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Abstract Diatoms are among the most abundant phytoplankton that inhabit coastal ecosystems, forming large blooms that fuel coastal food webs. Although diatoms are often large and morphologically distinct, many are small or morphologically cryptic making it difficult to understand the temporal dynamics of whole diatom communities and the environmental factors that drive them. Here, we investigated diatom diversity and its environmental correlates using 6 yr of monthly surface water samples from the Narragansett Bay Plankton Time Series to investigate the seasonal and annual variability of diatom species occurrence. High‐throughput amplicon sequencing of filtered biomass yielded 658 diatom amplicon sequence variants (ASVs), of which 347 were identified to species. Of the 49 diatom genera in the sequencing dataset, 33% had never been observed in the time series using microscopy (1959–2014). We observed a weak quadratic relationship between ASV richness and chlorophyll‐aconcentrations, suggesting that richness decreases during blooms. There was a significant difference in diatom ASV richness by season and we identified distinct assemblages associated with different seasons. These assemblages were remarkably synchronous, exhibiting a sinewave‐like pattern, over 6 yr with an annual periodicity that correlated significantly with seasonal changes in temperature, light, and dissolved inorganic nitrogen. The annual cycle of diatom assemblages suggests stability in a key component of the estuarine food web known to influence ecosystem resilience and function. Deviations from the annual cycle of recurrence could be used to distinguish between changes in community structure driven by annual fluctuations in the environment and those driven by climate‐change stressors.
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This content will become publicly available on August 7, 2026
Genetic divergence in a marine copepod associated with marginal habitats across the subarctic Pacific
The lipid-rich copepodNeocalanus flemingeriis abundant throughout the subarctic Pacific, with a biogeographic range that includes the open ocean, marginal seas and fjord systems. Two distinct genetic variants have been reported based on differences in size: the ‘small form’, with a 1 yr life cycle, is found throughout the region, and the ‘large form’, with a 2 yr life cycle, is found in the western Pacific, where it is most abundant in the Sea of Okhotsk. Using a molecular approach, this study examined the genetic composition ofN. flemingeripopulations in the Gulf of Alaska from multiple stations over a 9 yr period. This is the first report of the occurrence of the large form in the eastern Pacific, where it exhibits a significant presence in fjord systems. However, in this region, both the small- and large-formN. flemingerihave annual life cycles. Collections from nearshore to offshore locations over multiple years indicated both interannual and spatial differences in the relative proportion of the 2 variants. Our results show that the forms inhabit overlapping yet distinct habitats, potentially due to adaptation to contrasting environmental conditions.
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- Award ID(s):
- 2222376
- PAR ID:
- 10636479
- Publisher / Repository:
- Inter-Research Science publisher
- Date Published:
- Journal Name:
- Marine Ecology Progress Series
- Volume:
- 766
- ISSN:
- 0171-8630
- Page Range / eLocation ID:
- 31 to 42
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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