Prediction of ecological niches and carbon export by appendicularians using a new multispecies ecophysiological model

Abstract

We developed, calibrated and validated an ecophysiological model that represents food consumption, growth and production of faecal pellets and discarded houses during the life cycle of Oikopleura dioica, O. longicauda, O. fusiformis and O. rufescens, which are among the most abundant appendicularian species in the ocean. The forcing variables of the model are temperature (T ) and food concentration. We calculated the growth rates of the 4 species and predicted the dominant species as a function of environmental conditions on 3 ecological applications. Firstly, we used the seasonal changes in T and chlorophyll a (chl a) in the English Channel to predict the seasonal succession of the 4 species. Secondly, using sea surface T and chl a data from the MODIS satellite, we determined the dominant appendicularian species over the World Ocean, thus providing a first-ever description of appendicularian biogeography over the 4 different seasons. Thirdly, we applied our model to in situ observations performed with the Underwater Video Profiler during the POMME 3 cruise in the Northeastern Atlantic in 2001. In areas of high appendicularian concentrations (135 ind. m -3 ), the appendicularians grazed daily only 0.6% of the stock of total particulate carbon. Of this grazed material, 21% was used for growth, 14% was respired and 65% was lost as detritus. Based on our model predictions, we concluded that at 2 of the 4 sampling stations, the integrated mass of detritus produced by the appendicularian population equalled or exceeded the carbon flux recorded in sediment traps at 200 m depth. This indicated high rates of disaggregation and/or consumption of these particles during their transit to depth.

Pelagic tunicate grazing on marine microbes revealed by integrative approaches

“…Intact phytoplankton cells have been observed in salp fecal pellets (Silver and Bruland 1981). Discarded mucous houses, fecal pellets, and pseudofeces have high sinking rates (Silver and Bruland 1981;Noji et al 1997) and are also consumed by metazoan predators, including copepods, ostracods, and euphausiid larvae (Gorsky and Fenaux 1998;Lombard et al 2010). Export of material can be accelerated by vertical migration (e.g., salps and pyrosomes) (Wiebe et al 1979;Angel 1989;Andersen and Sardou 1992).…”

“…However, data also indicate differences between pelagic tunicate taxa in the efficiency of carbon export from the surface. For example, detritus from appendicularians (i.e., discarded mucous houses) disaggregates above 200 m, thus is not a major source of carbon to the deep sea (Lombard et al 2010). In contrast, salp carbon export is high at 200 m (Stone and Steinberg 2016).…”

Sinking of Gelatinous Zooplankton Biomass Increases Deep Carbon Transfer Efficiency Globally

“…Biogeochemical models (e.g., Gehlen et al, ; Ilyina et al, ; Laufkötter et al, ) are normally parameterized using particulate organic matter data (e.g., 0.5–1,000 μm marine snow and fecal pellets) that were derived from laboratory experiments (Ploug et al, ) or from sediment trap data (Gehlen et al, ). These models do not include jelly‐C (except larvaceans; Lombard & Kiørboe, ; Lombard et al, ) not only because this carbon transport mechanism is considered transient/episodic and not usually observed, and mass fluxes are too big to be collected by sediment traps (e.g., Siegel et al, ), but also because models aim to simplify the biotic compartments to facilitate calculations. Furthermore, jelly‐C deposits tend not to build up at the seafloor over a long time, such as phytodetritus (Beaulieu, ), being consumed rapidly by demersal and benthic organisms (Sweetman et al, ) or decomposed by microbes (Tinta et al, ).…”

Effect of Type and Concentration of Ballasting Particles on Sinking Rate of Marine Snow Produced by the Appendicularian Oikopleura dioica

“…These mucous feeding structures are an important source of marine snow formed by zooplankton [27], and may contribute significantly to POC flux [28,29]. Despite this potentially high contribution to carbon flux, only few studies have focused on appendicularians’ impact on POC fluxes [30], and nothing is known about the impact of food or ballasting particles (eg. [31]) on the sinking properties of discarded houses.…”