The Overlooked PM Cycle through Marine Animals

The incomplete combustion of vegetation fires and burning fossil fuels release fire-derived carbon, often referred to as black carbon [1]. The BC constitutes a global environmental issue, especially those with diameters of a few nanometers to tens of micrometers. Like those with a diameter of around 1um (PM1) or smaller, small particles even affect human health.

Most of this BC enters the atmosphere, but the airborne BC eventually falls back to the ground or the oceans. A portion of what falls on land enters the rivers, which mostly empty into the oceans. Studies on the fate and impact of the PM in the oceans have mainly concerned input sources across the air-water interface and reactions in the water column and sediments. The atmospheric aerosol deposition is an essential source of macro and micronutrients (N, P, C, Si, and Fe) to the oceans. Most studies of such an aerosol deposition in the oceans relate to how they impact nutrients and toxic metals’ biogeochemical cycles and how they affect primary productivity [2-4]. Investigation of PM in marine animals has largely been overlooked.

It has been shown in the laboratory that PM may generate inferior locomotion, feeding, growth, and fertility survival problems in aquatic snail Parafossarulus striatulus [5]and the rotifer Brachionus calyciflorus [6]. Although ingestion of PM by wild aquatic animals is also expected, to the best of our knowledge, PM1 has only been detected in wild sea anemones collected around coastal waters of Taiwan due to technical difficulties [7]. However, there is no reason for the absence of PM1 in sea anemones in other world regions, but this remains to be proven. Further, there is a reasonable ground for the existence of PM in other marine animals. Here we show that PM is indeed found in corals.

Small stony coral fragments of Tubastraea coccinea were collected from the Kuishantao Islet on the northeastern coast of Taiwan by SCUBA diving in June 2018. After narcotization, relaxation, fixation, and cleaning, the coral samples were decalcified in 5% HCl. The decalcified samples were washed by phosphatebuffered saline before conducting the histological sections. The sections were with or without Giemsa stain [8] and were examined under a light microscope equipped with a camera system. Detailed methods can be found in Liu et al. [7]. PM was observed in the mesenterial filaments of the stony coral T. coccinea (Figure 1). The PM was round with black color, which was evident in the nonstaining micrograph. The size of PM varied from < 0.5 to 6.5 μm.

Figure 1: Distribution of particulate matter (PM) in the stony coral Tubastraea coccinea sampled at the Kuishantao Islet in June 2018. A. External morphology. B. PM in a cross-sectioned coral polyp with Giemsa stain. C. Enlarged image of (B) without Giemsa stain. →: PM; me: mesentery; mf: mesenterial filaments; mu: mucocytes; t: tentacle.

Our studies on sea anemones [7] and the stony coral can at most be called exploratory. It is hoped that other studies would detect PM in other marine animals. Investigation into the physiological effects of PM and how it moves up the food web is also urgently needed [8].

The authors are grateful to the anonymous reviewers for their constructive comments on this manuscript. The authors like to express their appreciation to the SeaWatch Company and Mr. Chen-Yun Hsieh, for the field work. Dr. Chienhsun Chen and the Taiwan Ocean Research Institute generously facilitated the use of light microscopes. Financial support from the Asia-Pacific Ocean Research Center at the National Sun Yat-sen University with funding from the Ministry of Education, Taiwan, and the ROC’s Ministry of Science and Technology (MOST 110-2611-M-110-008; MOST 110- 2621-M-110-003) are acknowledged.

1. Wagner S, Brandes J, Spencer RGM, Ma K, Rosengard SZ, et al. (2019) Isotopic composition of oceanic dissolved black carbon reveals non-riverine source. Nat Commun 10: 5064.
2. Chen CTA, Wang SL (1999) Carbon, alkalinity and nutrient budget on the East China Sea continental shelf. J Geophys Res 104(C9): 20675-20686.
3. Ventura A, Simões EFC, Almeida AS, Martins R, Duarte AC, et al. (2021) Deposition of aerosols onto upper ocean and their impacts on marine biota. Atmosphere 12: 684.
4. Bikkina P, Sarma VVSS, Kawamura K, Bikkina S (2021) Dry deposition of inorganic and organic nitrogen aerosols to the Arabian Sea: Sources, transport, and biogeochemical significance in surface waters. Mar Chem 231: 103938.
5. Hartono D, Lioe B, Zhang Y, Li B, Yu J (2017) Impacts of particulate matter (PM2.5) on the behavior of freshwater snail Parafossarulus striatulus. Sci Rep 7(1): 644.
6. Verma V, Rico-Martinez R, Kotra N, Rennolds C, Liu J, et al. (2013) Estimating the toxicity of ambient fine aerosols using freshwater rotifer Brachionus calyciflorus (Rotifera: Monogononta). Environ Pollut 182: 379-384.
7. Liu LL, Hsieh CY, Kuo MY, Chen C, Shau YH, et al. (2020) Evidence for fossil fuel PM1 accumulation in marine biota. Environ Sci Technol 54(7): 4068-4078.
8. Cramer AD, Rogers ER, Parker JW, Lukes RJ (1973) The Giemsa stain for tissue sections: An improved method. Am J Clin Pathol 60(2): 148-156.