The role of mixing in controlling resource availability and phytoplankton community composition

Abstract

We investigate the role of mixing, through its effect on nutrient and light availability, as a driver of phytoplankton community composition in the context of Margalef's mandala. Data on microstructure turbulence, irradiance, new nitrogen supply and phytoplankton composition were collected at 102 stations in three contrasting marine environments: the Galician coastal upwelling system of the northwest Iberian Peninsula, the northwestern Mediterranean, and the tropical and subtropical Atlantic, Pacific and Indian oceans. Photosynthetic pigments concentration and microscopic analysis allowed us to investigate the contribution of diatoms, dinoflagellates, pico-and nanoeukaryotes, and cyanobacteria to the phytoplankton community. Simple linear regression was used to assess the role of environmental factors on community composition, and environmental overlap among different phytoplankton groups was computed using nonparametric kernel density functions. Mixing and new nitrogen supply played an important role in controlling the phytoplankton community structure. At lower values of mixing and new nitrogen supply cyanobacteria dominated, pico-and nanoeukaryotes were dominant across a wide range of environmental conditions, and finally enhanced new nitrogen supply was favourable for diatoms and dinoflagellates. Dinoflagellates were prevalent at intermediate mixing levels, whereas diatoms spread across a wider range of mixing conditions. Occasional instances of enhanced diatom biomass were found under low mixing, associated with the high abundance of Hemiaulus hauckii co-occurring with high N 2 fixation in subtropical regions, and with the formation of thin layers in the Galician coastal upwelling. Our results verify the Margalef's mandala for the whole phytoplankton community, emphasizing the need to consider nutrient supply, rather than nutrient concentration, as an indicator of nutrient availability.

Global diversity and distribution of aerobic anoxygenic phototrophs in the tropical and subtropical oceans

“…S2). Water mass properties and productivity regimes for the stations sampled in the Malaspina Circumnavigation Expedition have been previously described in detail (e.g., Estrada et al ., 2016; Regaudie‐de‐Gioux et al ., 2019; Teira et al ., 2019 and Villamaña et al ., 2019).…”

No β-N-Methylamino-L-alanine (BMAA) Was Detected in Stranded Cetaceans from Galicia (North-West Spain)

“…Among these diatoms, several potential BMAA-producers are accounted reaching high densities [19][20][21][22][23]. The estuaries ("rías") receive nutrients and phytoplankton from rivers, and high abundances of cyanobacteria, including potential BMAA-producers, are frequent in moderately stratified waters [71][72][73][74][75]. Unfortunately, BMAA levels for these bloom periods are unknown.…”

Mixing and Phytoplankton Growth in an Upwelling System

“…Only a limited number of studies have previously used microstructure observations to investigate the relationship between turbulence and phytoplankton activity and composition. Among those, most studies were focused on analyzing the role of mixing and nutrient supply as drivers of phytoplankton community structure (Sharples et al, 2007(Sharples et al, , 2009Machado et al, 2014;Villamaña et al, 2017Villamaña et al, , 2019. As far as we know only two studies have used microturbulence observations to investigate phytoplankton growth under the CTH framework.…”