HYPOXIA Objectives

Eutrophication, and the consequently induced hypoxia, evoke major economic, ecological and ecosystem functioning, consequences in coastal marine ecosystems. Increased primary production, caused mostly by the runoff of fertilizers and the burning of fossil fuels, is one of the most prominent characteristics of a hypoxic area. Subsequently, high primary production leads to accumulation of dissolved and particulate organic matter which triggers high microbial activity and, thus, consumption of dissolved oxygen in the bottom water.

These changes in the concentration of oxygen and organic matter are primarily reflected in the microbial communities. The structure of the microbial communities changes, while microbial metabolism shifts from aerobic to anaerobic respiration. Such changes in the metabolic pathways of the microorganisms can affect further the ecosystem by enriching it with products of anaerobic respiration that can be toxic for other benthic organisms. Thus, the energy flow is modified from a complex food web including higher trophic levels to a reduced food complexity consisting only of lower (microbial) trophic levels.

The HYPOXIA project includes a multi-disciplinary investigation of the problem of eutrophication and the induced hypoxia, in coastal marine ecosystems to the point where irreversible changes (regime shifts) are induced. The project includes the meta-analysis of historical data in areas with increased nutrient discharge, field sampling (in areas with eutrophication symptoms) and mesocosm experiments (with induced eutrophication) to investigate the dynamics of the benthic- pelagic coupling in the marine ecosystem in a system of increased nutrient availability and / or increased supply of organic material.

The project will involve:

  1. Study the impact on benthos and in particular the change in thevalues of environmental quality indicators depending on the amount of the sedimentation fluxes of organic material, the effects of hypoxia on biogeochemical processes in the sediment, the structure and diversity of benthic microbial communities (using molecular techniques such as analysis of 16sRNA), on the metabolism and recycling of C, N and P in seagrass meadows, and the response of the opportunistic species, especially the Capitella spp complex depending on the characteristics of the system.

  2. Study the dynamics of theplankton and microbial system using inverse microscopy, flow cytometry and molecular techniques (DDGE, metagenomics analysis of microbial communities) to identify which organisms benefit from the nutrient discharge and what succession pattern appears depending on the quantity of input and the environmental characteristics of the system

  3. Statistical meta-analysis of historical data and use of mathematical models to extract quantitative relationships between nutrient input and the response of different components of the marine ecosystem.

In particular will be studied:

  • The quantitative relationship between eutrophication in the water column to benthic hypoxia.

  • The shift of planktonic (phyto-, zoo-, microbial) and benthic (marine phanerogams, macrofauna and benthic microbial communities) communities, during a progressive eutrophication and the limits that induce a regime change.

  • Changes of ecosystem processes rates using as an indicator the rate of mineralization of organic material (oxygen consumption) in the surface sediment layer.

  • The genetic structure of populations of opportunistic species, especially the Capitellaspp complex and the development of molecular markers (microsatellites and mitochondrial DNA) to detect possible demographic phenomena that are likely to govern the populations of the species.