Juvenile mortality in benthic marine invertebrates

Abstract

T h~r t y years ago Thorson (1966 Neth J Sea Res 3 267-293) calculated that juvenile mortallty in m a n n e bivalves could exceed 98 6 % Subsequently juvenile mortality rates have been assumed to be high and to influence the evolution of life history traits However there have been no attempts to establish whether high luvenile mortality IS common or to determine if lnterspecific trends in l u v e n~l e mortality exist To address t h~s Issue we revlewed 30 studies of age-specif~c mortality among bivalves, gastropods, barnacles ascid~ans, bryozoans and echinoderms High juvenile mortality is widespread among benthic marlne Invertebrates with 20 of the 30 s t u d~e s reporting levels of luven~l e mortal~ty > 9 0 % Mortal~ty is part~cularly h~g h during the first moments of luvenile life and can exceed 30% during the f~r s t day Pool~ng surv~vorship data from all species revealed a general trend with survivorsh~p decreasing exponentially during the first days or weeks of juvenile life until by the age of 4 mo, virtually all cohorts were reduced to < 2 0 % of their ~nitial numbers ~nortality remained low thereafter We suggest that extreme vulnerability at the onset of luvenile life is a shared t r a~t that is largely responsible for the surv~vorship trend Natural variation within this trend would be largely due to variation in intensity of mortality factors Predation and desiccation are well-documented causes of juvenile mortality, but the current lack of data on factors such as ultraviolet radiation, diseases and lnternal causes (energy depletion developmental and physiological defects) precludes a ranking of factors as select~ve pressures Methods used to quantify juvenile mortality vary cons~derably in the level of resolution they can achieve w t h i n the early luvenile perlod Studies of early juvenile mortality should ideally monitor the fate of individuals from the onset of luvenile l~f e using sampling intervals 5 1 d Mapping and imaging techniques can provide accurate results for sess~le organisms, whereas mark and recapture can be effective for motile animals w~t h l~m~t e d dispersal Early juvenile mortahty has been shown to influence population abundance and distnbution as well as community structure Juvenile mortality is also expected to be an important determinant of age at matunty, but only among species m a t u r~n g within 4 mo of postlarval l~f e since mortality remalns low after the age of 4 mo A compilation of data on age at first reproduction In 92 species revealed a b~modal grouping of species 22% of species matunng within 45 d after b e g i n n~n g luvenile life and 60% maturlng after at least 1 yr The influence of luven~le mortality on age at inaturlty will d~f f e r substantially among these 2 groups and will therefore not be equal or directly comparable among all species Given the magnitude of early juvenile mortality and the similarities in mortality patterns across diverse taxa and habitats a better understanding of early ]uvenile mortality should help researchers to understand how ...

Dissolution mortality of juvenile bivalves in coastal marine deposits

“…Size, not age, determines sexual maturity in M. mercenaria (Gosselin and Qian 1997). Data from this study show that, at least using the saturation states evaluated here (⍀ aragonite ϭ 0.3), larger bivalves are far less susceptible to dissolution mortality than smaller size classes, with a quasi-exponential decrease in mortality rate noted with increasing bivalve size (Fig.…”

“…Dissolution of recently set bivalves has profound ecological implications since populations may be substantially modified by the thermodynamic conditions encountered by juveniles during their transition from the water column to competent members of the benthos. Relatively small perturbations in the initial populations of settling marine bivalves translate to large alterations of adult populations (Gosselin and Qian 1997;Hunt and Scheibling 1997). This biological-geochemical couple raises interesting questions regarding the role of carbonate chemistry in regulating benthic community composition in nearshore estuarine sediments and merits further investigation.…”

“…Extremely high mortality (Ͼ98%) is widespread among settling marine bivalves in nearshore deposits, where exponential loss is common within the first several days to weeks following their full recruitment transition from the pelagic larval phase to the benthic juvenile phase (Thorson 1966;Roegner and Mann 1995;Gosselin and Qian 1997;Hunt and Scheibling 1997;Richards et. al.…”

Differences in feeding adaptations in intertidal and subtidal suspension-feeding gastropods: studies on Crepidula fornicata and Crepipatella peruviana

“…Because C. fornicata and C. peruviana do not move as adults and have only limited mobility as juveniles (and as small males) (Conklin 1897;Chaparro et al 2001a), individuals living at the upper edge of their intertidal range have less time to collect food than their subtidal conspecifics. Unless they have a mechanism that compensates for reduced feeding time, this could potentially limit their vertical distribution, especially if slower growth delays a potential escape in size from mortality in the intertidal zone (Gosselin and Qian 1997;Hunt and Scheibling 1997).…”

Role of post-settlement mortality in the establishment of Acropora reef slope zonation in Ishigaki Island, Japan

“…Mortality during the first few months after settlement is generally very high in benthic marine invertebrates, including corals (Gosselin and Qian 1997;Mundy and Babcock 2000;Wilson and Harrison 2005). To date, however, there is little information for Acropora corals regarding the stage in the life history during which a difference in mortality between shallowand deep-habitat species can be observed.…”