The Ross Sea and its primary producers

The Ross Sea is one of the most productive areas in the Antarctic Ocean, being an area characterized by a high seasonal and regional variety of primary production and carbon export processes through the water column. These seasonal variations are linked to the formation and melting of the sea ice and the variation in the dynamics of the water column.

These variables may change, for example, the introduction of freshwater by melting sea ice has been recognized as the main driver in the decrease in the dynamism of the water column during the spring-summer seasons. These and other changes can have significant effects on phytoplankton communities [1], communities that play an important role in biogeochemical processes [2] in the ocean.

One of the most important types of phytoplankton in the Antarctic region is the Diatoms, which contribute 75% of primary production in the Antarctic Ocean and support many of the food webs [3] in the region. Within the Diatoms, there are 2 main groups, the pennants and the centrists, these groups present differences in body shape among others thinks. As such, the researchers of this study aimed to describe the distribution of different groups of diatoms in the Ross Sea. For this, they carried out 2 oceanographic cruises during the austral summer of 2014 and 2017.

In 2014 and 2017, the surface distribution of diatoms was dominated in both summers by pennate diatoms (Fragilariopsis and Pseudo-nitzschia), but a temporal variation was analysed, where there was a change in the community, mainly dominated by pennate diatoms to dominated by centric diatoms, in February 2014 and 2017.

In general, the phytoplankton communities were very similar between cruises. However, the concentrations reached were different (Fig.1). A change in the concentrations of groups of Diatoms in surface water agrees with the observation of other authors.

Fig. 1. Spatial and temporal distribution of the most abundant diatom genera estimated from samples collected at the surface of the water column. The histograms represent the concentrations of diatoms in the stations RoME I, RoME II and RoME III, in 2014, and in the stations TNB, AMG, Central Rose Sea (Central) and Cape Adare (Adare), in 2017. The circles represent the contribution percentage of pennate and centric diatoms to the total diatom abundance in each station.

This study was the first description of the diversity of Diatom groups in the Ross Sea, as expected changes in environmental variables affect the distribution of phytoplankton in the water column. The dynamics of the trophic network of the polar regions depend exclusively on the phytoplankton community and its changes, changes that can have effects on the biogeochemical cycles, the authors highlight the lack of studies on this subject and the importance of carrying out more studies to know these communities and its variations.

Smaller organisms are also crucial for balance of our ecosystems!

[1] Phytoplankton: Group of microscopic aquatic organisms that can perform photosynthesis and that live floating along the water column.

[2] Biogeochemical processes: Also known as the cycle of matter, it is therefore the process of passing from the environment (physical-chemical components) to living organisms and from these back to the environment.
[3] Trophic network: Interconnection within an ecosystem of matter and energy transfers between organisms.

Source: Saggiomo, M., Escalera, L., Bolinesi, F., Rivaro, P., Saggiomo, V., & Mangoni, O. (2021). Diatom diversity during two austral summers in the Ross Sea (Antarctica). Marine Micropaleontology, 165.

Author: Graça Sofia Nunes


Leave a Reply