Comparing historical and contemporary macrofaunal communities and functional traits in a subarctic embayment in Newfoundland, Canada
Notice bibliographique
Résumé
Studies examining biological communities in relation to environmental factors over time are essential for understanding natural sources of community variation (i.e., structure and function), as well as their response to stressors. Benthic macrofauna are important biological indicators used to assess environmental quality in marine ecosystems. Placentia Bay is a large subarctic embayment on the southeast coast of Newfoundland (NL) that has been identified as an Ecologically and Biologically Significant Area (EBSA) that is exposed to anthropogenic stressors (e.g., fisheries and hazardous substances). The overarching aim of my thesis research was to assess the influence of various environmental factors on the community structure and functional traits of macrofauna in Placentia Bay using contemporary and historical biological and environmental data. Comparison of macrofauna at 8 stations sampled in 1998 and 2019–2020 (n=77) showed significant temporal changes in community structure and function, without loss of function (i.e., 36 morphological/behavioral modalities). The historical community had significantly higher densities, but lower evenness and diversity compared to contemporary years. Macrofauna were dominated by highly tolerant (82.3%) subsurface deposit feeders (62.1%) having small body sizes, whereas contemporary communities had a higher proportion of medium tolerant species/taxa (7.2 vs. 36.7%) and nearly equal proportions of subsurface and surface deposit feeders (26.7 and 29.1%) with small-medium body sizes. These changes are likely a reflection of the large reduction in the relative proportion of polychaetes (91 vs. 58%). Community patterns were related to the sedimentary habit. Sediments have become coarser with higher levels of sedimentary total organic matter in the contemporary compared to the historical years. Interestingly, while grain size has also become coarser between 2019 and 2020 communities were similar. Moreover, even though contaminants (examined in 2020 only) were not above probable biological effect levels, depth and heavy metal concentrations were most correlated to macrofaunal community structure among different areas in the bay. This research indicates the need for studies specifically designed to better quantify temporal changes in total organic carbon and heavy metals in relation to potential anthropogenic sources and effects on macrofauna in the bay. It is recommended that total organic carbon and C/N ratios (indicator of food quality/source) are continuously monitored to examine how their levels change over time and the possible source(s) of enrichment. Additionally, as development continues in coastal regions such as Placentia Bay future studies examining acceptable contaminant levels and possible biological outcomes are needed.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,002 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».