Environmental regimes in the Caribbean and implications for the dynamics and distribution of its coral reefs

Over evolutionary time coral reefs have been exposed to the influence of diverse environmental forces which have determined their structure and function. However, the climate of the earth is changing, affecting many biological systems, including coral reefs. Through this thesis the static and dynamic environment of the Caribbean basin was characterized using remote sensing and in situ data sources. This information was used to understand how present environmental conditions have shaped reef ecosystems and how the changing climate might jeopardize them. Focusing on physical constraints that drive many aspects of coastal ecology, a region-wide categorisation of the Physical Environments of the Caribbean Sea (PECS) was developed. The classification approach is hierarchical; including a first level of 16 physicochemical provinces based on sea surface temperature, turbidity and salinity data; and a second level considering mechanical disturbance from wave exposure and hurricanes. The PECS categorisation will facilitate comparative analyses and inform the stratification of studies across environmental provinces in the region. Montastraea spp. forereef habitats have the highest biodiversity and support the largest number of ecosystem processes and services in the Caribbean. One of the aspects of the physical environment, wave exposure, was used to predict the distribution of these habitats in the Caribbean basin with high accuracy (79%). The distribution of the habitat is constrained in environments of high exposure, a pattern likely to be driven by high rates of chronic sediment scour that constrain recruitment. This approach constitutes a fast and inexpensive alternative to traditional habitat mapping and complements global efforts to map reef extent. Recent changes in temperature have impacted ecosystem function across the globe. However, the nature of the responses has depended upon the rate of change of temperature and the season when the changes occur, which are spatially variable. In the Caribbean Sea, temperature trends are highly variable in space (ranging from -0.20 to 0.54°C decade-1) and most of the warming has been due to increases in summer temperatures. The highly detailed spatial and temporal patterns assessed can be used to elucidate observed ecological responses to climatic change in the region. In the face of increased temperatures it has been suggested that reefs may become increasingly restricted to locations of naturally low thermal stress, such as upwelling areas. However, when analysing the degree to which seasonal upwelling reduces the local thermal stress experienced by corals, it is clear that upwelling areas do not always offer meaningful protection. Hypothesised areas need to be assessed individually in order to evaluate their capacity as a refuge against climate change. In this thesis large progress has been made in assessing the ocean climate of the Caribbean basin by quantifying spatial patterns and their rate of change. Although some insight into the consequences of these seascape patterns to the function and distribution of marine systems has been provided, more can be done to fully exploit the datasets produced

Physical environments of the Caribbean Sea

The Caribbean Sea encompasses a vast range of physical environmental conditions that have a profound influence on the organisms that live there. Here we utilize a range of satellite and in situ products to undertake a region-wide categorization of the physical environments of the Caribbean Sea (PECS). The classification approach is hierarchical and focuses on physical constraints that drive many aspects of coastal ecology, including species distributions, ecosystem function, and disturbance. The first level represents physicochemical properties including metrics of satellite sea surface temperature, water clarity, and in situ salinity. The second level considers mechanical disturbance and includes both chronic disturbance from wind-driven wave exposure and acute disturbance from hurricanes. The maps have a spatial resolution of 1 km. An unsupervised neural network classification produced 16 physicochemical provinces that can be categorized into six broad groups: (1) low water clarity and low salinity and average temperatures; (2) low water clarity but average salinity and temperature, broadly distributed in the basin; (3) low salinity but average water clarity and temperature; (4) upwelling; (5) high latitude; and (6) offshore waters of the inner Caribbean. Additional mechanical disturbance layers impose additional pattern that operates over different spatial scales. Because physical environments underpin so much of coastal ecosystem structure and function, we anticipate that the PECS classification, which will be freely distributed as geographic information system layers, will facilitate comparative analyses and inform the stratification of studies across environmental provinces in the Caribbean basin

Reefs of last resort: locating and assessing thermal refugia in the wider Caribbean

Ocean temperature increase is recognised as one of the major threats to the future of coral reefs. During the past 50. years, global mean temperatures have risen by 0.13. °C/decade, but in the Caribbean warming trends are greater, and are of the order of 0.29. °C/decade. In light of this threat, some researchers have proposed that reefs may survive better in locations of naturally low thermal stress, and have hypothesised that such refugia may be located in: (1) deep areas; (2) areas of high currents; (3) upwelling; and (4) high-latitude areas. These regions have been targeted as priorities for conservation activities; however, with the exception of deep reefs, formal assessment of the efficacy of these potential refugia is lacking. Here we tested the three remaining hypotheses in the wider Caribbean region using remotely sensed data and hydrodynamic model outputs. We began by determining the location of the hypothesised refugia, and then quantified the extent to which they minimise acute and chronic thermal stress in a significant and consistent manner through time. Furthermore, recognising the increasing sea warming and the concern that high temperatures could frequently exceed lethal thresholds for many organisms in the future, we assessed the ability of these areas to slow the rates of increase of temperatures. We show that the proposed areas do not constitute meaningful refugia from acute thermal stress. However, upwelling areas in the Caribbean have conservation utility because rates of thermal warming are lower

Environmental regimes in the Caribbean and implications for the dynamics and distribution of its coral reefs

Over evolutionary time coral reefs have been exposed to the influence of diverse environmental forces which have determined their structure and function. However, the climate of the earth is changing, affecting many biological systems, including coral reefs. Through this thesis the static and dynamic environment of the Caribbean basin was characterized using remote sensing and in situ data sources. This information was used to understand how present environmental conditions have shaped reef ecosystems and how the changing climate might jeopardize them. Focusing on physical constraints that drive many aspects of coastal ecology, a region-wide categorisation of the Physical Environments of the Caribbean Sea (PECS) was developed. The classification approach is hierarchical; including a first level of 16 physicochemical provinces based on sea surface temperature, turbidity and salinity data; and a second level considering mechanical disturbance from wave exposure and hurricanes. The PECS categorisation will facilitate comparative analyses and inform the stratification of studies across environmental provinces in the region. Montastraea spp. forereef habitats have the highest biodiversity and support the largest number of ecosystem processes and services in the Caribbean. One of the aspects of the physical environment, wave exposure, was used to predict the distribution of these habitats in the Caribbean basin with high accuracy (79%). The distribution of the habitat is constrained in environments of high exposure, a pattern likely to be driven by high rates of chronic sediment scour that constrain recruitment. This approach constitutes a fast and inexpensive alternative to traditional habitat mapping and complements global efforts to map reef extent. Recent changes in temperature have impacted ecosystem function across the globe. However, the nature of the responses has depended upon the rate of change of temperature and the season when the changes occur, which are spatially variable. In the Caribbean Sea, temperature trends are highly variable in space (ranging from -0.20 to 0.54°C decade-1) and most of the warming has been due to increases in summer temperatures. The highly detailed spatial and temporal patterns assessed can be used to elucidate observed ecological responses to climatic change in the region. In the face of increased temperatures it has been suggested that reefs may become increasingly restricted to locations of naturally low thermal stress, such as upwelling areas. However, when analysing the degree to which seasonal upwelling reduces the local thermal stress experienced by corals, it is clear that upwelling areas do not always offer meaningful protection. Hypothesised areas need to be assessed individually in order to evaluate their capacity as a refuge against climate change. In this thesis large progress has been made in assessing the ocean climate of the Caribbean basin by quantifying spatial patterns and their rate of change. Although some insight into the consequences of these seascape patterns to the function and distribution of marine systems has been provided, more can be done to fully exploit the datasets produced.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Source data for Plos ONE publication Redefining thermal regimes to design reserves for coral reefs in the face of climate change

Reef managers cannot fight global warming through mitigation at local scale, but they can use information on thermal patterns to plan for reserve networks that maximize the probability of persistence of their reef system. Here we assess previous methods for the design of reserves for climate change and present a new approach to prioritize areas for conservation that leverages the most desirable properties of previous approaches. The new method moves the science of reserve design for climate change a step forwards by: (1) recognizing the role of seasonal acclimation in increasing the limits of environmental tolerance of corals and ameliorating the bleaching response; (2) including information from several bleaching events, which frequency is likely to increase in the future; (3) assessing relevant variability at country scales, where most management plans are carried out. We demonstrate the method in Honduras, where a reassessment of the marine spatial plan is in progress

Dall'altra parte della Rivoluzione

Reef managers cannot fight global warming through mitigation at local scale, but they can use information on thermal patterns to plan for reserve networks that maximize the probability of persistence of their reef system. Here we assess previous methods for the design of reserves for climate change and present a new approach to prioritize areas for conservation that leverages the most desirable properties of previous approaches. The new method moves the science of reserve design for climate change a step forwards by: (1) recognizing the role of seasonal acclimation in increasing the limits of environmental tolerance of corals and ameliorating the bleaching response; (2) using the best proxy for acclimatization currently available; (3) including information from several bleaching events, which frequency is likely to increase in the future; (4) assessing relevant variability at country scales, where most management plans are carried out. We demonstrate the method in Honduras, where a reassessment of the marine spatial plan is in progress

Upwelling areas do not guarantee refuge for coral reefs in a warming ocean

Global warming is a severe threat to coral reefs. It has been proposed that upwelling could minimise the thermal stress caused by ocean warming, and therefore upwelling areas may serve as a refuge for corals. Here, using 21 yr of satellite sea surface temperature data, we analysed the degree to which the thermal stress experienced by corals is reduced in 4 seasonal upwelling areas with reef development: Colombia in the southern Caribbean, Panama in the eastern tropical Pacific, Oman in the Arabian Sea and Madagascar in the Indian Ocean. Upwelling areas do not always offer protection from thermal stress. When compared with nearby non-upwelling areas, upwelling can only provide defence against warming events if: (1) the threat and the upwelling coincide, and (2) this overlap produces a meaningful decrease in thermal stress in upwelling areas. These conditions were met in only 2 of the 4 upwelling areas analysed: Colombia and Oman. In Oman, upwelling decreased the magnitude, frequency and duration of thermal disturbances (identified when Coral Bleaching HotSpots, anomalies exceeding the average temperature of the warmest month, are larger than 1°C), while in Colombia upwelling only decreased their frequency. The protective role of upwelling seems to be limited geographically; therefore, further upwelling areas need to be assessed individually in order to evaluate their capacity as a refuge from thermal stress. © Inter-Research 2010

Quantifying the squeezing or stretching of fisheries as they adapt to displacement by marine reserves

The designation of no-take marine reserves involves social and economic concerns due to the resulting displacement of fishing effort, when fishing rights are removed from those who traditionally fished within an area. Displacement can influence the functioning of the fishery and success of the reserve, yet levels of displacement are seldom quantified after reserve implementation and very rarely before that. We devised a simple analytical framework based on set theory to facilitate reserve placement. Implementation of the framework requires maps of fishing grounds, fishing effort, or catch per unit effort for at least 2 years. The framework quantifies the level of conflict that a reserve designation might cause in the fishing sector due to displacement and the opportunities to offset the conflict through fisher spatial mobility (i.e., ability of fishers to fish elsewhere). We also considered how the outputs of the framework can be used to identify targeted management interventions for each fishery. We applied the method in Honduras, where the largest marine protected area in Central America is being placed, for which spatial data on fishing effort were available for 6 fisheries over 3 years. The proposed closure had a greater negative impact on the shrimp and lobster scuba fisheries, which concentrated respectively 28% and 18% of their effort inside the reserve. These fisheries could not accommodate the displacement within existing fishing grounds. Both would be forced to stretch into new fishing grounds, which are available but are of unknown quality. These stakeholders will likely require compensation to offset costly exploratory fishing or to travel to fishing grounds farther away from port