Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

Keller, David P.; Hood, Raleigh R.

doi:10.1016/j.ecolmodel.2010.12.014

Cited by 36 publications

(30 citation statements)

References 130 publications

(184 reference statements)

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“…Total mortality of phytoplankton populations was in balance with gross growth (Figure 7a), indicating fast turnover of the photoautotrophic production within the North Atlantic Ocean. These results emphasize the need for the incorporation of viral lysis into ecosystems models (Franks, 2001;Keller and Hood, 2011;Keller and Hood, 2013). Moreover, our results support hypothesis (H3) that viral lysis rates vary with latitude, and point at a striking reduction in the ratio of viral lysis rates to grazing rates of marine phytoplankton at higher latitudes (Figure 7b).…”

Section: Discussionsupporting

confidence: 78%

Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean

et al. 2015

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Viral lysis of phytoplankton constrains marine primary production, food web dynamics and biogeochemical cycles in the ocean. Yet, little is known about the biogeographical distribution of viral lysis rates across the global ocean. To address this, we investigated phytoplankton groupspecific viral lysis rates along a latitudinal gradient within the North Atlantic Ocean. The data show large-scale distribution patterns of different virus groups across the North Atlantic that are associated with the biogeographical distributions of their potential microbial hosts. Average virusmediated lysis rates of the picocyanobacteria Prochlorococcus and Synechococcus were lower than those of the picoeukaryotic and nanoeukaryotic phytoplankton (that is, 0.14 per day compared with 0.19 and 0.23 per day, respectively). Total phytoplankton mortality (virus plus grazer-mediated) was comparable to the gross growth rate, demonstrating high turnover rates of phytoplankton populations. Virus-induced mortality was an important loss process at low and mid latitudes, whereas phytoplankton mortality was dominated by microzooplankton grazing at higher latitudes (456°N). This shift from a viral-lysis-dominated to a grazing-dominated phytoplankton community was associated with a decrease in temperature and salinity, and the decrease in viral lysis rates was also associated with increased vertical mixing at higher latitudes. Ocean-climate models predict that surface warming will lead to an expansion of the stratified and oligotrophic regions of the world's oceans. Our findings suggest that these future shifts in the regional climate of the ocean surface layer are likely to increase the contribution of viral lysis to phytoplankton mortality in the higher-latitude waters of the North Atlantic, which may potentially reduce transfer of matter and energy up the food chain and thus affect the capacity of the northern North Atlantic to act as a long-term sink for CO 2 .

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Section: Discussionsupporting

confidence: 78%

Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean

et al. 2015

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“…A turbidostat-like numerical formulation was used to control nutrient and DOM inflow and all model runs were to steady-state. Dissolved organic matter cycling is treated in detail as described in Keller and Hood (2011) with modifications only to the equations describing photochemical processes and the uptake of DON by phytoplankton; the latter does not occur in these simulations because there is little information to parameterize this process in the three systems and the former are described below. The model processes that produce Ducklow (2000); Field et al (1998); Lalli and Parsons (1997).…”

Section: Model Descriptionmentioning

confidence: 99%

“…1) used in this study is a slightly modified version of an existing C-N model (Keller and Hood, 2011) that includes: (1) two size classes of phytoplankton (b20 μm and >20 μm) and zooplankton (b200 μm and >200 μm), (2) bacteria, (3) detritus, (4) viruses, (5) DIC, (6) ammonium, (7) nitrate, and (6) labile, semi-labile, and refractory DOC and DON. In this model plankton have fixed non-Redfield C:N ratios, while detritus and DOM stoichiometry is variable.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Bacteria consume DOM and are also responsible for the ectoenzyme hydrolysis of semi-labile DOM, which produces both labile and refractory material. The model equations are in the Appendix A and the parameters for the three idealized ecosystems that differ from Keller and Hood (2011) are listed in Tables 2 and 3. The structure of the planktonic community in each idealized ecosystem was based on a study by Gasol et al (1997) that examined the biomass distribution (in terms of carbon) of different marine planktonic communities. In this study Gasol et al (1997) found that in the open ocean the mean biomasses of bacteria, protozoans (heterotrophic protists), and zooplankton, relative to that of phytoplankton were 1.00 ± 0.09, 0.54 ± 0.09, and 0.51 ± 0.05, respectively.…”

Section: Model Descriptionmentioning

confidence: 99%

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Comparative simulations of dissolved organic matter cycling in idealized oceanic, coastal, and estuarine surface waters

Keller

Hood

2013

Journal of Marine Systems

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“…DOC release was fixed at 5 and 3% for nanophytoplankton and diatoms, respectively. Recently, PER in the upper Chesapeake Bay was assumed to be a constant 26% (Keller & Hood, 2011), a relatively high value that seems to be based on a misinterpretation of Anderson & Williams (1998).…”

Section: Per In Biogeochemical Modelsmentioning

confidence: 99%

Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean

Thornton

2014

European Journal of Phycology

353

311

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The partitioning of organic matter (OM) between dissolved and particulate phases is an important factor in determining the fate of organic carbon in the ocean. Dissolved organic matter (DOM) release by phytoplankton is a ubiquitous process, resulting in 2-50% of the carbon fixed by photosynthesis leaving the cell. This loss can be divided into two components: passive leakage by diffusion across the cell membrane and the active exudation of DOM into the surrounding environment. At present there is no method to distinguish whether DOM is released via leakage or exudation. Most explanations for exudation remain hypothetical; as while DOM release has been measured extensively, there has been relatively little work to determine why DOM is released. Further research is needed to determine the composition of the DOM released by phytoplankton and to link composition to phytoplankton physiological status and environmental conditions. For example, the causes and physiology of phytoplankton cell death are poorly understood, though cell death increases membrane permeability and presumably DOM release. Recent work has shown that phytoplankton interactions with bacteria are important in determining both the amount and composition of the DOM released. In response to increasing CO 2 in the atmosphere, climate change is creating increasingly stressful conditions for phytoplankton in the surface ocean, including relatively warm water, low pH, low nutrient supply and high light. As ocean physics and chemistry change, it is hypothesized that a greater proportion of primary production will be released directly by phytoplankton into the water as DOM. Changes in the partitioning of primary production between the dissolved and particulate phases will have bottom-up effects on ecosystem structure and function. There is a need for research to determine how these changes affect the fate of organic matter in the ocean, particularly the efficiency of the biological carbon pump.

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Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

Cited by 36 publications

References 130 publications

Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean

Latitudinal variation in virus-induced mortality of phytoplankton across the North Atlantic Ocean

Comparative simulations of dissolved organic matter cycling in idealized oceanic, coastal, and estuarine surface waters

Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean

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