An official website of the United States government
Diatoms are key primary producers across marine, freshwater, and terrestrial ecosystems. They are responsible for photosynthesis and secondary production that, in part, support complex food webs. Diatoms can produce phytochemicals that have transtrophic ecological effects which increase their competitive fitness. Polyunsaturated aldehydes (PUAs) are one class of diatom-derived phytochemicals that are known to have allelopathic and anti-herbivory properties. The anti-herbivory capability of PUAs results from their negative effect on grazer fecundity. Since their discovery, research has focused on their production by pelagic marine diatoms, and their effects on copepod egg production, hatching success, and juvenile survival and development. Few investigations have explored PUA production by the prolific suite of benthic marine diatoms, despite their importance to coastal trophic systems. In this study, we tested eight species of benthic diatoms for the production of the bioactive PUAs 2,4-heptadienal, 2,4-octadienal, and 2,4-decadienal. Benthic diatom species were isolated from the Salish Sea, an inland sea within the North Pacific ecosystem. All species were found to be producers of at least two PUAs in detectable concentrations, with five species producing all three PUAs in quantifiable concentrations. Our results indicate that production of PUAs from Salish Sea benthic diatoms may be widespread, and thus these compounds may contribute to benthic coastal food web dynamics through heretofore unrecognized pathways. Future studies should expand the geographic scope of investigations into benthic diatom PUA production and explore the effects of benthic diatoms on benthic consumer fecundity.
more »
« less
This content will become publicly available on July 10, 2026
Inorganic carbon enrichment does not increase production of polyunsaturated aldehydes in a pelagic and benthic diatom.
Seasonal upwelling in coastal environments supports high primary production by increasing concentrations of inorganic nutrients in the euphotic zone. Diatoms typically dominate planktonic primary production and community composition during seasonal upwelling, especially in temperate ecosystems. Some diatoms elevate their competitive fitness by producing polyunsaturated aldehydes (PUAs). These phytochemicals act to reduce the fecundity of their grazers by reducing sperm motility, lowering egg production and viability, and delaying embryo development, reducing diatom consumptive pressure. While research into the mechanisms driving PUA production includes bottom-up factors (i.e., nutrient availability), few studies have explored how dissolved carbon dioxide (pCO2) concentration affects PUA production. In this study, we analyzed the production of bioactive PUAs (2,4-heptadienal, 2,4-octadienal, and 2,4-decadienal) in two diatom species found in the Salish Sea, an inland sea of the North Pacific ecosystem, under varying pCO2 concentrations that are experienced during seasonal upwelling events. We found that elevated pCO2 concentration caused an increase in carbon uptake in the diatoms, but did not lead to more PUA production, and at times caused a decrease in production. Our results suggest that carbon enrichment does not elevate the chemically defensive capabilities of diatoms by way of elevated PUA production.
more »
« less
- Award ID(s):
- 2342375
- PAR ID:
- 10638823
- Publisher / Repository:
- PLoS Journals
- Date Published:
- Journal Name:
- PloS one
- ISSN:
- 1932-6203
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Diatom-dominated blooms in coastal upwelling systems contribute disproportionately to global primary production. The fate of carbon captured during a diatom bloom is often influenced by species-specific ecological differences. However, successional patterns that take place during a diatom bloom are often oversimplified, and the diversity of diatom adaptations to different stages of a bloom remains poorly characterized. To improve our understanding of diatom specificity to certain conditions within a bloom, we employed microscopy, 18S rRNA amplicons, and biogeochemical analysis within a simulated upwelling mesocosm experiment. We successfully simulated a diatom bloom and found that diatoms bloomed during early and late phases of the bloom. Surprisingly, the relative abundance of congeneric diatoms with the Thalassiosira, Chaetoceros, and Pseudonitzschia displayed opposing patterns that were consistent among experimental mesocosms. The late stage of the bloom was especially interesting because some diatoms continued to bloom among mixotrophic dinoflagellate genera Akashiwo, Heterocapsa, and Prorocentrum. Additionally, Syndiniales putative parasites were correlated with several diatoms, especially in the initial phase of the bloom. The novel observations of consistent rapid successional changes within our mesocosms reflect the ability of diatom and dinoflagellate genera to occupy bloom conditions that fall outside traditional expectations. Syndiniales parasite co-occurrence with blooming diatoms may be important to successional trends of coastal diatom populations, and this parasitic interaction deserves further study in coastal upwelling systems. This study indicates there are underlying diatom traits and biotic interactions that should be considered when estimating their contribution to productivity and carbon cycling within upwelling systems.more » « less
-
Diatoms are major contributors to marine primary productivity and carbon export due to their rapid growth in high-nutrient environments and their heavy silica ballast. Their contributions are highly modified in high-nutrient low-chlorophyll regions due to the decoupling of upper-ocean silicon and carbon cycling caused by low iron (Fe). The Si cycle and the role of diatoms in the biological carbon pump was examined at Ocean Station Papa (OSP) in the HNLC region of the northeastern subarctic Pacific during the NASA EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field study. Sampling occurred during the annual minimum in surface silicic acid (Si(OH)4) concentration. Biogenic silica (bSi) concentrations were low, being in the tens of nanomolar range, despite high Si(OH)4 concentrations of about 15 μM. On average, the >5.0-µm particle size fraction dominated Si dynamics, accounting for 65% of bSi stocks and 81% of Si uptake compared to the small fraction (0.6–5.0 μm). Limitation of Si uptake was detected in the small, but not the large, size fraction. Growth rate in small diatoms was limited by Fe, while their Si uptake was restricted by Si(OH)4 concentration, whereas larger diatoms were only growth-limited by Fe. About a third of bSi production was exported out of the upper 100 m. The contribution of diatoms to carbon export (9–13%) was about twice their contribution to primary productivity (3–7%). The combination of low bSi production, low diatom primary productivity and high bSi export efficiency at OSP was more similar to the dynamics in the subtropical gyres than to other high-nutrient low-chlorophyll regions.more » « less
-
The contribution of diatoms to the production and export of organic carbon is highly modified in high-nutrient low-chlorophyll (HNLC) regions due to the decoupling of upper-ocean silicon and carbon cycling caused by low iron. The Si cycle and the role of diatoms in the biological carbon pump was examined at Ocean Station Papa (OSP) in the HNLC region of the northeastern subarctic Pacific during the NASA EX port Processes in the Ocean from RemoTe Sensing (EXPORTS) field study. Sampling occurred during the annual minimum in surface silicic acid concentration, [Si(OH)4 ]. Biogenic silica (bSi) concentrations were low being in the tens of nanomolar range despite high [Si(OH) 4 ], ~15 μM. On average the > 5.0 μm particle size fraction dominated Si dynamics accounting for 65% of bSi stocks and 81% of Si uptake compared to the small fraction (0.6 - 5.0 μm). Limitation of Si uptake was detected in the small, but not the large, size fraction. Small diatoms were co-limited with growth rate restricted by Fe and Si uptake restricted by [Si(OH) 4 ], whereas larger diatoms were only growth limited by Fe. About a third of silica production was exported out of the upper 100 m. The contribution of diatoms to carbon export (9 - 13%) was about twice their contribution to primary productivity (3 - 7%). The combination of low silica production, low diatom primary productivity and high bSi export efficiency at OSP was more similar to the dynamics in the subtropical gyres than to other HNLC regions.more » « less
-
null (Ed.)Synopsis Intense bottom-ice algal blooms, often dominated by diatoms, are an important source of food for grazers, organic matter for export during sea ice melt, and dissolved organic carbon. Sea-ice diatoms have a number of adaptations, including accumulation of compatible solutes, that allows them to inhabit this highly variable environment characterized by extremes in temperature, salinity, and light. In addition to protecting them from extreme conditions, these compounds present a labile, nutrient-rich source of organic matter, and include precursors to climate active compounds (e.g., dimethyl sulfide [DMS]), which are likely regulated with environmental change. Here, intracellular concentrations of 45 metabolites were quantified in three sea-ice diatom species and were compared to two temperate diatom species, with a focus on compatible solutes and free amino acid pools. There was a large diversity of metabolite concentrations between diatoms with no clear pattern identifiable for sea-ice species. Concentrations of some compatible solutes (isethionic acid, homarine) approached 1 M in the sea-ice diatoms, Fragilariopsis cylindrus and Navicula cf. perminuta, but not in the larger sea-ice diatom, Nitzschia lecointei or in the temperate diatom species. The differential use of compatible solutes in sea-ice diatoms suggests different adaptive strategies and highlights which small organic compounds may be important in polar biogeochemical cycles.more » « less
