The Lagoon at Caroline/Millennium Atoll, Republic of Kiribati: Natural History of a Nearly Pristine Ecosystem

University of Hull, United Kingdom
PLoS ONE (Impact Factor: 3.53). 06/2010; 5(6):e10950. DOI: 10.1371/journal.pone.0010950
Source: PubMed

ABSTRACT A series of surveys were carried out to characterize the physical and biological parameters of the Millennium Atoll lagoon during a research expedition in April of 2009. Millennium is a remote coral atoll in the Central Pacific belonging to the Republic of Kiribati, and a member of the Southern Line Islands chain. The atoll is among the few remaining coral reef ecosystems that are relatively pristine. The lagoon is highly enclosed, and was characterized by reticulate patch and line reefs throughout the center of the lagoon as well as perimeter reefs around the rim of the atoll. The depth reached a maximum of 33.3 m in the central region of the lagoon, and averaged between 8.8 and 13.7 m in most of the pools. The deepest areas were found to harbor large platforms of Favia matthaii, which presumably provided a base upon which the dominant corals (Acropora spp.) grew to form the reticulate reef structure. The benthic algal communities consisted mainly of crustose coralline algae (CCA), microfilamentous turf algae and isolated patches of Halimeda spp. and Caulerpa spp. Fish species richness in the lagoon was half of that observed on the adjacent fore reef. The lagoon is likely an important nursery habitat for a number of important fisheries species including the blacktip reef shark and Napoleon wrasse, which are heavily exploited elsewhere around the world but were common in the lagoon at Millennium. The lagoon also supports an abundance of giant clams (Tridacna maxima). Millennium lagoon provides an excellent reference of a relatively undisturbed coral atoll. As with most coral reefs around the world, the lagoon communities of Millennium may be threatened by climate change and associated warming, acidification and sea level rise, as well as sporadic local resource exploitation which is difficult to monitor and enforce because of the atoll's remote location. While the remote nature of Millennium has allowed it to remain one of the few nearly pristine coral reef ecosystems in the world, it is imperative that this ecosystem receives protection so that it may survive for future generations.

Download full-text


Available from: Katie Barott, Aug 16, 2015
  • Source
    • "We have not classified the previously-mentioned Millenium Atoll with the cellular reefs listed above because the scale of the cellular morphology at Millenium and in many other Pacific atoll lagoons is up to an order of magnitude larger than the Abrolhos. While the large-scale cellular reefs also seem to consist predominantly of branching Acropora (Roy & Smith, 1971; Grovhoug & Henderson, 1976; Valencia, 1977; Barott et al., 2010), we do not believe our model applies directly to them because it cannot produce cells of their horizontal dimensions unless it is scaled up massively, to unrealistic depths of at least 100 m. We are currently investigating the large-scale cellular morphology. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The three-dimensional form of a coral reef develops through interactions and feedbacks between its constituent organisms and their environment. Reef morphology therefore contains a potential wealth of ecological information, accessible if the relationships between morphology and ecology can be decoded. Traditionally, reef morphology has been attributed to external controls such as substrate topography or hydrodynamic influences. Little is known about inherent reef morphology in the absence of external control. Here we use reef growth simulations, based on observations in the cellular reefs of Western Australia's Houtman Abrolhos Islands, to show that reef morphology is fundamentally determined by the mechanical behaviour of the reef-building organisms themselves-specifically their tendency to either remain in place or to collapse. Reef-building organisms that tend to remain in place, such as massive and encrusting corals or coralline algae, produce nodular reefs, whereas those that tend to collapse, such as branching Acropora, produce cellular reefs. The purest reef growth forms arise in sheltered lagoons dominated by a single type of reef builder, as in the branching Acropora-dominated lagoons of the Abrolhos. In these situations reef morphology can be considered a phenotype of the predominant reef building organism. The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images. More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef.
    PeerJ 01/2015; 3:e935. DOI:10.7717/peerj.935 · 2.10 Impact Factor
  • Source
    • "comm. Jim Maragos), which is dominated by Acropora spp., but also characterised by abundant cover of crustose coralline algae , turfing algae and the giant clam Tridacna maxima (Barott et al., 2010). A large number of T. maxima shells and many dead coral microatolls remain in Palmyra's lagoon supporting this suggestion . "
    [Show abstract] [Hide abstract]
    ABSTRACT: The lagoon at Palmyra Atoll in the central Pacific was subject to major military modifications during WWII and now the dominant fauna on the lagoon's hard substrate are sponges, not corals. In this study, we quantified the physical and biological factors explaining the variation in sponge distribution patterns across 11 sites to determine the potential for the sponges in the lagoon at Palmyra to invade the surrounding reef systems. Significant differences in sponge assemblages were found among all but three sites. For all the models we examined the strongest environmental relationships were found for variables related to sedimentation/turbidity and food/habitat availability. Our findings suggest that the sponges in Palmyra's lagoon are likely to be restricted to this habitat type where they are associated with conditions resulting from the earlier heavy disturbance and are unlikely to spread to the outer reef environments unless there is a dramatic decline in environmental quality.
    Marine Pollution Bulletin 11/2012; 66(1-2). DOI:10.1016/j.marpolbul.2012.08.017 · 2.79 Impact Factor
  • Source
    • "Natural history of the Millennium Atoll black reef Millennium, formerly Caroline Island, is the most southern atoll of the LI (latitude: À9.955, longitude: À150.210). The reefs on Millennium were characterized by high fish abundances (Barott et al., 2010), "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Line Islands are calcium carbonate coral reef platforms located in iron-poor regions of the central Pacific. Natural terrestrial run-off of iron is non-existent and aerial deposition is extremely low. However, a number of ship groundings have occurred on these atolls. The reefs surrounding the shipwreck debris are characterized by high benthic cover of turf algae, macroalgae, cyanobacterial mats and corallimorphs, as well as particulate-laden, cloudy water. These sites also have very low coral and crustose coralline algal cover and are call black reefs because of the dark-colored benthic community and reduced clarity of the overlying water column. Here we use a combination of benthic surveys, chemistry, metagenomics and microcosms to investigate if and how shipwrecks initiate and maintain black reefs. Comparative surveys show that the live coral cover was reduced from 40 to 60% to <10% on black reefs on Millennium, Tabuaeran and Kingman. These three sites are relatively large (>0.75 km(2)). The phase shift occurs rapidly; the Kingman black reef formed within 3 years of the ship grounding. Iron concentrations in algae tissue from the Millennium black reef site were six times higher than in algae collected from reference sites. Metagenomic sequencing of the Millennium Atoll black reef-associated microbial community was enriched in iron-associated virulence genes and known pathogens. Microcosm experiments showed that corals were killed by black reef rubble through microbial activity. Together these results demonstrate that shipwrecks and their associated iron pose significant threats to coral reefs in iron-limited regions.
    The ISME Journal 09/2011; 6(3):638-49. DOI:10.1038/ismej.2011.114 · 9.27 Impact Factor
Show more