Selenium (Se) is an essential trace element for humans and animals. Its necessity for plants is still under examination. Due to the contradictory nature of Se and its significance, it has received much interest in recent years. Se deficiency can be harmful to humans, yet almost a billion people are deficient. Its deficiency has been associated with cancers, impairment of organs, and a number of other ailments. The biofortification of plants and livestock is a guaranteed practice to increase human selenium consumption. Strategies such as foliar spraying, the direct application of Se in plants and Se feed, and injections in livestock have been employed. Se biofortification has been shown to have additional beneficial effects in plants and livestock. In plants, it has been reported to mitigate different types of stress and increase yield. In animal biofortification, Se has been shown to reduce the detrimental effects of ailments and promote healthy growth. Se biofortification, nevertheless, confronts a number of difficulties. For instance, the bulk of biofortified products must be prepared before consumption, lowering the Se concentration. The objective of this review is to convey the current understanding of the Se biofortification of plants and animals, as well as its difficulties, taking into account both the detrimental consequences of Se deficiency and benefits of Se biofortification.

Very little attention has been paid to quantifying ammonia (NH₃) emissions from Antarctic marine animal excreta. In this paper, penguin guano and ornithogenic soils from four penguin colonies and seal colony soils were collected in coastal Antarctica, and laboratory experiments were conducted to investigate potential NH₃emissions and effects of environmental factors on NH₃fluxes. Ammonia fluxes were extremely low from the frozen samples. Significantly enhanced NH₃emissions were observed following thawing. The mean fluxes were 7.66 ± 4.33 mg NH₃kg^-1h^-1from emperor penguin guano, 1.31 ± 0.64 mg NH₃kg^-1h^-1from Adélie penguin guano and 0.33 ± 0.39 mg NH₃kg^-1h^-1from seal colony soils during the thawing period. Ammonia emissions from penguin guano were higher than those from ornithogenic soils during freezing-thawing cycles (FTCs). The temperature, pH, total nitrogen (TN) and drying-wetting conversion had an important effect on NH₃fluxes. For the first time, we provide a quantitative relationship between NH₃flux and temperature, TN and pH. Our results show that marine animal excreta and ornithogenic soils are significant NH₃emission sources. In coastal Antarctica, FTC-induced NH₃emissions might account for a large proportion of annual flux from marine animal colonies due to high freezing-thawing frequency.

Most studies on phosphorus cycle in the natural environment focused on phosphates, with limited data available for the reduced phosphine (PH₃). In this paper, matrix-bound phosphine (MBP), gaseous phosphine fluxes and phosphorus fractions in the soils were investigated from a penguin colony, a seal colony and the adjacent animal-lacking tundra and background sites. The MBP levels (mean 200.3 ng kg⁻¹) in penguin colony soils were much higher than those in seal colony soils, animal-lacking tundra soils and the background soils. Field PH₃ flux observation and laboratory incubation experiments confirmed that penguin colony soils produced much higher PH₃ emissions than seal colony soils and animal-lacking tundra soils. Overall high MBP levels and PH₃ emissions were modulated by soil biogeochemical processes associated with penguin activities: sufficient supply of the nutrients phosphorus, nitrogen and organic carbon from penguin guano, high soil bacterial abundance and phosphatase activity. It was proposed that organic or inorganic phosphorus compounds from penguin guano or seal excreta could be reduced to PH₃ in the Antarctic soils through the bacterial activity. Our results indicated that penguin activity significantly increased soil phosphine formation and phosphorus contribution, thus played an important role in phosphorus cycle in terrestrial ecosystems of maritime Antarctica.

We investigated nutrient composition and the potential for greenhouse gas production in Antarctic penguin guano, ornithogenic soils and seal colony soils through a laboratory incubation experiment. Total organic carbon contents ranged from 0.2–14.7% and total nitrogen contents ranged from 0.05–3.60% across all the samples. Penguin guano and the soils had the δ¹³C_orgvalues of -28.4‰ to -22.8‰ and highly enriched δ¹⁵N values (8.28–35.51‰), indicating a rapid N cycling in local ecosystems. The mean CO₂and CH₄emission rates from penguin guano were significantly higher than those from the soils under aerobic or anaerobic conditions. The CO₂-C/TOC rate indicated that the bioavailability of TOC was markedly higher in penguin guano than in the soils. These soils showed higher N₂O emission rates under anaerobic conditions, indicating that denitrification may be the major process in N₂O emission. The CO₂and CH₄emissions have a significant correlation with TOC in both penguin guano and the soils. Our results show that marine animal excreta are an important factor determining storage and composition of nutrients in coastal Antarctica, and that they may considerably affect current and future net fluxes of greenhouse gases in this region.