Periodic Reporting for period 2 - PLOCEAN (Plastic impacts on Ocean's biogeochemical cycles in the Anthropocene)
Período documentado: 2023-07-05 hasta 2024-07-04
PLOCEAN project aims at understanding the behavior plastic debris in the marine environment and their interaction with microbes and the natural biogeochemical cycling of elements, like carbon, marine aggregates and marine snow. This helps tracking sources and vertical residence of plastic in the water column that may influence microplastics buoyancy and fate, as well as how plastic can in turn interact with organic aggregates formation and carbon content. PLOCEAN addresses important knowledge gaps for research priorities in the study of plastics in the marine environment: 1) plastic fluxes from land to sea and within the marine biotic and abiotic compartments; 2) biogeochemical processes driving plastic bioavailability for marine organisms; and 3) the role of plastic as a new component of marine biogeochemical cycles. These themes are important for society because plastic is being considered as a planarity boundary threat but its wider interaction with marine life and the functioning of the oceans has still many uncertainties.
The research objectives addressed are the following:
1) Understanding plastic fluxes from land to sea and within the marine biotic and abiotic compartment (WP1: Land-to-Sea Fluxes)
2) Understanding the environmental factors that determine temporal microbial selection of plastic surfaces (WP2: Aggregation)
3) Biogeochemical processes driving plastic bioavailability for marine organisms and understanding the role of plastic as a new component of the marine biogeochemical cycle (WP3: Distribution in the Water Column).
The research objectives addressed are the following:
1) Understanding plastic fluxes from land to sea and within the marine biotic and abiotic compartment (WP1: Land-to-Sea Fluxes)
2) Understanding the environmental factors that determine temporal microbial selection of plastic surfaces (WP2: Aggregation)
3) Biogeochemical processes driving plastic bioavailability for marine organisms and understanding the role of plastic as a new component of the marine biogeochemical cycle (WP3: Distribution in the Water Column).
PLOCEAN is articulated into 4 work packages (WP1, WP2, WP3 and WP4). WP1 to WP3 relate to research, while WP4 relates to outreach. The outgoing phase has focused on the coastal ecosystem of the Indian River Lagoon (IRL) (FL, USA), the most biodiverse lagoon ecosystem in the Northern Hemisphere hosting at least 10,000 different species of plants and animals. The lagoon is a shallow water system (~1.2 m depth) with high amounts of plastic in the benthic zone; it is suffering from excess nutrient loads from wastewater effluents and microplastics were found in the tissues of crabs and oysters. As a comparison, the North Atlantic Ocean and Northern European waters are studied to see differences and similarities across environments. In WP1, a one-year monitoring of the IRL was performed (2021-2022). Samples were collected with a neuston net, and DNA was isolated from the plastic particles for genomic analysis of microbial communities (the plastisphere). Microplastic samples, after DNA extraction, were scanned by FT-IR to determine polymer type and oxidation state. Additionally, IRL sediment samples from 4 different sites were analyzed by µFT-IR for microplastics (> 20 µm) amount and composition to compare water and sediment environments. WP2 addressed the microbial selection for plastic polymers by work on board a German RV across the Northern Atlantic and based on the preliminary results on the amount of microbial DNA retrieved from the plastisphere during the cruise, one exposure experiment in the IRL on selected polymers to understand early microbial colonization and selection, as well as for comparing differences between the two environments. In WP3, work was done on sediment trap data from the North Atlantic Ocean to determine fluxes of marine snow and plastic in relation to seawater conditions (e.g. salinity, oxygen and temperature), and availability of aggregates (plastic and marine gel particles) for organisms at specific depths (study published). Additionally, the analysis of long-term sediment trap samples deployed in Northern European waters is in progress (for µFT-IR to determine the amount of plastic and other components). In WP4, the Covid-19 pandemic made the activity in presence difficult at the beginning. However, in 2021 PLOCEAN was remotely present at Science is Wonderful! Week and involved FAU-Harbor Branch volunteers in sampling the IRL for microplastics. In the summer of 2022, PLOCEAN engaged in a 7-weeks plastics summer camp for kids at Harbor Branch: samples collected by beachcombing were analyzed and every week an explanatory video with the week’s results was delivered and presented to the kids. In 2023, PLOCEAN was present at the Science is Wonderful! Event in Bruxelles with several activities. A video for school curricula was shot and will be available on the Science is Wonderful! EU website later in the fall of 2023. From June to December 2023 PLOCEAN is also involved in a citizen-science activity in the Mediterranean Sea with microplastics sampling and analysis for plastisphere community composition.
From the research objectives and WPs, genomic analyses and bioinformatics are in progress and more samples will be sent out for sequencing in the upcoming months. Plastic polymer analysis by FT-IR from the activities highlighted so far in all WPs shows that Polyethylene (PE), Polypropylene (PP) and PE:PP co-polymers are so far the most abundant polymer types retrieved in the sediments, surface waters and beaches along the IRL (FL, USA), as well as the most abundant surface polymer types sampled in the North Atlantic Ocean by surface trawls. From the study published for the North Atlantic Ocean where plastics were captured by sediment traps, Polyethylene Terephthalate (PET) was found included in marine aggregates. It is likely that other polymer types are present in marine aggregates too and is the objective of ongoing and upcoming work and data analysis.
From the research objectives and WPs, genomic analyses and bioinformatics are in progress and more samples will be sent out for sequencing in the upcoming months. Plastic polymer analysis by FT-IR from the activities highlighted so far in all WPs shows that Polyethylene (PE), Polypropylene (PP) and PE:PP co-polymers are so far the most abundant polymer types retrieved in the sediments, surface waters and beaches along the IRL (FL, USA), as well as the most abundant surface polymer types sampled in the North Atlantic Ocean by surface trawls. From the study published for the North Atlantic Ocean where plastics were captured by sediment traps, Polyethylene Terephthalate (PET) was found included in marine aggregates. It is likely that other polymer types are present in marine aggregates too and is the objective of ongoing and upcoming work and data analysis.
During the first phase of PLOCEAN several samples were collected from different environments to understand the microbial selection and attachment on plastic and microplastics debris, in particular for what concerns different plastic polymer types and early colonization steps. The microbial DNA is being studied to understand not only the community composition but also the possible genes shared by the community and functional traits that may be common on plastic or depend on environmental conditions. The analysis of these samples is in progress and we expect to have clear comparisons across data and environments by the end of the project. Steps in our understanding of plastic fluxes and biogeochemical interactions were made in WP3, since for the first time in situ measured vertical fluxes of microplastics were provided by our published study (Environ. Sci. Technol. 2022, 56, 22, 15638–15649, https://doi.org/10.1021/acs.est.2c04712). The study also showed that by the interaction with biogenic polymers plastic can be embedded into rapidly sinking particles also known as marine snow, and that the carbon contained in plastic can represent a non-negligible fraction of the total downward flux of particulate organic carbon to the deep ocean. The deployment of sediment traps as a tool to study plastic fluxes has been recently published (Galgani, L., H. Hepach, K.W. Becker, and A. Engel. 2023. Sediment traps: A renowned tool in oceanography applied to new marine pollutants. Oceanography 36-Supplement 1:52–53, https://doi.org/10.5670/oceanog.2023.s1.16.). The work in progress in PLOCEAN focused on plastic interaction with microbes and seawater biogenic components, can shed light on important pathways that regulate the transport of plastic and microplastics in marine systems and on potential interferences with the marine carbon cycle and ecosystem functioning, with ecosystem’s health implications that can have societal and economical repercussions.