Crustacean zooplankton release copious amounts of dissolved organic matter as taurine in the ocean

Abstract

Taurine (Tau), an amino acid‐like compound, is present in almost all marine metazoans including crustacean zooplankton. It plays an important physiological role in these organisms and is released into the ambient water throughout their life cycle. However, limited information is available on the release rates by marine organisms, the concentrations and turnover of Tau in the ocean. We determined dissolved free Tau concentrations throughout the water column and its release by abundant crustacean mesozooplankton at two open ocean sites (Gulf of Alaska and North Atlantic). At both locations, the concentrations of dissolved free Tau were in the low nM range (up to 15.7 nM) in epipelagic waters, declining sharply in the mesopelagic to about 0.2 nM and remaining fairly stable throughout the bathypelagic waters. Pacific amphipod–copepod assemblages exhibited lower dissolved free Tau release rates per unit biomass (0.8 ± 0.4 μmol g−1 C‐biomass h−1) than Atlantic copepods (ranging between 1.3 ± 0.4 μmol g−1 C‐biomass h−1 and 9.5 ± 2.1 μmol g−1 C‐biomass h−1), in agreement with the well‐documented inverse relationship between biomass‐normalized excretion rates and body size. Our results indicate that crustacean zooplankton might contribute significantly to the dissolved organic matter flux in marine ecosystems via dissolved free Tau release. Based on the release rates and assuming steady state dissolved free Tau concentrations, turnover times of dissolved free Tau range from 0.05 d to 2.3 d in the upper water column and are therefore similar to those of dissolved free amino acids. This rapid turnover indicates that dissolved free Tau is efficiently consumed in oceanic waters, most likely by heterotrophic bacteria.

Chemical Diversity and Biochemical Transformation of Biogenic Organic Sulfur in the Ocean

“…Taurine, an amino sulfonic acid, has many biological roles in the cell, including bile acid chelation, osmoregulation, and membrane stabilization (Lambert et al, 2015). Taurine is widely produced by marine metazoans and some phytoplankton at intracellular concentrations that may exceed 200 mM (Visscher et al, 1999;Tevatia et al, 2015;Clifford et al, 2017). In the North Atlantic Ocean, taurine concentrations were ∼0.1-10 nM in epipelagic waters, and ∼0.01-1 nM in bathypelagic waters (Clifford et al, 2019).…”

Metagenomic insights into zooplankton‐associated bacterial communities

“…The importance of taurine for bacterial growth has primarily been demonstrated using SAR11 cultures (Carini et al, 2013). The concentration and turnover rate of dissolved taurine in the ocean have only recently been determined (Clifford et al, 2017). Taurine is an organo-sulfonate found in the tissues of marine invertebrates such as zooplankton and is a potential source of carbon, nitrogen and sulfur for heterotrophic bacteria (Williams et al, 2012;Carini et al, 2013).…”

SAR11 bacteria have a high affinity and multifunctional glycine betaine transporter

“…Marine bacterioplankton have been observed to have promiscuous GBT transporters, with osmolytes similar in structure to GBT, such as dimethylsulfoniopropionate (DMSP), choline, and proline betaine, showing moderate to strong competition for the GBT transporter . Pelagibacter cells are known to oxidize several common osmolytes, including DMSP, an osmolyte known to be produced by phytoplankton and bacteria (Sun et al, 2016;Curson et al, 2017), and taurine, an osmolyte known to be secreted by zooplankton (Carini et al, 2013;Clifford et al, 2017).…”