its Impact on Sea Butterflies
Ocean acidification due to increased carbon dioxide absorption leads to heightened acidity and a reduced availability of carbonate ions needed for shell formation and maintenance. Winters pose a particular risk for these creatures as the cooler water absorbs more CO2, leading to the possibility of their shells dissolving, weakening, or deforming. This increases their vulnerability to predators, infections, and stress and affects their metabolism, growth, reproduction, and survival.
Rising ocean temperatures influence the distribution and abundance of sea butterflies, as they seek optimal thermal conditions for development and survival. It also alters food availability and quality, impacting ocean currents and mixing which affect the sea butterfly transport.
Additionally, the warmer and stratified ocean leads to decreased oxygen levels, affecting sea butterflies’ respiration and energy balance, their vertical migration patterns, and it exacerbates the effects of ocean acidification by increasing dissolved carbon dioxide concentrations.
Reduced Sea Butterfly Population and Its Impact on Antarctica’s Marine Ecosystems
As sea butterflies represent a major food source for various marine animals, their decline can lead to starvation, malnutrition, and reduced reproduction in predators and prey alike. This disruption has ramifications for the marine food web, as these creatures play a crucial role in connecting primary producers (phytoplankton) with secondary consumers (zooplankton) and higher trophic levels.
A decrease in the sea butterfly population could alter the structure and function of the marine food web, thereby potentially affecting the biodiversity and productivity of the Antarctic marine ecosystem.
Furthermore, sea butterflies contribute to the “biological pump,” transporting carbon from the surface to the deep ocean through their shells and fecal pellets. As their population declines, less carbon is sequestered in the ocean. This not only results in increased atmospheric carbon dioxide levels but also further ocean acidification.
The role of sea butterflies in preventing the acidification of oceans, maintaining the balance of the marine food chain, and supporting the ecosystem’s overall health are undeniable. Their struggle for survival in changing climate conditions alerts us to the pressing need to mitigate the impacts of global warming and maintain the delicate balance of aquatic ecosystems.
For those facing civil service examinations, understanding the consequences of phenomena such as ocean acidification and global warming, particularly on marine life, may prove essential. For example, in 2012 and 2019, questions relating to the effects of increasing ocean acidification and global warming on coral life system respectively were included in the test.
