Oliver Zielinski

Comparison of remote sensing reflectance from above-water and in-water measurements west of Greenland, Labrador Sea, Denmark Strait, and west of Iceland

The need to obtain ocean color essential climate variables (OC-ECVs) using hyperspectral technology has gained increased interest in recent years. Assessing ocean color on a large scale in high latitude environments using satellite remote sensing is constrained by polar environmental conditions. Nevertheless, on a small scale we can assess ocean color using above-water and in-water remote sensing. Unfortunately, above-water remote sensing can only determine apparent optical properties leaving the sea surface and is susceptible to near surface environmental conditions for example sky and sunglint. Consequently, we have to rely on accurate in-water remote sensing as it can provide both synoptic inherent and apparent optical properties of seawater. We use normalized water leaving radiance LWN or the equivalent remote sensing reflectance RRS from 27 stations to compare the differences in above-water and in-water OC-ECVs. Analysis of above-water and in-water RRS spectra provided very good match-ups (R2 > 0.97, MSE < 1.8*10(-7)) for all stations. The unbiased percent differences (UPD) between above-water and in-water approaches were determined at common OC-ECVs spectral bands (410, 440, 490, 510 and 555) nm and the classic band ratio (490/555) nm. The spectral average UPD ranged (5 - 110) % and band ratio UPD ranged (0 - 12) %, the latter showing that the 5% uncertainty threshold for ocean color radiometric products is attainable. UPD analysis of these stations West of Greenland, Labrador Sea, Denmark Strait and West of Iceland also suggests that the differences observed are likely a result of environmental and instrumental perturbations.

TECHNICAL REALIZATION OF EXTENSIVE AQUACULTURE CONSTRUCTIONS IN OFFSHORE WIND FARMS: CONSIDERATION OF THE MECHANICAL LOADS

The presented study focuses on the development of offshore wind farms in conjunction with open ocean aquaculture within the German Bight. For aquaculture enterprises in the open ocean an extensive cultivation of various species, blue mussels (Mytilus edulis), oysters

Citizens and satellites: Assessment of phytoplankton dynamics in a NW Mediterranean aquaculture zone

Abstract Ocean colour measurements from space are well suited to assess phytoplankton dynamics over broad spatial scales. Closer to the coast however, the quality of these data degrades as a result of the loading of sediments and dissolved matter from terrestrial runoff, the influences of land reflection on atmospheric correction and sea-bottom reflection, which compromise their use in coastal management actions. Recently, the enabling of citizens to provide environmental observations has gained recognition as a way for enhancing the spatio-temporal coverage of satellite observations. In the FP7 funded EU project “Citclops” (Citizens’ observatory for coast and ocean optical monitoring), a smart phone app for the classification of water colour, simplified to 21 hues of the Forel Ule (FU) scale, is developed. In this study we examine two bays in the Ebro Delta (NW Mediterranean) where satellite data, hyperspectral measurements, and observations with the citizen tool for colour comparison were available. FU values and their corresponding novel colorimetric parameter, the hue colour angle, were derived in the bay at 12 stations with the traditional FU scale and one automated in-situ radiometric system at the Alfacs Bay aquaculture site. Both methods complied well during the study course of May–June 2011. These measurements were further compared to data from Full Resolution MERIS (Medium Resolution Imaging Spectrometer) satellite images. The quality of the retrieved hue angle varies over the image. For high-quality sites, MERIS hue colour angles and FU values gave a good estimate of seasonal algal dynamics in the bays over the year 2011, while ground measurements revealed colour changes over short space- and time frames, which are indicative of the fast dynamics of phytoplankton in the area that could not be fully resolved with MERIS data. The use of FU values and hue colour angle of water will allow a simple integration of data from hyperspectral measurements, MERIS multispectral observations and citizens observations with the (Citclops/EyeOnWater) water colour app. Such observational data can be included to local monitoring efforts, and can also foster an increased interest of the general public to local environmental management and governance issues.

Physical, Bio-Optical State and Correlations in North–Western European Shelf Seas

Color of seawater has become an integral tool in understanding surface marine ecosystems and processes. In this paper we seek to assess the correlations and consequently the potential of using shipborne remote sensing products to infer marine environmental parameters. Typical seawater parameters are chlorophyll–a (chl–a), colored dissolved organic material (CDOM), suspended particulate material (SPM), Secchi–disk depth (SDD), temperature, and salinity. These parameters and radiometric quantities were observed from a total of 60 stations covering German Bight, North Sea, Inner Seas, Irish Sea, and Celtic Sea. Bio-optical models developed in this study were used to predict the in situ measured parameters, with low mean unbiased percent differences and absolute percent difference less than 35%. Our investigations show that the use of ocean color products namely the Forel–Ule Index to infer seawater parameters is encouraging. The constrained spatial and temporal span of measured in situ parameters does limit the accuracy of our models. Absorption coefficients of the main color producing agents CDOM, chl–a, and inorganic fraction of SPM (iSPM) were determined to estimate absorption budgets. During the field campaign, iSPM was the primary light absorber over the spectral range (400–700 nm) although variabilities were observed in the regional seas.

Towards Selective Tidal-Stream Transport for Lagrangian profilers

Autonomous Lagrangian profilers are widely used as measurement and monitoring platforms. In their current mode of operation, the profilers usually drift passively at their parking depth before making a vertical profile to go back to the surface. This paper presents a control strategy to actively select and use tidal currents so that a profiler can autonomously reach a desired destination. After presenting the profiler and possible modifications for a coastal environment, we introduce simple mathematical models for the profiler and its environment. We then present a feedback controller that, taking into account the direction of oscillating tidal currents, is able to steer the profiler to any horizontal location. For illustration, we also give a few simulation results using tidal current data from the North Sea.

Sunglint Detection for Unmanned and Automated Platforms

We present an empirical quality control protocol for above-water radiometric sampling focussing on identifying sunglint situations. Using hyperspectral radiometers, measurements were taken on an automated and unmanned seaborne platform in northwest European shelf seas. In parallel, a camera system was used to capture sea surface and sky images of the investigated points. The quality control consists of meteorological flags, to mask dusk, dawn, precipitation and low light conditions, utilizing incoming solar irradiance (ES) spectra. Using 629 from a total of 3,121 spectral measurements that passed the test conditions of the meteorological flagging, a new sunglint flag was developed. To predict sunglint conspicuous in the simultaneously available sea surface images a sunglint image detection algorithm was developed and implemented. Applying this algorithm, two sets of data, one with (having too much or detectable white pixels or sunglint) and one without sunglint (having least visible/detectable white pixel or sunglint), were derived. To identify the most effective sunglint flagging criteria we evaluated the spectral characteristics of these two data sets using water leaving radiance (LW) and remote sensing reflectance (RRS). Spectral conditions satisfying ‘mean LW (700–950 nm) < 2 mW·m−2·nm−1·Sr−1’ or alternatively ‘minimum RRS (700–950 nm) < 0.010 Sr−1’, mask most measurements affected by sunglint, providing an efficient empirical flagging of sunglint in automated quality control.

Citizen Bio-Optical Observations from Coast- and Ocean and Their Compatibility with Ocean Colour Satellite Measurements

Marine processes are observed with sensors from both the ground and space over large spatio-temporal scales. Citizen-based contributions can fill observational gaps and increase environmental stewardship amongst the public. For this purpose, tools and methods for citizen science need to (1) complement existing datasets; and (2) be affordable, while appealing to different user and developer groups. In this article, tools and methods developed in the 7th Framework Programme of European Union (EU FP 7) funded project Citclops (citizens’ observatories for coast and ocean optical monitoring) are reviewed. Tools range from a stand-alone smartphone app to devices with Arduino and 3-D printing, and hence are attractive to a diversity of users; from the general public to more specified maker- and open labware movements. Standardization to common water quality parameters and methods allows long-term storage in regular marine data repositories, such as SeaDataNet and EMODnet, thereby providing open data access. Due to the given intercomparability to existing remote sensing datasets, these tools are ready to complement the marine datapool. In the future, such combined satellite and citizen observations may set measurements by the engaged public in a larger context and hence increase their individual meaning. In a wider sense, a synoptic use can support research, management authorities, and societies at large.

Requirements and approaches for a more cost-efficient assessment of ocean waters and ecosystems, and fisheries management

Development of a new generation of multifunctional sensor systems is underway to address ocean monitoring challenges. These range from more precise monitoring of the marine environment to an improved management of fisheries and, among other things, address improved life cycle cost-efficiency. These advances will be achieved through innovations such as multiplatform integration, greater reliability through better antifouling management and greater sensor and data interoperability. Requirements for the sensors have been refined through surveys and discussions with science and industry users. This paper will describe these developments in the NeXOS project.

Detection and identification of hydrocarbons in marine waters using time-resolved laser-fluorescence: Set-up and first results of a new submersible sensor

Highly sensitive laser-induced time-resolved fluorescence spectrometry offers a fast and reagent-free analytical method for the detection and distinction of hydrocarbons in water. It has a significant potential for a wide range of marine applications as a submersible solution, e.g. for long-term application in environmental monitoring or observation tasks in the offshore oil and gas industry in combination with remotely operated vehicles. The objective of the project “subLIF” (submersible time-resolved Laser-Induced Fluorescence sensor) is the development of a real-time, reagent-free in situ detection system for the identification and quantification of hydrocarbons in natural waters. Within this paper we present the set-up and first results achieved with the prototype of the innovative measuring cell under laboratory conditions as well as the sensor principle and the applied detection-system of the “subLIF” project.

In Situ Observations of Biological and Environmental Parameters by Means of Optics—Development of Next-Generation Ocean Sensors With Special Focus on an Integrating Cavity Approach

To meet the requirements of increasing environmental awareness in aquatic ecosystems, optical techniques offer a fast and reliable opportunity for a wide range of applications providing high-resolution measurements. In this respect, important parameters which have to be addressed include phytoplankton biomass and taxonomic composition, total suspended matter, dissolved organic matter, as well as hazardous substances, e.g., polycyclic aromatic hydrocarbons (PAHs). Requiring comparable low effort, optical methods are a convenient and noninvasive way to derive information on the optical active substances in different water bodies. Various approaches and devices are available, either aiming on the determination of the waters inherent optical properties or on measuring the fluorescence properties of different constituents. This contribution presents the objectives and measurement principles of two new optical sensor developments in this respect. A special focus lies on an integrating cavity approach for hyperspectral absorption measurement. This approach overcomes two common problems in classical absorption measurement of seawater: 1) usually low concentration of absorbing material in the water negatively affecting accurate measurements of untreated samples; and 2) errors introduced by light scattering of particles requiring empirical corrections to obtain good accuracy. To combine these advantages with the possibilities of automated, long-term high-frequency measurements, an integrating cavity was adapted for flow-through operation. First field results obtained by the resulting Hyperspectral Absorption Sensor (HyAbS) in the North Sea and off the Norwegian coast are evaluated and compared with discrete measurements. The second development is a matrix-fluorescence sensor with flexible wavelength configuration for the detection and characterization of dissolved substances, such as fluorescent dissolved organic matter (FDOM) and PAHs. Here, the measurement principle of the sensor and first field results from a related, laboratory-based method will be presented as a preliminary work necessary for the development of the final in situ sensor. Furthermore, future plans for both instruments as well as a possible combination will be discussed. In summary, both approaches have the potential to be multiparameter instruments for high-resolution measurements of environmental parameters.