Intraspecific variation in multiple trait responses of Alexandrium ostenfeldii towards elevated pCO.

Dissolved oceanic CO concentrations are rising as result of increasing atmospheric partial pressure of CO (pCO), which has large consequences for phytoplankton. To test how higher CO availability affects different traits of the toxic dinoflagellate Alexandrium ostenfeldii, we exposed three strains of the same population to 400 and 1,000 µatm CO, and measured traits including growth rate, cell volume, elemental composition, C fractionation, toxin content, and volatile organic compounds (VOCs). Strains largely increased their growth rates and particulate organic carbon and nitrogen production with higher pCO and showed significant changes in their VOC profile.

Meta-analysis reveals enhanced growth of marine harmful algae from temperate regions with warming and elevated CO levels.

Elevated pCO and warming may promote algal growth and toxin production, and thereby possibly support the proliferation and toxicity of harmful algal blooms (HABs). Here, we tested whether empirical data support this hypothesis using a meta-analytic approach and investigated the responses of growth rate and toxin content or toxicity of numerous marine and estuarine HAB species to elevated pCO and warming. Most of the available data on HAB responses towards the two tested climate change variables concern dinoflagellates, as many members of this phytoplankton group are known to cause HAB outbreaks.

Intraspecific trait variation and trade-offs within and across populations of a toxic dinoflagellate.

Intraspecific trait diversity can promote the success of a species, as complementarity of functional traits within populations may enhance its competitive success and facilitates resilience to changing environmental conditions. Here, we experimentally determined the variation and relationships between traits in 15 strains of the toxic dinoflagellate Alexandrium ostenfeldii derived from two populations. Measured traits included growth rate, cell size, elemental composition, nitrogen uptake kinetics, toxin production and allelochemical potency.

Combined physical, chemical and biological factors shape Alexandrium ostenfeldii blooms in The Netherlands.

Harmful algal blooms (HABs) are globally expanding, compromising water quality worldwide. HAB dynamics are determined by a complex interplay of abiotic and biotic factors, and their emergence has often been linked to eutrophication, and more recently to climate change. The dinoflagellate Alexandrium is one of the most widespread HAB genera and its success is based on key functional traits like allelopathy, mixotrophy, cyst formation and nutrient retrieval migrations.