engleski

Centric diatoms response to nutrient limitation in Northern Adriatic

As a shallow basin and under the strong influence of freshwater input (Po river), Northern Adriatic (NA) is characterized by pronounced spatiotemporal changes of nutrient concentrations over the year with unbalanced N/P ratios and also it is phosphate-limited. This represents a challenge for the phytoplankton survival and imposes adaptation of individual life strategies which results in highly structured phytoplankton community through the basin. In situ measurements showed that activation of enzyme alkaline phosphatase helps phytoplankton species to overcome nutrient-limited conditions. Based on the long- term data (45-year monitoring programme) on diatom diversity and related nutrient measurements, several diatom species were chosen. We isolated them from the environment, cultured in opposite nutrient conditions (phosphorus enriched and phosphorus depleted) and observed their behavior and physiological adaptations. In this paper, we focused on centric diatoms as a very important class of diatoms in NA and showed data on growth rates, localization and activation patterns of alkaline phosphatase in laboratory conditions and also showed long term in situ data. The combination of laboratory experiment and in situ data play a key role in understanding species behavior under different environmental conditions. Our results imply species level adaptation to nutrient-limited conditions. Each diatom species developed different life strategy in order to compete for nutrients and find its’ own niche where it can thrive. This is of great importance to better understand and predict phytoplankton community structure in the ever-changing marine environment.

diatoms ; alkaline phosphatase ; northern Adriatic ; phosphorus limitation

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