Diatom dynamics in a coastal ecosystem affected by upwelling: coupling between species succession, circulation and biogeochemical processes
Bibliographic record
Abstract
The typical phytoplankton succession scenario in coastal upwelling zones is high diatom growth during upwelling and flagellate dominance during water column stratification. Within the diatom/flagellate succession there exist short-term changes in diatom communities that are caused by physical, chemical and biological processes. In this study, we used an improved 2-D kinematic box model to assess the influence of these processes on diatom dynamics in an estuarine ecosystem affected by coastal upwelling. This model enabled us to separate hydrographic from biogeochemical processes occurring in the estuary. Hydrographic variables, nutrient concentrations and phytoplankton composition were determined over a 2 wk period in the Ra de Vigo, NW Spain. Two major hydrographic phases were identified which coincided with a clear temporal and spatial separation between 2 diatom assemblages: Thalassiosira spp./Skeletonema costatum and Chaetoceros spp./Cerataulina pelagica. During upwelling, horizontal (6.6 km d -1 ) and vertical (11.7 m d -1 ) convective fluxes were high, causing a net input of NO 3 -, HPO 4 2and SiO 4 H 4 . During this phase the Thalassiosira spp./ S. costatum standing stock was high (> 20 mol C l -1 ). Hydrographic processes, however, affected the Thalassiosira spp./S. costatum assemblage more than biogeochemical processes and this resulted in the net loss of this assemblage from the Ra and its export towards the shelf. There was a significant correlation between the biogeochemical variations in this diatom assemblage and silicate, suggesting a strong dependency of Thalassiosira spp./S. costatum on this nutrient. By comparison, due to the higher carbon-specific net growth rate of the Chaetoceros spp./C. pelagica assemblage (0.35 d -1 ) during upwelling, this assemblage maintained a high biomass in the Ra. Upwelling was followed by upwelling relaxation when horizontal (1.9 km d -1 ) and vertical fluxes (1.8 m d -1 ) were reduced and nutrient levels diminished. During upwelling relaxation there was an accumulation of Chaetoceros spp./C. pelagica biomass (>18 mol C l -1 ). Biogeochemical processes provoked a loss of Thalassiosira spp./S. costatum due to rapid sedimentation and a net increase in Chaetoceros spp./C. pelagica. It is suggested that the accumulation of Chaetoceros spp. is aided by a lower sinking rate whereas the selection of C. pelagica is more dependent on NO 3 -and HPO 4 2consumption. It is concluded that upwelling events in the Ra cause the exportation of Thalassiosira spp./S. costatum standing stock from the Ra towards the shelf, which will ultimately benefit shelf pelagic and benthic fish communities. Upwelling relaxation events favour the retention of a high standing stock of Chaetoceros spp./ C. pelagica, which is then directly available to the shellfish aquaculture of the Ra.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".