Consequences of UV‐enhanced community respiration for plankton metabolic balance

Abstract

The net community production (NCP) of plankton communities affects their role as sources or sinks of atmospheric CO 2 . Most estimates of NCP have been made by enclosing communities in bottles, generally glass borosilicate, that remove ultraviolet (UV)B and part of UVA wavelengths. A series of experiments were conducted to test whether NCP values from communities incubated excluding UVB (+ part of UVA) radiation (i.e., in glass borosilicate) differ from those of communities receiving the full solar radiation spectrum (i.e., incubated with quartz bottles) and to explore the effect of UV radiation on the respiration rates and bacterial production in these communities. Plankton NCP tended to be 43% lower, on average, when the rates were measured under full solar radiation than when UVB (+ part of UVA) was removed. Dark respiration was significantly enhanced after exposure to the full solar spectrum for most communities, showing lower values when previously incubated in a light environment free of UVB (250%) or in the dark (262%). Bacterial production was inhibited by natural sunlight but increased, as observed for community respiration, when transferred to the dark. Communities previously exposed to full solar spectrum showed the greatest increase in bacterial production when allowed to recover in the dark. The net result of these responses were an increase in community respiration and decline in net community production over 24 h, indicating that UVB radiation plays a major role in the metabolic balance of the ocean's surface ecosystem.

Nutrient availability limits biological production in Arctic sea ice melt ponds

“…In our study, primary production determined in bottle incubations may have been stimulated relative to in situ rates due to the exclusion of UV radiation in the incubation bottles (e.g. Worrest et al 1980;Agustí et al 2014). Although further studies are needed to evaluate the combined impact of UV radiation and the stimulating effect of nutrient enrichment, the increase in Chl a in ponds and enclosures over time in our study clearly demonstrated that despite potential UV radiation biological production was indeed limited by nutrients.…”

“…Wängberg et al 2008) and ciliate biomass (Marangoni et al 2006;Summerer et al 2009). If the bacteria and grazers are more strongly inhibited by UV radiation than are primary producers, UV radiation may thus have a stimulating effect on net productivity in the melt ponds (Agustí et al 2014;Garcia-Corral et al 2014). In our study, primary production determined in bottle incubations may have been stimulated relative to in situ rates due to the exclusion of UV radiation in the incubation bottles (e.g.…”

Comparing marine primary production estimates through different methods and development of conversion equations

“…For instance, modifications of the light field (Kirk, 1994) are observed as the incubations have been conducted with borosilicate bottles, a material that excludes UVB radiation. Indeed, recent analyses comparing estimates derived using quartz and glass bottles have shown that estimates of net community production are affected by the removal of the ambient UVB radiation when glass or plastic materials that filter out UV-B radiation are used, as has been the case for most analyses (Godoy et al, 2012;Agustí et al, 2014;Regaudie-de-Gioux et al, 2014). Furthermore, it is rare for in vitro incubations to be carried out at the correct corresponding environmental temperature.…”

Plankton Respiration, Production, and Trophic State in Tropical Coastal and Shelf Waters Adjacent to Northern Australia

“…Also, if incubation techniques are employed the light climate in experimental containers needs to reflect that in the field, which can be challenging. For example, it has recently been demonstrated that borosilicate flasks widely used for experimental incubations filter out UV light resulting in overestimation of production (Agustí et al, 2014). Moreover, the use of incubators allowing the passage of UV light may also mistakenly include the UV photo-oxidation (oxygen sink) in their plankton productivity term, which can lead to an underestimation of NCP (Kitidis et al, 2014;Gieskes et al, 2015).…”