Relationships Between Aquatic Protists and Humans

Abstract

Protists exhibit a tremendously wide variety of lifestyles and metabolic functions. Considering predicted shortages of natural resources and foods in the near future, much more attention has to be paid to these potentialities of protists from applied and industrial points of view. We provide a general overview of their potentialities, some of which have already been industrialized. On the other hand, our health and economics have long been damaged by other potentialities of protists such as harmful algal blooms and paralytic shellfi sh poisoning . We have been intensively searching for effective countermeasures to avoid or reduce these detrimental impacts. Wise use of protistan benefi cial potentialities is a key issue to respond adequately to rapidly and drastically ongoing changes of global environments. In addition we have to exactly consider what is now happening to the protistan communities due to anthropogenic impact s.

Punctuated Sediment Discharge During Early Pliocene Birth of the Colorado River: Evidence from Regional Stratigraphy, Sedimentology, and Paleontology

“…The Streptochilus biofacies suggests a further increase in water depth (Table 2): the foraminiferal assemblage is similar to that found in the Elphidium and Rosalina biofacies except for the change in dominance to Streptochilus. Streptochilus is an opportunistic planktic foraminifer that appears in shallow surface water (75-150 m) in tropical to subtropical coastal regions where fluctuating nutrient-richwater is upwelled resulting in relatively eutrophic conditions (Resig and Kroopnick, 1983;Hemleben et al, 1989;Nikolaev et al, 1998;Thomas, 2006, 2007;Ohtsuka et al, 2015;Schiebel and Hemleben, 2005). The absence of new species in this biofacies despite increased water depths suggests that the connection to the proto-Gulf of California may have been restricted.…”

In situ imaging reveals the biomass of giant protists in the global ocean

“…Most rhizarians produce mineral skeletons of calcium carbonate (Foraminifera) or silicate (polycystine radiolarians) that are often well preserved in marine sediments, making this group a focus for the development of paleoproxies 12 . Others, such as Phaeodaria, Collodaria and Acantharia, possess more delicate skeletons and are not preserved in marine sediment records 12,13 . A number of studies, ranging from sediment trap to environmental molecular surveys [15][16][17] , have suggested that the Rhizaria are important for present-day oceanic ecosystems.…”

“…However, unlike crustacean plankton, which can be easily collected, delicate rhizarians are severely damaged by plankton nets, and other rhizarians, such as Acantharia, eventually dissolve upon preservation in regular fixatives (for example, formalin). Rhizaria are therefore inconsistently sampled 13,14,20,21 and their global distribution and role in the ecosystem are not well understood. Although they are known to be abundant in specific areas of the oceans 14,20,22 , their contribution to plankton communities has never been assessed on a global scale.…”

“…3b). Considering that all Collodaria and most Acantharia investigated so far harbour symbiotic microalgae 13,14,24 , we estimated that these groups typically contribute 0.18% (0.17% for Collodaria and 0.01% for Acantharia) of total primary production in oligotrophic waters (Extended Data Table 4). Only one study, performed in the oligotrophic Sargasso Sea, has estimated the contribution of Rhizaria to total primary production; this study showed that large photosymbiotic Rhizaria could account for 0.1-0.4% of total primary production 25 .…”

“…(iv) Primary production of photosymbiotic rhizarians was estimated individually for all Acantharia and Collodaria observed between 0 and 500 m depth. While all collodarian species investigated have been described as photosymbiotic 13,14 , the vast majority of large acantharian specimens found in the upper water column are known to harbour symbionts 24,25 .…”