Microplastics in the Ocean: Vertical transfer through intertidal food webs

Project Description

This project aims to better understand the fate of microplastics (plastic fragments of < 5mm) in the marine environment. Microplastics (MP), have been found from highly urbanized areas to the remote Antarctic. It is starting to become clear that MPs are ingested by many marine organisms, but the implications of this are not yet known. Some animal groups are particularly poorly-studied, most notably marine invertebrates. For my PhD, I am focussing on assessing MP ingestion by invertebrates from different trophic levels and feeding groups with the goal to model trophic interactions. After having focused on the highly urbanized Humber estuary (UK) during my 2020 sampling campaign, the comparison with a second site with similar conditions, the Ria Formosa, will allow me to broaden the relevance of my models. Within the Assemble project I propose to complete a comprehensive MP sampling and classification in the Ria Formosa, this will allow me to determine:

1. The MP sinks and sources in an enclosed lagoon system including a range of different marine habitat types.
2. Which species ingest the most MP and how it varies with feeding mode and habitat type.
3. How MP move through the marine food webs and which trophic levels they are likely to accumulate in.
4. Whether this data can be used to predict the fate of MP in marine food webs.

The Ria Formosa is a large tidal lagoon in southern Portugal and characterized by a series of channels and barrier islands producing a diverse array of sheltered and exposed marine habitats. The Ria is a protected area and an important feeding ground for birds, but it is also a potential hotspot for MP pollution from land via wastewater and run-off and also from the many aquaculture installations in the lagoon. Recent publications have shown MP accumulation in almost all habitat types in the lagoon. Both the Humber estuary and the Ria Formosa are important wetland sites, providing food and shelter for many standing and overwintering birds, which will be at high risk of ingesting MP by foraging for benthic invertebrates. Like so, it would be very interesting to conduct my research there, building from and expanding the existing research in Ria Formosa.

For this project I will sample a range of different intertidal habitat types (e.g. sand, mudflats and Zostera beds) and benthic animal species; comparing the amount and nature of MP found. Environmental factors and the presence of vegetation may favour accumulation in specific areas. I will be able distinguish factors favouring the settlement of plastics and identify pathways of pollutants in marine food webs. Ultimately, this project will provide data for comparison of MP pollution between the Humber estuary and the Ria Formosa, and will give new insights on the fate of MP in different intertidal ecosystems.