Mark G. J. Hartl

Deep-sea polymetallic nodule mining is in the exploration phase at present with some groups proposing a move towards extraction within years¹. Management of this industry requires evidence of the long-term effects on deep-sea ecosystems², but the ability of seafloor ecosystems to recover from impacts over decadal scales is poorly understood³. Here we show that, four decades after a test mining experiment that removed nodules, the biological impacts in many groups of organisms are persistent, although populations of several organisms, including sediment macrofauna, mobile deposit feeders and even large-sized sessile fauna, have begun to re-establish despite persistent physical changes at the seafloor. We also reveal that areas affected by plumes from this small-scale test have limited detectable residual sedimentation impacts with some biological assemblages similar in abundance compared to control areas after 44 years. Although some aspects of the modern collector design may cause reduced physical impact compared to this test mining experiment, our results show that mining impacts in the abyssal ocean will be persistent over at least decadal timeframes and communities will remain altered in directly disturbed areas, despite some recolonization. The long-term effects seen in our study provide critical data for effective management of mining activities, if they occur, including minimizing direct impacts and setting aside an effective network of protected areas^4,5.

The composition, abundance and distribution of macroplastics (MAPs) and microplastics (MPs) in the Vinces and Los Tintos rivers were determined in three sites (Pueblo Nuevo, Santa Marianita, Los Tintos) from the low basin in the coastal province of Guayas, Ecuador. MAPS were recorded by visual census, covering a total distance of 140 m, and MPs were extracted in the intertidal sediments via density separation using a saturated NaCl solution, and these were counted using a stereomicroscope. A total of 940 plastic items were identified. The predominant debris was plastic with 85.2%, followed by manufactured materials and metals. The Vinces River contained the highest abundance of plastic in the locality of Pueblo Nuevo. The most abundant plastic was MPs. The most common MAPs were plastic bags (23%), food packaging (17%) and foamed plastic (8%). MP size classes quantified between 0.15 and 2.52 mm in intertidal, very fine sandy sediment and decreased in abundance with increasing grain size. The most common MPs were fibres (65.2%) (black (43.8%) and blue (25.8%)), and their distribution has a high correlation with population density and water flow direction: Santa Marianita 5.55 g⁻¹, Pueblo Nuevo 7.39 g⁻¹, Los Tintos 8.17⁻¹. A significant abundance of fibres was identified in Pueblo Nuevo. The plastic spatial distribution revealed major plastic pollution in areas where recreational and tourism activities have been developed. Therefore, we recommend implementing awareness campaigns by educating businesses, residents and tourists on managing solid waste (especially plastic) and wastewater. Our results can serve as a baseline for future plastic monitoring in the area.

The potential for trophic transfer of single-walled carbon nanotubes (SWCNTs) was assessed using the green algae Tetraselmis suecica and the blue mussel Mytilus edulis in a series of laboratory experiments. Swanee River Natural Organic Matter (SRNOM)-dispersed SWCNTs were introduced into growing algal cultures. Light microscopical observations, confirmed by scanning electronic microscopy (SEM) and Raman spectroscopy, showed that SWCNT agglomerates adhered to the external algal cell walls and transmission electronic microscopy (TEM) results suggested internalization. A direct effect of SWCNT exposure on the algae was a significant decrease in growth, expressed as chlorophyll a concentration and cell viability. Mussels, fed with algae in the presence of SWCNTs, led to significantly increased pseudofaeces production, indicating selective feeding. Nevertheless, histological sections of the mussel digestive gland following exposure showed evidence of SWCNT-containing algae. Furthermore, DNA damage and oxidative stress biomarker responses in the mussel haemocytes and gill tissue were significantly altered from baseline values and were consistent with previously observed responses to SWCNT exposure. In conclusion, the observed SWCNT-algal interaction demonstrated the potential for SWCNT entrance at the base of the food chain, which may facilitate their trophic transfer with potential consequences for human exposure and health.