FRAM

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Project title and acronym

Benthic ecology and biogeochemistry using Bathysnap and sediment oxygen profiling in the Arctic (ArcEcoBio)

Host facility

FRAM – FRontiers in Arctic marine Monitoring

Modality of Access

MoA2 – Partially remote (the presence of the user is required at some stage, e.g. for installing and uninstalling an instrument)

Description

We propose adding a Bathysnap sea floor observing system to the lander-type long term benthic observatory at FRAM for a period of one year. Combining Bathysnap visual information with oxygen microprofile time-series and other measurements carried out in the Benthic Boundary Layer with the same instrument would enable quantification of the arrival and fate of seasonal pulses of carbon-rich phytodetritus at the seafloor, as well as how the activity of benthic fauna relates to this process. This ‘phytodetritus’ is made up of sunken algae, microbes, as well as zooplankton and their fecal pellets and exuvae and represents the principal component of downward carbon transport over ecological time scales.

Bathysnap collects time-lapse photography of the seafloor at 4 hr intervals covering an area of  a few square meters with the effectively viewed area dependant on object type (Bett et al 2001). This is because different objects types have differing visibility depending in part on their size and coloration where larger brighter objects tend to have a larger effectively viewed area (see Buckland et al. 1994). While originally in film format, the system now uses a digital camera and flash system with a Deep-Sea Power & Light battery. The system is self-contained and does not need network integration and is deployable and recoverable as a free vehicle lander system with mooring above and is deployable from any standard research vessel without specialized equipment such as an ROV. At FRAM, Bathysnap will be mounted at the same lander frame that is used for time series observations of diffusive oxygen uptake (DOU) of the seafloor carried out by AWi by means of long term microprofiler measurements. DOU measurements serve as a proxy to quantify rates of microbial remineralization of organic matter. Equipped with stable fiberoptical microsensors the microprofiler repeatedly records

oxygen micro profiles for up to one year and complements Bathysnap imagery to simultaneously address dynamics in Phytodetritus supply as well as remineralization.Bathysnap systems have previously been used at the Porcupine Abyssal Plain (PAP; another Fix03 site) on a regular basis since 1989. Benthic time-lapse photography systems have also been deployed for similar research at Sta. M in the northeast Pacific since 1989. These systems have proved to be reliable and informative tools. Discovery has aided understanding processes related to pelagic benthic coupling, as well as connections between climate, surface conditions including productivity and the transport of sinking particulate organic carbon (POC) flux from the upper ocean to the deep sea and seafloor. Ultimately these systems can monitor the fate and influence of that POC on the seafloor. These tools can be used to document the variation in movement speeds of bioturbating megafauna and changes in physical features on the seafloor. On several occasions these systems have captured never before seen behaviours of seafloor life such as the laying down of an entropneust fecal cast, the formation and gradual breakdown of echiuran burrows, or other behaviours (Lampitt 1985, Smith et al. 2005). These photographic systems have also been able to disentangle the origin/composition of intense POC fluxes that were otherwise not observed by standard conical sedimentation traps (e.g., Parflux Sediment Trap, see Smith et al. 2008, 2013, 2014). They have also been used to document the activity rates of megafauna including their movement speeds and patterns (behaviours), the area of bioturbated seafloor over time for each taxon (Vardaro et al. 2009), and the time taken to process and repackage the seasonally deposited phytodetritus (Bett et al. 2001). Long term patterns of benthic megafauna communities at FRAM have been studied intensively based on imaging surveys and samples (e.g., Bergmann et al., 2011). This provides the required information to accompany the proposed high resolution time-series of seafloor dynamics and benthic activity patterns that is so far missing for this Arctic site.

Several questions of societal interest can be addressed when data are available synoptically from polar and temperate areas for particle fluxes studied with sediment trap moorings, photographic time-series observations, and variations in organic matter remineralisation obtained with a sediment oxygen microprofiler (see also Ruhl et al. 2011). For example, how do processes of pelagic-benthic coupling differ between polar and temperate seas in terms o the timing and intensity of visible phytodetritus coverage? How do the observed communities differ in terms of how they process this coverage via ingestion and bioturbation? What portions of the overall POC flux might be being missed by Parflux Sediment Traps and similar systems? How tightly does the arrival of visible phytodetritus correlate to benthic organic matter remineralisation over periods of days to months?

Remineralisation rates at the seafloor determine the share of organic carbon supply from the upper water column that is returned to the sea and eventually the atmosphere as inorganic carbon and the share that is sequestered in the sediments and removed from earth’s active carbon pool. Organic matter supply to the deep sea is not constant but changes seasonally and even from day to day as pulses of POC reach the seafloor during episodic export events. We expect that coupling the above methods at both PAP and FRAM using identical methodologies will provide an unprecedented insight in the questions posed.

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Project title and acronym

DYnamics of Nutrients using AutonoMous lnsTrumEnts in Fram Strait (DYNAMITE)

Host facility

FRAM – FRontiers in Arctic marine Monitoring

Modality of Access

MoA2 – Partially remote (the presence of the user is required at some stage, e.g. for installing and uninstalling an instrument)

Description

Rationale: Nutrients supplied to the Arctic Ocean (AO) from the Atlantic via Fram Strait and the Barents Sea Opening, Pacific via Bering Strait, and Rivers, support primary production in Arctic  shelf seas, leading to a net C02 sequestration via the biological carbon pump (MacGilchrist et al., 2014). Furthermore, the AO is a source of nutrients to the North Atlantic, supplying nutrients via Davis Strait and Fram Strait. Changes in the hydrological cycle at high northern latitudes has modified the input of fresh water, and consequently, the quality and quantity of nutrients to the AO. We do not understand present-day AO budget closure, and so we do not know how the AO biogeochemistry will respond to future climate change and how this will impact transports to the NAti.

Background: Torres-Valdes et al. (2013) provided a physically mass-balanced budget of dissolved

inorganic nutrients, nitrate [N], silicate [Si] and phosphate [P] for the AO. This study identified the AO as a net exporter of P and Si to the NAtl, but found the N budget to be balanced In spite  of large N loses via denitrification there. The relevance of these transports is that P supports the P demand for N fixation in the Atlantic Ocean and supply 90% of the Si fluxes to the NAtl. Most of the Si originates in Arctic rivers, implying that future impacts to the watersheds surrounding the AO will directly impact transports to the NAtl. In the case of P and N however, non-oceanic sources were found inadequate to account for the imbalances.

Previous work: The foregoing analyses lead to the hypothesis that oceanic transport of dissolved organic nutrients – nitrogen (DON) and phosphorus (DOP) – may account for the imbalances of N and Pin the budget. Recent work (Torres-Valdes et al., in prep.) suggests DON may account for the N lost to denitrification, with high DON transports via Fram Strait and the Barents Sea Opening. Although P remains an open question; DOP seems to account for only ~1s% of the imbalance. Furthermore, the transformation of organic nutrients by microbial communities from organic to inorganic forms during transport may influence composition.

Gaps in knowledge and solution: The scarcity of data and temporal resolution hinder our understanding of changes in nutrient transports. This arises primarily from the difficulties in accessing AO gateways year round. Instrumenting the FRAM observatory with recently developed in situ nutrient sensors and commercially available autonomous samplers provides the best solution at hand to deepen our knowledge of nutrient exchanges to/from the AO at Fram Strait. The National Oceanography Centre (NOC) ‘s Ocean Technology and Engineering group have developed state-of-the-art nitrate [Beaton et al. 2012] and phosphate [Legiret et al. 2013] lab-on-a-chip sensors that offer analytical performance equivalent to laboratory methods, and can be configured to perform two measurements per day for up to a year. The sensors have been tested in month-long deployments in coastal waters [Beaton et al. 2012], in rivers, on benthic landers, and are due to be trialed on oceanic gliders in August 2014. In this project we propose to deploy these instruments on the FRAM moorings to evaluate their performance whilst also providing critical data to answer questions of scientific interest.

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Project title and acronym

Ocean chemistry and acoustics in the gas hydrate-charged Fram Strait (GasFram}

Host facility

FRAM

Modality of Access

MoA2 – Partially remote (the presence of the user is required at some stage, e.g. for installing and uninstalling an instrument)

Description

Context and objectives

Today’s global warming development has turned the cold Arctic regions to a “hot spot” for energy, environment and climate research. Methane is known as a powerful green-house gas, 25 times more potent than C02 in terms of trapping heat in the atmosphere over a timeframe of 100 years. Scientists  at the Center for Arctic Gas Hydrate, Environment and Climate (CAGE) based in Trornse (Norway), together with colleagues at NGU (Norwegian Geological survey) and Akvaplan-niva, aim to find out the role of methane from Arctic gas hydrate in past, present and future climate change.

Seepage of methane gas bubbles released from the seabed has been observed in shallow water (<400m depth) offshore Svalbard (Knies et al., 2004; Hustoft et al., 2009; Westbrook et al., 2009; Berndt et al., 2014), and one of the goals of CAGE is to monitor these methane seeps and provide the link between potential sources of elevated methane concentrations and the reasons for variations. For this purpose, a long-term observatory will be deployed on the seafloor on one of the seepage areas for a period of ten years. This CAGE observatory will integrate a CTD recorder for temperature and salinity measurements, an ADCP for current measurement, pH and C02 sensors for acidification monitoring, and fluorometer, oxygen and methane sensors. In addition, a hydrophone will record and quantify bubble releases. Moreover, the hydrophone frequency ranges will allow for detecting marine mammals.

Access to the central HAUSGARTEN site within the FRAM observatory (79° 04,16’N / 4° 04,59’E, N2500m depth) will mainly serve as a reference site for the CAGE observatory in an area where no deep-water gas hydrate has been found. Concretely, we wish to add to the central HAUSGARTEN site at FRAM, for one year: 1) a self-logging methane sensor for local methane measurement (mainly background), 2) a CTD recorder for temperature and salinity time-series and 3) a self-sustained hydrophone for hydro-acoustic background. In addition, material/samples/data obtained from the  long-term lander-based benthic observatory in the central HAUSGARTEN site as well as temperature and salinity data from CTD casts, plankton net samples and sediment samples from the multicorer  (MUC) during the 2015 cruise will be shared between scientists from both institutions as part of scientific collaborations by mutual agreement.

Rationale

Sea-floor and water column observations

Evidences already show the impact of water temperature increase in the modification of the gas hydrate stability zone (GHSZ), potentially releasing methane in the pore water and ultimately in the water column (Westbrook et al., 2009; Ferre et al., 2012). This highlights not only the importance of monitoring temperature changes and methane concentration, but also other parameters in order to understand the interaction between oceanographic changes and methane fluxes. Depending on the release rate, at least N50% of the methane that dissolves into the sediment pore water could be retained inside the seafloor by microbial anaerobic oxidation of methane (Treude et al., 2003; Knittel and Boetius, 2009). This process may essentially influence the benthic organisms living at and within the surface sediments of the sea floor. One way to reconstruct past marine methane emissions is by carbon isotope (613() analysis of benthic foraminifera (e.g. Kennett et al., 2000).

Negative carbon-isotopic compositions of foraminifera tests have been reported from methane seep environments, and it has been suggested that some of these species record distinct 13C-depletions inherited from  methane (Sen Gupta et al., 1997; Rathburn et al., 2000; Hill et al., 2004; Panieri et al., 2009, 2014).

Thus, benthic foraminifers in methane seep environments likely preserve geochemical information from which past methane events may be reconstructed. Planktic foraminifera Methane rising through sediments as free gas could bypass the benthic methane filter (Knittel and Boetius, 2009) and, depending on the water depth, reach the atmosphere (McGinnis et al., 2006). In the water column, aerobic oxidation of methane converts methane with oxygen into C021 which can impact the pH of water masses. Prediction of pH decrease due to the anthropogenic C02-uptake is about 0.3-0.5 units until the end of this century (Caldeira and Wickett, 2005), and methane-induced acidification could nearly double this decrease (Biastoch et al., 2011).

Planktic foraminifera live in the upper 200m of the water column and their shells record various oceanographic conditions and sea surface properties such as the extent on sea-ice cover and changes in position of the oceanic fronts (e.g. Pflaumann et al., 2003; Rasmussen et al., 2007). More important, their shells may provide information on changes of ocean carbon chemistry due to shifts in both  atmospheric and methane-induced C02•  Planktic and benthic foraminifera shells obtained from plankton net samples, sediment trap, and sediment surface samples from 2012 and 2013 will supplement sampling campaign planned for summer 2015. The ocean acidification project (“Effects of ocean chemistry changes on planktic foraminifera in the Fram Strait: Ocean Acidification from natural to anthropogenic changes”) by Tine Rasmussen is already in progress with cooperation with AWi (project partner from AWi: Dr. Eduardsauerfetnd) regarding sediment traps. The collaboration between the two institutes will be strengthened through this proposal.