Vanishing clams on an Iberian beach: local consequences and global implications of accelerating loss of shells to tourism

Understanding the interactions between cephalopods and marine litter: A research evaluation with identification of gaps and future perspectives

Litter is known to negatively affect numerous marine organisms, but the extent of such impacts is not well known for several groups, including cephalopods. Considering the ecological, behavioral and economic importance of these animals, we reviewed the types of interactions between cephalopods and litter in the scientific literature, to evaluate impacts and knowledge gaps. We found 30 papers, which included records of microplastic ingestion and the transfer of synthetic microfibers along the food web. The largest number of records involved litter use as shelter, and the common octopus was the most frequent species. At first sight, litter use as shelter could appear to be a potential positive effect, but it is necessary to clarify the implications of this choice and its long-term consequences. Regarding ingestion and trophic transfer, further research is needed to elucidate its occurrence and impacts on cephalopods and their predators, including humans.

In an octopus's garden in the shade: Underwater image analysis of litter use by benthic octopuses

Benthic octopuses have been widely documented in artificial shelters for decades, and this use is apparently increasing. Despite any possible positive effects, the use of litter as shelter could have negative implications. In this work, we aimed to elucidate the interactions of octopuses with marine litter, identifying types of interactions and affected species and regions. To achieve this, we obtained 261 underwater images from 'citizen science' records, and identified 8 genera and 24 species of benthic octopuses interacting with litter. Glass objects were present in 41.6% of interactions, and plastic in 24.7%. Asia presented the highest number of images, and most records were from 2018 to 2021. Citizen science provided important evidence on octopus/marine litter interactions, highlighting its value and the need for more investigations on the subject. This information is fundamental to help prevent and mitigate the impacts of litter on octopuses, and identify knowledge gaps that require attention.

Tourism and urban development as drivers for invertebrate diversity loss on tropical islands

Oceanic islands harbour a disproportionately high number of endemic and threatened species. Rapidly growing human populations and tourism are posing an increasing threat to island biota, yet the ecological consequences of these human land uses on small oceanic island systems have not been quantified. Here, we investigated and compared the impact of tourism and urban island development on ground-associated invertebrate biodiversity and habitat composition on oceanic islands. To disentangle tourism and urban land uses, we investigated Indo-Pacific atoll islands, which either exhibit only tourism or urban development, or remain uninhabited. Within the investigated system, we show that species richness, abundance and Shannon diversity of the investigated invertebrate community are significantly decreased under tourism and urban land use, relative to uninhabited islands. Remote-sensing-based spatial data suggest that habitat fragmentation and a reduction in vegetation density are having significant effects on biodiversity on urban islands, whereas land use/cover changes could not be linked to the documented biodiversity loss on tourist islands. This offers the first direct evidence for a major terrestrial invertebrate loss on remote oceanic atoll islands due to different human land uses with yet unforeseeable long-term consequences for the stability and resilience of oceanic island ecosystems.

Marine litter disrupts ecological processes in reef systems

Marine litter (ML) contaminates essentially all global coastal and marine environments and drives multiple ecosystem-level effects. Although deleterious effects of ML on several organisms have been investigated in the last years, this information tends to be dispersed or underreported, even in marine biodiversity hotspots such as reef ecosystems. Two are the main goals of this paper: (i) to integrate and synthesize current knowledge on the interactions of ML and reef organisms, and (ii) to evaluate the multiple disruptions on the ecological processes in reef systems. We report here ML-driven ecological disruptions on 418 species across eight reef taxa, including interactions that were previously not addressed in detail, and evaluate their major conservation implications. These results can help raise awareness of global impacts on the world's reefs by highlighting ML associations in different reef systems around the world, and can aid in ML input reduction and marine management.