What are phytoplankton?
Marine phytoplankton are microscopic single celled algae, growing in the surface layer of the ocean. Similar to plants on land, marine algae grow via a process called photosynthesis, where the phytoplankton cells harness light energy from the sun and use this in combination with water and carbon dioxide to produce organic carbon and oxygen, in a process called primary production. They grow and bloom depending on light and nutrient availability in the water column. Based at the bottom of the marine pelagic food chain, phytoplankton are “the grass of the sea”, accounting for ca. 40% of global primary production.
Phytoplankton cells photographed through the optical microscope lens. Magnification is 100x.
Focus of this research
The main focus of this study, in the framework of the Marine Climate Change National Research Programme, is to investigate changes in the abundance, distribution, and structure of phytoplankton communities in the North East Atlantic and Irish coastal waters in relation to altered conditions of the marine environment as induced by global change. Existing phytoplankton time series datasets include coastal monitoring programmes (Water Framewrok Directive and, Phytoplankton National Monitoring Program), oceanographic cruises on board national research vessels, and satellite data of ocean colour. Relationships with the ocean’s physical variables, such as sea surface temperature and the natural modes of climate variability (North Atlantic Oscillation Index; Atlantic Multidecadal Oscillation, Eastern Atlantic patterns), will be examined.
Recent scientific studies have demonstrated that warmer atmospheric temperature increases thermal stratification of the water column, resulting in lower amounts of phytoplankton biomass at mid-latitudes. Changes in phytoplankton species abundance have also been demonstrated from long term time series studies in the United States and the United Kingdom, with a noticable decline in the abundance of diatoms such as Skeletonema and Odontella species.
A decline in the amount of phytoplankton or a change in species composition is likely to have a knock-on effect on the marine food chain from zooplankton to commercial fisheries in addition to a reduction in the amount of carbon dioxide that is removed from the atmosphere. Increased stratification and a decrease in nutrient levels are likely to have an effect on the phytoplankton community structure such as changes in the geographic distribution of species associated with more turbulent water and possible increase in harmful algal blooms events (see below).
Marine mortalities on the Irish west coast following the bloom of toxic phytoplankton species Karenia mikimotoi, in 2005.