Multiple phytoplankton community responses to environmental change in a temperate coastal system: A trait-based approach

Abstract

The effect of environmental change in structuring the phytoplankton communities of the coastal waters of the Eastern English Channel was investigated by applying a trait-based approach on two decades (1996-2019) of monitoring on diatoms and Phaeocystis. We show that phytoplankton species richness in an unbalanced nutrient supply context was influenced by wind-driven processes, ecological specialization for dissolved inorganic phosphorous, temporal niche differentiation, and a competition-defense and/or a growth-defense trade-off, a coexistence mechanism where weak competitors (i.e., slower growing) are better protected against predation. Under the influence of both environmental perturbations (e.g., wind-driven processes, freshwater influence, unbalanced nutrient levels) and biotic interactions (e.g., competition, predation, facilitation), phytoplankton species exhibited specific survival strategies such as investment on growth, adaptation and tolerance of species to environmental stresses, silicification and resource specialization. These strategies have led to more speciose communities, higher productivity, functional redundancy and stability in the last decade. Our results revealed that the unbalanced nutrient reduction facilitated Phaeocystis blooms and that anthropogenic climate warming and nitrate reduction may threaten the diatom communities of the eastern English Channel in a near future. Our results provide strong support for biogeographical historical and niche-based processes in structuring the phytoplankton community in this temperate region. The variety of species responses that we characterized in this region may help to better understand future changes in pelagic ecosystems, and can serve as a basis to consider functional approaches for future ecosystem management.

On the conditions promoting Pseudo-nitzschia spp. blooms in the eastern English Channel and southern North Sea

“…The eastern English Channel and southern North Sea present an unusual phytoplankton succession occurring every spring. Each year, the Haptophyte P. globosa forms massive blooms between March and May and these blooms are preceded and followed by two diatom blooms with distinct species composition (Breton et al, 2000;Breton et al, 2022;Genitsaris et al, 2015;Grattepanche et al, 2011;Hernández-Fariñas et al, 2014).…”

“…This is the case of the eastern English Channel and southern North Sea. Phytoplankton research in this area has mainly focused on the understanding of the massive P. globosa blooms that occur every spring (Breton et al, 2000;Breton et al, 2022;Genitsaris et al, 2015;Grattepanche et al, 2011;Hernández-Fariñas et al, 2014;Peperzak, 2002).…”

Niche and interspecific association with respect to the dominant phytoplankton species in different hydrological periods of Lake Wuchang, China

“…Compared with the other dominant species, the niche width of Synedra acus varied from 3.55 to 6.65 (Table 2), indicating that Synedra acus had a stronger ability to compete for environmental resources and could be considered a widespread species in Lake Wuchang. In the wet season, an unbalanced nutrient supply arose with the increasing water temperature, which caused phytoplankton species to exhibit specific survival strategies, such as investment in growth, adaptation, tolerance of species to environmental stresses, solidification, and resource specialization (Breton et al, 2022), which led to cyanobacteria becoming the most common dominant species in the wet season. Moreover, Cyclotella and Aulacoseira were the dominant species only in the dry season, although both of them had higher niche widths (6.48 and 3.44, respectively), which might be due to their better adaptability to winter environmental conditions and less common resource use, so they were more likely to become the dominant species in a single habitat.…”