Cebrian Just

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Cebrian
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Just
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  • Preprint
    Light dependence of Zostera marina annual growth dynamics in estuaries subject to different degrees of eutrophication
    ( 2005-05-20) Hauxwell, Jennifer ; Cebrian, Just ; Valiela, Ivan
    In temperate, shallow systems with clear waters the temporal dynamic of eelgrass (Zostera marina) growth is closely associated with the seasonality of irradiance at the water's surface. It has been recently suggested that increasing eutrophication, via light attenuation by increased algal growth, may disrupt the close temporal association between eelgrass growth and surface irradiance often found in pristine sites. Here, we test this hypothesis by examining the coupling between eelgrass growth dynamics and surface irradiance over an annual cycle in four shallow estuaries of the Waquoit Bay system (Massachusetts, USA) that have similar physical characteristics, but are subject to different land-derived nitrogen loading rates and the intensity of eutrophication sustained. Contrary to our hypothesis, the results show that, in general, most measures of eelgrass demographics were positively correlated with surface irradiance in all four estuaries. Out of the 45 regression models adjusted between irradiance and demographic variables (density, plastochrone intervals, and above- or below-ground biomass, growth, and production, on both a per shoot and areal basis), only 9 of them were non-significant, and only 6 of those corresponded to the eutrophic estuaries. Most notably, we found a lack of correlation between shoot density and irradiance in the eutrophic estuaries, in contrast to the strong coupling exhibited in estuaries receiving the lowest nitrogen loads. Experimental evidence from previous work has demonstrated severe light limitation and other deleterious impacts imposed by macroalgal canopies on newly recruiting shoots in the eutrophic estuaries, likely contributing to the lack of correlation between shoot density and irradiance at the water's surface. Because the range in eutrophication encompassed by this comparison includes the range of conditions at which eelgrass can survive, the relatively consistent temporal coupling between surface irradiance and most eelgrass demographic variables found here may also be a feature of other shallow temperate systems undergoing increasing eutrophication, and indicates a measure of plant recruitment (density) to be one of the first parameters to become uncoupled from light reaching the water's surface.
  • Dataset
    Use of a diatom inhibitor reveals contribution to seagrass ecosystem in experiments conducted using seagrass cores from 1m depth in Grand Bay in 2017.
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-08-11) Krause, Jeffrey W ; Cebrian, Just
    We report an assessment for determining the contribution by diatoms to community productivity and respiration within a coastal benthic ecosystem with multiple autotrophs. During summer, cores of open sediment and seagrass habitat were collected from a lagoon within the Northern Gulf of Mexico. Cores were maintained in an outdoor mesocosm. Germanic acid, an inhibitor of diatom cell division, was added to half the cores and quantification of production and respiration was done. Inhibition of diatoms reduced benthic productivity within the seagrass habitat. 71 to 83% of production was attributable to diatoms and this contribution moved the benthic system into net autotrophy. Diatom contribution to production in other habitat-community components was more variable (varied from 0 to 86%). Findings underscore the ecological importance of diatoms as producers in seagrass beds, the role of seagrasses in maintaining productivity, and infer that diatoms may have similar contributions in other aquatic vegetated habitats. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/819932
  • Dataset
    Silica and nitrogen analyses from incubation experiments conducted using seagrass cores from 1m depth in Grand Bay in 2017.
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-08-11) Krause, Jeffrey W ; Cebrian, Just
    We report an assessment for determining the contribution by diatoms to community productivity and respiration within a coastal benthic ecosystem with multiple autotrophs. During summer, cores of open sediment and seagrass habitat were collected from a lagoon within the Northern Gulf of Mexico. Cores were maintained in an outdoor mesocosm. Germanic acid, an inhibitor of diatom cell division, was added to half the cores and quantification of production and respiration was done. Inhibition of diatoms reduced benthic productivity within the seagrass habitat. 71 to 83% of production was attributable to diatoms and this contribution moved the benthic system into net autotrophy. Diatom contribution to production in other habitat-community components was more variable (varied from 0 to 86%). Findings underscore the ecological importance of diatoms as producers in seagrass beds, the role of seagrasses in maintaining productivity, and infer that diatoms may have similar contributions in other aquatic vegetated habitats. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/819975