Coral tumor-like growth anomalies induce an immune response and reduce fecundity

Multi-Factor Coral Disease Risk: A new product for early warning and management

Ecological forecasts are becoming increasingly valuable tools for conservation and management. However, there are few examples of near-real-time forecasting systems that account for the wide range of ecological complexities. We developed a new coral disease ecological forecasting system that explores a suite of ecological relationships and their uncertainty and investigates how forecast skill changes with shorter lead times. The Multi-Factor Coral Disease Risk product introduced here uses a combination of ecological and marine environmental conditions to predict the risk of white syndromes and growth anomalies across reefs in the central and western Pacific and along the east coast of Australia and is available through the US National Oceanic and Atmospheric Administration Coral Reef Watch program. This product produces weekly forecasts for a moving window of 6 months at a resolution of ~5 km based on quantile regression forests. The forecasts show superior skill at predicting disease risk on withheld survey data from 2012 to 2020 compared with predecessor forecast systems, with the biggest improvements shown for predicting disease risk at mid- to high-disease levels. Most of the prediction uncertainty arises from model uncertainty, so prediction accuracy and precision do not improve substantially with shorter lead times. This result arises because many predictor variables cannot be accurately forecasted, which is a common challenge across ecosystems. Weekly forecasts and scenarios can be explored through an online decision support tool and data explorer, co-developed with end-user groups to improve use and understanding of ecological forecasts. The models provide near-real-time disease risk assessments and allow users to refine predictions and assess intervention scenarios. This work advances the field of ecological forecasting with real-world complexities and, in doing so, better supports near-term decision making for coral reef ecosystem managers and stakeholders. Secondarily, we identify clear needs and provide recommendations to further enhance our ability to forecast coral disease risk.

Coral growth anomalies, neoplasms, and tumors in the Anthropocene

One of the most widespread coral diseases linked to anthropogenic activities and recorded on reefs worldwide is characterized by anomalous growth formations in stony corals, referred to as coral growth anomalies (GAs). The biological functions of GA tissue include limited reproduction, reduced access to resources, and weakened ability to defend against predators. Transcriptomic analyses have revealed that, in some cases, disease progression can involve host genes related to oncogenesis, suggesting that the GA tissues may be malignant neoplasms such as those developed by vertebrates. The number of studies reporting the presence of GAs in common reef-forming species highlights the urgency of a thorough understanding of the pathology and causative factors of this disease and its parallels to higher organism malignant tissue growth. Here, we review the current state of knowledge on the etiology and holobiont features of GAs in reef-building corals.

Four-Year Field Survey of Black Band Disease and Skeletal Growth Anomalies in Encrusting Montipora spp. Corals around Sesoko Island, Okinawa

The Indo-Pacific zooxanthellate scleractinian coral genus Montipora is the host of many coral diseases. Among these are cyanobacterial Black Band Disease (BBD) and Skeletal Growth Anomalies (GAs), but in general data on both diseases are lacking from many regions of the Indo-Pacific, including from Okinawa, southern Japan. In this study, we collected annual prevalence data of Black Band Disease (BBD) and Skeletal Growth Anomalies (GAs) affecting the encrusting form of genus Montipora within the shallow reefs of the subtropical Sesoko Island (off the central west coast of Okinawajima Island) from summer to autumn for four years (2017 to 2020). In 2020 Montipora percent coverage and colony count were also assessed. Generalized Linear Models (GLM) were used to understand the spatial and temporal variation of both BBD and GAs in the nearshore (NE) and reef edge (RE) sites, which revealed higher probability of BBD occurrence in RE sites. BBD prevalence was significantly higher in 2017 in some sites than all other years with site S12 having significant higher probability during all four surveyed years. In terms of GAs, certain sites in 2020 had higher probability of occurrence than during the other years. While the general trend of GAs increased from 2017 to 2020, it was observed to be non-fatal to colonies. In both diseases, the interaction between sites and years was significant. We also observed certain BBD-infected colonies escaping complete mortality. BBD progression rates were monitored in 2020 at site S4, and progression was related to seawater temperatures and was suppressed during periods of heavy rain and large strong typhoons. Our results suggest that higher BBD progression rates are linked with high sea water temperatures (SST > bleaching threshold SST) and higher light levels (>1400 µmol m−2 s−1), indicating the need for further controlled laboratory experiments. The current research will help form the basis for continued future research into these diseases and their causes in Okinawa and the Indo-Pacific Ocean.

A proteomic analysis of skeletal tissue anomaly in the brain coral Platygyra carnosa

Coral skeletal growth anomaly (GA) is a common coral disease. It has been considered as a pathological condition comparable to abnormal tissue growth in mammals, but little is known about the molecular changes underlying coral GA. To investigate the molecular pathology of GA, we compared the proteome between normal and GA-affected tissues of the brain coral Platygyra carnosa using iTRAQ-labeling and LC-MS/MS, which quantified 818 proteins and identified 117 differentially expressed proteins (DEPs). GO analyses revealed DEPs that might be related to GA included "translational elongation", "proteasome core complex", "amine metabolic processes" and "lysosome". Several proteins implicated in calcification and fluorescence were differentially expressed at both protein and mRNA level. Protein-protein interaction network suggested possible involvement of TNF receptor signaling in GA. Overall, our results provided novel insights into the molecular pathology of coral GA, which will pave the way for determination of the causative agent(s) of this coral disease.

Case-control design identifies ecological drivers of endemic coral diseases

Endemic disease transmission is an important ecological process that is challenging to study because of low occurrence rates. Here, we investigate the ecological drivers of two coral diseases-growth anomalies and tissue loss-affecting five coral species. We first show that a statistical framework called the case-control study design, commonly used in epidemiology but rarely applied to ecology, provided high predictive accuracy (67-82%) and disease detection rates (60-83%) compared with a traditional statistical approach that yielded high accuracy (98-100%) but low disease detection rates (0-17%). Using this framework, we found evidence that 1) larger corals have higher disease risk; 2) shallow reefs with low herbivorous fish abundance, limited water motion, and located adjacent to watersheds with high fertilizer and pesticide runoff promote low levels of growth anomalies, a chronic coral disease; and 3) wave exposure, stream exposure, depth, and low thermal stress are associated with tissue loss disease risk during interepidemic periods. Variation in risk factors across host-disease pairs suggests that either different pathogens cause the same gross lesions in different species or that the same disease may arise in different species under different ecological conditions.

Spatial and Temporal Variation in Fecundity of Acropora spp. in the Northern Great Barrier Reef

The amount of energy invested in sexual reproduction by scleractinian corals depends on their life history strategies (i.e., allocation of energy between growth, reproduction, and maintenance). However, energy allocated to reproduction will also be affected by the amount of energy acquired and prevailing environmental conditions. Coral fecundity is therefore likely to vary spatially, especially along marked gradients in environmental conditions. One of the foremost gradients in reef structure and environmental conditions occurs with distance from the coast, whereby inner-shelf or near shore reefs are generally subject to higher levels of nutrients, sediments and pollutants, which often adversely affect reef-building corals. This study quantified fecundity (oocytes per polyp) for three species, Acropora nasuta, A. spathulata, and A. hyacinthus, at six locations in the northern Great Barrier Reef (GBR), encompassing inner-, mid- and outer-shelf reefs. Replicate colonies were sampled at each location prior to the predicted date of spawning in 2013 and 2014. Both shelf position and year were important factors explaining variation in fecundity for each of the three coral species. Most notably, there were clear and consistent declines in the number of oocytes between 2013 and 2014, coinciding with the incidence of category 4 Cylone Ita in early 2014. Contrary to expectations, polyp-level fecundity was no lower (and in some cases substantially higher) on inner-shelf reefs, compared to conspecifics growing on mid-shelf or outer-shelf reefs. The observed patterns are much more complicated than anticipated, necessitating further research to understand differential population dynamics of corals on inner-shelf versus mid- and outer-shelf reefs.