Size-spectrum based differential response of phytoplankton to nutrient and iron-organic matter combinations in microcosm experiments in a Chilean Patagonian Fjord
The Patagonian fjords have been recognized as a major region of relatively high primary productivity systems during spring-summer bloom periods, where iron-organic matter forms may be essential complexes involved in key growth processes connected to the carbon and nitrogen cycles. We used two dissolved organic matter (DOM) types, marine polysaccharide and siderophore, as a model to understand how they affect the bioavailability of Fe to phytoplankton and bacteria and to assess their ecological role in fjord systems. A 10-day microcosm study was performed in the Comau Fjord during summer conditions (March 2012). Pico-, nano-, and microphytoplankton abundance, total chlorophyll-a and bacteria abundance, and bacterial secondary production estimates were analyzed in five treatments: (i) control (no additions), (ii) only nutrients (NUT: PO4, NO3, Si), (iii) nutrients + Fe(II), (iv) polysaccharide (natural diatoms extracted: 1-3 beta Glucan), and (v) Hexandentate Desferroxiamine B (DFB, siderophore). Our results showed that while DFB reduced Fe bioavailability for almost all phytoplankton assemblages in the fjord, polysaccharide did not have effects on the iron bioavailability. At Nutrients + Fe and Polysaccharide treatments, chlorophyll-a concentration abruptly increased from 0.9 to 20 mg m(-3) during the first 4-6 days of the experimental period. Remarkably, at the Nutrients + Fe treatment, the development of the bloom was accompanied by markedly high abundances of Synechococcus, picoeukaryotes, and autotrophic nanoflagellates within the first 4 days of the experiment. Our study indicated that small plankton (phytoplankton <20 mu m and bacteria) were the first to respond to dissolved Nutrients + Fe compared to large sized micro-phytoplankton cells (>20 mu m). This could be at least partially attributed to biological utilization of Fe (2 to 3 nM) by Fe dissolved fraction thus having a positive effect on the small-sized phytoplankton community.
|Título según WOS:||Size-spectrum based differential response of phytoplankton to nutrient and iron-organic matter combinations in microcosm experiments in a Chilean Patagonian Fjord|
|Título según SCOPUS:||Size-spectrum based differential response of phytoplankton to nutrient and iron-organic matter combinations in microcosm experiments in a Chilean Patagonian Fjord|
|Título de la Revista:||PHYCOLOGICAL RESEARCH|
|Fecha de publicación:||2014|
|Página de inicio:||136|