Several studies have already been carried out to characterize heterotrophic bacteria and phytoplankton communities in ocean sites and in different coastal areas of temperate, tropical and polar zones. Mar Piccolo of Taranto (Ionian Sea) is a semi-enclosed basin subject to pollution and receives a considerable amount of sewage and industrial waste. The aims of this work was to analyse the qualitative and quantitative composition of heterotrophic bacteria and phytoplankton communities and the interactions between these two planktonic components. Samples of sea-water were collected monthly from September 2006 to August 2007 in two stations of the Mar Piccolo at the surface and bottom layers. Among the Gram-negative bacteria, the predominant genus were Aeromonas, Photobacterium e Pseudomonas. Gram-positive bacilli were abundant at all sampling points. Among pigmented bacteria, Flavobacterium was predominant. As regards phytoplankton communities, quantitative data evidenced high abundance values in the spring time and they were characterized by the dominance of diatom and phytoflagellate groups. Dinoflagellates and coccolithophorids accounted only for low percentage values. During the sampling period, diatoms were dominant with high cell densities in the spring and were mainly represented by Pseudo-nitzschia spp., Chaetoceros spp., Cylindrotheca closterium, and Thalassiosira sp. Indeed, phytoflagellates, mainly represented by the undetermined forms < 10 ?m and by cryptophyceans, had a wider distribution over time. As regards the interactions between bacteria and phytoplankton, our data must be considered preliminary, but they seemed to evidence that phytoplanktonic spring bloom could be probably responsible for the availability of organic matter for bacterial populations. But, further studies will evaluate whether the balance in time between the positive dissolved factors (nutrients from phytoplankton bloom) and the negative particulate factors (grazing) could be considered to be a major determinant of the temporal fluctuations of bacterial density in Mar Piccolo.
Relazioni tra batteri eterotrofi e fitoplancton nel Mar Piccolo di Taranto
Cavallo RA;Acquaviva MI;Narracci M;Stabili L;Caroppo C
2007
Abstract
Several studies have already been carried out to characterize heterotrophic bacteria and phytoplankton communities in ocean sites and in different coastal areas of temperate, tropical and polar zones. Mar Piccolo of Taranto (Ionian Sea) is a semi-enclosed basin subject to pollution and receives a considerable amount of sewage and industrial waste. The aims of this work was to analyse the qualitative and quantitative composition of heterotrophic bacteria and phytoplankton communities and the interactions between these two planktonic components. Samples of sea-water were collected monthly from September 2006 to August 2007 in two stations of the Mar Piccolo at the surface and bottom layers. Among the Gram-negative bacteria, the predominant genus were Aeromonas, Photobacterium e Pseudomonas. Gram-positive bacilli were abundant at all sampling points. Among pigmented bacteria, Flavobacterium was predominant. As regards phytoplankton communities, quantitative data evidenced high abundance values in the spring time and they were characterized by the dominance of diatom and phytoflagellate groups. Dinoflagellates and coccolithophorids accounted only for low percentage values. During the sampling period, diatoms were dominant with high cell densities in the spring and were mainly represented by Pseudo-nitzschia spp., Chaetoceros spp., Cylindrotheca closterium, and Thalassiosira sp. Indeed, phytoflagellates, mainly represented by the undetermined forms < 10 ?m and by cryptophyceans, had a wider distribution over time. As regards the interactions between bacteria and phytoplankton, our data must be considered preliminary, but they seemed to evidence that phytoplanktonic spring bloom could be probably responsible for the availability of organic matter for bacterial populations. But, further studies will evaluate whether the balance in time between the positive dissolved factors (nutrients from phytoplankton bloom) and the negative particulate factors (grazing) could be considered to be a major determinant of the temporal fluctuations of bacterial density in Mar Piccolo.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
