Description
Casault, B., Johnson, C.L., Devred, E., Clay, S., and Beazley, L. 2025. Chemical and Biological
Oceanographic Conditions on the Scotian Shelf and in the Eastern Gulf of Maine during 2024.
Can. Tech. Rep. Fish. Aquat. Sci. 3744: vi + 58 p. https://doi.org/10.60825/p6ad-1k52
Nutrient and plankton conditions were assessed in the context of physical conditions observed
in the Maritimes Region in 2024. Nutrient depletion was widespread across the region, with
Prince 5 (P5) station recording its tenth consecutive year of below-normal surface and
subsurface nitrate inventories, while Cabot Strait section recorded record-low inventories for
surface nitrate, silicate, and phosphate. Lower nutrient conditions likely influenced
phytoplankton productivity, as chlorophyll-a measured in situ or derived from satellite remote
sensing was mainly near or below normal across the region. The spring phytoplankton bloom
was earlier than normal in the eastern area, near normal in the central area, and later than
normal in the western area of the region. The intensity of the spring bloom was mainly normal to
slightly below normal regionwide (except for Lurcher Shoal). The onset of the fall phytoplankton
bloom was delayed across most areas, with the Eastern Scotian Shelf indicating a record-late
onset. The intensity of the fall bloom was variable but mainly within near-normal ranges.
Calanus finmarchicus abundance was near normal for the core sections, but negative and
positive anomalies were recorded at the Halifax-2 (HL2) and P5 stations, respectively.
Pseudocalanus spp. abundance reached record-high levels for the Halifax section, but was
otherwise near normal. Mesozooplankton biomass was above normal at P5 but mainly below
normal elsewhere, with record-low biomass observed at HL2. Arctic Calanus species and
warm-water offshore copepods mainly remained at or below normal abundances, while
warm-water shelf copepods showed near-normal abundances except for negative anomalies
observed for the Halifax section and at P5.
Resources
| Name | Format | Description | Link |
|---|---|---|---|
| Figure 11 : Chlorophyll a inventory at the Maritimes high-frequency sampling stations | CSV | Open resource | |
| Figure 17 : Zooplankton (> 200 µm) abundance and community composition at the Maritimes high-frequency sampling stations | CSV | Open resource | |
| Figure 18 : Annual anomaly scorecards for zooplankton abundance and biomass | CSV | Open resource | |
| Figure 19 : Copepod abundance and composition at the Maritimes high-frequency sampling stations | CSV | Open resource | |
| Figure 21 : Calanus finmarchicus abundance and developmental stage distribution at the Maritimes high-frequency sampling stations | CSV | Open resource | |
| Figure 22 : Zooplankton biomass at the Maritimes high-frequency sampling stations | CSV | Open resource | |
| Figure 23 : Calanus finmarchicus abundance during the ecosystem trawl surveys | CSV | Open resource | |
| Figure 24 : Mesozooplankton dry biomass during the ecosystem trawl surveys | CSV | Open resource | |
| Figure 25 : Calanus finmarchicus abundance during the seasonal surveys on the core sections | CSV | Open resource | |
| Figure 26 : Mesozooplankton dry biomass during the seasonal surveys on the core sections | CSV | Open resource | |
| Figure 27 : Annual anomaly scorecard for non-copepod groups abundance on the Scotian Shelf sections | CSV | Open resource | |
| Figure 28 : Annual anomaly scorecards for copepod indicator species grouped abundance | CSV | Open resource | |
| Figure 06 : Nitrate inventories at the Maritimes high-frequency sampling stations | CSV | Open resource | |
| Figure 07 : Annual anomaly scorecards for surface (0–50 m) and deep (50–150 m) nitrate, silicate, and phosphate inventories | CSV | Open resource | |
| Canadian Technical Report of Fisheries and Aquatic Sciences 3744 | Open resource |