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Bioavailability of dissolved organic matter in marine systems

Lønborg C 1,2 & Álvarez–Salgado X.A2

1Scottish Association for Marine Science, Dunstaffnage Marine Laboratory Oban, Argyll, PA37 1QA, United Kingdom

2CSIC, Insituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain

The bioavailability and bacterial degradation of dissolved organic matter (DOM) were determined from the oligotrophic surface open ocean to highly productive coastal waters.  A total of 1629 bioavailability observations for DOC, 749 for DON and 381 for DOP were collected from different databases and published articles.  DOC concentrations varied between 38 and 514 µmol L–1, 23 ± 12% (average ± SD) of which was bioavailable (BDOC). DON ranged from 4.4 to 36.4 µmol L–1 and the bioavailable fraction (BDON) represented 39 ± 16% of DON. Finally, the concentrations of DOP varied from 0.06 to 0.52 µmol L–1, 64 ± 26% of which was bioavailable (BDOP). Bioavailability increased in the sequence DOP > DON > DOC in all systems in agreement with the decreasing lability of phytogenic phosphorus compounds, proteins, carbohydrates and lipids. Positive linear relationships were found in all systems between dissolved organic matter (DOM) and bioavailable DOM (BDOM), with regression slopes not significantly different from 1:1, suggesting that BDOM controls the variations of DOM concentrations in all types of marine systems.

What structures fish communities in the South Aegean: fishing or habitat?

Longo C1,2 , Pierce G J1, Peristeraki P2 & Tserpes G2

1School of Biological Sciences (Zoology), University of Aberdeen, Aberdeen, UK

2Fisheries Department, Hellenic Centre for Marine Research (HCMR), Crete, Greece

Fishing has altered community properties such as size-structure and mean trophic level in marine ecosystems worldwide. Presently, Mediterranean ecosystems are also witnessing changes in species distributions due to increased temperatures coupled with the introduction of tropical species through the Suez Canal and ballast waters. Thus, the community structure of Mediterranean fish is rapidly changing under the pressure

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