Species-specific house productivity of appendicularians

Abstract

Appendicularians, pelagic tunicates that are common in world oceans, periodically produce new mucus houses and discard old ones. Discarded houses form macroscopic aggregates that constitute sites of biological activity in the water column and also contribute to the transport of organic matter to deeper water. In this study, we measured the house renewal rates of 10 appendicularian species cultivated in 30 µm-mesh-screened seawater at 17 to 29°C. In addition, the carbon content of the tunicates (C B ), their newly secreted houses (C NH ) and their discarded houses (C DH ) were concurrently examined for some of the oikopleurid species. , and that the first 3 species could discard houses corresponding to 380, 708 and 174% of their biomass d -1 , respectively. The individual lifetime production of C NH and C DH for all 3 species was estimated to be 1.1 to 3.6 and 2.7 to 12 times greater than the C B of mature individuals. This high houseproductivity, combined with large population sizes, indicates that appendicularians are major producers of macroscopic aggregates in marine ecosystems. KEY WORDS: Appendicularians · House · House renewal rate · Carbon content · Macroscopic aggregatesResale or republication not permitted without written consent of the publisher

Ecology of Anguilliform Leptocephali: Remarkable Transparent Fish Larvae of the Ocean Surface Layer

“…4 2009 of various types of zooplankton (Alldredge 1976). Some fish larvae also feed directly on discarded larvacean houses, because they are often abundant and they are immediately replaced by a new house when their filters clog (Alldredge 1972(Alldredge , 1976Sato et al 2003). Other fish feed directly on the larvaceans themselves (Capitanio et al 2005;Llopiz and Cowen 2009), but by feeding only on discarded larvacean houses or marine snow, leptocephali do not directly impact the organisms producing their food source.…”

Phytoplankton as Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate

“…Marine snow comprises macroscopic organic aggregates >500 µm in size and originates from clumps of aggregated phytoplankton (phytodetritus), discarded appendicularian houses, fecal matter and other miscellaneous detrital particles [21]. Appendicularians secrete mucous feeding structures or "houses" to collect food particles and discard and renew them up to 40 times a day [32]. Discarded appendicularian houses are highly abundant (thousands per m 3 in surface waters) and are microbial hotspots with high concentrations of bacteria, ciliates, flagellates and phytoplankton.…”

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

“…They contribute to actively transfer biogenic carbon to depth (Robison et al 2005) through their large production of fast-sinking discarded houses and faecal pellets (López-Urrutia & Acuña 1999, Sato et al 2003, Alldredge 2005, high growth rates (Hopcroft & Roff 1995), short life cycles (Fenaux 1976), and ability to feed intensively on small particles (Fernández et al 2004). They also play an important role in marine food webs as grazers of the ecosystem's microbial components and food source for lager organisms (Gorsky & Fenaux 1998, Zubkov & López-Urrutia 2003, Purcell et al 2005.…”

“…They also play an important role in marine food webs as grazers of the ecosystem's microbial components and food source for lager organisms (Gorsky & Fenaux 1998, Zubkov & López-Urrutia 2003, Purcell et al 2005. Because different appendicularian species have different metabolic rates, notably their filtration rate and production of discarded houses (Sato et al 2003(Sato et al , 2005, they have different effects on the ecosystem (López-Urrutia et al 2005) and, thus, on biogeo-chemical fluxes. Hence, it is important to identify these organisms to the species level in order to estimate their potential ecological or biogeochemical roles.…”