How tiny algae shaped the evolution of giant clams
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Giant clams live in a symbiotic relationship with algae.
view moreCredit: Ruiqi Li/CU Boulder
Giant clams, some of the largest mollusks on Earth, have long fascinated scientists. These impressive creatures can grow up to 4.5 feet in length and weigh over 700 pounds, making them icons of tropical coral reefs.
But these animals don’t bulk up on a high-protein diet. Instead, they rely largely on energy produced by algae living inside them. In a new study led by CU Boulder, scientists sequenced the genome of the most widespread species of giant clam, Tridacna maxima, to reveal how these creatures adapted their genome to coexist with algae.
The findings, published Jan. 4 in the journal Communications Biology, offer clues about how such evolution may have contributed to the giant clam’s size.
“Giant clams are keystone species in many marine habitats,” said Jingchun Li, the paper’s senior author and professor in the Department of Ecology and Evolutionary Biology. “Understanding their genetics and ecology helps us better understand the coral reef ecosystem.”
A symbiotic relationship
Unlike popular myths—like the one in Disney’s “Moana 2” where the giant clam eats humans—these vegetarian mollusks rely on algae living within their bodies for energy. If giant clams ingest the right algae species while swimming through the ocean as larvae, they develop a system of tube-like structures coated with these algae inside their body. These algae can turn sunlight into sugar through photosynthesis, providing nutrients for the clams.
“It’s like the algae are seeds, and a tree grows out of the clam’s stomach,” Li said.
At the same time, the clams shield the algae from the sun’s radiation and give them other essential nutrients. This mutually beneficial relationship is known as photosymbiosis.
“It’s interesting that many of giant clams’ cousin species don’t rely on symbiosis, so we want to know why giant clams are special,” said Li.
In collaboration with researchers at the University of Guam and the Western Australian Museum, the team compared the genes of T. maxima with closely related species — such as the common cockle—that lack symbiotic partners. The researchers found that T. maxima have evolved more genes coded for sensors to distinguish friendly algae from harmful bacteria and viruses. At the same time, T. maxima tuned down some of its immune genes in a way that likely helps the animal tolerate algae living in their body long term, according to Ruiqi Li, the paper’s first author and postdoctoral researcher at the CU Museum of Natural History.
As a result of the clam’s weakened immune system, its genome contains a large number of transposable elements, which are bits of genetic material left behind by ancient viruses.
“These aspects highlight the tradeoffs of symbiosis. The host has to accommodate a suppressed immune system and potentially more viral genome invasions,” said Ruiqi Li.
The study also discovered that giant clams have fewer genes related to body weight control, known as the CTRP genes. Having fewer CTRP genes might have allowed giant clams to grow larger.
Conservation concerns
Last year, a giant clam population assessment by Ruiqi Li, prompted the International Union for Conservation of Nature (IUCN) to update the conservation status of multiple giant clam species. Tridacna gigas, the largest and most well-known species, is now recognized as “critically endangered,” the highest level before a species becomes extinct in the wild.
T. maxima, because of its wide distribution, is currently classified as “least concern.” But Ruiqi Li said it’s possible that different species are lumped into one category simply because they look similar.
“If you think these giant clams are all the same species, you might underestimate the threat they face,” Ruiqi Li said. “Genetic studies like this can help us distinguish between species and assess their true conservation needs.”
The team hopes to sequence the genomes of all 12 known species of giant clams to better understand their diversity.
Similar to corals, giant clams are facing increasing threats from climate change. When the ocean water becomes too warm, the clams expel the symbiotic algae from their tissues. Without the algae, the giant clams can starve.
“The giant clams are very important for the stability of the marine ecosystem and support biodiversity,” Jingchun Li said. She added that many creatures living in the shallow waters rely on their shells for shelter, and giant clams also provide food for other organisms.
“Protecting them is essential for the health of coral reefs and the marine life that depends on them.”
Journal
Communications Biology
DOI
FAU Engineering researchers develop new weapon against harmful algal blooms
Breakthrough in water treatment: Algae-based adsorbents could combat phosphorous pollution
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Harmful algal blooms occur when colonies of algae — simple plants that live in the sea and freshwater — grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds.
view moreCredit: FAU Harbor Branch Oceanographic Institute
As harmful algal blooms (HABs) continue to spread across the globe, urgent research is needed to address this growing threat. Studies in Italy, China, and the Atlantic basin have shown that many water bodies have high nitrogen-to-phosphorus ratios, making phosphorus a key factor that drives these blooms. This highlights the critical need for more effective phosphorus management strategies to curb the rise of HABs and protect our ecosystems.
Recently, there’s been a growing interest in finding useful ways to repurpose troublesome algal biomass, which could be turned into valuable products like bioplastics, biofertilizers, and biofuels. Researchers have already explored using algal biomass to create materials that can help clean up things such as heavy metals, rare earth metals, dyes, and even capture CO2 and harmful volatile organic compounds from the air.
However, few studies have looked into how algal biomass, especially cyanobacteria, also known as blue-green algae, can be used to create materials that remove phosphate from water.
Now, researchers from the College of Engineering and Computer Science at Florida Atlantic University, have filled that gap by transforming cyanobacterial biomass, which is typically a hazardous waste, into custom-made adsorbent materials that can pull harmful phosphorus out of water. Adsorbent materials are substances that can attract and hold molecules or particles such as gases, liquids, or dissolved solids on their surface. Unlike absorbent materials that soak up substances into their structure, adsorbents capture molecules on the outside surface, forming a thin layer.
To convert algal biomass into chemically modified activated carbon adsorbent materials for phosphate removal, researchers collected cyanobacterial biomass from Florida’s Lake Okeechobee and processed before activation using fast and energy-efficient microwave heating. To improve phosphate removal from water, researchers tested adsorbent materials modified with lanthanum chloride or zinc chloride. Relatively abundant, lanthanum is a metal that is part of the rare-earth element group. Both compounds are useful in a variety of fields including environmental cleanup, industrial processing, and chemical manufacturing. Previous research did not identify any human health risks associated with the use of lanthanum for phosphorus removal.
Results of the study, published in the journal Algal Research, show that materials treated with lanthanum chloride removed more than 99% of phosphorus, even at starting phosphorus concentrations as high as 20 milligrams per liter of water. The best material could be synthesized in three minutes and successfully achieved 90% phosphorus removal efficiency with a low amount of material (0.2 gram per liter of contaminated water) and just 30 minutes of contact time. This material also performed well in the presence of natural organic matter by selectively removing phosphorus.
The study suggests that lanthanum-modified algae-based adsorbents could help reduce HABs by removing phosphorus from water. The effectiveness comes from the formation of a compound, LaPO4.H2O (also known as rhabdophane), which traps phosphorus permanently.
“Our findings suggest that lanthanum-modified algae-based materials could be an effective solution for removing phosphorus and preventing harmful algal blooms if used on a larger scale,” said Masoud Jahandar Lashaki, Ph.D., senior author, assistant professor and graduate program director/coordinator in FAU’s Department of Civil, Environmental and Geomatics Engineering. “By using readily available waste materials like algal biomass, combined with lanthanum, an element known for its strong phosphorus-binding capabilities, we have developed an adsorbent that can effectively target and remove excess phosphorus from water. Phosphorus is a major contributor to the occurrence of harmful algal blooms, which can lead to toxic water conditions, loss of aquatic life, and significant economic impacts on industries like fishing and tourism.”
Results of this study show the promise of this innovative approach in addressing one of the most pressing challenges in water quality management. With further refinement and scalability, this technique could become an essential tool for managing nutrient pollution and preserving aquatic ecosystems globally.
“Our team’s research highlights the high efficiency of these materials in removing phosphorus over a wide range of concentrations. This approach could provide an environmentally friendly and cost-effective solution to mitigate the effects of eutrophication – the process where excessive nutrients, particularly phosphorus, fuel the growth of harmful algae in lakes, rivers, and coastal areas,” said Stella Batalama, Ph.D., dean, FAU College of Engineering and Computer Science. “By applying lanthanum-modified algae-based materials in regions prone to harmful algal blooms, communities could significantly reduce the occurrence of these blooms, improving water quality, protecting ecosystems, and ensuring safe water for both human use and wildlife.”
Study co-authors are Vithulan Suthakaran, a civil engineer and doctoral candidate in FAU’s College of Engineering and Computer Science; Ryan Thomas, an environmental engineer and FAU graduate; Mitchell Guirard, an environmental engineer and FAU graduate; and Daniel Meeroff, Ph.D., professor and dean of undergraduate studies, FAU Department of Civil, Environmental and Geomatics Engineering.
This research and publication were developed under Project INV12 and funded by the Florida Department of Environmental Protection (FDEP) under the direction of the Blue-Green Algae Task Force. The research team recently received a Phase-II grant ($590,527; INV45) from the FDEP to investigate the scalability of the proposed solution.
- FAU -
About FAU’s College of Engineering and Computer Science:
The FAU College of Engineering and Computer Science is internationally recognized for cutting-edge research and education in the areas of computer science and artificial intelligence (AI), computer engineering, electrical engineering, biomedical engineering, civil, environmental and geomatics engineering, mechanical engineering, and ocean engineering. Research conducted by the faculty and their teams expose students to technology innovations that push the current state-of-the art of the disciplines. The College research efforts are supported by the National Science Foundation (NSF), the National Institutes of Health (NIH), the Department of Defense (DOD), the Department of Transportation (DOT), the Department of Education (DOEd), the State of Florida, and industry. The FAU College of Engineering and Computer Science offers degrees with a modern twist that bear specializations in areas of national priority such as AI, cybersecurity, internet-of-things, transportation and supply chain management, and data science. New degree programs include Master of Science in AI (first in Florida), Master of Science and Bachelor in Data Science and Analytics, and the new Professional Master of Science and Ph.D. in computer science for working professionals. For more information about the College, please visit eng.fau.edu.
About Florida Atlantic University:
Florida Atlantic University, established in 1961, officially opened its doors in 1964 as the fifth public university in Florida. Today, the University serves more than 30,000 undergraduate and graduate students across six campuses located along the southeast Florida coast. In recent years, the University has doubled its research expenditures and outpaced its peers in student achievement rates. Through the coexistence of access and excellence, FAU embodies an innovative model where traditional achievement gaps vanish. FAU is designated a Hispanic-serving institution, ranked as a top public university by U.S. News & World Report and a High Research Activity institution by the Carnegie Foundation for the Advancement of Teaching. For more information, visit www.fau.edu.
A schematic of the treatment process to convert algal biomass into chemically modified activated carbon adsorbent materials for phosphate removal.
Credit
FAU College of Engineering and Computer Science
Journal
Algal Research
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Developing activated carbon adsorbent materials using cyanobacterial biomass as precursor to remove phosphate from surface waters
Article Publication Date
28-Jan-2025
