Stream integrity in oceanic islands – a functional approach using organic matter decomposition

State
ONGOING
Name
Ana Balibrea Escobar
Entity host
CIBIO, Research Center in Biodiversity and Genetic Resources, InBIO Associate Laboratory

BIOPOLIS Program in Genomics, Biodiversity and Land Planning

UNESCO Chair-Land Within Sea: Biodiversity & Sustainability in Atlantic Islands, University of the Azores
University awarding the degree
University of the Azores

Science Networks
Research Gate

ORCID

Objective

Human activities and changes in land use potentially impact stream ecosystems, but official evaluations of stream ecological integrity rely only on the assessment of structural indicators, while functional indicators are not considered. This is despite the recognition by the WFD that “ecological status is an expression of the quality of the structure and functioning of aquatic ecosystems”, and that ecosystem functioning is tightly related with ecosystem services. Decomposition of organic matter has been proposed as a suitable functional indicator of stream functional integrity, and multiple European projects have been dedicated to this topic. Oceanic islands are far less economically developed than mainland member states as a direct result of their remoteness, isolation and insular nature. Moreover, investigation on oceanic islands is scarce, but needed given that islands differ from mainland in multiple factors that can affect the litter decomposition, such as low diversity of invertebrates and naturally challenging water characteristics (e.g. high heavy metal concentrations).

The main goal of this project is to assess the use of organic matter decomposition as a potential indicator of stream ecosystem functioning in the Azores archipelago. The specific objectives of this project are:

to evaluate organic matter decomposition as a possible indicator of stream ecosystem functioning and to compare its performance with that of structural indicators in streams included in the regional bioassessment program;
to test the use of organic matter decomposition as an indicator in streams under riparian forest modifications for agricultural and livestock uses in comparison with non-impacted streams;
to assess organic matter decomposition in streams naturally enriched with heavy metals from volcanic activity but not affected by human activities to establish reference conditions for this particular stream type; and
test the effects of heavy metals concentrations on litter decomposition and on biological communities associated to this process.

Results & Impact

Human activities, such as intensive agriculture and pasture, may impact negatively on freshwater systems and deteriorate water quality. Traditionally, biomonitoring programs to assess stream ecological integrity are based on structural parameters (macroinvertebrates, diatoms, macrophytes and fish communities). However, since stream ecological integrity depends on both structural and functional integrity, evaluation of stream functional parameters has been suggested as a complementary approach in stream bioassessment to allow a more complete assessment of stream ecological integrity. Given the strong dependence of stream ecosystems on allochthonous organic matter resources, which constitute the primary source of energy and matter for stream food webs, decomposition of organic matter has been proposed as a suitable indicator of stream functional integrity. During the last two decades, organic matter decomposition has been extensively addressed as an indicator of stream functional integrity, but studies on oceanic islands are non-existing despite fundamental differences between oceanic islands streams and their continental counterparts. The main goal of this project is to assess the use of organic matter decomposition as a potential indicator of stream functional integrity in the Azores archipelago, where intensive agriculture and pasture activities pose serious threats to stream ecological integrity and ecosystem services.

This project will contribute to fill in the knowledge gap regarding the use of organic matter decomposition as an indicator of stream functional integrity in the species-poor ecosystems characteristic of oceanic islands. The project will be carried out in conjugation with the Azorean Inland Waters Monitoring Program (Concurso público No 18/DRA/2019), which is undertaken by the research team of the CIBIO-Açores. The connection of this projects will allow an assessment of both structural and functional stream integrity in the stream network considered in the official bioassessment program and facilitates communication of results on the effectiveness of organic matter decomposition as an indicator of stream functional integrity to the official entities.