Environmental Impact on Harmful Species Pseudo-nitzschia spp. and Phaeocystis globosa Phenology and Niche

Abstract

Global environmental change modifies the phytoplankton community, which leads to variations in their phenology and potentially causes a temporal mismatch between primary producers and consumers. In parallel, phytoplankton community change can favor the appearance of harmful species, which makes the understanding of the mechanisms involved in structuring phytoplankton ecological niches paramount for preventing future risk. In this study, we aimed to assess for the first time the relationship between environmental conditions, phenology and niche ecology of harmful species Phaeocystis globosa and the complex Pseudo-nitzschia along the French coast of the eastern English Channel. A new method of bloom detection within a time-series was developed, which allowed the characterization of 363 blooms by 22 phenological variables over 11 stations from 1998 to 2019. The pairwise quantification of asymmetric dependencies between the phenological variables revealed the implication of different mechanisms, common and distinct between the taxa studied. A PERMANOVA helped to reveal the importance of seasonal change in the environmental and community variables. The Outlying Mean and the Within Outlying Mean indexes allowed us to position the harmful taxa niche among the rest of community and quantify how their respective phenology impacted the dynamic of their subniches. We also discussed the possible hypothesis involved and the perspective of predictive models.

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

“…Indeed, longer Pseudo-nitzschia spp. blooms (bloom length: 246 days, i.e., approximately 30 weeks) were recently reported for coastal areas mostly affected by seasonal stratification-destratification cycles, not shorter upwelling-downwelling cycles (Karasiewicz and Lefebvre, 2022). Interestingly, over L9 coastal production area, subjected to minor upwelling influence and higher riverine discharges, no significant intra-annual patterns in the abundance of ASP-producers were detected, reflecting the complexity of forces acting at the land-ocean interface Jassby, 2008, 2010).…”

“…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). Considering all bloom events, for each annual cycle, the following phenological indices were estimated for each coastal production area (L6, L7a, L7c, L8, L9) and HAB group: (1) number of bloom events (bloom events year − 1 ); (2) duration of bloom events (weeks bloom − 1 ); (3) total duration of all bloom events per year (weeks year − 1 ); (4) HAB abundance peak value (cells L − 1 ); (5) timing of bloom initiation (i.e., first week when HAB abundance surpassed the threshold criterion; expressed in week of the year, WOY); (6) HAB abundance peak timing (WOY); and (7) timing of bloom termination (last week when HAB abundance was above the threshold criterion; WOY).…”

Seasonal dietary niche changes in Neotropical bats

“…2021), respectively. The residual tolerance (RTol) quantifies the information lost after dimensional reduction (Karasiewicz & Lefebvre 2022). This parameter evaluates the reliability of the variables used to define the species’ niche (Dolédec et al .…”

Dynamic Linear Models for analysing time series data in coastal environmental monitoring

“…Many other parameters may be defined based upon this seasonality function (cf. Guallar et al, 2017;Karasiewicz and Lefebvre, 2022).…”