Interannual Variability in the Thermal Habitat of Alexandrium catenella in the Bay of Fundy and the Implications of Climate Change

Abstract

Globally, harmful algal blooms (HABs) are an increasing problem. In the Gulf of Maine and Bay of Fundy, blooms of the toxic dinoflagellate Alexandrium catenella are annually recurrent phenomena. As this region is one of the most rapidly warming areas of the global ocean, an improved understanding of the mechanisms driving the initiation of local A. catenella blooms, their interannual variability and the implications of future climate change is critical to local monitoring strategies and marine resources management. A 27-year (1988–2014) time series of weekly A. catenella cell counts from the Bay of Fundy and concurrent satellite-measured sea surface temperature, freshwater discharge from the St. John River and wind-driven turbulence are compared to assess their relationship to variability in bloom phenology metrics. The mean thermal habitat associated with early detection of A. catenella is 6.5 ± 1.6°C, whereas that of bloom initiation averages 9.2 ± 1.5°C. Both thermal habitats for A. catenella are trending earlier over the study period. Bloom initiations that precede the arrival of the thermal habitat mean (occur in colder water) are associated with higher spring freshwater discharge and are generally weaker blooms. Increased spring freshwater discharge is also associated with earlier bloom initiation and earlier maximum concentration dates. No significant relationship was observed with the strength of wind-driven mixing. Removal of the mean thermal seasonal cycle shows that surface temperature anomalies have a strong negative relationship to the bloom phenology metrics and arrival of thermal habitat: warmer years are linked to earlier arrival of thermal habitats (∼12 days °C–1) and earlier detection and bloom initiation dates (∼33 days °C–1). Using these relationships and present trends in Bay of Fundy surface temperature warming over the period 1982–2019, we project the arrival dates of bloom thermal habitat and bloom phenology metrics out to the middle of this century. Based on current rates of sea surface temperature change, bloom phenology metrics (e.g., bloom initiation, early detection), can be expected to shift 1–2 months earlier in the season by mid-century. Such changes in the phenology of A. catenella blooms will need to be incorporated into both monitoring strategies and forecasting models for the region.

Variability patterns and phenology of harmful phytoplankton blooms off southern Portugal: Looking for region-specific environmental drivers and predictors

“…Phenological indices for ASP-, DSP-, and PSP-producers, were estimated using in-situ abundance data, retrieved from IPMA public database. For each group and coastal production area, bloom events were defined as occurrences when abundance exceeded 5% above the annual local median value, at least during two consecutive weeks (Siegel et al, 2002), a threshold criterion used in phytoplankton (Ferreira et al, 2014; see Krug et al, 2018b and references therein) and HAB (see Bucci et al, 2020;5− 25%) studies. This approach implicitly considered variable bloom thresholds depending on annual cycles, HAB groups, and coastal production areas, an advantage over recent studies of HAB phenology (Guallar et al, 2017;Karasiewicz and Lefebvre, 2022).…”

Apparent biogeographical trends in Alexandrium blooms for northern Europe: identifying links to climate change and effective adaptive actions

“…Alexandrium cyst beds have been extensively mapped along the western Atlantic margin, including estuaries and embayments of the Gulf of St. Lawrence, Bay of Fundy and the Gulf of Maine (e.g., Castell- Perez et al, 1998;Matrai et al, 2005;Stock et al, 2005;Martin et al, 2014;Anderson et al, 2014;Bucci et al, 2020), and recently for the Alaskan coast of the Chuckchi Sea (Anderson et al, 2021). In northern Europe, the biogeographical extent of Alexandrium cyst beds has been determined only locally and sporadically for a few coastal zones.…”

Long-term temperature trend in Kamchatka supports expansion of harmful algae

“…The harmful algae expand over their spatial range limits, harmful algal blooms (HABs) happen in different coastal areas, and the underlying causes and factors influencing the dynamics of toxic algae are targets of many studies (Hallegraeff, 2010; Bucci et al, 2020; Hays et al, 2005; Gobler et al, 2017; Ho et al, 2019; Griffith et al, 2020; Trainer et al, 2020; Errera et al, 2014). The temperature of the upper ocean is a fundamental feature controlling phytoplankton metabolic processes (Raven, and Geider, 1988; Moisan et al, 2002; Thomas et al, 2012) and a major metric that could be used for predicting HABs (Ralston et al, 2014).…”