Are vertical distribution patterns of scleractinian corals maintained by pre- or post-settlement processes? A case study of three contrasting species

Abstract

ABSTRACT. Vertical zonation of hard corals in tropical coral reef Systems is a weil documented and predictable pattern in the organisation of tropical coral communities. However, the mechanisms that underly vertical zonation of hard corals are poorly understood. Two alternative conceptual models for the maintenance of vertical zonation are considered; depth-dependent settlement of larvae, or indiscriminant settlement of larvae with distnbutions determined by differential post-settlement mortality with depth. These alternative models were evaluated by undertaking field translocation experiments using 10 d old juveniles of 3 species with contrasting adult distnbutions: Goniastrea aspera (Verrillrestncted to shallow reef flat habitats; Oxypora lacera (Verrili)-restncted to low light, lower slope habitats; and Platygyra daedalea (Ehs and Solander) -a species with a broad depth range. Laboratoryraised larvae of each species were settled onto terracotta settlement plates and the plates translocated to 3 depths in the field: reef flat (0 m), mid slope (5 m), lower slope (10 m). Survival of the laboratorysettled juveniles was monitored at 3, 6 and 12 mo after settlement. For each of the 3 species, juveniles survived equaliy well at all 3 depths over the 12 mo study penod. The pattern of survivorship of G. aspera and P. daedalea among depths, however, was dependent on plate surface (top, bottom). Given the absence of depth-dependent survival of juveniles from the 2 zone-specific species G. aspera and 0. lacera, we reject the hypothesis that adult distribution patterns of these 2 species is determined by indiscriminant settlement of larvae followed by differential early post-settlement mortality with depth.

Pelagic conditions affect larval behavior, survival, and settlement patterns in the Caribbean coral Montastraea faveolata

“…Resale or republication not permitted without written consent of the publisher coral planulae are primitive larvae with limited mobility and no specialized organs (Harrison & Wallace 1990) has led to the assumption that their dispersal and survival is a predominantly passive, stochastic process (Scheltema 1986, Garrison 1999, Mundy & Babcock 2000. However, recent studies have shown that coral planulae move both actively and passively during dispersal and exhibit complex larval behavior during settlement (Babcock & Mundy 1996, Raimondi & Morse 2000, Stake & Sammarco 2003.…”

“…When considering larval behavior, one should be aware that life-history elements (i.e. growth, behavior and maintenance) are not independent, since energetic resources of invertebrate larvae are limited (Richmond 1987, Pechenik 1990, 1999, Hoegh-Guldberg & Emlet 1997, Bertram & Strathmann 1998, Pechenik et al 1998, Mundy & Babcock 2000. Differential allocation of resources among various life-history elements in response to variable environmental conditions provides the opportunity to optimize survival for an individual without means to replenish spent resources (Pechinek 1990).…”

“…Variations in salinity due to large-scale hydrodynamic processes or rainfall are likely to be a potential natural stressor during this life-phase, as members of the lower invertebrate groups, including the cnidarians, are not capable of osmoregulation (HoeghGuldberg & Smith 1989). Salinity affects the biology of many marine organisms (Lyster 1965, Mann et al 1991, Metaxas & Young 1998, Simpson & Hurlbert 1998, Garrison 1999 and most corals have a narrow salinity tolerance (Muthiga & Szmant 1987, Porter et al 1999, Mundy & Babcock 2000. Although salinity stress does occur, it is unlikely that it creates altered environmental conditions for prolonged periods of time, since hydrodynamic processes constantly mix large bodies of seawater.…”

Recruitment hotspots: consistent spatial patterns in the relative abundance of coral recruits at One Tree Island, Australia

“…The location of adult conspecifics may be particularly important because larvae may choose to settle in areas where adults are abundant i.e. aggregative settlement (Mundy and Babcock 2000, Carlon 2002, Vermeij 2005.…”

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.…”