Seasonal changes in bacteria and phytoplankton biomass control the condition index of the demosponge Halichondria panicea in temperate Danish waters
Bibliographic record
Abstract
Sponges are sessile filter-feeders, and the basic principles for water pumping and particle retention are the same among all demosponges. Phytoplankton cells smaller than the inhalant openings (ostia) are retained and phagocytosed in the inhalant canal system before the water is sieved through the collar filter of the choanocytes, which efficiently retain bacteria. However, the importance of bacteria versus phytoplankton as the main diet is unclear. Sponges must cope with seasonal changes in food availability in temperate waters, and during winter, low phytoplankton and bacterial biomasses may result in starvation. In this study, the lower threshold of suspended biomass resulting in starvation of the demosponge Halichondria panicea was determined. We measured the seasonal changes in phytoplankton and bacterial biomasses along with the sponge condition index (CI, the ratio of organic to inorganic matter). A low CI during winter reflected starvation, and based on total available carbon concentrations (phytoplankton plus bacterial carbon), we conclude that a concentration of ca. 30 µg C l<sup>−1</sup> was not sufficient to cover the maintenance costs of H. panicea. Bacteria constitute a minor, but consistent part of the diet, around 20%. A field growth experiment revealed a positive correlation between CI and sponge weight. Measured volume-specific clearance rate of sponges, density of choanocyte chambers and inter-choanocyte chamber-distance were not significantly different in low and high CI sponges, and it remains unknown how sponges withstand long periods with low suspended food particle concentrations.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Scholarly communication | 0.000 | 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 teacher head, 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".