Spatio-temporal variability of micro-, nano- and pico-phytoplankton in the Mediterranean Sea from satellite ocean colour data of SeaWiFS
The seasonal and year-to-year variability of the phytoplankton size class (PSC) spatial distribution has been examined in the Mediterranean Sea by using the entire time series of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) space observations (1998–2010). Daily maps of PSCs have been determined u...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-09-01
|
| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/11/759/2015/os-11-759-2015.pdf |
| Summary: | The seasonal and year-to-year variability of the phytoplankton size class
(PSC) spatial distribution has been examined in the Mediterranean Sea by
using the entire time series of Sea-viewing Wide Field-of-view Sensor
(SeaWiFS) space observations (1998–2010). Daily maps of PSCs have been
determined using an empirical model based on a synoptic relationship between
surface chlorophyll <i>a</i> and diagnostic pigments referred to different
taxonomic groups. The analysis of micro-, nano- and pico-phytoplankton
satellite time series (1998–2010) describes, quantitatively, the algal
assemblage structure over the basin and reveals that the main contribution to
chlorophyll <i>a</i> in most of the Mediterranean Sea comes from the
pico-phytoplankton component, especially in nutrient-poor environments.
Regions with different and peculiar features are the Northwestern
Mediterranean Sea, the Alborán Sea and several coastal areas, such as the
North Adriatic Sea. In these areas, local interactions between physical and
biological components modulate the composition of the three phytoplankton
size classes. It results that, during the spring bloom season,
micro-phytoplankton dominates in areas of intense vertical winter mixing and
deep/intermediate water formation, while in coastal areas micro-phytoplankton
dominates in all seasons because of the nutrient supply from the terrestrial
inputs. In the Alborán Sea, where the Atlantic inflow modulates the
nutrient availability, any predominance of one class over the other two has
been observed. The nano-phytoplankton component instead remains widespread
over the entire basin along the year, and its contribution to chlorophyll <i>a</i>
is of the order of 30–40 %. The largest inter-annual signal occurs in
the Northwestern Mediterranean Sea, driven by the year-to-year variation in
intensity and extension of the spring bloom, followed by the Alborán Sea,
in which the inter-annual variability is strongly modulated by the Atlantic
inflow.
In absence of sufficient in situ data of community composition, the
satellite-based analysis demonstrated that pico-, nano- and micro-phytoplankton classes
often coexist. The predominance of one group over the other ones is strongly
dependent on the physical and biological processes occurring at the mesoscale. These
processes directly influence the nutrient and light availability, which are
the principal forcing for the algae growth. |
|---|---|
| ISSN: | 1812-0784 1812-0792 |