Download AEBR 374 Zooplankton and microplastics between New Zealand and the Ross Sea 2023–26, and the effects of sub-sampling of Continuous Plankton Recorder data

Zooplankton are small, drifting animals living in the ocean that are a crucial link in marine food webs and actively transport carbon to the deep sea. We have been sampling zooplankton in cold Subantarctic and Southern Ocean waters south of New Zealand since 2008, and the information helps us to understand how climate change is affecting marine ecosystems and to anticipate future change. Our study also monitors microplastics in the ocean, which have been increasing over the last 15 years. The samples of zooplankton and plastic are collected by an instrument called the Continuous Plankton Recorder (CPR) which is towed by a Sanford Ltd fishing vessel, the Fishing Vessel San Aotea II, as it travels between Timaru and the toothfish fishery grounds in the Ross Sea, Antarctica every year. This project extended the time series of observations by another two years and also investigated if subsampling could help us continue the work in a more affordable way. Our study found that subsampling the data 2:1 (that is, only analysing every-other sample of the continuous silk) makes the analysis cheaper and faster, only reduces the data quality by a small amount and does not affect our ability to understand change in zooplankton communities or our ability to monitor microplastic pollution.