Aquatic Domains Research Articles

Introduction: theorising heritage for the seas

ABSTRACT This Introduction makes the case for a more critical engagement with oceans and the maritime within critical heritage theory. We lay out a research agenda that more consciously foregrounds aquatic domains in debates about conservation, sovereignty, governance, state power, and the politics of memory. In laying the ground for the papers that follow, we portray oceanic geographies and maritime heritage as politically and culturally charged arenas in order to argue that oceans are far from neutral or culturally egalitarian spaces and are subject to human-imposed hierarchies and competing ontologies. We scrutinize the dynamic interplay between maritime and marine realms to challenge conventional understandings of space, territory, and ownership, advocating for a reimagined approach to heritage that recognizes the ocean’s pivotal role in shaping human history and culture.

Coastal inundation regime moderates the short-term effects of sediment and soil additions on seawater oxygen and greenhouse gas dynamics: a microcosm experiment

The frequency and persistence of tidal inundation varies along the coastal terrestrial-aquatic interface, from frequently inundated wetlands to rarely inundated upland forests. This inundation gradient controls soil and sediment biogeochemistry and influence the exchange of soils and sediments from terrestrial to aquatic domains. Although a rich literature exist on studies of the influence of tidal waters on the biogeochemistry of coastal ecosystem soils, few studies have experimentally addressed the reverse question: How do soils (or sediments) from different coastal ecosystems influence the biogeochemistry of the tidal waters that inundate them? To better understand initial responses of coastal waters that flood coastal wetlands and uplands, we conducted short-term laboratory experiments where seawater was amended with sediments and soils collected across regional gradients of inundation exposure (i.e., frequently to rarely inundated) for 14 sites across the Mid-Atlantic, USA. Measured changes in dissolved oxygen and greenhouse gas concentrations were used to calculate gas consumption or production rates occurring during seawater exposure to terrestrial materials. We also measured soil and water physical and chemical properties to explore potential drivers. We observed higher oxygen consumption rates for seawater incubated with soils/sediments from frequently inundated locations and higher carbon dioxide production for seawater incubated with soils from rarely inundated transect locations. Incubations with soil from rarely inundated sites produced the highest global warming potential, primarily driven by carbon dioxide and secondarily by nitrous oxide. We also found environmental drivers of gas rates varied notably between transect locations. Our findings indicate that seawater responses to soil and sediment inputs across coastal terrestrial-aquatic interfaces exhibit some consistent patterns and high intra- and inter-site variability, suggesting potential biogeochemical feedback loops as inundation regimes shift inland.

An Improved Scheme for Correcting Remote Spectral Surface Reflectance Simultaneously for Terrestrial BRDF and Water‐Surface Sunglint in Coastal Environments

AbstractGlobal spectroscopic missions, such as NASA’s Surface Biology and Geology, will observe coastal environments and must account for the optical properties of both land and sea. Specifically, they must consider reflectance effects that arise from interactions between surface structures and variable observing geometries that are unique to terrestrial and aquatic domains. Over vegetated surfaces, Bidirectional Reflectance Distribution Function (BDRF) effects must be corrected to consistently map vegetation properties. At the water surface interface, sunglint effects must be corrected to estimate water column and benthic properties. Current analyses focus on vegetation or aquatic domains and do not easily address environments with mixed water and vegetation cover. Wetland environments within global spectroscopic data sets will pose a challenge to correction methods when scientific applications in coastal regions require continuous reflectance correction over both surface types. Here, we present the first simultaneous treatment of terrestrial BRDF and aquatic sunglint in a wetland environment. We evaluate existing vegetation‐BRDF correction methods and pair them with sunglint correction of aquatic pixels. We test multiple sunglint correction strategies to produce continuous corrected products over both vegetation and water surfaces. We show that the addition of sunglint correction in wetland environments significantly reduces error between overlapping image regions. Comparisons between airborne and in situ data demonstrate sub‐percent error in remote estimates of water‐leaving reflectance. Our results demonstrate the importance of both BRDF and sunglint corrections in wetland environments. A unified treatment will be critical for global‐scale hyperspectral spectroscopy missions.

A unified approach to estimate land and water reflectances with uncertainties for coastal imaging spectroscopy

Coastal ecosystem studies using remote visible/infrared spectroscopy typically invert an atmospheric model to estimate the water-leaving reflectance signal. This inversion is challenging due to the confounding effects of turbid backscatter, atmospheric aerosols, and sun glint. Simultaneous estimation of the surface and atmosphere can resolve the ambiguity enabling spectral reflectance maps with rigorous uncertainty quantification. We demonstrate a simultaneous retrieval method that adapts the Optimal Estimation (OE) formalism of Rodgers (2000) to the coastal domain. We compare two surface representations: a parametric bio-optical model based on Inherent Optical Properties (IOPs); and an expressive statistical model that estimates reflectance in every instrument channel. The latter is suited to both land and water reflectance, enabling a unified analysis of terrestrial and aquatic domains. We test these models with both vector and scalar Radiative Transfer Models (RTMs). We report field experiments by two airborne instruments: NASA's Portable Remote Imaging SpectroMeter (PRISM) in an overflight of Santa Monica, California; and NASA's Next Generation Airborne Visible Infrared Imaging Spectrometer (AVIRIS-NG) in an overflight of the Wax Lake Delta and lower Atchafalaya River, Louisiana. In both cases, in situ validation measurements match remote water-leaving reflectance estimates to high accuracy. Posterior error predictions demonstrate a closed account of uncertainty in these coastal observations.

Editorial

The present Special Issue entitled “Italian Long-Term Ecological Research for understanding ecosystem diversity and functioning. Case studies from aquatic, terrestrial and transitional domains” is the first published collection of studies performed at LTER-Italy sites which address the diversity and dynamics of ecosystems in different domains in responses to natural and anthropogenic forcing.

Exploring variability in environmental impact risk from human activities across aquatic ecosystems

Aquatic ecosystems are under severe pressure. Human activities introduce an array of pressures that impact ecosystems and their components. In this study we focus on the aquatic domains of fresh, coastal and marine waters, including rivers, lakes and riparian habitats to transitional, coastal as well as shelf and oceanic habitats. In an environmental risk assessment approach, we identified impact chains that link 45 human activities through 31 pressures to 82 ecosystem components. In this linkage framework >22,000 activity-pressure-ecosystem component interactions were found across seven European case studies. We identified the environmental impact risk posed by each impact chain by first categorically weighting the interactions according to five criteria: spatial extent, dispersal potential, frequency of interaction, persistence of pressure and severity of the interaction, where extent, dispersal, frequency and persistence account for the exposure to risk (spatial and temporal), and the severity accounts for the consequence of the risk. After assigning a numerical score to each risk criterion, we came up with an overall environmental impact risk score for each impact chain. This risk score was analysed in terms of (1) the activities and pressures that introduce the greatest risk to European aquatic domains, and (2) the aquatic ecosystem components and realms that are at greatest risk from human activities. Activities related to energy production were relevant across the aquatic domains. Fishing was highly relevant in marine and environmental engineering in fresh waters. Chemical and physical pressures introduced the greatest risk to the aquatic realms. Ecosystem components that can be seen as ecotones between different ecosystems had high impact risk. We show how this information can be used in informing management on trade-offs in freshwater, coastal and marine resource use and aid decision-making.

Analysis of raw EEM fluorescence spectra - ICA and PARAFAC capabilities

Excitation-Emission fluorescence spectroscopy is a versatile technique and has been used to detect, characterize and quantify residual Dissolved Organic Matter (DOM) in aquatic domains. PARAllel FACtor Analysis (PARAFAC) has been extensively used in the analysis of excitation-emission matrices (EEM), allowing for a better identification and quantification of contributions resulting from spectral decomposition.In this work we have adapted Independent Component Analysis (ICA) in order to make it suitable to the analysis of three-way EEM datasets, and tested ICA and PARAFAC performances for the study of three available datasets (Claus, Dorrit and drEEM). Semi-empirical simulation allowed us to assess the impact of (a) sample size, (b) signal sources and (c) composition dependencies, and the presence of (d) unspecific signal contributions (e.g. light scattering) upon both algorithms.PARAFAC and ICA have similar performances in processing ideal three-way EEM datasets but, in the presence of non-trilinear responses, ICA leads to a more realistic approach, yielding a better decomposition of contributing sources and their identification and quantification. This makes this algorithm more suitable for the analysis of real, raw EEM data, without the need of preprocessing to remove any unspecific contributions.

The importance of landscape diversity for carbon fluxes at the landscape level: small‐scale heterogeneity matters

Landscapes can be viewed as spatially heterogeneous areas encompassing terrestrial and aquatic domains. To date, most landscape carbon (C) fluxes have been estimated by accounting for terrestrial ecosystems, while aquatic ecosystems have been largely neglected. However, a robust assessment of C fluxes on the landscape scale requires the estimation of fluxes within and between both landscape components. Here, we compiled data from the literature on C fluxes across the air–water interface from various landscape components. We simulated C emissions and uptake for five different scenarios which represent a gradient of increasing spatial heterogeneity within a temperate young moraine landscape: (I) a homogeneous landscape with only cropland and large lakes; (II) separation of the terrestrial domain into cropland and forest; (III) further separation into cropland, forest, and grassland; (IV) additional division of the aquatic area into large lakes and peatlands; and (V) further separation of the aquatic area into large lakes, peatlands, running waters, and small water bodies These simulations suggest that C fluxes at the landscape scale might depend on spatial heterogeneity and landscape diversity, among other factors. When we consider spatial heterogeneity and diversity alone, small inland waters appear to play a pivotal and previously underestimated role in landscape greenhouse gas emissions that may be regarded as C hot spots. Approaches focusing on the landscape scale will also enable improved projections of ecosystems’ responses to perturbations, e.g., due to global change and anthropogenic activities, and evaluations of the specific role individual landscape components play in regional C fluxes. WIREs Water 2016, 3:601–617. doi: 10.1002/wat2.1147This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Science of Water > Water and Environmental Change Science of Water > Water Quality

Multiannual phytoplankton trends in relation to environmental changes across aquatic domains: A case study from Sardinia (Mediterranean Sea)

We investigated multiannual trends in phytoplankton in relation to several environmental drivers. We analyzed ecological data collected during the past two decades from three aquatic sites: an artificial lake, a coastal lagoon, and a marine coastal area. Hydrographic, nutrient, and phytoplankton data were statistically analyzed to detect trends and interactions. In all ecosystems, the chlorophyll a concentration decreased with increasing abundance of small-sized phytoplankton. Phytoplankton dynamics were related to decreased nutrient concentrations in the lake, to dynamics of phosphorus and decreased salinity in the lagoon, and probably to combined top-down and bottom-up processes in the marine gulf.

Modeling Underwater Structures

For systems to become truly autonomous it is necessary that they be able to interact with complex real-world environments. In this article we investigate techniques and technologies to address the problem of the acquisition and representation of complex environments such as those found underwater. The underwater environment presents many challenges for robotic sensing including highly variable lighting and the presence of dynamic objects such as fish and suspended particulate matter. The dynamic six-degree-of-freedom nature of the environment presents further challenges due to unpredictable external forces such as current and surge. In order to address the complexities of the underwater environment we have developed a stereo vision-inertial sensing device that has been successfully deployed to reconstruct complex 3-D structures in both the aquatic and terrestrial domains. The sensor combines 3-D information, obtained using stereo vision, with 3DOF inertial data to construct 3-D models of the environment. Semiautomatic tools have been developed to aid in the conversion of these representations into semantically relevant primitives suitable for later processing. Reconstruction and segmentation of underwater structures obtained with the sensor are presented.

A generic metadata description for hydrodynamic model data

Sharing of data sets between numerical models is considered an important and pressing issue in the modeling community, because of (i) the time consumed to convert data sets and (ii) the need to connect different types of numerical codes to better map inter-connectedness of aquatic domains. One of the reasons for the data sharing problem arises from the lack of sufficient description of the data, or lack of metadata, which is due to the absence of a standardized framework for these metadata sets. This paper describes the development of a metadata framework for hydrodynamic data descriptions using the Geographic Information Metadata, 19115:2003 standard published by the International Standards Organization (ISO). This standard has been chosen not only because of its extent and adequacy to describe geospatial data, but also because of its widespread use and flexibility to extend the coverage. The latter is particularly important, as further extensions of the metadata standard are needed to provide a comprehensive metadata representation of hydrodynamics and their I/O data. In order to enable the community to share and reuse numerical code data sets, however, they need to be published in both human and machine understandable format. One such format is the Web Ontology language (OWL), whose syntax is compliant with the Extensible Markup Language (XML). In this paper, we present an extensive metadata profile using the available elements of ISO 19115:2003 as well as its extension rules. Based on the metadata profile, an explicit specification or ontology for the model data domain has been created using OWL. The use of OWL not only permits flexibility when extending the coverage but also to share data sets as resources across the internet as part of the Semantic Web. We demonstrate the use of the framework using a two-dimensional finite element code and its associated data sets.