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A remarkable diversity of bioerosion trace fossils is reflected by the plethora of ichnotaxa that has been proposed for these structures during the past two centuries. Bioerosion traces include microborings, macroborings, grazing traces, attachment etchings, and predation traces. They occur in calcareous, siliceous, osteic, and xylic substrates, and are known or interpreted to be produced by tracemakers as diverse as bacteria, fungi, algae, invertebrates, and vertebrates. This review presents the status quo of an inventory of all bioerosion ichnotaxa currently recognized as valid, comprising 123 ichnogenera and 339 ichnospecies, including 45 combinationes novae, the majority of which on account of fossil sponge bioerosion traces formerly grouped within the sponge biotaxon Cliona. In addition, the spelling of several ichnotaxa has to be corrected, leading to eight nomina corrigenda, and three cases of primary or secondary homonymy require establishing nomina nova, i.e., the new ichnogenus name Irhopalia replacing Rhopalia Radtke, 1991, as well as the new ichnospecies names Entobia morrisi replacing E. glomerata (Morris, 1851) and Entobia tuberculata replacing E. mammillata Bromley and D’Alessandro, 1984, respectively. Ichnotaxa of dubious or invalid nomenclatural status currently include an additional 76 ichnogenera and 157 ichnospecies. The invalid ichnogenus Ipites is herein reinstated as new ichnogenus. Considering that only four valid (and one invalid) ichnofamilies had previously been established for bioerosion ichnotaxa, we here introduce a suite of 14 additional ichnofamilies: Gastrochaenolitidae, Talpinidae, Entobiaidae, Planobulidae, Ichnoreticulinidae, Saccomorphidae, Centrichnidae, Renichnidae, Podichnidae, Gnathichnidae, Circolitidae, Oichnidae, Belichnidae, and Machichnidae. During the past five decades, the number of valid bioerosion ichnotaxa has more than quadrupled, reflecting a boost in bioerosion research, but also indicating the need for ichnotaxonomic consolidation in concert with a revision of key ichnogenera. In this context, the aim of this overview is to call for feedback from the research community in order to foster completeness of this list and to provide ichnotaxonomic stability. Furthermore, we want to raise awareness of the existence of the listed ichnotaxa, many of which obviously have remained unconsidered or forgotten for a long time.

Ocean warming and acidification threaten the future growth of coral reefs. This is because the calcifying coral reef taxa that construct the calcium carbonate frameworks and cement the reef together are highly sensitive to ocean warming and acidification. However, the global-scale effects of ocean warming and acidification on rates of coral reef net carbonate production remain poorly constrained despite a wealth of studies assessing their effects on the calcification of individual organisms. Here, we present global estimates of projected future changes in coral reef net carbonate production under ocean warming and acidification. We apply a meta-analysis of responses of coral reef taxa calcification and bioerosion rates to predicted changes in coral cover driven by climate change to estimate the net carbonate production rates of 183 reefs worldwide by 2050 and 2100. We forecast mean global reef net carbonate production under representative concentration pathways (RCP) 2.6, 4.5, and 8.5 will decline by 76, 149, and 156%, respectively, by 2100. While 63% of reefs are projected to continue to accrete by 2100 under RCP2.6, 94% will be eroding by 2050 under RCP8.5, and no reefs will continue to accrete at rates matching projected sea level rise under RCP4.5 or 8.5 by 2100. Projected reduced coral cover due to bleaching events predominately drives these declines rather than the direct physiological impacts of ocean warming and acidification on calcification or bioerosion. Presently degraded reefs were also more sensitive in our analysis. These findings highlight the low likelihood that the world’s coral reefs will maintain their functional roles without near-term stabilization of atmospheric CO₂ emissions.

Marine sponges are set to become more abundant in many near-future oligotrophic environments, where they play crucial roles in nutrient cycling. Of high importance is their mass turnover of dissolved organic matter (DOM), a heterogeneous mixture that constitutes the largest fraction of organic matter in the ocean and is recycled primarily by bacterial mediation. Little is known, however, about the mechanism that enables sponges to incorporate large quantities of DOM in their nutrition, unlike most other invertebrates. Here, we examine the cellular capacity for direct processing of DOM, and the fate of the processed matter, inside a dinoflagellate-hosting bioeroding sponge that is prominent on Indo-Pacific coral reefs. Integrating transmission electron microscopy with nanoscale secondary ion mass spectrometry, we track 15N- and 13C-enriched DOM over time at the individual cell level of an intact sponge holobiont. We show initial high enrichment in the filter-feeding cells of the sponge, providing visual evidence of their capacity to process DOM through pinocytosis without mediation of resident bacteria. Subsequent enrichment of the endosymbiotic dinoflagellates also suggests sharing of host nitrogenous wastes. Our results shed light on the physiological mechanism behind the ecologically important ability of sponges to cycle DOM via the recently described sponge loop.

Bioerosion on inshore reefs is expected to increase with global climate change reducing reef stability and accretionary potential. Most studies investigating bioerosion have focused on external grazers, such as parrotfish and urchins, whose biomass is more easily measured. Yet, cryptic endolithic bioeroders such as macroboring (worms, sponges and bivalves) and microboring taxa (fungus and algae) have the potential to be the dominant source of reef erosion, especially among inshore reef systems exposed to increased nutrient supply. We measured bioerosion rates of bioeroder functional groups (microborers, macroborers, and grazers), and their response to environmental parameters (temperature, light, turbidity, chlorophyll a), as well as habitat variables (coral cover, turfing algae, macroalgae) across two inshore turbid reefs of north Western Australia. Total bioerosion rates were low (0.163 ± 0.012 kg m−2 year−1) likely due to low light and nutrient levels. Macroborers were the dominant source of bioerosion and were positively correlated with turfing algae cover, highlighting the role of turf-grazing fish on endolithic bioerosion rates. Overall low bioerosion rates suggest that despite the reduced coral cover and carbonate production, these reefs may still maintain positive reef accretion rates, at least under current environmental conditions. However, an improved understanding of relationships between environmental drivers, habitat and grazing pressure with bioeroding communities is needed to improve predictions of reef carbonate loss with future climate change.

Coral reefs are in global decline. Reversing this trend is a primary management objective but doing so depends on understanding what keeps reefs in desirable states (ie “functional”). Although there is evidence that coral reefs thrive under certain conditions (eg moderate water temperatures, limited fishing pressure), the dynamic processes that promote ecosystem functioning and its internal drivers (ie community structure) are poorly defined and explored. Specifically, despite decades of research suggesting a positive relationship between biodiversity and ecosystem functioning across biomes, few studies have explored this relationship in coral reef systems. We propose a practical definition of coral reef functioning, centered on eight complementary ecological processes: calcium carbonate production and bioerosion, primary production and herbivory, secondary production and predation, and nutrient uptake and release. Connecting research on species niches, functional diversity of communities, and rates of the eight key processes can provide a novel, quantitative understanding of reef functioning and its dependence on coral reef communities that will chart the transition of coral reefs in the Anthropocene. This will contribute urgently needed guidance for the management of these important ecosystems.

Biotic connectivity between ecosystems can provide major transport of organic matter and nutrients, influencing ecosystem structure and productivity 1 , yet the implications are poorly understood owing to human disruptions of natural flows 2 . When abundant, seabirds feeding in the open ocean transport large quantities of nutrients onto islands, enhancing the productivity of island fauna and flora 3 , 4 . Whether leaching of these nutrients back into the sea influences the productivity, structure and functioning of adjacent coral reef ecosystems is not known. Here we address this question using a rare natural experiment in the Chagos Archipelago, in which some islands are rat-infested and others are rat-free. We found that seabird densities and nitrogen deposition rates are 760 and 251 times higher, respectively, on islands where humans have not introduced rats. Consequently, rat-free islands had substantially higher nitrogen stable isotope (δ 15 N) values in soils and shrubs, reflecting pelagic nutrient sources. These higher values of δ 15 N were also apparent in macroalgae, filter-feeding sponges, turf algae and fish on adjacent coral reefs. Herbivorous damselfish on reefs adjacent to the rat-free islands grew faster, and fish communities had higher biomass across trophic feeding groups, with 48% greater overall biomass. Rates of two critical ecosystem functions, grazing and bioerosion, were 3.2 and 3.8 times higher, respectively, adjacent to rat-free islands. Collectively, these results reveal how rat introductions disrupt nutrient flows among pelagic, island and coral reef ecosystems. Thus, rat eradication on oceanic islands should be a high conservation priority as it is likely to benefit terrestrial ecosystems and enhance coral reef productivity and functioning by restoring seabird-derived nutrient subsidies from large areas of ocean. Productivity of coral reefs is enhanced near islands with no invasive rats, as populations of seabirds, which transfer nitrogen from deeper areas of ocean to the nearshore waters via their guano, are much larger than on rat-infested islands.

A microcosm experiment was conducted at two phases in order to investigate the ability of indigenous consortia alone or bioaugmented to degrade weathered polystyrene (PS) films under simulated marine conditions. Viable populations were developed on PS surfaces in a time dependent way towards convergent biofilm communities, enriched with hydrocarbon and xenobiotics degradation genes. Members of Alphaproteobacteria and Gammaproteobacteria were highly enriched in the acclimated plastic associated assemblages while the abundance of plastic associated genera was significantly increased in the acclimated indigenous communities. Both tailored consortia efficiently reduced the weight of PS films. Concerning the molecular weight distribution, a decrease in the number-average molecular weight of films subjected to microbial treatment was observed. Moreover, alteration in the intensity of functional groups was noticed with Fourier transform infrared spectrophotometry (FTIR) along with signs of bio-erosion on the PS surface. The results suggest that acclimated marine populations are capable of degrading weathered PS pieces.

Invertebrate bioerosion on fossil bone can contribute to reconstructions of benthic taxonomic assemblages and inform us about oxygenation levels, water depth and exposure time on the seafloor prior to burial. However, these traces are not commonly described in the fossil record. To date, there have been only 13 published studies describing a total of 15 instances of invertebrate bioerosion on marine reptile fossil bones from the Mesozoic globally. We surveyed the collections of several UK museums with substantial occurrences of Mesozoic marine reptiles for evidence of invertebrate bioerosion. Here, we document 153 specimens exhibiting 171 newly recorded instances of invertebrate bioerosion on Jurassic and Cretaceous marine reptile bones. Several major bioeroding taxonomic groups are identified. Within the geological strata of the United Kingdom, there is a higher prevalence of bioerosion in the Cretaceous relative to the Jurassic, despite greater sampling of specimens from the Jurassic. Although biotic turnover and food web restructuring might have played a role, potentially pertaining to heightened productivity during the later stages of the Mesozoic Marine Revolution, we consider it more likely that this temporal change corresponds to differences in depositional environment and taphonomic history between the sampled rock units. In particular, the Cretaceous deposits are characterized by heightened oxygenation levels relative to their Jurassic counterparts, as well as reworking, which would have allowed two phases of bioerosion. A spatiotemporally broader dataset on invertebrate bioerosion on vertebrate bone will be important in further testing this and other hypotheses.

Carbon burial is increasingly valued as a service provided by threatened vegetated coastal habitats. Similarly, shellfish reefs contain significant pools of carbon and are globally endangered, yet considerable uncertainty remains regarding shellfish reefs' role as sources (+) or sinks (−) of atmospheric CO2. While CO2 release is a by-product of carbonate shell production (then burial), shellfish also facilitate atmospheric-CO2 drawdown via filtration and rapid biodeposition of carbon-fixing primary producers. We provide a framework to account for the dual burial of inorganic and organic carbon, and demonstrate that decade-old experimental reefs on intertidal sandflats were net sources of CO2 (7.1 ± 1.2 MgC ha−1 yr−1 (µ ± s.e.)) resulting from predominantly carbonate deposition, whereas shallow subtidal reefs (−1.0 ± 0.4 MgC ha−1 yr−1) and saltmarsh-fringing reefs (−1.3 ± 0.4 MgC ha−1 yr−1) were dominated by organic-carbon-rich sediments and functioned as net carbon sinks (on par with vegetated coastal habitats). These landscape-level differences reflect gradients in shellfish growth, survivorship and shell bioerosion. Notably, down-core carbon concentrations in 100- to 4000-year-old reefs mirrored experimental-reef data, suggesting our results are relevant over centennial to millennial scales, although we note that these natural reefs appeared to function as slight carbon sources (0.5 ± 0.3 MgC ha−1 yr−1). Globally, the historical mining of the top metre of shellfish reefs may have reintroduced more than 400 000 000 Mg of organic carbon into estuaries. Importantly, reef formation and destruction do not have reciprocal, counterbalancing impacts on atmospheric CO2 since excavated organic material may be remineralized while shell may experience continued preservation through reburial. Thus, protection of existing reefs could be considered as one component of climate mitigation programmes focused on the coastal zone.

The remote northernmost Galápagos Islands, Darwin and Wenman, exhibited well-developed coral communities in 1975, which were severely degraded during the 1982–1983 El Niño warming event. Mapping of the coral reef at Darwin, herein Wellington Reef, shows it presently to be the largest known structural reef in the Galápagos. It consists of numerous 1- to 3-m-high Porites framework towers or stacks and overlies a carbonate (coral/calcareous sediments) basement. Pre-disturbance Wellington Reef was constructed chiefly by Porites lobata and Pocillopora elegans , and Wenman coral cover was dominated by Pavona clavus and Porites lobata . Subsequent surveys in 2012 have demonstrated robust recovery in spite of ENSO thermal shock events, involving both high and low stressful temperatures that have caused tissue bleaching and mortality. No losses of coral species have been observed. Radiocarbon dating of 1- to 3-m-high poritid framework stacks, from their peaks to bases, revealed modern ages of up to 690 yr. Incremental stack growth rates ranged from 0.15–0.39 to 1.04–2.40 cm yr −1 . The former are equivalent to framework accretion rates of 1.5–3.9 m Kyr −1 , the latter to coral skeletal growth rates of 1.0–2.4 cm yr −1 . Coral recovery in the central and southern Galápagos has been nonexistent to low compared with the northern islands, due chiefly to much higher population densities and destructive grazing pressure of the echinoid Eucidaris galapagensis . Thus, coral reef resistance to ENSO perturbations and recovery potential in the Galápagos are influenced by echinoid bioerosion that varies significantly among islands.