Marine Life & Conservation
Microplastics: No small problem for filter-feeding ocean giants

Sharks, rays and whales impacted by microplastic pollution and associated toxins
Plastic pollution has recently gained increasing attention for its effects on marine mammals, fish and birds. However, it is still not fully understood to what extent small pieces of plastic, known as microplastics, impact marine life and ecosystems. Microplastic pollution is a major threat to filter-feeding animals such as manta rays, whale sharks and baleen whales, according to a new study published in the journal Trends in Ecology & Evolution. These iconic animals are at risk of exposure to microplastic contamination and associated toxins.
The paper, authored by researchers from the Marine Megafauna Foundation, Murdoch University (Australia), University of Siena (Italy) and Hawaii Institute of Marine Biology, stresses the significant risks microplastics pose to megafauna since these need to swallow hundreds to thousands of cubic meters of water daily in effort to capture plankton. They can ingest microplastics directly from polluted water or indirectly through contaminated prey. Filtering of indigestible plastic particles can block nutrient absorption and cause damage to the digestive tract of animals. Additionally, plastic-associated chemicals and pollutants can accumulate over decades and alter biological processes, leading to altered growth, development and reproduction, including reduced fertility.
Lead author Elitza Germanov, researcher at the Marine Megafauna Foundation and PhD student at Murdoch University, said: “Despite the growing research on microplastics in the marine environment, there are only few studies that examine the effects on large filter feeders. We are still trying to understand the magnitude of the issue. It has become clear though that microplastic contamination has the potential to further reduce the population numbers of these species, many of which are long-lived and have few offspring throughout their lives.”
“It is vital to understand the effects of microplastic pollution on ocean giants since nearly half of the mobulid rays, two thirds of filter-feeding sharks and over one quarter of baleen whales are listed by the IUCN as globally threatened species and are prioritized for conservation”, she adds.
It is challenging to assess plastic concentrations through conventional methods usually used to study animal diets, such as stomach analysis or collection of egested material, as these rely on opportunistic observations and are unsuitable for threatened species. However, using non-lethal sampling of small amounts of tissue (biopsy), researchers are now able to test for chemical tracers.
Professor Maria Cristina Fossi from the University of Siena, one of the first scientists who studied this problem, and colleagues reported an average of 0.7 plastic items per cubic meter of water around the Baja California peninsula, an important feeding ground for endangered whale sharks. The researchers estimated that whale sharks may be ingesting 171 items on a daily basis. Meanwhile in the Mediterranean Sea, fin whales are thought to swallow microplastic particles in the thousands per day.
“Our studies on whale sharks in the Sea of Cortez and on fin whales in the Mediterranean Sea confirmed exposure to toxic chemicals, indicating that these filter feeders are taking up microplastics in their feeding grounds. Exposure to these plastic-associated toxins pose a major threat to the health of these animals since it can alter the hormones, which regulate the body’s growth and development, metabolism, and reproductive functions, among other things”, says Professor Fossi who co-authored this paper.
Filter feeders are considered to be at high risk of exposure since many inhabit some of the most polluted waters, namely in the Coral Triangle region, Bay of Bengal, Gulf of Mexico and Mediterranean Sea. “As plastic production is projected to increase globally, future research should focus on coastal regions where microplastic pollution overlaps with the critical feeding and breeding grounds of these threatened animals. Many areas are biodiversity hotspots and of economic importance due to fisheries and marine tourism. Targeting these with the backing of local government and industry will help ensure efforts to mitigate the plastic threat are employed to their fullest,” Germanov concludes.
Elitza Germanov, Andrea Marshall, Lars Bejder, Maria Cristina Fossi and Neil R Loneragan ‘Microplastics: No small problem for filter feeding megafauna’ was published on 5 February 2018 and is available here.
The Marine Megafauna Foundation was created in 2009 to research, protect and conserve the populations of threatened marine megafauna around the world. ‘Megafauna’ are large marine species such as sharks, rays, marine mammals and sea turtles.
Find out more about Marine Megafauna Foundation here.
Blogs
Evolution of Manatees in Florida

Op-ed by Beth Brady, PhD, Senior Science and Conservation Associate, Save the Manatee® Club
Recent news articles and broadcasts have claimed that manatees are not native to Florida or only arrived on Florida’s west coast in the 1950s. These claims, based on limited anthropological records, point to where manatees were historically exploited by humans and assume that a lack of evidence means manatees were absent from certain areas. However, absence of evidence is not evidence of absence—it’s like looking for stars in the daytime; just because you can’t see them doesn’t mean they’re not there. Moreover, genetic and fossil evidence indicate manatees have been present in Florida for the last 12,000 years.
The Florida Fish and Wildlife Conservation Commission (FWC), which manages Florida manatee populations, has created a manatee timeline highlighting key dates and notable information about manatee presence in Florida (https://myfwc.com/education/wildlife/manatee/timeline/). Historical records suggest that manatees have been observed in Florida as far back as the 1500s, with some details presented by the Florida Fish and Wildlife timeline aligning with evidence presented in the publication.
Manatee species, such as the African manatee and the Antillean manatee, continue to be poached by humans (Marsh et al., 2022). As a result, these species are difficult to observe in the wild and may adapt by foraging at night to avoid human encounters (Rycyk et al., 2021). This behavior could help explain why historical Florida manatee populations that were hunted by humans are absent from middens and rarely mentioned in historical accounts.
Further, the publication only briefly touches on the paleontological record and genetic evidence, which indicate that manatees have existed in Florida for a much longer period. Fossil and genetic evidence reveal a rich history of manatees in Florida. Manatees belong to the order Sirenia, which includes the Amazonian, African, and West Indian manatee species. While Sirenian fossils have been found globally, only Florida and the Caribbean contain specimens from every epoch over the past 50 million years (Reep and Bonde, 2006). The modern manatee, as we know it, emerged in the Caribbean about 2 million years ago (Domning, 1982).
The evolution of manatees during the Pleistocene epoch provides valuable insights into how environmental changes shaped their distribution and genetic diversity. During the Pleistocene epoch (2.59 million to 11,700 years ago), there were roughly 20 cycles of long glacial periods (40,000–100,000 years) followed by shorter interglacial periods lasting around 20,000 years. At the start of these warmer periods, Caribbean manatees migrated northward with the warming waters (Reep and Bonde, 2006). Water currents and thermal barriers isolated these manatees from populations in Mexico and the Caribbean, leading to genetic divergence. Fossil evidence indicates that Trichechus manatus bakerorum lived in Florida and North Carolina about 125,000 years ago but did not survive the last glacial period, which began 100,000 to 85,000 years ago (Domning, 2005). This subspecies was eventually replaced by modern Florida manatees.
This evolutionary theory is further supported by genetic evidence. Research indicates that Florida manatees trace their evolutionary origins to Caribbean ancestors that migrated northward over the past 12,000 years (Garcia-Rodriguez et al., 1998). A 2012 study by Tucker et al. reinforces this theory, showing higher genetic diversity in manatees on Florida’s west coast compared to those on the east. Over time, core populations migrated northward, with some groups moving south and east along the Florida coastline before heading north along the Atlantic. This migration pattern left the west coast population with greater genetic diversity, while the east coast population retained only a smaller subset. These findings suggest that the founding population of Florida manatees—arriving approximately 12,000 years ago—originated along Florida’s southwestern coast, which became the center of the state’s manatee population (Reep and Bonde, 2006). The process of vicariance further supports this hypothesis; as geographic and ecological barriers emerged, they likely isolated the Florida manatee populations from their Caribbean ancestors. This isolation likely limited migration back and forth between regions, fostering the establishment of local populations in southwestern Florida.
Manatees are not only a cherished symbol of Florida’s natural heritage but also a species with deep evolutionary and historical ties to the region. In sum, despite recent claims questioning their nativity, extensive fossil and genetic evidence confirms that manatees have been present in Florida’s waters for thousands of years, with ancestors dating back over 12,000 years. We agree with the authors of the published article that protecting these iconic creatures and their habitats is essential to preserving Florida’s unique ecological identity for future generations
Beth Brady is the Senior Science and Conservation Associate at Save the Manatee Club whose work focuses on manatee biology and conservation. She has her PhD from Florida Atlantic University and her Master’s in Marine Science from Nova Southeastern University.
Marine Life & Conservation
Paul Watson Released as Denmark Blocks Japan’s Extradition Bid

Renowned anti-whaling activist Paul Watson has been released from custody in Greenland after spending five months in detention. Denmark’s Justice Ministry rejected Japan’s request for his extradition, citing insufficient guarantees that his time already served in custody would be credited against any potential sentence.
The 74-year-old Canadian-American was arrested on July 21 in Nuuk, Greenland’s capital, when his ship docked to refuel. His arrest was based on a 2012 Japanese warrant related to a 2010 encounter in Antarctic waters. Japan alleged Watson obstructed operations and caused damage to a whaling research ship during efforts to disrupt illegal whaling. Watson has consistently denied these claims, maintaining his commitment to marine conservation.
Denmark, which oversees extradition matters for Greenland, concluded that while the legal conditions for extradition were met, the lack of assurances from Japan regarding time-served credit made extradition untenable.
In a video shared by his foundation, Watson expressed gratitude and relief, saying, “After five months, it’s good to be out… and good to know they’re not sending me to Japan.” He added that the most difficult part of his time in custody was being separated from his two young sons.
Watson is a pioneering figure in marine conservation, known for founding the Captain Paul Watson Foundation in 2022 after decades of activism with the Sea Shepherd Conservation Society. His bold efforts to defend marine life have earned him widespread support, including from celebrities and conservationists. His work has also been featured in the acclaimed reality TV series Whale Wars.
Watson’s lawyer, Jonas Christoffersen, praised the decision, stating, “We are happy and relieved that Paul Watson is now free.” He added that Watson is eager to reunite with his family and continue his vital work.
The arrest occurred while Watson’s vessel, the M/Y John Paul DeJoria, was en route to the North Pacific with a team of 26 volunteers to intercept a Japanese whaling ship. His foundation described the arrest as politically motivated and emphasized that Watson’s actions were focused on ending illegal whaling practices.
Japan resumed commercial whaling in 2019 after leaving the International Whaling Commission, asserting that whale meat is a cultural tradition. Conservationists, however, continue to challenge these practices, highlighting their impact on marine ecosystems.
Despite the challenges, Watson remains steadfast in his mission to protect marine life and bring attention to whaling practices. His dedication to ocean conservation has made him a globally respected advocate for the environment.
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