Localized outbreaks of coral disease on Arabian reefs are linked to extreme temperatures and environmental stressors

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) representing a gradient of environmental conditions. The Persian Gulf has extreme seasonal fluctuations in temperature and chronic hypersalinity, whereas the other two regions experience more moderate conditions. Field surveys identified 13 coral diseases including tissue loss diseases of unknown etiology (white syndromes) in Porites, Platygyra, Dipsastraea, Cyphastrea, Acropora and Goniopora; growth anomalies in Porites, Platygyra and Dipsastraea; black band disease in Platygyra, Dipsastraea, Acropora, Echinopora and Pavona; bleached patches in Porites and Goniopora and a disease unique to this region, yellow-banded tissue loss in Porites. The most widespread diseases were Platygyra growth anomalies (52.9% of all surveys), Acropora white syndrome (47.1%) and Porites bleached patches (35.3%). We found a number of diseases not yet reported in this region and found differential disease susceptibility among coral taxa. Disease prevalence was higher on reefs within the Persian Gulf (avg. 2.05%) as compared to reefs within the Strait of Hormuz (0.46%) or Oman Sea (0.25%). A high number of localized disease outbreaks (8 of 17 sites) were found, especially within the Persian Gulf (5 of 8 sites). Across all regions, the majority of variation in disease prevalence (82.2%) was associated with the extreme temperature range experienced by these corals combined with measures of organic pollution and proximity to shore. Thermal stress is known to drive a number of coral diseases, and thus, this region provides a platform to study disease at the edge of corals’ thermal range

Embedding the value of coastal ecosystem services into climate change adaptation planning

Coastal habitats, such as salt marshes and dune systems, can protect communities from hazards by reducing coastline exposure. However, these critical habitats and their diverse ecosystem services are threatened by coastal development and the impacts from a changing climate. Ever increasing pressure on coastal habitats calls for coastal climate adaptation efforts that mitigate or adapt to these pressures in ways that maintain the integrity of coastal landscapes. An important challenge for decisionmakers is determining the best mitigation and adaptation strategies that not only protect human lives and property, but also safeguard the ability of coastal habitats to provide a broad suite of benefits. Here, we present a potential pathway for local-scale climate change adaptation planning through the identification and mapping of natural habitats that provide the greatest benefits to coastal communities. The methodology coupled a coastal vulnerability model with a climate adaptation policy assessment in an effort to identify priority locations for nature-based solutions that reduce vulnerability of critical assets using feasible land-use policy methods. Our results demonstrate the critical role of natural habitats in providing the ecosystem service of coastal protection in California. We found that specific dune habitats play a key role in reducing erosion and inundation of the coastline and that several wetland areas help to absorb energy from storms and provide a protective service for the coast of Marin county, California, USA. Climate change and adaptation planning are globally relevant issues in which the scalability and transferability of solutions must be considered. This work outlines an iterative approach for climate adaptation planning at a local-scale, with opportunity to consider the scalability of an iterative science-policy engagement approach to regional, national, and international levels

Ecological causes and consequences of Sea Star Wasting Syndrome on the Pacific coast

Disease outbreaks are becoming more frequent as anthropogenic changes to ecosystem function stress species and create conditions favorable for pathogen infection. Marine outbreaks that were once locally constrained are re-emerging as large-scale epidemics with heightened mortality, decimating populations across multiple ocean basins. Effective prediction of future disease impacts requires a better understanding of their causes and consequences. In this dissertation, I explore the connections between environmental conditions, recovery of decimated host populations, and multispecies interactions to examine how a marine epidemic affects marine communities. I focus on a recent Sea Star Wasting Syndrome outbreak in rocky intertidal habitats along the Pacific coast of North America, with emphasis in Central California. Sea stars are an iconic intertidal species to many coastal visitors. Their absence has generated heightened public awareness of current challenges to ocean health, providing many opportunities for engagement in the process and outcomes of ecological research.In my first chapter, I use data from long-term ecological monitoring to assess the recovery of sea star populations and predation pressure in the years immediately following the outbreak. I show that while sea star numbers are rebounding, these populations are made of smaller individuals that do consume the same amount of food. In my second chapter, I explore potential conditions associated with outbreak timing using data from citizen scientists and researchers combined. I identified associations between Sea Star Wasting Syndrome appearance, low tide exposure duration, proximity to other infected sites, and chlorophyll a concentration, though the relative importance of these factors varied across geographic regions of the coast. In my third chapter, I take advantage of a natural experiment created by the loss of predatory sea stars to measure the consequences of the outbreak on the intertidal community. I found that while mussels, the sea stars’ primary prey, had increased their coverage, they had not displaced the species living below the mussel bed. At local field sites, mussel increases were positively correlated with mussel recruitment and not pre-outbreak sea star levels. However, a coast-wide scale, pre-outbreak sea star density was positively correlated with pre-outbreak sea star density. Finally, I conclude with key insights from this work. My dissertation provides evidence that sea star wasting does not have uniform causes or population-level and community-level consequences across coastal regions. I discuss the value of long-term ecological monitoring and citizen science as critical information sources in the process of evaluating disease impacts

Associations among Plankton Abundance, Water Quality And Sediment Quality In The San Francisco Bay: Nitrogen And Phosphorus

nutrients from anthropogenic pollution can degrade water quality and alter the balance of marine food webs. lying at the base of the trophic pyramid, plankton quickly respond to nutrient changes in the water, which can have repercussions throughout both pelagic and benthic food webs, and thus they serve as a good bioindicator of water quality. In early november 2009, we evaluated sediment pollution, water pollution, and plankton abundance at four shoreline sites in the San Francisco Bay. We tested the sediment for nitrogen, phosphorus, potassium, and pH levels, all factors that can affect growth of primary producers. In the water, we tested nitrate, phosphate, and pH levels. lastly, we sampled shoreline plankton abundance both morning and evening. Sediment phosphorus and water phosphates were strongly correlated with one another, but water nitrates remained relatively constant, at low levels, across sites. daytime plankton abundance showed a positive trend with water phosphate. these trends suggest nitrogen is quickly taken up by plankton, making nitrogen the limiting factor for them. the relationship between plankton and phosphorus is influenced by more complex factors

Ecological causes and consequences of Sea Star Wasting Syndrome on the Pacific coast

Disease outbreaks are becoming more frequent as anthropogenic changes to ecosystem function stress species and create conditions favorable for pathogen infection. Marine outbreaks that were once locally constrained are re-emerging as large-scale epidemics with heightened mortality, decimating populations across multiple ocean basins. Effective prediction of future disease impacts requires a better understanding of their causes and consequences. In this dissertation, I explore the connections between environmental conditions, recovery of decimated host populations, and multispecies interactions to examine how a marine epidemic affects marine communities. I focus on a recent Sea Star Wasting Syndrome outbreak in rocky intertidal habitats along the Pacific coast of North America, with emphasis in Central California. Sea stars are an iconic intertidal species to many coastal visitors. Their absence has generated heightened public awareness of current challenges to ocean health, providing many opportunities for engagement in the process and outcomes of ecological research.In my first chapter, I use data from long-term ecological monitoring to assess the recovery of sea star populations and predation pressure in the years immediately following the outbreak. I show that while sea star numbers are rebounding, these populations are made of smaller individuals that do consume the same amount of food. In my second chapter, I explore potential conditions associated with outbreak timing using data from citizen scientists and researchers combined. I identified associations between Sea Star Wasting Syndrome appearance, low tide exposure duration, proximity to other infected sites, and chlorophyll a concentration, though the relative importance of these factors varied across geographic regions of the coast. In my third chapter, I take advantage of a natural experiment created by the loss of predatory sea stars to measure the consequences of the outbreak on the intertidal community. I found that while mussels, the sea stars’ primary prey, had increased their coverage, they had not displaced the species living below the mussel bed. At local field sites, mussel increases were positively correlated with mussel recruitment and not pre-outbreak sea star levels. However, a coast-wide scale, pre-outbreak sea star density was positively correlated with pre-outbreak sea star density. Finally, I conclude with key insights from this work. My dissertation provides evidence that sea star wasting does not have uniform causes or population-level and community-level consequences across coastal regions. I discuss the value of long-term ecological monitoring and citizen science as critical information sources in the process of evaluating disease impacts

Associations among Plankton Abundance, Water Quality And Sediment Quality In The San Francisco Bay: Nitrogen And Phosphorus

nutrients from anthropogenic pollution can degrade water quality and alter the balance of marine food webs. lying at the base of the trophic pyramid, plankton quickly respond to nutrient changes in the water, which can have repercussions throughout both pelagic and benthic food webs, and thus they serve as a good bioindicator of water quality. In early november 2009, we evaluated sediment pollution, water pollution, and plankton abundance at four shoreline sites in the San Francisco Bay. We tested the sediment for nitrogen, phosphorus, potassium, and pH levels, all factors that can affect growth of primary producers. In the water, we tested nitrate, phosphate, and pH levels. lastly, we sampled shoreline plankton abundance both morning and evening. Sediment phosphorus and water phosphates were strongly correlated with one another, but water nitrates remained relatively constant, at low levels, across sites. daytime plankton abundance showed a positive trend with water phosphate. these trends suggest nitrogen is quickly taken up by plankton, making nitrogen the limiting factor for them. the relationship between plankton and phosphorus is influenced by more complex factors

Where are resilience-based management strategies appropriate for coral reefs? Mapping environmental conditions and trends in coral cover in Guam and American Samoa

Resilience-based management strategies are gaining attention as tools to improve coral survival and recovery under increasingly stressful conditions. Prioritizing locations to implement these strategies depends on knowing where corals already show potential signs of resilience and how environmental conditions may shift with climate change. We synthesized environmental conditions and coral cover trends in Guam and American Samoa using present-day climate conditions and 2 future climate scenarios: Representative Concentration Pathways 4.5 and 8.5. We examined the spatial overlap between favorable and unfavorable environmental conditions and locations where coral reefs have maintained or increased coral cover over the past decade. Locations representing 4 combinations of the aforementioned characteristics may be subject to different management strategies: (1) conservation and restoration of robust corals, (2) restoration of declining corals, (3) conservation of genetic material of robust corals and stressor mitigation, and (4) no clear strategy for declining corals. We estimated areas in which multiple management actions could be performed based on these combinations. Under present-day climate conditions, the conservation of genetic material and stressor mitigation were overrepresented in Guam, comprising 23% of the study area; this declined to 15% in future climate scenarios. Coral restoration was at first underrepresented (0%). In American Samoa, the proportional area for each strategy remained consistent regardless of climate. Coral restoration was overrepresented, comprising 54% to 56% of the study area, whereas the conservation of genetic material and stressor mitigation were underrepresented (9% to 11%, respectively). Our approach offers a rapid way to assess where potential management actions could be applied based on data aggregated over large spatial extents, which can complement more detailed, labor-intensive assessments of reef community dynamics, particularly if distinct coral communities inform the boundaries of aggregation units. These results may guide managers in selecting ecologically suitable locations for implementing resilience-based management strategies for coral reefs.

Reduction and recovery of keystone predation pressure after disease-related mass mortality.

Disturbances such as disease can reshape communities through interruption of ecological interactions. Changes to population demographics alter how effectively a species performs its ecological role. While a population may recover in density, this may not translate to recovery of ecological function. In 2013, a sea star wasting syndrome outbreak caused mass mortality of the keystone predator Pisaster ochraceus on the North American Pacific coast. We analyzed sea star counts, biomass, size distributions, and recruitment from long-term intertidal monitoring sites from San Diego to Alaska to assess regional trends in sea star recovery following the outbreak. Recruitment, an indicator of population recovery, has been spatially patchy and varied within and among regions of the coast. Despite sea star counts approaching predisease numbers, sea star biomass, a measure of predation potential on the mussel Mytilus californianus, has remained low. This indicates that post-outbreak populations have not regained their full predation pressure. The regional variability in percent of recovering sites suggested differences in factors promoting sea star recovery between regions but did not show consistent patterns in postoutbreak recruitment on a coast-wide scale. These results shape predictions of where changes in community composition are likely to occur in years following the disease outbreak and provide insight into how populations of keystone species resume their ecological roles following mortality-inducing disturbances

Reduction and recovery of keystone predation pressure after disease-related mass mortality.

Disturbances such as disease can reshape communities through interruption of ecological interactions. Changes to population demographics alter how effectively a species performs its ecological role. While a population may recover in density, this may not translate to recovery of ecological function. In 2013, a sea star wasting syndrome outbreak caused mass mortality of the keystone predator Pisaster ochraceus on the North American Pacific coast. We analyzed sea star counts, biomass, size distributions, and recruitment from long-term intertidal monitoring sites from San Diego to Alaska to assess regional trends in sea star recovery following the outbreak. Recruitment, an indicator of population recovery, has been spatially patchy and varied within and among regions of the coast. Despite sea star counts approaching predisease numbers, sea star biomass, a measure of predation potential on the mussel Mytilus californianus, has remained low. This indicates that post-outbreak populations have not regained their full predation pressure. The regional variability in percent of recovering sites suggested differences in factors promoting sea star recovery between regions but did not show consistent patterns in postoutbreak recruitment on a coast-wide scale. These results shape predictions of where changes in community composition are likely to occur in years following the disease outbreak and provide insight into how populations of keystone species resume their ecological roles following mortality-inducing disturbances