The Project

The importance of phytoplankton biodiversity in global and local scale processes

The effect of a changing climate on the marine biodiversity and the fate of anthropogenic CO2 in the atmosphere are among the most pressing issues of our time. At global scale, phytoplankton, as primary producers that convert light and CO2 into biomass, stand at the base of the oceanic food web. Their importance as a food source for the pelagos and as a potential sink of atmospheric carbon has been widely recognized. Some phytoplankton groups have also been identified to have an important role in the global climate regulation and the atmospheric sulfur cycle. In addition, some phytoplankton species are able to cause harm through the production of toxins or by their accumulated biomass. Such outbreaks which typically occur in coastal areas are known as “harmful algal blooms” (HABs).

Diagram illustrating the role of phytoplankton in the sulfur cycle. Source: modified from Takahashi et al. (2011). Episode of a "red tide" algal bloom (non-toxic) of Noctiluca scintillans in New Zealand. Source: M. Godfrey.

Social impact of environmental changes associated to phytoplankton dynamics at local scale is also significant. For instance, when harmful algal blooms are formed the toxins travel up the food chain and they pose serious human-health threats and severely affect numerous industries and commercial fisheries, causing substantial economic losses.

Example of a HAB toxicity effect in fishes. Estimates of the average annual economic effects of HABs in the EU and the US, based on outbreaks in 1987-2000. Source: P. Hoagland and S. Scatasta (2006).

Advanced optical technologies for monitoring biodiversity of phytoplankton

Numerous studies over the past three decades have focused on the development of algorithms linking different processes such as estimation of primary production or detection of HABs to the primary pigment in phytoplankton, chlorophyll-a (Chla), a proxy for the phytoplankton biomass. However, given those phenomena such as the proliferation of algal blooms and production of sulfur components are taxon-dependent, further efforts are needed to go beyond the estimation of only Chla, which is common to all taxonomic groups. 

The gathering of higher-resolution biological information in the oceans fundamentally relies on bio-optical oceanography. As a non-intrusive approach, in situ and remotely-sensed optical observations of ocean waters provide information regarding the concentrations of optically significant constituents in seawater, and improve the possibilities to observe important biological and biogeochemical variables. Knowledge of the variability of bio-optical properties of the ocean is essential as it can be an important indicator of the health of the complex and biologically productive coastal ocean in the form of changing turbidity, diversity and distributions of species and harmful algal blooms and associated toxins. 

A significant increase in optical measurement capabilities in the ocean has been related to the following recent technological advances:

HYPERSPECTRAL SENSORS: high spectral resolution 
The capability to obtain high spectral resolution measurements at hundreds of narrow and closely spaced wavelength bands from the ultraviolet to near-infrared, with a resolution better than 10 nm, provides the opportunity for improvements in the extraction of information regarding phytoplankton assemblages and other optically significant constituents in seawater.
NEW OBSERVATIONAL PLATFORMS: high spatial & temporal resolution
Another key factor regarding increase optical measurement capabilities is the emergence of new ocean observing platforms such as Autonomous Underwater Vehicles (AUVs) and Unmanned Aerial Vehicles (UAVs). For optical oceanographers, those new technologies open the possibility to more accurately characterize complex environments and phytoplankton distribution from large scale patterns (i.e., using UAVs) to small scale structures (i.e., using AUVs).