Gareth J Williams

Bangor University · School of Ocean Sciences

The Anthropocene rise in global temperatures is facilitating the expansion of tropical species into historically non-native subtropical locales, including coral reef fish. This redistribution of species, known as tropicalization, has serious consequences for economic development, livelihoods, food security, human health, and culture. Measuring the...

Climate change, overfishing, and pollution have driven changes in the composition of many extant reef fish assemblages. As global temperatures rise, historically temperate locales are becoming inhabited by vagrant tropical species as their ranges expand poleward in a process known as tropicalization. Severe reef fish biomass declines are predicted...

The influence of depth and associated gradients in light, nutrients and plankton on the ecological organization of tropical reef communities was first described over six decades ago but remains untested across broad geographies. During this time humans have become the dominant driver of planetary change, requiring that we revisit historic ecologica...

Coral reef ecosystems are being fundamentally restructured by local human impacts and climate-driven marine heatwaves that trigger mass coral bleaching and mortality¹. Reducing local impacts can increase reef resistance to and recovery from bleaching². However, resource managers lack clear advice on targeted actions that best support coral reefs un...

Marine heatwaves are causing recurring coral bleaching events on tropical reefs that are driving ecosystem change. Yet, little is known about how bleaching and subsequent coral mortality impacts the spatial properties of tropical seascapes, such as patterns of organism spatial clustering and heterogeneity across scales. Changes in these spatial pro...

Marine heatwaves are triggering coral bleaching events and devastating coral populations globally, highlighting the need to identify processes promoting coral survival. Here, we show that acceleration of a major ocean current and shallowing of the surface mixed layer enhanced localized upwelling on a central Pacific coral reef during the three stro...

Scientists and managers rely on indicator taxa such as coral and macroalgal cover to evaluate the effects of human disturbance on coral reefs, often assuming a universally positive relationship between local human disturbance and macroalgae. Despite evidence that macroalgae respond to local stressors in diverse ways, there have been few efforts to...

Highly competitive coral reef benthic communities are acutely sensitive to changes in environmental parameters such as temperature and nutrient concentrations. Physical oceanographic processes that induce upwelling therefore act as drivers of community structure on tropical reefs. How upwelling impacts coral communities, however, is not fully under...

Aim Biodiversity loss is impacting essential ecosystem functions and services across the globe. Recently, our interest in the benefits of biodiversity for ecosystem function has shifted focus from measurements of species richness to functional diversity and composition. However, the additional importance of other community characteristics, such as...

Dark spot disease (DSD) was first reported within Florida’s coral reefs in the 1990s but factors affecting its spatial distribution have not been well studied. We used a 14-year (2005–2019) coral monitoring data set, utilizing 2242 surveys collected along Florida’s coral reefs (about 530 linear km) to explore the spatial and temporal patterns of DS...

The influence of depth and associated gradients in light, nutrients, and plankton on the ecological organisation of tropical reef communities was first described over six decades ago but remains untested across broad geographies. Humans have also become the dominant driver of planetary change, requiring we re-visit historic ecological paradigms to...

Within low-nutrient tropical oceans, islands and atolls with higher primary production support higher fish biomass and reef organism abundance. External energy subsidies can be delivered onto reefs via a range of physical mechanisms. However, the influence of spatial variation in primary production on reef fish growth and condition is largely unkno...

High energy marine regions host ecologically important habitats like temperate reefs, but are less anthropogenically developed and understudied compared to lower energy waters. In the marine environment direct habitat observation is limited to small spatial scales, and high energy waters present additional logistical challenges and constraints. Sem...

Bioindicators are useful for determining nutrient regimes in marine environments, but their ability to evaluate corals reefs in different ecological states is poorly understood. The precision, availability and congruency of eight potential bioindicators (brown macroalgae, green macroalgae, turf algae, cyanobacteria, soft corals, zoanthids, sponges,...

Plastic pollution and climate change have commonly been treated as two separate issues and sometimes are even seen as competing. Here we present an alternative view that these two issues are fundamentally linked. Primarily, we explore how plastic contributes to greenhouse gas (GHG) emissions from the beginning to the end of its life cycle. Secondly...

We used a 12-yr data set of benthic cover (2005–2017), spanning two bleaching events, to assess changes in benthic cover and coral community composition along 21 islands within Gulf of Mannar (GoM), southeast India. Overall, between 2005 and 2017 reefs had a simultaneous decrease in relative coral cover (avg. = − 36%) and increase in algal cover (a...

Upwelling has profound effects on nearshore tropical ecosystems, but our ability to study these patterns and processes depends on quantifying upwelling dynamics in a repeatable and rigorous manner. Previous methods often lack the ability to identify individual cold‐pulse events within temperature time series data or require several user‐defined par...

From microbes to humans, habitat structural complexity plays a direct role in the provision of physical living space, and increased complexity supports higher biodiversity and ecosystem functioning across biomes. Coastal development and the construction of artificial shorelines are altering natural landscapes as humans seek socio-economic benefits...

Habitat structure influences a broad range of ecological interactions and ecosystem functions across biomes. To understand and effectively manage dynamic ecosystems, we need detailed information about habitat properties and how they vary across spatial and temporal scales. Measuring and monitoring variation in three‐dimensional (3D) habitat structu...

[This corrects the article DOI: 10.1371/journal.pone.0061974.].

Scleractinian corals are engineers on coral reefs that provide both structural complexity as habitat and sustenance for other reef-associated organisms via the release of organic and inorganic matter. However, coral reefs are facing multiple pressures from climate change and other stressors, which can result in mass coral bleaching and mortality ev...

Background Coral reefs are rapidly changing in response to local and global stressors. Research to better understand and inform the management of these stressors is burgeoning. However, in situ studies of coral reef ecology are constrained by complex logistics and limited resources. Many reef studies are also hampered by the scale-dependent nature...

The third global coral bleaching event, which started in 2014 and extended well into 2017, was the longest coral bleaching event on record. The length of the event means corals in some parts of the world had no time to recover in 2014, 2015 or 2016 during the cool/winter season, prior to experiencing bleaching the following year. This recent global...

The spatial structure of ecological communities on tropical coral reefs across seascapes and geographies have historically been poorly understood. Here we addressed this for the first time using spatially expansive and thematically resolved benthic community data collected around five uninhabited central Pacific oceanic islands, spanning 6° latitud...

Given the recent trend towards establishing very large marine protected areas (MPAs) and the high potential of these to contribute to global conservation targets, we review outcomes of the last decade of marine conservation research in the British Indian Ocean Territory (BIOT), one of the largest MPAs in the world. The BIOT MPA consists of the atol...

Human activities are changing ecosystems at an unprecedented rate, yet large-scale studies into how local human impacts alter natural systems and interact with other aspects of global change are still lacking. Here we provide empirical evidence that local human impacts fundamentally alter relationships between ecological communities and environment...

Geographical comparisons suggest that coral reef communities can vary as a function of their environmental context, differing not just in terms of total coral cover but also in terms of relative abundance (or coverage) of coral taxa. While much work has considered how shifts in benthic reef dynamics can shift dominance of stony corals relative to a...

Primary producers in terrestrial and marine systems can be affected by fungal pathogens threatening the provision of critical ecosystem services. Crustose coralline algae (CCA) are ecologically important members of tropical reef systems and are impacted by coralline fungal disease (CFD) which manifests as overgrowth of the CCA crust by fungal lesio...

The Arabian Peninsula borders the hottest reefs in the world, and corals living in these extreme environments can provide insight into the effects of warming on coral health and disease. Here, we examined coral reef health at 17 sites across three regions along the northeastern Arabian Peninsula (Persian Gulf, Strait of Hormuz and Oman Sea) represe...

Ecological processes occur over multiple spatial, temporal and thematic scales in three-dimensional (3D) ecosystems. Characterizing and monitoring change in 3D structure at multiple scales is challenging within the practical constraints of conventional ecological tools. Remote sensing from satellites and crewed aircraft has revolutionized broad-sca...

Policies designed to address current challenges to the sustainability of fisheries generally use an ecosystem‐based approach – one that incorporates interactions between fishes, fishers, and the environment. Fishing alters the trophic structure among coral reef fish but properly assessing those impacts requires an understanding of how and why that...

Life for many of the world’s marine fish begins at the ocean surface. Ocean conditions dictate food availability and govern survivorship, yet little is known about the habitat preferences of larval fish during this highly vulnerable life-history stage. Here we show that surface slicks, a ubiquitous coastal ocean convergence feature, are important n...

An outbreak of stony coral tissue loss disease (SCTLD), emerged on reefs off the coast of southeast Florida in 2014 and continues to spread throughout Florida’s Reef Tract. SCTLD is causing extensive mortality of multiple coral species and disease signs vary among affected coral species with differences in rates of tissue loss (acute and subacute),...

We take advantage of a natural gradient of human exploitation and oceanic primary production across five central Pacific coral reefs to examine foraging patterns in common coral reef fishes. Using stomach content and stable isotope (δ¹⁵N and δ¹³C) analyses, we examined consistency across islands in estimated foraging patterns. Surprisingly, species...

Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages—the foundation species of coral reef ecosystems. Here, we...

Studies have shown that as we sequence seawater from a selected environment deeper and deeper, we approach finding every bacterial taxon known for the ocean as a whole. However, such studies have focused on taxonomic marker genes rather than on whole genomes, raising the possibility that the lack of endemism results from the method of investigation...

Tropical coral reefs currently face an unprecedented restructuring since their extant form and function emerged ~24 million years ago in the early Neogene. They have entered the Anthropocene—an epoch where humans have become the dominant force of planetary change. Human impacts on and interactions with coral reefs are escalating across multiple tro...

https://www.coris.noaa.gov/activities/maui_reef_resilience/ The project team assessed the relative resilience of reef sites at two depths along areas of West and South-West Maui ("leeward Maui") in March of 2018. The surveys were conducted as a collaborative effort with DAR, The Nature Conservancy, and community organizations. This report presents...

Coral reefs underpin a range of ecosystem goods and services that contribute to the well‐being of millions of people. However, tropical coral reefs in the Anthropocene are likely to be functionally different from reefs in the past. In this perspective piece, we ask, what does the Anthropocene mean for the provision of ecosystem services from coral...

Our project team assessed the relative resilience of reef sites at two depths along areas of West and South-West Maui (‘leeward Maui’) in March of 2018. The surveys were conducted as a collaborative effort with DAR, The Nature Conservancy, and community organizations. This report presents findings from meeting these project objectives: 1) assess be...

Evidence suggests many marine bacteria are cosmopolitan, with widespread but sparse strains poised to seed abundant populations upon conducive growth conditions. However, studies supporting this 'microbial seed bank' hypothesis have analyzed taxonomic marker genes rather than whole genomes/metagenomes, leaving open the possibility that disparate oc...

Coral reefs worldwide face unprecedented cumulative anthropogenic effects of interacting local human pressures, global climate change and distal social processes. Reefs are also bound by the natural biophysical environment within which they exist. In this context, a key challenge for effective management is understanding how anthropogenic and bioph...

We are in the Anthropocene—an epoch where humans are the dominant force of planetary change. Ecosystems increasingly reflect rapid human‐induced, socioeconomic and cultural selection rather than being a product of their surrounding natural biophysical setting. This poses the intriguing question: To what extent do existing ecological paradigms captu...

Understanding and predicting patterns of spatial organization across ecological communities is central to the field of landscape ecology, and a similar line of inquiry has begun to evolve sub‐tidally among seascape ecologists. Much of our current understanding of the processes driving marine community patterns, particularly in the tropics, has come...

Abstract Coral reefs worldwide face an uncertain future with many reefs reported to transition from being dominated by corals to macroalgae. However, given the complexity and diversity of the ecosystem, research on how regimes vary spatially and temporally is needed. Reef regimes are most often characterised by their benthic components; however, co...

Mixotrophy is among the most successful nutritional strategies in terrestrial and marine ecosystems. The ability of organisms to supplement primary nutritional modes along continua of autotrophy and heterotrophy fosters trophic flexibility that can sustain metabolic demands under variable or stressful conditions. Symbiotic, reef-building corals are...

The original version of the Article was missing an acknowledgement of a funding source. The authors acknowledge that A. Safaie and K.Davis were supported by National Science Foundation Award No. 1436254 and G. Pawlak was supported by Award No. 1436522. This omission has now been corrected in the PDF and HTML versions of the Article.

Coral bleaching is the detrimental expulsion of algal symbionts from their cnidarian hosts, and predominantly occurs when corals are exposed to thermal stress. The incidence and severity of bleaching is often spatially heterogeneous within reef-scales (<1 km), and is therefore not predictable using conventional remote sensing products. Here, we sys...

Depth is used often as a proxy for gradients in energetic resources on coral reefs and for predicting patterns of community energy use. With increasing depth, loss of light can lead to a reduced reliance on autotrophy and an increased reliance on heterotrophy by mixotrophic corals. However, the generality of such trophic zonation varies across cont...

Coral reefs are a globally threatened ecosystem due to a range of anthropogenic impacts. Increasing sea surface temperatures associated with global warming are a particular threat, as corals grow close to their upper thermal limit. When this limit is exceeded for a sufficient length of time during thermal stress events, corals lose their algal symb...

A major challenge for coral reef conservation and management is understanding how a wide range of interacting human and natural drivers cumulatively impact and shape these ecosystems. Despite the importance of understanding these interactions, a methodological framework to synthesize spatially explicit data of such drivers is lacking. To fill this...

Driver data analysis, assumptions, and limitations. (DOCX)

Correlation matrix for driver layers used in PCA. (XLSX)

Detailed GIS methods used to create fisheries catch maps. (DOCX)

For sessile organisms such as reef-building corals, differences in the degree of dispersion of individuals across a landscape may result from important differences in life-history strategies or may reflect patterns of habitat availability. Descriptions of spatial patterns can thus be useful not only for the identification of key biological and phys...

Significance Coral reef taxa produce a diverse array of molecules, some of which are important pharmaceuticals. To better understand how molecular diversity is generated on coral reefs, tandem mass spectrometry datasets of coral metabolomes were analyzed using a novel approach called meta-mass shift chemical (MeMSChem) profiling. MeMSChem profiling...

Increasingly frequent severe coral bleaching is among the greatest threats to coral reefs posed by climate change. Global climate models (GCMs) project great spatial variation in the timing of annual severe bleaching (ASB) conditions; a point at which reefs are certain to change and recovery will be limited. However, previous model-resolution proje...

Humans are an increasingly dominant driver of Earth's biological communities , but differentiating human impacts from natural drivers of ecosystem state is crucial. Herbivorous fish play a key role in maintaining coral dominance on coral reefs, and are widely affected by human activities, principally fishing. We assess the relative importance of hu...

Summary of sampling survey effort; Herbivorous fish functional classification; Predictors terms, estimating anthropogenic impacts and modeling; Herbivore species richness and biomass by region; Summary of the best performing GAMMs (all models with weight > 0.05) with smoother graphs.

Anthropogenic changes to the Earth now rival those caused by the forces of nature and have shepherded us into a new planetary epoch – the Anthropocene. Such changes include profound and often unexpected alterations to coral reef ecosystems and the services they provide to human societies. Ensuring that reefs and their services endure during the Ant...

Sponges are important components of coral reef fauna, although little is known of their temporal dynamics. Sponges dominate the lagoon system at Palmyra Atoll in the Central Pacific, which may not be its natural state. Here we examined the temporal variability and recruitment rates of these sponge assemblages to determine if they are stable and exa...

Oceanic microbial diversity covaries with physicochemical parameters. Temperature, for example, explains approximately half of global variation in surface taxonomic abundance. It is unknown, however, whether covariation patterns hold over narrower parameter gradients and spatial scales, and extending to mesopelagic depths. We collected and sequence...

Oceanic microbial diversity covaries with physicochemical parameters. Temperature, for example, explains approximately half of global variation in surface taxonomic abundance. It is unknown, however, whether covariation patterns hold over narrower parameter gradients and spatial scales, and extending to mesopelagic depths. We collected and sequence...

The Hawai'i Coral Disease database (HICORDIS) houses data on colony-level coral health condition observed across the Hawaiian archipelago, providing information to conduct future analyses on coral reef health in an era of changing environmental conditions. Colonies were identified to the lowest taxonomic classification possible (species or genera),...

Tropical cyclone (TC) waves can severely damage coral reefs. Models that predict where to find such damage (the ‘damage zone’) enable reef managers to: 1) target management responses after major TCs in near-real time to promote recovery at severely damaged sites; and 2) identify spatial patterns in historic TC exposure to explain habitat condition...

Dramatic changes in populations of fishes living on coral reefs have been documented globally and, in response, the research community has initiated efforts to assess and monitor reef fish assemblages. A variety of visual census techniques are employed, however results are often incomparable due to differential methodological performance. Although...

List of Survey Questions Included in the Survey. (DOCX)

Description of Top Three Survey Methodologies. (DOCX)

Online Survey. (DOCX)