Carrageenans are valuable marine polysaccharides derived from specific species of red seaweed (Rhodophyta) widely used as thickening and stabilizing agents across various industries. Kappaphycus alvarezii, predominantly cultivated in tropical countries, is the primary source of kappa-carrageenan. Traditional industrial extraction methods involve alkaline treatment for up to three hours followed by heating, which is inefficient and generates substantial waste. Thus, developing improved extraction techniques would be helpful for enhancing efficiency and reducing environmental impacts, solvent costs, energy consumption, and the required processing time. In this study, we explored innovative extraction methods, such as ultrasound-assisted extraction (UAE) and supercritical water extraction (SFE), together with other extraction methods to produce kappa-carrageenan from a new strain of K. alvarezii from the Philippines. FTIR-ATR spectroscopy was employed to characterize the structure of the different carrageenan fractions. We also examined the physicochemical properties of isolated phycocolloids, including viscosity, and the content of fatty acids, proteins, and carbohydrates. For refined carrageenan (RC), both the traditional extraction method and the UAE method used 1 M NaOH. Additionally, UAE (8% KOH) was employed to produce semi-refined carrageenan (SRC). UAE (8% KOH) produced a high yield of carrageenan, in half the extraction time (extraction yield: 76.70 ± 1.44), and improved carrageenan viscosity (658.7 cP), making this technique highly promising for industrial scaling up. On the other hand, SFE also yielded a significant amount of carrageenan, but the resulting product had the lowest viscosity and an acidic pH, posing safety concerns as classified by the EFSA’s re-evaluation of carrageenan as a food additive.

In forested streams, leaf litter decomposition is a vital ecosystem process, governed primarily by aquatic hyphomycetes. These fungi are crucial mediators of nutrients and energy to invertebrates and higher trophic levels. Very little information is available on the impact of low concentrations of different sizes of nanoplastic particles (NPPs) on leaf litter decomposition and aquatic hyphomycetes communities. Besides, NPPs impact on leaf litter nutritional quality and invertebrate feeding behaviour is unknown. We conducted a microcosm assay with varying concentrations (0-25 μg L^-1) of small (100 nm; SNPPs) and large (1000 nm; LNPPs) plastic particles to assess their impact on leaf litter decomposition, sporulation rates and community structure of aquatic hyphomycetes. Furthermore, leaf litter was retrieved and fed to invertebrates to assess feeding rates. Our results indicated that leaf litter decomposition, fungal sporulation and abundance were significantly affected by NPPs concentrations and sizes. By contrast, leaf litter nutritional quality was impacted only by sizes. The NPPs, particularly SNPPs, augmented leaf litter polyunsaturated fatty acids (18-31%), consequently improving food quality; however, invertebrates' feeding rates were not impacted. Overall, our study provides novel insights on the risks posed by NPPs with pronounced impact at the basal trophic level.

Amidst unprecedented anthropogenic pressure on marine ecosystems, seabirds can serve as sentinels for shifts in marine prey availability. We examined the diet and foraging ecology of 2 sympatric Procellariiformes, the Cape Verde shearwaterCalonectris edwardsiiand Bulwer’s petrelBulweria bulwerii, during their breeding period in Cabo Verde, West Africa. By analysing fatty acids (FAs), δ¹⁵N and δ¹³C values, and using GPS loggers, we quantitatively assessed the diet of both adults and chicks, estimated the isotopic niche of adult birds, and identified their main foraging regions. Our findings revealed annual variations in the diet of both adults and chicks, supported by quantitative prey estimates and FA signatures. Adult Cape Verde shearwaters consistently displayed a diet enriched in commercial fishes (>40%), with varying proportions of squid or non-commercial fishes across different years. Bulwer’s petrel displayed greater diet variability, consuming higher proportions of squid (54%), mesopelagic fishes (81%), and commercial fishes (29%) in 2017, 2018, and 2019, respectively. Chicks of both species exhibited varying diets across years. However, chick growth and fledging parameters remained fairly consistent among years. The isotopic niche, GPS tracking, and oceanographic conditions within foraging regions provided partial support for the annual variations observed in the diet of adults, especially for Cape Verde shearwaters. However, the diet differences for Bulwer’s petrels were less straightforward, likely due to the equitable distribution of their main prey. Notably, both species exhibited resilience in coping with unfavourable foraging conditions, enabling adult breeders to exploit a wide variety of prey resources without compromising breeding outcomes.

Understanding food-web structure is crucial to determine the functioning of ecosystems and sustainably manage resources. The Scotia Sea is an important area for Antarctic krill and toothfish fisheries, and one of the regions most impacted by climate change in the Southern Ocean. Whilst the pelagic Antarctic krill-centric food web has been investigated in reasonable detail, the structure of deep-sea food webs associated with toothfish fisheries remain largely unknown. Utilising stable isotopes and fatty acids as trophic proxies, we studied the deep-sea food-web structure in three locations of the Scotia Sea, from South Georgia (SG) to the South Sandwich Islands (SSI; divided into north and south). Our analyses indicate that all food webs were similar, presenting high trophic redundancy and similar vertical structure. All food webs had five trophic levels, with the 5th and 4th trophic levels mainly constituted of fish and the 3rd trophic level of cephalopods and crustaceans. However, some differences existed with the SG food web presenting larger diversity of producers and the bigeye grenadier Macrourus holotrachys in the highest trophic position, while Patagonian toothfish Dissostichus eleginoides and both Patagonian and Antarctic toothfish D. mawsoni were the top predators at SSI-North and SSI-South, respectively. Compared to coastal and pelagic food webs in the Southern Ocean, our results suggest that deep-sea food webs, including the benthic/demersal components, have a longer food-chain length. This study provides essential knowledge of the ecological variability of Southern Ocean deep-sea food webs while contributing to the management of resources within the SG and SSI Marine Protected Area.