Long-term changes in coral colony size distributions on Kenyan reefs under different management regimes and across the 1998 bleaching event

Juvenile corals are an important component of the population dynamics of corals, but little is known about the ecology and natural history of their early life-history stages. In demographic surveys, small juvenile corals are often grouped with larger and older corals or overlooked entirely due to their small size and cryptic nature. This study describes the distribution, abundance, and microhabitat of small juvenile corals, defined as post-settlement corals ≤5 mm in diameter, at Palmyra Atoll, Central Pacific. A diver-operated pulsating blue light and filter system was used to enhance innate coral fluorescence during daylight to aid in detecting small juvenile corals. Juvenile densities ranged from 0 to 59.5 m -2 and were more than 9 times higher on the fore reef (21.9 ± 0.8 m ). The highest juvenile densities were observed in the middle of the sampled range at 14 m depth on the fore reef. Juvenile corals accounted for > 31% of coral colonies in all habitats and depths, which resulted in positively skewed size-frequency distributions. The microhabitat of juvenile corals on coral rubble was best described as a convex surface covered with crustose coralline algae that lacked another coral within a 20 mm radius. This study provides basic ecology and natural history information of small juvenile corals and shows the feasibility of surveying corals ≤ ≤5 mm in diameter as a method for monitoring coral populations and assessing environmental changes on a coral reef.

Section: Discussionmentioning

confidence: 97%

Distribution, abundance, and microhabitat characterization of small juvenile corals at Palmyra Atoll

Roth

Knowlton²

2009

“…Since demographic processes such as fecundity, growth and survival are strongly correlated with colony size (Hughes & Jackson 1980), the size structure of coral populations is an important determinant of their ecological dynamics (Bak & Meesters 1998, Meesters et al 2001. Several studies have explored spatial variation in the size structure of coral populations at various depths and sites (Vermeij & Bak 2003, Adjeroud et al 2007, Victor et al 2009), but few have followed the impact of disturbances through time, examining temporal shifts in population structure (van Woesik 2000, Gilmour 2004, McClanahan et al 2008, Crabbe 2009). …”

Section: Introductionmentioning

confidence: 99%

Recolonisation of Acropora hyacinthus following climate-induced coral bleaching on the Great Barrier Reef

Linares

Pratchett²,

Coker³

2011

Given projected increases in the frequency and/or severity of climatic disturbances, the persistence of corals may be more a function of their capacity for regeneration than resistance to such episodic disturbances. If so, climate change may favour those corals that regenerate fastest following acute disturbance. The tabular coral Acropora hyacinthus is fast-growing and typically dominates shallow wave-exposed habitats on the Great Barrier Reef, but it is extremely vulnerable to climate-induced coral bleaching and other disturbances (e.g. cyclones and outbreaks of crown-of-thorns starfish). The present study explores temporal changes in percentage cover and size structure of A. hyacinthus on reefs affected by the 2001−2002 bleaching event. Annual surveys conducted at 3 mid-shelf reefs from 2008 to 2010 revealed rapid, but very patchy, recovery of A. hyacinthus. Following extensive coral loss, local cover of A. hyacinthus increased due to growth of established colonies as well as addition and subsequent growth of new colonies. At one reef, recovery was mostly due to increased abundance of small colonies, assumed to have recruited since the bleaching, whereas recovery at the 2 other study reefs (< 5 km away) was the sustained growth of established colonies. These results show that resilience of A. hyacinthus populations may be due to either recolonisation or persistence, but that, either way, these corals are well suited to rapid recovery following acute disturbance.

“…A large fish body size leads to a higher rank in the competitive hierarchy and permits the occupation of the best habitat patches (Holbrook & Schmitt 2002, Hobbs & Munday 2004. Colony size is an important life-history characteristic of corals (McClanahan et al 2008) and has an effect on the inhabiting organisms. Larger colonies generally supported larger fishes, but coral size alone did not determine host quality.…”

Section: Ecological Consequences Of Different Body Formmentioning

confidence: 99%

“…Apart from improving our understanding of factors governing the habitat preferences and resource partitioning among coral-associated fishes, the present study may help to make predictions about the consequences of coral loss and changes in coral composition (Hoegh-Guldberg et al 2007, Hughes et al 2007) and in colony size (McClanahan et al 2008) for associated organisms in future coral reefs. The diversity and structural complexity of coral microhabitats may become less as numerous factors such as coral bleaching (Baird & Marshall 2002, Wilkinson 2004 or crown-of-thorns seastar outbreaks (Moran et al 1992, Lourey et al 2000 degrade and destroy coral reefs.…”

Section: Ecological Consequences Of Different Body Formmentioning

confidence: 99%

Microhabitat characteristics influence shape and size of coral-associated fishes

Wehrberger¹,

Herler²

2014

Coral reefs provide a high diversity of habitats, including the often complex structure of reef-building corals themselves. Since these coral microhabitats are constrained spatially, specific phenotypic adaptations of associated species to the geometric structure of corals are expected. In the northern Red Sea, we investigated how the physical structure of 2 Acropora corals influences the size, shape and growth of fishes that live in these corals. Branch length and interbranch distance increased strongly and differentially with colony size in both coral species, making large colonies more suitable for larger fishes. We used traditional and geometric morphometrics to demonstrate that the 2 coral-dwelling gobies Gobiodon histrio (Valenciennes) and G. rivulatus (Rueppell) follow different ontogenetic growth patterns. Adult G. histrio show a dorsoventrally expanded body combined with a lateral compression, while the wider-bodied G. rivulatus has a smaller maximum body length. The lateral compression enables G. histrio to pass smaller interbranch distances than G. rivulatus of the same body length, as demonstrated in an experiment testing their ability to pass narrow interbranch distances. Measurements of G. histrio revealed a greater increase of body length and mass with coral colony size in Acropora digitifera than in A. gemmifera or other coral species. Outliers in growth rates of the fishes demonstrated that moving to larger corals and/or associating with a larger breeding partner benefits fish growth. Shape-related lateral body size differences provide an explanation why those fishes that are better adapted to certain host corals compete more successfully for these microhabitats. The evolution of different shapes in coral-associated fishes indicates differences in habitat specialization to reef-building corals with different geometries.