Geology topics

Colleen A. Burge

Publications and source records attributed to Colleen A. Burge.

6 recordsLinked to original sources

USGS2021

Warming sea surface temperatures fuel summer epidemics of eelgrass wasting disease

Seawater temperatures are increasing, with many unquantified impacts on marine diseases. While prolonged temperature stress can accelerate host-pathogen interactions, the outcomes in nature are poorly quantified. We monitored eelgrass wasting disease (EWD) from 2013-2017 and correlated mid-summer prevalence of EWD with remotely sensed seawater temperature metrics before, during, and after the 2015-2016 marine heatwave in the northeast Pacific, the longest marine heatwave in recent history. Eelgrass shoot density declined by 60% between 2013 and 2015 and did not recover. EWD prevalence ranged from 5-70% in 2013 and increased to 60-90% by 2017. EWD severity approximately doubled each year between 2015 and 2017. EWD prevalence was positively correlated with warmer temperature for the month prior to sampling while EWD severity was negatively correlated with warming prior to sampling. This complex result may be mediated by leaf growth; bigger leaves may be more likely to be diseased, but may also grow faster than lesions, resulting in lower severity. Regional stressors leading to population declines prior to or early in the heatwave may have exacerbated the effects of warming on eelgrass disease susceptibility and reduced the resilience of this critical species.

Marine Ecology Progress Series↗

USGS2018

Intensive oyster aquaculture can reduce disease impacts on sympatric wild oysters

Risks associated with disease spread from fish and shellfish farming have plagued the growth and public perception of aquaculture worldwide. However, by processing nutrients and organic material from the water column, the culture of many suspension-feeding bivalves has been proposed as a novel solution toward mitigating problems facing coastal water quality, including the removal of disease-causing parasites. Here we developed and simulated an epidemiological model describing sympatric oyster Crassostrea virginica populations in aquaculture and the wild impacted by the protozoan parasite Perkinsus marinus . Our model captured the indirect interaction between wild and cultured populations that occurs through sharing water-borne P. marinus transmission stages, and we hypothesized that oyster aquaculture can enhance wild oyster populations through reduced parasitism as long as cultured oysters are harvested prior to spreading disease. We found that the density of oysters in aquaculture, which is commonly thought to lead to the spread of disease through farms and out to nearby populations in the wild, has only indirect effects on P. marinus transmission through its interaction with the rate of aquaculture harvests. Sufficient aquaculture harvest, which varies with the susceptibility of farmed oysters to P. marinus infection and their lifespan once infected, reduces disease by diluting parasites in the environment. Our modeling results offer new insights toward the broader epidemiological implications of oyster aquaculture and effective disease management.

Aquaculture Environment Interactions↗

USGS2016

Complementary approaches to diagnosing marine diseases: a union of the modern and the classic

Linking marine epizootics to a specific aetiology is notoriously difficult. Recent diagnostic successes show that marine disease diagnosis requires both modern, cutting-edge technology (e.g. metagenomics, quantitative real-time PCR) and more classic methods (e.g. transect surveys, histopathology and cell culture). Here, we discuss how this combination of traditional and modern approaches is necessary for rapid and accurate identification of marine diseases, and emphasize how sole reliance on any one technology or technique may lead disease investigations astray. We present diagnostic approaches at different scales, from the macro (environment, community, population and organismal scales) to the micro (tissue, organ, cell and genomic scales). We use disease case studies from a broad range of taxa to illustrate diagnostic successes from combining traditional and modern diagnostic methods. Finally, we recognize the need for increased capacity of centralized databases, networks, data repositories and contingency plans for diagnosis and management of marine disease.

Philosophical Transactions of the Royal Society B:↗

USGS2015

Up in arms: Immune and nervous system response to sea star wasting disease

Echinoderms, positioned taxonomically at the base of deuterostomes, provide an important system for the study of the evolution of the immune system. However, there is little known about the cellular components and genes associated with echinoderm immunity. The 2013–2014 sea star wasting disease outbreak is an emergent, rapidly spreading disease, which has led to large population declines of asteroids in the North American Pacific. While evidence suggests that the signs of this disease, twisting arms and lesions, may be attributed to a viral infection, the host response to infection is still poorly understood. In order to examine transcriptional responses of the sea star Pycnopodia helianthoides to sea star wasting disease, we injected a viral sized fraction (0.2 μm) homogenate prepared from symptomatic P. helianthoides into apparently healthy stars. Nine days following injection, when all stars were displaying signs of the disease, specimens were sacrificed and coelomocytes were extracted for RNA-seq analyses. A number of immune genes, including those involved in Toll signaling pathways, complement cascade, melanization response, and arachidonic acid metabolism, were differentially expressed. Furthermore, genes involved in nervous system processes and tissue remodeling were also differentially expressed, pointing to transcriptional changes underlying the signs of sea star wasting disease. The genomic resources presented here not only increase understanding of host response to sea star wasting disease, but also provide greater insight into the mechanisms underlying immune function in echinoderms.

PLoS ONE↗

USGS2014

Densovirus associated with sea-star wasting disease and mass mortality

Populations of at least 20 asteroid species on the Northeast Pacific Coast have recently experienced an extensive outbreak of sea-star (asteroid) wasting disease (SSWD). The disease leads to behavioral changes, lesions, loss of turgor, limb autotomy, and death characterized by rapid degradation (“melting”). Here, we present evidence from experimental challenge studies and field observations that link the mass mortalities to a densovirus (Parvoviridae). Virus-sized material (i.e., <0.2 μm) from symptomatic tissues that was inoculated into asymptomatic asteroids consistently resulted in SSWD signs whereas animals receiving heat-killed (i.e., control) virus-sized inoculum remained asymptomatic. Viral metagenomic investigations revealed the sea star-associated densovirus (SSaDV) as the most likely candidate virus associated with tissues from symptomatic asteroids. Quantification of SSaDV during transmission trials indicated that progression of SSWD paralleled increased SSaDV load. In field surveys, SSaDV loads were more abundant in symptomatic than in asymptomatic asteroids. SSaDV could be detected in plankton, sediments and in nonasteroid echinoderms, providing a possible mechanism for viral spread. SSaDV was detected in museum specimens of asteroids from 1942, suggesting that it has been present on the North American Pacific Coast for at least 72 y. SSaDV is therefore the most promising candidate disease agent responsible for asteroid mass mortality.

Proceedings of the National Academy of Sciences of↗

USGS2014

Climate change influences on marine infectious diseases: implications for management and society

Infectious diseases are common in marine environments, but the effects of a changing climate on marine pathogens are not well understood. Here, we focus on reviewing current knowledge about how the climate drives hostpathogen interactions and infectious disease outbreaks. Climate-related impacts on marine diseases are being documented in corals, shellfish, finfish, and humans; these impacts are less clearly linked to other organisms. Oceans and people are inextricably linked, and marine diseases can both directly and indirectly affect human health, livelihoods, and well-being. We recommend an adaptive management approach to better increase the resilience of ocean systems vulnerable to marine diseases in a changing climate. Land-based management methods of quarantining, culling, and vaccinating are not successful in the ocean; therefore, forecasting conditions that lead to outbreaks and designing tools/approaches to influence these conditions may be the best way to manage marine disease.

Annual Review of Marine Science↗