Uncertainty and sensitivity in optode-based shelf-sea net community production estimates

Abstract

Abstract. Coastal seas represent one of the most valuable and vulnerable habitats on Earth. Understanding biological productivity in these dynamic regions is vital to understanding how they may influence and be affected by climate change. A key metric to this end is net community production (NCP), the net effect of autotrophy and heterotrophy; however accurate estimation of NCP has proved to be a difficult task. Presented here is a thorough exploration and sensitivity analysis of an oxygen mass-balance-based NCP estimation technique applied to the Warp Anchorage monitoring station, which is a permanently well-mixed shallow area within the River Thames plume. We have developed an opensource software package for calculating NCP estimates and air-sea gas flux. Our study site is identified as a region of net heterotrophy with strong seasonal variability. The annual cumulative net community oxygen production is calculated as (−5 ± 2.5) mol m −2 a −1 . Short-term daily variability in oxygen is demonstrated to make accurate individual daily estimates challenging. The effects of bubble-induced supersaturation is shown to have a large influence on cumulative annual estimates and is the source of much uncertainty.

Simultaneous assessment of oxygen- and nitrate-based net community production in a temperate shelf sea from a single ocean glider

“…Biological oxygen production can also be used as a proxy for net community production (J (O 2 )), with a net production of oxygen indicative of a net autotrophic system (Alkire et al, 2014;Hull et al, 2016). We implement an oxygen mass balance model to separate the physically and biologically driven components of the observed oxygen inventory changes.…”

“…B is the wind speed and temperature-dependent bubble supersaturation term from Liang et al (2013). This bubble term has a relatively large effect on net community production estimates when C s is close to C sat (Emerson and Bushinsky, 2016;Hull et al, 2016;Liang et al, 2017). Gas exchange is only relevant within the ventilated partition of the water column, which is equivalent to the actively mixed surface layer (known as mixing layer; Brainerd and Gregg, 1995) (z mix ).…”

“…It can be divided into two energetically distinct regimes: a seasonally stratifying northern part and a fully mixed southern and coastal part (Emeis et al, 2015). The shallower fully mixed region is believed to act as a net sink for CO 2 during the spring bloom periods and a source of CO 2 during the rest of the year (Emeis et al, 2015;Hull et al, 2016). Thomas et al (2005) suggest that the seasonally stratified regions are a sink for carbon throughout the year.…”

“…Key among those processes is marine production. Estimates of net community production (NCP) can quantify the uptake of CO 2 from the atmosphere into the sea (Alkire et al, 2012;Hull et al, 2016;Plant et al, 2016). Changes to community production can affect how organic material is exported to and respired within the non-ventilated waters below the thermocline (Große et al, 2016).…”

A Review of the Tools Used for Marine Monitoring in the UK: Combining Historic and Contemporary Methods with Modeling and Socioeconomics to Fulfill Legislative Needs and Scientific Ambitions

“…These data are used within the OSPAR eutrophication assessment (Foden et al, 2011). In addition, these data have enabled better design of robust monitoring programmes (Heffernan et al, 2010), validation of models (Große et al, 2016;van der Molen et al, 2016) and satellite marine products (Neukermans et al, 2012), and for studying ecosystem behavior (Devlin et al, 2009;Blauw et al, 2012;Capuzzo et al, 2013Capuzzo et al, , 2015Johnson et al, 2013;Hull et al, 2016). Fixed-point moorings are also used for making measurements of the wave climate.…”