Colony Decline Research Articles

Precision Monitoring of Honey Bee (Hymenoptera: Apidae) Activity and Pollen Diversity during Pollination to Evaluate Colony Health.

Certain crops depend upon pollination services for fruit set, and, of these, almonds are of high value for Australia. Stressors, such as diseases, parasites, pesticides, and nutrition, can contribute to honey bee Apis mellifera L. colony decline, thereby reducing bee activity and pollination efficiency. In Australia, field studies are required to monitor honey bee health and to ascertain whether factors associated with colony decline are impacting hives. We monitored honey bee colonies during and after pollination services of almond. Video surveillance technology was used to quantify bee activity, and bee-collected pollen was periodically tested for pesticide residues. Plant species diversity was also assessed using DNA metabarcoding of the pollen. Results showed that bee activity increased in almond but not in bushland. Residues detected included four fungicides, although the quantities were of low risk of oral toxicity to bees. Floral diversity was lower in the pollen collected by bees from almonds compared to bushland. However, diversity was higher at the onset and conclusion of the almond bloom, suggesting that bees foraged more widely when availability was low. Our findings suggest that commercial almond orchards may sustain healthier bee colonies compared to bushland in early spring, although the magnitude of the benefit is likely landscape-dependent.

Experts’ opinions on threats to Leach’s Storm-Petrels ( Hydrobates leucorhous ) across their global range

Seabirds are declining globally, though the threats they face differ among and within species and populations. Following substantial population declines at several breeding colonies, Leach’s Storm-Petrel (<em>Hydrobates leucorhous</em>) was uplisted from Least Concern to Vulnerable by the International Union for Conservation of Nature (IUCN) in 2016. Reasons for these declines are unclear, and it is important to identify threats the species faces across its global breeding range to guide research directions and inform conservation efforts. We solicited feedback from 37 Leach’s Storm-Petrel scientific experts from eight countries on the importance of different threats facing the species on land and at sea. Perceived threats to extant colonies varied spatially, with a consensus within regions for main threats. Most researchers agreed that the main threats at or near colonies are avian and mammalian predators and onshore light attraction. At-sea threats have been less studied and were harder to identify and rank, but include offshore lights and structures, spatial shifts in prey, and contaminants. Climate change was not listed specifically because of its multifaceted repercussions, but several perceived threats are linked to climate change. Globally, introduction of mammalian predators is an overarching driver of seabird colony decline or extirpation; thus biosecurity must be considered an important measure for the conservation of storm-petrels. In addition, filling knowledge gaps and implementing a series of regionally relevant and targeted strategies that lead to small but cumulative conservation successes may be the best approach for this species.

Risk assessment of honey bee stressors based on in silico analysis of molecular interactions.

A global decline of the honey bee Apis mellifera has been observed in the last decades. This pollinator plays a fundamental role in food production and the economy in Europe. The decline of honey bee colonies is linked to several stressors, including pesticides. The current pesticide risk assessment of honey bees in Europe focuses on lethal effects and lacks reflection on sublethal effects. A better understanding of the consequences that exposure to these chemicals has on honey bees is still needed. In this context, the aim of this European Food Risk Assessment Fellowship Programme fellowship project has been to use in silico methodologies, such as virtual screening, as a first step to identify possible interactions at the molecular level between A. mellifera proteins and pesticide ligands. For this purpose, a docking study of the proteins from A. mellifera and pesticide ligands extracted from online databases has been performed by using the software Autodock Vina. The results obtained were a ranking based on the predicted affinity of the pesticides for specific and non-specific binding sites on bee macromolecules. These results were compared with data obtained from the literature and linked to potential sublethal effects. Finally, a risk assessment analysis of the identified molecular stressors of honey bees was performed. The results of this study are considered a starting point to identify new sources of possible stress for honey bees and thereby contribute to the overall understanding of the honey bee decline.

Impact of demographic variability on the disease dynamics for honeybee model.

For the last few years, annual honeybee colony losses have been center of key interest for many researchers throughout the world. The spread of the parasitic mite and its interaction with specific honeybee viruses carried by Varroa mites has been linked to the decline of honeybee colonies. In this investigation, we consider honeybee-virus and honeybee-infected mite-virus models. We perform sensitivity analysis locally and globally to see the effect of the parameters on the basic reproduction number for both models and to understand the disease dynamics in detail. We use the continuous-time Markov chain model to develop and analyze stochastic epidemic models corresponding to both deterministic models. By using the disease extinction process, we compare both deterministic and stochastic models. We have observed that the numerically approximated probability of disease extinction based on 30 000 sample paths agrees well with the calculated probability using multitype branching process approximation. In particular, it is observed that the disease extinction probability is higher when infected honeybees spread the disease instead of infected mites. We conduct a sensitivity analysis for the stochastic model also to examine how the system parameters affect the probability of disease extinction. We have also derived the equation for the expected time required to reach disease-free equilibrium for stochastic models. Finally, the effect of the parameters on the expected time is represented graphically.

Natural processes influencing pollinator health.

Evidence from the last few decades indicates that pollinator abundance and diversity are at risk, with many species in decline. Anthropogenic impacts have been the focus of much recent work on the causes of these declines. However, natural processes, from plant chemistry, nutrition and microbial associations to landscape and habitat change, can also profoundly influence pollinator health. Here, we argue that these natural processes require greater attention and may even provide solutions to the deteriorating outlook for pollinators. Existing studies also focus on the decline of individuals and colonies and only occasionally at population levels. In the light of this we redefine pollinator health and argue that a top-down approach is required focusing at the ecological level of communities. We use examples from the primary research, opinion and review articles published in this special issue to illustrate how natural processes influence pollinator health, from community to individuals, and highlight where some of these processes could mitigate the challenges of anthropogenic and natural drivers of change.This article is part of the theme issue ‘Natural processes influencing pollinator health: from chemistry to landscapes’.

Characterisation of thymol effects on RDL receptors from the bee parasite Varroa destructor

A major contributor to bee colony decline is infestation with its most devastating pest, the mite Varroa destructor. To control these mites, thymol is often used, although how it achieves this is not understood. One well-documented action of thymol is to modulate GABA-activated ion channels, which includes insect RDL receptors, a known insecticidal target. Here we have cloned two Varroa RDL subunits, one of which is similar to the canonical RDL subunit, while the other has some differences in M4, and, to a lesser extent, M2 and its binding site loops. Expression of this unusual RDL receptor in Xenopus oocytes reveals GABA-activated receptors, with an EC50 of 56 μM. In contrast to canonical RDL receptors, thymol does not enhance GABA-elicited responses in this receptor, and concentration response curves reveal a decrease in GABA Imax in its presence; this decrease is not seen when similar data are obtained from Apis RDL receptors. We conclude that an M2 T6′M substitution is primarily responsible for the different thymol effects, and suggest that understanding how and where thymol acts could assist in the design of novel bee-friendly miticides.

Uwikłani w opowieści: o kolonialnych spotkaniach, emigracji i wizji Afryki Wschodniej w Desertion Adbulrazaka Gurnaha

The article offers an analysis of colonialism, immigration, and the representation of East Africa in Desertion (2005) by Nobel-Prize winner Abdulrazak Gurnah. By analyzing the complex structure of the novel, the article demonstrates that its protagonists are implicated in multiple stories, which only appear to be incompatible, but in reality are deeply entangled. Applying a variety of postcolonial theories, I focus on Gurnah’s representation of the colonial encounter at the end of the 19th century in British East Africa. I show that the colonizers’ attitudes in the novel vary from an aggressive perspective on colonial conquest, through to the belief in the legitimacy of the imperial mission, to an ideology which Mary Louise Pratt defines in terms of anti-conquest and reciprocity. However, their uncontrollable, often somatic reactions, illustrate the ambivalence of colonial discourse and foreshadow the decline of colonialism. The article also argues that Gurnah’s vision of local interactions in East Africa at the turn of the 20th century is particularly complex and that the writer proposes cosmopolitan ethics. Yet, at the same time, Gurnah does not idealize East Africa and depicts prejudice and discrimination, particularly in relation to women of mixed parentage. Furthermore, the article discusses the cultural shock of the immigrant figure and the phenomena of mimicry and (de)colonization of the mind in Gurnah’s novel. Finally, it shows how Gurnah questions the concept of racial divisions, demonstrating their harmful effects in the 1960s both in Britain and in Zanzibar. &nbsp; Projekt został sfinansowany ze środków Narodowego Centrum Nauki, przyznanych na podstawie decyzji numer DEC: 2019/33/B/HS2/00019. &nbsp; Projekt został sfinansowany ze środków Narodowego Centrum Nauki, przyznanych na podstawie decyzji numer DEC: 2019/33/B/HS2/00019.

Impact of Neonicotinoid Insecticides on the Foraging Activity of Indian Honey Bee, Apiscerana indica (Fab.) in the Cotton Ecosystem

Indian honey bees are the important managed pollinators of several agricultural and horticultural crops in India. At present, bee colony decline is the biggest crisis amongbeekeepers. The use of neonicotinoid insecticides is considered the prime factor, and they were found to cause a direct impact on bees by mortality and indirectly impair the foraging behavior of bees. Hence, the study aimed to assess the impact of neonicotinoids on the foraging activity of Indian honey bees. The neonicotinoids viz., imidacloprid 17.8 SL, clothianidin 50 WDG, thiamethoxam 25 WG, and thiacloprid 21.7 SC, along with organophosphate dimethoate 30 EC (chemical check) and control (no spray) were sprayed at field recommended doses on cotton crop. Foraging activity of the bees,viz.,incoming foragers with nectar and pollen load and outgoing foragers were counted at the hive entrance during the morning (09.00-11.00), afternoon (13.00-15.00), and evening (16.00-18.00) hours of the day. The data were recorded at pre-treatment count and posttreatment count on different day intervals viz., 1DAS, 3DAS, 7DAS, and 15DAS. The mean number of incoming nectar, pollen foragers, and outgoing foragers were recorded to be maximum in control than neonicotinoid-treated plots. Hence, the reduction in foraging activity may lead to areduction in the food storage area and brood area ultimately lesseningthe overall colony growth. It’s always better to avoid spraying cotton crop during the flowering period using neonicotinoids to dodge the residues even though cotton is not a food crop; meanwhile, it will safeguard the pollinators.

Synergetic Inactivation Mechanism of Protocatechuic Acid and High Hydrostatic Pressure against Escherichia coli O157:H7.

With the wide application of high hydrostatic pressure (HHP) technology in the food industry, safety issues regarding food products, resulting in potential food safety hazards, have arisen. To address such problems, this study explored the synergetic bactericidal effects and mechanisms of protocatechuic acid (PCA) and HHP against Escherichia coli O157:H7. At greater than 200 MPa, PCA (1.25 mg/mL for 60 min) plus HHP treatments had significant synergetic bactericidal effects that positively correlated with pressure. After a combined treatment at 500 MPa for 5 min, an approximate 9.0 log CFU/mL colony decline occurred, whereas the individual HHP and PCA treatments caused 4.48 and 1.06 log CFU/mL colony decreases, respectively. Mechanistically, membrane integrity and morphology were damaged, and the permeability increased when E. coli O157: H7 was exposed to the synergetic stress of PCA plus HHP. Inside cells, the synergetic treatment additionally targeted the activities of enzymes such as superoxide dismutase, catalase and ATPase, which were inhibited significantly (p ≤ 0.05) when exposed to high pressure. Moreover, an analysis of circular dichroism spectra indicated that the synergetic treatment caused a change in DNA structure, which was expressed as the redshift of the characteristic absorption peak. Thus, the synergetic treatment of PCA plus HHP may be used as a decontamination method owing to the good bactericidal effects on multiple targets.

A scientific note of pest-insects associated with stingless bee hive Melipona eburnea in the Ecuadorian Amazon Region

Bees are the primary pollinators in nature. However, climate change, excessive use of fertilizers and invasive species have caused the decline of bee colonies. Therefore, this study aimed to analyze the presence of pests in colonies of Melipona eburnea. For this, the colonies of M. eburnea were examined during the honey extraction process. We found 4 different pests associated with the physical conditions of colonies and the fragile defense of the bees against the invaders. In conclusion, this report of the presence of pests is to alert researchers and meliponicultures to prevent the decline of stingless bees.

Pengolahan Limbah Cair Industri dari PT. Sier Menggunakan Metode Elektroflotasi (EF)

One of the methods for treating industrial waste is using the electro-flotation (EF) method. In this study, the EF method used requires stainless steel as the anode and aluminum as the cathode. Industrial wastewater treated using the EF method comes from PT. Surabaya Rungkut Industrial Estate (SIER). Liquid waste is put into the EF basin, then the power supply is turned on and then the voltage and contact time are adjusted. After the EF process, the treated wastewater was sampled in a certain amount to measure the value of Chemical Oxygen Demand (COD), Total Suspended Solid (TSS) and the number of bacterial colonies. Based on the calculation, the result shows that with an electric voltage of 32.5 volts and a contact time of 60 minutes, the result is the largest decrease in COD and TSS values. COD decreased from 236.66 mg / L to 24.56 mg / L or 90%, TSS decreased from 187 mg / L to 34.33 mg / L or 81.64%. While the decline in bacterial colonies from 4,7.104 to 4,03.103 or 91,42% decrease at the mains voltage of 19 volts and contact time for 20 minutes.

Beekeeping Production System, Challenges, and Opportunities in Selected Districts of South Wollo Zone, Amhara, Ethiopia

The study was conducted in Tehulederie, Kalu, and Dessie Zuria districts of South Wollo Zone, Amhara, Ethiopia, to assess the current beekeeping production system with available opportunities and challenges facing the beekeeping subsector. The districts were purposively selected based on potential and accessibility and then stratified into lowland, midland, and highland. In total, 135 beekeepers, of which 126 were males and 9 were females, were interviewed using a pretested semistructured questionnaire. The result revealed that beekeeping is actively practiced by the community regardless of age and sex. Three beekeeping production systems, that is, traditional, transitional, and movable frame hive, have been identified, accounting for 80%, 4%, and 16%, respectively. More than 80% of total bee colonies are managed being placed in the backyard. Besides, the study indicated that about 79% of the beekeepers keep bees primarily for income generation and home consumption. According to this study, the average bee colony holding size is 5.13 per a beekeeper. Also, this study identified that the swarm catching method is the major source of bee colony accounting for more than 45% to start beekeeping and 76% to increase existing colony number. Bee colony decline, absconding and swarming, honeybee pests and predators, and lack of training and extension were identified as major beekeeping challenges in the study areas. This study identified the beekeeping production system, opportunities, and challenges of the study areas and has significantly contributed to our knowledge and identified lack of extension and training as intervention areas. Therefore, practical beekeeping training and extension should get primary emphasis to combat the existing challenges.

Natural extracts as potential control agents for Nosema ceranae infection in honeybees, Apis mellifera

Nosema disease is one factor that can cause colony decline in honeybees (Apis mellifera L.) worldwide. Nosema ceranae has outcompeted Nosema apis in the Western honeybee (A. mellifera) which is its original host. Fumagilin is an effective antibiotic treatment to control Nosema infection but currently it is forbidden in many countries. In this study, 12 plant extracts were evaluated for their toxicity to adult bees and antimicrosporidian activity under laboratory and field conditions. N. ceranae-infected adult bees were fed ad libitum with 50% sucrose solution containing 1% and 5% (w/v) of each plant extract. Bee mortality in N. ceranae-infected groups fed with plant extracts was higher than that in the control group treated with fumagilin. The results demonstrated that 9 of 12 extracts had high antimicrosporidian activity against N. ceranae and their efficacies were comparable to fumagilin. Spore reduction in infected bees was 4–6 fold less after extract treatment. Following laboratory screening, Annona squamosa, Ocimum basilicum, Psidium guajava and Syzygium jambos were tested in honeybee colonies. Plant extracts of 2% concentration (w/v) inhibited the development of Nosema spores after 30 days of treatment. At the end of experiment (90 days), spores in the plant extract treated groups were lower than in group treated with fumagilin but there was no significant difference. Although, extracts tested in this study showed high toxicity to bee in laboratory cages, they did not show negative affects on bees under whole colony conditions. Therefore, the effectiveness of plant extracts tested in this study was notable and warrants further study as potential Nosema control agents in honey bees. Plant extracts would offer a non-antibiotic alternative for Nosema control and help reduce the overuse of antibiotics in livestock.

Microplastic Polystyrene Ingestion Promotes the Susceptibility of Honeybee to Viral Infection

Microplastics (MPs) are an emerging threat to ecological conservation and biodiversity; however, little is known of the types and possible impacts of MPs in pollinators. To examine whether MPs were present in honeybees, we analyzed the honeybee samples collected in fields from six provinces in China. Four types MPs were identified in honeybee including polystyrene (PS) by Raman spectroscopic analysis, and these plastic polymers were detected in 66.7% bee samples. Then, we assessed the physical and biological impacts of PS of three sizes (0.5, 5, and 50 μm) on bees for 21 days. Next, we measured how the presence of PS affected the Israeli acute paralysis virus proliferation, a small RNA virus associated with bee colony decline. Experimental evidence showed that a large mass of PS was ingested and accumulated within the midgut and enhanced the susceptibility of bees to viral infection. Not only histological analysis showed that PS, especially 0.5 μm PS, damaged the midgut tissue and was subsequently transferred to the hemolymph, trachea, and Malpighian tubules, but also qPCR and transcriptomic results indicated that genes correlated with membrane lipid metabolism, immune response, detoxification, and the respiratory system were significantly regulated after PS ingestion. Our results highlight neglected MP contamination to the bees, a pollination ecosystem stressed by the anthropogenic pollution, and have implications for human health via ingestion of bee products.

Enzymatic responses in the head and midgut of Africanized Apis mellifera contaminated with a sublethal concentration of thiamethoxam

The increasing use of insecticides, promoted by the intensification of agriculture, has raised concerns about their influence on the decline of bee colonies, which play a fundamental role in pollination. Thus, it is fundamental to elucidate the effects of insecticides on bees. This study investigated the damage caused by a sublethal concentration of thiamethoxam - TMX (0.0227 ng/μL of feed) in the head and midgut of Africanized Apis mellifera, by analyzing the enzymatic biomarkers, oxidative stress, and occurrence of lipid peroxidation. The data showed that the insecticide increased acetylcholinesterase activity (AChE) and glutathione-S-transferase (GST), whereas carboxylesterase (CaE3) activity decreased in the heads. Our results indicate that the antioxidant enzymes were less active in the head because only glutathione peroxidase (GPX) showed alterations. In the midgut, there were no alkaline phosphatase (ALP) or superoxide dismutase (SOD) responses and a decrease in the activity of CaE was observed. Otherwise, there was an increase in GPX, and the TBARS (thiobarbituric acid reactive substances) assay also showed differences in the midgut. The TBARS (thiobarbituric acid reactive substances) assay also showed differences in the midgut. The results showed enzymes such as CaE3, GST, AChE, ALP, SOD, and GPX, as well as the TBARS assay, are useful biomarkers on bees. They may be used in combination as a promising tool for characterizing bee exposure to insecticides.

An Investigation of Honey Bee Viruses Prevalence in Managed Honey Bees (Apis mellifera and Apis cerana) Undergone Colony Decline

Objective: In the absence of known clinical symptoms, viruses were considered to be the most probable key pathogens of honey bee. Therefore, the aim of this study was to investigate the prevalence and distribution of honey bee viruses in managed Apis mellifera and Apis cerana in China. Methods: We conducted a screening of 8 honey bee viruses on A. mellifera and A. cerana samples collected from 54 apiaries from 13 provinces in China using RT-PCR. Results: We found that the types and numbers of viral species significantly differed between A. mellifera and A. cerana. Black Queen Cell Virus (BQCV), Chronic Bee Paralysis Virus (CBPV), Apis mellifera filamentous virus (AmFV), and Kakugo virus (DWV-A/KV) were the primary viruses found in A. mellifera colonies, whereas Chinese Sacbrood Bee Virus (CSBV) and Sacbrood Bee Virus (SBV) were the primary viruses found in A. cerana. The percentage infection of BQCV and CSBV were 84.6% and 61.6% in all detected samples. We first detected the occurrences of Varroa destructor virus-1 (VDV-1 or DWV-B) and DWV-A/KV in China but not ABPV in both A. mellifera and A. cerana. Conclusion: This study showed that BQCV and CSBV are the major threat to investigated A. mellifera and A. cerana colonies.

Genetic variability and phylogenetic analysis among strains of deformed wing virus infesting honey bees and other organisms.

Various viruses can infect honey bees, but deformed wing virus (DWV) is considered the most dangerous virus to them and has role in the sudden decline of bee colonies. This virus has different strains; however, there are no available studies to compare the characteristics of these strains utilizing bioinformatics. In this study, 27 strains of deformed wing virus were analyzed based on their sequences and their genetic relationships. Also, some primers were designed and tested to identify their ability to separate DWV strains. The percentages range from 28.99% to 29.63%, 22.28% to 22.78%, 15.73% to 16.28%, and 31.71% to 32.86% for nucleotides A, G, C, and T, respectively in all strains. The numbers of polymorphic sites as well as nucleotide diversity were highly similar in all strains. Statistical analyses generally showed the absence of high variations between sequences. Also, the phylogenetic tree classified strains into three groups. The network between strains of each group was established and discussed based on their geographical locations. Two groups contained strains from USA and Europe while one group contained strains from Asia. Rapid variations and mutations in the sequences of DWV were suggested. Notably, genetic studies on DWV are lacking in some geographical regions. The variations between strains detected in honey bees and other organisms were discussed. Four primers were designed and tested beside two reference primers. One of the designed primers showed the best results in binding with all DWV strains except one.

Foraging Activities of Honeybees (Apis mellifera L.) and Bumblebees (Bombus terrestris L.) on Passionfruit (Passiflora edulis f. edulis) Flower and their Pollination Effects

We studied the activity and pollination effects of insect pollinators (Apis mellifera and Bombus terrestris) in passionfruit pollination to investigate the possibility of insect pollination in greenhouse-cultivated passionfruit. The climatic condition inside the greenhouse during the flowering of passionfruit, bee traffics and flower visit duration of two species were measured. In addition, the pollination effect was determined by investigating the physical characteristics of fruits according to each pollination methods. The bee traffic and foraging activity of A. mellifera were 3.6 and 7 times greater than those of B. terrestris, respectively. However, when this result was converted into a percentage to colony size, the ratio of B. terrestris was 19.1, and was 10.2 times higher than that of A. mellifera. In addition, the activity of A. mellifera was affected by the illumination level (R=0.593) and ultraviolet rays (R=0.647), but the activity of B. terrestris was less affected by light. Therefore, we considered B. terrestris to be more suitable for the pollination of passionfruit than A. mellifera. Regarding the pollination effect, there was no difference between the two insect pollinators; however, better fruit quality was observed with insect pollinators than with artificial pollination. Certain problems should be addressed when using an insect pollinator directly for the pollination of passionfruit. First, pollen robbing caused by the differences between flowering start time and bee activity start time should be considered. Second, the low pollination efficiency because of the presence of extrafloral nectaries in passionfruit should be considered. Lastly, the pollination effect caused by the colony decline because of the long duration of pollination should be factored in. If these problems are solved by controlling the activity time of the foraging bees, increasing the pollinator density by 30%, and adding or managing the bee colony, insect pollinators could be effectively used for passionfruit pollination.

Contract labor migration as an agent of revolutionary change in the Danish West Indies

ABSTRACT The following article examines the post-emancipation labor contract migration (1848–1917) from the eastern Caribbean islands to the Danish West Indies. This migration was intended to fill a labor vacuum caused by the emancipation of slaves in 1848. The migrant laborers technically had fewer restrictions than slaves did, but the planter class used the restrictive Labor Act of 1849 at their disposal to have total control over the laborers. During this period, the positions of the planter and laboring classes became polarized. The former wanted total control of labor, while the latter wanted fair treatment in the contractual labor engagements. The result was that the labor class, with their festering problems, formed a strong camaraderie among themselves. Migrant and native challenged their working and living conditions. Their dissatisfaction eventually manifested in riots, locally known as Fireburn or Fyah Bun, which resulted in the destruction of property and the loss of life. The riots, however, changed local working conditions and eventually accelerated the decline of Danish colonialism on St. Croix, St. John, and St. Thomas. These revolutionary events and agents of change created a new platform for how labor relations would be conducted in the Danish West Indies – a platform that was created from the position of the laboring class.

Long-term shifts in the colony size structure of coral populations along the Great Barrier Reef.

The age or size structure of a population has a marked influence on its demography and reproductive capacity. While declines in coral cover are well documented, concomitant shifts in the size-frequency distribution of coral colonies are rarely measured at large spatial scales. Here, we document major shifts in the colony size structure of coral populations along the 2300 km length of the Great Barrier Reef relative to historical baselines (1995/1996). Coral colony abundances on reef crests and slopes have declined sharply across all colony size classes and in all coral taxa compared to historical baselines. Declines were particularly pronounced in the northern and central regions of the Great Barrier Reef, following mass coral bleaching in 2016 and 2017. The relative abundances of large colonies remained relatively stable, but this apparent stability masks steep declines in absolute abundance. The potential for recovery of older fecund corals is uncertain given the increasing frequency and intensity of disturbance events. The systematic decline in smaller colonies across regions, habitats and taxa, suggests that a decline in recruitment has further eroded the recovery potential and resilience of coral populations.