Exploring Tiny Sea Life in the Sparse South Pacific Waters

Greg Howard
8th March, 2024

Exploring Tiny Sea Life in the Sparse South Pacific Waters

Image Source: Natural Science News, 2024

Key Findings

  • Study in South Pacific Gyre found diverse ocean microorganisms, including overlooked fungi and protists
  • Parasitic protists, mainly Syndiniales, were abundant and varied with ocean depth
  • These microorganisms likely have a big role in the ocean's nutrient and carbon cycles
Microorganisms in the ocean are more than just tiny specks in the water; they are powerhouses that drive the planet's life-support systems. They make up around 70% of marine biomass and are responsible for half of the Earth's primary production, which is the creation of organic compounds from carbon dioxide through photosynthesis. These processes are crucial for the global cycling of nutrients and carbon—elements fundamental to life on Earth. However, not all microorganisms have been given equal attention in research, especially those in the vast and nutrient-poor South Pacific Gyre (SPG). The Ruđer Bošković Institute has conducted a study[1] that sheds light on the overlooked members of the ocean's microbiome: heterotrophic and mixotrophic protists—organisms that obtain nutrients from other organisms and through photosynthesis—and fungi. This research is significant as it delves into the diversity and distribution of these microorganisms in the SPG, the largest subtropical gyre, which is characterized by its low nutrient content. The study found notable differences in the diversity of protistan communities between the sunlit (photic) and dark (aphotic) regions of the ocean. Factors like temperature, salinity, oxygen, and nutrient concentrations significantly influenced the diversity of the entire protistan community. Interestingly, the diversity of parasitic protists was also affected by the concentration of chlorophyll a, a pigment associated with photosynthesis. A striking discovery was the dominance of parasitic protists belonging to the class Syndiniales, which made up over 98% of the total parasitic protists. These organisms showed a higher relative sequence abundance as one moved deeper into the ocean and exhibited consistent patterns across different sampling locations. This aligns with previous findings that highlighted the importance and ubiquity of Syndiniales in oceanic systems[2]. In contrast to the protistan community, the fungal community in the SPG was more influenced by the location of the sampling station and by the different zones of the pelagic (open ocean) environment. Earlier studies have shown that fungi such as Penicillium species play a role in carbon and nitrogen cycling in marine sediments[3]. The current study expands on this by revealing a significant presence of functionally diverse fungi in the SPG's water column. These findings are crucial because they suggest that parasitic protists and fungi in the SPG could have a substantial impact on the marine food web, particularly in the cycling of organic matter[4]. This impact is significant in the SPG's oligotrophic (nutrient-poor) environment, where every bit of nutrient cycling is vital to sustaining life. Moreover, this study's insights into the protistan and fungal communities in the SPG are valuable for understanding how these microorganisms contribute to the dynamics of the food webs in the world's oceans. This is especially pertinent as we face future climate change, which could alter the temperature and nutrient profiles of marine environments, potentially affecting the roles these microorganisms play. The research from the Ruđer Bošković Institute not only fills in gaps in our knowledge about the microorganisms in the SPG but also highlights the intricate connections between different species and their environments. It underscores the fact that even the smallest organisms can have a profound impact on global processes. As we continue to explore the complexities of the ocean's microbiome, studies like this one are essential for piecing together the puzzle of how life in the ocean functions and how it might respond to the challenges of a changing world.

EcologyMarine BiologyMycology


Main Study

1) Insight into planktonic protistan and fungal communities across the nutrient-depleted environment of the South Pacific Subtropical Gyre.

Published 5th March, 2024


Related Studies

2) Beyond the limits of the unassigned protist microbiome: inferring large-scale spatio-temporal patterns of Syndiniales marine parasites.


3) Genome characterization of two novel deep-sea sediment fungi, Penicillium pacificagyrus sp. nov. and Penicillium pacificasedimenti sp. nov., from South Pacific Gyre subseafloor sediments, highlights survivability.


4) The largely neglected ecological role of oceanic pelagic fungi.


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