Sublethal injuries in non-marine microconchid tubeworms from the Lower Carboniferous of West Virginia,USA

More than 10,000 non-marine microconchid tubeworms (order Tentaculita) from the Lower Carboniferous (Mauch Chunk Group) of West Virginian, USA, have been inspected with respect to the occurrence of specimens having repaired injuries. The inspection showed that only nine specimens bear distinct regenerations of their tubes which constitute only 0.08% of the total specimens. This value, although much lower than that obtained from other encrusting tentaculitoid tubeworms, is very similar to that calculated before for the thousands of Early Devonian planktonic tentaculitids. This clearly indicates that sample size (specimen number) is critical for obtaining the reliable data about the proportion of regenerated vs. unaffected specimens. The sublethal injuries present in these few individuals probably resulted from failed predation, most probably by grazing fishes. However, the repaired injuries only indicate that some individuals survived but do not provide any information about the predation intensity on the group in the given paleoenvironment. Microconchids encrusted a given substrate in large quantities, so grazing fishes may have easily removed the majority of individuals, leaving no trace of predation activity in the Early Carboniferous, non-marine paleoenvironments of what is now West Virginia.     

Coral reef encruster communities and carbonate production in cryptic and exposed coral reef habitats along a gradient of terrestrial disturbance

Encrusting calcareous organisms such as bryozoans, crustose coralline algae (CCA), foraminiferans, and serpulid worms are integral components of tropical framework-building reefs. They can contribute calcium carbonate to the reef framework, stabilise the substrate, and promote larval recruitment of other framework-building species (e.g. coral recruits). The percentage cover of encrusting organisms and their rates of carbonate production (g m⁻² year⁻¹) were assessed at four sites within a coastal embayment, along a gradient of riverine influence (high-low). As the orientation and type of substrate is thought to influence recruitment of encrusting organisms, organisms recruiting to both natural (the underside of platy corals) and experimental substrates were assessed. The effect of substrate exposure under different levels of riverine influence was assessed by orientating experimental substrates to mimic cryptic and exposed reef habitats (downwards-facing vs upwards-facing tiles) at each site. Cryptic experimental tiles supported similar encruster assemblages to those recruiting to the underneath (cryptic side) of platy corals, suggesting that tiles can be used as an experimental substrate to assess encruster recruitment in reef systems. Encruster cover, in particular CCA, and carbonate production was significantly higher at low-impact (clear water), high wave energy sites when compared to highly riverine impacted (turbid water), low wave energy sites. Cryptically orientated substrates supported a greater diversity of encrusting organisms, in particular serpulid worms and bryozoans. The inverse relationships observed between riverine inputs and encrusters (total encruster cover and carbonate production) have implications for both the current and future rates and styles of reefal framework production.