Methodology - Main activities
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 lead
s 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 present project will investigate the response of various components of the ecosystem to eutrophication and the consequently induced hypoxia. The consideration of different groups of organisms and biogeochemical processes, particularly at various spatial and temporal scales will serve to further shed light on different aspects of the problem. The consideration is required by the complexity of the project objectives since, as well says Duarte (2009) «an ecosystem approach to understanding and managing eutrophication requires that research be extended to include impacts beyond primary producers and to examine possible cascading effects and feedbacks involving other components of the ecosystem”. Furthermore, using four independent approaches (field sampling, large experiments, meta-analysis and modelling) allows the exploitation of benefits of each of them and overcome the limitations posed by others in some of the objectives of the study. Objectives
The HYPOXIA project aims at the study of the basic ecological processes of eutrophication which can lead to significant, irreversible within a short period of time, changes in marine ecosystems. In particular the project will investigate:
• The quantitative relationship between eutrophication in the water column and the hypoxia in the benthic domain.
• The changes in the structure of the communities of plankton (phyto-, zoo-, microbial) and the benthos (seagrass meadows, meiofaunal, macrofaunal and benthic microbial communities) during the progressive increase in eutrophication and the thresholds inducing regime shifts.
• The changes in the rates of ecosystem functions using as indicators the rates of organic matter mineralization (O2 consumption and consequent production of CO2, soluble N, P and H2S) in the surface layer of the sediment.
• The genetic structure of populations of opportunistic species and particularly the cluster of Capitella spp and the development of molecular markers (microsatellite and mitochondrial DNA) to detect possible demographic phenomena that might govern the populations of the species
Anticipated results
The idea of studying the coupling of pelagic and benthic ecosystems in the sense of the energy flow from the water column to the seabed and especially in the deep sea is quite old (see review in Graf 1992). However, the study of impact when approaching hypoxia levels in order to estimate the quantitative relationship between eutrophication in the water column and hypoxia in the underlying sediments has significant elements of originality particularly as it is designed to address the issue of regime shift and detection of thresholds which is a stimulating subject in marine research. Conducting the study at the oligotrophic eastern Mediterranean environment makes it even more interesting as it is expected much stronger (and therefore visible) change in environmental conditions than e.g. in cases of eutrophic sea masses as in the Black Sea or the Baltic. An additional element of innovation is the combination of very different modern approaches of pelagic and benthic ecology, microbial ecology, molecular techniques and mathematical modeling. The results are expected not only to have an important application e.g. in environmental policy to prevent irreversible changes in coastal marine ecosystems, but also to provide important information and global concern about specific aspects of the problem. Some of these aspects are the succession of microbial communities in the eutrophication gradient (column) and hypoxia (sediment) and their match with the patterns of the respective phyto-, zooplankton and benthic macrofaunal communities. Also very important results are expected from the study of the variability in the complex of Capitella spp in relation to environmental variability in the benthic habitat. The species of this complex are expected to have developed special adaptations to be able to respond to extreme environmental conditions in which they live (pollution, hypoxia). Changes in gene level that provide increased adaptability of species to their environment will be the subject of this part of the study. This is an exciting subject with international interest which connects the ecology of an organism with its genes. Benefit from the implementation of the project
Our study will address an environmental issue which is of significant interest to the society, particularly in the context of coastal zone management and the regulation of the various uses of the marine environment. The results will be used in the SHoCMed project of the EU/GFCM and the «WG on Site selection and Carrying Capacity” of the GFCM/CAQ) both addressing the issue of aquaculture regulation in the coastal zone. A series of important papers in the prime scientific literature are expected ranging from microbial communities to seagrasses comprising both field studies and large experiments. The results and the experimental facilities will be also used for the training of undergraduate students of the Biology Department, the visiting ERASMUS students and the postgraduate students of the MSc Programme in “Environmental Biology” organized by the UoC Biology Department, the HCMR and the Natural History Museum in Crete. Although no direct financial benefits are expected, the societal, scientific and educational benefits are significant. Furthermore, it is anticipated that the project will allow the establishment of a group of excellence on this issue which will be able to collaborate with other complementary groups in joint EU projects. Progress beyond the state of the art
Since the recovery of ecosystems after anoxic crises is slow and difficult, the adoption of safe Environmental Quality Standards (ESQs) is necessary for the maintenance of the goods and services provided by costal ecosystems. HYPOXIA research project has been designed to answer a series of questions such as:
• Description of the plankton system dynamics under different levels of nutrient addition.
• Developing a mesocosms methodology suitable for the experimental study of benthic-pelagic coupling
• Dynamics of the benthic system and subsystems response to gradients of dissolved oxygen (DO) concentration until the hypoxia levels
• Eutrophication impacts on seagrasses: comparison of estimates resulting from different study methods.
• Meta-analysis results: differences in biogeochemical variables among areas, seasons and discharge types.
• Benthic indicators for the EU Water Framework Directive (WFD): sensitivity along the DO gradient and calibration of the corresponding values among each other and with the geochemical variables
• Relationship between remote sensing and field values for the detection of eutrophication: use of past time series for risk assessment.
• Structure and ecological preferences of different species-members of the Capitella complex. Do they coexist or they occupy different segments of the eutrophication gradient? How strong is the selection pressure that caused their separation? Are they all present in all types of pollution/disturbance or is there a clear separation of preferences; How much do they differ and how are they are classified in terms of “opportunisticity”?
• Structure of the bacterial communities: is there redundancy or clear changes regarding their abundance and diversity? How is this structure related to the corresponding structure of the metazoan communities?
• Hypoxia impacts on ecosystem biogeochemical functions
• Mathematical modelling of the dose/response relations for the main variables of the pelagic and benthic systems.
• The mathematical modelling and the experimental studies will be an important step forward for the understanding of basic ecological mechanisms of the eutrophication processes that may induce significant non reversible (in a small time scale) changes to marine ecosystems.
