A review of the ocean science and technology partnership between US and Korea

In 2001, the National Oceanic and Atmospheric Administration (NOAA) and the Ministry of Maritime Affairs and Fisheries Integrated Coastal and Ocean Resources Scientific and Technical Arrangement was signed to pursue scientific and technical cooperation in integrated coastal and ocean resources management in the mutual interest of the participants. Over the last 6 years, the cooperation has been very beneficial, particularly for advancing marine science and management programs in Korea, such as Deep Sea Aquaculture, Sea Grant College Program, Marine Protected Areas, and Ocean Observations. The benefits to NOAA from the cooperation include Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, ocean and coastal observations, GEOSS program, and Global Program of Action. Also the cooperation has spillover effects on other ocean science and technological arrangement between US and Korea. This article reviews purpose, obstacles, and achievement of the cooperation and suggests recommendations for the future steps.     

Difficulties in separating hurricane induced effects from natural benthic succession: Hurricane Isabel,a case study from Eastern Virginia,USA

Hurricane Isabel reached the Eastern seaboard of North America on 18 September 2003 causing estimated damage >3 billion US dollars and the death of ∼50 people. Isabel is considered to be one of the most significant tropical cyclones to affect Virginia, since the Chesapeake Potomac Hurricane of 1933 and Hurricane Hazel in 1954. A study of the temporal changes in the benthic fauna pre- and post-hurricane was conducted on an intertidal sandflat within the dynamic barrier island system near Wachapreague, Eastern Virginia. Replicate sediment cores were collected 3 weeks before Isabel made landfall and further samples were collected on 5 occasions over the following 20 months. An immediate effect of Isabel was a doubling in the number of species, a significant increase in invertebrate species diversity (H′) and a rise in opportunistic species and deposit feeders, but a non-significant increase in the total number of organisms. Changes in infauna occurred such that by the end of the study there were significantly increased numbers of species, faunal abundances and community diversity measures, as compared with pre-hurricane samples, suggesting a potentially positive medium-term effect of this hurricane perturbation. The most notable direct effects of the hurricane were on the relative abundances of feeding guilds with a reduction in interface feeders from 87% pre-hurricane to 64% post-hurricane, and an increase in surface deposit feeders from 7% pre-hurricane to 20% post-hurricane. The study highlights potential problems in interpreting post-perturbation data when insufficient pre-perturbation data exist.     

The mid-depth circulation of the northwestern tropical Atlantic observed by floats

A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16°N between the Antilles islands and the Mid-Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADW east of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.     

Combining pixel and object based image analysis of ultra-high resolution multibeam bathymetry and backscatter for habitat mapping in shallow marine waters

Habitat mapping data are increasingly being recognised for their importance in underpinning marine spatial planning. The ability to collect ultra-high resolution (cm) multibeam echosounder (MBES) data in shallow waters has facilitated understanding of the fine-scale distribution of benthic habitats in these areas that are often prone to human disturbance. Developing quantitative and objective approaches to integrate MBES data with ground observations for predictive modelling is essential for ensuring repeatability and providing confidence measures for habitat mapping products. Whilst supervised classification approaches are becoming more common, users are often faced with a decision whether to implement a pixel based (PB) or an object based (OB) image analysis approach, with often limited understanding of the potential influence of that decision on final map products and relative importance of data inputs to patterns observed. In this study, we apply an ensemble learning approach capable of integrating PB and OB Image Analysis from ultra-high resolution MBES bathymetry and backscatter data for mapping benthic habitats in Refuge Cove, a temperate coastal embayment in south-east Australia. We demonstrate the relative importance of PB and OB seafloor derivatives for the five broad benthic habitats that dominate the site. We found that OB and PB approaches performed well with differences in classification accuracy but not discernible statistically. However, a model incorporating elements of both approaches proved to be significantly more accurate than OB or PB methods alone and demonstrate the benefits of using MBES bathymetry and backscatter combined for class discrimination.     

The potential of wetlands in reducing storm surge

A critical component of flood protection in some coastal areas is expected to be the potential contribution of wetlands to the lowering of surges as they propagate inland from the coast. Consequently, an accurate method to quantify the effect of wetlands on coastal surge levels is required. The degree to which wetlands attenuate surge is the subject of debate and difficult to assess. The potential of wetlands to reduce storm surge has typically been expressed as a constant attenuation rate, but the relationship is much more complex. A numerical storm surge model was applied to assess the sensitivity of surge response to specified wetland loss. Results suggest that wetlands do have the potential to reduce surges but the magnitude of attenuation is dependent on the surrounding coastal landscape and the strength and duration of the storm forcing. Numerical models that simulate the relevant physical processes can provide valuable information on how to best integrate wetlands into coastal protection plans. However, while the model applied for this study has displayed skill in estimating surges over wetlands, the formulations are missing key processes and model advancements are necessary.     

The effects of trophic interactions and spatial competition on algal community composition on Hawaiian coral reefs

Much of coral reef ecology has focused on how human impacts change coral reefs to macroalgal reefs. However, macroalgae may not always be a good indicator of reef decline, especially on reefs with significant sea urchin populations, as found in Kenya and Hawaii. This study tests the effects of trophic interactions (i.e. herbivory by fishes and sea urchins) and spatial competition (between algae and coral) on algal community structure of reefs surrounding two Hawaiian Islands that vary in their level of human impacts. Reef‐building organisms (corals and crustose coralline algae) were less abundant and turf algae were more abundant on Maui as compared to Lanai, where human impacts are lower. In contrast to previous studies, we found no evidence that macroalgae increased with human impacts. Instead, low turf and macroalgal abundance were best explained by the interactive effects of coral cover and sea urchin abundance. Fishing sea urchin predators appeared to have cascading effects on the benthic community. The absence of sea urchin predators and high sea urchin densities correspond to a disproportionately high abundance of turf and crustose coralline algae. We propose that high turf algal abundance is a better indicator of reef decline in Hawaii than high macroalgal abundance because turf abundance was highest on reefs with low coral cover and few fish. The results of this study emphasize that understanding changes in community composition are context‐dependent and that not all degraded reefs look the same.     

Guiding ecological principles for marine spatial planning

The declining health of marine ecosystems around the world is evidence that current piecemeal governance is inadequate to successfully support healthy coastal and ocean ecosystems and sustain human uses of the ocean. One proposed solution to this problem is ecosystem-based marine spatial planning (MSP), which is a process that informs the spatial distribution of activities in the ocean so that existing and emerging uses can be maintained, use conflicts reduced, and ecosystem health and services protected and sustained for future generations. Because a key goal of ecosystem-based MSP is to maintain the delivery of ecosystem services that humans want and need, it must be based on ecological principles that articulate the scientifically recognized attributes of healthy, functioning ecosystems. These principles should be incorporated into a decision-making framework with clearly defined targets for these ecological attributes. This paper identifies ecological principles for MSP based on a synthesis of previously suggested and/or operationalized principles, along with recommendations generated by a group of twenty ecologists and marine scientists with diverse backgrounds and perspectives on MSP. The proposed four main ecological principles to guide MSP—maintaining or restoring: native species diversity, habitat diversity and heterogeneity, key species, and connectivity—and two additional guidelines, the need to account for context and uncertainty, must be explicitly taken into account in the planning process. When applied in concert with social, economic, and governance principles, these ecological principles can inform the designation and siting of ocean uses and the management of activities in the ocean to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure sustainable economic and social benefits.     

Holocene and Eemian climatic optima in the Korean Peninsula based on textural and carbon isotopic records from the stalagmite of the Daeya Cave,South Korea

Textural and stable isotopic records from the absolute-dated stalagmite of the Daeya Cave (DY-1) provide new insights into the climatic evolution of the Korean Peninsula during the Holocene and Eemian climatic optima. The stalagmite yielded ages of 8572 ± 227 to 5907 ± 158 and 1,23,456 ± 535 to 1,19,837 ± 1089 years, which coincide with the Holocene and Eemian climatic optima, respectively. The stalagmite’s δ¹³C record closely resembles previously reported Chinese speleothem δ¹⁸O data. Thus it can be suggested that textural and geochemical results of the DY-1 reflect East Asian monsoon intensity, which is forced by summer insolation patterns in the northern hemisphere. Lighter carbon isotopic compositions, well-developed fibrous calcite crystals, and their relatively faster growth rate in the stalagmite sample are interpreted to reflect the warmest and wettest climate conditions of the Holocene and Eemian interglacials. Both climatic optima took place when insolation was decreasing from its maximum level, temperature in Greenland was highest, and sea level approached its maximum level. These climatic optima also coincide with decreasing Antarctic temperatures. Compared the DY-1 data to other proxies, it is suggested that the Holocene and Eemian climatic optima developed through a balance among boreal insolation, monsoon intensity, and sea level (also continental ice volume), which are the main climatic forcing factors in the northern hemisphere. These trends also follow the bi-polar seesaw mechanism as previously described.     

A nonlinear stability analysis of convection in a generalized incompressible fluid

Abstract

We establish a nonlinear stability result for convection in a generalized incompressible fluid. Both numerical calculations and an asymptotic analysis are carried out. The linear and nonlinear results are shown to be very close in both cases, implying that the region of possible subcritical instabilities is very small.

During this work I was supported by a research studentship awarded by the Science and Engineering Council of the United Kingdom.     

Differential effects of salinity changes on two estuarine fishes,Leiostomus xanthurus andMicropogonias undulatus

Salinity fluctuation has been proposed as an important determinant of estuarine fish distribution. To test this idea, we compared distribution, behavioral preference and physiological sensitivity of two juvenile estuarine fishes, spot (Leiostomus xanthurus) and croaker (Micropogonias undulatus), with respect to salinity change. In field collections, spot: croaker ratios were positively correlated with salinity variation. Subsequent behavioral observations revealed that croaker tend to cross a 10‰ salinity gradient less often than spot. We proposed that energetic costs of salinity adaptation may be higher for croaker, resulting in the observed avoidance behavior. Oxygen consumption rates over rapid salinity fluctuations showed no significant differences in metabolic response between species, although there was some indication that sensitivity changes with fish size. Apparently, juvenile spot and croaker are well-equipped to withstand extreme changes in salinity. We conclude that environmental factors correlated with salinity change may be responsible for distribution differences between these two abundant species.