THE USE OF ENVIRONMENTAL DNA TO CHARACTERIZE FISH ASSEMBLAGES IN TEMPERATE ESTUARIES OF VARYING LEVELS OF NUTRIENT IMPACT
Notice bibliographique
Résumé
The inner region has been identified as an important area for evaluating the health of estuaries, as many riverine inputs, like excessive nutrients (eutrophication), are more concentrated here than in the lower reaches of the estuary. However, the inner estuary’s fish assemblage is undersampled in Canada’s southern Gulf of Saint Lawrence due to issue of accessibility, and avoidance due to high macroalgal biomass. To help address these issues, this dissertation investigated the inner estuary’s fish assemblage with novel methods for evaluating these assemblages. Chapter 3 assessed whether the inner estuarine region possessed distinct nearshore fish assemblages relative to the middle and outer estuarine regions. The abundance of northern mummichog (Fundulus heteroclitus macrolepidotus) was also investigated as a potential indicator of estuarine eutrophication to simplify the sampling effort. Three Prince Edward Island estuaries with varying levels of nutrient impact were sampled in August 2020 and again, along with one additional estuary, in June and August 2021. Each estuary was sampled in the inner, middle, and outer regions. Results from multivariate analyses suggest that the inner region is generally distinct from the middle and outer regions at all estuaries. Mummichogs were generally found in higher abundance in the inner region of most estuaries and displayed a strong, positive linear correlation with sea lettuce abundance. Nearshore fish assemblages were more similar between estuaries from the same shoreline (north vs south shore) than between estuaries with similar levels of nutrient impact (defined by eutrophic times). However, the inner region of estuaries with higher levels of nutrient impact were found to also have relatively higher mean mummichog abundance than inner regions of estuaries with lower nutrient impact. Thus, mummichog abundance may offer an indication of eutrophication within the inner region of estuaries. Chapter 4 evaluated whether environmental DNA (eDNA) metabarcoding, could act as a complement or replacement to beach seining. Three stations (inner, middle, and outer estuary) were sampled using eDNA medium collection (1 L water samples) and beach seines across estuaries sampled in the previous data chapter. eDNA metabarcoding detected more fish species than beach seining, including deeper water species like striped bass (Morone saxatilis) and the endangered winter skate (Leucoraja ocellata). eDNA metabarcoding also differentiated stations 0.4-3 km apart and detected the seasonal and interannual shifts in the fish assemblages suggested by beach seining. Most surprising was that the most abundant fish taxa detected by eDNA metabarcoding and beach seining often contributed similar percentages of the total composition. Thus, eDNA metabarcoding has not only the potential to act as a complement to beach seining (i.e., detect additional species/ genera) but could serve as a replacement in the sea lettuce-infested inner regions of eutrophic estuaries. This dissertation’s primary findings, namely that mummichog abundance in the inner estuary may serve as an indicator of eutrophication and eDNA metabarcoding could serve as a complement and replacement for beach seining, may be directly used in assessing estuarine health across the southern Gulf of Saint Lawrence.
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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 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| 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 ».