Ocean Microscopic Diversity Sheds Light on Climate Change's Impact on the Oceans
Wed, April 21, 2021

Ocean Microscopic Diversity Sheds Light on Climate Change's Impact on the Oceans

The ocean has always been a huge, for the most part still unexplored world full of mysterious species / Photo by: Max Pixel

 

The ocean has always been a huge, for the most part still unexplored world full of mysterious species. This despite thousands of studies that have been conducted and discovered new species, learned how they live underwater, and their impacts on the world’s biodiversity. Comparatively, we have only a few studies that focused on marine microbes, the tiny organisms that live in water environments and can only be seen under a microscope.

Marine microbes are invisible to the naked eye, and these include bacteria, viruses, archaea, protists, and fungi. Previous studies showed that 90 percent of the weight of all living organisms in the ocean comes from microbes. However, just because they aren’t easily seen doesn’t mean they are less significant. These microorganisms are often the engines of ecosystems that otherwise would not have access to the food and nutrients they need. They also clean the oceans and defend ecosystems against harmful viruses.

Microbes are essential for a thriving ocean ecosystem. Without them, the world we know would not exist. Experts reported that the microbial world accounted for almost 50 to 90 percent of Earth’s history, with life itself likely beginning in the ocean. Not only do they account for the majority of ocean biomass and constitute a hidden majority of life that flourishes in the sea, but microbes are also the major primary producers in the ocean.

These marine microorganisms dictate much of the flow of marine energy and nutrients, influence our climate, and provide us with a source of medicines and natural products. They exist everywhere, helping to shape the features of our planet, past and present. For instance, bacteria and unicellular algae play a particularly important role in the general economy of our planet. Not only do they form the basis of the food chains, but they also recycle almost all the organic matter of the planet.

The Role of Rhodopsins in Regulating Climate

It has been established that almost all sunlight in the ocean is captured by chlorophyll in algae. But a recent study conducted by researchers from the University of Southern California discovered that rhodopsins, a sunshine-grabbing pigment, are the ones responsible for trapping the sunlight. This kind of marine microbes was discovered by scientists at USC about 20 years ago. They found out that rhodopsins have light-sensitive protein systems in their cell membranes that trap sunlight. 

Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, reported that the researchers explored the eastern Atlantic Ocean and the Mediterranean Sea in 2014. They collected sampled microorganisms in the water column down to 200 meters, hoping to determine how widespread rhodopsins are and in what conditions they are favored. The team found out that rhodopsins are more abundant than once thought. They outperform algae at capturing light in oligotrophic zones. 

The study published in Science Advances discovered that unlike algae that use sunlight and CO2 to produce organic material and oxygen, these microbes use light to make adenosine triphosphate, the basic energy currency that drives many cellular processes. Laura Gómez-Consarnau, assistant professor (research) of biology at the USC Dana and David Dornsife College of Letters, Arts, and Sciences, stated that the ocean will be more nutrient-poor due to the abundance of rhodopsins and the increasing global temperature. 

"So, with fewer nutrients near the surface, algae will have limited photosynthesis, and the rhodopsin process will be more abundant. We may have a shift in the future, which means the ocean won't be able to absorb as much carbon as it does today. So more CO2 gas may remain in the atmosphere, and the planet may warm faster,” Gómez-Consarnau said.

It has been established that almost all sunlight in the ocean is captured by chlorophyll in algae. But a recent study conducted by researchers from the University of Southern California discovered that rhodopsins, a sunshine-grabbing pigment, are the ones responsible for trapping the sunlight / Photo by: Max Pixel

 

Phytoplankton and Global Warming

A recent study by researchers from the Tara Oceans expedition, an international, interdisciplinary enterprise that collected 35,000 samples from all the world's oceans between 2009 and 2013, emphasized plankton as a major contributor to marine ecosystems in terms of biomass, abundance, and diversity. Unfortunately, planktonic species are being distributed unevenly across the ocean due to global warming. 

Lucie Zinger, the co-senior author of the Institut de Biologie de l'Ecole Normale Superieure (IBENS) in Paris, stated that higher oceanic temperatures are likely to cause a "tropicalization" of the temperate and polar oceanic regions. It is expected that there will be an increased diversity of planktonic species with higher water temperatures. This could alter the associated ecosystems and have serious consequences worldwide.

"This analysis allowed us to study not only what ocean microbes are capable of doing, but also what they actually do at a global scale,” author Shinichi Sunagawa at the ETH Zürich, Switzerland said. 

Marine microbes provide a helpful insight not only to prove how these microorganisms shape our ecosystems but also show the impacts of climate change on them / Photo by: Ivan Pellacani via Wikimedia Commons.

 

Phytoplankton, microscopic marine algae that provide food for a wide range of sea creatures, are also affected by global warming. A lot of people are unaware that they supply half the oxygen we breathe and they are a cornerstone of the ocean food web. According to The Conversation, an online site that offers informed commentary and debate on the issues affecting our world, phytoplankton use carbon dioxide to manufacture their own food.

However, global warming causes the ocean surface to become less dense. Phytoplankton in the warm top layer would starve without replenishment of the nutrient fertilizer from below. This leads to reduced primary production and a corresponding decrease in carbon pumping to the deep sea.

Marine microbes provide a helpful insight not only to prove how these microorganisms shape our ecosystems but also show the impacts of climate change on them. These studies provide an opportunity for researchers to learn more about ocean microscopic diversity and determine how they help in mitigating the impacts of climate change.