Diversity Of Coral Communities Research Articles

The Ecological Status and Change in High-Latitude Coral Assemblages at the Xuwen Coral Reef, Northern South China Sea: Insight into the Status and Causes in 2020

Taking the coral communities of the Xuwen coral reef in 2020 as the research object, we analyzed the species composition, diversity, and interspecific Spearman correlation of the scleractinian coral communities, investigated the features and spatial distribution of the scleractinian coral community, and discussed the correlation between the community composition and environmental factors to identify the affecting factors and their sources. These results showed that (1) compared with the survey in 2004, the coverage of corals in 2020 had significantly decreased, while the dominant genera were still Goniopora and Porites. The coral morphology was massive, and the diversity of the coral community (Shannon-Wiener index, H') was 2.87. The distribution of coral was uneven. The competition among some dominant species of coral was intense. (2) The mass coral bleaching event in the NSCS in August 2020 did not cause severe coral death in the short term on the Xuwen coral reef. (3) The growth of the coral community in 2020 might be greatly affected by high suspended solids and nutrient levels, which were related to the current, mariculture, and coastal erosion. (4) Anthropogenic activities such as coastal aquaculture and fishing were the major factors leading to the reduction in coral coverage on Xuwen coral reef in the past 10 years.

Coral community of Holocene coral reef in the southern South China Sea and its significance for reef growth

Ancient coral reefs are rich archives of historical process and vital baselines for future development. Coring gives a window into the growth of ancient coral reefs and the fossil coral community's response to paleoenvironment. Well NK-1 drilled from Meiji Reef is the longest scientific core with the highest recovery in the South China Sea. This study focused on the upper section of the Well NK-1 accumulated during the Holocene. From 8200 yr BP, Holocene reef initiated on the substrates of Pleistocene limestone and stopped accreting vertically at 4800 yr BP. It consisted of an initiation and fast reef growth (5.6 mm yr−1) from 8200 yr BP to 7300 yr BP, a shift to slow reef growth (2.0 mm yr−1) between 7300 yr BP and 5400 yr BP, a return to a rapid reef growth (8.8 mm yr−1) from 5400 yr BP to 4800 yr BP, and finally a cessation of upward accretion and a reinforced lateral progradation since 4800 yr BP. A total of 11 coral genera and 16 Acropora species were identified from the Holocene segment of the core. The diversity of coral communities had an impact on reef growth. Coral communities with less genera and absolute predominance of branching Acropora were corresponded with a rapid vertical accumulation of reef framework with higher accretion rate. Acropora corals with rapid growth and dispersion by fragmentation were principal reef-builders during the Holocene, with A.valida being the most prevalent coral species. The highest Acropora species richness occurred at the geological era of 5400–5300 yr BP when reef accumulated with the fastest upward accretion rate of 23.1 mm yr−1. This intricate and detailed pattern presented a new and novel model for the development of Holocene reef, indicating that the coral community and key reef builders were crucial to reef growth. These findings are extremely helpful for understanding the current ecological state of modern coral reefs as well as their potential response to global climate change.

Functional Richness and Resilience in Coral Reef Communities

Within the Anthropocene the functional diversity of coral communities is changing rapidly, putting the resilience of many coral reef ecosystems in jeopardy. A better understanding of the relationship between coral functional diversity and reef resilience could reveal practical ways to achieve increased resilience. However, manipulating coral diversity experimentally is challenging, and consequently the links between coral functional diversity, resilience, and ecosystem functioning remain obscure. We used an ecologically detailed agent-based model to conduct a virtual experiment in which functional diversity was manipulated over the entire trait space of scleractinian corals. Using an imputed trait dataset of 798 coral species and eight key functional traits, we assembled 245 functionally distinct coral communities, which we subjected to a cyclone and bleaching event. We then measured four different aspects of their resilience and quantified for each measure the respective effect of (i) the functional richness (FRic), and (ii) community-weighted means (CWM) of four types of trait: effect, resistance, recovery, and competitive. FRic represents the volume occupied by a community in the functional space, while CWM indicates the location of the communities’ centroid in the functional space. We found a significant and positive effect of FRic on three measures of resilience: communities with higher FRic recovered surface cover faster and had more rugosity and cover 10 years after the disturbances. In contrast, the resistance of the coral community—i.e., the capacity to maintain surface cover when subjected to the disturbances—was independent of FRic and was determined primarily by the CWM of resistance traits. By analyzing community dynamics and functional trade-offs, we show that FRic increases resilience via the selection and the insurance effects due to the presence of competitive species in the functional space, i.e., those highly dominant species that contribute the most to the complexity of the habitat and recover quickly from disturbances. Building from the results of our experiment and the trait correlation analysis, we discuss the potential for FRic to serve as a proxy measure of resilience and we present a strategy that can provide direction to on-going reef restoration efforts, and pave the way for sustaining coral communities in a context of rapid global change.

Catastrophic regime shifts in coral communities exposed to physical disturbances: Simulation results from object-oriented 3-dimensional coral reef model

A 3-dimensional individual-based model, the ReefModel, was developed to simulate the dynamical structure of coral reef community using object-oriented techniques. Interactions among functional groups of reef organisms were simulated in the model. The behaviours of these organisms were described with simple mechanistic rules that were derived from their general behaviours (e.g. growing habits, competitive mechanisms, response to physical disturbance) observed in natural coral reef communities. The model was implemented to explore the effects of physical disturbance on the dynamical structure of a 3-coral community that was characterized with three functional coral groups: tabular coral, foliaceous coral and massive coral. Simulation results suggest that (i) the integration of physical disturbance and differential responses (disturbance sensitivity and growing habit) of corals plays an important role in structuring coral communities; (ii) diversity of coral communities can be maximal under intermediate level of acute physical disturbance; (iii) multimodality exists in the final states and dynamic regimes of individual coral group as well as coral community structure, which results from the influence of small random spatial events occurring during the interactions among the corals in the community, under acute and repeated physical disturbances. These results suggest that alternative stable states and catastrophic regime shifts may exist in a coral community under unstable physical environment.

Modelling processes that generate and maintain coral community diversity

This study addresses why adjacent sites on coral reefs are different, why some places support so few coral species, and how human impacts are affecting coral community dynamics and ultimately diversity. The paper includes a brief review outlining what theory tells us and how that theory relates to empirical data. A metapopulation and a metacommunity model are introduced. The metapopulation model can be used to predict a species' probability of site occupancy and the metacommunity model can be used to predict the number of species supported at any one site. The models identify the primary mechanisms that generate and maintain local (10s m2–10s km2) coral diversity based on a regional (100s km2) perspective. Local diversity appears regulated by differential post-settlement mortality that in turn leads to local extinction of some species. Indeed, harsh local environments cause high levels of local extinction and these environments support few coral species.