How clams help determine at-risk ecosystems

Findings from a new study published in the journal Environmental Pollution show that clams can act as a litmus test for ecological risks of plastic pollution.

Researchers in China discovered microplastics in Asian clams in the Yangtze River to be representative of microplastic pollution in the river’s ecosystems.

“The levels of microplastics in the Asian clam can serve to track the amount of microplastics that may be available to marine animals of a similar size,” say the authors. “From an ecological perspective, Asian clams can provide a snapshot of what can be ingested across a large area.”

Microplastics are tiny plastic particles that are smaller than 5mm—or about the width of a pencil.

These small particles were detected at high levels in 96% of Asian clams sampled. At these levels, researchers say, habitat contamination and transfer to other organisms is likely.

Clams were chosen as “indicators” of microplastic pollution because they are filter feeders—essentially acting as a strainer trapping food and other small particles in water.

Along with clams, sediment and water were collected for microplastic analysis at 21 sites along the Yangtze river. Within those study areas, three different ecosystems were selected: lakes, rivers, and estuaries—transition zones where saltwater meets freshwater.

To isolate microplastics, the researchers used a series of elaborate filters, nets, and vacuums.

Levels of microplastics varied greatly across the three ecosystems. Rivers contained higher levels, which could be attributed to lower water volume, or even proximity to industrial plants.

“Some of the rivers are located in urban areas and receive more wastewater than lakes,” the authors say. “Sediments in river drainage areas are also likely hotspots for microplastics.”

Microplastics are ubiquitous in marine environments. These particles have pervaded every marine ecosystem in the world. Plastic pollution found in marine animals has ran the gamut from sea birds, sea snakes, and sea turtles to penguins, seals, and sea lions.

The extent of microplastic pollution in freshwater systems—like lakes and rivers—is less clear. However, recent studies are beginning to paint a bigger picture.

A few months ago, scientists in Germany discovered that rivers are responsible for a considerable amount of marine plastic pollution—with rivers in Asia being a heavy contributor.

Although this pollution can seem distant to humans, we are not isolated from it. Shellfish, such as the Asian clam, are a source of nutrition for billions of people, and are widely consumed throughout China. People typically eat clams without removing the digestive tract. As a result, the contents of a clam’s stomach—and plastics within it—become the contents of the consumer’s stomach. Ingestion of these microplastics is a possible health risk and has been shown to cause inflammatory reactions.

“Few studies have determined the level of microplastics exposure from freshwater shellfish consumption,” say the researchers of the current study. “So, it will be valuable to set the baseline for microplastic consumption by humans. Potential human health risks should not be ignored.”

Climate change threatens future stability of rice ecosystems

New research claims climate and land-use change will greatly lower rice yields by the end of the century.

Rice yields in the Philippines and Vietnam could decline 30% by the year 2100.

“Because of a temperature increase in the Philippines and Vietnam of up to 4°C, rice yields can be kept steady only at the expense of natural vegetation, which would likely reduce native habitat and biodiversity,” say the authors of the new study published in the journal Environmental Research Letters.

The researchers created simulation models (from 2000-2099) comprising seven study areas to arrive at these conclusions. For climate change, two future scenarios were considered: a 1.5°C-2°C trajectory and a 3°C-4°C trajectory. For land use change, three future scenarios were chosen: low rice conversion, high rice conversion, and one based on global economic trends. The scientists then determined how these models affected ecosystem services—benefits humans gain from the environment—provided by rice ecosystems.

Along with rice yields, the study predicted a climate-induced decline in two other ecosystem services: carbon storage and carbon sequestration.

Carbon storage, a plant’s ability to store carbon long-term, is estimated to decrease 15% by the end of the century. This loss of storage capacity is caused by less photosynthesis (absorbing carbon) and more respiration (releasing carbon). Just like the proteins in our bodies, proteins driving photosynthesis slow down at high temperatures.

Land-use change also worsened carbon storage. As land is converted to rice fields, forests are decimated and the stored carbon is released

The outcome of climate and land-use change on carbon sequestration is more nuanced, though. Sequestration can be thought of as a carbon scale: photosynthesis as a weight on one side and respiration as a weight on the other side. Overall, by the end of the century, respiration outweighed photosynthesis—carbon sequestration declined by 12%.

However, when land-use change was added in high amounts, carbon sequestration shot up. To rapidly grow, crop plants—like rice—imbibe large amounts of carbon, while releasing little. This is in contrast to older forests, which absorb less carbon as their growth slows.

Another ecosystem service, irrigation water, was projected to increase by 10%-20%. Despite this, rice yields still markedly decreased. Although more land-use somewhat offsets the effects of climate change on yields in the early 21st century, those offsets are later negated in the latter half of the century by rising temperatures.

As rice is a staple food for 3.5 billion people—nearly half of the world’s population—declining yields could have prodigious consequences. Rice cultivation is the main source of income for over 100 million households across the world.

Cultural identity is at stake, too. These ecosystems shape farmers’ values, spiritual experiences, and connection to the natural environment.

“Locally specific land use policies and development plans have to consider more than the availability of rice,” the researchers say. “Cultural services to maintain future human wellbeing must be included.”

Fetal heart defects join the growing risks of second-hand smoke

Mothers’ exposure to second-hand smoke increases the risk of fetal heart defects, according to a new study published in the journal Environmental Pollution.

Researchers found that mothers in Guangdong, China exposed to second-hand smoke were 44% more likely—compared to mothers lacking exposure—to give birth to children with heart defects.

However, second-hand smoke was not the only risk factor for heart defects. Low household income, migrant status, and the father’s alcohol consumption all contributed to increased risk of fetal heart defects.

“Our findings were consistent with the hypothesis that low socioeconomic status is associated with a higher risk of fetal heart defects,” say the authors of the study.

To confirm fetal heart defects, physicians were consulted and their diagnoses were confirmed by a fetal heartbeat monitor. To determine smoke exposure and other information, participants were interviewed in-person.

Several previous studies—one published in 2010 in Lithuania, and one published in 2011 in Italy—had similar results. Both studies found increased risk of fetal heart defects in children with fathers who smoked.

The authors of the current study, and many others, claim that smoking is a significant public health concern in China.

With 300 million smokers—nearly the entire population of the U.S.—China is the world’s largest consumer of tobacco. Of those millions, a large majority are men. Only 2% of women are current smokers. These statistics, the researchers say, suggest that a large number of non-smoking females are exposed to second-hand smoke daily.

It is estimated, that among non-smokers in China, 73% are exposed to second-hand smoke every day.

“Our findings may help to identify high-risk populations for fetal heart defects,” the researchers say. “This provides an opportunity for targeted preventive interventions.”