Environmental Discoveries
Humpback
whale tail, Reunion Island. Credit: François
Baelen / Ocean Image Bank
Bad breath from lakes
Around the world, there has been an increase in the number of small lakes, observed between the 1980s and 2019. The total area of lakes around the world has increased by about 46,000 km2 (roughly the area of Denmark).
This increase in lakes around the world, especially in the higher latitudes, is due to the melting permafrost and glaciers resulting in the formation of glacial lakes because of global warming, as well as the development of artificial reservoirs inland. Scientists were able to use remote sensing to map 3.4 million lakes and reservoirs around the world to determine their surface area and determine the changes over the last four decades. But why is this increase in lakes a concern for scientists? Lakes are known to emit greenhouse gases – carbon dioxide, methane, and nitrous oxide through the breakdown of organic matter – largely leaf litter that collects on the bottoms of the lakes – by microbes (bacteria and fungi). Smaller lakes (under one km2) disproportionately emit more carbon dioxide than larger lakes owing to the greater anaerobic activity in a smaller volume of water. Lakes may burp and emit such gases that visibly bubble to the surface. Today, the annual global emission of carbon dioxide from lakes is equivalent to that of the UK in 2012. Additional forms of emissions and further release of greenhouse gases are major concerns for scientists monitoring global warming.
It’s raining microplastic
This year scientists in New Zealand were able to measure the amount of microplastic that falls in rain, using a new technique capable of detecting plastics down to 50 microns. At Auckland University, scientists found an average of 5,000 microplastics per day within a one metre-square area of roof top that likely add up to 74 metric tonnes per year or the equivalent of three million plastic bottles. Comparisons with other cities around the world revealed a drastic underestimation of previous measurements of microplastics that settle because of limited methods to detect the tiniest of the microplastics (under 10 microns). A previous study done in London, for example, highlighted only 771 microplastic particles per square-metre mostly composed of plastic fibres. The most common types of plastics included plastics from grocery bags (polyethylene), protective gear such as masks and gloves (polycarbonate), and from food and beverage containers (polyethylene terephthalate or PET)
Sunscreen death to corals
Scientists are finally able to understand how sunscreen lotions damage corals. Many places around the world, such as Hawai`i and Mexico have already banned sunscreen impacting their coral reefs, especially those near very popular beaches. By testing on sea anemones – a close relative of corals – they found that the major ingredient in sunscreen – oxybenzone which blocks UV light – produces a toxin deadly to corals. Sunlight helps bind the oxybenzone to sugar to form the compound that can kill corals. Interestingly, much of the algae that lives in the corals were observed to soak up the compound and reduce the impacts. The compound directly kills baby corals and limits tissue healing when the coral is damaged. Major concerns surround the periods of ocean warming when the corals become bleached: without the allies of the coral symbiotic algae that protect against the chemical pollutants, corals will be especially vulnerable to climate change adding to local stressors related to pollution, overfishing etc.
Save the whales, store more carbon
Scientists are proposing that the protection and conservation of our largest marine animals can be a viable blue carbon solution for the mitigation of climate change. Whales, especially baleen whales, can grow up to 150 tonnes. As a long-lived species, they can roam the ocean for 100 years or more. Whales can also eat up to 4 % of their weight daily (up to 8000 lbs per day) and are therefore capable of being stable and long-term stores of carbon.
When whales die their bodies sink to the bottom of the ocean, resulting in the downward transfer of organic matter to the deep ocean ecosystems that slowly feed on the whale. How the carbon is retained or dispersed in this ecosystem is less known, but results in the long-term storage of carbon. Furthermore, the excrement of whales is rich in nutrients, especially in the open ocean. Whale waste results in the blooming of phytoplankton through photosynthesis (fixation of carbon) which is then transferred up the food chain to krill and other marine microorganisms feeding nekton and fish and the ocean megafauna. While 80 % of whale populations have been devastated from hunting, the global protection of whales serves the whole planet in the effort against climate change. It is the right thing to do for the whales and for us.
Plastic
(nurdles) pollution on a beach. Credit: Sören Funk
/ Ocean Image Bank
References
Hansel, Colleen M. "Sunscreens threaten coral survival." Science 376.6593 (2022): 578-579.
Pearson, Heidi C., et al. "Whales in the carbon cycle: can recovery remove carbon dioxide?." Trends in Ecology & Evolution (2022).
Pi, X., Luo, Q., Feng, L. et al. Mapping global lake dynamics reveals the emerging roles of small lakes. Nat Commun 13, 5777 (2022). https://doi.org/10.1038/s41467-022-33239-3
Wenxia Fan, Jennifer A. Salmond, Kim N. Dirks, Patricia Cabedo Sanz, Gordon M. Miskelly, and Joel D. Rindelaub. Evidence and Mass Quantification of Atmospheric Microplastics in a Coastal New Zealand City Environmental Science & Technology 2022 56 (24), 17556-17568
DOI: 10.1021/acs.est.2c05850
Vuckovic D. et al. Conversion of oxybenzone sunscreen to phototoxic glucoside conjugates by sea anemones and corals. Science. Vol. 376, May 6, 2022, p. 644. doi: 10.1126/science.abn2600.
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