TRICOFER

Trichodesmium fertilization on Marine Productivity in the Canary Islands

About

The aim of this project is to prove the following hypothesis: Trichodesmium spp, a colonial diazotrophic cyanobacteria, fertilizes the Canary Islands waters leading to an increase in primary production. The progressive temperature increase and water column stratification occurring in the Canary Islands region has resulted into recurrent Trichodesmium blooms in the last few years. When colonies aggregate in the surface, they collapse and die, liberating high inorganic nutrient and organic matter concentrations to the water column (before sinking), which favour the exuberating growth of other planktonic organisms, acting as a fertilizer in the marine food web. If our hypothesis is correct, the increasing occurrence of Trichodesmium blooms in the near future could partially palliate the reduction in primary productivity in the Canary region as predicted by climatic models, due to the sea surface progressive warming.

This study will be carried out combining controlled experiments, by adding extracts of supernatant from cell exudates that they release when dying on natural water samples, and high spatial sampling at sea (10-100m) through Trichodesmium blooms, to observe the organic matter and nutrient fertilization effect associated to these blooms (in situ validation). The project is presented from a clearly multidisciplinary approach, by a consortium of researchers from 4 research groups from the University of Las Palmas de Gran Canaria, including biological oceanography studies, remote sensing, biogeochemistry, ecophysiology, molecular biology, marine ecology and climate change.

Objectives

Quantify superficial Trichodesmium blooms abundance throughout the year using remote sensing (FAI index; "Floating Algae Index), for the period 2017-2021, and linking this information with environmental factors (such as water temperature and stratification).

Objective 1

Study, at small scale level (10 -100 m), the change in seawater properties, concentration of inorganic and organic nutrients, and bacteria, phytoplankton and zooplankton communities (metazoan food web versus microbial food web/microbial loop), by sampling surface blooms of Trichodesmium, to know the impact of fertilization on the environment.

Objective 2

Develop fertilization experiments with exudates extracted from collapsed blooms where Trichodesmium colonies are dead, using natural samples of coastal seawater, to observe the response capacity of natural communities in terms of increased productivity and changes in community structure (for example, impact on the microbial food web/microbial loop).

Objective 3

Make a balance on the fertilization impact throughout different years, depending on the proliferation of superficial Trichodesmium blooms, supposedly due to an increase in water temperature and/or stratification.