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Identifier

000419785

Title

Μεγάλης κλίμακας επιπτώσεις ανθρωπογενών δραστηριοτήτων στο βενθικό οικοσύστημα : επανεξέταση των βενθικών κοινοτήτων 20 χρόνια μετά

Alternative Title

Long-term effects of human activities on the benthic ecosystem: revisiting sampling sites after 20 years

Author

Τσικοπούλου, Ειρήνη

Thesis advisor

Καρακάσης, Ιωάννης

Reviewer

Αρβανιτίδης, Χρήστος
Τσαπάκης, Μανώλης
Λαδουκάκης, Εμμανουήλ
Λύκα, Κωνσταντίνα
Smith, Christopher J.

Abstract

Long-term ecological studies are considered fundamental for understanding complex ecological dynamics and global change effects and also enhance many aspects of conservation practice and policy. Although long-term time series monitoring benthic ecosystem are rare, long-term comparisons with historical data can be efficiently used to infer temporal changes in diversity and community composition. In this context, three different benthic macrofaunal communities were studied in a period of about 20-25 years long. Identical sampling design, season, techniques and protocols were followed in both studies in order to minimize bias in the long-term comparisons. The first case concerned the indirect effects of aquaculture on the benthic ecosystem in a semi-closed bay (Cephalonia, Ionian Sea) where a relatively large fish farm has been operating since 1982. The environmental impacts of fish farming on benthic ecosystems beneath the fish cages have been widely addressed the past decades. However, the chronic release of nutrients can cause a shift in local primary productivity and a chronic increase in the sedimentation of organic material at a large spatial scale which could be reflected in benthic ecosystems. Results from the recent samplings (2014 and 2015) were compared to historical data obtained in 1996 and 2001, in order to detect if nutrient release that could impact phytoplankton dynamics in the bay could indirectly alter benthic communities, as well. Macrofaunal communities have not shown deterioration but rather a small, yet statistically significant, improvement in diversity indices and ecological status indicators, and no significant change regarding bioturbation potential. This indicated that processes involved in nutrient consumption and transfer are highly effective in such an oligotrophic environment. In the next case, changes in the benthic community on a traditional fishing ground in the eastern Mediterranean were addressed after an 18-years period. An improvement in diversity metrics and ecological quality status were detected and according to local fishermen ascribed to the Greek economic crisis. Specifically, there was a modest increase in species richness, total abundance and ecological status in the unaffected zone and more pronounced improvement in the trawled zone pointing at a possible link to a decrease in fishing effort. This upturn emphasized the strong link between financial activities and ecology. The present study underlines the multiple and variable effects of economy not only on countries and citizens but also on the environment and ecosystem conservation and management. Finally, a bathymetric transect in the north coast of Crete first studied in 1989, has been revisited 24 years later. This comprehensive macrofaunal dataset revealed changes in benthic diversity and community composition between the sampling periods. The recorded changes were higher at the stations located close to the coastal zone. Nevertheless, the ecological status remained stable and above the threshold values for good ecological status. The latest results indicated that changes in the benthic community seem to have been driven by local anthropogenic factors and stochasticity and less by large-scale factors such as climate change and nutrients influxes in the entire Mediterranean Basin.

Language

Greek

Subject

Aquaculture trawling

Benthic ecology

Ecological quality status

Long-term study

Macrofauna

Natural variability

Βενθική αλιεία

Βενθική οικολογία

Μακροπανίδα