Temperature differentially affects the persistence of polyunsaturated aldehydes in seawater

Abstract

Environmental context Diatoms, unicellular algae that live suspended in the water column, can undergo periods of rapid growth, called blooms. When these algal blooms die, organic compounds including polyunsaturated aldehydes are released to the surrounding water with currently unknown ecological effects. Here we demonstrate that temperature differentially affects the persistence of three major polyunsaturated aldehydes produced by diatoms, and we quantify the removal rates from seawater of these compounds. Abstract Polyunsaturated aldehydes (PUAs) are volatile compounds commonly released into the environment by different fresh and seawater phytoplankton species. Diatoms are among the main producers of these metabolites in seawater. The release of these metabolites in seawater is known to be wound-activated as a consequence of predation or cell lysis. Hence, the interaction of phytoplankton species that produce PUAs with other marine organisms is being thoroughly investigated. However, the stability of these compounds in seaweater once they are released and their persistence under different environmental conditions have never been quantified. In this work, we reveal an important effect of seawater temperature on the persistence of dissolved 2E,4E/Z-decadienal (DECA), 2E,4E/Z-octadienal (OCTA) and 2E,4E/Z-heptadienal (HEPTA) in seawater at the nanomolar scale. These three aldehydes were more persistent at 10°C than at either 15 or 20°C. Half lives of OCTA and HEPTA were reduced from 200h at 10°C to 80h at 15°C and 60h at 20°C. In addition, DECA was consistently more persistent than OCTA and HEPTA at the three temperatures assayed. This dependence of the persistence of dissolved PUAs on seawater temperature could determine a differential effect of equivalent PUA concentrations on the diversity and plankton community’s structure at different water depths, seasons or latitudes.