Phytoplankton of Bransfield Strait and Elephant Island during austral summer 2007

Abstract

The distribution and structure of the phytoplankton community in Bransfield Strait and Elephant Island were studied during Austral Summer of 2007. The seawater samples were collected using a Niskin bottle at different depths. The quantitative analysis was performed by the Utermöhl sedimentation method. 76 species of microalgae were identified in the water column of Bransfield Strait: 53 diatoms, 18 dinoflagellates and 5 microflagellates. In terms of abundance, the most representative groups were microflagellates (76%), diatoms (21%) and dinoflagellates (3%). The dominant species were Leucocryptos marina, Thalassiosira antarctica, Pseudonitzschia pseudodelicatissima, Pseudonitzschia seriata y Pronoctiluca pelagica. The highest abundance levels of diatoms were recorded surrounding Elephant Island and associated with temperatures >1 °C and salinities values <34.2 ups, while the largest abundance of microflagellates was recorded nearby South Shetland and Elephant islands. The poorest area in phytoplankton was determined in the vicinity of the Antarctic Peninsula. Vertically, the greatest densities of phytoplankton were located above 50 m. The diversity index was low, less than 2.4 bits/cel while the similarity among samples high, more than 60%. On a small scale there was no a marked temporal variation of phytoplankton.