Marine biology – Sponges as biomonitors of m

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Sponges are filter feeders that live on particles, but they can also ingest microscopic fragments of plastic and other anthropogenic pollutants. They can therefore serve as useful bioindicators of the health of marine ecosystems.

The pollution of the world’s oceans from the anthropogenic input of plastics and other industrial wastes represents a growing threat to the viability of marine ecosystems. – And because these pollutants accumulate in fish, crustaceans and molluscs, they enter the food chain and can be ingested by human consumers. Microparticles smaller than 5 mm present a particularly insidious problem. This class of pollutants includes microplastics and textile fibers, as well as synthetic chemicals found in consumer products such as household cleaners and cosmetics. It is therefore imperative to develop methods to quantify the extent of the threat in order to develop effective measures to mitigate it. In a new publication in the journal Environmental pollution, a research team led by Ludwig-Maximilians-Universitaet (LMU) in Munich, Professor Gert Wörheide (Department of Earth and Environmental Sciences, and GeoBio-Center) shows that marine sponges have great potential in as bioindicators for monitoring microscopic pollutants in the seas.

Sponges are sometimes referred to as ocean vacuums. They feed on tiny particles suspended in currents, filtering them from the seawater that flows through their highly porous tissues – which are supported by mineralized skeletons in many species. To assess their utility as bioindicators for microparticulate pollutants, Wörheide and his colleagues studied 15 samples of a type of mineralized sponges belonging to the class known as “demosponges” from an offshore coral reef. off the coast of Bangka Island in North Sulawesi (Indonesia). “We chose this site because Southeast Asia is a hotspot for plastic pollutants in the oceans,” explains Elsa B. Girard, lead author of the study. Girard recently graduated from LMU’s master’s program in Geobiology and Paleobiology, and his contribution to the article was part of his master’s thesis. “Given the impact of global warming and overexploitation of marine resources, local sponge species could act as useful biomonitors of micropollutants, and help us develop appropriate measures to reduce the deleterious effects of these substances on reef communities, ”she explains. .

In cooperation with specialists from the SNSB-Munich State Mineralogical Collection and the Department of Chemistry and Nanoscience Center (CeNS) of LMU, the biologists used two innovative methods to examine the samples taken from the reef. Using two-photon excitation microscopy (TPE), they confirmed that sponges do incorporate microparticles into their tissues. Then they used Raman spectroscopy to characterize the nature of the particles themselves. The data obtained with the second technique revealed the presence of no less than 34 different types of microparticles in the tissues of the sponges. The spectrum ranged from plastics such as polystyrene to cotton and titanium dioxide (TiO2). TiO2 is used in stains and paints, in addition to being a component of sun lotions. In addition, the variation in the composition of the microparticles in the different samples seems to reflect the spatial variations in the type of particles in the surrounding water.

The researchers detected between 90 and 600 particles per gram of dried tissue in their sponge samples. “As sponges can weigh up to several hundred grams, we estimate based on these results that each can accumulate more than 10,000 particles,” explains Wörheide. “This makes them promising candidates for the task of monitoring levels of anthropogenic microparticle pollution in the oceans.” With the exception of molluscs, few other species have the required properties of marine bioindicators. According to the study’s authors, sponges have several other “qualifications” for the job. They are abundant and permanently active as filter feeders. In addition, measurements of pollution levels can be performed on tissue samples (biopsies) without affecting the viability of the organisms.

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