Spatial Patterns and Short-term Changes of Coral Assemblages Along a Cross-shelf Gradient in the Southwestern Lagoon of New Caledonia

Mehdi Adjeroud,Christophe Peignon,Mohsen Kayal,Lucie Penin,Emeline Poisson

doi:10.3390/d11020021

Abstract

Coral reef assemblages generally form gradients of spatial structures which are governed by a variety of interacting physical and biological processes that vary in intensity, frequency, and spatial scale. Assessing the structure of contemporary reef assemblages may help to understand future changes and to identify appropriate conservation actions. The spatial distribution and interannual variability (from 2006 to 2008) of coral assemblages were investigated at 10 stations in the southwestern lagoon of New Caledonia, and the strength of the cross-shelf gradient was evaluated. Coral cover, generic richness, and abundance of adult and juvenile assemblages were highly variable within and among the three major reef habitats (fringing, mid-shelf, and barrier reefs). Abundance increased with distance from shore, whereas generic richness and cover were not correlated with shelf position. Assemblage composition was generally related to habitat, even though some mid-shelf and fringing reef assemblages resembled those observed on other habitats. A significant correlation between juvenile and adult distributions was recorded, suggesting that adult assemblages are partly controlled by the short-term history of recruitment patterns. The interannual variation of coral assemblages was far less pronounced, with significant changes only detected at some mid-shelf and barrier reefs, for a few genera characterised by high turn-over.

Highlights

Coral reefs are characterised by exceptional biodiversity and complexity, and are among the most productive ecosystems on earth [1,2]
A decreasing trend was observed at mid-shelf stations (MS), whereas values increased at barrier reef station BA1
An opposite pattern was observed for encrusting coralline algae (ECA), with the highest values exhibited at barrier reef stations and the mid-shelf station MS2, whereas values were much lower at other stations (Figure 2C)

Summary

Introduction

Coral reefs are characterised by exceptional biodiversity and complexity, and are among the most productive ecosystems on earth [1,2]. Since the pioneering work of Goreau [11], spatial and temporal patterns within coral communities at multiple scales have been extensively documented worldwide [12,13,14,15]. This previous work shows that the distribution and dynamics of coral assemblages are governed by a variety of interacting extrinsic physical and biological. Recruitment is widely recognised as being a major driver in the dynamics and recovery of local populations following disturbances, though both pre- and post-settlement events may influence the local abundance and spatial distribution of adult assemblages [20,21,22,23,24]

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Conclusion