Rock bottom: Colonization patterns of deep-sea Arctic and subarctic dropstones (200–1300 m)
Bibliographic record
Abstract
Hard substrata of allochthonous origin, such as ice-rafted dropstones, can provide essential habitat for benthic communities in the polar and subpolar deep sea, acting as “islands” in otherwise finer-grained sedimentary environments. The present study explored the diversity and distribution patterns of morphospecies (msp/mspp) present on dropstones collected at depths of ∼200–500 m in the Labrador Sea (LAB) and ∼700–1300 m in Baffin Bay (BAF), respectively spanning subarctic and Arctic regions of eastern Canada. Specifically, the zonation, intra- and interspecific interactions, and succession of all colonizers were examined. Based on in - situ images, dropstones exhibited ∼94% greater epibenthic megafaunal richness than similar surfaces of the substratum immediately surrounding them. Analysis of three dropstones collected from each of six sites documented a total of 101 sessile and motile taxa spanning 10 phyla. Across sites, bryozoans dominated at all depths and locations (27 mspp, plus 3 dead) followed by poriferans (27 mspp), 19 cnidarians, eight arthropods, eight annelids, five chordates (tunicates), three echinoderms, three molluscs, and one foraminifer. There were 19 mspp that spanned both LAB and BAF, with greater overall richness in the subarctic region (62 vs 26 mspp). A total of 64 sessile mspp occurred above the stone-sediment interface (e.g., cnidarians and poriferans), whereas 22 mspp (mostly bryozoans) occurred at the stone-sediment interface; one morphospecies of polychaete occurred below. The most abundant morphospecies was an arborescent bryozoan, while two encrusting bryozoans covered the most surface area. Eight morphospecies occurred as just one individual or colony per stone, and 35 mspp appeared to maintain an exclusion zone between conspecifics (e.g., tube-dwelling annelids, hydrozoans, and anthozoans). Conversely, in 51 mspp conspecifics occurred abutting one another (e.g., bryozoans and poriferans). Allospecific exclusion zones appeared to occur in 27 mspp (e.g., bryozoans and annelids), whereas 59 allospecifics (e.g., poriferans, cnidarians, and chordates) occurred within touching distance. Secondary colonization (including cases of epibiosis) was observed in 83 mspp, documenting 204 unique pairings of hosts and colonizers. The number and diversity of morphospecies colonizing dropstones in the deep sea of the eastern Canadian Arctic and subarctic support the role of dropstones as oases that facilitate connectivity in an otherwise poorly diversified epibenthic environment. • Deep-sea epibenthic communities on subarctic and Arctic dropstones were compared • Subarctic dropstone communities had higher richness than Arctic dropstones • Most taxa colonized exposed surface rather than sediment boundary or undersurface • Distances between conspecifics were greater than distances between allospecifics • Epibiosis and overgrowth of allospecifics was common, evoking communities in flux
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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 | 0.007 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.006 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 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".